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PubMed2005

Analysis of BoLA class II microsatellites in cattle infested with Boophilus microplus ticks: class II is probably associated with susceptibility.

The aim of this study was to determine the role of certain bovine lymphocyte antigens (BoLA) regions in the resistance or susceptibility to Boophilus microplus tick infestation in two different breeds of cattle. The breeds were maintained, one in natural conditions and the second one in an experimental setting at the research station in Martinez de la Torre, Veracruz, Mexico. The study took place from June to August 2001 (natural infestation) using 33 crossbreed steers (crossbreed is here defined as 3/4 European = 1/2 Simmenthal x 1/4 Holstein x 1/4 Zebu, a cross resulting from F1 x Simmenthal), ranging from 15 to 20 months old. Fifty-nine F1 cows (1/2 Holstein x 1/2 Zebu) were included in the experimental setting, infested and followed during 25 days in November 2001 and 2002. Experiment A included thirty-one 2-7-year-old F1 cows, and experiment B included twenty-eight 18-24-month-old F1 heifers. Both groups were analysed separately and were not comparable because of the different infestation methods and genetic background. All ticks > or =4mm long were counted on the total body of F1 animals and on one side of the 3/4 European steers. In this case, susceptible animals were defined when having ticks = X + 1S.D. (29 +/- 16). In the experimental setting susceptibility was defined when the number of ticks was over the 75 percentile (> or =79). DNA was extracted from peripheral blood samples of all animals. The BoLA DRB3, DRBP1, RM185 and BM1815 microsatellite loci were amplified using a PCR method. Genescan software was used for analysis in an ABI sequencer. The SPSS statistical program was used and the comparisons were assessed using the Fisher's exact test. In the naturally infested animals, DRB3-184 was found positively associated with tick infestation (P = 0.018; Pc = NS; OR = 5; EF = 28%). DRBP1-128 was also found to be increased (P = 0.03; Pc = NS; OR = 6; EF = 42%). In the experimentally infested animals, two more loci were found to be associated, BM1815-152 (P = 0.01; Pc = NS; OR = 15; EF = 74%) and DRBP1-130 (P = 0.05; Pc = NS; OR = 4; EF = 77%). None of them remained significant after correction, indicating that a larger sample size is needed to confirm the results. This is the first study showing MHC genes associated with tick infestation based on class II microsatellite polymorphisms. Further studies are needed to confirm the susceptibility traits and to determine haplotype segregation in families.

Animals↗
PubMed1998

Protozoal parasites in tick species infesting camels in Sinai Peninsula.

A faunistic survey of ticks infesting camels was carried out in 7 localities of Sinai; El-Arish, Beer El Abd, Nakhel, Ain Mousa, St. Catherine, Wadi Hadra, and Dahab. The protozoal organisms present in the gut and haemolymph of the collected tick species were investigated. Results revealed the presence of six species of tick infesting camels, Hyalomma dromedarii, H. impeltatum, H. an. excavatum, H. an. anatolicum, H. marginatum and H. schulzei. The first 3 species were most common, whereas the latter 3 species were found in certain limited localities. Babesia sp. and Theilera sp. were recorded in both tick guts and haemolymph in most species allover the studied areas. Trypanosoma sp. was recorded in the guts of ticks collected from Beer El Abd, Nakhel and Dahab. Anaplasma sp. was found in tick guts from Beer El Abd and Dahab, however the same organism was detected in the haemolymph of ticks collected in Nakhel and Dahab.

Animals↗
PubMed2006

Synergistic effect of silencing the expression of tick protective antigens 4D8 and Rs86 in Rhipicephalus sanguineus by RNA interference.

