Attachment kinetics of the adult tick Amblyomma variegatum to cattle

At the beginning of the 1999 rainy season, three traditional cattle herds were monitored for 48 days while grazing in the bushy savannah of southwestern Burkina Faso. Cattle in each herd were caught on several occasions each day and the attached ticks were counted. This confirmed that Amblyomma variegatum Fabricius (Acari: Ixodidae) adults picked up in the pastures mainly attach to the interdigital areas (87% of the 791 ticks captured), and reach the predilection sites later (chest and udder/inguinal area) when the animals lie down. As many females as males attached to the hosts, but the seasonal distribution was very heterogeneous, with only a few females attaching as long as the humidity rate remained low. It is suggested that this prevents eggs from being laid when conditions are not optimal for their survival and that of the larvae. Ticks attached all day but the number picked up hourly and daily varied greatly according to their density on the pasture. As a general trend, confirmed by another study carried out in 2005, the number of ticks picked up daily increased from less than one tick/animal/day, before the onset of the rainy season, to 6.5 (+/- 1.5) ticks/animal/day on average during the infestation peak, which lasted 6-8 weeks, until early or mid-July. The number then decreased to less than one tick/animal/day from the end of July onwards. The infestation on the predilection sites followed the same trend, with a daily tick burden increase of three to five A. variegatum adults, depending on herd and year, during the infestation peak.     

Invasion of West African cattle by the tick Amblyomma variegatum

Studies in Cameroon and Burkina Faso examined the invasion process of cattle by adult Amblyomma variegatum Fabricius (Acari: Ixodidae) ticks. Nearly all the ticks picked up in the pasture during grazing were found on the limb ends, near the hooves, where they temporarily attached. Then when the cattle lay down, the ticks moved from the feet towards the predilection sites, where they attached definitively. Many ticks disappeared during this displacement. All the female ticks and approximately 70% of the males were thus unable to attach to the predilection sites as long as the pioneer males had not attached and started to produce attraction-aggregation-attachment pheromones. Nevertheless, A. variegatum females and males attached to the feet in similar numbers during grazing, whether the cattle were already infested or not, indicating that stimuli originating from the hosts are powerful enough to attract both sexes. After attachment of the pioneer males, the number of ticks that successfully reached the predilection sites increased. However, even on infested animals, 40-50% of A. variegatum ticks found near the hooves after the grazing periods disappeared during the night following their capture. When moving from the temporary attachment sites towards the final ones, one-third of the ticks changed the individual host. Considering this two-stage infestation process, it is suggested that a targeted tick control, using a foot-bath, might greatly reduce cattle infestation. In particular, it could be effective in traditional herds, with animals grazing permanently during the day, lying down only once back in the night pen.     

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     

Amblyomma variegatum and associated diseases in the Caribbean: strategies for control and eradication in Guadeloupe

Amblyomma variegatum, introduced into Guadelopue 150 years ago, has recently spread in the Lesser Antilles and threatens North America. Two important diseases are associated with the tick: heartwater and dermatophilosis. Heartwater occurs in Guadeloupe, Marie-Galante and Antigua; acute dermatophilosis exists almost everywhere the tick is present. Both are very pathogenic for upgraded or newly-infested cattle. After 15 years of A. variegatum control in Guadeloupe, a balance is established between a tick population maintained at a low level by spraying acaricides and an animal population either completely resistant to heartwater and dermatophilosis (creole cattle) or regularly treated against ticks (upgraded cattle). An eradication campaign against A. variegatum in Guadeloupe, to avoid the spread of the associated diseases, appears technically difficult but possible, economically profitable, but socially completely utopian. We suggest for Guadeloupe a reinforced control of the tick with a persistent acaricide, hoping that a general decrease of the tick infestation rate on cattle will eliminate heartwater and acute dermatophilosis.     

