GPS Tracking of Free-Ranging Pigs to Evaluate Ring Strategies for the Control of Cysticercosis/Taeniasis in Peru

Background Taenia solium, a parasitic cestode that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. T. solium eggs are released into the environment through the stool of humans infected with an adult intestinal tapeworm (a condition called taeniasis), and cause cysticercosis when ingested by pigs or other humans. A control strategy to intervene within high-risk foci in endemic communities has been proposed as an alternative to mass antihelminthic treatment. In this ring strategy, antihelminthic treatment is targeted to humans and pigs residing within a 100 meter radius of a pig heavily-infected with cysticercosis. Our aim was to describe the roaming ranges of pigs in this region, and to evaluate whether the 100 meter radius rings encompass areas where risk factors for T. solium transmission, such as open human defecation and dense pig activity, are concentrated. Methodology/Principal Findings In this study, we used Global Positioning System (GPS) devices to track pig roaming ranges in two rural villages of northern Peru. We selected 41 pigs from two villages to participate in a 48-hour tracking period. Additionally, we surveyed all households to record the locations of open human defecation areas. We found that pigs spent a median of 82.8% (IQR: 73.5, 94.4) of their time roaming within 100 meters of their homes. The size of home ranges varied significantly by pig age, and 93% of the total time spent interacting with open human defecation areas occurred within 100 meters of pig residences. Conclusions/Significance These results indicate that 100 meter radius rings around heavily-infected pigs adequately capture the average pig’s roaming area (i.e., home range) and represent an area where the great majority of exposure to human feces occurs.
Author Summary Taenia solium, commonly known as the pork tapeworm, is a parasite that affects humans and pigs. It has a disproportionate impact on low and middle income countries, and is most common in rural areas where free-ranging domestic pigs are common, and access to sanitation is limited. Pigs acquire cysticercosis, the larval stage of the disease, when they ingest T. solium eggs that have been released into the environment through the feces of an infected human host. In this study, we tracked free-ranging pigs with GPS devices, and found that most pigs remained close to their owners’ homes throughout the tracking period, and that the majority of pigs’ interactions with open human feces occurred near their owners’ homes. These findings suggest that 100 meter radius rings around heavily-infected pigs capture the most likely area of pig infection, and support focused control interventions in areas surrounding heavily-infected pigs.