The roles of birds, lizards, and rodents as hosts for the western black-legged tick Ixodes pacificus.

We compared the infestation by ixodid ticks of lizards, rodents, and birds collected simultaneously within areas representing common habitat types in Mendocino County, CA. Lizards were infested only by Ixodes pacificus Cooley and Kohls, birds by I. pacificus and Haemaphysalis leporispalustris (Packard), and rodents by I. pacificus, I. spinipalpis Hadwen and Nuttall, I. woodi Bishopp, Dermacentor occidentalis Marx, and D. variabilis (Say). Infestation by I. pacificus larvae and nymphs of lizards (Sceloporus occidentalis Baird and Girard; Elgaria spp.) and western gray squirrels (Sciurus griseus Ord) (means of 9-35 larvae and 5-6 nymphs per animal) was several times greater than for Neotoma fuscipes Baird woodrats, Peromyscus spp. mice, and birds (means of 0.9-3.5 larvae and 0-0.3 nymphs). Overall, Borrelia-refractory lizards accounted for 84% of I. pacificus larvae and 91% of nymphs collected from animals in dense woodlands. Bird species frequently utilizing tick-questing substrates such as leaf litter (guild I birds) were more heavily infested by I. pacificus subadults (5.2 larvae and 1.0 nymphs per bird) than guild IV birds with minimal perceived contact with tick-questing substrates (0.08 larvae and 0.06 nymphs per bird). Notably, guild I birds carried similar larval loads and at least 20-fold higher nymphal loads relative to woodrats and mice. Only guild IV birds carried as few I. pacificus nymphs as did these rodents. The ratios of larvae to nymphs suggest that, relative to birds, lizards, and squirrels (infested by 1.3-6.0 larvae per nymph), nocturnally active ground-dwelling rodents such as woodrats and mice are underutilized by the nymphal stage (69 to >100 larvae per nymph). The western gray squirrel and guild I-II birds (e.g., the dark-eyed junco, Junco hyemalis [L.]) were the only potential reservoirs of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner (the causative agent of Lyme disease in North America) that were frequently infested with both I. pacificus larvae and nymphs and commonly utilized dense woodland habitats.     

Birds and their ticks in northwestern California: minimal contribution to Borrelia burgdorferi enzootiology

Birds and their attendant ticks were surveyed for infection with the Lyme disease spirochete Borrelia burgdorferi, in chaparral and woodland-grass habitats in northwestern California from March to July, 1998 to 1999. In total, 234 birds were captured and recaptured (15%); nearly 2.5 times more birds were captured in chaparral than in woodland-grass. Overall, 34 species representing 15 families were collected during this study; of these, 24 species were caught in chaparral, 19 in woodland-grass, and 9 in both vegetational types. The most frequently captured birds were sage sparrows (Amphispiza belli) in chaparral, and American robins (Turdus migratorius) and oak titmice (Baelophus inornatus) in woodland-grass. Birds hosted 35 Ixodes pacificus (15 larvae, 20 nymphs) and 9 Haemaphysalis leporispalustris (3 larvae, 5 nymphs, 1 adult) ticks, of which 32 were removed from chaparral birds and 12 from woodland birds. The prevalence of tick infestation was 13% (21/167) in chaparral and 5% (3/67) in woodland-grass, but the relative and mean tick intensities of 0.19 and 1.5 for chaparral birds, and 0.18 and 4.0 for woodland birds, respectively, did not differ significantly by habitat. Spirochetes were not detected in either bird-blood or tick-tissue samples when tested by culture, immunofluorescence, or Giemsa-staining. In contrast, over 90% (86/94) of western fence lizards (Sceloporus occidentalis) collected in June or July were infested with an average of 6.9 and 8.9 immature I. pacificus in chaparral and woodland-grass, respectively. We conclude that birds contribute little to the enzootiology of B. burgdorferi in chaparral and woodland-grass habitats in northwestern California because of their limited parasitism by tick vectors and lack of detectable spirochetemias.     

