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PubMed1992

Immunisation of cattle against theileriosis in Nakuru District of Kenya by infection and treatment and the introduction of unconventional tick control.

One hundred and one cross European-Boran cattle (50 cows and 51 calves), on a farm in Nakuru District, Kenya, were immunised against theileriosis using Theileria parva lawrencei and Theileria parva parva stocks from another district of Kenya. The stabilates used were T.p.lawrencei (Mara III) used at 10(-1.7) dilution and T.p.parva (Kilae) used at 10(-1.0) dilution. The stabilates were combined and inoculated simultaneously with a short-acting formulation of oxytetracycline hydrochloride given intramuscularly at 10 mg kg-1 body weight and was repeated on Day 4 after inoculation of the stabilate. Most of the theileriosis challenge on the farm was thought to be derived directly from the African buffalo (Syncerus caffer). Nine percent of the cattle had significant indirect fluorescent antibody (IFA) titres before the immunisation and 99% after immunisation. The immunised cattle were exposed to tick-borne disease challenge on the farm by withdrawal of acaricide cover. The immunised cattle were divided into five groups plus two susceptible control cows and two calves for each group. Cattle in four of the groups had acaricidal ear tags, each group having a different type, applied to both ears and the fifth group remained untagged. The animals remained without conventional acaricide application for 134 days. Ten out of 20 (50%) non-immunised control cattle became T.p.lawrencei reactors which only one out of 97 (1%) of the immunised cattle reacted. A frequent complication noted was mild infections due to unidentified Theileria sp. which required expert differentiation from T.parva infections. An additional group of ten steers whose tick load was removed by hand at weekly intervals was introduced 79 days after exposure; these had no tick control and four became T.p.lawrencei reactors. Of 12 calves born during the exposure period and without tick control, four became theilerial reactors and one died. The application of acaricidal tags however, reduced tick infestation levels considerably compared with untagged controls but did not prevent transmission of theileriosis with the possible exception of tags on Group 4. A number of transient low grade fevers were noted and attributed to Theileria sp., Ehrlichia bovis, Ehrlichia (Cytoecetes) ondiri and Borrelia theileri infections, none of which were fatal. One immunised animal died of acute dual infection of Babesia bigemina and Borrelia theileri after acaricide control by spraying was re-introduced but no Anaplasma infections were detected. An analysis of the economic effects of immunisation was made.

Animals↗
PubMed1999

Towards a permanent solution for controlling cattle ticks.

Acaricides are essential in the short-term but do not offer a permanent solution to tick control. This situation will not change without a change of approach. A vaccine against Boophilus microplus confers partial long-term control but has little immediate effect on tick burdens. The effectiveness of acaricides and vaccination is greatest for breeds of high tick resistance. High host resistance is the key to effective long-term tick control with total resistance the ultimate aim. While improvements to acaricides and vaccines are continuously pursued, improvements to the most important single factor controlling ticks, host resistance, have been neglected. Resistance is as heritable as milk yield or growth and in tropical breeds can be increased to very high levels by selection. Despite this there are no current examples of sustained selection for tick resistance. Temperate breeds have low resistance but because of high production potentials are favoured for crossbreeding with tropical breeds. This perpetuates the need for reliance on acaricides. Selection to increase polygenic resistance of temperate breeds is impractical. However, a quantum increase can be achieved by introgressing major resistance genes. Such a gene occurs in the Belmont Adaptaur and in suitable genetic backgrounds confers 100% resistance. Total resistance is achievable and provides a permanent solution to ticks.

Animals↗
PubMed1990

The impact of pure infestations of Rhipicephalus appendiculatus and Amblyomma hebraeum on the productivity of cattle and implications for tick control strategies in Africa.

This paper reviews studies carried out by an FAO project in Zimbabwe, on the effects of the ticks Rhipicephalus appendiculatus and Amblyomma hebraeum on the productivity of cattle. Larvae and nymphs of the two species had no detectable effect on liveweight gain (LWG). The losses in LWG caused by each adult female that completed feeding were approximately 4 g for R. appendiculatus and 10 g for A. hebraeum. Losses in milk production caused by both species amounted to approximately 7 g for every female that engorged. The loss in productivity per engorged female, known as the damage coefficient, can be used in simulation models to estimate the value of production losses caused by the ticks and the economic benefits of control strategies.

