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Dogs and Guinea worm eradication

Thursday, 19th of January 2017

The Lancet Infectious Diseases

Volume 16, No. 11, p1225–1226, November 2016

Correspondence

Dogs and Guinea worm eradication

Mark L Eberhard,

Ernesto Ruiz-Tiben,

Donald R Hopkins

Published: November 2016

© 2016 Elsevier Ltd. All rights reserved.

Teresa Galán-Puchades, in her Correspondence on dogs and Guinea worm eradication,1x1Galán-Puchades, MT. Dogs and Guinea worm eradication. Lancet Infect Dis. 2016; 16: 7701

noted several critical points about the Guinea Worm Eradication Program (GWEP) in Chad. We would like to clarify several of the issues.

Dog infections have been addressed programmatically in Chad for the past 4 and a half years. The situation in Chad is different from previous reports of sporadic Guinea worm infections in dogs. What is not made clear by Galán-Puchade is that human Guinea worm has infected dogs occasionally, but when eliminated from the human population, dog infections disappear.2x2Muller, R. Dracunculus and dracunculiasis. Adv Parasitol. 1971; 9: 73–151 , 3x3Cairncross, S, Muller, R, and Zagaria, N. Dracunculiasis (Guinea worm disease) and the eradication initiative. Clin Micro Rev. 2002; 15: 223–246

 (59) By contrast, in Chad, dog infections are probably responsible for the small number of cases in human beings.4x4Eberhard, ML, Ruiz-Tiben, E, Hopkins, DR et al. The peculiar epidemiology of dracunculiasis in Chad. Am J Trop Med Hyg. 2014; 90: 61–70

 (18)4 We expect human infections in Chad to stop once transmission of Guinea worms among dogs is interrupted. Lastly, all evidence suggests transmission is not occurring via common drinking water sources, but via a paratenic aquatic host that people and dogs are eating raw or only partly cooked.4x4Eberhard, ML, Ruiz-Tiben, E, Hopkins, DR et al. The peculiar epidemiology of dracunculiasis in Chad. Am J Trop Med Hyg. 2014; 90: 61–70

 (18)4

Previous laboratory studies have shown that dogs (and cats and monkeys) are good experimental hosts for Dracunculus medinensis.5x5Moorthy, VN and Sweet, WC. Further notes on the experimental infection of dogs with dracontiasis. Am J Hyg. 1938; 27: 301

, 6x6Muller, R. Experimental dracontiasis in animals. Parasitology. 1968; 58: 7–8

 Hence, the ease with which this infection was established in dogs is not surprising.

The reward paid to dog owners probably has a key role in dog infections being reported by owners, which is exactly what was hoped for. However, the increase in dog infection rates has resulted from active surveillance undertaken in larger and larger areas within Chad by the GWEP.

Residents of endemic villages have been interviewed to learn what is known about Guinea worm disease. Discussions have also been held with former officials of Chads GWEP from 1993–98 to gain some insight and perspective on the matter. None of these reliable sources ever encountered a Guinea worm infection in a dog during years of working in endemic areas when hundreds of cases in human beings were being reported.4x4Eberhard, ML, Ruiz-Tiben, E, Hopkins, DR et al. The peculiar epidemiology of dracunculiasis in Chad. Am J Trop Med Hyg. 2014; 90: 61–70

Crossref | PubMed | Scopus (18)4

We recently showed that tadpoles were readily infected with D medinensis and harboured larvae that were infectious to ferrets.7x7Eberhard, ML, Yablsey, MJ, Zirimwabagabo, H et al. Possible role of fish and frogs as paratenic hosts of Dracunculus medinensis Chad. Emerg Inf Dis. 2016; 22: 1428–1430

Crossref7 Tadpoles have been shown to harbour those larvae into the adult frog stage, and that these larvae were infective in mammalian definitive hosts.8x8CrichtonVFJ and Beverley-Burton, M. Observations on the seasonal prevalence, pathology and transmission of Dracunculus insignis (Nematoda: Dracunculoidea) in the raccoon, Procyon lotor in Ontario. J Wildl Dis. 1977; 13: 273–280

Crossref, 9x9Eberhard, ML and Brandt, FH. The role of tadpoles and frogs as paratenic hosts in the life cycle of Dracunculus insignis (Nematoda: Dracunculoidea). J Parasitol. 1995; 81: 792–793

Crossref | Scopus (11) We recently discovered the occurrence of a D medinensis larva in a wild-caught frog in Chad.10x10Eberhard, ML, Cleveland, CA, Zirimwabagabo, H, Yabsley, MJ, Ouakou, PT, and Ruiz-Tiben, E. Guinea worm (Dracunculus medinensis) infection in a wild-caught frog, Chad. Emerg Infect Dis. 2016; DOI: http://dx.doi.org/10.3201/eid2211.161332 (published online Nov 15.)

Crossref10

In Chad, most water bodies are too large to treat with chemical larvicide, so it is applied to cordoned areas suspected of being contaminated, thus preventing new infections in the following year.

D medinensis from dogs and human beings in Chad are genetically indistinguishable, hence interventions in place now and in the near future aim to interrupt transmission from both hosts.

We declare no competing interests. The findings and conclusions in this Correspondence are our own and do not necessarily represent the official position of the US Centers for Disease Control and Prevention.

References

1Galán-Puchades, MT. Dogs and Guinea worm eradication. Lancet Infect Dis. 2016; 16: 770

2Muller, R. Dracunculus and dracunculiasis. Adv Parasitol. 1971; 9: 73–151

3Cairncross, S, Muller, R, and Zagaria, N. Dracunculiasis (Guinea worm disease) and the eradication initiative. Clin Micro Rev. 2002; 15: 223–246

4Eberhard, ML, Ruiz-Tiben, E, Hopkins, DR et al. The peculiar epidemiology of dracunculiasis in Chad. Am J Trop Med Hyg. 2014; 90: 61–70

5Moorthy, VN and Sweet, WC. Further notes on the experimental infection of dogs with dracontiasis. Am J Hyg. 1938; 27: 301

6Muller, R. Experimental dracontiasis in animals. Parasitology. 1968; 58: 7–8 

7Eberhard, ML, Yablsey, MJ, Zirimwabagabo, H et al. Possible role of fish and frogs as paratenic hosts of Dracunculus medinensis Chad. Emerg Inf Dis. 2016; 22: 1428–1430

8CrichtonVFJ and Beverley-Burton, M. Observations on the seasonal prevalence, pathology and transmission of Dracunculus insignis (Nematoda: Dracunculoidea) in the raccoon, Procyon lotor in Ontario. J Wildl Dis. 1977; 13: 273–280

9Eberhard, ML and Brandt, FH. The role of tadpoles and frogs as paratenic hosts in the life cycle of Dracunculus insignis (Nematoda: Dracunculoidea). J Parasitol. 1995; 81: 792–793

10Eberhard, ML, Cleveland, CA, Zirimwabagabo, H, Yabsley, MJ, Ouakou, PT, and Ruiz-Tiben, E. Guinea worm (Dracunculus medinensis) infection in a wild-caught frog, Chad. Emerg Infect Dis. 2016; DOI: http://dx.doi.org/10.3201/eid2211.161332 (published online Nov 15.)