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PubMed1990

Estimation of the potential demand for a bovine babesiosis and anaplasmosis vaccine in Argentina.

A survey to estimate the potential demand for a bovine babesiosis and anaplasmosis vaccine was carried out by a postal questionnaire sent to 4407 veterinarians in the north and centre of Argentina. Twenty-three percent of the questionnaires (1047) were answered; 317 (7.2% of the total, 30% of those answered) pointed out the occurrence of the diseases and/or probable demand for the vaccine. The minimum and maximum demands were 407,892 and 982,300 doses for anaplasmosis, and 272,496 and 631,400 doses for babesiosis, respectively. The results presented from here onwards are based on the minimum demand. Sixty-eight and 48% of the anaplasmosis and babesiosis vaccine demand, respectively, came from veterinarians living in the Boophilus microplus-free area, while the remainder came from the tick-infested area, reflecting the fact that many farm owners from the tick-infested area seek professional assistance from veterinarians living in the tick-free area. Most of the demand for both vaccines was aimed at breeding cattle (77.2%), 14.5% at dairy cattle and the rest at studs (8.3%). Veterinarians living in the tick-infested area demanded vaccine for breeding cattle in a higher proportion than veterinarians from the tick-free area, whose demand was greater for dairy cattle. In the tick-free area, the demand for anaplasmosis vaccine was twice that for babesiosis vaccine, whereas in the tick-infested area the demand was equal. This agrees with the fact that the anaplasmosis-stricken area extends beyond the tick-infested region. Sixty percent of the respondents preferred a vaccine frozen in liquid nitrogen, whilst the rest preferred a refrigerated one, the first group accounted for 73% of the total demand. Fifty-six percent of the demand occurred between March and June with the peak in April, which reflects the main weaning date. The elasticity of the demand is discussed in relation to the probable benefits to be accrued by the farmers who make use of it. The annual mortality rates due to both babesiosis and anaplasmosis were estimated at 1.5 and 3.5% in the milk herds of Salta and Tucumán, respectively. In the beef herds of these two provinces, the mortality rate due to both diseases has been estimated at 3.5%. Using these figures and current prices, the systematic application of the vaccine in calves would render a benefit-cost ratio between 4.6 and 9.0, which would warrant its use in the herds of the areas at risk, i.e. in enzootic instability.

Anaplasma↗

PubMed2000

Immunological control of ticks through vaccination with Boophilus microplus gut antigens.

The control of tick infestations and the transmission of tick-borne diseases remain a challenge for the scientific community. Traditional control methods have been only partially successful. Recently, vaccination with recombinant Boophilus microplus gut antigens has been shown to control tick infestations. Our Bm86-containing vaccine formulation (Gavac) has been effective for the control of artificial infestations of B. annulatus, B. decoloratus, and chemically sensitive and resistant B. microplus strains from Australia, Africa, America, and Iran. Preliminary results with Hyalomma spp. and Rhipicephalus spp. suggest partial cross protection. In field trials, vaccination with Gavac controlled B. microplus and B. annulatus infestations and reduced the transmission of babesiosis, resulting in important savings for the cattle industry. Different degrees of susceptibility to the vaccination with Bm86 and sequence variations in the Bm86 locus have been reported. The Bm95 antigen was isolated from the Argentinean Bm86-resistant B. microplus strain A. A Bm95-based vaccine was used to protect cattle against tick infestations under production conditions with similar results to that obtained with Gavac. The Bm95 antigen from strain A was able to protect against infestations with Bm86-sensitive and Bm86-resistant tick strains, thus suggesting that Bm95 could be a more universal antigen in protecting cattle against infestations by B. microplus strains from different geographical areas. These results clearly demonstrate the advantage and possibilities for the immunological control of ticks.

Animals↗

PubMed1997

Perceptions of veterinary clinics and pest control companies regarding tick-related problems in dogs residing in Texas cities.

