Histopathology of <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> (Acari: Ixodidae) ticks fed on resistant hosts

Histological features of Rhipicephalus sanguineus ticks fed on dog, a non resistant host, and on guinea pig, a resistant host, were compared. Unfed ticks and ticks from each host species were collected during first and third infestation and processed for histology. Many ticks from guinea pigs, especially during third infestation, were unattached, dehydrated and small. Only the midgut of ticks fed on guinea pigs had host leukocytes. Vacuolization of midgut cells was observed in all ticks, with exception of those fed on dogs for more than 96 h. Ticks of guinea pigs, particularly from third infestation, had vacuolated tracheae and swelling of malpighian tubules. Solely ticks from third infestation of guinea pigs displayed vacuolization of oocytes. Ticks fed on guinea pigs also had an increased number of guanine spherules. Observed alterations in ticks from guinea pigs are discussed.     

Tick infestation risk and <Emphasis Type="Italic">Borrelia burgdorferi</Emphasis> s.l. infection-induced increase in host-finding efficacy of female <Emphasis Type="Italic">Ixodes ricinus</Emphasis> under natural conditions

An investigation of the risk of human tick infestation, together with the prevalence of Borrelia burgdorferi s.l. infection, was conducted in a sylvatic habitat in western Germany to provide data needed for future risk-benefit evaluations of acaricides used for clothing impregnation. Additionally, data were collected on behavioural changes in Borrelia burgdorferi s.l.-infected adult female I. ricinus ticks and the possible impact of such changes on host-finding efficacy. The risk of I. ricinus-infestation was determined by collecting from the protective clothing of volunteers and by dragging in known tick-infested sites in the Kühkopf Mountain area, Koblenz, Germany, from June through October 2006. The overall tick infestation rate per person per hour was 7.4 ± 5.5, with the following sex- and stage-specific differences: males 0.32 ± 0.37, females 1.1 ± 1.2, nymphs 3.6 ± 4.4, larvae 2.4 ± 3.5. Concurrent dragging revealed an average 19.4 ± 16.2 times higher infestation rate as well as a markedly lower infection rate with borreliae in adult I. ricinus ticks when compared to ticks collected from exposed human volunteers. Although the difference in infection rates was statistically significant (P < 0.023) only in adult female ticks, our data indicate that B. burgdorferi s.l. infection may increase host-finding efficacy in adult I. ricinus. The overall exposure risk was 1.0 B. burgdorferi s.l.-infected ticks per person per hour of exposure, or 0.25 ticks per 100 m walking distance in the study area.     

Evaluation of the one-side tick counting technique and of the level of infestation of bovines with Rhipicephalus microplus

Counting ticks on one side of a bovine has been widely used to estimate the overall number of ticks; however, the accuracy of this method has not been determined. This work aimed to evaluate the one-side technique for counting ticks, identify bovines with a higher level of infestation, and determine the prevalence of infestation of adults and calves. To evaluate the one-side technique, ticks were counted on both sides of 352 bovines from three farms in nine months, and total numbers were correlated with the numbers counted on the left sides. The intraclass correlation coefficients reached values >0.99 for all farms, independent of the season. These results demonstrated that counting ticks on one-side and multiplying by 2 is a reliable method for estimating the overall number of ticks. To evaluate the level of infestation of various bovines, ticks were counted monthly, for 12 months, on the same bovines from seven farms. An animal was considered highly infested if the Anscombe residuals from a negative binomial GLM were ≥4, at least 2×. The number of bovines with infestation levels higher than expected varied among farms from zero to 3. Using this method, it is possible to evaluate the most infested bovines in order to remove them from the herd. The prevalence of infestation in calves reached 100% in five of the seven farms and 3- to 15-month-old calves had significantly higher infestation than adults.