Monthly dynamics of ticks (Acari: Ixodida) infesting N'Dama cattle in the Republic of Guinea

The occurrence of ixodid ticks on N'Dama cattle was studied in the Republic of Guinea between June 1994 and May 1995. Monthly tick collections were performed on 80 animals from 14 villages located in Dabola, Kouroussa and Dinguiraye prefectures. A total of 19,804 ticks was collected and classified using standard taxonomic keys. The following tick species were identified: Amblyomma variegatum, Hyalomma marginatum rufipes, Hyalomma trunctum, Hyalomma nitidum, Rhipicephalus lunulatus, Rhipicephalus muhsamae, Rhipicephalus senegalensis, Rhipicephalus sulcatus, Rhipicephalus turanicus, Boophilus annulatus, Boophilus geigyi. Boophilus spp. were the most numerous adult ticks (57.1%), Am. variegatum adults constituted 27.4%, while 12.4% were Rhipicephalus spp. and 2.5% Hyalomma spp. Rhipicephalus turanicus and Hyalomma nitidum were recorded for the first time in the country. Am. variegatum and Boophilus spp. were present throughout the year, whereas Am. variegatum adults showed a peak during the rainy season between April and September. Immature stages collected belonged exclusively to the genera Amblyomma and Boophilus. Am. variegatum larvae and nymphs showed a peak during the dry season (October-March); no significant variation between seasons was observed for Boophilus immatures. A significantly higher infestation of cattle by Rhipicephalus spp. was found in Dabola and Kouroussa prefectures, located in the southern part of the study area, with similar climatic, vegetation and rainfall characteristics. Possible options for the control of ticks in the study area are briefly discussed.     

The efficiency of patch sampling for determination of relative tick burdens in comparison with total tick counts

Quanttative data on host tick burdens ar fundamental for the initiation of control strategies and effective management of wildlife populations, but the methods of live sampling employed for domestic animals are unsuitable for sampling wild animals. Despite advances in the use of destructive methods (the scrub and digestion techniques) to obtain measures of the total tick burden on wildlife, these methods are too involved for many field workers, who often need only measures of relative tick burden. Recently, patch sampling methods have been introduced whereby only certain predilection sites are sampled, the presumption being that the number of ticks collected gives an indiccation of the relative degree of infestation. We examined the validity of patch sampling as a measure of relative tick burden by comparing adult ticks collected from the ears, head, neck, foreleg and perianal region of impala (aepyceros melampus) with total tick burdens of the same animals derived from the digestion technique. Adult ticks from patch sampling were positively and significantly correlated with total adults and total ticks (larvae, nymphs, and adults) on impala, with ticks patch sampled from the neck showing the highest correlation with the total tick burden. Comparison of relative tick loads from patch sampling with absolute tick loads from digestion for three classes of impala (females, bachelor males and territorial males) gave qualitatively similar results. We conclude that, when measures of relative tick load are sufficient and destructive sampling is not feasible, patch sampling can provide reliable information on relative tick burdens that are positively correlated with the total tick burden.     

Factors influencing the distribution of questing ticks and the prevalence estimation of T. parva infection in brown ear ticks in the Tanga region, Tanzania.

Questing ticks from various districts and agro-ecological zones (AEZ) in the Tanga Region of Tanzania were studied for a two-year period between September 1999 and July 2001. Collections of both nymphal and adult ticks occurred at 29 sites using a blanket or white cloth dragging technique. The species recorded in the order of decreasing abundance were Rhipicephalus appendiculatus, Boophilus spp., and Ambylomma variegatum. Rhipicephalus appendiculatus field infestation levels varied across administrative districts and seasons, with Amani and the cool-to-dry season having lower tick counts ( = -2.09, SE = 0.71, P < 0.001 and = -1.54, SE = 0.56, P = 0.006 for Amani and cool to dry season, respectively). Based on the polymerase chain reaction technique, Theileria parva infection prevalence in adult R. appendiculatus was estimated to be 2.6%. Implications of these findings in light of the spatial and temporal distribution of ticks are discussed for the accurate diagnosis of multiple tick-borne diseases, the infected vector tick, the endemic status of T. parva in the region, and the implemention of control strategies.     

