Experimental infection of the rabbit tick,<Emphasis Type="Italic"> Haemaphysalis leporispalustris</Emphasis>, with the bacterium<Emphasis Type="Italic"> Rickettsia rickettsii</Emphasis>, and comparative biology of infected and uninfected tick lineages

The present study consisted of two experiments that evaluated experimental infections of Haemaphysalis leporispalustris ticks by a Brazilian strain of Rickettsia rickettsii, and their effect on tick biology. In experiment I, ticks were exposed to R. rickettsii during the larval, nymphal or adult stages by feeding on rabbits (Oryctolagus cuniculus) needle-inoculated with R. rickettsii, and thereafter reared on uninfected rabbits for the entire next tick generation. Regardless of the tick stage that acquired the infection, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 1.3 to 41.7%), and were able to transmit R. rickettsii to uninfected rabbits, as demonstrated by rabbit seroconversion, guinea pig inoculation with rabbit blood, and PCR on rabbit blood. In Experiment II, ticks were exposed to R. rickettsii during the larval stage by feeding on rabbits co-infested with R. rickettsii-infected adult ticks, and thereafter reared on uninfected rabbits until the next generation of larvae. Again, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 3.0 to 40.0%), and were able to transmit R. rickettsii to uninfected rabbits. Thus, it was demonstrated that larvae, nymphs, and adults of H. leporispalustris were able to acquire and maintain the R. rickettsii infection by transstadial and transovarial transmissions within the tick population, with active transmission of the bacterium to susceptible rabbits by all parasitic stages. Analyses of biological parameters of uninfected and R. rickettsii-infected tick lineages were performed in order to evaluate possible deleterious effects of R. rickettsii to the infected tick lineages. Surprisingly, all but one of the four R. rickettsii-experimental groups of the present study showed overall better biological performance than their sibling uninfected control ticks. Results of the present study showed that H. leporispalustris could support infection by a high virulent strain of R. rickettsii for at least two generations, in which infected tick lineages tended to have better performance than uninfected ticks. Our results support a possible role of H. leporispalustris in the enzootic maintenance of R. rickettsii in Latin America, as previously suggested by earlier works.     

Spatial proximity and asynchronous refuge sharing networks both explain patterns of tick genetic relatedness among lizards,but in different years

A major question for understanding the ecology of parasite infections and diseases in wildlife populations concerns the transmission pathways among hosts. Network models are increasingly used to model the transmission of infections among hosts – however, few studies have integrated host behaviour and genetic relatedness of the parasites transmitted between hosts. In a study of the Australian sleepy lizard Tiliqua rugosa and its three‐host ixodid tick (Bothriocroton hydrosauri), we asked if patterns of genetic relatedness among ticks were best explained by spatial proximity or the host transmission network. Using synchronous GPS locations of over 50 adult lizards at 10 min intervals across the three‐month activity period, over 2 years, we developed two alternative parasite transmission networks. One alternative was based on the spatial proximity of lizards (at the centre of their home ranges), and the other was based on the frequency of asynchronous shared refuge use between pairs of lizards. In each year, adult ticks were removed from lizards and their genotypes were determined at four polymorphic microsatellite loci. Adult ticks collected from the same host were more related to each other than ticks from different hosts. Similarly, adult ticks collected from different lizards had a higher relatedness if those lizards had a shorter path length connecting them on each of the two networks we explored. The predictors of tick relatedness differed between years. In the first year, the asynchronous shared refuges network was the stronger predictor of tick relatedness, whereas in year two, the spatial proximity‐based network was the stronger predictor of tick relatedness. We speculate on how changing environmental conditions might change the relative importance of alternative processes driving the transmission of parasites.     

Vertical vs. horizontal transmission of the microbiome in a key disease vector,Ixodes pacificus

