Status of research on two parasitic zoonoses (Toxoplasmosis and toxocariasis) in Sub-Saharan Africa and their prevalence in selected rural communities of Kwazulu-Natal Province of South Africa using free-range chickens as a case study.

Abstract

Free-range chickens are among the popular livestock that are owned by most households in rural communities. They constitute a major source of food security, financial income, and are used in socio-cultural practices. However, due to their habit of scavenging for food they are exposed to parasitic agents thereby making them host for several disease pathogens such as Toxoplasma gondii and Toxocara spp. Toxoplasma gondii and Toxocara spp are the etiological agents of human toxoplasmosis and human toxocariasis respectively. Humans become directly infected via accidental ingestion of sporulated oocysts of T. gondii from felids and tachizoites/bradyzoites of T. gondii from raw/undercooked meat or embryonated eggs with second stage larva of Toxocara spp via contact with contaminated faeces of definitive hosts (dogs and cats), or indirectly via ingestion of contaminated water or consumption of raw or undercooked chickens. Following infection, the parasites migrate through the human body causing varying degree of diseases known as toxoplasmosis and toxocariosis respectively. Consumption of poultry meat viscera is an increasing dietary habit common in different communities worldwide and depending on socio-cultural preferences it can either be eaten raw, undercooked, or well cooked. However, the habit of eating raw/under cooked meat or viscera poses the risk of transmitting T. gondii and Toxocara spp from animals to humans. Limited information exist on the epidemiology of T. gondii and Toxocara spp in sub-Saharan Africa and let alone the role of free-range chickens in the transmission of these zoonotic parasites, hence, this study was designed to: ➢ review the status of research on these two parasitic zoonoses in sub-Saharan Africa. ➢ determine prevalence of the parasites in free-range chickens from selected rural communities in KwaZulu-Natal province through molecular approach. determine the level of awareness of the zoonotic transmission of these parasites when the viscera or meat of Free-range chicken are consumed raw or undercooked. A sytematic review and meta-analysis was conducted following the Preferred Reporting items for systematic Reviews and Meta-Analysis (PRISMA) guidelines on the epidemiology of T. gondii in animals and humans in southern Africa and epidemiology of Toxocara spp in canine, feline, and humans in sub-Saharan Africa respectively. The reviews showed that there is paucity of information on T. gondii and Toxocara spp in food animals including free-range chickens.

Furthermore, to determine the prevalence of T. gondii and Toxocara spp in free-range chickens, free-range chickens were randomly purchased from selected rural communities namely, Gingindlovu (GI), Ozwathini (O), uMzinto (MZ), and Shonwgweni (SH) in KwaZulu-Natal (KZN). The chickens were euthanized according to ethical guidelines. The brain tissue of each chicken was divided into two equal halves. One half was examined for the presence of parasites while the remaining half was preserved in 70% alcohol for molecular analysis. To detect the presence of T. gondii, the preserved brain tissues were subjected to molecular analysis based on analysis of DNA sequences of the nuclear ribosomal internal transcribed spacer (ITS-1 and ITS-2) region using TOX4 and TOX5 primers. To detect the presence of Toxocara spp, various parts of chickens such as brain, heart, liver, spleen, kidney, duodenum, pectoral, thigh, and breast were digested using the acid/pepsin; 1:1 method and the larvae were recovered with 20-μm sieve. Three (3) larvae were recovered from the right pectoral from a chicken collected in GI; two (2) from the lungs of a chicken from MZ; three (3) each in the liver and left thigh of two separate chickens from SH. The recovered larvae were subjected to molecular analysis using Nem_18S primers. Toxoplasma gondii was not detected in the tissue samples which were subjected to molecular analysis, however, Toxocara canis was identified in Gingindlovu (n=1), uMzinto (n=1), and Shongweni (n=2). The identified T. canis showed 100% homology with Genbank isolates from China, the United Kingdom, and the United State of America. The occurrence of T. canis in free-range chickens from KZN province reveals the possibility of human toxocariasis transmission in the province. Moreover, we conducted a questionnaire survey to determine the knowledge and practices relating to consumption of free-range chicken viscera in selected rural communities of KwaZulu-Natal with respect to zoonotic transmission of T. gondii and Toxocara spp. There was low level of awareness of risk of zoonotic transmission of the parasites via ingestion of raw/undercooked free-range chicken meat/viscera and the majority of respondents consumed free-range chicken viscera. They preferred the viscera well cooked which reduces the risk of transmission of the the two parasites. The study contributes new knowledge on the prevalence of zoonotic parasites in free-range chickens as well as the level of knowledge and awareness on zoonosis transmission via consumption raw/undercooked free-range chicken viscera or meat.