Tick proteins have been shown to be useful for the development of vaccines which reduce tick infestations. Potential tick protective antigens have been identified and characterized, in part, by use of RNA interference (RNAi). RNAi allows for analysis of gene function by characterizing the impact of loss of gene expression on tick physiology. Herein, we used RNAi in Rhipicephalus sanguineus to evaluate gene functions of two tick protective antigens, 4D8 and Rs86, the homologue of Bm86, on tick infestation, feeding and oviposition. Silencing of 4D8 alone resulted in decreased tick attachment, survival, feeding and oviposition. Although the effect of Rs86 RNAi was less pronounced, silencing of this gene also reduced tick weight and oviposition. Most notably, simultaneous silencing of 4D8 and Rs86 by RNAi resulted in a synergistic effect in which tick survival, attachment, feeding, weight and oviposition were profoundly reduced. Microscopic evaluation of tick tissues revealed that guts from dual injected ticks were distended with epithelial cells sparsely distributed along the basement membrane. These results demonstrated the synergistic effect of the silencing expression of two tick protective genes. Inclusion of multiple tick protective antigens may, therefore, enhance the efficacy of tick vaccines.

Animals↗
PubMed2001

Exposure of cattle immunized with different stocks of Theileria parva to buffalo-associated Theileria challenge on two game parks in Zimbabwe.

Eight cattle immunized with cattle-derived Theileria parva Boleni stabilate together with six susceptible controls were released in Dombawera Game Park on the Highveld of Zimbabwe. This coincided with Rhipicephalus appendiculatus nymphal activity. The cattle grazed together with African buffaloes (Syncerus caffer) and were not treated against tick infestation. The nymphal tick infestation was high, and seven of the eight immunized cattle and three of the controls had severe and fatal reactions. Subsequently, two stocks of Theileria parva to be tested for their immunizing abilities were prepared-one from adult ticks which were fed as nymphs on one of the sick control animals (Dom 268) and the other from adult ticks collected from pastures grazed by buffaloes (Bv-1). Two groups of cattle were immunized with either the Dom 268-derived strain (eight animals) or the Bv-1-derived strain (four animals). These together with three non-immunized controls, were released in Bally Vaughaun Game Park in the Highveld, where buffaloes are present, during the season of nymphal tick activity. A third group of five cattle, immunized with stabilate Bv-1, and three non-immunized controls were released at the same site during the season of adult tick activity. The nymphal and adult tick infestations of the cattle were large and more than 2000 nymphs and 1000 adult ticks were counted per animal. Cattle were treated with a pyrethroid pour-on preparation to control the tick infestation and screw-worm strike. The immunized cattle in the three groups survived the theileriosis challenge for a period of 18 months, but the non-immunized control cattle suffered a severe and fatal theileriosis 19-23 days after being placed on the pasture.

Animals↗
PubMed1993

Distribution and host-relationship of ticks (Ixodoidea) infesting domestic animals and rodents in Sinai Peninsula.

Geographical distribution of ticks infesting farm animals in Sinai Peninsula revealed the presence of 12 tick species namely Hyalomma dromedarii, H. impeltatum, H. an anatolicum, H. an. excavatum, H. marginatum rufipes, H. m. turanicum, H. schulzei, Rhipicephalus sanguineus, R. turanicus, Boophilus annulatus, Ornithodors erraticus and Argas persicus. The distribution map of those species is given. The areas of Sinai could be arranged as regards the number of tick species in the following descending order, Beer Lehfin & St. Cathrine (9 spp.), Kosaimah & Nuweibah (8 spp.), Arish & Godirate (7 spp.), Firan (6 spp.) Beer El-Abd, Zowaid, Rafah, Quntara, Wadi Hadra & El Tur (5 spp.), Abu Redis, and Hammam Pharon (4 spp.).

Animals↗
PubMed1990

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.

Africa, Central↗
PubMed1994

Lymphocyte proliferative responses and the occurrence of dermatophilosis in cattle naturally infested with Amblyomma variegatum.

The proliferative response of lymphocytes from tick-infested Zebu type, N'Dama and Friesian cattle and acaricide-treated Zebu types and Friesians in concanavalin A (Con A) stimulated cultures was monitored regularly for periods ranging from 11 to 27 months. The numbers of ticks on the animals and the presence of dermatophilosis were also noted. The Friesian cattle carried most and the N'Dama fewest Amblyomma variegatum ticks. The tick-infested Friesians all developed severe clinical dermatophilosis within 5 months of becoming tick-infested. Dermatophilosis lesions on the tick-infested Zebu type and N'Dama cattle were less common and less severe especially in the N'Damas. The proliferative response of lymphocytes from tick-infested Friesians in Con A stimulated cultures fell to almost half that of the acaricide-treated Friesians soon after the former became tick-infested. The tick-infested Zebu types also developed a depressed response compared with the tick-free Zebu group over a 27 month study period. However, the responses of the N'Damas was similar to that of the tick-free Zebu types. The addition of autologous serum to Con A stimulated cultures of lymphocytes derived from the tick-infested Zebu types and N'Damas suppressed their proliferative response compared with that of similar cultures for the tick-free Zebu types.