Animals↗
PubMed2005

The use of a recombinant baculovirus expressing a chitinase from the hard tick Haemaphysalis longicornis and its potential application as a bioacaricide for tick control.

Baculoviruses are specific insect pathogens used as selective biological insecticides on lepidopteran insects. We have tested a recombinant baculovirus expressing a chitinase gene for its efficacy as a tick bioacaricide. The recombinant Autographa californica multiple nuclear polyhedrosis virus expressing a chitinase enzyme (AcMNPV-CHT1) from the hard tick, Haemaphysalis longicornis, was constructed and found to have a novel bioacaricidal effect against ticks. The recombinant baculovirus was used to express the chitinase enzyme in Spodoptera frugiperda (Sf9) insect cells. Topical application of the supernatant harvested from the insect cell culture was found to cause mortality in nymphal ticks of H. longicornis. High temperature (>30 degrees C) and infrared radiation affected the chitinase enzyme activity and recombinant baculovirus infectivity by reducing the speed of tick killing by 60%. A mixture of recombinant virus and chitinase was found to kill ticks faster (p < 0.01) than pure chitinase and recombinant virus alone. Thus, the recombinant virus showed a synergistic effect with the foreign chitinase gene. In order to reduce the excessive use and cost of acaricides, it was found that a mixture of recombinant virus and flumethrin could halve the dose of the chemical acaricide used. These findings are important for the safe use of the recombinant virus expressing chitinase as a bioacaricide against ticks.

Animals↗
PubMed1993

Seroconversion to Cowdria ruminantium of Malawi zebu calves, reared under different tick control strategies.

The seroconversion by indirect ELISA to Cowdria ruminantium over the first year of life of sixty-six Malawi zebu calves born into groups which were dipped 17 times per year was compared to seroconversion of 32 calves born into non-dipped groups. Amblyomma variegatum tick counts and clinical disease in each group of cattle were monitored throughout the study period. No cases of heartwater were seen in either group of calves over the first 22 months of life. Only one case of heartwater was observed, in an 8 year old cow, in the 1,800 intensively monitored cattle over the same period. By 12 months of age almost all undipped calves had seroconverted and 50% of seroconversions were attributed to nymphal challenge. In contrast, only 41% of calves had become seropositive by 12 months of age in the dipped groups. The dipping regime used therefore significantly decreased seroconversion rates to C. ruminantium in these calves. 73% of calves had detectable levels of maternal antibodies to C. ruminantium in the first 4 weeks of life. Antibody levels in each of the calves in dipped groups had waned to below the cut off point for the ELISA by 8-12 weeks. Seroconversion did not occur in the first 8-12 weeks of life in dipped herds. The indirect ELISA test results were not significantly different in the proportion positive in single tests at 12 months of age, or by cumulative test results of the previous 9 months, and therefore the test may be of value as a test of herd immunity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Organization and tactics of the ground tick control in the south of the Tyumen Region].

Measures for protection of the general population from the attacks of vectors of natural and focal infections were implemented by OOO "Spetsbioservis" at the expense of the regional budget in the involving foci oftick-borne encephalitis (TBE) and Ixodes tick-borne encephalitis in the south of the Tyumen Region during 2002-2004. The organizational and tactical issues of ground antitick treatments were perfected during this work. The paper describes the maximum effective completeness of teams of disinfectors and their supply with materials and equipment, as applied to local conditions. This scheme of organizational and tactical measures for acaricidal treatments in the south of the Tyumen Region in 2002-2004 has indicated their high effectiveness and mobility. In 2002-2003, tick bites were not recorded in children's health facilities. In these years, the incidence of TBE in the population of Tyumen reduced by 39.3% as compared with 2001. The qualitative implementation of acaricidal treatments, their extended scopes, successively intensified sanitary educational work among the population, and introduced personal prophylactic agents (repellents and protective clothes) will substantially affect the epidemiological situation associated with tick-borne infections in the region.

Agriculture↗
PubMed2002

Partial strategic tick control within a herd of European breed cattle in the state of Rio Grande do Sul, southern Brazil.