     

PCR identification and phylogenetic analysis of the medically important dust mite <Emphasis Type="Italic">Suidasia medanensis</Emphasis> (Acari: Suidasiidae) in Malaysia

Hard ticks are a perennial problem in livestock systems throughout Mexico. No data are currently available on tick prevalence, infestation intensity and population dynamics for sheep in the humid tropics of Mexico. Blackbelly sheep (n = 30) in Tabasco state, Mexico, were examined every 3 weeks for 1 year, and all Ixodidae ticks were counted and removed for analysis. Tick species were identified, infestation prevalence and intensity calculated per animal, and infestation per body zone determined. Overall infestation on the studied animals was 51.9%. Four tick species were identified (Amblyomma mixtum, A. imitator, Rhipicephalus microplus and R. annulatus), the most abundant being A. mixtum (94.9%). Prevalence was highest during the northwinds season (61.9%), followed by the dry (48.5%) and rainy (47.3%) seasons; however, the intensity (2.01–2.07 ticks/sheep) did not differ between seasons. Infestation was most frequent in certain zones including the axilla, crotch, udder, abdomen, thorax and rib area. Sheep in the humid tropics of Tabasco, Mexico, are parasitized by four hard tick species and prevalence is highest in the northwinds season. The present data constitute an important baseline for developing sustainable tick control programs for sheep in the humid tropics of Mexico.     

Competition,facilitation or mediation via host? Patterns of infestation of small European mammals by two taxa of haematophagous arthropods

1. We studied the effect of flea infestation on the pattern of tick (Ixodes ricinus and Ixodes trianguliceps) infestation on small mammals. 2. We asked (1) whether the probability of an individual host being infested by ticks was affected by its infestation of fleas (number of individuals and species) and (2) whether the abundance and prevalence of ticks in a host population was affected by the abundance, prevalence, level of aggregation, and species richness of fleas. 3. The probability of a host individual being infested by ticks was affected negatively by flea infestation. At the level of host populations, flea abundance and prevalence had a predominantly positive effect on tick infestation, whereas flea species richness had a negative effect on tick infestation. 4. The effect of flea infestation on tick infestation was generally greater in I. ricinus than in I. trianguliceps, but varied among host species. 5. It can be concluded that the effect of fleas on tick infestation of small mammals may be either negative or positive depending on the level of consideration and parameters involved. The results did not provide support for direct interactions between the two ectoparasite taxa, but suggested population and community dynamics and the defence system of the hosts as possible factors.     

Changes in immunity to Ixodes ricinus by rabbits infested at different levels

Abstract. Two groups of rabbits were infested twice with different numbers of Ixodes ricinus adults: one group (high infestation) with twenty-five females and twenty-five males and the other group (low infestation) with five pairs. A third infestation was performed in both groups with fifteen adult pairs. Tick biology was monitored for resistance effects. At the second infestation, the feeding and the egg production were more perturbed in ticks fed on high infestation rabbits. The embryogenesis was only affected in ticks from high infestation rabbits. At the third infestation, resistance was increased only in low infestation rabbits, which became more resistant than high infestation rabbits. The blastogenic response of peripheral blood lymphocytes and antibody production against ticks were assessed. A salivary gland extract and an integumental antigen from Lricinus adult females were able to initiate lymphocyte proliferation. The response was significantly higher in high infestation rabbits, especially at the end of the second infestation, and higher in low infestation rabbits during the third infestation. Non-specific proliferation with concanavalin A was temporarily decreased in both rabbits groups during the first and the second infestations. Specific antibody response to salivary and integument antigens were always the highest in high infestation rabbits. The involvement of tick-induced immunosuppression is discussed.     

C3 levels in the sera of rabbits infested and reinfested withIxodes ricinus L. and in midguts of fed ticks

Serum C3 levels of rabbits infested 3 times withIxodes ricinus L. females and C3 in midgut extracts of fed ticks have been measured by a single radial immunodiffusion test.From the first tick attachment, the mean serum C3 level of hosts increased. A peak of C3 occurred 6 days after the beginning of each infestation and was highest during the third infestation (about 8 times more pronounced than the level measured before the first). After the end of all infestations of the rabbits, the serum C3 level decreased and approached normal levels.Modifications of serum C3 levels during reinfestations influenced C3 contents in the blood meal of fed ticks. Midguts of ticks fed during the third infestation contained more C3 than midguts of ticks of the same engorged weights fed during the first or second infestations.     

