[Field trials to control the bee tick Varroa jacobsoni with Folbex-VA-NEU and biotechnical measures on a bee farm in Tunisia].
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Animals↗
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Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
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[Trial results with dilor in controlling the taiga tick].
Laboratory and field trials of dilor (beta-dihydroheptachlorine) have demonstrated its high acaricidal characteristics, but this pesticide is not recommended as a means for extermination of Ixodes persulcatus, tick-borne encephalitis virus vectors. The tested compound is characterized by a high persistence, superior even to that of DDT. Dilor metabolites retain their toxicity in the forest up to 4-5 years.
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Subunit vaccines for the control of tick-borne diseases: implications for the future.
Tick-borne parasites are a major constraint to the improvement of livestock productivity in the developing world. These parasites include Theileria parva, T. annulata, Babesia bigemina, B. bovis, Anaplasma marginale and Cowdria ruminantium. The impact of these diseases is currently limited by the use of acaricides to decrease transmission by the tick vectors and immunization of the host animals using live vaccines. The use of acaricide is hampered by the development of acaricide resistance and live vaccines are dependent on cold chain facilities, which are generally unreliable in developing countries. There is therefore a requirement for improved vaccines that circumvent these problems. Candidate vaccine antigens have been identified for most of these parasites and are currently being evaluated for their capacity to induce solid protection.
Anaplasma↗
Hyalomma truncatum (Acari; Ixodidae): investigations into the scototaxis of unfed adult ticks.
Under controlled test conditions, unfed male and female Hyalomma truncatum ticks exhibited a positive scototaxis to stationary, two-dimensional targets. Upright-positioned rectangles were the most attractive targets. The attractiveness of these targets increased with their size. Significantly more ticks responded scototactically positively to the targets under a luminance contrast ratio of 5:1, as compared with other luminance contrast ratios. Targets with an elevation angle of 13 degrees were occupied more frequently than objects with higher elevation angles. Scototaxis was the same towards a stationary and a sinusoid oscillating target. When an upright-positioned rectangle was combined with a CO2 gradient, the number of ticks that migrated into the CO2 gradient and contacted the target did not increase significantly. The interval between exposure and first locomotion of the ticks, however, was significantly shorter under the influence of a CO2 gradient than in all other experiments without a CO2 gradient. A temperature gradient simulating a natural host (cattle) did not alter the scototaxis. The results of these investigations suggest that the positive scototaxis exhibited by adult H. truncatum ticks is not likely to be part of their appetence behaviour but rather searching behaviour to find adequate protection from harsh climatic conditions.
Animals↗
Vaccines against Theileria parva.
Bovine theileriosis caused by Theileria parva continues to be a major economic problem in many parts of Eastern, Southern, and Central Africa. Due to the unsustainable nature of the present control method--using toxic acaricides to kill ticks--alternative control methods are being sought. Live vaccines are being used in many countries in the region. These vaccines are based on the infective sporozoite stage of the parasite. Sporozoites are inoculated in cattle with simultaneous administration of a long-acting formulation of oxytetracycline. These vaccines are poorly adopted in the region, mainly because of problems associated with the use of live parasites. An experimental recombinant vaccine based on a sporozoite surface antigen (p67) has been developed. Immunization with this antigen induces neutralizing antibodies and, under laboratory conditions, this technique protects approximately 70% of the immunized cattle to a defined needle challenge. The efficacy of the vaccine is currently being evaluated under field challenge in Kenya. Since a vaccine based on a single antigen may not be sustainable under field conditions, a search for schizont antigens that induce protective cell-mediated immune responses continues. It is expected that the ultimate vaccine against theileriosis will incorporate a mixture of several antigens derived from both sporozoite and schizont stages, contributing to robust immunity.
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Vaccination against ticks (Boophilus spp.): the experience with the Bm86-based vaccine Gavac.
