Theses and Dissertations (Veterinary Tropical Diseases)

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Exposure of wild carnivores to rabies and Mokola viruses in provincial and private game reserves in Mpumalanga province
Letsholo, Samantha Laone (University of Pretoria, 2014-03)
Rabies, a disease caused by members of the genus Lyssavirus, family Rhabdoviridae is a significant veterinary and public health threat globally including South Africa. This fatal but preventable zoonotic disease causes encephalitis in all warm-blooded vertebrates including humans. At least 50 000 human fatalities and 5 million rabies exposures occur annually. However, in developing countries where both domestic (urban type) and wild (sylvatic type) rabies cycles are common and transmission occurs readily across species barriers, the disease has proven difficult to eradicate. In South Africa, the main maintenance host species include the domestic dog, Canis lupus familiaris, in Limpopo province, Mpumalanga, Eastern Cape and coastal KwaZulu/Natal provinces, and wildlife host species including the black-backed jackal, Canis mesomelas, the bat-eared fox, Otocyon megalotis, (both maintain the canid rabies biotype) and the yellow mongoose, Cynictis penicillata, that maintains the mongoose rabies biotype. There are currently 12 Lyssavirus species worldwide. In South Africa, Lagos bat virus and Duvenhage virus are rarely diagnosed in terrestrial animals and are generally associated with fruit-eating (Epomophorus wahlbergi) and insect-eating (Minopterus schreibersii) bats respectively. To date, Mokola virus (MOKV) and Ikoma virus (IKOV) are the only lyssaviruses that have not been recovered from bat species. Between 1928 and 2006, rabies was diagnosed in 4952 wildlife species in South Africa, the majority of which were mongoose species, especially Cynictis penicillata, followed by the bat eared fox, Otocyon megalotis, and the black-backed jackal, Canis mesomelas. Only one case of rabies was diagnosed in lions over the same period and no cases of Mokola virus infections have been documented in South African wildlife thus far. This project was undertaken to determine the prevalence of neutralising antibodies to RABV and MOKV, the latter a rabies-related virus, in serum samples originating from lions in private and provincial game reserves adjacent to the Mnisi communal area in Mpumalanga province and in the greater Kruger National Park. The expected benefits of the study include the evaluation of exposure of lions to RABV and MOKV in the above-mentioned region of South Africa, further improving the understanding of the epidemiology of the disease in a human/domestic animal/wildlife interface. Stored lion serum samples from the University of Pretoria, Department of Veterinary Tropical Diseases (n=140) and the Agricultural Research Council-Ondesterpoort Veterinary Institute (ARC-OVI), OIE Rabies Laboratory (n=20) and sera from other carnivores from the ARC-OVI (n=5) were tested for antibodies to classical rabies virus and Mokola virus using the fluorescent antibody virus neutralization test. All 165 sera were collected from private and provincial game reserves in Mpumalanga province between the years 1995 and 2012. The cut-off point for both RABV and MOKV serum samples was determined as 0.5 IU/ml and 0.95 IU/ml respectively. Any serum sample with a titre less than 0.5 IU/ml was regarded as negative, while any serum sample with a titre equal to or above 0.5 IU/ml was regarded as positive for RABV. Any serum sample with a titre less than an equivalent of log100.95 dilution was regarded as negative, while any serum sample with a titre equal to or above log100.95 dilution was regarded as positive for MOKV. Lion sera collected between 1995 and 2000 (n=140) had a 2.1% prevalence of RABV neutralizing antibodies and a 0.7% prevalence of MOKV antibodies. Sera collected from lions between 2010 and 2012 (n=20) had a 65.0% prevalence of RABV antibodies and a 26.3% prevalence of MOKV antibodies. Due to the uncertain vaccination status of samples collected between 2010 and 2012 and the significant differences in prevalence between the lion serum collected between 1995 and 2000 and between 2010 and 2012, the two groups of lions were treated as two separate populations. Other carnivores (n=5) had a prevalence of RABV neutralising antibodies of 40.0% and a prevalence of MOKV neutralising antibodies of 25.0%. When calculating the difference of proportions for the prevalences of the antibodies of the two lyssaviruses within each population, the prevalences were not significantly different. The results of the study suggest that lions in Kruger National Park have been exposed to RABV (2.1%) and or possibly another lyssavirus related to MOKV at low frequencies between 1995 and 2000. The sample sizes of the lions from other game reserves and other carnivores were too small to make a valid conclusion thus larger sample population sizes must be considered for future studies in these areas. Since the neutralising antibody prevalences in the Kruger National Park lions were not significantly different for both viruses, it can be concluded that if a lion presents with clinical signs of rabies, the disease is just as likely to be caused by RABV as MOKV.
Disposable diaper use and perception of health and environmental risks in a rural community from Bushbuckridge, South Africa
Lowe, Army L. (University of Pretoria, 2024-10)
Littering of disposable diapers is a problem with One Health implications and has been identified as an issue within the Mnisi community, a rural area within Bushbuckridge, South Africa. Several environmental and public health related concerns arise from this, including contamination of waterways used by animals and people with human waste, scavenging by domestic and wild animals, and the aesthetic impact on the environment. The aim of this study was to gain an understanding of the use and sanitation practices associated with disposable diapers, with the ultimate goal of identifying possible community-led initiatives and solutions which can be used for training and education. Focus group discussions were conducted within the community which included a participatory mapping exercise used to map general diaper disposal sites. Focus group data was analyzed according to three themes: decisions and factors around diaper use and disposal, perceptions of impact and health risk of diaper use for people and animals, and barriers and solutions for proper disposal. Most participants used disposable diapers and disposed of them within the environment because they lacked access to municipal waste collection. Regarding decisions around diaper use, common factors discussed were convenience, social perception and beliefs, cost, water access, and diaper disposal logistics. Convenience and societal perception and beliefs were determined as key factors behind diapering choices, and both a gender and a generational divide was revealed. Participants express general understanding of negative impacts associated with diaper disposal, but knowledge gaps exist, notably regarding water pollution and pathogen spread, that could be a focus of educational campaigns. Regarding solutions, participants proposed the provision of a central collection point as well a return to reusable diapers, each of which has its own considerations and hurdles. Any interventions should retain the perceived convenience factor of disposable diapers and be implemented on a community rather than individual basis. Solutions should be multifaceted, involve opportunities for community collaboration amongst all ages and genders, and should also engage local leadership. Focus groups should be considered as the first steps towards continued discussions amongst stakeholders.