Habitat-related variation in infestation of lizards and rodents with Ixodes ticks in dense woodlands in Mendocino County, California

During the spring and early summer of 2002, we examined the relative importance of Borrelia-refractory lizards (Sceloporus occidentalis, Elgaria spp.) versus potential Borrelia burgdorferi sensu lato (s.l.)-reservoirs (rodents) as hosts for Ixodes pacificus immatures in 14 woodland areas (six oak, five mixed oak/Douglas fir, and three redwood/tanoak areas) distributed throughout Mendocino County, California. Lizards were estimated to serve as hosts for 93-98% of all larvae and > or =99.6% of all nymphs infesting lizards or rodents in oak woodlands and oak/Douglas fir sites in the southern part of the county. In redwood/tanoak woodlands and oak/Douglas fir sites in northern Mendocino County, the contribution of rodents to larval feedings reached 36-69% but lizards still accounted for 94-100% of nymphal bloodmeals. From late April to mid-June, I. pacificus larvae were recovered from 95 to 96% of lizards and dusky-footed woodrats (Neotoma fuscipes) and from 59% of Peromyscus spp. mice. In contrast, 99% of lizards but few woodrats (15%) and none of the mice were infested by nymphs. Comparisons of tick loads for 19 lizard-Peromyscus spp. mouse pairings, where the lizard and mouse were captured within 10m of each other, revealed that the lizards harbored 36 times more larvae and >190 times more nymphs than the mice. In oak woodlands, loads of I. pacificus larvae decreased from late April/early May to late June for S. occidentalis lizards but increased for Peromyscus spp. mice. We conclude that the relative utilization of Borrelia-refractory lizards, as compared to rodents, by I. pacificus larvae was far higher in dry oak woodlands than in moister habitats such as redwood/tanoak and oak/Douglas fir woodlands in northern Mendocino County. Non-lizard-infesting potential enzootic vectors of B. burgdorferi s.l. (I. angustus and I. spinipalpis) were recorded from rodents in three of six oak woodland areas, two of five oak/Douglas fir woodland areas, and two of three redwood/tanoak woodland areas.     

Prevalence and abundance of Ixodes pacificus immatures (Acari: Ixodidae) infesting western fence lizards (Sceloporus occidentalis) in northern California: temporal trends and environmental correlates.

The prevalence and abundance of immature Ixodes pacificus ticks on western fence lizards (Sceloporus occidentalis) were examined in relation to time of year, host attributes (i.e., age, gender, and presence or absence of blood parasites), and 5 environmental characteristics, including topographic exposure and ground cover substrate, over a 2-year period in northern California. Lizards were infested with subadult ticks from early March until late July or early August, with peak median numbers of larvae and nymphs recorded in late April and early May of both years. Peak larval and nymphal abundances differed between years. The overall ratio of larvae to nymphs on adult male lizards was low, ranging from 0.80 in 1999 to 2.41 in 2000. Such intensive feeding of nymphs versus larvae on these lizards, which are reservoir-incompetent for Borrelia burgdorferi spirochetes, may explain previous observations of decreasing spirochetal infection prevalence from the nymphal to adult stage in northwestern California. Adult male lizards were more likely to be infested with nymphs and harbored greater abundances of larvae and nymphs than adult females. Lizards uninfected with blood parasites had more nymphs than infected lizards. The measured environmental characteristics could explain only a small percentage of the total variation observed in larval prevalence (22%) and in larval and nymphal abundance (12 and 3%, respectively).     

