Nested PCR for specific diagnosis of Taenia solium taeniasis

Abstract

Taeniasis due to Taenia solium is a disease with important public health consequences, since the larval stage is not exclusive to the animal intermediate, the pig, but also infects humans, causing neurocysticercosis. Early diagnosis and treatment of T. solium tapeworm carriers is important to prevent human cysticercosis. Current diagnosis based on microscopic observation of eggs lacks both sensitivity and specificity. In the present study, a nested-PCR assay targeting the Tso31 gene was developed for the specific diagnosis of taeniasis due to T. solium. Initial specificity and sensitivity testing was performed using stored known T. solium-positive and -negative samples. The assay was further analyzed under field conditions by conducting a case-control study of pretreatment stool samples collected from a population in an area of endemicity. Using the archived samples, the assay showed 97% (31/32) sensitivity and 100% (123/123) specificity. Under field conditions, the assay had 100% sensitivity and specificity using microscopy/enzyme-linked immunosorbent assay coproantigen testing as the gold standards. The Tso31 nested PCR described here might be a useful tool for the early diagnosis and prevention of taeniasis/cysticercosis.

FIG. 1.

Tso31 nested-PCR amplification using DNA extracted from different sources. Electrophoresis was performed using 5 μl of amplification product. Lanes 1 and 13, 100-bp ladders; lanes 2 to 8, DNA from a contaminated sample with 100, 50, 20, 10, 5, 2, and 1 T. solium eggs, respectively; lane 9, DNA from a T. solium proglottid; lane 10, DNA from a T. saginata proglottid; lane 11, DNA from a T. solium-positive stool sample; lane 12, DNA from a T. saginata-positive stool sample.

FIG. 2.

Analytical sensitivity of the Tso31 nested PCR. Lanes 1 and 10, 100-bp ladders. DNA extracted from T. solium cysts was spectrophotometrically quantitated and diluted. PCR was carried out using different DNA concentrations as follows; lanes 2 to 9, 10 ng, 1 ng, 100 pg, 10 pg, 1 pg, 100 fg, 10 fg, and 1 fg, respectively.