Toxoplasma gondii infection in impala (Aepyceros melampus) from the Timbavati abattoir
Rabe, Shanzelle (University of Pretoria, 2024-10)
Toxoplasma gondii (T. gondii) is a protozoon parasite with a worldwide distribution that infects mainly domestic and wild felids, with virtually all mammal and avian species acting as intermediate hosts. Clinical manifestation known as toxoplasmosis causes encephalitis as well as infertility, abortion or the birth of offspring with central nervous system abnormalities. The feline definitive host ingests the parasite when consuming intermediate hosts with tissue cysts containing T. gondii bradyzoites. Considering the possible presence of the parasite in production and wildlife species, the consumption of undercooked game meat by people, should be regulated because of the potential risk of T. gondii transmission to humans. In this study the prevalence of infection and the tissue cyst predilection sites was determined through serological and molecular assays performed on impala antelope (Aepyceros melampus) samples collected from the Timbavati abattoir, located within the Timbavati Private Nature Reserve (TPNR), on the western boundary of the Kruger National Park (KNP). Impala samples (n = 138) were collected within the TPNR over six months. Serum was used in two serological assays, the Modified Agglutination Test (MAT) and the Latex Agglutination Test (LAT), for assessing the seroprevalence. An optimised in-house sodium acetate method was used to extract DNA from the triceps brachii, cardiac muscle, tongue, diaphragm, spleen, liver, and brain samples, followed by quantitative polymerase chain reaction (qPCR) to amplify an 81-bp fragment of the Repeat element 529-bp sequence to confirm the presence of T. gondii DNA. Due to the limited research on T. gondii in wildlife species in Africa, in terms of both clinical significance and the interface between humans and wildlife in the rural setting, the main focus of the current study was to determine whether the rural communities in and around the Mnisi area are at risk of contracting T. gondii by consuming game meat, and to determine if specific organs/tissues were more prone to containing T. gondii cysts than others. Based on a seroprevalence of 8.70% (MAT) and 13.77% (LAT) in impala in the Mnisi area, the risk of infection via environmental (faecal) contamination is quite low, but still noteworthy. In both assays the two strong positive impala individuals were F18 and F29. When comparing the results between MAT and LAT using the McNemar’s test and Kappa statistics, the LAT yielded a higher seroprevalence, alluding to the possibility of it being the less specific test of the two, however the MAT is more subjective in terms of interpretation of the results. When evaluating the presence of T. gondii DNA using qPCR, 7.25% of individual impala contained T. gondii DNA in at least one of the seven tissues that were sampled, and of these the only samples to have Ct values consistently below 35 were F18 (brain) and F29 (tongue). The presence of DNA within specific tissues (tongue, heart, brain, triceps brachii, and diaphragm) correlates directly with the risk of infection via ingestion of tissue cysts. Undercooked game meat is often sold to nature reserves as biltong or carpaccio, but is most often consumed locally by the population around Timbavati. A lack of resources in the rural community often leads to ingestion of raw or undercooked game meat, and therefore poses a significant risk of contracting toxoplasmosis. Since treatment of T. gondii using drugs such as sulphadiazine, pyrimethamine, clindamycin, or toltrazuril is challenging in people, a better understanding of the prevalence of this parasite within the wildlife population can lead to advances in prevention of disease in and around the Mnisi community. Furthermore, investigating the different strains of T. gondii circulating in wildlife species might shed some light on its genetic diversity within the South African population, and will also help to assess the clinical importance of this disease.
A comparison of perceptions of the tuberculin skin test and an incentive postmortem-based surveillance system in the Mnisi community, Mpumalanga, South Africa
Marange, Rudo (University of Pretoria, 2018-10)
Tuberculosis (TB) is a global health concern. Mycobacterium bovis (M. bovis) and Mycobacterium tuberculosis (M. tuberculosis) are the most common causes of TB in animals and humans respectively. As part of TB control strategies most governments have instituted test and slaughter policies to eradicate bovine TB (bTB). While this has been met with some success, innovative and effective strategies to control TB are needed. We evaluated the postmortem surveillance (PMS) system as an alternative to the tuberculin skin test (TST) and found it to be a potentially cheaper and effective surveillance method. The level of TB awareness in the Mnisi community was also evaluated. Tuberculosis awareness by the community is also an effective way of TB control as education empowers people to make informed choices with regards to mitigating TB risk factors in their daily lives.
Vaccination of on-farm cattle against heartwater : safety and efficacy of Ehrlichia ruminantium (Welgevonden) vaccine
Marumo, Ratselane Daniel (University of Pretoria, 2018)
Ehrlichia ruminantium (Rickettsiales, Rickettsiaceae) is the causative agent of heartwater disease transmitted to cattle, sheep, goats and wild ruminants e.g. springbok by Amblyomma hebraeum in South Africa (SA). The current live blood vaccine (Ball 3) used in SA has limitations; it does not show efficacy against most field strains, it is virulent and concurrent treatment with antibiotic is necessary and it is produced in life animals which hinders its quality control. Second generation vaccines have not yet been developed to commercial stages. Previous experiments using an attenuated E. ruminantium (Welgevonden) tissue culture experimental vaccine in Merino sheep, Boer goats and Angora goats, administered through intramuscular (I/M) and intravenous (I/V) routes, without the use of antibiotic, showed promising results in terms of safety and efficacy. The objective of the current study was to test the safety and efficacy of this attenuated tissue culture vaccine in cattle, administered by the I/M route. One sheep injected with 10 ml of the virulent Welgevonden heartwater strain was used to infect Amblyomma hebraeum nymphs. Twenty (8-24 months old) male Friesian Holstein cattle obtained from a heartwater and vector free area were used; ten were vaccinated with the attenuated Welgevonden tissue culture isolate intramuscularly and ten were untreated controls. The vaccine was prepared and inoculated with an estimated concentration of 1.11 X 10⁶ E. ruminantium organisms in 2 ml. Tick challenge of both cattle groups was performed with 17 infected A. hebraeum (7 males/10 females) 35 days following vaccination. Cattle were screened serologically by the indirect fluorescent antibody test (IFAT) and by molecular tools using pCS20 quantitative real-time TaqMan (qPCR) before and after vaccination and challenge. Cattle were weighed before vaccination, during vaccination reactions and tick challenge (Days 0-77). Animals were monitored for clinical signs of heartwater disease and treated according to a score sheet when appropriate. Samples of ticks that dropped from infected sheep on different days were highly infected (103) with E. ruminantium (Welgevonden) organisms as tested using qPCR and deemed suitable for animal challenge. The group of cattle (n=10) which were vaccinated intramuscularly, showed no clinical or local vaccine related reactions and no treatment was required. The vaccinated group was challenged 35 days post vaccination together with the untreated controls (n=10). The mean number of engorged female ticks that dropped from the vaccinated (n=7.7) and unvaccinated (n=8.3) groups showed no statistical difference. The vaccinated group did not show any clinical reactions, while 8/10 of the unvaccinated controls developed severe reactions and received treatment while one animal was euthanized following the score sheet. There was a statistical significant mean difference (p-value = 0.0003) in the final weight gain/loss between the vaccinated (mean 5.6 + 2.84 Kg) and unvaccinated (mean -0.33 + 2.78 Kg) groups. On Day 37 after tick challenge, 100% of the vaccinated and 80% of the unvaccinated cattle showed sero-conversion (1/180) in the IFAT. The results of the study have demonstrated the safety and efficacy of the attenuated E. ruminantium (Welgevonden) experimental vaccine against homologous challenge in cattle as judged by the severe clinical reactions in the unvaccinated group. The vaccinated group also had a gain in mean body weight compared to the unvaccinated group after challenge.