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.     

Autochthonous and migratory birds as a dispersion source for Ixodes ricinus in southern Italy

The present study was carried out in a protected wooded area, which is part of the Parco Regionale Gallipoli Cognato Piccole Dolomiti Lucane, one of the most important ecological reserves in southern Italy. From April 2010 to April 2011, 212 birds, comprising 22 species from 12 families, were captured and examined for ticks. A total of 75 (35.4?%) birds were found infested by ticks, with 451 ticks being collected. All ticks were identified as Ixodes ricinus, of which 241 (53.4?%) were larvae and 210 nymphs (46.6?%). The highest intensity of infestation was found in April 2010, when 117 ticks were retrieved on 25 birds. No ticks were found on birds (n?=?5) netted in December 2010. High infestation rates were recorded on blackbirds (Turdus merula) (90 %; 29 birds examined) and on mistle thrushes (Turdus viscivorus) (100?%; 2 birds examined). The highest intensity of infestation by larvae was found on wrens (5.6 larvae/bird) and by nymphs on mistle thrushes (11.5 nymphs/bird). Temperature and number of hours of light showed to influence the activity of larvae and nymphs. These data support the notion that birds may be responsible for the heterogeneous distribution of I. ricinus in Europe, thus playing a role in the epidemiology of certain tick-borne pathogens.     

Ecological implications on the aggregation of <Emphasis Type="Italic">Amblyomma fuscum</Emphasis> (Acari: Ixodidae) on <Emphasis Type="Italic">Thrichomys laurentius</Emphasis> (Rodentia: Echimyidae), in northeastern Brazil

We investigated the Amblyomma fuscum load on a pullulating wild rodent population and the environmental and biological factors influencing the tick load on the hosts. One hundred and three individuals of Thrichomys laurentius were caught in an Atlantic forest fragment in northeastern Brazil, as part of a longitudinal survey on ticks infesting non-volant small mammals. Ticks (n = 342) were found on 45 individuals and the overall mean intensity of infestation was 7.6 ticks per infested rodent. Ticks were highly aggregated in the host population and the negative binomial distribution model provides a statistically satisfactory fit. The aggregated distribution was influenced by sex and age of the host. The microhabitat preference by T. laurentius probably increases contact opportunities between hosts and aggregated infesting stages of the ticks and represents important clues about the habitat suitability for A. fuscum.     

Rhipicephalus appendiculatus feeding on rabbits and cattle: Salivary-gland responses to varying host resistance

AdultRhipicephalus appendiculatus ticks were fed as three sequential infestations on both rabbits and cattle. The feedings at first infestation on naive hosts were optimum for the ticks, whereas at third infestation the hosts were resistant, as expressed by reduced tick feeding performance. Ticks from naive and resistant hosts were examined for histological differences of salivary glands. In ticks fed on resistant rabbits there was a large increase in the synthesis of glycoprotein secretory granules in thec ₁ cells compared with ticks fed on naive rabbits. In ticks fed on naive and resistant cattle, the activity of thec ₁ cells was less than in ticks fed on naive and resistant rabbits. It was concluded that the salivary glands are able to respond selectively to conditions at the feeding site, and that this may be advantageous to the tick.     

Footbath acaricide treatment to control cattle infestation by the tick Amblyomma variegatum

Previous studies have shown that about 90% of adult Amblyomma variegatum Fabricius (Acari: Ixodidae) picked up daily by grazing cattle are still attached to the interdigital areas in the evening, when the animals return from pasture. It was therefore postulated that a targeted treatment, designed to kill the ticks attached to the feet, would limit infestation of the predilection sites. Footbaths filled with various pyrethroid formulations were used over 3 years, at the beginning of the rainy season (from mid-May to the end of July), to assess the efficacy of such a control method. It proved efficient in preventing the ticks from attaching to the predilection sites. Although five to 12 A. variegatum adults attached to each treated animal daily, and although the tick burden of the predilection sites of control cattle increased each day by four to 10 ticks, the average infestation of the predilection sites of treated cattle that were initially highly infested (over 100 ticks/animal) continuously decreased to reach a level of about 10-30 ticks/animal after 6-8 weeks of treatment. In herds with a lower initial tick burden (40-70 ticks/animal) this level was obtained within 2-3 weeks and the mean infestation subsequently remained consistently low. Footbath treatment carried out every other day during the adult peak infestation period should therefore greatly limit losses due to ticks. This method was appreciated by traditional livestock farmers, essentially because it is not time-consuming and because it requires only c. 200 mL aqueous formulation per animal at each passage. The cost of the acaricide needed to treat one animal during the peak infestation period was assessed at c. euro 0.20. This control method might also have an impact on some species of tsetse flies and mosquitoes, thereby contributing to trypanosomiasis and malaria control.     