Relative importance of lizards and mammals as hosts for ixodid ticks in northern California

Lizards and mammals were trapped and examined for ticks from August 1992 to June 1993 in two habitat types, chaparral and woodland-grass, in northern California. Five tick species were collected from mammals (Dermacentor occidentalis, Haemaphysalis leporispalustris, Ixodes pacificus, I. spinipalpis, I. woodi), but only I. pacificus was found on lizards. Dermacentor occidentalis, I. pacificus, and I. woodi occurred in both habitats, whereas H. leporispalustris and I. spinipalpis were found only on animals trapped in chaparral. The tick species most commonly encountered on mammals was D. occidentalis in chaparral and I. pacificus in woodland-grass. Peak infestation of mammals occurred in spring for I. pacificus immatures and H. leporispalustris, summer for D. occidentalis immatures, fall through spring for I. woodi immatures, and fall through winter for I. spinipalpis. The primary aim of the study was to quantify the relative importance of the western fence lizard (Sceloporus occidentalis), which is reservoir-incompetent for Borrelia burgdorferi sensu lato (s.l.), and mammalian B.burgdorferi s.l.-reservoirs as hosts for the immature stages of I. pacificus in spring. The estimated relative utilization by I. pacificus of the western fence lizard versus mammals was 88% for larvae and 99% for nymphs in chaparral in May. When tick infestation data were corrected for a two-fold lower efficiency of field examinations for rodents than for lizards, the western fence lizard still accounted for 78% of larval and 98% of nymphal feedings. In woodland-grass, 46% of 100 I. pacificus larvae and 100% of 52 nymphs recovered from mammals or western fence lizards during May-June were collected from the lizards. However, this may represent an underestimate of the importance of the western fence lizard as a larval host in this habitat because inclement weather during the late May sampling period doubtless resulted in significantly decreased lizard activity. In conclusion, the western fence lizard was more heavily utilized by I. pacificus immatures, especially nymphs, than were rodents. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lacerta bilineata (Reptilia,Lacertidae) as a host of Ixodes ricinus (Acari,Ixodidae) in a protected area of northern Italy

A survey on the importance of Lacerta bilineata as host of Ixodes ricinus was conducted in Northern Italy over a three-year period. A total of 202 western green lizards were captured and a total of 2349 ticks were collected. All ticks were identified as I. ricinus; 53.2% and 46.7% were at the larval and nymphal stages, respectively. Tick number and prevalence were higher in males than in females, especially from April to June during the host breeding period. The level of tick infestation increased with lizard age and size. The number of ticks collected on adult lizards peaked in June and in August. Infestation levels appear to be related to lizard activity patterns and behaviour. Tick number and prevalence also varied in relation to host habitat, infestation being higher in lizards from areas with hard vegetation cover.     

The impact of tick load on the fitness of their lizard hosts

A survey was conducted of natural populations of the sleepy lizard Tiliqua rugosa in South Australia to determine whether infestation by ectoparasitic ticks reduced their fitness. Between 1982 and 1990, 2183 captures of 824 individual lizards were made in an area where they were infested by the tick Aponomma hydrosauri, and 3668 captures of 586 individual lizards were made in an area where they were infested with the tick Amblyomma limbatum. Lizards with high tick loads in one year tended to have high loads the next year. Longevity of lizards in the study was either not correlated with tick load, or positively correlated. Size achieved was greater amongst lizards with greatest tick load, and lizards in mating pairs had higher tick loads than those never found in pairs. The data do not support the hypothesis that tick load diminishes host fitness.     

Wild turkey (Meleagris gallopavo) as a host of ixodid ticks, lice, and Lyme disease spirochetes (Borrelia burgdorferi sensu lato) in California state parks