Identification of African swine fever virus proteins that activate T-cell immune responses
Mabetlela, Freddy Mokadi (University of Pretoria, 2018-09)
African swine fever (ASF) is a highly contagious haemorrhagic disease of domestic pigs, which affects wild boar as well and for which there is currently no commercial vaccine. African swine fever virus (ASFV), the causal agent of ASF infects warthogs (Phacochoerus africanus), bush pigs (Potamochoerus porcus), giant forest hogs and members of the soft tick genus (Ornithodoros moubata complex) without causing disease. Virulent isolates of this virus causes mortality in domestic pigs within seven to ten days post infection, leading to negative economic consequences. Vaccination attempts using different strategies only protect against homologous strains with inadequate protection against heterologous strains of ASFV. The immunological characterisation of ASFV proteins could assist in the development of an effective vaccine against ASF. The aim of this study was therefore to immunologically characterise a selected range of ASFV proteins (p22, CD2V, pp220 fragments (F)1-F4, pS273R, pA104R, pE165R, pF334L, pK205R and pL11L) by identifing the cytokines they induce in peripheral blood mononuclear cells (PBMC) from a pig that was infected with ASFV via tick feeding (pig 1) and an incontact ASFV infected pig (pig 2). The benefits of identifying immunilogical characteristics of the cytokines can lead to possible vaccine development and decrease of animal losses due to ASF. Several proteins (p22, pp220 F1-4, pS273R, pA104R, pE165R and pK205R) from the genotype II ASFV isolate MAL/11/02 were successfully expressed using a pET102/D-Topo isomerase enzyme (TOPO)® bacterial expression system. Plasmids with gene inserts were amplified using the Invitrogen E. coli TOP10 cloning cells and proteins were expressed in BL21 DE3 cells using isopropyl β-D-1-thiogalactopyranoside (IPTG) induction. The protein product of genes EP402R (CD2V), pF334L and pL11L did not express and were excluded from futher experiments. The expressed proteins were purified by affinity chromatography using Nickel columns with affinity to the His-tag on the recombinant proteins. The immunological assays, interferon gamma (IFN)-γ enzyme-linked immunospot (ELISpot) and cytokine [Interleukin (IL)-2, IL-4, IL-8, IL 10, IL-12, IFN-γ and IFN-alpha (α)] reverse transcription (RT) quantitative real time polymerase chain reaction (RT-qPCR), were conducted using PBMCs. PBMC was collected from pig 1 after ten days post infection (pi) with the genotype XIX ASFV isolate RSA/12/15 strain of ASFV and pig 2 ten days after co-habitation with pig 1. Only four of the nine recombinant ASFV proteins produced significant cytokine levels. The recombinant p22 protein up-regulated cytokines IL-2, IL-4, IL-8, IL-10 and IFN-γ in pig 1 and IFN-α in pig 2. Fragment four (F4) of polyprotein (pp) 220 up-regulated IL-4, IL-8, IL-12 and IFN-α in pig 1 and IFN-α in pig 2. Recombinant proteins pA104R up-regulated IFN-α in pig 1 and pS273R significantly down-regulated IFN-α in pig 1. In conclusion, the study revealed that ASFV recombinant proteins p22 and pp220-F4 induced all the study cytokines which are important in antiviral immunity. This data can be applied in future ASFV vaccinology studies.
Seroprevalence and associated risk factors of West Nile virus in selected equine populations in South Africa
Jeal, Rebecca Eileen (University of Pretoria, 2018-06)
The family Flaviviridae consists of 94 species, which are distributed worldwide. Viruses in this family share aetiological properties such as membrane envelope proteins, resulting in diagnostic cross-‐reactivity. Flaviviruses are divided into two clades; arthropod-‐borne and non-‐arthropod borne viruses. The most predominant flavivirus seen in horses is West Nile virus (WNV), belonging to the arthropod-‐borne clade. West Nile virus has been divided into two lineages, of which, the second lineage is primarily found in South Africa. West Nile virus is transmitted through vector species, of which mosquito species are most predominant. Two genera of mosquitoes in particular, Aedes and Culex are widely distributed and are fundamental in the transmission of the virus to both reservoir hosts and incidental hosts. Other vectors included in the transmission he family Flaviviridae consists of 94 species, which are distributed worldwide. Viruses in this family share aetiological properties such as membrane envelope proteins, resulting in diagnostic cross-‐reactivity. Flaviviruses are divided into two clades; arthropod-‐borne and non-‐arthropod borne viruses. The most predominant flavivirus seen in horses is West Nile virus (WNV), belonging to the arthropod-‐borne clade. West Nile virus has been divided into two lineages, of which, the second lineage is primarily found in South Africa. West Nile virus is transmitted through vector species, of which mosquito species are most predominant. Two genera of mosquitoes in particular, Aedes and Culex are widely distributed and are fundamental in the transmission of the virus to both reservoir hosts and incidental hosts. Other vectors included in the transmission Blood samples were initially tested using the serum neutralization test (SNT). Documented positive and negative samples were then subjected to a capture IgG sandwich enzyme-‐linked immunosorbant assay (ELISA). The results of the two assays were compared with one another, proving to correlate efficiently, giving the resultant seroprevalence percentages for each province, and then were used in comparison with the outcome of the questionnaires to determine significant associated risk factors. Results were analyzed with both univariable and multivariable analyses, taking clustering into consideration, to determine both apparent and prevalence estimate for each province and significance of seropositivity with associated risk factors. A small population of mosquitoes was collected in both Gauteng and Mpumalanga Provinces and were identified and separated into species. A nested SYBR green real-‐time PCR assay was conducted on the pooled species of mosquitoes. All species presented negative for the presence of WNV, which could be a result of a low number of mosquitoes or a low prevalence of WNV in each species. The species identified included: Culex spp., Aedes spp. and Anopheles spp. The SNT were used to determine the apparent seroprevalence of WNV in the collected serum samples, thereafter, the prevalence estimate was calculated with a 95% confidence interval, taking clustering into consideration, for each province. The Free State Province had a high seroprevalence of 73% (95% CI 64-‐81%), the Western Cape Province had a seroprevalence of 65% (95% CI 51-‐79%) and Gauteng Province had a seroprevalence of 61% (95% CI 61-‐62%). Limpopo Province had a seroprevalence of 60% (95% CI 45-‐74%), followed by Northern Cape Province with 57% (95% CI 48-‐66%), KwaZulu-‐Natal Province with 54% (95% CI 43-‐65%) and Mpumalanga Province with 56% (95% CI 40-‐73%). The North West and Eastern Cape Provinces had lower seroprevalences of 43% (95% CI 34-‐52%) and 48% (95% CI 43-‐54%) respectively. Overall, the apparent seroprevalence for South Africa was 59% (95% CI 54-‐64) using the SNT. The ELISA assays showed similar results to the SNT, with a 61% (95% CI 44-‐79%) seroprevalence of WNV for South Africa. Gauteng Province had a seroprevalence of 47% (95% CI 44-‐79%), KwaZulu-‐Natal Province had a seroprevalence of 24% (95% CI 44-‐79%), Northern Cape Province had 78% (95% CI 44-‐79%) seroposivitiy, Eastern Cape Province had a seroprevalence of 68% (95% CI 44-‐79%), North West Province with 59% (95% CI 44-‐79%) and Mpumalanga Province had a seropositivity of 79% (95% CI 44-‐79%). The results obtained using the ELISA had a moderate agreement with the SNT results (Kappa = 0.5).The univariable analysis showed association of WNV seropositive horses with; various agricultural activities, contact with different animal species, presence of annual frost, assorted water sources, occurrence of standing water pools and presence of Culicoides midges. These variables were subjected to multivariab analysis. The variables that indicated a p-‐value of less than 0.05 were considered significant. Among these values were agricultural activities, such as livestock in the Free State Province, forestry in Mpumalanga Province and vineyards in the Western Cape Province. Contact with small ruminants and other species were the only significant species associated with WNV seropositive horses. Both standing pools of water and river sources were associated with seroprevalence in different provinces. Lastly, annual frost was only associated with seroprevalence in the Limpopo Province. Of the medical history and symptoms, fever was the singular variable associated with seropositivity. It is evident that many positive cases of infected horses are either not being reported or are not presenting with substantial clinical signs. The horses included in this study were from various age groups, different sexes and breeds and participated in various disciplines. Racehorses were excluded from the study due to their movement throughout the country making them bad sentinels for the study. The high seroprevalence of WNV in horse populations, determined in this study, indicates a subsequent high exposure rate throughout South Africa, varying amongst provinces. The risk factors associated with seroprevalence were all area specific, indicating the importance of habitats and the role it plays in transmission due to the presence of potential vectors. This study also noted a lack of knowledge about the transmission and prevalence of WNV amongst horse owners in South Africa.
