Birds as potential reservoirs of tick-borne pathogens: first evidence of bacteraemia with Rickettsia helvetica

Sándor Hornok,Enikő Gönczi,Regina Hofmann-Lehmann,Marina L Meli,Tibor Csörgő,Dávid Kováts,Zsófia Hadnagy,Nóra Takács,Róbert Farkas

doi:10.1186/1756-3305-7-128

Abstract

BackgroundBirds have long been known as carriers of ticks, but data from the literature are lacking on their role as a reservoir in the epidemiology of certain tick-borne disease-causing agents. Therefore, the aim of this study was to evaluate the presence of three emerging, zoonotic tick-borne pathogens in blood samples and ticks of birds and to assess the impact of feeding location preference and migration distance of bird species on their tick infestation.MethodsBlood samples and ticks of birds were analysed with TaqMan real-time PCRs and conventional PCR followed by sequencing.ResultsDuring the spring and autumn bird migrations, 128 blood samples and 140 ticks (Ixodes ricinus, Haemaphysalis concinna and a Hyalomma specimen) were collected from birds belonging to 16 species. The prevalence of tick infestation and the presence of tick species were related to the feeding and migration habits of avian hosts. Birds were shown to be bacteraemic with Rickettsia helvetica and Anaplasma phagocytophilum, but not with Candidatus Neoehrlichia mikurensis. The prevalence of rickettsiae was high (51.4%) in ticks, suggesting that some of them may have acquired their infection from their avian host.ConclusionBased on the present results birds are potential reservoirs of both I. ricinus transmitted zoonotic pathogens, R. helvetica and A. phagocytophilum, but their epidemiological role appears to be less important concerning the latter, at least in Central Europe.

Highlights

Birds have long been known as carriers of ticks, but data from the literature are lacking on their role as a reservoir in the epidemiology of certain tick-borne disease-causing agents
Birds can fly over large distances in the course of a few days, during their seasonal migration. They have long been known for their epidemiological role as carriers of hard ticks (Acari: Ixodidae), implying that tick-borne pathogens in ticks attached to avian hosts can be transported to geographically distant places [1]
Ixodes ricinus was found on the majority of tick-infested birds (63 of the 68 individuals: 92.6%, confidence intervals (CIs): 83.797.6%)

Summary

Introduction

Birds have long been known as carriers of ticks, but data from the literature are lacking on their role as a reservoir in the epidemiology of certain tick-borne disease-causing agents. Birds can fly over large distances in the course of a few days, during their seasonal migration. They have long been known for their epidemiological role as carriers of hard ticks (Acari: Ixodidae), implying that tick-borne pathogens in ticks attached to avian hosts can be transported to geographically distant places [1]. If larvae or nymphs acquire tick-borne pathogens with their blood meal, they will be able to infect another host only during a subsequent developmental stage, which is referred to as transstadial transmission [2]. Tick-borne pathogens taken up by adult female ticks will only be able to gain access to another host, if they pass through the ovaries/ova of the female ticks to the generation (i.e. with transovarial transmission) [2]

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