Tübingen, 21th of August 2017. Scientists from the Max Planck Institute for Developmental Biology Tübingen isolated the nematode Strongyloides stercoralis from humans and their dogs in rural Cambodia and compared the worms using molecular-biological analyses. The aim of the study was to find out whether dogs are a potential source of zoonotic transmission of this parasite or not. S. stercoralis causes the much-neglected soil born helminthiasis strongyloidiasis, wich is listed on the WHO list of neglected tropical diseases. The results of the study are now published in the journal PLOS Neglected Diseases.
It is a well-known saying that dog owners look like their pets. Apart from outward appearances – they are sure to share their parasites. And even these are sometimes that very much alike, so they can only be distinguished by genetic analyzes. Researchers from the MPI for developmental Biology now did this distinction using nuclear and mitochondrial DNA sequence polymorphisms.
Strongyloidiasis - a neglected disease
S. stercoralis, a soil-transmitted nematode, causes a neglected tropical helminthiasis and is endemic in tropical, subtropical and temperate settings with poor sanitary and hygiene conditions. Strongyloidiasis is a chronic parasitic infection of humans and animals. Some 300 million people are estimated to be infected worldwide. Usually, strongyloidiasis has mild manifestations, the infection may be severe and life-threatening in cases of immunodeficiency. Therefore it is important that a public health strategy will be developed to control strongyloidiasis.
People and their dogs - a relationship with side effects
The prevalence of S. stercoralis in rural Cambodia is very high and people live in close coexistence with their dogs. This setting made it easy for Siyu Zhou and Tegen G. Jaleta from the Department of Evolutionary Biology at the MPI for Developmental Biology to take fecal samples from humans and dogs of the same household.
In collaboration with colleagues from the Swiss Tropical and Public Health Institute in Basel, and from the Cambodian Ministry of Health, they isolated S. strecoralis larvae from the collected samples and analyzed the worms derived from these two host species using nuclear and mitochondrial DNA sequence polymorphisms. They found that in dogs there exist two populations of S. stercoralis, which are clearly separated from each other genetically based on the nuclear and the mitochondrial, sequence. One population, to which the majority of the worms belong to, appears to be restricted to dogs. The other population is indistinguishable from the population of S. stercoralis isolated from humans.
Effective disease control only with broad knowledge
The results strongly suggest that there is a considerable risk for a dog to human transmission. The potential of dogs as reservoirs for zoonotic transmission of S. stercoralis to humans suggests that in order to reduce the exposure of humans to infective S. stercoralis larvae, it might be beneficial to treat dogs for the infection along with their owners and to reduce the exposure of humans to dog feces.
Original Publication: Jaleta TG, Zhou S, Bemm FM, Schär F, Khieu V, Muth S, et al. (2017) Different but overlapping populations of Strongyloides stercoralis in dogs and humans—Dogs as a possible source for zoonotic strongyloidiasis. PLoS Negl Trop Dis 11(8): e0005752. https://doi.org/10.1371/journal.pntd.0005752
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The Max Planck Institute for Developmental Biology conducts basic research in the fields of biochemistry, genetics and evolutionary biology. It employs about 350 people and is located at the Max Planck Campus in Tuebingen, Germany. The Max Planck Institute for Developmental Biology is one of 80 research institutes that the Max Planck Society for the Advancement of Science maintains in Germany.