Microhabitat choice and host-seeking behaviour of the tuatara tick,

Understanding the factors that influence patterns of ectoparasite infestation within wildlife populations involves knowledge of the mechanisms that influence host infestation. For ectoparasitic ticks, knowing where ticks might occur in the off-host environment and how they locate their hosts is essential to understanding patterns of ectoparasite infestation. The tuatara tick (Amblyomma sphenodonti) parasitises the tuatara (Sphenodon punctatus) on Stephens Island, New?Zealand. We completed a series of laboratory microcosm experiments to examine daily activity patterns, microhabitat preferences and host-seeking behaviour by Amblyomma sphenodonti. Firstly, to determine the diel activity pattern of ticks, we observed the behaviour of ticks every 2?h over a 48-h period. We then tested the preferences of ticks for soil moisture, soil texture and shade by offering different pairs of substrate conditions. Last, to determine what cues ticks used to locate their hosts, we tested the response of ticks to filter paper infused with host scent or excrement. Ticks were most active at night. They also showed a significant preference for moister, coarser and shaded substrates 12 h after the start of the experiment. Ticks did not show an immediate response to either of the two host stimuli, but after 12 h showed a significant preference for host scent and avoided host excreta. We suggest that the microhabitat preferences of ticks reflect conditions within host refuges (burrows), and that the delayed response to host odour suggests ticks could use host scent to identify substrates frequented by hosts.     

Feeding performance ofAmblyomma variegatum (Acarina: Ixodidae) fed repeatedly on rabbits

Rabbits infested with different stages ofAmblyomma variegatum Fabricius, 1794 became resistant to subsequent infestations by the same tick. Resistance was manifested by a reduction of 73.6% in the mean engorged weight of female ticks by the 3rd infestation. By the 5th infestation, only 70% of the nymphs engorged and their mean engorged weight was 57.7% of that of nymphs fed on tick-naive control rabbits. In the case of larvae, there was a 22.8% reduction in their mean engorged weight by the 6th infestation. Based on increases in body length while feeding on tick-naive rabbits, the nymphs could be divided into four feeding categories, i.e. Nl (unfed), N2, N3 and N4 (increasing states of engorgement). While 92–96% of ticks which dropped from susceptible rabbits fitted into feeding category N4, only 28% of those that dropped from tick-resistant rabbits fitted into that category. The remainder of the ticks fitted into categories N3 (60%) and N2 (12%). The majority of those ticks with reduced weight developed into adults which had an atypical scutal ornamentation pattern, in that an additional pair of lateral spots was regularly observed on the males. The females of such ticks deposited small numbers of eggs from which no larvae hatched.     

The effects of tick numbers and intervals between infestations on the resistance acquired by guinea-pigs to adults of Rhipicephalus evertsi evertsi (Acari: Ixodidae)

Guinea-pigs were infested three times at short (1 week) intervals or long (10 week) intervals between successive infestations with low (1), medium (8) and high (15) numbers of adult Rhipicephalus evertsi evertsi. To compare the resistance developed by the hosts at short and long intervals between infestations, a challenge (fourth) infestation was performed with the high number of ticks. Resistance was assessed by comparing the mean weight of engorged female ticks that dropped from the hosts. Concentrations of beta globulins in the host sera were also monitored. Different tick Ioads (low, medium and high) and infestation intervals had a similar influence on the reduction in weight of the females which was between 60–70% after the final challenge. However, the concentration of beta globulins, was highest in the guinea-pigs exposed to medium and high numbers of ticks with long infestation intervals, probably because of an increase in the production of protective antibodies in response to more intensive antigenic challenge. The relationship between engorgement weight and beta globulin levels in host sera is discussed.     