Rio Grande wild turkeys (Meleagris gallopavo intermedia) were evaluated as potential hosts of ixodid ticks, lice, and Lyme disease spirochetes (Borrelia burgdorferi sensu lato [s.l.]) in three state parks in Sonoma County, California, USA, during 2003 and 2004. In total, 113 birds were collected, 50 (44.2%) of which were found to be infested by 361 ixodid ticks representing three species: the western black-legged tick (Ixodes pacificus, n=248), the rabbit tick (Haemaphysalis leporispalustris, n=112), and one American dog tick (Dermacentor variabilis). Year-round the prevalence of all ticks combined was unrelated to the age or sex of turkeys, and the prevalence of infestation by I. pacificus (35.4%) was significantly higher than it was for either H. leporispalustris (14.2%) or D. variabilis (0.9%). The proportion of the two prevalent tick species differed significantly by life stage with 86.3% of the I. pacificus and 82.1% of the H. leporispalustris enumerated being nymphs and larvae, respectively. Three species of lice were collected, including the chicken body louse Menacanthus stramineus (12.5% of total), Chelopistes meleagridis (37.5% of total), and Oxylipeurus polytrapezius (50% of total). The records for all three ticks are the first ever from wild turkeys, and those for the lice are the first from this host in the far-western United States. Wild turkeys potentially were exposed to the feeding activities of I. pacificus nymphs infected with B. burgdorferi s.l. as 15% of host-seeking nymphs (n=200) collected in woodlands used by turkeys as roosting or foraging areas were infected mainly with B. burgdorferi sensu stricto (s.s.). However, only one (1%) of 90 turkey blood specimens tested by PCR contained B. burgdorferi s.s., and four in vitro, complement-protein assays demonstrated that domestic turkey serum is moderately bacteriolytic for this spirochete. Taken together, these findings indicate that wild turkeys are important avian hosts of I. pacificus nymphs, but they appear to be inconsequential hosts of B. burgdorferi s.l.     

Relative utilization of reptiles and rodents as hosts by immature Ixodes scapularis (Acari: Ixodidae) in the coastal plain of North Carolina,USA

The interaction of immature black-legged ticks, Ixodes scapularis, with reptiles and rodents was investigated in various woodland habitats in the coastal plain of North Carolina. Reptiles were sampled from April 1 to September 30, 1991. No ticks were found on 95 specimens representing 16 species of snakes. Ticks were found on 54 (36.7%) of 147 lizards. I. scapularis was the only tick recovered from lizards. Some lizards were collected in drift fence traps each month of the study except August. Capture rates averaged one lizard per 16 trap-days. Larvac and nymphs of I. scapularis were removed from the southeastern five-lined skink (Eumeces inexpectatus), the ground skink (Scincella lateralis), the broad-headed skink (E. laticeps) and the eastem glass lizard (Ophisaurus ventralis), but ticks were not found on three other lizard species. Tick infestation rates and loads for parasitized species are presented. Ticks were almost exlusively attached at the base or in the axils of forelimbs of skinks and in the lateral grooves of eastern glass lizards. Rodents were live-trapped at sites where lizards were sampled and at other sites from 1 July, 1990 to 30 January, 1992. Capture rates averaged one rodent per 47 trap-nights. Ticks were found on 23 (17.8%) of 129 animals inspected. Five species of rodents were examined but only four species were found to be tick-infested. In contrast to lizards, few I. scapularis were collected. Rodents, principally the white-footed mouse (Peromyscus leucopus) and cotton mouse (P. gossypinus) were most frequently infested with immature American dog ticks, Dermacentor variabilis, during winter and early spring months. Burdens of D. variabilis on these rodents averaged 0.3 ticks per rodent. Effects of the diversion of ticks from feeding on Peromyscus mice on the transmission of the Lyme disease spirochete are discussed.The use of trade names in this publication does not imply an endorsement by the North Carolina Agricultural Research Service or the College of Veterinary Medicine, North Carolina State University of the products named, nor criticism of similar ones not mentioned. Partial support for this research was provided by the U.S. Marine Corps, The Centers for Disease Control and Prevention, and the North Carolina Agricultural Research Service and College of Veterinary Medicine, North Carolina State University.     

