1998 Onderstepoort Journal of Veterinary Research, Volume 65, 1998

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CONTENTS

*Volume 65: Number 1*

Detection of African horsesickness virus and discrimination between two equine orbivirus serogroups by reverse transcription polymerase chain reaction	Bremer, CW & Viljoen, GJ	1

Morphological confirmation of the separate species status of Culicoides (Avaritia) nudipalpis Delfinado, 1961 and C. (A.) imicola Kieffer, 1913 (Diptera: Ceratopogonidae)	Meiswinkel, R & Baylis, M	9

Krimpsiekte in a sheep following a single dose of Tylecodon ventricosus (Burm. f.) Toelken and the isolation of tyledoside D from this plant species	Vleggaar, R, Botha, CJ, Van der Lugt, JJ, Erasmus, GL, Kellerman, TS & Schultz, RA	17

Suspected cardiac glycoside intoxication in sheep and goats in Namibia due to Ornithogalum nanodes (Leighton)	Bamhare, C	25

Distribution of endocrine cells in the gut of the impala (Aepyceros melampus)	Schoeman, JH, De Vos, V & Van Aswegen, G	31

Detection and characterization of foot-and-mouth disease virus in sub-Saharan Africa	Bastos, ADS	37

Dynamics of free-living ixodid ticks on a game ranch in the Central Province, Zambia	Horak, IG, Zieger, U & Cauldwell, AE	49

Guide for authors		61


*Volume 65: Number 2*

Comparison of immune responses of two Salmonella gallinarum strains viewed as possible vaccines for fowl typhoid in Kenya	Nyaga, PN, Kimoro, CO & Bebora, LC	67

Isolation and characterization of a Babesia species from Rhipicephalus evertsi evertsi ticks picked off a sable antelope (Hippotragus niger) which died of acute babesiosis	Hove, T, Sithole, N, Munodzana, D & Masaka, S	75

Observations on the use of Anaplasma centrale for immunization of cattle against anaplasmosis in Zimbabwe	Turton, JA, Katsande, TC, Matingo, MB, Jorgensen, WK, Ushewokunze-Obatolu, U & Dalgliesh, RJ	81

Three new species of ciliated protozoa from the hindgut of both white and black wild African rhinoceroses	Van Hoven, W, Gilchrist, FMC, Liebenberg, H & Van der Merwe, CF	87

Immunization of rabbits with Amblyomma hebraeum nymphal homogenates and implications for the host amplification system	Tembo, SD	97

The clinical efficacy of enrofloxacin in the treatment of experimental bovine pneumonic pasteurellosis	Thompson, PN, Van Amstel, SR & Henton, MM	105

Ixodid tick infestations of wild birds and mammals on a game ranch in Central Province, Zambia	Horak, IG, Zieger, U, Cauldwell, AE & Uys, AC	113

Selection of an scFv phage antibody that recognizes bluetongue virus from a large synthetic library and its use in ELISAs to detect viral antigen and antibodies	Van Wyngaardt, W & Du Plessis, DH	125

Reseasrch communications:

An epidemic of besnoitiosis in cattle in Kenya	Njagi, ON, Ndarathi, CM, Nyaga, PN & Munga, LK	133

Helminths and bot fly larvae of wild ungulates on a game ranch in Central Province, Zambia	Boomker, JDF, Horak, IG, Zieger, U & Cauldwell, AE	137

Book review:

Contamination of animal products: prevention and risks for public health		143


*Volume 65: Number 3*

Some epidemiological and economic aspects of a bluetongue-like disease in cattle in South Africa - 1995/96 and 1997	Barnard, BJH, Gerdes, GH & Meiswinkel, R	145

Spauligodon timbavatiensis n. sp. (Nematoda: Pharyngodonidae) from Pachydactylus turneri (Sauria: Gekkonidae) in the Northern Province, South Africa	Boomker, JDF & Hering-Hagenbeck, SFBN	153

Pentastomid infections in cichlid fishes in the Kruger National Park and the description of the infective larva of Subtriquetra rileyi n. sp	Boomker, JDF, Booyse, DG & Junker, K	159

The absence of clinical disease in cattle in communal grazing areas where farmers are changing from an intensive dipping programme to one of endemic stability to tick-borne diseases	Tice, GA, Bryson, NR, Stewart, CG, Du Plessis, B & De Waal, DT	169

