Abstract
The adult Taenia solium, the pork tapeworm, usually lives as a single worm in the small intestine of humans, its only known definitive host. Mechanisms of genetic variation in T. solium are poorly understood. Using three microsatellite markers previously reported [1], this study explored the genetic variability of T. solium from cysts recovered from experimentally infected pigs. It then explored the genetic epidemiology and transmission in naturally infected pigs and adult tapeworms recovered from human carriers from an endemic rural community in Peru. In an initial study on experimental infection, two groups of three piglets were each infected with proglottids from one of two genetically different tapeworms for each of the microsatellites. After 7 weeks, pigs were slaughtered and necropsy performed. Thirty-six (92.3%) out of 39 cysts originated from one tapeworm, and 27 (100%) out of 27 cysts from the other had exactly the same genotype as the parental tapeworm. This suggests that the microsatellite markers may be a useful tool for studying the transmission of T. solium. In the second study, we analyzed the genetic variation of T. solium in cysts recovered from eight naturally infected pigs, and from adult tapeworms recovered from four human carriers; they showed genetic variability. Four pigs had cysts with only one genotype, and four pigs had cysts with two different genotypes, suggesting that multiple infections of genetically distinct parental tapeworms are possible. Six pigs harbored cysts with a genotype corresponding to one of the identified tapeworms from the human carriers. In the dendrogram, cysts appeared to cluster within the corresponding pigs as well as with the geographical origin, but this association was not statistically significant. We conclude that genotyping of microsatellite size polymorphisms is a potentially important tool to trace the spread of infection and pinpoint sources of infection as pigs spread cysts with a shared parental genotype.
Highlights
Taenia solium is a zoonotic parasite that affects both humans and pigs
We evaluated the genetic variability of the progeny of two individual tapeworms by infecting two groups of three pigs each
In the second study we described the genetic relationships among tapeworms obtained from four carriers and cysts obtained from eight naturally infected pigs in a rural community
Summary
Taenia solium is a zoonotic parasite that affects both humans and pigs. Larval infection in the human brain results in neurocysticercosis, the sole main cause of acquired adult epilepsy in developing countries [2]. Neurocysticercosis is considered a potentially eradicable disease [3], and many efforts to implement interventions to control or eliminate this parasite are currently being explored [4, 5]; there are some aspects of the epidemiology, such as distribution and transmission of the parasite among endemic communities that are still unknown. Understanding the interaction between the parasite, swine host, and humans by observing transmission dynamics and clustering of infection through the use of genotyping can help determine the most cost-effective intervention for the given setting. The genetic variation of T. solium has not yet been fully described, a detailed understanding of T. solium population genetic structure is vital to determining the transmission and other epidemiological features of this disease [6,7,8]. The study of genetic variants may help elucidate the reproduction aspects of the parasite [8]
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