Host-seeking behavior of Ixodes pacificus (Acari: Ixodidae) nymphs in relation to environmental parameters in dense-woodland and woodland-grass habitats

In the far-western United States, the bacteria that cause Lyme disease (Borrelia burgdorferi, Bb) and human granulocytic anaplasmosis (Anaplasma phagocytophilum, Ap) are transmitted by the western black-legged tick (Ixodes pacificus). In a dense woodland, human behaviors involving contact with wood were recently found to pose greater risk for encountering I. pacificus nymphs than behaviors entailing exclusive exposure to leaf litter. A four-year follow-up study was undertaken in the same woodland and, as a comparison area in one year only, in a nearby woodland-grass habitat to explore the biotic and abiotic factors that might elevate human exposure to host-seeking nymphs. Nymphs were active in the dense woodland throughout the daytime, but no consistent pattern of activity was observed with respect to time of day, temperature, or relative humidity. Significantly more nymphs were collected from the southern aspects of dense-woodland trunks than from other aspects, and more nymphs quested at a height of < or = 1 m vs 1-2 m aboveground. The prevalence of bacterial infection in ticks from the dense woodland was highly variable among years, with maxima of 22.6% and 42.9% for Bb, and 15.6% and 1.8% for Ap, in nymphs from logs and trunks, respectively. The mean densities of nymphs, and of Bb- or Ap-infected nymphs, were typically higher on logs and trunks than in adjoining leaf litter or grass in both habitats. The acarologic risk of encountering an infected nymph on dense-woodland logs or trunks was 2.8 to 11 times higher for Bb than for Ap in two of three years, and it was usually higher in dense woodland than in woodland-grass for both agents. Coinfections were rare (0.27%, n = 369 nymphs from both habitats). Individuals having prolonged contact with logs or trunks in spring would be well advised to employ personal protective measures to minimize exposure to I. pacificus nymphs and their attendant bacterial zoonotic agents.     

Risk factors in habitats of the tick Ixodes ricinus influencing human exposure to Ehrlichia phagocytophila bacteria

Ixodes ricinus L. (Acari: Ixodida) were sampled during 1996-99 in southern Scotland, on vegetation using cloth drags, on humans by removal from clothing and on roe deer (Capreolus capreolus L.) by searching legs of culled deer. Developmental microclimate was recorded by automatic recorders and questing microclimate by portable instruments during tick collections. Ticks and deer were examined for infection with Ehrlichia phagocytophila bacteria (Rickettsiales) using microscopy and polymerase chain reaction. This pathogen causes tick-borne fever of sheep in Europe and human granulocytic ehrlichiosis in North America, but in Europe human clinical ehrlichiosis due to E. phagocytophila has not been recorded despite serological evidence of exposure. Among three types of habitat, coniferous woodland was most infested with questing ticks (560 ticks/km of drag; mean numbers collected on long trousers: 24.3 larvae, 13.5 nymphs and 0.8 adult ticks/km walked), deciduous woodland had slightly lower infestation (426 ticks/km drag) and upland sheep pasture had much lower infestation (220 ticks/km drag). Of the three main vegetation types, bracken was least infested (360 ticks/km drag), ericas most (430 ticks/km drag) and grassland had intermediate infestation density (413 ticks/km drag). Questing and developmental microclimates were poor predictors of exposure within these habitats, except lower infestation of pastures was attributed to greater illumination there. Collectors who walked a total of 300 km through all habitats (taking 360 h in all seasons), wearing cotton trousers hanging outside rubber boots, were bitten by only four nymphs and 11 larvae of I. ricinus (but no adult ticks). There was a negative correlation between densities of deer and ticks collected, although presence of deer remains a major indicator of exposure. The proportion of infected ticks was fairly uniform at four sites studied. Overall prevalence of E. phagocytophila in I. ricinus was 3.3% in nymphs (40/1203) but only approximately 1.5% in adults of both sexes (although males do not bite). It was estimated that nymphs of I. ricinus gave 4.4% probability of one infected bite/person/year (for occupational exposure during this research) due to presence in all seasons and habitats, their human biting rate of 0.011 nymphs/h or 0.013 nymphs/km and widespread infection with E. phagocytophila. The frequency distribution of intensity of infection in ticks was approximately normal (mean 98 morulae/nymph infected), thus there is a high risk of receiving a high dose from any one infected tick bite.     