The distribution of heartwater in the highveld of Zimbabwe, 1980-1997	Peter, TF, Perry, BD, O'Callaghan, CJ, Medley, GF, Shumba, W, Madzima, W, Burridge, MJ & Mahan, SM	177

Serum biochemical values of farmed ostrich (Struthio camelus) in Botswana	Mushi, EZ, Binta, MG, Chabo, RG, Isa, JFW & Modisa, LA	189

Review of tsetse flies and trypanosomosis in South Africa	Kappmeier, K, Nevill, EM & Bagnall, RJ	195

Parasites of domestic and wild animals in South Africa. XXXV. Ixodid ticks and bot fly larvae in the Bontebok National Park	Horak, IG & Boomker, JDF	205

The production of an auxotrophic marked, plasmid-cured Salmonella ser. Typhimurium as a live attenuated vaccine	Van der Walt, ML & Greeff, AS	213

Book review:

Genetic resistance to animal disease		221


*Volume 65: Number 4*

The African monogenean gyrodactylid genus Macrogyrodactylus Malmberg, 1957, and the reporting of three species of the genus on Clarias gariepinus in South Africa	Khalil, LF & Mashego, SN	223

Experimental studies on the life-cycle of Sebekia wedli (Pentastomida: Sebekidae)	Boomker, JDF, Booyse, DG & Junker, K	233

Antigenic and genetic analysis of canine parvoviruses in southern Africa	Venter, EH, Steinel, A, Van Vuuren, M, Parrish, CR & Truyen, U	239

A study on bluetongue virus infection in Saudi Arabia using sentinel ruminants	Abu Elzein, EME, Aitchison, H, Al-Afaleq, AI, Al-Bashir, AM, Ibrahim, AO & Housawi, FMT	243

Light and electron microscopical observations on the terminal airways and alveoli of the lung of the SA (Cape) fur seal Arctocephalus pusillus	Wessels, JC & Chase, CC	253

Models for heartwater epidemiology: practical implications and suggestions for future research	Yonow, T, Brewster, CC, Allen, JC & Meltzer, MI	263

The efficacy of used engine oil against ticks on cattle	Dreyer, K, Fourie, LJ & Kok, DJ	275

Coccidia oocysts in the faeces of farmed ostrich (Struthio camelus) chicks in Botswana	Mushi, EZ, Isa, JFW, Chabo, RG, Binta, MG, Kapaata, RW, Ndebele, RT & Chakalisa, KC	281

Epidemiology of tick-borne diseases of cattle in Botshabelo and Thaba Nchu in the Free State Province	Dreyer, K, Fourie, LJ & Kok, DJ	285

Individual host variations in tick infestations of cattle in a resource-poor community	Dreyer, K, Fourie, LJ & Kok, DJ	291

A nucleotide-specific polymerase chain reaction assay to differentiate rabies virus biotypes in South Africa	Nel, LH, Bingham, J, Jacobs, JA & Jaftha, JB	297

Tick diversity, abundance and seasonal dynamics in a resource-poor urban environment in the Free State Province	Dreyer, K, Fourie, LJ & Kok, DJ	305

Correlation between ability of Ornithobacterium rhinotracheale to agglutinate red blood cells and susceptibility to fosfomycin	Fitzgerald, SL, Greyling, JM & Bragg, RR	317

Protein aggregation complicates the development of baculovirus-expressed African horsesickness virus serotype 5 VP2 subunit vaccines	Du Plessis, M, Cloete, M, Aitchison, H & Van Dijk, AA	321