Vectorial competence of Glossina brevipalpis in the transmission of Trypanosoma congolense in the Matutuíne District, Maputo Province, Mozambique
Cossa, Nióbio Vasco (University of Pretoria, 2024-11)
African Animal Trypanosomoses (AAT) are a group of parasitic diseases that are considered a major constraint to animal health and production in Africa, where they are associated with vast economic losses. AAT is caused by protozoa parasites of the genus Trypanosoma. In Mozambique, T. congolense is the predominant trypanosome species in regions affected by AAT. The epidemiology of AAT is largely determined by the distribution and vectorial competence of its cyclic vector, the tsetse fly. In southern Mozambique, there is a high prevalence of AAT in the Matutíne District, where the tsetse fly species Glossina brevipalpis is abundant. Based on existing studies, there is currently a lack of clarity on the vectorial competence of Glossina brevipalpis in the transmission of T. congolense. Therefore, this study aimed to assess the competence of G. brevipalpis as a vector of T. congolense using wild flies captured in Matutuíne District, Mozambique. In an initial experiment, 234 G. brevipalpis flies were captured in the Maputo National Park, and their survival under experimental conditions was evaluated. These flies were transferred to entomological cages, fed every 48 hours on one bovine and kept in a room for 30 days at the Tintigala Research Station, where temperature and relative humidity (Rh) were regularly monitored. The vectorial competence and possible mechanical transmission of T. congolense to susceptible cattle were then evaluated. For this experiment, 915 G. brevipalpis flies (41 females and 874 males) were fed six times in two cattle that had previously been infected with T. congolense (isolated from Matutuíne - TCM2018), followed by two meals in a clean animal to mechanically remove the remnant trypanosomes from previous blood meals. Lastly, they were fed for 30 days on four cattle that were susceptible to infection. These five susceptible animals were monitored for the development of parasitaemia for 60 days based on body temperature, PCV, buffy coat and PCR. In the meantime, flies were dissected weekly to observe the development of trypanosomes in the midgut and proboscis. Regarding the evaluation of mechanical transmission by G. brevipalpis, 97 teneral flies from a colony were fed once on two infected cattle (three days after emergence) and once on a susceptible bovine (48 hours after the first meal). Under experimental conditions, a survival rate of 77% was recorded within a period of 30 days among captured G. brevipalpis flies. Weekly dissection of flies that fed on infected animals revealed that 89% were positive for T. congolense, based on microscopy and 100% based on PCR (midgut and proboscis). The four susceptible cattle tested positive for T. congolense infection. However, no trypanosome infection was observed in the cattle used for cleaning the proboscis and evaluation of mechanical transmission. The current results indicate that G. brevipalpis is a competent vector for the transmission of T. congolense. Additionally, these results demonstrate the inability of G. brevipalpis to mechanically transmit T. congolense after 48 hours of an infected blood meal.
Retrospective study of human Brucellosis trends Between 2014-2023 and consideration of One Health perspectives of healthcare professionals in Isiolo County, Kenya
Wako, Buke Yussuf (University of Pretoria, 2025)
Brucellosis, a zoonotic disease, remains a significant public health concern in Kenya. It also has a substantial socio-economic impact, particularly in pastoralist communities such as Isiolo County, here human-animal interactions are common. This study aims to estimate the trends of human brucellosis in Isiolo County over the past decade (2014–2023) through retrospective hospital data, focusing on spatial and temporal patterns and proportional morbidity as well as key informant’s interviews (KII) evaluating barriers to diagnosis, control and effectiveness of current interventions of brucellosis across three study sites (Isiolo, Garbatulla and Merti hospitals). Retrospective data from the 3 hospitals were analyzed, including 10,302 individual test results across the study period, categorized by gender, age, and test outcomes. The retrospective analysis revealed gender disparities, with females representing 65% of tested patients and 61% of positive cases, likely reflecting higher healthcare-seeking behavior among women. Brucellosis was prevalent across all age groups, with individuals aged 19–35 years showing the highest positivity, likely due to occupational exposure to livestock. Variations in hospital-specific prevalence were noted, with Merti hospital consistently reporting higher positivity rates (19%) compared to Garbatulla (16%) and Isiolo (19.7%), which may be linked to higher testing volumes and improved public awareness campaigns. Yearly trends showed fluctuations, with peaks during the COVID-19 pandemic and research-driven testing efforts (2021). KIIs identified knowledge gaps regarding transmission, prevention, diagnostic challenges, including reagent shortages and reliance on less sensitive tests and cultural beliefs and myths hindering timely care-seeking. The study highlights the need for targeted interventions, including increased disease surveillance, public awareness, and improved diagnostic capacity. It emphasizes the significance of site- specific strategies and a One Health approach in addressing zoonotic diseases especially in resource-constrained settings. Further research is needed to assess the effectiveness of current control measures and address data gaps.