Vector‐borne pathogens are increasingly found to interact with the vector's microbiome, influencing disease transmission dynamics. However, the processes that regulate the formation and development of the microbiome are largely unexplored for most tick species, an emerging group of disease vectors. It is not known how much of the tick microbiome is acquired through vertical transmission vs. horizontally from the environment or interactions with bloodmeal sources. Using 16S rRNA sequencing, we examined the microbiome of Ixodes pacificus, the vector of Lyme disease in the western USA, across life stages and infection status. We also characterized microbiome diversity in field and laboratory‐collected nymphal ticks to determine how the surrounding environment affects microbiome diversity. We found a decrease in both species richness and evenness as the tick matures from larva to adult. When the dominant Rickettsial endosymbiont was computationally removed from the tick microbial community, we found that infected nymphs had lower species evenness than uninfected ticks, suggesting that lower microbiome diversity is associated with pathogen transmission in wild‐type ticks. Furthermore, laboratory‐reared nymph microbiome diversity was found to be compositionally distinct and significantly depauperate relative to field‐collected nymphs. These results highlight unique patterns in the microbial community of I. pacificus that is distinct from other tick species. We provide strong evidence that ticks acquire a significant portion of their microbiome through exposure to their environment despite a loss of overall diversity through life stages. We provide evidence that loss of microbial diversity is at least in part due to elimination of microbial diversity with bloodmeal feeding but other factors may also play a role.     

The effect of inflammatory and hypersensitive reactions,in response to the feeding of the tick Amblyomma variegatum,on the progression of experimental dermatophilosis infections

Initial infestations of Amblyomma variegatum larvae and nymphs, on rabbits and sheep respectively, produced inflammatory reactions in the host's skin; repeated infestations resulted in an increase in development of delayed type hypersensitive reactions. Dermatophilus congolensis cocci were applied in titrated doses to hosts at sites of inflammatory or hypersensitive reactions to ticks, and to control hosts with no exposure to ticks. We assessed the resulting infections for three weeks and found no significant difference between the infections on the three groups. We conclude that the local effects of the feeding of immature stages of this tick do not influence the pathogenesis of dermatophilosis.     

Auto-dissemination of commercially available fungal pathogens in a laboratory assay for management of the brown dog tick Rhipicephalus sanguineus

Rhipicephalus sanguineus is a canine tick that infests dogs throughout the world and is frequently found in homes and dog kennels. Management of this tick species is complicated by the presence of resistance to commonly utilized acaricides. Fungal formulations could provide a valuable alternative tool for management and are especially relevant indoors where detrimental environmental effects on fungal spores are of less concern. Two commercially available fungal formulations, one containing Metarhizium anisopliae and the other containing Beauveria bassiana, were compared for time to death and sporulation in nymphal ticks exposed for 60 min in treated filter paper packets. Beauveria bassiana exposure killed ticks faster than M. anisopliae exposure and B. bassiana was more likely to sporulate on tick cadavers than M. anisopliae. To determine whether infected ticks could disseminate fungus to their conspecifics, ticks were marked and treated with fungus before being placed with untreated ticks. Fungus was successfully transmitted from treated to untreated ticks. Mortality of ticks exposed to B. bassiana-exposed conspecifics occurred sooner than for those exposed to M. anisopliae-exposed conspecifics, indicating faster dissemination in the former. Therefore, although both formulations resulted in decreased longevity of ticks compared with the controls, the B. bassiana formulation holds the most promise for direct or indirect application with respect to brown dog tick management.     

Densities of Ixodes ricinus ticks (Acari: Ixodidae) on moorland vegetation communities in the UK

Unfed (questing) Ixodes ricinus ticks were collected by blanket dragging on a monthly basis from heather-dominated, Vaccinium-dominated and bracken-dominated vegetation communities from two different biogeographical regions of the UK (the Quantock Hills in Somerset, south west England and the North York Moors, north east England) throughout the spring and summer months of 1991 and 1992. Eighteen sites were monitored across the two regions and a total of 1920 blanket drags were carried out. Vaccinium sites showed high tick densities at all life stages, as did bracken sites. Significantly lower numbers of larval and nymphal ticks per drag were collected on heather sites than were collected on either Vaccinium (bilberry/whortleberry) or bracken sites, while similar numbers of adult ticks per drag were collected from each of the three vegetation communities. There was no significant difference between the mean numbers of any tick life stage collected on the Quantock Hills and those collected on the North York Moors on these vegetation communities or between the mean numbers of any tick life stage collected in 1991 and those collected in 1992 on these vegetation communities.     

