Elimination ofTaenia soliumTransmission in Northern Peru

Abstract

BACKGROUND Taeniasis and cysticercosis are major causes of seizures and epilepsy. Infection by the causative parasite Taenia solium requires transmission between humans and pigs. The disease is considered to be eradicable, but data on attempts at regional elimination are lacking. We conducted a three-phase control program in Tumbes, Peru, to determine whether regional elimination would be feasible. METHODS We systematically tested and compared elimination strategies to show the feasibility of interrupting the transmission of T. solium infection in a region of highly endemic disease in Peru. In phase 1, we assessed the effectiveness and feasibility of six intervention strategies that involved screening of humans and pigs, antiparasitic treatment, prevention education, and pig replacement in 42 villages. In phase 2, we compared mass treatment with mass screening (each either with or without vaccination of pigs) in 17 villages. In phase 3, we implemented the final strategy of mass treatment of humans along with the mass treatment and vaccination of pigs in the entire rural region of Tumbes (107 villages comprising 81,170 people and 55,638 pigs). The effect of the intervention was measured after phases 2 and 3 with the use of detailed necropsy to detect pigs with live, nondegenerated cysts capable of causing new infection. The necropsy sampling was weighted in that we preferentially included more samples from seropositive pigs than from seronegative pigs. RESULTS Only two of the strategies implemented in phase 1 resulted in limited control over the transmission of T. solium infection, which highlighted the need to intensify the subsequent strategies. After the strategies in phase 2 were implemented, no cyst that was capable of further transmission of T. solium infection was found among 658 sampled pigs. One year later, without further intervention, 7 of 310 sampled pigs had live, nondegenerated cysts, but no infected pig was found in 11 of 17 villages, including all the villages in which mass antiparasitic treatment plus vaccination was implemented. After the final strategy was implemented in phase 3, a total of 3 of 342 pigs had live, nondegenerated cysts, but no infected pig was found in 105 of 107 villages. CONCLUSIONS We showed that the transmission of T. solium infection was interrupted on a regional scale in a highly endemic region in Peru. (Funded by the Bill and Melinda Gates Foundation and others.)

The primary prevention of epilepsy: A report of the Prevention Task Force of the International League Against Epilepsy

“…The proportion of cases of epilepsy attributed to NCC was reduced from 37% among those diagnosed before the intervention to 14% among those diagnosed following the intervention ( P = .02) . More recently a study in Peru has demonstrated a significant reduction in Taenia cysts in pigs, but there has been insufficient time to demonstrate a reduction in epilepsy . In Africa, community‐directed ivermectin programs have significantly reduced transmission of O. volvulus by black flies, but none has examined the impact on epilepsy incidence or prevalence.…”

Human taeniasis: current insights into prevention and management strategies in endemic countries

“…More recently, The Bill & Melinda Gates Foundation has sponsored a large-scale trial of strategies aimed at eliminating T. solium from a large area of rural Peru. The recently reported results indicated that human MDA (2 g nicolsamide, three rounds per annum) administered in combination with porcine vaccination (TSOL18) and anthelmintic treatment (oxfendazole 30 mg/kg) successfully eliminated T. solium from the porcine intermediate host in 105 of 107 intervention villages, with elimination sustained for at least 1 year post-intervention 123. Recently in southeast Asia, porcine vaccination (TSOL18) and anthelmintic treatment (oxfendazole 30 mg/kg) have been combined with a human MDA program (two rounds triple-dose albendazole 400 mg) in Lao PDR, where an initial rapid reduction in human taeniasis prevalence was sustained over the 2 years of the study 49,54…”

Assessing Ultrasonography as a Diagnostic Tool for Porcine Cysticercosis

“…While this study confirmed the ability of ultrasound to diagnose larval cysts in live pigs, only a small number of heavily infected animals were examined. Given that the vast majority of infected pigs have only a few cysts in the entire body [12–14], the utility of ultrasonography as an adequate screening tool for food safety purposes or for monitoring progress of control programs is doubtful. However, ultrasonography could prove useful for applications in which detection of heavily infected pigs is the goal.…”

“…In a small Zambian study, researchers found that 35% of pigs with 100 or more cysts (compared to 0% of pigs with <100 cysts) were positively identified through tongue examination [19]. While more research is needed to confirm this hypothesis, it is likely that the sensitivity of tongue examination increases at even heavier cyst burdens, which can range into the thousands of cysts [12–14]. This makes it a reasonable tool for ring-strategy, which aims to identify only the most heavily infected pigs in a community.…”