Comparison of culture and real-time PCR for anthrax detection
Bowa, Benson (University of Pretoria, 2024-11)
Anthrax, a serious zoonotic disease caused by the bacterium, Bacillus anthracis, is a threat to the livelihood of many people living in Africa. In Zambia, anthrax is endemic in the Western and Eastern provinces and control is mainly focused on limiting environmental contamination and human exposure as much as possible through vaccination of animals and rapid response to animal disease outbreaks. Anthrax outbreak response is largely dependent on laboratory confirmation of the disease which is a part of the surveillance system for the country. The definitive method for confirmation of B. anthracis used in Zambia is culture, which contributes significantly to delayed response since it is lengthy and needs adequate logistical and technical support. This study aimed to compare culture and the non-culture methods from different host and sample types, semi-quantitative / real-time PCR (qPCR), using samples from different provinces in Zambia. A total number of 91 samples and 18 B. anthracis strains were used in the study. The samples were cultured using the standard microbiological method of identifying the causative bacterium and the obtained isolates and B. anthracis strains were confirmed by qPCR using a chromosomal marker Ba-1, lethal factor gene, lef on pXO1 and capsule B gene on pXO2, capB using TaqMan qPCR assay as well as chromosomal marker on small acid soluble proteins (sasp) using ANT probe, protective antigen gene, pagA using the probe BAPA on pXO1 and capsule C gene, capC on pXO2 using SYBR green qPCR assay. DNA was extracted from the samples and tested using TaqMan and SYBR green qPCR assays. Eighteen B. anthracis strains isolated were confirmed on SYBR green qPCR assay. With culture, the 91 samples yielded 41 (10.9%) B. anthracis isolates that were confirmed on SYBR green qPCR assay. The TaqMan qPCR assay detected 82.4% (75/91) of samples as B. anthracis using Ba-1 positive with lef and/or capB gene markers criteria. The SYBR green assay detected 63.7% (58/91) positive B. anthracis specimen using the criteria of positivity on BAPA and/or capC and ANT gene markers. Skin samples and buffalo host samples yielded the highest positive B. anthracis results with the Western Province with the highest anthrax incidence. The study demonstrated that culture infrequently detects anthrax positives from specimen and that qPCR is a more accurate method to use with TaqMan being more sensitive than SYBR green assay. Further, the study uncovered that isolate DNA was more reliable to use than specimen DNA for detection of B. anthracis using qPCR with specific samples type and species yielding better results.
Characterisation and control of foot-and-mouth disease outbreaks in Zambia between 2015 and 2020
Banda, Frank (University of Pretoria, 2024-10)
Repeated outbreaks of transboundary animal diseases, particularly foot-and-mouth disease (FMD), have posed significant challenges to the development of the livestock industry in Zambia and the broader Southern African region. This sector is crucial to national food security and livelihoods and holds potential for greater economic contribution due to Zambia’s favourable natural resources. This study explores the molecular epidemiology of the FMD virus (FMDV) in Zambia, focusing on the emergence and spread of serotypes O/EA-2, A, SAT-2, and SAT-3. A scoping review of diagnostic assays for SAT serotypes recommended the combined use of SAT-1, SAT-2, and SAT-3 lateral flow devices (LFDs) for effective viral detection, with the PrioCheck®-NSP kit proving highly effective for non-structural protein antibody identification. The immunogenicity of the O-Manisa vaccine was assessed in cattle challenged with the O/EA-2 outbreak strain, revealing significantly higher antibody titres in double-dosed animals at 56 days post-vaccination (dpv) compared to single-dosed groups. Furthermore, a strong positive correlation was observed between virus neutralisation tests and solid-phase competitive ELISA (SPCE), supporting the use of SPCE in immunogenicity assessments, particularly in resource-constrained settings. The findings underscore the complexity of FMD epidemiology in Zambia and highlight the urgent need for continuous monitoring of serotype O/EA-2 and a coordinated regional strategy for FMD control across Southern Africa.
Antimicrobial sensitivity of Escherichia coli and Enterococcus species isolated from table eggs, and backyard poultry farmers’ knowledge and attitudes on responsible antimicrobial use in Balfour, Dipaleseng Municipality of Mpumalanga Province, South Africa
Mbedzi, Sherpherd (University of Pretoria, 2025-07)
The emergence and subsequent spread of antimicrobial resistance (AMR) in pathogenic microorganisms is an increasing and well documented global health concern (Eagar et al., 2012; Roth et al., 2019). Widespread antimicrobial drug usage in livestock is implicated as one of the drivers of AMR (Kapena et al., 2020). Significant knowledge gaps exist about the efficacy of these drugs. It is crucial to carry out surveillance research in accordance with the global action plan of the World Health Organization (WHO) to combat AMR (Nulsen et al., 2008; Kapena et al., 2020). This research was conducted to determine the antibiotic sensitivity of Escherichia coli (E. coli) and Enterococcus isolates from chicken table eggs, as well as respondents’ knowledge of antibiotics, withdrawal times and AMR in the Balfour community of Mpumalanga province. A structured questionnaire was administered in face-to-face interview format to backyard poultry farmers (n=27). Out of 27 respondents, 48.1% (13/27) indicated having an idea of what antibiotics are, while 29.6% (8/27) had an idea about withdrawal times. Only 14.8% (4/27) of respondents heard about AMR, with 51.9% (14/27) of respondents indicating they consumed eggs laid during treatment and 22.2% (6/27) would slaughter chickens for meat during treatment. Standard bacteriological methods were used to isolate E. coli and Enterococci from eggshells and egg contents. Ten E. coli isolates were recovered; 90% (9/10) from eggshells and 10% (1/10) from egg contents. A total of 58 Enterococcus isolates were recovered from eggshell swabs, and none from egg contents. Antibiotic sensitivity of the recovered bacteria was determined using the Kirby-Bauer disk diffusion method. Of the 10 E. coli isolates, susceptibility to ampicillin was noted to be 40%, (4/10). Susceptibility to colistin, gentamicin and sulpha-trimethoprim was 100% (10/10). Doxycycline was 40% (4/10). Susceptibility to enrofloxacin, fosfomycin and kanamycin was similar, with 80% (8/10) of isolates showing susceptibility. There were 90% (9/10) isolates susceptible to sulphonamide compound. Susceptibility to tetracycline was 60% (6/10). All (100%) of the Enterococcus isolates recovered, were susceptible to ampicillin. Susceptibility to doxycycline was noted in 86.2% (50/58) of isolates, with only 6.9% (4/58) susceptible to enrofloxacin. Against erythromycin, 32.8% (19/58) of isolates were susceptible. None of the Enterococci showed susceptibility to kanamycin, with 86.2% (50/58) demonstrating resistance and 13.8% (8/58) showing intermediate susceptibility. There was 100% resistance to sulphonamides. Susceptibility to sulpha-trimethoprim and vancomycin was quite high at 98.3% (57/58) and 94.8% (55/58), respectively. Susceptibility to tetracycline was 48.3%. All Enterococcus isolates demonstrated resistance to at least a single antibiotic, with 72.4% exhibiting MDR (resistance to 3 or more antibiotics) (Magiorakos et al., 2012). The outcomes of the research show that there is very little awareness about antibiotics, withdrawal periods, and AMR among the surveyed community members. These outcomes emphasize the necessity of educational initiatives and community outreach efforts to better inform the public on these issues of public health concern.
