Zoonotic Tick-borne Pathogens Research Articles

Differential Exposure toAnaplasma phagocytophilumin Rodent Species in Northern California

Anaplasma phagocytophilum is a zoonotic tick-borne rickettsial pathogen that causes granulocytic anaplasmosis (GA) in humans, horses, and dogs. In California, dusky-footed woodrats (Neotoma fuscipes) are a putative reservoir host, and Ixodes pacificus is a vector for transmission from rodents to humans, dogs, and horses. Cases are clustered in coastal and Sierra Nevada foothill regions, but not necessarily in proximity to infected woodrats. This study was designed to compare exposures and active infections of A. phagocytophilum in multiple rodents at a fine spatial scale in a hyperenzootic area and to evaluate the spatial clustering of infections. Of 331 rodents, the seroprevalence was 14.5%, with 60% in tree squirrels (Sciurus griseus and Tamiasciurus douglasii), 29% in woodrats, 14% in flying squirrels (Glaucomys sabrinus), and 5% in chipmunks (Tamias senex). No seropositive ground squirrels (Spermophilus beecheyi) were detected. The seroprevalence was significantly higher west of the Trinity River (23.1%) than east (11.8%) of the river. One Douglas squirrel and one western gray squirrel were polymerase chain reaction (PCR) positive. There was more spatial clustering among seropositive animals compared with all animals tested across the spatial scales evaluated, and this clustering was significantly greater than expected by chance alone. A significant cluster of 24 seropositive animals was found west of the Trinity River, with a population of 56 animals considered within the 50% population-at-risk, and a radius of 362.8 meters. The diversity of cricetine and sciurid rodents infected suggests that squirrels and chipmunks may be underappreciated contributors to A. phagocytophilum ecology in the western United States. The spatial clustering of exposed animals suggests interesting underlying spatially heterogeneous environmental variables that could facilitate the persistence of A. phagocytophilum in nature.

SympatricIxodes triangulicepsandIxodes ricinusTicks Feeding on Field Voles (Microtus agrestis): Potential for Increased Risk ofAnaplasma phagocytophilumin the United Kingdom?

The importance of wild rodents as reservoirs of zoonotic tick-borne pathogens is considered low in the United Kingdom because, in studies to date, those parasitized by exophilic Ixodes ricinus ticks carry almost exclusively larvae and thus have a minor role in transmission cycles. In a cross-sectional study, 11 (6.7%) of 163 field voles (Microtus agrestis) captured at field sites in Northern England were PCR-positive for Anaplasma phagocytophilum. The voles were found to act as hosts for both larval and nymphal I. ricinus and all stages of the nidicolous tick I. trianguliceps, and eight individuals were infested with ticks of both species at the same time. Two of 158 larval and one of 13 nymphal I. ricinus, as well as one of 14 larval and one of 15 nymphal I. trianguliceps collected from the rodents were PCR-positive. These findings suggest that habitats where field voles are abundant in the United Kingdom may pose a risk of A. phagocytophilum infection because (i) field voles, the most abundant terrestrial mammal in the United Kingdom, may be a competent reservoir; (ii) the field voles are hosts for both nymphal and larval ixodid ticks so they could support endemic cycles of A. phagocytophilum; and (iii) they are hosts for nidicolous I. trianguliceps, which may alone maintain endemic cycles, and exophilic I. ricinus ticks, which could act as a bridge vector and transmit infections to humans and domesticated animals.

MSV003 Diversity of Borrelia burgdorferi s.l. species and OspA-types in Ixodes ricinus ticks from Germany

Ixodes ricinus is the most important tick species in Europe as it is most widely distributed and transmits the majority of tick-borne zoonotic pathogens. As limited data are available for Hungary, the aim of the present study was to investigate the seasonal timing of questing by I. ricinus and the infection rate of this tick species with all major tick-borne zoonotic pathogens. Monthly collections of I. ricinus were carried out over 3 consecutive years by dragging a blanket in 6 biotopes representing different areas of Hungary. Altogether, 1800 nymphs (300 per collection point) were screened as pooled samples (each of 5 specimens) by PCR-based methods for tick-borne pathogens. I. ricinus larvae, nymphs, and adults had bimodal activity patterns with a major peak in the spring. As newly moulted ticks of all stages are thought to emerge in the autumn of each year, it appears that most newly emerged ticks delayed their questing until the following spring. The minimum prevalence of Borrelia burgdorferi sensu lato was 2.5%. Borr. afzelii, Borr. burgdorferi sensu stricto, Borr. garinii, Borr. lusitaniae, and Borr. valaisiana were identified by hybridization. The minimum infection rate with spotted fever group rickettsiae was 1.9%. Rickettsia helvetica was identified in all biotopes. The minimum prevalence of Anaplasma phagocytophilum, Babesia divergens and Bab. microti was low (0.3–0.5%). Bartonella spp.-, Francisella tularensis-, and TBE virus-specific amplification products were not detected. Relative to the results of comparable studies carried out in the Carpathian Basin, the prevalence of tick-borne pathogens was low in Hungary. This might be attributed to the climatic difference between the lowland areas of Hungary and submountain areas of the surrounding countries involved in the studies.

New molecular biology detection methods for tick-borne infectious agents

Tick-borne zoonotic pathogens are well known in many areas all over the world. Among the tick-borne transmitted diseases in Switzerland, Lyme disease caused by Borrelia burgdorferi, ehrlichiosis caused by various species of Ehrlichia and tick-borne encephalitis caused by the tick-borne encephalitis virus (TBEV) are the most important zoonotic diseases. Early diagnosis and treatment is necessary to prevent fatal infections and chronic damage to various tissues. Due to the variety of uncharacteristic clinical signs, tick-borne diseases are not easily recognized. Diagnosis is based on clinical findings, a record of tick exposure, and direct or indirect detection of the pathogen. Here we discuss briefly the most important tick-borne infections and their diagnosis with emphasis on a new molecular diagnostic tool--the real-time TaqMan PCR--and its importance for the diagnosis of tick-borne pathogens.