Prevalence of hard tick infestations in cattle of Mizoram,India

The present study was conducted to determine the prevalence of hard tick infestations in cattle of Mizoram from April 2017 to March 2018. The prevalence of hard tick infestations was studied in relation to sex and age of animals and seasonal changes in a year. Cattle of selected places were examined carefully for the presence of ticks and in positive cases ticks were collected manually and identified on the basis of morphological characters. A total of 713 cattle were examined and out of which 452 (63.39%) cattle were found to be infested with hard ticks and the prevalent tick species was Rhipicephalus (Boophilus) microplus. A significantly (p < 0.01) higher infestation was observed in female cattle (66.43%) than males (48.83%). Age-wise highest prevalence of tick infestations was found in 1–5 years (73.41%) age group followed by >5 years age group (61.92%) and < 1 year (42.65%) age group, respectively. Seasonally, the prevalence of hard tick infestation was found highest (p < 0.01) in monsoon (77.91%) and lowest in winter (43.16%). The present study provides data on tick infestation in cattle of Mizoram, India.     

Effects of an invasive forest pathogen on abundance of ticks and their vertebrate hosts in a California Lyme disease focus

Invasive species, including pathogens, can have important effects on local ecosystems, including indirect consequences on native species. This study focuses on the effects of an invasive plant pathogen on a vertebrate community and Ixodes pacificus, the vector of the Lyme disease pathogen (Borrelia burgdorferi) in California. Phytophthora ramorum, the causative agent of sudden oak death, is a non-native pathogen killing trees in California and Oregon. We conducted a multi-year study using a gradient of SOD-caused disturbance to assess the impact on the dusky-footed woodrat (Neotoma fuscipes) and the deer mouse (Peromyscus maniculatus), two reservoir hosts of B. burgdorferi, as well as the impact on the Columbian black-tailed deer (Odocoileus hemionus columbianus) and the western fence lizard (Sceloporus occidentalis), both of which are important hosts for I. pacificus but are not pathogen reservoirs. Abundances of P. maniculatus and S. occidentalis were positively correlated with greater SOD disturbance, whereas N. fuscipes abundance was negatively correlated. We did not find a change in space use by O. hemionus. Our data show that SOD has a positive impact on the density of nymphal ticks, which is expected to increase the risk of human exposure to Lyme disease all else being equal. A positive correlation between SOD disturbance and the density of nymphal ticks was expected given increased abundances of two important hosts: deer mice and western fence lizards. However, further research is needed to integrate the direct effects of SOD on ticks, for example via altered abiotic conditions with host-mediated indirect effects.     

Columbian black-tailed deer (Odocoileus hemionus columbianus) as hosts for Borrelia spp. in northern California

The prevalence of infection of Columbian black-tailed deer (Odocoileus hemionus columbianus) with Borrelia spp. was evaluated in an area of northwestern California (USA) where Lyme disease is endemic and the relapsing-fever group spirochete Borrelia coriaceae is enzootic, and in a far-removed comparison area having a disparate climate and lower density of vector ticks. Blood samples collected from both deer herds in 1987, 1988, and from 2000-02 were assayed for borrelial infection with microscopic and molecular methods. Serum specimens from two (5%) of 39 deer from the Dye Creek Preserve in Tehama County versus 13 (20%) of 64 animals from the Hopland Research and Extension Center (HREC) in Mendocino County, California were polymerase chain reaction (PCR) test positive for B. burgdorferi sensu lato. DNA sequencing analyses revealed that eight animals were infected with B. bissettii, six with three unclassified genotypes, and one with B. burgdorferi sensu stricto. One serum sample (2%) from HREC was positive for a relapsing-fever group spirochete that had a 16S rRNA sequence homology of 99% with the C053 type strain of B. coriaceae. Spirochetes undetermined to geno-species were detected in thick-blood drops prepared from three (8%) of 36 deer from the HREC by direct immunofluorescence. Adults of the hippoboscid flies Lipoptena depressa (n=73) and Neolipoptena ferrisi (n=24), the Pacific Coast tick (Dermacentor occidentalis) (n=22), and the western black-legged tick (Ixodes pacificus) (n=1) that had been removed from deer from both study areas in 2002 were PCR test negative for borreliae. The occurrence of diverse borreliae in deer from northern California confounds and, consequently, reduces the utility of borrelial serosurveys for detecting specific genospecies, unless they are complemented by more specific assays (e.g., immunoblotting, PCR/sequencing analysis).     

