Yersinia pestis found in human fleas, Madagascar 2013

Madagascar is consistently one of the top two countries in Africa (and usually the world) in cases of plague, caused by Yersinia pestis. For five years prior to January 2013, Madagascar registered 312 to 648 cases per year, with a majority being laboratory confirmed of which >80% were bubonic plague. Of the multiple reservoir species in Madagascar, the black rat (Rattus rattus) is the primary reservoir with Xenopsylla choepus being the main urban vector and Synopsyllus fonquerniei in rural areas.

After a nine case bubonic outbreak in the rural area of Soavina in the district of Ambatofinandrana (shown below), fleas were collected within and outside of five houses over three nights.


The team from the Institut Pasteur de Madagascar collected 319 fleas representing five genera; the most common being the human flea Pulex irritans (73.3%).  In this study, X. cheopis and S. fonquerniei were only collected outside of the houses. Pulex irritans was found only indoors where it made up 95.5% of flea species. Of the 274 fleas tested for Yersinia pestis, 9 pulex irritans were positive. These positive human fleas came from three homes, one of which had a confirmed case of human plague. None of the other flea species tested positive for plague.

Previous observations of pulex irritans in Madagascar suggest this flea may be responsible for domestic human-to-human transmission. High densities of human fleas were reported in plague outbreak villages in 2012-2013. Flea surveys on rats in Madagascar conducted over the last three quarters of a century show that pulex irritans are very rare on rats, suggesting it is not transmitting plague from rats to humans at least in Madagascar. Although pulex irritans are commonly called the human flea, they will feed on dogs and pigs  in addition to humans.  They have also been sporadically found on a variety of other mammals and birds, including rats.

Coping with human fleas as plague vectors will be a significant extra burden on the public health services of Madagascar. Ridding homes of human fleas can be a difficult task. It will however give plague researchers an opportunity to study pulex irritans as a vector in one of the top human plague producing countries in the world.

Within the last ten years, Madagascar has produced human plague cases from three different fleas and pneumonic transmission. With its diversity of plague reservoirs and now flea vectors, Madagascar is illustrating how deeply Yersinia pestis can penetrate and become entrenched in the environment.

Reference:

Ratovonjato J, Rajerison M, Rahelinirina S, Boyer S. “Yersinia pestis in Pulex irritans fleas during plague outbreak, Madagascar” [letter]. Emerging Infectious Disease. 2014 Aug [30 June 2014].http://dx.doi.org/10.3201/eid2008.130629

Wyrwa, J. 2011. “Pulex irritans” (On-line), Animal Diversity Web. Accessed July 01, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Pulex_irritans/

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4 thoughts on “Yersinia pestis found in human fleas, Madagascar 2013

  1. Perhaps the extreme environmental degredation has left a paucity of hosts leaving humans as the most logical target for disease.

  2. Reblogged this on archaeotutor and commented:
    Those of you who have taken the ‘Black Death’ course may be interested in this post. In our last session of that course, you may recall we looked at the modern situation and this is a nice summary of a recent study in Madagascar.

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