The impact of Ixodiphagus hookeri, a tick parasitoid, on Ambl yomma variegatum (Acari: Ixodidae) in a field trial in Kenya

In an experiment to investigate the effect of the tick parasitoid, Ixodiphagus hookeri, on tick numbers on cattle, 150 000 parasitoids were released over a period of 1 year in a field where ten cattle infested with multiple tick species were kept. Amblyomma variegatum was reduced from 44 to two ticks per animal while Rhipicephalus appendiculatus increased over the time of parasitoid release. During the time of release 51% of the nymphs of A. variegatum collected from the animals were parasitized. The recovery of the parasitoids after the releases were stopped was only 9%. The total numbers of A. variegatum remained low up to 1 year after the parasitoid release was stopped. This study gives an insight into how I. hookeri could be used strategically for the management of A. variegatum on small-scale farms.     

Livestock Tick Predation by Chickens: The Rate of Digestion of Ticks in the Alimentary Tract of Chickens

Research on the predation of ticks by chickens is required to establish the potential rôle of chickens as biological control agents for ticks. In the present study, 26 local chickens were allowed to feed in groups of two or three for 1 hour on a meal containing adult unengorged Rhipicephalus appendiculatus and Amblyomma variegatum and slaughtered thereafter at different intervals ranging from 11 min to 24 h. The contents of the digestive tracts of the chickens were carefully examined under a dissecting microscope to determine the state of digestion of the ingested ticks.

All ticks found in the crop were not digested and a few A. variegatum were attached to the crop wall and were found dead. The gizzard contained partially and completely digested ticks while tick remnants were predominant in the small intestine. It was concluded that most of the digestion of tick proteins takes place in the small intestine. It was also concluded that, although the digestion rate of ticks varies in individual chickens, all ticks digested in a meal should have been completely digested and absorption of the tick nutrients should have started within 21–24 h although this could have been accomplished as early as 9 h by chickens with fast digestion rates.     

The impact of natural infestations of ticks in Zambia on the productivity of cattle and implications for tick control strategies in central Africa

Studies were carried out in Zambia using a farming systems approach to quantify the effects of tick control on traditionally managed Sanga cattle. In the first trial to investigate the effect of tick control, significant improvements in liveweight gain (LWG) occurred only in periods of medium to high challenge with adult Amblyomma variegatum. However, during the first 18 months of the study when animals were young, the acaricide used caused a suppression in weight gains. A supplementary experimental study indicated that the adverse effects of ticks on weight gain may be delayed when animals are on a low plane of nutrition. In both studies on the effects of ticks on LWG, estimates of weight loss per female A. variegatum were in the range of 46 to 69 g. In the second long term trial to measure the impact of tick control on overall heard productivity, outputs of milk and weaner calf per livestock unit carrying capacity were about 25% higher in a tick-free herd. The annual cost of control in 1988 at ZK286.26/livestock unit was greater than the increase in value of the products at ZK175.48/livestock unit carrying capacity. It is concluded from these studies that intensive tick control in the multipurpose livestock system in Zambia is not justified in the absence of serious tick-borne disease. However, strategic seasonal tick control of adult ticks from November to April would probably be economically viable. Calves should not be treated until they are 3 months of age.     

Strategic tick control in Burundi

Strategic tick control is an attempt to control ticks and reduce losses in animal production due to tick infestations while decreasing the cost for this control. Tick control is understood as a necessity to achieve maximum animal production from animals raised in tick-infested areas. At the same time, it has become difficult to justify intensive, year-round tick control for local breeds and their crosses. The increasing costs of acaricides, maintenance of the infrastructures, salaries for personnel, etc. have created a tick control programme where the benefits may not be adequate to justify the expense. This has been the case in Burundi. This programme with adequate participation from the cattle owners of Burundi and organizational support from government personnel can help solve this economic problem. The strategic programme reduces the period of tick control to four months each year. Once optimal participation is achieved, this period can probably be reduced to three months (Kaiser et al., 1988). The period of treatment corresponds to when there is maximal feeding activity of adult female ticks on the bovine population within a certain region. Cattle should be treated once each week throughout the four-month period in order to prevent female tick engorgement (based on the life cycle of R. appendiculatus). This will greatly reduce the number of female ticks which are available to recycle the population of ticks in the participating area. At the same time, a certain population of ticks must be maintained in order to assure contact between the cattle, ticks, and tick-borne diseases of this particular region.(ABSTRACT TRUNCATED AT 250 WORDS)     

Population dynamics of ticks on indigenous cattle in a pastoral dry to semi-arid rangeland zone of Uganda