Author index		331

Subject index		339

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Now showing 1 - 20 of 45

A nucleotide-specific polymerase chain reaction assay to differentiate rabies virus biotypes in South Africa
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Bingham, J.; Jacobs, Jeanette Antonio; Jaftha, Julian Bernard; Verwoerd, Daniel Wynand; Nel, Louis Hendrik
Antigenic and nucleotide sequence analyses have shown that two distinct biotypes of rabies virus are circulating in South Africa. One of these typically infects members of the family Canidae, while the other comprises a heterogeneous group of apparently indigenous viruses, infecting members of the Viverridae family. In recent times, it has become evident that a considerable amount of crossinfection may occur and the manifestation of viverrid rabies in non-viverrid animals in particular appears to have become more commonplace. Consequently, the need to rapidly distinguish between rabies virus biotypes has become increasingly important in efforts to monitor the epidemiology of rabies in the southern African region. In this study, a nested polymerase chain reaction (PCR) assay was developed to distinguish between these two groups of rabies viruses. Consensus oligonucleotides were used to amplify the cytoplasmic domain of the rabies virus glycoprotein and the adjacent intergenic region. The resultant amplicon was subsequently used as template in a second round heminested PCR in the presence of type-specific primers, thereby successfully generating amplicons of characteristic size for each biotype.
Models for heartwater epidemiology: practical implications and suggestions for future research
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Yonow, T.; Brewster, C.C.; Allen, J.C.; Meltzer, M.I.; Verwoerd, Daniel Wynand
We present a simple model of the dynamics of heartwater that we use to explore and better understand various aspects of this disease. We adapted the Ross-Macdonald model for malaria epidemiology so that we could consider both host and vector populations, and evaluate the interactions between the two. We then use two more biologically detailed models to examine heartwater epidemiology. The first includes a carrier state and host mortality, and the second includes density dependence. The results from all three models indicate that a stable equilibrium with high disease levels is probably the standard situation for heartwater (R₀ between 5,7 and 22,4). More than 80% of cattle become infected with heartwater if only 12% of infected tick bites produce an infection in cattle, if tick burdens are as low as only five ticks per host per day, or if tick lifespans are as short as 7 d. A host recovery rate of 30 d results in over 50% of the cattle becoming infected with heartwater. Our analyses indicate that it is quite difficult to prevent the establishment and maintenance of high levels of heartwater in a herd, thereby supporting previous suggestions that any attempts at controlling this disease through stringent tick control regimens are not warranted.
The production of an auxotrophic marked, plasmid-cured Salmonella ser. Typhimurium as a live attenuated vaccine
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Van der Walt, M.L.; Greeff, A.S.; Verwoerd, Daniel Wynand
A number of amino acid requiring auxotrophic strains of SalmonellaTyphimurium were produced by chemical mutagenesis. One of them, strain 81, was cured of the virulence plasmid and attenuated for mice. This strain had an auxotrophic requirement for serine, which could be used as a marker for the differentiation of the vaccine strain from other isolates in the field. The strain still contained the smooth form of the 0-antigen, was resistant to Complement-mediated killing of serum and produced type 1 fimbriae. Of the six auxotrophic mutants only this mutant differed in its outer membrane protein profile from that of the parent strain in that an outer membrane protein of about 30 kDa was absent. With the use of the polymerase chain reaction, using total DNA of the cell as template, and with primers targeted to the virulence plasmid, it was shown that the virulence plasmid of SalmonellaTyphimurium was completely cured from this strain. This strain also had a LD₅₀-value of 4 log units lower for mice than the parent strain. The plasmid-cured strain gave a very high degree of protection to mice after systemic immunization, but not after oral vaccination. Compared to the parent, strain 81 also had a lower multiplication rate in the liver and spleen after intraperitoneal inoculation, characteristics that could be attributed to plasmid-loss, and it could also not be recovered from the spleen and liver of orally inoculated mice.
Individual host variations in tick infestations of cattle in a resource-poor community
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Dreyer, K.; Fourie, L.J.; Kok, D.J.; Verwoerd, Daniel Wynand
