Proactive Tethering to Prevent Guinea Worm Infections among Dogs in Chad: An Analysis of the Impacts of Timing and Dog Selection.

Guinea worm, or dracunculiasis, has been targeted for eradication. Since the detection of the disease in animals, particularly domestic dogs in Chad, eradication efforts have become more challenging as animal infections perpetuate the cycle of infection and continue to put humans at risk. A wide range of community-based interventions is used to reduce infections, and the proactive tethering of dogs was introduced in 2020 to aid in the eradication efforts. This approach aims to contain dogs to prevent them from infecting water sources and to minimize exposure to water sources harboring infective Guinea worm larvae. However, tethering guidelines are not uniformly adhered to across communities. We adapted an agent-based simulation model to analyze various proactive tethering scenarios that consider dog selection methods, time of year, and time of day. Tethering 100% of dogs year-round but releasing them for part of the day (e.g., at night) results in 19-24% more infections compared with the full-day tethering of 60% of dogs year-round. Tethering 80% of dogs during the 3 months of peak infectivity, from April to June, results in 5-9% fewer infections than tethering 100% of dogs for 6 months during the dry season, from November to April. Because of the protracted prepatent period of Guinea worm disease (∼10-14 months), the results of interventions are not known until 1 year after they are implemented. Understanding the long-term impacts of tethering decisions when they are made is extremely important for achieving the ultimate goal of Guinea worm eradication.