Prevalence of cysticercosis in cattle and pigs slaughtered in Gauteng abattoirs, South Africa

Abstract

Taenia saginata and Taenia solium are cestodes causing cysticercosis in cattle and pigs respectively. These zoonotic cestodes are of high medical and veterinary importance due to their impact on public health particularly in developing countries. Abattoirs are currently being used for surveillance of animal diseases through meat inspection in South Africa. Although this method has low sensitivity and is subjective, it is currently the standard method used for diagnosis of cysticercosis. The aim of this study was therefore to determine the prevalence of bovine and porcine cysticercosis in Gauteng abattoirs through both retrospective (review of records) and cross-sectional (sampling of animals at selected abattoirs) methods between 2017 and 2018, using serological assay (AgELISA) and molecular assay (conventional PCR) performed on pooled tissues collected from predilection sites (the masseter muscles, tongue, heart and diaphragm). A review of the 5-year (2013 – 2017) archived records on the occurrence of cysticercosis, based meat inspection in Gauteng abattoirs, revealed prevalence 0.0037% and 0.0008% for bovine and porcine cysticercosis, respectively. The prevalence of cysticercosis in cattle and pigs in the cross-sectional study by meat inspection was 0.0% in both cattle (0/351) and pigs (0/107). The apDIA AgELISA, determined the sero-prevalence of bovine and porcine cysticercosis to be 3.40% and 2.80% respectively. The difference was not statistically significant (P=0.778). Of the four risk factors (sex, breed, throughput and district) for cysticercosis investigated, statistically significant differences were detected for only sex and breed of animals. The seroprevalence of bovine cysticercosis was significantly (P=0.02) higher in heifers, 7.3% (6/82) than in bulls, 2.0% (5/249); however, the seroprevalence of porcine cysticercosis was not statistically significantly (P=0.421) different between sows, 4.3% (2/47) and boars, 1.7 (1/60). Nguni breed of cattle had a statistically significantly (P=0.003) higher seroprevalence of cysticercosis, 11.3% (5/44) than either the Jersey breed, 4.4% (2/45) or Bonsmara breed, 1.7% (4/241). All 458 pooled tissues from predilection sites of cattle and pigs did not contain cysts and therefore tested negative on T. saginata and T. solium DNA. The low prevalence detected from the review of 5-year records, and the very low seroprevalence of bovine and porcine cystiscercosis indicate that the risk of cysticercosis to consumers of beef and pork products from the abattoirs sampled in Gauteng province is low. Furthermore, the failure of conventional PCR to detect the DNA of the pathogens from predilection sites of slaughter cattle and pigs confirms that PCR can only be used as a confirmatory tool not a diagnostic tool for taeniid species identification in cattle and pigs.