Summary by: Kailah Massey
Corresponding Authors: Robert Richards, robert.richards@uga.edu
The Guinea worm parasite, Dracunculus medinensis, is on the verge of eradication – an uncommon feat – but recent outbreaks linked to domestic dogs have presented challenges to eradication efforts. D. medinensis causes dracunculiasis, which, while rarely lethal, can be intensely painful and debilitating to hosts. In the Republic of Chad, D. medinensis infection faced a period of dormancy, with no reported cases between 2000-2009. However, in 2010 there was a small outbreak in cases associated with domesticated dogs. Since then, D. medinensis has continued to affect domestic dogs, and evidence suggests this has fueled the persistence of human infections. As interventions have focused on disrupting transmission in humans, infections in dogs hamper eradication efforts, since infections in dogs can continue the parasite’s life cycle and lead to new infections. Thus, it is imperative to gather more about the factors that influence infection to improve eradication strategies.
Host species become infected with D. medinensis after ingesting tiny crustaceans called copepods, which are infected with D. medinensis larvae. Hosts, including humans and dogs, ingest these copepods by drinking unfiltered water or consuming aquatic animals like fish which can contain infected copepods. The larvae mature within the host and grow into an adult worm over the course of a year. A painful blister develops in the host’s lower extremities, as the worm begins to emerge. If the adult worm emerges in water, it releases larvae to infect new copepods, continuing the life cycle.
To assess anthropogenic and environmental factors that predict infection of D. medinensis in domestic dogs in the Republic of Chad, a team of scientists, including CEID members, Robert Richards, Chris Cleveland, Richard Hall, Vanessa Ezenwa, Andrew Park, and Michael Yabsley used machine learning methods to recognize important characteristics of D. medinensis infection at the village level and spatial clusterings of dog cases regionally. This work was done in collaboration with researchers at the Carter Center in Atlanta, and the Chad Guinea Worm Eradication Program.
The study concluded that the presence of infection at the village level was predicted by various factors specific to the individual village, including climatic, demographic, and geographic factors. These factors differed among villages in northern and southern Chad. In comparison, in a spatial hotspot (areas with significantly more dog infections than would be expected based on the size of the dog population), the infections were influenced by location and climate. Overall, the study identifies various factors that contribute to D. medinensis infection in dogs. This insight can be used to aid researchers in future data collection efforts, as well as to inform and improve eradication programs.
Richards RL, Cleveland CA, Hall RJ, Tchindebet Ouakou P, Park AW, Ruiz-Tiben E, et al. (2020) Identifying correlates of Guinea worm (Dracunculus medinensis) infection in domestic dog populations. PLoS Negl Trop Dis 14(9): e0008620. https://doi.org/10.1371/journal.pntd.0008620
Life cycle image credit to DPDx.