Actinomycetales Infections↗
PubMed1979

Epidemiology and control of anaplasmosis in Australia.

Anaplasmosis occurs in those areas of northern and eastern Australia infested by the cattle tick Boophilus microplus but it has been studied intensively only in Queensland. Anaplasmosis is predominantly a disease of autumn and winter and of cattle greater than 1 year of age. The complement fixation test has been used in serological surveys of the tick-infested areas of the state. Both clinical and subclinical infections occur only in tick-infested areas and they are both more frequent in Bos taurus than in Bos indicus cattle probably due to the greater susceptibility of the former to ticks. Prevalence of infection is significantly greater in cattle exposed to heavy tick infestations than it is in cattle exposed to light tick infestations. B. microplus is considered to be the main vector with transmission being effected by transtadial and intrastadial but not transovarial means. Transtadial transmission by Rhipicephalus sanguineus has been demonstrated but attempts to demonstrate transmission by Haemaphysalis longicornis were unsuccessful. Vaccination with Anaplasma centrale is employed either as a routine preventative measure in young cattle or in the face of an outbreak. Attempts to attenuate a strain of A. marginale by adapting it to sheep were unsuccessful. Oxytetracycline and imidocarb have been used successfully to control the clinical disease.

Anaplasmosis↗
PubMed1989

Resistance and cross-resistance in guinea-pigs and rabbits to immature stages of ixodid ticks.

Infestation of guinea-pigs and rabbits with larvae of any one of five species of ticks, Rhipicephalus appendiculatus Neumann, Rhipicephalus evertsi evertsi Neumann, Amblyomma hebrauem Koch, Amblyomma variegatum Fabricius and Ixodes ricinus L., conferred resistance in the animals when exposed to subsequent infestations with the same tick species. Resistance to infestations by other tick species was not observed.

Animals↗
PubMed1995

The relationship between tick (Amblyomma hebraeum) infestation and immunity to heartwater (Cowdria ruminantium infection) in calves in Zimbabwe.

The occurrence of endemic stability for heartwater (Cowdria ruminantium infection) is a controversial issue, because the means by which young cattle and other neonatal ruminants become infected and acquire immunity to the disease have never been adequately explained. We conducted a study in a heartwater-endemic area in southeastern Zimbabwe to investigate the relationships between calf immunity to C. ruminatium, infestations of the tick vector Amblyomma hebraeum and dam, colostral and calf antibody titres to C. ruminantium. Two groups of cows (tick-infested and acaricide-treated) were artificially inseminated and then monitored through pregnancy and lactation by means of tick counts and serum antibody titres. The calves born to the cows in each treatment group were similarly monitored from birth until after weaning, when they were challenged with a heartwater stabilate (Ball-3 vaccine). Colostrum was collected from the cows on the days that the calves were born. Serum and colostrum samples were screened for Cowdria-specific antibodies using an indirect fluorescent antibody test. The cows and calves in the acaricide-treated group remained essentially tick-free for the duration of the study. The cows in the tick-infested group were continuously infested with A. hebraeum, but their calves only became infested between 12 and 31 weeks after birth. Cowdria-specific antibodies were detected in the sera of the cows and calves and in the colostrum of both treatment groups, but the titres were consistently higher in the tick-infested group than in the acaricide-treated group. Antibodies, probably of maternal origin since the precolostral serum titres were negative, were present in the calves of both groups for at least 8 weeks after birth. Between Weeks 24 and 52 postpartum, the antibody titres of the tick-infested group of calves were significantly correlated with the numbers of A. hebraeum present on the animals. The antibody titres of the calves in the acaricide-treated group increased considerably following challenge with heartwater stabilate, 60 weeks after birth. No clinical heartwater was detected in either group of calves following inoculation of stabilate, and it was concluded that the calves in both groups were immune to the disease. In the acaricide-treated group, immunity did not correlate with exposure to tick-transmitted infections. Hence, we concluded that the calves in both groups had probably been infected by vertical transmission around the time of birth. Such early infections are likely to have been controlled by maternal antibodies or by an unidentified immune mechanism.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Tick-induced modulation of the host immune response.