Prevalence of Borrelia burgdorferi sensu lato in ticks collected from migratory birds in Switzerland

The prevalence of ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland. A total of 1,270 birds captured at two sites were examined for tick infestation. Ixodes ricinus was the dominant tick species. Prevalences of tick infestation were 6% and 18.2% for birds migrating northward and southward, respectively. Borrelia valaisiana was the species detected most frequently in ticks, followed by Borrelia garinii and Borrelia lusitaniae. Among birds infested by infected ticks, 23% (6/26) were infested by B. lusitaniae-infected larvae. Migratory birds appear to be reservoir hosts for B. lusitaniae.     

Ixodid ticks on wild donkeys in a Mediterranean nature reserve (Asinara National Park): diversity and risk factors

The Sardinian coloured donkey Equus asinus (Perissodactyla: Equidae) and its albino colour morph represent the wildlife species most typical of the island of Asinara. This Mediterranean island represents a favourable context for ticks and tick‐borne diseases; however, knowledge of the tick fauna on Asinara is scarce. A total of 106 Sardinian donkeys were inspected for tick infestation from June to November 2015. All ticks found were collected, classified by stage and sex, and identified to species level. The level of infestation of each donkey was determined; both the overall tick infestation and infestations of each detected species were classified on a scale of 1–3 to give an infestation score (IS). Overall, 256 hard ticks were collected from 60 of 106 donkeys (56.6%). Rhipicephalus bursa, Haemaphysalis punctata and Hyalomma marginatum (all: Ixodida: Ixodidae) infested 26.4%, 28.3% and 6.6% of donkeys, respectively. Different variables affected the IS. With reference to overall tick infestation, a higher IS was observed in donkeys grazing on grassland and Mediterranean shrubland and in albino donkeys compared with coloured donkeys. The collected ticks included species involved in the transmission of pathogens to humans, which highlights the risks for public health in a tourist destination such as Asinara National Park.     

Tick infestation of small mammals in an English woodland

Tick infestations on small mammals were studied from April to November, 2010, in deciduous woodland in southern England in order to determine whether co‐infestations with tick stages occurred on small mammals, a key requirement for endemic transmission of tick‐borne encephalitis virus (TBEV). A total of 217 small mammals was trapped over 1,760 trap nights. Yellow‐necked mice (Apodemus flavicollis) made up the majority (52.5%) of animals, followed by wood mice (A. sylvaticus) 35.5% and bank voles (Myodes glareolus) 12%. A total of 970 ticks was collected from 169 infested animals; 96% of ticks were Ixodes ricinus and 3% I. trianguliceps. Over 98% of ticks were larval stages. Mean infestation intensities of I. ricinus were significantly higher on A. flavicollis (6.53 ± 0.67) than on A. sylvaticus (4.96 ± 0.92) and M. glareolus (3.25 ± 0.53). Infestations with I. ricinus were significantly higher in August than in any other month. Co‐infestations with I. ricinus nymphs and larvae were observed on six (3.6%) infested individuals, and fifteen small mammals (8.9%) supported I. ricinus – I. trianguliceps co‐infestations. This work contributes further to our understanding of European small mammal hosts that maintain tick populations and their associated pathogens, and indicates that co‐infestation of larvae and nymph ticks does occur in lowland UK. The possible implications for transmission of tick‐borne encephalitis virus between UK ticks and small mammals are discussed.     