Acquired resistance in dogs to repeated infestation with Ixodes scapularis (Acari: Ixodidae) reduces tick viability and reproductive success

The purpose of this study was to determine whether dogs develop acquired resistance to adult Ixodes scapularis infestation in an experimental model. Five dogs were each infested with ten mating pairs of ticks every week for 7 consecutive weeks, another five dogs were each infested with ten mating pairs once every 2 weeks for 10 weeks and four dogs served as controls not exposed to ticks. All ticks were allowed to feed to repletion and were collected only after dropping from the host. Several variables were measured to determine the extent of blood feeding success. Regression analysis indicated that the engorgement success, survival and mean tick engorgement weight declined with repeated infestation in both groups of dogs (p<0.05). Tick oviposition as well as the F1 viability declined with each successive infestation in both groups. These results suggest that repeated infestation with I. scapularis elicits a protective immune response against tick feeding and could serve as a limiting factor in the spread and transmission of Borrelia burgdorferi.     

Attractivity of cattle infested by Amblyomma variegatum (Acari: Ixodidae) for conspecific adult ticks from the field in Guadeloupe

Four field experiments were conducted with creole cattle in Guadeloupe to study the attractivity for adult ticks of animals previously infested with males of Amblyomma variegatum producing aggregation attachment pheromones (AAPs). In each experiment, two groups of cattle were used; the first group was infested with adult A. variegatum and the second group was kept free of ticks and pheromones by acaricidal treatment and by washing the hair and skin of previously infested sites. Both groups were then exposed to natural infestation by ticks present in the environment or by ticks bred in the laboratory and released on the pasture. The number of additional ticks infesting animals were compared between the treated and control groups. There were no significant differences between both groups in the numbers of new male ticks infesting the animals during the first days following the beginning of the experiment. Thereafter, comparison of the slopes of infestation indicated that infested cattle were no more attractive for male ticks than uninfested hosts. Uninfested cattle were spontaneously and rapidly infested by male ticks. It is concluded that carbon dioxide or another host component was a major attractant for A. variegatum males. Female ticks attached on predilection sites exclusively in the presence of AAP-producing males, i.e. 5–10 days after the attachment of the first males. Based on these results we postulate that slow-release devices impregnated with pheromones have no additional attractive effect on A. variegatum males under Caribbean conditions. However, they may be useful in inducing the attachment of females, but only in the first days preceding the arrival of pioneer AAP-producing males. © Rapid Science Ltd. 1998     

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.     

Hyalomma ticks on northward migrating birds in southern Spain: Implications for the risk of entry of Crimean‐Congo haemorrhagic fever virus to Great Britain

Crimean‐Congo haemorrhagic fever virus (CCHFV) is a zoonotic virus transmitted by Hyalomma ticks, the immature stages of which may be carried by migratory birds. In this study, a total of 12 Hyalomma ticks were recovered from five of 228 migratory birds trapped in Spring, 2012 in southern Spain along the East Atlantic flyway. All collected ticks tested negative for CCHFV. While most birds had zero Hyalomma ticks, two individuals had four and five ticks each and the statistical distribution of Hyalomma tick counts per bird is over‐dispersed compared to the Poisson distribution, demonstrating the need for intensive sampling studies to avoid underestimating the total number of ticks. Rates of tick exchange on migratory birds during their northwards migration will affect the probability that a Hyalomma tick entering Great Britain is positive for CCHFV. Drawing on published data, evidence is presented that the latitude of a European country affects the probability of entry of Hyalomma ticks on wild birds. Further data on Hyalomma infestation rates and tick exchange rates are required along the East Atlantic flyway to further our understanding of the origin of Hyalomma ticks (i.e., Africa or southern Europe) and hence the probability of entry of CCHFV into GB.     

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.