Establishment of in vitro persistent infection of the foot-and-mouth disease virus SAT 2 serotype and comparative viral genome analysis during acute and persistent infections
Nocaka, Linda (University of Pretoria, 2024-11)
Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen affecting global livestock production. This study aimed to establish persistent FMDV SAT 2 infection using ammonium chloride (NH4Cl) in vitro, a lysosomotropic agent that inhibits viral replication by increasing endosomal pH. Cytotoxicity assays determined NH4Cl’s effects on virus-free BHK-21 cells at concentrations of 10 mM, 15 mM, and 20 mM. Persistent infections were established by infecting BHK-21 cells at a multiplicity of infection (MOI = 0.001) and treating with NH4Cl, while acute infections were achieved without NH4Cl treatment. Acute infections exhibited extensive cytopathic effects (CPE), whereas persistent infections displayed delayed CPE. Real-time PCR confirmed reduced viral replication in NH4Cl-treated cultures, as indicated by higher Cq values (25–34) compared to acute infections (15–25). RNA sequencing revealed greater mutation accumulation in acute infections, with deletions and insertions predominantly occurring in non-structural protein (NSP) and 3’ UTR regions. Mutation rates increased over time in both infection types. This study demonstrates that NH4Cl effectively induces persistent SAT 2 FMDV infections in vitro by inhibiting replication and modulating viral evolution. These findings provide a valuable model for studying FMDV persistence and highlight key differences in viral adaptation between acute and persistent infections
Evaluation of different foot-and-mouth disease vaccination protocols in cattle in the Zambezi region of Namibia
Samuntu, Freddy (University of Pretoria, 2025-05)
Trade in beef products in Namibia was limited to geographic areas free from foot-and-mouth disease (FMD) until the inception of commodity-based trade. This study examined the equivalence of various vaccination protocols as part of a commodity-based trade initiative in the Zambezi Region of Namibia by determining whether the proportion of animals protected after vaccination with the Aftovaxpur vaccine (Botswana Vaccine Institute) containing FMD virus (FMDV) SAT-1, SAT-2, SAT-3 and O serotypes in the quarantine camp was significantly different to the proportion protected by field vaccination. Cattle (n = 131) were allocated into four groups. Group 1 (n = 40) consisted of cattle that had been vaccinated once in the field and again on entry to the quarantine camp, Group 2 (n = 29) consisted of cattle that had been vaccinated twice in the field and were not vaccinated in the quarantine camp and Group 3 (n = 39) consisted of cattle that tested positive to FMDV non-structural protein (NSP) antibodies to FMDV and were considered to have been naturally infected with FMDV. The three groups were quarantined for 30 days before slaughter at the Kopano quarantine facility located in Katima Mulilo, Zambezi region of Namibia. Group C (n = 23) was the control group and consisted of naïve cattle from south of the veterinary cordon fence that had never been vaccinated or exposed to FMDV. This group was vaccinated upon entry to the Kopano quarantine camp and again three weeks later. These animals were kept in the quarantine camp for 60 days. FMDV non-structural and structural protein antibody titres in cattle were determined at the start and end of the quarantine period. Cattle that tested positive for FMDV NSP antibodies at the beginning of quarantine were excluded from Groups 1 and 2. FMDV structural protein antibodies were determined with a liquid-phase blocking ELISA (LPBE) and a solid-phase competitive ELISA (SPCE). Cattle were considered protected against FMD if LPBE results were ≥ 1.6 or SPCE results > 50%. At the end of the quarantine period, a Z-test for independent proportions showed no significant differences (p > 0.05) between Groups 1, 2 or 3 and Group C for FMDV SAT-1, SAT-3 and O serotypes. There were, however, significant differences in the cattle protected against FMDV SAT-2 in Group 1 (100%, p = 0.001) and Group 3 (97.4%, p = 0.007) compared to Group C (78.3%). Independent-samples Mann-Whitney U tests compared FMDV antibody titres between Groups 1 or 2 and Group C. There were no significant differences for FMDV SAT-1 and O serotypes (p > 0.05), but significant differences for FMDV SAT-2: Group 1 (median = 2.0, p = 0.005) and Group 2 (median = 1.7, p = 0.044) compared to Group C (median = 1.8); and FMDV SAT-3: Group 1 (median = 2.2, p = 0.004) and Group 2 (median = 2.1, p = 0.003) compared to Group C (median = 1.9). The poorest immunogenic strain of the multivalent Aftovaxpur vaccine was FMDV SAT-2. The mean difference in LPBE titres between the start (day 0) and end (day 30 for Groups 1 and 2, and day 60 for Group C) of quarantine was 0.08 for Group 1, 0.23 for Group 2 and 0.59 for Group C. The most immunogenic vaccine strain was FMDV O serotype, with a mean difference in titres of 0.39 for Group 1, 0.61 for Group 2 and 0.94 for Group C. The results indicated that field vaccination was not equivalent to vaccination in the quarantine camp. There was a significant difference in the proportion of cattle with protective levels of antibodies for FMDV SAT-2 and significant differences in the median titres for FMDV SAT-2 and SAT-3 in field-vaccinated cattle compared to cattle vaccinated in the quarantine camp. There were differences in the immunogenicity of the FMDV strains in the vaccine, with serotype O being the most immunogenic and SAT-2 being the least immunogenic. The difference in protective levels of FMDV antibodies between field—and quarantine-vaccinated cattle depended on the serotype involved. Still, it was most likely due to field-vaccinated cattle receiving a booster and having a more mature immune response to the FMDV vaccine than quarantine-vaccinated cattle, who only received a primary series of vaccinations. The contribution emanating from this dissertation will add to the limited information available to support commodity-based trade, which will significantly help improve the lives of Namibian farmers north of the veterinary cordon fence.