Studies on seasonality and population dynamics of ticks on indigenous cattle and their crosses (calves) were carried out in Buruli Ranching Scheme, Nabiswera, Luwero district of Uganda on three treatment groups of animals: group 1 (twice a week dipping), group 2 (once a month dipping) and group 3 (no tick control). During this study, four major species of ticks of economic importance were recorded in decreasing order of abundance: Rhipicephalus appendiculatus, Rhipicephalus evertsi evertsi, Amblyomma variegatum and Boophilus decoloratus. Of these ticks, a seasonal pattern of activity was only observed in R. appendiculatus ticks, with peak activities occurring during rainy seasons. Greater numbers of ticks were recorded on cows than calves in the three treatment groups, with the exception of A. variegatum where the reverse occurred. The mean numbers of ticks per animal were highly significantly different (p < 0.01) when group 1 animals were compared with group 2 and 3 animals. However, no significant differences (p > 0.05) were observed in mean tick numbers between group 2 and 3 animals. Highly significant differences (p < 0.01) were observed in mean tick numbers on cows and calves (more than 12 months old) in different calving seasons. The state of lactation only affected tick counts on cows in group 1; significantly more ticks (p < 0.01) were observed in lactating than non-lactating cows. Furthermore, significantly greater (p < 0.05) numbers of ticks (with the exception of B. decoloratus) were recorded during the second year of study (March 1992-May 1993) than the first year (January 1991-February 1992), despite lower rainfall during the former period.     

Effect of tick control on liveweight gain of cattle in central Zambia

Field trials were carried out during 1982-86 in two different ecotypes in central Zambia to determine the impact of tick control on the liveweight gain (LWG) of cattle. During the first 2 years of the trial a diamidide acaricide (Amitraz) sprayed at weekly intervals caused periodic depression in LWG in young animals. Thereafter a pyrethroid acaricide (cypermethrin) was used. During the 1984-85 tick season infestations of 50-120 adult Amblyomma variegatum Fabricius in untreated animals caused significant reductions in LWG. From the differences in LWG between treated and untreated cattle, the induced loss in LWG was estimated at 46-61 g per engorged female A.variegatum.     

Two-spotted spider mite reared on resistant eggplant affects consumption rate and life table parameters of its predator,Typhlodromus bagdasarjani (Acari: Phytoseiidae)

The blue tick, Rhipicephalus microplus, threatens cattle production in most tropical and subtropical areas of the world. Delayed skin hypersensitivity reactions are thought to cause Nguni cattle to be more resistant to R. microplus than Bonsmara cattle yet the cellular mechanisms responsible for these differences have not been classified. Tick counts and inflammatory cell infiltrates in skin biopsies from feeding sites of adult R. microplus ticks were determined in 9-month-old Nguni and Bonsmara heifers to determine the cellular mechanisms responsible for tick immunity. Nguni heifers (1.7 ± 0.03) had lower (P < 0.05) tick counts than the Bonsmaras (2.0 ± 0.03). Parasitized sites in Nguni heifers had higher counts of basophils, mast and mononuclear cells than those in the Bonsmara heifers. Conversely, parasitized sites in Nguni heifers had lower neutrophil and eosinophil counts than those in the Bonsmara heifers. Tick count was negatively correlated with basophil and mast cell counts and positively correlated with eosinophil counts in both breeds. In the Bonsmara breed, tick count was positively correlated with mononuclear cell counts. Cellular responses to adult R. microplus infestations were different and correlated with differences in tick resistance in Nguni and Bonsmara cattle breeds. It is essential to further characterise the molecular composition of the inflammatory infiltrate elicited by adult R. microplus infestation to fully comprehend immunity to ticks in cattle.     