Relative resistance levels of cattle against tick infestations in the communal grazing area of Botshabelo in the south-eastern Free State were determined. The objective was to establish whether differences in resistance can be exploited to contribute to tick control methods used by small-scale farmers in resource-poor environments. Ten cows (Bos taurus crosses) between the ages of 18 months and four years were used and tick counts were conducted once a month over a period of 12 months to compare their total tick burdens. Tick burdens of the various animals were compared mutually as well as with the mean tick burden of the group as a whole. Tick numbers varied throughout the year on all individuals but some animals consistently tended to have either higher or lower numbers than the mean of the group. Tick burdens on cattle classified as having a relatively low resistance to tick infestations increased eleven-fold from January to June 1996 compared to a six-fold increase on cattle categorized as belonging to the high resistance group. Twenty-eight percent of the cattle in the total study group carried 50% of the ticks collected (60 079). It is recommended that farmers in the region visually assess B. decoloratus burdens, the most abundant tick species, and sell or cull the most susceptible animals first in their normal program of utilization of the animals. This should eventually result in the direct improvement of the overall tick resistance of their cattle herds.
Coccidia oocysts in the faeces of farmed ostrich (Struthio camelus) chicks in Botswana
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Mushi, E.Z.; Isa, J.F.W.; Chabo, R.G.; Binta, M.G.; Kapaata, R.W.; Ndebele, R.T.; Chakalisa, K.C.; Verwoerd, Daniel Wynand
Coccidia oocysts were demonstrated in the faeces of 53 (about 34 %) of 156 apparently healthy ostrich chicks. Young chicks had the highest proportion of infestation while those more than 9 weeks old had no oocysts at all in their faeces. These coccidia may be considered non pathogenic since the infected chicks grew normally without any evidence of diarrhoea.
The efficacy of used engine oil against ticks on cattle
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Dreyer, K.; Fourie, L.J.; Kok, D.J.; Verwoerd, Daniel Wynand
The study was conducted in a peri-urban agricultural system at Botshabelo, a city in the south-eastern Free State. A questionnaire survey revealed that 88,5% of cattle farmers in the area experienced problems related to ticks and tick-borne diseases. Because of the cost of commercial acaricides the Botshabelo farmers use alternative, cheaper methods of tick control, including the application of used engine oil. The specific aim of the study was to determine whether used engine oil can effectively control ticks on cattle. From March to August 1996 the tick burdens of ten control animals and six animals treated by their owner with used engine oil were compared. The total tick burdens for the 6 month period differed significantly between the two experimental groups. The efficacy of the used engine oil on the treated group varied between 15,1% and 64,8% with a mean of 38,1 %. Although commercial acaricides can be more cost-effective, the application of used engine oil can be useful to reduce tick numbers on cattle during periods of peak abundance. Another advantage is that the use of the oil will not influence existing endemic stability to Anaplasma marginale and Babesia bigemina infections because of the residual tick burdens after treatment.
Tick diversity, abundance and seasonal dynamics in a resource-poor urban environment in the Free State Province
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Dreyer, K.; Fourie, L.J.; Kok, D.J.; Verwoerd, Daniel Wynand
The objectives of this study were to determine the diversity, seasonal dynamics and abundance of ticks infesting cattle in urban, small-scale farming communities in and around Botshabelo and Thaba Nchu in the eastern Free State Province, South Africa. A total of ten cattle, ear-tagged for individual identification, were investigated monthly at each of five localities. Adult ticks were removed from the right hand side of each animal and placed in containers filled with 70% ethanol. They were subsequently identified and their numbers quantified. Immature Otobius megnini were counted but not removed. A total of 244 538 adult ticks of ten different species were collected over the 12-month study period. The tick species, in decreasing order of relative abundance, were: Boophilus decoloratus (87,26%), Rhipicephalus evertsi evertsi (6,86%), Hyalomma marginatum rufipes (2,42%), Otobius megnini (1,85%) Rhipicephalus follis (0,76%), Rhipicephalus gertrudae (0,54%), Rhipicephalus sp. (0,21 %), Ixodes rubicundus (0,08%), Hyalomma truncatum (0,01 %) and Margaropus winthemi (0,004 %). The three most abundant species, namely B. decoloratus, R. evertsi evertsi and H. marginatum rufipes, occurred at all localities but with significant differences in abundance. M. winthemi ticks occurred only in the Thaba Nchu area and were not found at any of the three localities in Botshabelo. Significant differences in tick burdens between the six warm months (September to February) and the six cooler months (March to August) were found for most of the species recorded. Boophilus decoloratus occurred in significantly higher numbers in autumn (March to May) and winter (June to August) compared to spring (September to November) and summer (December to February), with 76,8% of the total B. decoloratus burden occurring during the cooler months.