A trial is described, in the state of Rio Grande do Sul, southern Brazil, as one of a series suggested to investigate the effects of strategic but selective acaricide treatments of cattle within herds against Boophilus microplus. They are aimed at considering the repercussions of farmer attempts at immediate reductions in acaricide costs and the potential for creation of 'refugia' of untreated ticks. Half (Group 1) of a small experimental herd of European breed heifers were treated strategically against ticks, three times during the late spring-early summer and twice during autumn (southern hemisphere), with an injectable avermectin endectocide, designed to act directly against the first and third generations of parasitic B. microplus per 'cattle tick year' at this site, respectively. The consequent levels of infestations on all of the member cattle in their common pasture were monitored. Group 1 showed low to zero tick counts during the 28-day treatment interval periods and up to ca. 14 days after the last of such a series. Treated cattle, however, became re-infested outside of these periods and to levels that would be considered as unacceptable by farmers in the state. The untreated cattle (Group 2) showed infestations at generally higher levels, than their contemporaries, within and outside of the treatment periods. There were thus ample sources of larvae in the pasture, derived principally from falling, untreated engorged female ticks, re-infesting both the treated and untreated cattle. Advantages of maintaining chemically untreated cattle ticks within a herd, compared to their disadvantages as contaminants to classical strategic control procedures, merit re-evaluation, especially in relation to the recent, world-wide resurgence of acaricide resistance in B. microplus.

Animals↗
PubMed2000

Salivary glands in ixodid ticks: control and mechanism of secretion.

The salivary glands are vital to the biological success of ixodid ticks and the major route for pathogen transmission. Important functions include the absorption of water vapor from unsaturated air by free-living ticks, excretion of excess fluid for blood meal concentration, and the secretion of bioactive protein and lipid compounds during tick feeding. Fluid secretion is controlled by nerves. Dopamine is the neurotransmitter at the neuroeffector junction regulating secretion via adenylate cyclase and an increase in cellular cAMP. Dopamine also affects the release of arachidonic acid which is subsequently converted to prostaglandins. Prostaglandin E(2) (PGE(2)) is secreted at extremely high levels into tick saliva for export to the host where it impacts the host physiology. Additionally, PGE(2) has an autocrine or paracrine role within the salivary gland itself where it interacts with a PGE(2) receptor to induce secretion (exocytosis) of bioactive saliva proteins via a phosphoinositide signalling pathway and an increase in cellular Ca(2+). Regulation of fluid secretion has been extensively studied, but little is known about the mechanism of fluid secretion. Continuing advances in tick salivary gland physiology will be made as key regulatory and secretory gland proteins are purified and/or their genes cloned and sequenced.

Journal Article↗
PubMed2003

Winter activity of Ixodes scapularis (Acari: Ixodidae) and the operation of deer-targeted tick control devices in Maryland.

Host-seeking activity of adult blacklegged ticks, Ixodes scapularis Say was monitored by flagging during winter months in Beltsville, MD. Ticks were active many days during January and February, the coldest months, with some captures made when there was 70% snow cover and temperatures as low as -2 degrees C. Substantial numbers (70-90 ticks/h of flagging) of adult I. scapularis were captured on favorable days in January and February. The cost to treat white-tailed deer, Odocoileus virginianus (Zimmermann), using '4-poster' deer self-treatment devices, was estimated on a per female tick basis. We estimated deer abundance and tick attachment rates using data from the literature, tick activity levels using weather data and drag counts of ticks, and costs to operate the devices from experience. We found that self-treatment devices need not be operated continuously from late December until the third week of February. On average, savings of half the operating costs would be realized by not operating the devices when tick activity was low.

Animals↗
PubMed1990

Perspectives for subunit vaccines for the control of ticks.

For the first time, successful vaccination against a tick has been carried out using a single defined antigen. Further, it has been shown that it is feasible to produce active antigenic material by recombinant DNA technology. This represents a significant advance towards the development of an alternative means of tick control. Nevertheless, as with any new product and new technology, much developmental work still has to be done before one can be confident that a practical means of tick control will result. From the published information, it does not seem that research on vaccines against other tick species is as advanced as that on Boophilus microplus. The work on B. microplus may, however, provide a short cut to the development of further tick vaccines.

Animals↗