A search for tiny dragons (Dracunculus medinensis third-stage larvae) in aquatic animals in Chad, Africa

Scientific Reports

Corresponding authors: Christopher A. Cleveland, ccleve@uga.edu and Michael J Yabsley, myabsley@uga.edu

Summary author: Leah Crone, lec62627@uga.edu

Since 2012 The Republic of Chad has reported an increase of Guinea worm infections in dogs, cats, and baboons. While humans become infected through drinking from a contaminated water source differing infection patterns in dogs and cats have caused scientists to suspect an alternate form of transmission. This is supported by the increase of guinea worm infection in dogs and cats while human cases have greatly decreased since 1986.  Frogs and fish are believed to be short term hosts of Guinea worm, which may explain increased incidence in cats and dogs. A group of scientists including, CEID member Alec Thompson, studied the possibility of aquatic animals’ role as host to Guinea worm and how that impacts increasing infections in cats and dogs. They specifically looked at the presence of infectious larvae within aquatic animals which may be fed to cats and dogs, or found in nearby ponds that dogs and cats might feed from.

No Guinea worm larvae were found in the 234 fish, 2 turtles and 2 lizards surveyed. They did find 7 Guinea worm larvae in different frog species, 2 of which are eaten by humans, suggesting that frogs may be a paratenic (intermediate) host partially responsible for the increased cases in cats and dogs. However, when questioned, the locals said they cook the frogs thoroughly and do not consume them raw, and they do not feed the frogs to their dogs because of the possibility they might become ill, challenging this conclusion. While evidence of fish infection was not found in this study, separate research from lead author Christopher Cleveland suggests that fish consume infected copepods, creating short term hosts. Thus, there is a risk of infection for dogs and cats feeding on fish intestines. While this study brings to light new information on Guinea worm transmission through frogs, the significance is unknown. More research is needed to continue exploring alternative transmission methods.

Cleveland, C.A. et al. (2019). A search for tiny dragons (Dracunculus medinensis third-stage larvae) in aquatic animals in Chad, Africa. Scientific Reports. 9(375). https://doi.org/10.1038/s41598-018-37567-7