Epidemiology of tick-borne diseases of cattle in Botshabelo and Thaba Nchu in the Free State Province
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Dreyer, K.; Fourie, L.J.; Kok, D.J.; Verwoerd, Daniel Wynand
A seroepidemiological study was conducted on 151 cattle from the Botshabelo and Thaba Nchu areas in the central Free State Province of South Africa, two areas where small scale, peri-urban cattle farming is practised. An indirect fluorescent antibody test was used to test for Babesia bigemina and B. bovis antibodies. To test for Anaplasma marginale antibodies a competitive inhibition enzyme-linked immunosorbent assay method was used. There were no significant differences in serological test results between the cattle from Botshabelo and those from Thaba Nchu. The herd (two areas combined) had an average seroprevalence of 62,42% to B. bigemina, 19,47% to B. bovis and 98,60% to A. marginale. Based on the percentage of cattle that were seropositive to B. bigemina the immune status of cattle in the Botshabelo-Thaba Nchu area is approaching a situation of endemic stability. With reference to A. marginale, the high seroprevalence is indicative of a situation of endemic stability. The occurrence of B. bovis antibodies in the cattle is difficult to explain as Boophilus microplus ticks do not occur in the area in which the study was conducted.
Subject index
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Anonymous; Verwoerd, Daniel Wynand
Author index
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Anonymous; Verwoerd, Daniel Wynand
Protein aggregation complicates the development of baculovirus-expressed African horsesickness virus serotype 5 VP2 subunit vaccines
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Du Plessis, M.; Cloete, M.; Aitchison, Henry; Van Dijk, A.A.; Verwoerd, Daniel Wynand
This paper describes the expression of a cloned African horsesickness virus (AHSV) serotype 5 VP2- gene by a baculovirus recombinant that was generated by the BAC-TO-BAC™ system. Immunization of horses with crude cell lysates containing recombinant baculovirus-expressed AHSV5 VP2 did induce neutralizing antibodies, but afforded only partial protection against virulent virus challenge. Further analysis of partially protective crude cell lysates revealed that baculovirus-expressed AHSV5 VP2 was predominantly present in the form of insoluble aggregates. Only approximately 10% of VP2 was present in a soluble form. Immunization of guinea-pigs with aggregated and soluble forms of AHSV5 VP2 established that only soluble VP2 was capable of inducing neutralizing antibodies. This finding adds a new dimension to the development of AHSV VP2s as subunit vaccines. Further investigation is needed to limit formation of insoluble aggregates and optimize conditions for producing VP2 in a form capable of inducing protective immunity.
The clinical efficacy of enrofloxacin in the treatment of experimental bovine pneumonic pasteurellosis
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Van Amstel, S.R.; Henton, Marijke M.; Verwoerd, Daniel Wynand; Thompson, P.N. (Peter N.)
The clinical efficacy of enrofloxacin was tested in calves with experimentally induced pneumonic pasteurellosis. A strain of Pasteurella haemolytica, biotype A, serotype 1 (P haemolytica A 1), which had been isolated from an outbreak of pneumonic pasteurellosis in feedlot calves, was used to induce the disease in 24 eight-month-old calves. Each animal received, by intratracheal injection, 6 x 10¹¹ colony forming units of P haemolytica A 1 in a four-hour log phase culture. Twelve similar animals were kept as non-infected controls (Negative Control group). Treatment of the infected animals commenced 40 h after infection and was as follows: 12 animals each received 2,5 mg/kg enrofloxacin subcutaneously and 12 animals each received 5 ml sterile saline intramuscularly (Positive Control group). All treatments were given once daily for three consecutive days. Clinical examinations were performed on all animals once daily, starting prior to infection and continuing until 12 d post-infection. The parameters evaluated were rectal temperature, habitus (attitude), ocular mucous membrane congestion and abnormal sounds on lung auscultation. On day14 post-infection, all animals were killed and their lung lesions (if any) estimated as the percentage involvement of each pair of lungs. The only statistically significant (P≥ 0,05) differences observed were between the Negative Control group and the Positive Control group. Noticeable differences were seen between the enrofloxacin-treated group and the Positive Control group, but they were not statistically significant (P> 0,05). The average lung lesion score (pneumonic lesions as a percentage of total lung volume) for the Positive Control group was 12,1 % and that of the enrofloxacin-treated group, 8,4 %. This difference was not statistically significant (P > 0,05) .
