Abstract
Dracunculus medinensis, or human Guinea worm (GW), causes a painful and debilitating infection. The global Guinea Worm Eradication Program (GWEP) has successfully reduced human GW cases from 3.5 million in 21 countries in 1986 to only 30 cases in three remaining countries in 2017. Since 2012, an increase in GW infections in domestic dogs, cats and baboons has been reported. Because these infections have not followed classical GW epidemiological patterns resulting from water-borne transmission, it has been hypothesized that transmission occurs via a paratenic host. Thus, we investigated the potential of aquatic animals to serve as paratenic hosts for D. medinensis in Chad, Africa. During three rainy and two dry season trips we detected no GW larvae in 234 fish, two reptiles and two turtles; however, seven GW larvae were recovered from 4 (1.4%) of 276 adult frogs. These data suggest GW infections may occur from ingestion of frogs but the importance of this route is unknown. Additional studies are needed, especially for other possible routes (e.g., ingestion of fish intestines that were recently shown to be a risk). Significantly, 150 years after the life cycle of D. medinensis was described, our data highlights important gaps in the knowledge of GW ecology.
Highlights
The global Guinea Worm Eradication Program (GWEP) has successfully reduced human Guinea worm (GW) cases from 3.5 million in 21 countries in 1986 to only 30 cases in three remaining countries in 2017
Annual increases of GW infections since 2012 among domestic dogs and more recently cats, and the absence of classical water-borne outbreaks of Guinea Worm Disease (GWD) among humans led to the hypothesis that transmission was not occurring via the classical route of ingesting water containing copepods infected with L3s
It was posited that a paratenic host may be involved and that domestic animals were being infected via consumption of undercooked flesh or viscera of aquatic animals[3]
Summary
The global Guinea Worm Eradication Program (GWEP) has successfully reduced human GW cases from 3.5 million in 21 countries in 1986 to only 30 cases in three remaining countries in 2017. During three rainy and two dry season trips we detected no GW larvae in 234 fish, two reptiles and two turtles; seven GW larvae were recovered from 4 (1.4%) of 276 adult frogs These data suggest GW infections may occur from ingestion of frogs but the importance of this route is unknown. In Chad, infections in dogs, and more recently, cats, have been recorded[2] These infections do not typically follow the classic epidemiology of GWD in humans wherein infection occurs from drinking water containing infected copepods. The result of such transmission typically results in a clustering of cases nearby a single water source, which has not been observed in dog or cat cases. While it is still possible that animals may become infected via ingestion of infected copepods in water, an alternate route was hypothesized; fish or frogs may be playing a role in transmission of D. medinensis[3]
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