Seroprevalence of circulating taeniid antigens in pigs and associated risk factors in Kongwa district, Tanzania

Abstract

The aim of this study was to investigate exposure to porcine cysticercosis (PC) and associated risk factors in the Kongwa District, eastern-central Tanzania. For the first time a cross-sectional investigation of the seroprevalence in pigs using a commercial genus specific cysticercosis enzyme linked immunosorbent assay (apDia Ag-ELISA) was undertaken in eastern-central Tanzania. Moreover, the identity of suspected T. solium cysts from pigs in the study area were confirmed by sequencing parasites’ mitochondrial cox1 gene. Structured questionnaires and direct observations were used to investigate risk factors associated with parasite transmission. A total of 102 pig-keeping households were surveyed during the dry season between July and August 2017 and 126 households in the rainy season between March and April 2018. Of the 447 examined pigs, 77 (17%, 95% C.I. 14%–20%) tested positive in the ELISA. Seroprevalence was higher in pigs examined during the rainy (21%, 95% C.I. 16%–26%) than dry (12%, 95% C.I. 7%–17%) season (p = 0.019). Eight cyst-positive-pigs were confirmed to be infected with T. solium by sequencing. Risk factors associated with PC seropositivity included origin of piglets or pigs (OR = 0.27, 95% C.I. 0.13–0.42, p = 0.001), socioeconomic factors and pig production system (OR = 0.22, 95% C.I. 0.07–0.37, p = 0.005) and sanitation and hygiene practices (OR = 0.19, 95% C.I. 0.04–0.34, p = 0.014). This study has recorded a high Taenia spp. seroprevalence in pigs in Kongwa suggesting the presence of people in the community carrying the adult parasite, Taenia solium. Our findings also suggest risk of infection by T. solium to people in urban centres and cities consuming pigs from rural areas in Kongwa. The high seroprevalence in Kongwa calls for further studies on taeniasis and cysticercosis in the human population in order to determine suitable control strategies.

Soil contamination by Taenia solium egg DNA in rural villages in Kongwa district, Tanzania

“…In a previous study, a high prevalence of taeniid antigens was recorded in pigs from the same villages in Kongwa [5], suggesting environmental contamination with T. solium eggs. This finding is not supported by the results presented herein.…”

“…Parasite egg DNA was detected in areas around the toilet, waste disposal site and outside the house. Although research has been carried out on porcine and human cysticercosis in Tanzania [2,5,7], researches on soil contamination by T. solium eggs are scarce and none has been empirically examined with ddPCR.…”

“…The optimal annealing temperature for the universal ddPCR assay was set to 54°C [17]. For the ddPCR probe assay, the annealing temperature was determined to be 56°C by a thermal gradient ranging from 50°C to 60°C with 2 µl of template T. solium cysticerci DNA extracted from pigs [5].…”

“…The infection cycle of T. solium is usually associated with poor sanitary and hygiene conditions, free-range pig husbandry and inadequate or lack of meat inspection [5,6]. The prevalence of T. solium infection in Tanzania and elsewhere in Sub-Saharan Africa has been reported to range between 2.0% to 56.7% in pigs and 0.1% to 21.6% in humans [7], where they impact on the economies and nutritional well-being of rural communities.…”

“…In a previous study, we found a 17% seroprevalence rate of cysticercosis in pigs in rural villages of Kongwa district in Tanzania [5]. To improve the understanding of human and porcine cysticercosis infection-risk in more detail, it was decided to investigate the level of soil contamination by T. solium eggs at the village and household levels.…”