Clustering of Necropsy-Confirmed Porcine Cysticercosis Surrounding Taenia solium Tapeworm Carriers in Peru

Abstract

The pork tapeworm, Taenia solium, is among the leading causes of preventable epilepsy in the world and is common in rural areas of developing countries where sanitation is limited and pigs have access to human feces. Prior studies in rural villages of Peru have observed clusters of T. solium cysticercosis among pigs that live near human tapeworm carriers. Such spatial analyses, however, have been limited by incomplete participation and substandard diagnostic tests. In this study, we evaluated the association between necropsy-confirmed cysticercosis in pigs and their distance to T. solium tapeworm carriers in six villages in northern Peru. A total of six (1.4%) tapeworm carriers were detected using copro-antigen enzyme-linked immunosorbent assay and seven of 10 (70%) pigs belonging to the tapeworm carriers were found with viable cyst infection on necropsy. This was significantly greater than the prevalence of viable cyst infection among pigs living < 500 m (11%) and > 500 m (0.5%) from a tapeworm carrier (P < 0.001 for distance trend). Similar statistically significant prevalence gradients were observed after adjustment for possible confounders and for other pig-level outcomes including infection with > 10 viable cysts, degenerated cyst infection, and serological outcomes. This investigation confirms that porcine cysticercosis clusters strongly around tapeworm carriers in endemic rural regions of northern Peru and supports interventions that target these hotspots.

Figure 1.

Life cycle of Taenia solium (adapted with permission from O’Neal et al.).

Figure 2.

Geographic distribution of humans and pigs in six study villages. The size of the purple (no outline) and green (with outline) circles represents the number of positive pigs at each household (range: 1–20 for seropositive pigs and 1–5 for necropsy-confirmed infected pigs). This figure appears in color at www.ajtmh.org.

Figure 3.

Prevalence and 95% confidence intervals (exact binomial) for pig necropsy outcomes at increasing distances from identified tapeworm carriers. P-values are chi-square tests of trend for distance.

Figure 4.

Prevalence and 95% confidence intervals (exact binomial) for pig serological outcomes at increasing distances from identified tapeworm carriers. P-values are chi-square tests of trend for distance.

Figure 5.

Locations of four of six tapeworm carriers and pigs with viable cyst infection. The remaining two tapeworms carriers in Fernandez did not have nearby pigs. Points are jittered to show all pigs from each household—each small cluster of dots represents pigs from a single household. This figure appears in color at www.ajtmh.org.

Figure 6.

Locations of four of six tapeworm carriers and seropositive (enzyme-linked immunoelectrotransfer blot serology). The remaining two tapeworm carriers in Fernandez did not have nearby pigs. Points are jittered to show all pigs from each household—each small cluster of dots represents pigs from a single household. This figure appears in color at www.ajtmh.org.