The tick-host-pathogen interface is characterised by complex immunological interactions. Host immune responses to tick infestation and infection with tick-borne pathogens involve cytokines, antibodies, complement and T lymphocyte regulatory and effector pathways. A successful host-parasite relationship is a balance between limiting the parasite by host defenses and the ability of the parasite to modulate, evade or restrict the host response. Hosts acquire immunological based resistance to tick infestation, which reduces engorgement, production of ova and viability. Salivary glands of ixodid ticks produce a complex array of immunogens and pharmacologically active molecules. Tick salivary gland derived material can modulate host cytokine, antibody and cell mediated immune responses. Both immunoregulatory and immune effector pathways of the host are suppressed. Tick feeding impairs the ability to develop a primary immune response to a thymic dependent immunogen. Lymphocytes obtained from tick infested hosts are reduced in their ability to proliferate in vitro to T lymphocyte mitogens, while responses to B lymphocyte polyclonal activators are unaltered. Normal macrophages and lymphocytes were exposed to female tick salivary gland extracts prepared daily during the course of engorgement. All extracts reduced lymphocyte responses to T cell mitogens and enhanced in vitro proliferation in the presence of a B lymphocyte mitogen. Macrophage elaboration of tumour necrosis factor alpha and interleukin-1 are significantly reduced in a differential manner. Production of interleukin-2 and interferon-gamma by T lymphocytes is reduced. Tick modulation of the host immune response could enhance the ability of the arthropod to obtain a blood meal and facilitate pathogen transmission to an immunocompetent host.

Animals↗
PubMed1997

[Lyme borreliosis in dogs].

In a 2-year-old Bernese Mountain dog the diagnosis of Lyme borreliosis was made, using the criteria that are mentioned in the literature: seropositivity in the presence of the typical clinical symptoms, with infestation of ticks in the history. The usual therapy of amoxycillin or tetracyclines was inadequate and did not resolve the clinical symptoms, possibly as a result of a combination of initial corticosteroid therapy, the clinical presentation of the disease (mainly meningitis), and a presumed immuno-incompetence often seen in this breed. Intravenous treatment with amoxycillin finally led to total cure of the disease. Lyme borreliosis recurred half a year later, presumably as a result of a new tick infestation. A review of the literature on Lyme borreliosis in humans and dogs is presented. The fact that Lyme borreliosis in dogs in the Netherlands has not been diagnosed often and has not been reported before may be due to differences in approach to human and canine patients with fever.

Ampicillin↗
PubMed1999

Bm86 antigen induces a protective immune response against Boophilus microplus following DNA and protein vaccination in sheep.

Vaccination of sheep with a plasmid bearing the full length gene for the tick antigen Bm86 either alone or co-administered with plasmid carrying the ovine genes for the cytokines, granulocyte and macrophage colony stimulating factor (GM-CSF) or interleukin (IL)-1beta induced a relatively low level of protection against subsequent tick infestation. This tick damage reached statistical significance only for the groups which were vaccinated with plasmid encoding for Bm86, co-administered with plasmid encoding for ovine GM-CSF. Antibody titres measured against Bm86 were also low in all groups injected with the Bm86 DNA vaccine. Antibody production and anti-tick effect were significantly less than that achieved by two vaccinations with recombinant Bm86 protein. In all cases only a low level of antigen-specific stimulation of peripheral blood lymphocytes was recorded, as measured either by the incorporation of tritiated thymidine or the release of IFN-gamma. Injection of DNA encoding for Bm86, either alone or with co-administered cytokine genes, did however prime for a strong subsequent antibody response following a single injection of recombinant Bm86 protein in adjuvant. Antibody production nevertheless appeared to be slightly less effective than following two vaccinations with recombinant protein. The persistence of antibody following vaccination was the same regardless of the method of primary sensitization. In all cases the half-life of the antibody response was approximately 40-50 days indicating that, in contrast to results reported in mice, DNA vaccination in sheep did not result in sustained antibody production.