Failure of white-tailed deer, Odocoileus virginianus L., to sustain a population of cattle ticks, Boophilus annulatus (Say), through successive generations

Cattle ticks, Boophilus annulatus (Say), previously reared only on cattle, were placed on 3 white-tailed deer, Odocoileus virginianus L. Ticks were maintained through successive generations solely on the same deer as they aged (3, 6, and 9 mo of age) and received repeated challenges (0, 1, and 2 previous challenges). Cattle were infested simultaneously to assess tick viability and provide a comparison of tick numbers, female weight, egg mass weight, and egg hatch. The initial infestation (3,000 larvae/animal) produced a mean of 12.7 and 506.7 females from deer and cattle, respectively. Ticks recovered from deer weighed less, laid smaller egg masses, and had lower egg hatchability than cattle-reared ticks. A second infestation (3,000 larvae/animal) produced a 6.3-fold reduction in tick numbers on deer (means = 2.0 females/deer), whereas the number on cattle increased (means = 578.0 females/calf). Ticks reared on the deer were again smaller, laid fewer eggs, and had lower egg hatch, although differences were not significant. A third infestation of deer (1,900 larvae/deer) produced only 1 engorged female tick and no viable eggs, thus eliminating the population of deer-reared ticks within 3 generations. Results of the study suggest that a population of B. annulatus will not be sustained indefinitely through time solely on deer; thus, efforts to reduce deer populations severely as a means of eradicating ticks are unnecessary.     

The dependence of Hyalomma aegyptium on its tortoise host Testudo graeca in Algeria

Hyalomma aegyptium (Linnaeus, 1758) (Ixodida: Ixodidae) has recently been confirmed as a carrier of numerous pathogenic, including zoonotic, agents. Four environmentally distinct regions of Algeria, located between the humid coastal zone and the arid Saharan Atlas range, were selected in order to compare differences in tick abundance among localities, and the correlations between tick abundance and host population characteristics and other environmental conditions. Sampling was carried out during May and early June in 2010–2012. A total of 1832 H. aegyptium were removed from 201 tortoises. Adult ticks accounted for 52% of the collection. In the pre‐adult stages, larvae were dominant. Data on prevalence, intensity (mean ± standard deviation, range) and abundance of tick infestation were calculated for each locality. Locally, prevalences reached 100%. The sex ratio was biased in favour of males (4.2). Intensities of infestation differed significantly among the localities studied for all developmental stages of the tick. The intensity of infestation by adult ticks was positively correlated to the size of the tortoise and with tortoise population density in the habitat. However, findings for immature tick stages were independent of both variables. No significant correlations between infestation intensities and the climatic parameters tested were found. Immature ticks were observed to prefer the front parts of their tortoise hosts, whereas the majority of adults were attached to the rear parts.     

Efficiency and cost of strategic use of acaricide for tick control in N'Dama cattle in The Gambia

The efficiency of strategic and strategic/selective applications of flumethrin spray formulation for controlling ticks were assessed, respectively, in two groups of fourteen N'Dama cattle (Group S and Group S/S) by comparison of the number of feeding ticks with thirteen untreated N'Dama cattle (Group U) over a period of 11 months (June 1996 to April 1997). During the expected peak of tick abundance, acaricide was applied fortnightly on the whole body in animals in Group S and only on the most infested body areas in cattle in Group S/S. Weight changes and skin lesions, directly associated with tick attachment, were recorded in cattle in the three groups. The costs of the two tick control schemes were estimated. Maximum level of ticks, all species together, feeding on cattle was observed in the rainy season. Both in Group S/S and Group S, cattle carried a lower (P < 0.001) number of feeding ticks than animals in Group U over the whole study period. Percentage of tick control, over the entire period of tick investigation, was satisfactory in both acaricide-treated groups, reaching 61.2 and 75.2% in Groups S/S and S, respectively. However, the proportion of control varied according to tick species or genus. Significantly lower prevalence of skin lesions was observed on the ano-genital and udder region in cattle in Group S/S (P < 0.05) and Group S (P < 0.01) in comparison with cattle in Group U. Mean amount of acaricide solution used and relative estimated cost of treatment in cattle in Group S/S were, respectively, 25- and 14-fold lower than those in cattle in Group S. At the end of the study, animals in Groups S/S and S were, respectively, 7.2 and 15.9 kg heavier than animals in Group U. The difference was statistically significant (P < 0.02) only between Groups S and U. However, the efficiency, low cost and derived benefits of the strategic/selective acaricide application scheme indicated that it might be the most cost effective.     