Physiological Age of Field-collected Female Taiga Ticks, Ixodes persulcatus (Acari: Ixodidae), and their Infection with Borrelia burgdorferi Sensu Lato

In some studies the prevalence of tick infection (infection rate) and the intensity of infection are negatively correlated with unfed tick age (in the broad sense of this term). However, no special research has been carried out to consider the phenomenon thoroughly. The infection indices of the female taiga ticks, Ixodes persulcatus, infected with Borrelia burgdorferi s.l. were related to tick physiological age, an index that more precisely reflects tick physiological state than the time of tick collection in the field or the duration of tick survival under laboratory conditions. A novel quantitative technique of physiological age determination based on the evaluation of the ratios between sizes of the stable (scutum) and the changing (alloscutum) structures of the tick body was used. The age was estimated in accordance with the classical age-grade scale introduced by Balashov and a more fractional scale determined by the new technique. In total, 131 female ticks were examined for their infection and physiological age, 46 of which were infected with B. burgdorferi s.l. (mean infection rate 35.1%). The minimal intensity of infection was 0.4 bacterial cells per 100 fields of view whereas the maximal infection was 172 cells. There was no difference between the prevalence of infection in ticks of different physiological age. The intensity of infection obviously differed between ticks of different age groups in the scale introduced by Balashov but did not significantly differ between ticks of different age groups according to the fractional age-grade scale. The data concerning the relationships between Borrelia burgdorferi and unfed Ixodes ticks are considered.     

Seasonal dynamics of tick burden and associated Borrelia burgdorferi s.l. and Borrelia miyamotoi infections in rodents in a Dutch forest ecosystem

Ixodes ricinus ticks transmit Borrelia burgdorferi sensu lato (s.l.) as well as Borrelia miyamotoi. Larvae become infected when feeding on infected rodents, with horizontal transmission of B. burgdorferi and horizontal and vertical transmission of B. miyamotoi. We studied seasonal dynamics of infection rates of I. ricinus and their rodent hosts, and hence transmission risk of these two distinctly different Borrelia species. Rodents were live-trapped and inspected for ticks from May to November in 2013 and 2014 in a forest in The Netherlands. Trapped rodents were temporarily housed in the laboratory and detached ticks were collected. Borrelia infections were determined from the trapped rodents and collected ticks. Borrelia burgdorferi s.l. and B. miyamotoi were found in ticks as well as in rodents. Rodent density was higher in 2014, whereas tick burden as well as the Borrelia infection rates in rodents were higher in 2013. The density of B. miyamotoi-infected nymphs did not differ between the years. Tick burdens were higher on Apodemus sylvaticus than on Myodes glareolus, and higher on males than on females. Borrelia-infection rate of rodents varied strongly seasonally, peaking in summer. As the larval tick burden also peaked in summer, the generation of infected nymphs was highest in summer. We conclude that the heterogeneity of environmental and host-specific factors affects the seasonal transmission of Borrelia spp., and that these effects act more strongly on horizontally transmitted B. burgdorferi spp. than on the vertically transmitted B. miyamotoi.

     

Attachment site selection of ticks on roe deer, <Emphasis Type="Italic">Capreolus capreolus</Emphasis>

The spatio-temporal attachment site patterns of ticks feeding on their hosts can be of significance if co-feeding transmission (i.e. from tick to tick without a systemic infection of the host) of pathogens affects the persistence of a given disease. Using tick infestation data on roe deer, we analysed preferred attachment sites and niche width of Ixodes ticks (larvae, nymphs, males, females) and investigated the degree of inter- and intrastadial aggregation. The different development stages showed rather consistent attachment site patterns and relative narrow feeding site niches. Larvae were mostly found on the head and on the front legs of roe deer, nymphs reached highest densities on the head and highest adult densities were found on the neck of roe deer. The tick stages feeding (larvae, nymphs, females) on roe deer showed high degrees of intrastadial spatial aggregation, whereas males did not. Male ticks showed large feeding site overlap with female ticks. Feeding site overlap between larval-female and larval-nymphal ticks did occur especially during the months May–August on the head and front legs of roe deer and might allow pathogen transmission via co-feeding. Tick density, niche width and niche overlap on roe deer are mainly affected by seasonality, reflecting seasonal activity and abundance patterns of ticks. Since different tick development stages occur spatially and temporally clustered on roe deer, transmission experiments of tick-borne pathogens are urgently needed.     

