One Health investigation at abattoirs in South Africa

Abstract

One Health is a collaborative, multisectoral, and transdisciplinary strategy/approach with the aim of attaining the best possible health outcomes that acknowledge the connections between humans, animals, plants, and their common environment at the local, national, regional, and global levels. Zoonoses pose a threat to environmental integrity, animal and human welfare, and economic development. In this One Health project, zoonotic diseases were investigated that influence the health of abattoir workers and domestic animals slaughtered in this environment. Zoonotic diseases such as brucellosis and coxiellosis (Q-fever) are well known infections of humans and domestic animals while toxoplasmosis is zoonotic from cats to humans and thus investigated for its infectious potential in this study. Brucella abortus and B. melitensis have been reported in South Africa, first in small ruminants and later in cattle as well as humans since the turn of the century. Similar to brucellosis, humans are infected with Q-fever through contact with infected animals which may be asymptomatic. Their secretions result in occupational public health exposure potential for humans in contact with animals such as abattoir workers, animal handlers and veterinarians. Toxoplasma gondii is a ubiquitous protozoan parasite of warm-blooded animals. The organism causes infection in humans, wildlife, and domestic animals, including birds, cats, sheep, goats, cattle, and pigs. This study aimed to determine the knowledge, attitudes and practices (KAP) on zoonotic diseases of the abattoir workers at Eastern Cape province; assessing seropositivity of Coxiella burnetii, Toxoplasma gondii and Brucella spp. antibodies in African abattoir workers with meta-analysis; detect antibodies to zoonotic pathogens (C. burnetii, T. gondii and Brucella spp.) and characterize Brucella spp. in livestock slaughtered at these abattoirs using serology, bacteriological and molecular methods; and characterize B. abortus and B. melitensis isolated from cattle, goat and human in South Africa using whole genome sequencing single nucleotide polymorphism (wgSNP) analysis to determine the diversity of isolates from different hosts. Semi-structured questionnaires were administered to the abattoir workers regarding their KAP on zoonotic diseases. Of the 76 respondents who participated in the KAP questionnaire, it was discovered that 18,4%, 19.2% and 47.4% of abattoir workers had knowledge of Q-fever, toxoplasmosis, and brucellosis, respectively. Consumption of undercooked meat was reported by 11,8% while 31,6% of the abattoir workers drank unpasteurized milk. Most abattoir workers (84%) wore PPE, however, some of them explained that the use of PPEs was to protect their clothes from blood stains. Abattoir workers (75,3%) also reported hand injuries which occurred whilst at work. Lack of knowledge regarding micro-organisms and improper use of PPE were identified as important risk factors in the abattoirs. A total of ninety-two abattoir workers with known brucellosis seropositivity were evaluated for C. burnetii using the C. burnetii ELISA IgG and IgM assay. The overall C. burnetii seropositivity was 61.90% (95%Cl: 51.3 – 71.9) in abattoir workers with 61.96% IgG antibodies and 1.09% had IgM and IgG antibodies. The African abattoir worker meta-analysis indicated brucellosis seroprevalence ranging from 1.6-33.5% with two test or more done in 12 African countries, toxoplasmosis seroprevalence detected with different single test ranging from 39.1-84.0% in 8 countries and Q-fever seroprevalence done in 3 countries ranging from 6.5-37.1% which was much lower than the 61.9% observed in abattoir workers in this study. Livestock slaughtered at abattoirs from Eastern Cape Province included a total of 565 animals (280 cattle, 200 sheep and 85 pigs) sampled from 5 abattoirs including both high-throughput and low-throughput. Blood/serum and tissue (kidney, liver, spleen, lymph nodes and tonsils) samples were collected from corresponding animals. The objective of the study included determining the seropositivity and co-infection of infectious/zoonotic pathogens in slaughtered animals. This was achieved by serum screening using Rose Bengal test (RBT) and followed by confirmation for antibodies against smooth Brucella using indirect enzyme-linked immunosorbent assay (iELISA), Compliment Fixation Test (CFT). The Mast® Toxoreagent test and iELISA were used for the detection of antibodies against T. gondii and C. burnetii, respectively. The overall Brucella positivity based on at least two tests using RBT, CFT, iELISA and PCR was 4.3%, 1.0% and 0.0% in cattle, sheep, and pigs respectively. T. gondii seropositivity of 37.9%, 1.5% and 7.1% was observed in cattle, sheep, and pigs, respectively. Coxiella burnetii seropositivity of 26.4%, 15% and 2.4% was observed in cattle, sheep, and pigs, respectively. Co-exposure was detected in cattle for antibodies against C. burnetii and T. gondii (40.54%), Brucella spp. and T. gondii (1.35%), and Brucella spp. and Coxiella burnetii (4.05%). Co-exposure to Brucella spp., Coxiella burnetii and Toxoplasma gondii (4.05%) was detected in cattle. Co-exposure to Brucella spp. and Coxiella burnetii (6.67%) was detected in sheep. The 16S-23S ribosomal DNA interspacer region (ITS) PCR was used for the direct screening of Brucella spp. DNA from the tissues of slaughtered animals. The positivity frequency of 33.57% (94/280) cattle, 14.5% (29/200) sheep and 4.71% (4/85) pigs were observed. Suspect Brucella cultures from tissues were recovered from 43.6% (41/94) cattle, 51.7% (15/29) sheep, and 50% (2/4) pigs. The AMOS-PCR characterised B. abortus in 38/41 cattle,11/15 sheep and 2/2 pig cultures. A mixed infection of B. melitensis and B. abortus was observed in 3/41 cattle and in 4/15 sheep cultures. In cattle, the highest number of isolates were recovered from lymph nodes (33%, 31/94), followed by liver (26.6%, 25/94), while the lowest isolation was recovered from tonsils (10.6%, 10/94). In sheep, the highest number of isolates were recovered from liver and kidney (38%, 11/29), while the lowest isolation was recovered from lymph nodes (27.6%, 8/29). The isolation in pigs was only observed from tonsils (50%, 2/4). Brucella abortus and B. melitensis isolates from humans and animals in South Africa were characterised by whole genome sequencing single nucleotide polymorphism (wgSNP) analysis. The wgSNP analysis of B. abortus isolated from South African cattle showed diversity as well as transmission amongst livestock and humans since the B. melitensis isolated from humans and goats from the same outbreak clustered together. In conclusion, education of abattoir workers is essential as these workers are at risk of zoonotic diseases detected at these abattoirs. Lack of knowledge observed regarding zoonotic diseases, as well as failure to understand the correct use of PPE raises a concern since abattoir workers have high exposure potential to different zoonotic infections. This study reports the serological identification of Brucella spp., C. burnetii and T. gondii infections from apparently healthy slaughtered livestock. Mixed infections of B. abortus and B. melitensis were reported from cattle and sheep tissues that need to be further investigated together with B. melitensis in cattle and sheep as well as B. abortus in pigs. We recommend that training on PPE is done together with awareness of microorganisms to emphasize this unseen treat to workers. Furthermore, education to farmers on zoonotic disease and their control will also help to strengthen the health aspect in both animals and humans as animal health influence human health and the environment. Animals slaughtered at abattoirs provide ideal samples for investigation of serological and molecular detection of zoonotic and infectious pathogens that can be used for surveillance and better understanding of prevalence of these diseases in South Africa.