Prevalence of antimicrobial-resistant Escherichia coli and Enterococcus species in pigs in northern Malawi, and the knowledge, attitudes and practices (KAP) amongst butchers
Luwe, Michael. (Prince Aaron) (University of Pretoria, 2025-03)
The prevalence of multidrug-resistant (MDR) opportunistic pathogens in many of the sub-Saharan countries has been one of the compelling reasons for proper mapping and management of the disease in hotspot areas. This study investigated the prevalence of antimicrobial-resistant Escherichia coli and Enterococcus species isolated from pigs in the northern part of Malawi and analysed the knowledge, attitudes and practices (KAP) of butchers concerning good hygienic practices. The KAP questionnaire was administered to 75 participants and 232 caecal samples were collected from pigs slaughtered at randomly selected slaughter places in Nkhata Bay, Rumphi, Mzimba, Karonga, and Mzuzu city. Overall KAP scores for knowledge, attitude, and practices were 81%, 73% and 46%, respectively. A positive correlation between the butchers’ knowledge and their attitude (r = .46, p<0.001), knowledge and practices (r = .38, p<0.001), and attitude and practices (r = .76, p<0.001) was observed. Microbiological tests confirmed the presence of Escherichia coli and Enterococcus species by biochemical tests. Escherichia coli resistance to ampicillin was high (82.2%) and this was followed by trimethoprim-sulfamethoxazole (75.8%), gentamicin (22.5%), cefotaxime (13.1%), ciprofloxacin (7.9%), and tigecycline (0.5%). In terms of Enterococcus species, resistance to vancomycin, ampicillin and ciprofloxacin were at 79.7%, 50% and 23.4%, respectively. No resistance to tigecycline was observed in all the Enterococcus isolates. The study also found that 26.7% (n=51) and 10.1% (n=16) of the E. coli and Enterococcus isolates, respectively, were resistant to more than one class of antibiotics. The study revealed a high risk of cross-contamination with resistant pathogens. Therefore, good hygienic practices in the farm-to-fork continuum, enforcement of food safety regulations and capacity building are pivotal in reducing the dissemination of resistant genes in the pork chain. The importance of antimicrobial stewardship should not be underemphasized if optimal utilisation of antimicrobials is to be attained.
Prevalence of Toxoplasma gondii in commensal pest rodents at the National Zoological Garden in South Africa
Thovhakale, Ndidzulafhi Terrence (University of Pretoria, 2023-10)
Toxoplasmosis is a zoonotic disease caused by the ubiquitous Apicomplexan protozoa Toxoplasma gondii (T. gondii). The overall epidemiology of T. gondii in Southern Africa is understudied. Although a few studies have documented its circulation in humans, domestic animals, and wild animals, these studies were limited in species diversity and geographical location. Rodents are intermediate hosts and are recognised as key reservoir hosts for T. gondii. Rodents play an important role in the maintenance and transmission of the parasite as they are preyed on by cats, the definitive hosts. Toxoplasma gondii infection rates in the local rodent population may reflect infection rates in cats. The aim of this study was to determine the prevalence of T. gondii in pest rodents within the South African National Biodiversity Institute National Zoological Garden (SANBI NZG). Furthermore, an attempt was made to confirm the presence of T. gondii DNA in the various rodents’ tissues (brain, tongue, muscle, diaphragm, and heart) using quantitative polymerase chain reaction (qPCR). A total of 138 sera were tested for T. gondii antibodies using a commercial latex agglutination test. A cut-off titre ≥ 64 was used to distinguish between positive and negative cases. Ten samples were positive for T. gondii antibodies, bringing the overall prevalence to 7.25% (95%, CI= 3.53 – 12.92). Using the generalised linear model, there was a statistically significant (p<0.00432) positive correlation between presence of T. gondii antibodies and rodent body weight. No T. gondii DNA amplification was observed on the tissue samples from the ten T. gondii antibody positive rodents. The results of this study provide baseline knowledge about the role of rodents in the epidemiology of T. gondii natural infections, particularly in the human-wildlife interface.
Nematodes diversity in Mastomys rodents (Rodentia: Muridae) and molecular characterization of Trichuris species in the Mnisi Community, South Africa
Mutesasira, Jesse Mukisa (University of Pretoria, 2023)
Nematodes comprise of many species with diverse life histories and zoonotic potential. Understanding the distribution and diversity of nematodes in the commensal rodent genus Mastomys is crucial for assessing their impact on wildlife and livestock, and potential of zoonotic disease transmission. The current study investigated the nematode diversity in Mastomys species rodents in three habitats and characterized the recovered Trichuris sp. using morphometric and molecular techniques at a wildlife-human/domestic animal interface in the Savanna biome in Mnisi communal area, Mpumalanga, South Africa. Nematodes were recovered and identified in the gastrointestinal tracts of 68 M. natalensis and 27 M. coucha rodents which were trapped in crop, village and natural habitats in the Mnisi communal area in October 2020. Nematodes were microscopically identified using morphometric measurements. Molecular characterization of Trichuris sp. was achieved through deoxyribonucleic acid (DNA) extraction, polymerase chain reaction (PCR), Sanger sequencing and phylogenetic analyses of three genes: internal transcribed spacers (ITS) 1, ITS 2 and cytochrome B (CytB). Data were analyzed using descriptive statistics, univariate models, a zero-inflated negative binomial generalized linear model, and a binomial generalised linear model, to establish the frequency, measures of central tendency and the relationships between nematode counts or occurrence and predictor variables using R statistical software. Nematodes were recovered in 20% of the examined rodents, with a total of 46 nematodes recovered, representing two species: Trichuris sp. (mean abundance of 0.31± 0.22) primarily from the caecum and Abbreviata sp. (mean abundance of 0.15±0.14) primarily from the stomach. Almost all the rodents were infected with only one nematode species, while one rodent exhibited mixed infection of both nematode species. No significant differences (p>0.05) in nematode prevalence were observed between male and female Mastomys spp. Univariate and multivariable analysis confirmed a lack of significant differences (p>0.05) in nematode abundance concerning habitat type, rodent species, and sex. The obtained novel Trichuris sp. ITS1, ITS2 and CytB sequences, clustered in a distinct clade from published sequences, but showing genetic relationships with known Trichuris spp. The current study emphasizes the importance of integrating morphometric identification and molecular analysis to accurately categorize Trichuris spp. and suggests a need for a larger sample size per habitat type in future research on nematode diversity.
Knowledge, attitudes and practices analysis of farmers on the risk of introducing peste des petits ruminants from Angola into northern communal areas of Namibia
Gorejena, Brighton (University of Pretoria, 2023-11)
Peste des petits ruminants (PPR) is a highly contagious viral disease primarily affecting goats, sheep, and some wild small ruminants. It is characterized by fever, necrotic stomatitis, gastroenteritis, pneumonia, and mortality. Namibia is officially free of PPR in one zone, not the entire country. The national herd has not been exposed to PPR and is naïve. Thus, an outbreak of the disease is potentially devastating on a socioeconomic level. The closest PPR outbreak was in Cabinda province in Angola. To better understand the risk factors for introducing PPR from Angola, a study was conducted using a knowledge, attitudes, and practices (KAP) survey. The research employed a qualitative descriptive survey design consisting of questionnaires and interviews with 376 communal farmers residing within 10-20 km of the Namibia/Angola border in Namibia's Omusati and Ohangwena regions. The results showed that 84% of the farmers surveyed had insufficient knowledge regarding PPR, while 89% were unaware of its clinical symptoms. Nevertheless, the farmers showed good comprehension of general disease prevention techniques, including vaccination (99%), livestock isolation (85%), quarantine (72%), and regulated animal movements (94%). Additionally, the farmers exhibited awareness of the detrimental effects of disease outbreaks (90%). It was concluded that farmers' knowledge, attitudes, and practices (KAP) in Namibia's surveyed northern communal areas present a moderate risk of PPR incursion. The current surveillance strategies the competent authority implements are deemed sufficient and can be sustained. However, the study recommends enhancing PPR awareness among northern communal farmers, particularly those living near the Namibia/Angola border.