Animals↗
PubMed2000

Role of grooming in biological control of ticks.

Although many species of wild bovids live in tick infested environments, tick loads are usually kept to very low levels, primarily by frequent self grooming. Evidence from numerous studies on antelope in Africa strongly support the concept that the delivery of bouts of grooming reflects programmed grooming rather than stimulus driven or reactive grooming. In other words, grooming occurs in response to an endogenous generator that produces grooming bouts at periodic intervals, resulting in removal of ticks before they attach and begin to feed. In the same tick exposure environment, animals that groom most have the fewest ticks. The rate of programmed grooming is modulated by a number of interspecific and intraspecific determinants. Interspecific determinants include adult body size and whether or not the evolutionary habitat is tick dense or tick sparse. Intraspecific determinants include developmental stage of growth, gender (e.g., territorial male vs. female), ectoparasite exposure, and stage of arousal. Some of the intraspecific determinants appear to be mediated by systemic physiological influences suggesting there may be ways to improve grooming activity in weak groomers, such as cattle.

Africa↗
PubMed1998

Field studies and cost-effectiveness analysis of vaccination with Gavac against the cattle tick Boophilus microplus.

The control of tick infestations and the transmission of tick-borne diseases remains a challenge for the cattle industry in tropical and subtropical areas of the world. Traditional control methods have been only partially successful and the parasites continue to result in significant losses for the cattle industry. Recently, vaccines containing the recombinant Boophilus microplus gut antigen Bm86 have been developed. These vaccines have been shown to control tick infestations in the field. However, extensive field studies investigating the efficacy and cost-effectiveness of vaccination have not been reported and are needed to appraise the effect of this new approach for tick control. Here is reported the results of the application of Gavac in a field trial including more than 260,000 animals in Cuba. In this study the correlation between the antibody response to vaccination and the effect on ticks fertility is determined. Physiological status of the animals was found to affect the primary response to vaccination but not the antibody titers after revaccination. A cost-effectiveness analysis showed a 60% reduction in the number acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of $23.4 animal-1 year-1. These results clearly demonstrate the advantage of vaccination and support the application of Gavac for tick control.

Animals↗
PubMed1993

Contrasting effects of sera from rabbits and cattle infested with ticks on the in vitro feeding performance of the tick Rhipicephalus appendiculatus.

The in vitro feeding activity of partially engorged Rhipicephalus appendiculatus (Neumann) (Acari: Ixodidae) females fed on sera from uninfested hosts was compared to that of ticks fed serum of hosts which had previously been infested with ticks. Although ticks fed best on sera from bovid hosts which had no prior exposure to this ectoparasite, two infestations of a bovid had no significant effect on the acceptability of its serum. In contrast, ticks fed sera from rabbits which had twice been infested with ticks gained significantly less weight than those fed serum obtained from the same animals before the infestations. Clearly there is a difference between natural host resistance and that of laboratory animals.

Animals↗
PubMed1993

Experiments on the relationship between feeding of the tick Amblyomma variegatum (Acari: Ixodidae) and dermatophilosis skin disease in sheep.

Experiments on the systemic effect of feeding adult Amblyomma variegatum (F.) on dermatophilosis caused by Dermatophilus congolenis in six sheep were performed by feeding ticks at sites separate from sites of experimental infection with D. congolensis. Comparisons were made with D. congolensis infections on six control sheep without ticks. Tick-infested sheep developed chronic dermatophilosis lesions; tick-free sheep healed rapidly. On two tick-infested and two control sheep a chronological sequence of D. congolensis infection sites were made for histological comparisons. Dermatophilosis lesions on tick-infested sheep were characterized by chronic cellular infiltration and accumulation of plasma cells. Lesions on control sheep healed in association with transient cellular infiltration including plasma cells. In neither test nor control sheep was there evidence of effective phagocytosis of D. congolensis. It was concluded that feeding of these ticks had a systemic effect on the host such that dermatophilosis was aggravated via an effect on immunological reactions in the skin. Control of dermatophilosis by tick control is advocated.

Actinomycetales Infections↗