Seasonal dynamics of the brown dog tick,Rhipicephalus sanguineus,on a confined dog population in Italy

This study evaluated the seasonal dynamics of Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) on naturally infested dogs in a private shelter in southern Italy. From March to May 2008, 39 autochthonous mixed‐breed young dogs and 10 beagles were enrolled in the study. From March 2008 until March 2009, every 21 ± 2 days, 11 body sites of each dog were checked for ticks. At each follow‐up, the number of ticks, their developmental stage, sex and location on the dog's body were recorded. Adult ticks were found throughout the year, but immatures were absent in January and February. The adult tick population increased from July to August, whereas the load of immatures increased in early July and peaked in September, which suggests that R. sanguineus develops one generation per year in this area. The mean number of immature ticks per infested dog was higher than that of adults from March to October 2008. Ears, interdigital areas and armpits were the most frequent attachment sites of adult ticks. At the last follow‐up, a total of 2266 ticks were collected and identified as R. sanguineus. The results suggest that R. sanguineus develops one generation per year in the study area, but that it infests dogs in all seasons. This information should be taken into account when planning control programmes against this tick species and the pathogens it transmits.     

Host specificity of a generalist parasite: genetic evidence of sympatric host races in the seabird tick Ixodes uriae

Due to the close association between parasites and their hosts, many ‘generalist’ parasites have a high potential to become specialized on different host species. We investigated this hypothesis for a common ectoparasite of seabirds, the tick Ixodes uriae that is often found in mixed host sites. We examined patterns of neutral genetic variation between ticks collected from Black‐legged kittiwakes (Rissa tridactyla) and Atlantic puffins (Fratercula arctica) in sympatry. To control for a potential distance effect, values were compared to differences among ticks from the same host in nearby monospecific sites. As predicted, there was higher genetic differentiation between ticks from different sympatric host species than between ticks from nearby allopatric populations of the same host species. Patterns suggesting isolation by distance were found among tick populations of each host group, but no such patterns existed between tick populations of different hosts. Overall, results suggest that host‐related selection pressures have led to the specialization of I. uriae and that host race formation may be an important diversifying mechanism in parasites.     

Major surface protein 1a effects tick infection and transmission of Anaplasma marginale

Anaplasma marginale, an ehrlichial pathogen of cattle and wild ruminants, is transmitted biologically by ticks. A developmental cycle of A. marginale occurs in a tick that begins in gut cells followed by infection of salivary glands, which are the site of transmission to cattle. Geographic isolates of A. marginale vary in their ability to be transmitted by ticks. In these experiments we studied transmission of two recent field isolates of A. marginale, an Oklahoma isolate from Wetumka, OK, and a Florida isolate from Okeechobee, FL, by two populations of Dermacentor variabilis males obtained from the same regions. The Florida and Oklahoma tick populations transmitted the Oklahoma isolate, while both tick populations failed to transmit the Florida isolate. Gut and salivary gland infections of A. marginale, as determined by quantitative PCR and microscopy, were detected in ticks exposed to the Oklahoma isolate, while these tissues were not infected in ticks exposed to the Florida isolate. An adhesion-recovery assay was used to study adhesion of the A. marginale major surface protein (MSP) 1a to gut cells from both tick populations and cultured tick cells. We demonstrated that recombinant Escherichia coli expressing Oklahoma MSP1a adhered to cultured and native D. variabilis gut cells, while recombinant E. coli expressing the Florida MSP1a were not adherent to either tick cell population. The MSP1a of the Florida isolate of A. marginale, therefore, was unable to mediate attachment to tick gut cells, thus inhibiting salivary gland infection and transmission to cattle. This is the first report of MSP1a being responsible for effecting infection and transmission of A. marginale by Dermacentor spp. ticks. The mechanism of tick infection and transmission of A. marginale is important in formulating control strategies and development of improved vaccines for anaplasmosis.     

