Natural Transmission of ZoonoticBabesiaspp. byIxodes ricinusTicks

Abstract

To determine characteristics of natural transmission of Babesia sp. EU1 and B. divergens by adult Ixodes ricinus ticks, we examined tick salivary gland contents. We found that I. ricinus is a competent vector for EU1 and that their sporozoites directly invade erythrocytes. We conclude that EU1 is naturally transmitted by I. ricinus. Ixodes ricinus is a ubiquitous triphasic tick found commonly in Europe. This arthropod feeds on a wide variety of vertebrate hosts, including small rodents and wild and domestic ungulates. It is therefore a potential vector of numerous pathogens, such as bacteria, viruses, and parasites, mainly apicomplexans. Among these pathogens, 2 zoonotic Babesia species have been described in Europe: the well-known cattle parasite Babesia divergens (1) and the more recently reported roe deer parasite Babesia sp. EU1 (2-4). Biological transmission of B. divergens by I. ricinus ticks has been proven by in vivo experimental infections (5); however, quantitative transmission studies that visualize and quantify sporozoites have never been conducted. For Babesia sp. EU1, biological evidence of natural transmission by I. ricinus ticks is still lacking; its presence has been assessed only by DNA amplifi cation from whole ticks (4,(6)(7)(8). Therefore, to analyze transmission of zoonotic Babesia spp. by I. ricinus ticks, we visualized, isolated, and identifi ed infectious sporozoites from dissected tick salivary glands, the transmitting organs. The StudyIn 2008, ticks were collected from animals from 2 different biotopes where each Babesia species had been known to circulate: a farm on which a herd was infected with B. divergens and a reserve on which wild fauna were infected with Babesia sp. EU1. A dairy farm in La Verrie (Vendée, France) was selected as a favorable biotope for B. divergens transmission on the basis not only of the presence of numerous ticks on cows and in pastures in 2007 but also of the parasite circulation in the herd, attested by serologic testing (prevalence of 37.5% by immunofl uorescence antibody test [IFAT]) and confi rmed by its isolation from cattle erythrocytes (prevalence 25% by culture) (9). Of the cows tested by IFAT, 56% had positive results, which indicated that new infections from ticks were occurring within the herd. Because we assumed that sporozoite differentiation is stimulated by blood ingestion and because of experimental proof that female ticks can transmit B. divergens (10), we collected only adult ticks feeding on cows. The 324 collected ticks were morphologically identifi ed as I. ricinus and weighed to estimate their repletion status (range 3-398 mg). Of these, 223 ticks (4.7-339 mg) were dissected under a stereomicroscope to isolate both salivary glands, which were subsequently crushed in 30 μL phosphate-buffered saline in a 1.5-mL microtube with an adapted pestle. A droplet of this suspension was deposited on an 18-well slide, stained with May-Grünwald-Giemsa, and examined under a light microscope. When parasites were seen, and for 41 additional negative sa...

Longitudinal field study on bovine Babesia spp. and Anaplasma phagocytophilum infections during a grazing season in Belgium

“…EU1 was the only species found in both feeding and questing I. ricinus, despite the high number of ticks that were screened and the selection of farms located in a region previously identified as endemic for B. divergens. The same finding was previously described by Becker et al (2009), who found no evidence for B. divergens sporozoites in engorged adult or unfed I. ricinus ticks. Cattle and deer are the main hosts of adult I. ricinus ticks and are potential carriers of B. divergens.…”

“…and bacteria within the genus Anaplasma, respectively. Ixodes ricinus, the most prevalent tick species in northern and western Europe, is an important vector of both these pathogens (Baumgarten et al 1999;Becker et al 2009;Bonnet et al 2009). …”

Transfusion-TransmittedBabesiaspp.: Bull's-Eye onBabesia microti

“…This tick has also been shown to be a competent vector for Babesia sp. strain EU-1 (7,9). Roe deer appear to be the wild reservoir host for EU-1, but other reservoir hosts may exist that have not been identified (10).…”

Isolation and characterization of

“…EU1 were not isolated, despite the use of conditions known to be favorable to their growth from animal blood samples [9,10,13,30]. They share the same tick vector, I. ricinus [31][32][33], and the absence of these three Babesia species in the study region may be explained by the absence or very low abundance of this tick species in these regions [34]. However, we report here the isolation and characterization of a new Babesia from two geographically distant herds in Spain.…”