OBJECTIVE: To determine the extent and source of tick-related problems encountered by veterinary clinics and pest control company (PCC) clientele experiencing residential tick infestations in urban/suburban environments and to determine which tick-related diseases in dogs were diagnosed and treated at veterinary clinics. DESIGN: Cross-sectional survey. SAMPLE POPULATION: Veterinary clinics and PCC in Dallas/Fort Worth and Austin/San Antonio, Tex. PROCEDURE: Surveys were made into professionally printed booklets and mailed to participants. RESULTS: Dallas/Fort Worth and Austin/San Antonio clinics indicated that tick-related problems comprised 21 and 15%, respectively, of their canine-based business. The most frequently observed species was the brown dog tick. Tick infestations were most common during May through August. Immature tick populations were seen by the greatest number of clinics in May and June, and engorged female ticks were encountered most often in June and July. Ticks were most commonly found around homes and adjacent yards or lots. Greenbelts were perceived by all 4 study groups to be the principal place in the community where ticks were acquired by clients' dogs. Canine ehrlichiosis was the most common tick-related disease diagnosed and treated at clinics, followed by anemia caused by tick infestation. CLINICAL IMPLICATIONS: Identification of ticks is important, because different tick species transmit different disease agents and different ecologic factors may be associated with exposure and subsequent treatment. Knowledge of temporal activity patterns of ticks, where they are acquired and where populations become established, combined with improved cooperative efforts between veterinary clinics and PCC, would aid in more effective control and management of ticks.

Animals↗

PubMed2003

Antigens from Rhipicephalus sanguineus ticks elicit potent cell-mediated immune responses in resistant but not in susceptible animals.

In the present study we compared the immunological reactions between Rhipicephalus sanguineus tick-infested susceptible (dogs and mice) and tick-resistant hosts (guinea pigs), elucidating some of the components of efficient protective responses against ticks. We found that T-cells from guinea pigs infested with adult ticks proliferate vigorously in the presence of concanavalin A (ConA), whereas ConA-induced cell proliferation of tick-infested mice and dogs was significantly decreased at 43.1 and 94.0%, respectively, compared to non-infested controls. Moreover, cells from mice and dogs submitted to one or three successive infestations did not exhibit a T-cell proliferative response to tick antigens, whilst cells from thrice tick-infested guinea pigs, when cultured with either a tick extract or tick saliva, displayed a significant increase in cell proliferation. Also, we evaluated the response of tick-infested mice to a cutaneous hypersensitivity test induced by a tick extract. Tick-infested mice developed a significant immediate reaction, whereby a 29.9% increase in the footpad thickness was observed. No delayed-type hypersensitivity (DTH) reaction was detected. Finally, the differential cell count at the tick attachment site in repeatedly infested mice exhibited a 6.6- and 4.1-fold increase in the percentage of eosinophils and neutrophils, respectively, compared to non-infested animals, while a decrease of 77.0-40.9 in the percentage of mononuclear cells was observed. The results of the cutaneous hypersensitivity test and the cellular counts at the tick feeding site for mice support the view that tick-infested mice develop an immune response to R. sanguineus ticks very similar to dogs, the natural host of this species of tick, but very different from guinea pigs (resistant host), which develop a DTH reaction in addition to a basophil and mononuclear cell infiltration at the tick-attachment site. In conclusion, saliva introduced during tick infestations reduces the ability of a susceptible animal host to respond to tick antigens that could stimulate a protective immune response. As a consequence, the animals present a lack of DTH response and disturbed cellular migration to tick feeding site, which can represent a deficient response against ticks.

Animals↗

PubMed1990

Infestation of cattle by the brown ear tick, Rhipicephalus appendiculatus, does not affect serological responses to foot-and-mouth disease vaccine.

A comparison of the serological responses of tick-free and tick-infested cattle following inoculation with the Botswana SAT 2 foot-and-mouth disease vaccine indicated that infestation by the brown ear tick, Rhipicephalus appendiculatus, did not affect serological responses to the vaccine. This finding implies that infestation by this tick species is unlikely to influence immunity following routine inoculation against foot-and-mouth disease in tick endemic areas.