The lizards Lacerta agilis and L. vivipara as hosts to larvae and nymphs of the tick Ixodes ricinus

In this paper we provide quantitative information on the occurrence of larvae and nymphs of the tick Ixodes ricinus in populations of the lizards Lacerta agilis and L. vivipara . Levels of infestation were rather low, at least when compared with those of small mammals and sheep. Hence we suppose that lizards feed only a minor fraction of the total tick population.
Differences in tick loads among lizard subpopulations are probably attributable to difference in body size and mobility among the host groups.
Ticks exhibit a markedly clumped distribution on the lizards. This distribution pattern fits with the negative binomial distribution. The overdispersed distribution of tick larvae in the field and aspects of the lizards' behaviour are considered as factors which contribute to the observed infestation patterns.
Tick larvae were active throughout summer, with peak levels occurring during June-July. Nymphs were most numerous during May-June but almost absent during the summer months. Almost always ticks were attached near the lizards' forelimbs. Possible mortality resulting from tick infestation does not contribute significantly to the overall lizard mortality. Hence, these ectoparasites seem to have but a minor impact on the lizard populations.     

Impact of the experimental removal of lizards on Lyme disease risk

The distribution of vector meals in the host community is an important element of understanding and predicting vector-borne disease risk. Lizards (such as the western fence lizard; Sceloporus occidentalis) play a unique role in Lyme disease ecology in the far-western United States. Lizards rather than mammals serve as the blood meal hosts for a large fraction of larval and nymphal western black-legged ticks (Ixodes pacificus--the vector for Lyme disease in that region) but are not competent reservoirs for the pathogen, Borrelia burgdorferi. Prior studies have suggested that the net effect of lizards is to reduce risk of human exposure to Lyme disease, a hypothesis that we tested experimentally. Following experimental removal of lizards, we documented incomplete host switching by larval ticks (5.19%) from lizards to other hosts. Larval tick burdens increased on woodrats, a competent reservoir, but not on deer mice, a less competent pathogen reservoir. However, most larvae failed to find an alternate host. This resulted in significantly lower densities of nymphal ticks the following year. Unexpectedly, the removal of reservoir-incompetent lizards did not cause an increase in nymphal tick infection prevalence. The net result of lizard removal was a decrease in the density of infected nymphal ticks, and therefore a decreased risk to humans of Lyme disease. Our results indicate that an incompetent reservoir for a pathogen may, in fact, increase disease risk through the maintenance of higher vector density and therefore, higher density of infected vectors.     

Clinical, epidemiologic, and environmental surveillance for ehrlichiosis and anaplasmosis in an endemic area of northern California.

Two forms of tick-borne leukocytotropic rickettsioses have been recognized in California since the mid-1990s: human monocytic ehrlichiosis (HME) caused by Ehrlichia chaffeensis and human granulocytic anaplasmosis (HGA) caused by Anaplasma phagocytophilum. Between 1997 and 1999, two cases of HME and four cases of HGA were diagnosed in residents of southern Humboldt County, California. Environmental followup at case-patients' residences revealed dense populations of Ixodes pacificus ticks, particularly in grassy roadside areas. PCR evidence of A. phagocytophilum was detected in approximately 2.0% of I. pacificus; E. chaffeensis was not detected in any of 625 ticks tested. Serologic antibody to A. phagocytophilum was detected in two of 54 participants in a community epidemiologic study; one of these also had antibody to E. chaffeensis. Over 85% of study participants reported finding a tick on themselves in the preceding 12 mo. Residents of southern Humboldt County are at significant risk of tick bites and should take appropriate prevention measures to avoid infection with rickettsia and other tick-transmitted pathogens.