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Background Taenia solium inflicts substantial neurologic disease and economic losses on rural communities in many developing nations. “Ring-strategy” is a control intervention that targets treatment of humans and pigs among clusters of households (rings) that surround pigs heavily infected with cysticerci. These pigs are typically identified by examining the animal’s tongue for cysts. However, as prevalence decreases in intervened communities, more sensitive methods may be needed to identify these animals and to maintain control pressure. The purpose of this study was to evaluate ultrasonography as an alternative method to detect pigs heavily infected with T. solium cysts. Methodology/Principal Findings We purchased 152 pigs representing all seropositive animals villagers were willing to sell from eight communities (pop. 2085) in Piura, Peru, where T. solium is endemic. Tongue and ultrasound examinations of the fore and hind-limbs were performed in these animals, followed by necropsy with fine dissection as gold standard to determine cyst burden. We compared the sensitivity and specificity of ultrasonography with tongue examination for their ability to detect heavy infection (≥ 100 viable cysts) in pigs. Compared to tongue examination, ultrasonography was more sensitive (100% vs. 91%) but less specific (90% vs. 98%), although these differences were not statistically significant. The greater sensitivity of ultrasound resulted in detection of one additional heavily infected pig compared to tongue examination (11/11 vs. 10/11), but resulted in more false positives (14/141 vs. 3/141) due to poor specificity. Conclusions/Significance Ultrasonography was highly sensitive in detecting heavily infected pigs and may identify more rings for screening or treatment compared to tongue examination. However, the high false positive rate using ultrasound would result in substantial unnecessary treatment. If specificity can be improved with greater operator experience, ultrasonography may benefit ring interventions where control efforts have stalled due to inadequate sensitivity of tongue examination., Author Summary Taenia solium is a cestode that infects humans and pigs. The parasite causes up to one-third of epilepsy in Latin America, Asia and Africa and results in economic harm to smallholder farmers who cannot sell the contaminated pork of their infected pigs. “Ring-strategy” is an intervention being evaluated as a potential method to control the spread of infection within communities. This strategy involves identifying heavily infected pigs and targeting treatment resources to humans and pigs living nearby these animals. Tongue examination of pigs is used to provide a simple yet crude technique for identifying the most heavily infected pigs. The purpose of this study was to evaluate the ability of ultrasonography to identify T. solium infection in pigs and to compare it to traditional tongue examination methods. We found that ultrasonography may be better at detecting heavily infected pigs than traditional tongue examination methods, but has limitations such as increased cost and a high false positive rate. With improvements in training and greater operator experience, ultrasound may have the potential to contribute to control interventions based on ring-strategy.

Background Taenia solium, a parasite that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. Geographic hotspots of pigs testing positive for serologic markers of T. solium exposure have been observed surrounding the locations of human tapeworm carriers. This clustered pattern of seropositivity in endemic areas formed the basis for geographically targeted control interventions, which have been effective at reducing transmission. In this study, we further explore the spatial relationship between human tapeworm carriers and infected pigs using necroscopic examination as a quantitative gold-standard diagnostic to detect viable T. solium cyst infection in pigs. Methodology/Principal findings We performed necroscopic examinations on pigs from 7 villages in northern Peru to determine the number of viable T. solium cysts in each pig. Participating humans in the study villages were tested for T. solium tapeworm infection (i.e., taeniasis) with an ELISA coproantigen assay, and the distances from each pig to its nearest human tapeworm carrier were calculated. We assessed the relationship between proximity to a tapeworm carrier and the prevalence of light, moderate, and heavy cyst burden in pigs. The prevalence of pig infection was greatest within 50 meters of a tapeworm carrier and decreased monotonically as distance increased. Pigs living less than 50 meters from a human tapeworm carrier were 4.6 times more likely to be infected with at least one cyst than more distant pigs. Heavier cyst burdens, however, were not more strongly associated with proximity to tapeworm carriers than light cyst burdens. Conclusion/Significance Our study shows that human tapeworm carriers and pigs with viable T. solium cyst infection are geographically correlated in endemic areas. This finding supports control strategies that treat humans and pigs based on their proximity to other infected individuals. We did not, however, find sufficient evidence that heavier cyst burdens in pigs would serve as improved targets for geographically focused control interventions., Author summary Taenia solium, the pork tapeworm, is a parasite transmitted between humans and pigs. The disease is most common in developing countries where access to sanitation is limited and domestic pigs are allowed to roam freely. Humans infected with the intestinal tapeworm release T. solium eggs into the environment when they defecate outside, and pigs become infected with the larval stage of the disease, cysticercosis, upon consuming these eggs in human feces. Prior work using serologic testing of pigs has shown that proximity to human tapeworm carriers is a possible risk factor for porcine cysticercosis. Our study investigated if proximity to human tapeworm carriers was associated with established cyst infection in pigs, and if proximity to tapeworm carriers also increased the degree of cyst infection in pigs (i.e., the number of T. solium cysts a pig was infected with). The results confirmed that human tapeworm carriers and infected pigs are geographically correlated, but did not uncover a stronger relationship for heavily infected pigs. It is important to continue to investigate this spatial relationship as some control strategies rely on the assumption that human tapeworm carriers will be found in close proximity to heavily infected pigs. Future control strategies would benefit from a precise knowledge of the degree of pig infection that best predicts for nearby tapeworm carriers.

Community-based ecosystem management (CBEM) in the United States is closely tied to global processes. Increasing and shifting international market demands for ecosystem products and services together with global trends in climate change and biodiversity loss have tangible impacts in communities in every region of the country. Meanwhile, community-based natural resource management efforts in other parts of the world, particularly in developing countries, have a longer history than in the United States. This history, and the tools and techniques developed elsewhere for community-based resource management, can help to inform North American advocates and practitioners of CBEM. This paper has four objectives. The first is to identify key global trends that affect communities in the United States. These trends include demand and supply relationships (especially of forest resources) and environmental changes that will shape economic and policy choices in coming decades. Second, the paper examines counte...