Hard tick species (Acari: Ixodidae) and infestation in two livestock agroecosystems from Antioquia,Colombia

Tick infestation affects about 80% of livestock globally while transmitting various pathogens causing high economic losses. This study aimed to determine the degree of tick infestation in two regions, North and Middle Magdalena in Antioquia, Colombia, to identify the ixodid tick species found and the associated risk factors. A cross-sectional study was carried out in 48 farms distributed in six municipalities of Antioquia. Two paddocks and eight bovines per farm were evaluated to estimate tick infestation (adults, nymphs, and larvae). Tick species were identified through a morphological and molecular analysis based on partial sequences of data obtained from DNA molecular markers, two mitochondrial (16S rRNA and COI), and one genomic DNA gene (18S rRNA). A multivariate Poisson regression model was applied to estimate the associated risk factors with ticks in cattle. Rhipicephalus microplus, Amblyomma patinoi and Dermacentor nitens were present in the livestock agroecosystems in the Middle Magdalena region; the highest incidence of tick infestation in cows and paddocks was reported in the municipality of Puerto Triunfo. The livestock agroecosystems in Middle Magdalena were characterized by a higher presence of adult R. microplus in cattle. Larval infestation of R. microplus, followed by D. nitens, was also found in paddocks. The multivariate analysis showed that the origin of cattle was the main risk factor associated with the presence of ticks (i.e., when cattle came from outside the farm). Cattle movement between farms in Middle Magdalena can contribute to the spread of ticks in this region.

     

Effects of deer density on tick infestation of rodents and the hazard of tick-borne encephalitis. I: empirical assessment

Tick borne encephalitis (TBE) is endemic to eastern and central Europe with broad temporal and spatial variation in infection risk. Although many studies have focused on understanding the environmental and socio-economic factors affecting exposure of humans to TBE, comparatively little research has been devoted to assessing the underlying ecological mechanisms of TBE occurrence in enzootic cycles, and therefore TBE hazard. The aim of this study was to evaluate the effect of the main ungulate tick hosts on the pattern of tick infestation in rodents and TBE occurrence in rodents and questing adult ticks. In this empirical study, we considered three areas where endemic human TBE occurs and three control sites having no reported human TBE cases. In these six sites located in Italy and Slovakia, we assessed deer density using the pellet group count-plot sampling technique, collected questing ticks, live-trapped rodents (primarily Apodemus flavicollis and Myodes glareolus) and counted ticks feeding on rodents. Both rodents and questing ticks were screened for TBE infection. TBE infection in ticks and rodents was positively associated with the number of co-feeding ticks on rodents and negatively correlated with deer density. We hypothesise that the negative relationship between deer density and TBE occurrence on a local scale (defined by the minimum overlapping area of host species) could be attributed to deer (incompetent hosts) diverting questing ticks from rodents (competent hosts), know as the 'dilution effect hypothesis'. We observed that, after an initial increase, the number of ticks feeding on rodents reached a peak for an intermediate value of estimated deer density and then decreased. Therefore, while at a regional scale, tick host availability has already been shown to be directly correlated with TBE distribution, our results suggest that the interactions between deer, rodents and ticks are much more complex on a local scale, supporting the possibility of a dilution effect for TBE.     

Tick antigens recognized by serum from a guinea pig resistant to infestation with the tick Rhipicephalus appendiculatus

Immune resistance to infestation by an ixodid tick, Rhipicephalus appendiculatus, the vector of the cattle disease East Coast Fever, was induced in a guinea pig by repeated tick infestation. This resistance is expressed as the ability of the host to interfere with tick feeding. Resistance to ixodid tick feeding is an acquired response mediated by host antibody. We report the use of antibodies from a resistant host animal, in immunoblotting, to characterize the tick antigens recognized. The major tick antigens identified had molecular weights of 120,000, 94,000, 88,000, 77,000, 58,000, 46,000, 35,000, 31,000, 28,000, 25,000, 20,000 and 16,000. Most of these antigens were found in tick salivary glands. The presence and concentration of many tick salivary antigens appeared to vary with relation to the tick feeding cycle. Many of the antigens present in salivary glands were also detected in tick cement. Tick gut extract, although a poorer source of antigens, contained more of the 31,000 dalton antigen than salivary glands. Larval and nymphal tick extract lacked many of the antigens present in adult ticks. The data suggest that tick resistance is a complex phenomenon probably elicited by several different tick antigens.