Correlation between ability of Ornithobacterium rhinotracheale to agglutinate red blood cells and susceptibility to fosfomycin
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Fitzgerald, S.L.; Greyling, J.M.; Bragg, R.R. (Robert Richard); Verwoerd, Daniel Wynand
Twenty five freeze-dried isolates of Ornithobacterium rhinotracheale were used for the determination of minimum inhibitory concentrations (MIC) against the antibiotic fosfomycin (Fosbac, produced by Bedson SA, consisting of a 25% mixture of fosfomycin). The same isolates were tested for their ability to haemagglutinate chicken red blood cells. Ten of the 25 isolates were found to be susceptible to fosfomycin (MIC values below 128 ug/ml). All of these isolates were able to agglutinate red blood cells. This is the first report on the ability of O. rhinotracheale to agglutinate red blood cells. The remaining 15 isolates were resistant to fosfomycin (MIC values above 128 ug/ml). Only five of these isolates were found to have the ability to agglutinate red blood cells. There appears to be a correlation between the ability of O. rhinotracheale isolates to agglutinate red blood cells and their susceptibility to fosfomycin. The ability of certain isolates of O. rhinotracheale to agglutinate red blood cells, raises the questions of differences in virulence between the isolates which can agglutinate red blood cells and those which cannot and the use of this ability to agglutinate red blood cells as an alternative method for serotyping O. rhinotracheale.
Light and electron microscopical observations on the terminal airways and alveoli of the lung of the SA (Cape) fur seal Arctocephalus pusillus
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Wessels, J.C.; Chase, C.C.; Verwoerd, Daniel Wynand
During activities of the Sea Fisheries Research Institute at Kleinzee, lung samples from six South African fur seals were collected. The terminal airways showed pseudostratified ciliated columnar epithelium with numerous goblet cells and occasional brush cells. Smooth muscle, cartilage and submucosal glands were also present. The epithelium changed over a short distance, in the smaller airways, through pseudostratified columnar non-ciliated to simple cuboidal epithelium with no goblet cells. The columnar non-ciliated cells contained secretory granules, which appeared to be serous. No Clara cells were found. Cartilage and muscle were present throughout, up to the origin of the alveolar ducts, but the glands disappeared together with the goblet cells. Alveoli were lined by types one and two alveolar epithelial cells, with subepithelial capillaries. They were divided by an alveolar septum with a well developed alveolar knob. This knob contained elastic fibres and fibroblasts, but not the smooth muscle cells which are present in terrestrial mammals and in Phocidae.
A study on bluetongue virus infection in Saudi Arabia using sentinel ruminants
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Abu Elzein, E.M.E.; Aitchison, Henry; Al-Afaleq, A.I.; Al-Bashir, A.M.; Ibrahim, A.O.; Housawi, F.M.T.; Verwoerd, Daniel Wynand
Four sentinel herds comprising cattle, sheep and goats were established at various localities in Saudi Arabia. Maternal bluetongue antibodies were detected in all four sentinel herds but disappeared in 4- 6 months, immediately followed by seroconversion in all. Serological results indicated that the animals were recently exposed to BT virus serotypes 10, 12, 15 and 20. The epidemiology of the disease in Saudi Arabia is discussed.
Review of tsetse flies and trypanosomosis in South Africa
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Kappmeier, Karin; Nevill, E.M.; Bagnall, R.J.; Verwoerd, Daniel Wynand
The history of tsetse flies and nagana (trypanosomosis) in South Africa, and especially in Zululand, is reviewed. Four valid tsetse fly species have been recorded from South Africa. Glossina morsitans morsitans disappeared from the most northerly parts of South Africa during the rinderpest epizootic between 1896-1897. Of the three remaining species that occurred in Zululand, now part of KwaZulu· Natal Province, G. pallidipes was the most common vector of nagana in cattle, but was eradicated from this area in 1954. G. brevipalpis and G. austeni remained but were responsible for only a few sporadic cases of nagana up until 1990. A widespread outbreak occurred in 1990 where cattle served by 61 diptanks were found infected with Trypanosoma congolense and T. vivax. Dipping of cattle in a pyrethroid plus the therapeutic treatment of infected animals brought the disease under control. The outbreak also led to a trial to control G. brevipalpis from the most northerly parts of the Hluhluwe/ Umfolozi Game Reserve making use of target technology as for savannah species. The results were not satisfactory and the trial was discontinued until further research could provide a more appropriate system for the control of this species. A Tsetse Research Station was established at Hellsgate near St. Lucia Lake where research on G. brevipalpis and G. austeni is conducted into ways and means of monitoring and controlling these species.
