Dogs Key Impediment to Eradicating Guinea Worm Disease

Just as eradication of Guinea worm disease appeared imminent, it emerged that domestic dogs also harbor the parasite.

Guinea worm disease is usually caught by drinking water containing water fleas that carry the parasite larvae. The worms mate and grow inside the body, and after 10-14 months the one-meter-long adult worm emerges, usually from the arms or legs, to shed its larvae back into water. The parasite causes disability and trauma in some of the world’s poorest communities in Chad, Ethiopia, Mali and South Sudan.

Targeted surveillance showed that in 2020, 93% of Guinea worms detected worldwide were in dogs in Chad. Research by the University of Exeter, published today in Current Biology, has revealed a new pathway for transmission: by dogs eating fish that carry the parasite larvae. This means dogs maintain the parasite’s life-cycle and humans can still catch the disease.

The researchers worked for a year in several of the worst-affected villages along the River Chari in Chad. They tracked hundreds of dogs with satellite tags to analyze movements, and revealed dog diets throughout the year using forensic stable isotope analysis of dog whiskers. Much of the fish eaten by the dogs,  usually guts or smaller fish,  was discarded by humans fishing on the river and its lagoons.

According to study leader Robbie McDonald of the University of Exeter, "Our work shows that fisheries, and the facilitation of dogs eating fish, are likely contributing to the persistence of Guinea worm in Chad. The challenge now is that this pathogen must be eliminated not only from people but also from animals.”