Seasonal Population Dynamics of Ixodes Ticks and Tick-Borne Encephalitis Virus

Seasonality of the epidemic and epizootic processes of tick-borne encephalitis (TBE) depend on the period of activity of ixodid ticks Ixodes persulcatus Schulze and I. ricinus Linnaeus, which are the main reservoirs and vectors of TBE virus, and also on the process of their activation. The period of activity is the period during which the ticks occur in the active state. Activation is the transition into this state of ticks that moulted from the preceding stage and completed post-moulting development. For I. persulcatus, the first adult ticks generally emerge between April 10 and May 9. Under a variety of natural conditions, activation of adult I. persulcatus after wintering lasts for 45–86 days and this period may be even longer in certain areas of the Far East. The period during which one-half of the entire tick population becomes activated (AT₅₀) comprises no more than 10–20 days. In adult I. ricinus ticks the activation period may last even longer than in I. persulcatus. The data on duration of the period of activity and on activation of larval and nymphal stages of both tick species were considered. Ticks exhausting their nutrient reserves and failing to find a host die quickly. The period during which 50% of the entire tick population die under natural conditions is designated LT₅₀. The main types of I. persulcatus and I. ricinus seasonal activity within their species ranges were reviewed. Data on the relationship between TBE virus reproduction in a natural focus and physiological age, pattern of activation, and seasonal changes in age structure of the tick population were analyzed. Seasonal changes in the prevalence of infection among active unfed adult ticks in a natural population are determined by virus content in individual ticks at the moment of their activation and also by the duration of subsequent virus persistence (the rate of virus loss) in ticks. Apparently, the opportunity and frequency of horizontal TBE virus transmission under natural conditions, change during the season of tick activity.     

Detection of Rickettsia and Anaplasma from hard ticks in Thailand

We collected a total of 169 adult hard ticks and 120 nymphs from under the leaves of plants located along tourist nature trails in ten localities. The results present data examining the vector competence of ticks of different genera and the presence of Rickettsia and Anaplasma species. The ticks belonged to three genera, Amblyomma, Dermacentor, and Haemaphysalis, comprising 11 species. Rickettsia bacteria were detected at three collection sites, while Anaplasma bacteria were detected at only one site. Phylogenetic analysis revealed new rickettsia genotypes from Thailand that were closely related to Rickettsia tamurae, Rickettsia monacensis, and Rickettsia montana. This study was also the first to show that Anaplasma bacteria are found in Haemaphysalis shimoga ticks and are closely related evolutionarily to Anaplasma bovis. These results provide additional information for the geographical distribution of tick species and tick‐borne bacteria in Thailand and can therefore be applied for ecotourism management.     

Autophagy-related genes from a tick,Haemaphysalis longicornis

Ticks are gorging-fasting organisms; their life cycle is characterized by alternate off-host (starvation) and on-host (meal) conditions. Their generation time is estimated in several years and many ticks spend more than 95% of their life off the host. They seem to have a unique strategy to endure the off-host state for a long period. Thus, we focused on autophagy, which is induced by starvation and is essential for extension of the lifespan, and hypothesized that ticks also have a system of autophagy to overcome the starved condition. Recently, we showed the existence of a homologue of an ATG gene, ATG12, and its expression pattern from nymphal to adult stages in a three-host tick, Haemaphysalis longicornis. The expression level of HlATG12 was downregulated at the beginning of feeding and was highest at 3 months after engorgement. In addition, the HlAtg12 protein was localized to the region around granule-like structures within midgut cells of unfed adults. These results indicate that HlATG12 functions during unfed stages. Here, a potential role of autophagy in unfed ticks is discussed with regard to reports in other animals, such as yeast, mammal, and fruit fly.

Addendum to: Umemiya R, Matsuo T, Hatta T, Sakakibara S, Boldbaatar D, Fujisaki K. Cloning and characterization of an autophagy-related gene, ATG12, from the three-host tick Haemaphysalis longicornis. Insect Biochem Mol Biol 2007; 37:975-84     

Species,developmental stage and infection with microbial pathogens of engorged ticks removed from dogs and questing ticks

Research into tick‐borne diseases implies vector sampling and the detection and identification of microbial pathogens. Ticks were collected simultaneously from dogs that had been exposed to tick bites and by flagging the ground in the area in which the dogs had been exposed. In total, 200 ticks were sampled, of which 104 came from dogs and 96 were collected by flagging. These ticks were subsequently examined for DNA of Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Rickettsia spp. and Babesia canis. A mixed sample of adult ticks and nymphs of Ixodes ricinus (Ixodida: Ixodidae) and Haemaphysalis concinna (Ixodida: Ixodidae) was obtained by flagging. Female I. ricinus and adult Dermacentor reticulatus (Ixodida: Ixodidae) ticks dominated the engorged ticks removed from dogs. Rickettsia spp. were detected in 17.0% of the examined ticks, A. phagocytophilum in 3.5%, B. canis in 1.5%, and B. burgdorferi s.l. in 16.0%. Ticks with multiple infections were found only among the flagging sample. The ticks removed from the dogs included 22 infected ticks, whereas the flagging sample included 44 infected ticks. The results showed that the method for collecting ticks influences the species composition of the sample and enables the detection of a different pattern of pathogens. Sampling strategies should be taken into consideration when interpreting studies on tick‐borne pathogens.     