Serum biochemical values of farmed ostrich (Struthio camelus) in Botswana
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Mushi, E.Z.; Binta, M.G.; Chabo, R.G.; Isa, J.F.W.; Modisa, Lorna A..; Verwoerd, Daniel Wynand
Reference biochemical values for serum analytes of 126 clinically normal farmed ostriches on one farm in Botswana were established. These included sodium, potassium, chloride, total protein, albumin, urea, creatinine, uric acid, cholesterol, total bilirubin, conjugated bilirubin, glucose, triglyceride, calcium, phosphorus, manganese, copper, zinc, alkaline phosphatase, gamma glutamyl transferase and creatinine kinase. The values obtained in this study can be used as reference values.
Antigenic and genetic analysis of canine parvoviruses in southern Africa
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Steinel, A.; Parrish, C.R.; Truyen, U.; Verwoerd, Daniel Wynand; Van Vuuren, Moritz; Venter, Estelle Hildegard
Canine parvovirus (CPV) is a significant pathogen of domestic and free-ranging carnivores all over the world . It suddenly appeared at the end of the 1970s and most likely emerged as a variant of the well known feline panleukopenia virus (FPV). During its adaptation to the new host, the domestic dog, the virus has changed its antigenic profile twice giving rise to two new antigenic types, CPV-2a and CPV-2b. These new types have replaced the original type CPV-2 in the United States of America, Europe and Japan. However, no data about the prevalence of the new antigenic types on the African continent are available. In this study, 128 recent parvovirus isolates from South Africa and Namibia were antigenically typed with type-specific monoclonal antibodies. No original CPV-2 viruses were found and its complete replacement by the new antigenic types conforms to the situation in other parts of the world. The predominant strain found in southern Africa was CPV-2b (66 %), which differs from the situation in Europe and Japan where CPV-2a is the most prevalent type. Analysis of the capsid protein DNA-sequences of four selected African isolates gave no hint of a specific African parvovirus lineage.
The distribution of heartwater in the highveld of Zimbabwe, 1980-1997
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Peter, T.F.; Perry, B.D. (Brian D.), 1946-; O'Callaghan, C.J.; Medley, G.F.; Shumba, W.; Madzima, W.; Burridge, M.J.; Mahan, S.M.; Verwoerd, Daniel Wynand
Heartwater, the tick-borne disease caused by the rickettsia Cowdria ruminantium has historically been confined to the southern and western lowvelds of Zimbabwe. Since 1986, however, cases of heartwater have been diagnosed with increasing frequency in the central and eastern regions of the previously heartwater-free highveld plateau. During the same period, collections of the two major tick vectors of heartwater in Zimbabwe, Amblyomma hebraeum and Amblyomma variegatum, were made for the first time in these areas, suggesting that spread of these ticks was responsible for the changed distribution of the disease. The factors associated with this spread have not been determined, but increased cattle and wildlife movement and reduced intensity of dipping undoubtedly play important roles. Currently, the distribution of heartwater and its vectors in the highveld is still largely restricted to the central and eastern regions. The northern regions of the highveld appear to be predominantly uninfected, though it is likely that, eventually, heartwater will spread further with considerable impact on livestock production in Zimbabwe.
The absence of clinical disease in cattle in communal grazing areas where farmers are changing from an intensive dipping programme to one of endemic stability to tick-borne diseases
(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998) Tice, G.A.; Bryson, N.R.; Stewart, C.G.; Du Plessis, B.; De Waal, D.T.; Verwoerd, Daniel Wynand
A two-year field study was conducted in four communal grazing areas in South Africa. Sera were collected from young cattle (6-18 months old) in these areas during the winters of 1991 to 1993. The sera were tested for antibodies to Babesia bovis, Babesia bigemina, Anaplasma marginale and Cowdria ruminantium. In two of the four areas, treatment with acaricide was erratic and dependent on the discretion of individual owners. In these areas the drought of 1992 had a major impact on tick burdens and there were changes in the seroprevalence to tick-borne diseases. In the other two areas there was a reduction in the intensity of acaricide application and this was associated with an increase in seropositivity to the tick-borne diseases. Increases in the prevalence of seropositivity and the presence of endemic instability, as calculated from inoculation rates, were not accompanied by outbreaks of clinical disease. Possible reasons for this are discussed.

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