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Universität Hamburg (2020)

Investigations on the abundance of ectoparasites and vector-borne pathogens in southwest Madagascar

Ehlers, Julian

Titre : Investigations on the abundance of ectoparasites and vector-borne pathogens in southwest Madagascar

Untersuchungen zum Vorkommen von Ektoparasiten und verktorübertragenen Krankheitserregern in Südwest Madagaskar

Auteur : Ehlers, Julian

Université de soutenance : Universität Hamburg

Grade : Doctoral degree 2020

Résumé partiel
Human encroachment on natural habitats is steadily increasing due to the rapid growth of the worldwide population. The consequent expansion of agricultural land and livestock husbandry, accompanied by spreading of commensal animals, create new interspecific contact zones that are major regions of risk of the emergence of diseases and their transmission between livestock, humans and wildlife. Among the emerging diseases of the recent years those that originate from wildlife reservoirs are of outstanding importance. Many vector-borne diseases are still underrecognized causes of fever throughout the world and tend to be treated as undifferentiated illnesses. The lack of human and animal health facilities, common in rural areas, bears the risk that vector-borne infections remain unseen, especially if they are not among the most common. Ectoparasites represent an important route for disease transmission besides direct contact to infected individuals. While factors driving disease emergence are clearly visible in Madagascar, the knowledge of ectoparasites and potential pathogens is alarmingly limited. Following the One Health concept, this dissertation approaches the presence of ectoparasites and vector-borne bacteria, taking environmental factors and host ecology into account in order to identify possible transmission paths at the human/animal interface. The study took place in the northern portion of Tsimanampetsotsa National Park and the adjacent coastal strip in southwest Madagascar, in the dry and in the rainy season of 2016/2017. For the survey on ectoparasites species and the influence of habitat alteration, endemic mammals were trapped in transects of box traps installed in three habitats revealing different degrees of disturbance : Forest of the national park, degraded forest, and cultivated land. Additionally, Rattus rattus and Mus musculus were trapped inside villages, and livestock was sampled. I identified 17 species of ectoparasites, thirteen of which (blood-feeding lice, fleas and ticks) were subjected to further investigation for the presence and identity of rickettsiae, borreliae, bartonellae and Yersinia pestis using PCR techniques. This study presents the molecular detection of a broad spectrum of vector-borne bacteria including pathogens : Yersinia pestis in X. cheopis, Ricksttsia felis-like organisms in several fleas and Rickettsia africae in all ectoparasite species except one. Borreliae and bartonellae were found only in two ectoparasite species each. A large portion of the parasites was host-specific, barely stating threats for cross species transmission. Apart from the introduced flea species Echidnophaga gallinacea no interspecific parasite transfer occurred between introduced and native mammals. Microcebus griseorufus, which was the only endemic mammal caught in statistically sufficient numbers, revealed the highest louse prevalence inside the least degraded habitat, contrary to the common assumption that the prevalence of ectoparasites increases in degraded areas. This study also confirms the littoral site as less suitable habitat for most introduced ectoparasite species.

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