Molecular detection of tick-borne haemoparasites in cattle and buffalo samples from Mashonaland West and Masvingo Provinces, Zimbabwe
Modirwa, Annicky A.R. (University of Pretoria, 2022)
Tick-borne haemoparasite diseases caused by Babesia, Theileria, Anaplasma and Ehrlichia species are a major constraint to the beef and dairy cattle industry, causing the most economic losses of cattle in sub-Saharan Africa. The cattle industry in Zimbabwe is continuously threatened by the spread of tick-borne diseases, which significantly affect the economy not only through morbidity and mortality but also through the costs involved in the control of diseases and treatment of sick animals. However, there is a lack of current data on the distribution of tick-borne diseases in Hurungwe district, Mashonaland West Province. The current study used molecular tools to investigate the occurrence of haemoparasites in cattle from Hurungwe district in Mashonaland West Province and buffalo from Gonarezhou National Park in Zimbabwe. DNA was extracted from 87 whole blood samples including 80 cattle and seven buffalo. The DNA samples were subjected to the Reverse-line blot hybridization (RLB) and quantitative real-time polymerase chain reaction (qPCR) analyses. Haemoparasite infections were detected in 58 samples (67 %) by RLB, and 55 % of these only hybridized to the genus-specific probes. Tick-borne haemoparasites detected by RLB included three Theileria species (T. mutans, T. velifera, and Theileria sp. sable), detected in single and mixed-parasite infections. Anaplasma centrale (3 %) and Babesia bigemina (1 %) were also detected by the RLB assay. The most commonly occurring tick-borne pathogens in cattle detected by qPCR assays were A. marginale (28 %) and B. bigemina (9 %); followed by A. centrale (8 %) and B. bovis (3 %). While in buffalo A. marginale (86 %), followed by A. centrale (14 %) were mostly detected. The results of the current study indicated that the species-specific qPCR assays used were more sensitive in detecting haemoparasites than the RLB assay. Anaplasma marginale and Babesia bovis were only detected by the species-specific qPCR assays and not by the RLB assay, which suggests that these haemoparasite infections were present at low levels thus could not be detected by RLB assay. The RLB assay suffers lower sensitivity when a sample is infected with more than one haemoparasite, especially when the levels of infection vary; the high infection will be preferentially detected over low infections of the same genus due to primer competition. Notably, T. parva or E. ruminantium was not detected from the investigated samples. The amplification and sequencing of the 16S and 18S rRNA genes from samples that hybridized exclusively to the RLB genus-specific probes yielded nine and one good quality sequences, for the 16S and 18S rRNA genes respectively. However, BLASTn analysis did not reveal hits to any haemoparasites expected to occur in cattle and buffalo. Our results did not follow the common trend for the prevalence of tick-borne diseases of cattle in Zimbabwe. Bovine theileriosis has recently been reported to be responsible for most cattle mortalities in Zimbabwe, followed by babesiosis, heartwater, and then anaplasmosis. Our results therefore suggest that the trend of occurrence of tick-borne diseases depends on the vector-parasite-host-environment dynamics for each province, thus may vary between provinces. Finally, this study confirms that buffalo in the sampled area are carriers of tick-borne diseases that pose risk to the cattle population.
Knowledge, attitudes and practices analysis, prevalence and molecular detection of Neospora caninum and Toxoplasma gondii in livestock in the Khomas region of Namibia
Samkange, Alaster (University of Pretoria, 2023-12)
This study chiefly focussed on the Khomas region of Namibia, and the research areas were: (1) the knowledge, attitudes and practices regarding neosporosis and toxoplasmosis among livestock farmers in the Khomas region and animal health practitioners in the whole country; (2) the seroprevalence and associated risk factors of Neospora caninum in cattle; (3) the seroprevalence and associated risk factors of Toxoplasma gondii in sheep and goats; (4) molecular investigation of N. caninum DNA in cattle and, (5) the molecular detection of T. gondii in sheep and goats in abattoir samples. Only 15.9% (10/63) of the livestock farmers had heard about neosporosis or toxoplasmosis or knew how animals get infected (p<0.0001). Five per cent (3/63) of the farmers knew the risks associated with keeping dogs and cats concerning neosporosis and toxoplasmosis, respectively (p<0.0001). None of the animal health practitioners (n=51) routinely requested N. caninum or T. gondii laboratory tests in cases of cattle, sheep or goat abortions. Although all animal health practitioners indicated they routinely interacted with livestock farmers, none regularly discussed neosporosis or toxoplasmosis. Five point seven per cent (42/736) of the bovine sera were seropositive to N. caninum. Eight of the 32 establishments had at least one positive animal, giving a herd-level seroprevalence of 25%. There was no significant association between N. caninum seropositivity in cattle and the presence of dogs, jackals, history of abortions, farm size, and the number of cattle or average annual rainfall. The establishments with moderate to high numbers of Feliformia were 9.8 times more likely to be seropositive to N. caninum than those with none to low levels of the former (p=0.0245). Overall, 3.68% (11/299) of the sheep sera were seropositive to T. gondii, and 61.54% (8/13) of the sheep flocks tested had at least one positive animal. Only 0.29% (1/345) of the goat sera were seropositive to T. gondii, and one of the 19 goat flocks had at least one positive animal, giving a herd-level prevalence of 5.26%. Sheep flocks had significantly greater animal-level and flocklevel prevalences than goats (p<0.05) and were 13.14 times more likely to be seropositive (OR = 13.14; CI 95%: 1.686-102.382) than goat flocks. Seropositivity to T. gondii was positively associated with the total number of sheep at the farming establishment, history of abortions and farm size (p<0.05), but not goats. The study concluded that sheep were probably more exposed to T. gondii infection than goats and that the T. gondii seroprevalence level in the Khomas region was very low compared to other countries. One hundred and ninety-nine bovine abattoir samples were collected from different animals, comprising 110 brain samples and 75 heart muscle samples. In addition, there were 14 whole blood samples from N. caninum seropositive cattle. The collected samples were tested using a conventional PCR targeting the pNc5 gene. All the samples tested were negative. The authors concluded that the negative results could be due to the low prevalence of N. caninum infection caused by adverse weather conditions and that a future study targeting aborted fetuses over a more extended period could yield positive results. The T. gondii molecular study analysed 174 brain and heart tissue samples from sheep and goats for the presence of T. gondii DNA using nested PCR targeting the B1 gene. The tissue samples were obtained from animals at abattoirs designated for human consumption. The study found that 16.7% of the samples tested positive for T. gondii DNA, with a higher prevalence in sheep (17.4%) than in goats (7.7%). Eight of the 29 positive samples were successfully sequenced using the Sanger method. All isolates identified were closely related to T. gondii type III genotype, exhibiting alignment scores ranging from 96.44% to 100%. This study emphasizes the public health hazards of consuming undercooked sheep and goat meat and highlights the pressing need to introduce control measures to mitigate human exposure.

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