Spotted fever Rickettsia species in Hyalomma and Ixodes ticks infesting migratory birds in the European Mediterranean area.

Katarina Wallménius,Per-Eric Lindgren,Christos Barboutis,Erik Salaneck,Björn Olsen,Kenneth Nilsson,Fredrik Nyström,Thord Fransson,Thomas Gt Jaenson

doi:10.1186/1756-3305-7-318

Abstract

BackgroundA few billion birds migrate annually between their breeding grounds in Europe and their wintering grounds in Africa. Many bird species are tick-infested, and as a result of their innate migratory behavior, they contribute significantly to the geographic distribution of pathogens, including spotted fever rickettsiae. The aim of the present study was to characterize, in samples from two consecutive years, the potential role of migrant birds captured in Europe as disseminators of Rickettsia-infected ticks.MethodsTicks were collected from a total of 14,789 birds during their seasonal migration northwards in spring 2009 and 2010 at bird observatories on two Mediterranean islands: Capri and Antikythira. All ticks were subjected to RNA extraction followed by cDNA synthesis and individually assayed with a real-time PCR targeting the citrate synthase (gltA) gene. For species identification of Rickettsia, multiple genes were sequenced.ResultsThree hundred and ninety-eight (2.7%) of all captured birds were tick-infested; some birds carried more than one tick. A total number of 734 ticks were analysed of which 353 ± 1 (48%) were Rickettsia-positive; 96% were infected with Rickettsia aeschlimannii and 4% with Rickettsia africae or unidentified Rickettsia species. The predominant tick taxon, Hyalomma marginatum sensu lato constituted 90% (n = 658) of the ticks collected. The remaining ticks were Ixodes frontalis, Amblyomma sp., Haemaphysalis sp., Rhipicephalus sp. and unidentified ixodids. Most ticks were nymphs (66%) followed by larvae (27%) and adult female ticks (0.5%). The majority (65%) of ticks was engorged and nearly all ticks contained visible blood.ConclusionsMigratory birds appear to have a great impact on the dissemination of Rickettsia-infected ticks, some of which may originate from distant locations. The potential ecological, medical and veterinary implications of such Rickettsia infections need further examination.

Highlights

A few billion birds migrate annually between their breeding grounds in Europe and their wintering grounds in Africa
Except for spotted fever group (SFG) rickettsiae, other microbial agents including Borrelia burgdorferi, Anaplasma phagocytophilum, the tick-borne encephalitis (TBE) and the Crimean-Congo hemorrhagic fever (CCHF) viruses are known to be vectored by ticks, which sometimes infest migratory birds [4,5,6,7,8,9,10,11]
This study aimed to investigate if ticks, which infest migratory passerine birds in Africa are infected with Rickettsia species when they arrive on their avian hosts in southern Europe

Summary

Introduction

A few billion birds migrate annually between their breeding grounds in Europe and their wintering grounds in Africa. Many bird species are tick-infested, and as a result of their innate migratory behavior, they contribute significantly to the geographic distribution of pathogens, including spotted fever rickettsiae. In contrast to I. frontalis, ticks of the H. marginatum species complex are two-host ticks This signifies that the engorged Hyalomma larva remains on its host on which it moults to become a nymph and to take another blood meal. A Hyalomma tick, which attaches as an unfed larva to a migrating bird can remain up to four weeks on the same bird. Such ticks may be transported long distances, e.g. from sub-Saharan Africa to northern Europe

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