Animals↗

PubMed2000

Issues in tick vaccine development: identification and characterization of potential candidate vaccine antigens.

It is well established that acquired immunity against tick infestation can be induced by repeated tick infestation or by active immunization with either crude or purified native as well as recombinant antigens. This review provides insights into the development of tick vaccines with reference to identification, purification and molecular cloning of candidate target antigens.

Animals↗

PubMed2006

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

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

Animal Migration↗

PubMed1999

Sequence variations in the Boophilus microplus Bm86 locus and implications for immunoprotection in cattle vaccinated with this antigen.

Cattle tick infestations constitute a major problem for the cattle industry in tropical and subtropical regions of the world. Traditional control methods have been only partially successful, hampered by the selection of chemical-resistant tick populations. The Boophilus microplus Bm86 protein was isolated from tick gut epithelial cells and shown to induce a protective response against tick infestations in vaccinated cattle. Vaccine preparations including the recombinant Bm86 are used to control cattle tick infestations in the field as an alternative measure to reduce the losses produced by this ectoparasite. The principle for the immunological control of tick infestations relies on a polyclonal antibody response against the target antigen and, therefore, should be difficult to select for tick-resistant populations. However, sequence variations in the Bm86 locus, among other factors, could affect the effectiveness of Bm86-containing vaccines. In the present study we have addressed this issue, employing data obtained with B. microplus strains from Australia, Mexico, Cuba, Argentina and Venezuela. The results showed a tendency in the inverse correlation between the efficacy of the vaccination with Bm86 and the sequence variations in the Bm86 locus (R2 = 0.7). The mutation fixation index in the Bm86 locus was calculated and shown to be between 0.02 and 0.1 amino acids per year. Possible implications of these findings for the immunoprotection of cattle against tick infestations employing the Bm86 antigen are discussed.

Amino Acid Sequence↗

PubMed2000

Coinfection with Borrelia burgdorferi and the agent of human granulocytic ehrlichiosis suppresses IL-2 and IFN gamma production and promotes an IL-4 response in C3H/HeJ mice.

Previously we demonstrated that Borrelia burgdorferi transmission by Ixodes scapularis suppressed IL-2 and IFN gamma production and promoted IL-4 production in mice. The present studies were conducted to determine whether coinfection with the human granulocytic ehrlichiosis (HE) agent would promote a Th2 cytokine response in mice. Transmission to the spleen of the agent of human granulocytic ehrlichiosis (aoHGE) and B. burgdorferi occurred 4 and 7 days, respectively, after tick infestation. Coinfection synergized to suppress splenic IL-2 production 7-14 days after tick infestion. Transmission of B. burgdorferi or aoHGE alone significantly decreased splenic IFN gamma 4-7 days after tick infestation, while coinfection suppressed IFN gamma production 7-14 days after tick infestation. Splenic IL-4 production was significantly increased 4 days after coinfection, and by day 10, aoHGE plus B. burgdorferi induced greater splenic IL-4 (57.2 pg/ml, 348% of control values) than either organism transmitted alone (aoHGE, 22.7 pg/ml, B. burgdorferi, 25.1 pg/ml). Coinfection enhanced expansion of splenic T cells, CD4+ lymphocytes and B cells while decreasing CD8+ T cells. These data demonstrate that aoHGE and B. burgdorferi, when cotransmitted, suppress a systemic IL-2 and IFN gamma response, while strongly promoting systemic IL-4 production in the susceptible host. The antigen(s) responsible for this polarization are unknown and will be the subject of future studies.

Animals↗

PubMed1992

The use of time-series analysis to forecast bont tick (Amblyomma hebraeum) infestations in Zimbabwe.

