New insights in cysticercosis transmission.

Carmen S Arriola,Luis A Gomez-Puerta,Hector H Garcia,Armando E Gonzalez,Maria T Lopez-Urbina,Robert H Gilman,Ana Flisser

doi:10.1371/journal.pntd.0003247

Abstract

Taenia solium infection causes severe neurological disease in humans. Even though infection and exposure to swine cysticercosis is scattered throughout endemic villages, location of the tapeworm only explains some of the nearby infections and is not related to location of seropositive pigs. Other players might be involved in cysticercosis transmission. In this study we hypothesize that pigs that carry nematodes specific to dung beetles are associated with cysticercosis infection and/or exposure. We carried out a cross-sectional study of six villages in an endemic region in northern Peru. We euthanized all pigs (326) in the villages and performed necropsies to diagnose cysticercosis. For each pig, we counted cysticerci; measured anti-cysticercus antibodies; identified intestinal nematodes; tabulated distance to nearest human tapeworm infection; and recorded age, sex, productive stage, and geographic reference. For the purpose of this paper, we defined cysticercosis infection as the presence of at least one cysticercus in pig muscles, and cysticercosis exposure as seropositivity to anti-cysticercus antibodies with the presence of 0–5 cysticerci. Compared to pigs without nematode infections, those pigs infected with the nematode Ascarops strongylina were significantly associated with the presence of cysticerci (OR: 4.30, 95%CI: 1.83–10.09). Similarly, pigs infected with the nematode Physocephalus sexalatus were more likely to have cysticercosis exposure (OR: 2.21, 95%CI: 1.50–3.28). In conclusion, our results suggest that there appears to be a strong positive association between the presence of nematodes and both cysticercosis infection and exposure in pigs. The role of dung beetles in cysticercosis dynamics should be further investigated.

Highlights

Cysticercosis affects humans following the ingestion of Taenia solium eggs, generally by fecal-oral contamination
Pigs acquire cysticercosis when ingesting Taenia solium eggs that have been released into the environment in the feces of a person infected with T. solium
We found an association between helminths, for whom dung beetles act as an intermediate host, and porcine cysticercosis infection and exposure after adjusting for other porcine cysticercosis predictors such as distance to tapeworm carrier and age

Summary

Introduction

Cysticercosis affects humans following the ingestion of Taenia solium eggs, generally by fecal-oral contamination. Cysticerci establish primarily in the central nervous system and is the main cause of epilepsy in adults in endemic areas [1]. In Peru, the prevalence of human cysticercosis is relatively high in endemic areas [2]. The T. solium life cycle requires an intermediate host, the pig, to develop its larvae stage. When humans eat pork contaminated with cysticerci (T. solium larvae), T. solium tapeworms develop in their guts and release eggs via human defecation. T. solium eggs turn into cysticerci when ingested by pigs. The presence of cysticerci in pigs can be observed macroscopically in the muscles as cysticerci are as large as rice grains. They are able to transmit the disease; cysticerci that are not able to transmit the disease are considered degenerated or non-viable cysts [3,4]

Results

Discussion

Conclusion