Prevalence and risk assessment of toxoplasmosis in commercial and communal sheep and goats in the North West province and occurrence in the Free State province

Abstract

Toxoplasmosis is one of the most widespread parasitic zoonotic diseases arising from Toxoplasma gondii infection. This disease significant impact on sheep and goat production; however, it sometimes goes unnoticed in the herd, leading to unexpected and inexplicable abortions and death among the new-born’s deaths. This study aimed to determine the prevalence and risk factors of T. gondii infections in sheep and goats from commercial and communal farms in the North West, as well as its occurrence in the Free State province. Additionally, we analysed variations and phylogenetic relationships in the T. gondii B1 and GRA6 gene sequences from isolates deposited in GenBank (https://www.ncbi.nlm.nih.gov/) to evaluate the usefulness of the two genes as phylogenetic markers. Toxoplasma gondii IgG antibodies and DNA were analysed in blood samples from 439 animals (164 sheep and 285 goats), vaginal swabs, milk, sheath scrapes from the North West province, and 11 diagnostic tissue samples from the Free State province. A questionnaire was administered to farmers used to assess potential risk factors associated with animals’ exposure to T. gondii infections. Additionally, 183 gene sequences (107 B1 and 83 GRA6 gene sequences) retrieved from GenBank from different animal species originating from different countries were analysed, and single nucleotide polymorphisms (SNP’s) were present in 17% and 83%, of the B1 and GRA6 gene sequences, respectively. Of the 439 sera tested, 13.9% (95% CI: 0.00-1.00%) were positive for antibodies against T. gondii. It was discovered that sheep and goats had seroprevalences of 19.5% and 10.5%, respectively. T. gondii was not detected by PCR in any of the analysed samples (n=198). Using the Chi-Squared test or odds ratio, the main risk factors associated with T. gondii infections were breed, gender, species, animal origin, history of abortion, disposal of aborted material, disposal of manure, type of breeding, district, municipality, feeding system, feed storage, and presence of cats on farms. The high seroprevalence in this study suggests that T. gondii exposure is widespread within the farms. The absence of genetic material associated with T. gondii by PCR even in seropositive animals suggests the animals were at some point exposed to the pathogen, but they do not shed the parasite in their reproductive tissues. Perhaps, these animals may potentially shed the pathogen in other tissues that we did not analyse. The isolates' gene sequence analysis showed that the GRA6 gene could work as a genetic marker for T. gondii in population studies compared to the B1 gene. To effectively prevent and control exposure to T. gondii infections, the identified risk factors must be considered.