Studying the dynamics of tick infestations on cattle is an essential step in developing optimal strategies for tick control. Successful strategic tick control requires accurate predictions of when tick infestations will reach predetermined threshold levels. In the case of Amblyomma hebraeum, earlier work has shown that there is no consistent pattern of seasonal activity. This means that a statistical model for predicting A. hebraeum infestations cannot reliably use climatic factors as the only independent variables. An alternative method is to apply time-series, or auto-regressive moving-average (ARMA), analysis which uses only the past population patterns to predict future trends. This technique was applied to a data set consisting of 108 weekly tick counts of A. hebraeum (adult males, standard females, flat females and standard nymphs), conducted at an experimental station in southeastern Zimbabwe. The ability of the ARMA models to fit and predict actual tick infestations was judged using two sets of criteria. The first set focused on the goodness-of-fit, and used the adjusted R2 values, Q statistic and the Akaike Information Criteria. The second set of criteria measured the forecasting accuracy of an estimated equation, and consisted of regressing a 9-period forecast against an actual out-of-sample data set not used in the estimation process. The root mean square error of the forecast was also considered when comparing several models for the same data set. Using these criteria, the models estimated using the ARMA technique were judged to both fit and forecast with sufficient accuracy to warrant their use in strategic tick control. Although the success of using ARMA to forecast A. hebraeum is partly due to the non-seasonal behavior of the species, the results presented here suggest that it is worthwhile exploring the use of ARMA techniques to model the dynamics of other tick species. Where independent variables exert considerable influence on the dynamics of a tick species, these variables can be incorporated into an ARMA-style model.

Animals↗

PubMed2006

Ixodes frontalis and avian tick-related syndrome in the United Kingdom.

OBJECTIVES: This study aimed to characterise tick species responsible for avian tick infestations in the UK, to analyse various risk factors for tick-related syndrome in tick-infested birds and to test samples for the presence of certain tick-transmitted pathogens. METHODS: Ticks, blood, splenic tissue and tick attachment site tissue from birds with attached ticks were requested from veterinarians and wildlife sanctuaries around the UK. Ticks were identified according to standard keys, and samples were analysed via DNA PCR test for Borrelia burgdorferi sensu lato, Babesia species, Bartonella species and Ehrlichia species. RESULTS: Ixodes frontalis was the most commonly identified tick, and an association of adult female I frontalis with tick-related syndrome in birds was demonstrated. Tick infestation was markedly seasonal. I frontalis was found on 32 species of birds. DNA PCR testing was uniformly negative. Of the birds known to have been treated, 75 per cent (nine of 12) survived. CLINICAL SIGNIFICANCE: Tick-related syndrome is a poorly understood syndrome, with sporadic distribution, both geographically and seasonally. This study confirms I frontalis as the most common cause of this syndrome in the UK and identifies some features of the tick life cycle in this country. The benefit of treatment in affected birds is highlighted. Risk factors for tick-related syndrome are examined and preventive strategies discussed.

Animals↗

PubMed2000

Immunogenetic influences on tick resistance in African cattle with particular reference to trypanotolerant N'Dama (Bos taurus) and trypanosusceptible Gobra zebu (Bos indicus) cattle.

In sub-Saharan Africa, tick infestation and tick-borne infections together with tsetse-transmitted trypanosomosis arguably constitute the main parasitological disease complex constraining livestock production. Resistance to tick attack and tick-borne micro-organisms (TBMs) varies among different breeds of cattle. The magnitude of losses due to these parasites is related to an extent to the degree of breed resistance. Generally, zebu (Bos indicus) cattle possess a higher resistance to ticks and TBMs than European (Bos taurus) cattle. The host's immune system would appear to be the single most important factor that regulates this resistance. This paper reports on the main effector immune mechanisms governing resistance against ticks and TBMs. The cellular immune response appears more effective and stable than humoral immunity in modulating resistance to ticks and TBMs. Similarities between the immune mechanisms employed by trypanotolerant N'Dama (B. taurus) cattle, when infected with trypanosomes, and those elicited by tick bites and TBMs seem to exist, particularly at the skin level in the early phases of parasitic invasion. Moreover, there is evidence that in the N'Dama breed, resistance against ticks per se also has a genetic basis. Therefore, the N'Dama appears to be a unique breed in that it exhibits resistance to several parasitic diseases and/or infections, including helminths, when compared to other cattle breeds in West Africa. It is concluded that the multi-parasite resistant traits of the N'Dama breed should be exploited in those areas where trypanosomosis, ticks and tick-borne diseases constrain animal production. This should be of benefit for low-input farming systems where the use of chemicals for prophylaxis and therapy is limited by their relatively high cost. Additionally, the potential contribution of multiple disease resistant N'Dama cattle should be considered in crossbreeding programmes with exotic dairy breeds for increasing milk production in West Africa.