Life cycle and seaonal development of postembryonicArgas reflexus (Acari: Argasidae) at two thermally different locations in Central Europe

Seasonal development was investigated in the pigeon tick,Argas reflexus (F.) over a 5-year period. The ticks were kept in desiccators at two deposition sites with different temperature conditions: a warmer attic and a cooler outdoor aviary. The life cycle ofA. reflexus consists of the egg, larva, a variable number of two to four nymphal instars and the adult stage. In the cooler aviary, the ticks passed, on average, fewer nymphal instars than in the attic. At both locations, ecdysis of the nymphs and adults occurred only during the summer months, with peak numbers of ticks finishing the moult in August. This consistent pattern was evident irrespective of the feeding date of the preceding developmental stage or the year of observation. The results strongly suggest that nymphs II, nymphs I and larvae fed later than in mid-July, August or September, respectively, entered a state of diapause and, thus, overwintered in the engorged state.Argas reflexus nymphs II from a laboratory stock that were deposited inside the attic showed a remarkably different seasonal pattern of development, even more than 1 year after their deposition. This suggests that a circannual rhythm may be involved in the ticks' seasonal timing. Mortality of the engorged ticks (from repletion to ecdysis of the following stage/instar) was below 1.5% in most cases, irrespective of the season and the location. Unfed larvae survived for a maximum of one year inside the attic, whereas the median survival period of unfed nymphs was at least 3 years at the same location. Based on the present results, the generation time from (F₁) egg deposition to oviposition in the F₂ generation might be 3–11 years in Central EuropeanA. reflexus, depending on the course of development (two or three nymphal instars) and the number of gonotrophic cycles (probably up to six) of the F₁. The life span of a single tick might take approximately 7–11 years or even longer.     

Role of cuticular lipids and water-soluble compounds in tick susceptibility to Metarhizium infection

The arthropod cuticle acts as a physiochemical barrier protecting the organism from pathogens' entry. Entomopathogenic fungi actively penetrate the cuticles of arthropod hosts and are therefore directly affected by cuticle composition. Previously we have observed that Metarhizium spp. developing on resistant ticks ultimately die without penetrating tick's cuticle, suggesting that the cuticles of resistant ticks have antifungal compounds. In the present study, lipids and water-soluble cuticular components were extracted from engorged female tick cuticles, of one susceptible and one resistant tick species to Metarhizium spp. While conidia exposed to lipids from the susceptible tick, Rhipicephalus annulatus, germinated and differentiated into appressorium, conidia exposed to lipids from the resistant tick, Hyalomma excavatum, were inhibited. Soluble cuticular component extracts from both susceptible and resistant ticks stimulated conidial germination but not appressorium differentiation. A comparative analysis of the fatty acid profile in lipid extract of each tick exhibited similar compositions, but the relative abundance of C16:0, C18:0, C18:1ω9C and C20:0 was 2–5 times higher in the extracts from resistant ticks. All of these fatty acids inhibited conidial germination in vitro at 1% and 0.1% w/v concentration, but C20:0 stimulated appressorium differentiation at low concentration. This is the first report demonstrating a possible link between the presence of antifungal compounds in a specific concentration in tick cuticle and tick resistance to infection.     

The local effect of hypersensitive or inflammatory reactions to nymphal Amblyomma variegatum on simultaneous infections with Dermatophilus congolensis

Amblyomma variegatum nymphs were applied to sites infected with Dermatophilus congolensis on eight rabbits. Four rabbits were previously sensitized to the fecding of nymphal A. variegatum to produce hypersensitive reactions to the tick feeding; the remaining four rabbits had no previous exposure to nymphal A. variegatum and produced inflammatory reactions to the tick feeding.The resulting dermatophilosis infections were assessed for three weeks and there was a correlation between the position of the inflammatory tick attachment sites and the foci of infection. There was a significant increase in the lesions at sites with inflammatory reactions to the ticks, compared with sites not exposed to tick feeding; these differences appeared to be due to individual variation in the host response and were not sustained throughout the assessment.