Accurate diagnosis of lesions suspected of being caused by Taenia solium in body organs of pigs with naturally acquired porcine cysticercosis.

Charles G Gauci,Dinesh Kumar Singh,Zachary Nsadha,Meritxell Donadeu,Marshall W Lightowlers,Andrew Stent,Chrisostom Ayebazibwe,Chris Rutebarika,Angela Colston,Ishab Poudel,Keshav Sah,Mar Siles-Lucas

doi:10.1371/journal.pntd.0007408

Abstract

The definitive method for diagnosis of porcine cysticercosis is the detection of cysticerci at necropsy. Cysts are typically located in the striated muscle and brain. Until recently Taenia solium cysticerci have not been definitively identified in other tissue locations, despite several comprehensive investigations having been undertaken which included investigation of body organs other than muscle and brain. Recently a study conducted in Zambia reported 27% infection with T. solium in the liver of pigs with naturally acquired porcine cysticercosis, as well as some T. solium infection in the lungs and spleen of some animals. We investigated the cause of lesions in sites other than the muscle or brain in a total of 157 pigs from T. solium endemic regions of Uganda and Nepal which were subjected to extensive investigations at necropsy. Lesions which had the potential to be caused by T. solium were characterised by macroscopic and microscopic examination, histology as well as DNA characterisation by PCR-RFLP and sequencing. Lesions were confirmed as being caused by Taenia hydatigena (both viable and non-viable), by T. asiatica and Echinococcus granulosus (in Nepal) and nematode infections. No T. solium-related lesions or cysticerci were identified in any tissue other than muscle and brain. It is recommended that future evaluations of porcine cysticercosis in aberrant tissue locations include DNA analyses that take appropriate care to avoid the possibility of contamination of tissue specimens with DNA from a different tissue location or a different animal. The use of appropriate control samples to confirm the absence of cross-sample contamination is also recommended.

Highlights

Taenia solium is a cestode parasite which is an important cause of human morbidity and mortality, in many developing countries where sanitary conditions and pig rearing practices favour the parasite’s transmission
An investigation of porcine cysticercosis carried out in Zambia described 27% of infected pigs as having T. solium cysts in the liver, as well some animals having cysts in other unusual tissues locations
We collected lesions from the tissues of pigs derived from T. solium endemic areas in Uganda and Nepal

Summary

Introduction

Taenia solium is a cestode parasite which is an important cause of human morbidity and mortality, in many developing countries where sanitary conditions and pig rearing practices favour the parasite’s transmission. T. solium is a zoonotic parasite with pigs acting almost exclusively as the intermediate host responsible for transmission. Completion of the parasite’s life cycle has been prevented in many developed countries through improvements in sanitation and hygienic pig rearing practices, which prevent the animals from being exposed to human faeces. Similar improvements in developing countries where T. solium is currently endemic would be expected to reduce the incidence of human cysticercosis. Large areas of Africa, Asia and Latin America where T. solium is endemic remain economically disadvantaged, presenting a substantial hindrance to implementation of control programs. New tools have become available for prevention or treatment of porcine cysticercosis [3], and the existence of these tools has encouraged an increasing number of efforts to evaluate different control strategies

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