Africa South of the Sahara↗

PubMed1993

Effects of cattle tick (Boophilus microplus) infestation on the bovine immune system.

The immunosuppressive effect of experimental Boophilus microplus infestation on bovine peripheral blood lymphocytes (PBL) and on host antibody production to a protein antigen (ovalbumin) was examined. Boophilus microplus infestation caused a marginal decrease in the percentage of T lymphocytes in PBL, which was observed in both lightly (5000 larvae) and heavily (40,000 larvae) infested cattle, and began at the second infestation and continued until the end of the fourth infestation. The percentage of B lymphocytes in heavily tick-infested cattle was less than that in non-infested control cattle after the fourth infestation. The response of PBL from tick-infested cattle to phytohemagglutinin (PHA) was always less than that of tick-free cattle after the second infestation. No noteworthy differences were detected between the three stages of tick infestation, that is, 1 week before the peak of adult engorgement, the middle of the peak and 1 week after all ticks had dropped. Boophilus microplus saliva (100 microliters ml-1) suppressed 47% of the response of bovine PBL to PHA in vitro. This suppressive effect of saliva may contribute to the lower responsiveness of PBL from tick-infested cattle. Antibody production by tick-infested cattle was examined during the third and fourth heavy tick infestation. Tick-infested cattle showed a diminished response against ovalbumin after the second immunization. The immunosuppressive effects of tick infestation may play an important role in tick survival or in the transmission of tick-borne diseases in the field.

Animals↗

PubMed1999

Tick species infesting ruminants in Italy: ecological and bio-climatic factors affecting the different regional distribution.

The distribution of tick species able to infest ruminants in Italy is briefly reviewed on the basis of published records and new data obtained in several surveys carried out mainly in northern Italy. The most frequent and abundant tick species found on ruminants throughout Italy are Ixodes ricinus and Dermacentor marginatus, the first gradually replacing its association with sheep by the association with wild ruminants. Rhipicephalus bursa was mainly found on cattle while R. turanicus, which is considered one of the most sheep-associated species, was found only on wild boar. Haemaphysalis punctata, H. sulcata and H. parva are the other tick species quite frequently found on small ruminants when they are reared on pastures mainly in central-southern Italy. However, the land exploitation of these last decades has dramatically reduced the diversity of Italian environment and significantly modified the distribution and the abundance of ticks causing a heavy spread of the tick species characterized by a strong adaptability such as I. ricinus and R. sanguineus. If this trend continues, it is possible to hypothesise that few "resistant" tick species will gradually replace most of the others. This hypothesis seems to be confirmed by the high percentage observed for I. ricinus (57.4%) and R. sanguineus (35.73%) out of 8,712 specimens collected from several different hosts and from the environment.

Animals↗

PubMed2002

Natural Ehrlichia phagocytophila transmission coefficients from sheep 'carriers' to Ixodes ricinus ticks vary with the numbers of feeding ticks.

In a longitudinal study in a UK upland site, 38% of adult sheep were detected as infected with the tick-borne bacterium Ehrlichia phagocytophila by PCR of blood samples. Infection prevalence declined significantly with sheep age but varied significantly and non-linearly with the number of adult Ixodes ricinus ticks feeding per sheep. These findings suggested that under conditions of natural repeated tick-borne challenge sheep remain partially susceptible to re-infections, but the likelihood of re-infection depended on the numbers of feeding ticks. Transmission efficiency from sheep to immature ticks also varied significantly and non-linearly with the number of adult ticks feeding per sheep: transmission efficiency was almost zero in sheep with low adult tick infestations rising to 30% at certain levels of adult tick infestation. Infection intensity in infected engorged immature ticks also varied with the number of adult ticks feeding per sheep, but neither prevalence nor intensity of infection in engorged ticks were related to sheep blood PCR result. These findings suggest that variation in the numbers of ticks feeding per sheep may influence E. phagocytophila transmission by direct effects on transmission at the tick-host interface.

