Effect of National Schistosomiasis Control Programme on Taenia solium taeniosis and porcine cysticercosis in rural communities of Tanzania

Abstract

Taenia solium is found throughout sub-Saharan Africa and co-endemic with schistosomiasis in many regions. Taenia solium leads to taeniosis and neurocysticercosis - the leading cause of preventable epilepsy globally. This study aimed to assess the effects of the National Schistosomiasis Control Programme on prevalence of taeniosis and porcine cysticercosis over a four year period in Tanzania. School-based mass drug administration (MDA) of praziquantel was carried out based on schistosomiasis endemicity. Four human and five porcine cross-sectional surveys were carried out from 2012 to 2015 in Mbozi and Mbeya district in Tanzania. Three rounds of school-based MDA of praziquantel were delivered in Mbozi and two in Mbeya. The prevalence of taeniosis and porcine cysticercosis was estimated annually. Stool samples were collected from humans and prevalence of taeniosis estimated by copro-Ag-ELISA. Blood samples from pigs were collected to estimate cysticercosis prevalence by Ag-ELISA. "Track-and-treat" of taeniosis cases was carried out after each survey. In total 12082 stool samples and 4579 porcine serum samples were collected. Significantly fewer children (≤ 15) from Mbozi were infected throughout the study than children from Mbeya who showed a significant decrease in copro-Ag prevalence after the first treatment only. During the final survey in Mbozi the prevalence of taeniosis in adults (1.8%) was significantly lower (p = 0.031, OR 0.40, CI: 0.17-0.89), compared to baseline (4.1%). The prevalence of porcine cysticercosis (8%) had also dropped significantly (p = 0.002, OR 0.49, CI: 0.32-0.76) in this district compared to baseline (13%), whereas no significant difference was seen in Mbeya compared to baseline. The study suggests that three rounds of MDA targeting schistosomiasis in school-aged children combined with 'track-and-treat' contributed to a reduction in prevalence of T. solium in this population, and also had a spillover effect on adults in treated areas as well as reducing the prevalence of T. solium in the intermediate pig host population. Elimination of T. solium in this area would require a One Health approach.

Keywords: Cysticercosis; Mass drug administration (MDA); Preventive chemotherapy; Taenia solium; Taeniosis.

Fig. 1

Study design covering surveys (S) at month-0 (S0) to month-36 follow-up (S36) from 2012 to 2015 in Mbeya and Mbozi district, Tanzania. “Track-and-treat” was attempted on all taeniosis cases identified during the study period.

Fig. 2

Map of study area, Mbeya and Mbozi district in Tanzania, showing where human stool and porcine blood samples were collected in the period 2012 to 2015.

Fig. 3

Taeniosis prevalence among adult age groups in areas receiving school based MDA in Mbeya and Mbozi district, Tanzania at Feb-Apr 2012 (S0), Jul-Aug 2013 (S12), Jul-Aug 2014 (S24), and Jul-Aug 2015 (S36).

Fig. 4

Porcine cysticercosis prevalence in the two districts Mbozi and Mbeya, Tanzania at Feb-Apr 2012 (S0), Oct-Nov (S3), Jul-Aug 2013 (S12), Jul-Aug 2014 (S24), and Jul-Aug 2015 (S36). Asterisk (*) marks significant difference with baseline (S0) based on logistical regression with *p = 0.01–0.05, **p = 0.001–0.009, and ***p < 0.0001. Error bars depict the 95% binomial confidence intervals based on number of positives and sample size.

Fig. 5

Illustration of the proportional difference in infection of humans and pigs based on prevalence of taeniosis and porcine cysticercosis in Mbozi and Mbeya districts, Tanzania at baseline carried out in Feb-Apr 2012 (S0) and the last follow-up in Jul-Aug 2015 (S36).