Animals↗

PubMed1995

Ecology of Ixodes ricinus immatures on Apodemus agrarius (Muridae) in the lowland ecosystems conditions.

Ecology of Ixodes ricinus collected on black-striped field mouse (Apodemus agrarius) was studied in the lowland ecosystems. During the study period (1986-1991), 1483 specimens of A. agrarius were examined in southern Slovakia and 1319 larvae and nymphs were collected from hosts. The seasonal pattern--bimodal (peak in spring and autumn)--was distinct for larvae. Both prevalence and abundance of tick infestation of A. agrarius by nymphs were low. Prevailing material of nymphs was collected from May (pooled data from all years) on mature hosts. There were significantly higher infestation in mature males than in females as well as significantly higher tick infestation of mature hosts than immature ones. Higher abundance of tick infestation of A. agrarius in fields is probably influenced by great spatial mobility of hosts and by import of ticks from landscape verdure.

Animals↗

PubMed1995

East Coast fever as a continued constraint to livestock improvement in Tanzania: a case study.

An investigation was carried out into the cause of deaths in a recently established dairy farm with 211 animals. Clinical examination revealed that 14 out of 15 sick animals were depressed, pyrexic, anorexic and had variable degrees of respiratory distress and enlarged lymph nodes. These clinical signs were suggestive of East Coast fever (ECF). This was confirmed on positive demonstration of piroplasms and macroschizonts in blood and lymph node smears respectively, and on post-mortem examination. Parasites were also demonstrated in smears taken from 5 other animals which were pyrexic and had enlarged lymph nodes. Epidemiological investigation revealed that the occurrence of the disease was associated with contact with tick-infested pastures and unsatisfactory tick control due to improper dipping of the herd. The use of pasture by pastoral cattle which are rarely dipped also increased tick infestation. It is concluded that, unless effective disease control is applied ECF will continue to be a major killer disease of cattle in Tanzania.

Animals↗

PubMed1963

Ticks (Ixodidae) on birds migrating from Europe and Asia to Africa 1959-61.

The need for imaginative thinking and research in the epidemiology of diseases transmitted by arthropods is made manifest by new views of the longevity and host ranges of arthropod-borne viruses, as well as by other biological and medical phenomena. Among these is the intercontinental transport of ticks by migrating birds. During the fall migration periods of 1959, 1960 and 1961, 32 086 birds (comprising 72 forms) were examined for ticks in Egypt while en route from Asia and eastern Europe to tropical Africa. Of these, 40 forms, represented by 31 434 birds, were tick-infested. The bird hosts, numbering 1040 (3.31% of the tick-infested bird forms examined), bore 1761 ticks, or 1.69 ticks per host. Common ticks taken were Hyalomma m. marginatum, Haemaphysalis punctata, and Ixodes ricinus. Ixodes frontalis and Hyalomma aegyptium were less common and Haemaphysalis sulcata, H. otophila, and H. pavlovskyi were rare. The common tick species are known to be reservoirs and vectors of pathogens causing a number of human and animal diseases in Europe and Asia. Several of the bird hosts have also been incriminated as reservoirs in their summer ranges. Over 20 strains of pathogenic viruses were isolated from these birds and their ticks in Egypt in the 1961 fall migration period.THE MOST DIFFICULT PROBLEMS IN INVESTIGATIONS SUCH AS THIS IN MANY PARTS OF THE WORLD ARE TAXONOMIC ONES: the correct identification of bird hosts, of immature stages of ticks and of viruses.

Africa↗