The control of tick infestations and the transmission of tick-borne diseases remain 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 B. microplus gut antigen Bm86 have been developed. Our vaccine formulation (Gavac, Heber Biotec S.A., Havana, Cuba) has been registered and is commercially available in Cuba, Colombia, Dominican Republic, Brazil and Mexico. In controlled pen trials, Gavac has been effective for the control of artificial infestations of B. annulatus, B. decoloratus and chemical-sensitive and resistant B. microplus strains from Australia, Africa, America and Iran. In controlled field trials in Cuba, Brazil, Argentina and Mexico, Gavac has shown a 55-100% efficacy in the control of B. microplus infestations in grazing cattle 12-36 weeks after the first vaccination. Field trials under production conditions have been conducted in Cuba, Colombia, Brazil and Mexico in pure and cross-bred cattle herds. The application of Gavac has increased the time between acaricide treatments by an average of 32 /-21 days (P = 0.0005) resulting in important savings for the cattle industry. In Cuba, a cost-effectiveness analysis was conducted in more than 260000 animals. The cost-effectiveness analysis showed a 60% reduction in the number of acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of 23.4 dollars animal(-1) year (-1). These results clearly demonstrate the advantage of vaccination and support the application of Gavac for the control of Boophilus spp. infestations.
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Control and eradication of chelonian tick infestations, with particular reference to vectors of heartwater.
Studies using the African tortoise tick (Amblyomma marmoreum) and leopard tortoises (Geochelone pardalis) demonstrated that cyfluthrin and permethrin were safe and efficacious acaricides for control of Amblyomma ticks on tortoises. A protocol was developed that successfully eradicated an A. sparsum infestation from a tortoise breeding facility in Florida. It involved treatment of all tortoises with a permethrin formulation, followed by treatment of the premises with a cyfluthrin formulation. Sentinel tortoises were later placed on the treated premises to establish successful tick eradication.
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Preventing Lyme disease.
Five species of ixodid ticks that frequently feed on humans, Ixodes dammini, I. scapularis, I. pacificus I. ricinus, and I. persulcatus, are competent vectors of B. burgdorferi. Collectively, these species are distributed over vast areas of North America, Europe, and Asia. Lyme disease is becoming prevalent because of increased human exposure to infected ticks. Chemical and environmental methods of controlling these ticks over large areas will be difficult because none of these species is concentrated in a particular habitat. In relatively small local areas and special habitats such as islands, ticks may be reduced significantly by application of chemicals or by altering the environment. For example, areas surrounding homes may be successfully treated with timely applications of chemicals; reductions in ticks may be achieved by eliminating significant host animals, such as deer. Satisfactory biologic methods of control are presently unavailable. Personal protection efforts taken by the individual, such as using repellents on clothing or skin, wearing clothing that prevents ticks from easily gaining access to skin, and locating and removing attached ticks promptly, may be the most effective measures that can be taken to reduce risk of contracting Lyme disease.
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Effect of acaricide control of Amblyomma variegatum ticks on bovine dermatophilosis on nevis.
A sentinel group of 8 Bos taurus cattle was compared with similar cattle in a herd of 90 of which 21 were pastured with the sentinels. The sentinel group was not treated with acaricide whilst the rest of the cattle were treated weekly with the organophosphate acaricide ethion. Weekly counts of adult ticks and rankings of dermatophilosis were made on the sentinel herd. The remaining cattle were observed for the presence of ticks and dermatophilosis prior to the weekly treatment with acaricide. All sentinel cattle became infested with Amblyomma variegatum ticks and dermatophilosis developed on all. Rank correlations of tick numbers and dermatophilosis scores were between +0.34 and +0.98, varying with maturity of cattle and time during the trial. Incidence of dermatophilosis on the cattle treated with acaricide was very low. Tick numbers on the sentinel animals were compared to rainfall and temperature. It is concluded that acaricide is the best option for controlling bovine dermatophilosis in Nevis.
Actinomycetales Infections↗
Control of lone star ticks (Acari: Ixodidae) on Spanish goats and white-tailed deer with orally administered ivermectin.
Ivermectin administered orally to Spanish goats, Capra hircus (L.), or to white-tailed deer, Odocoileus virginianus (Zimmerman), was highly effective against lone star ticks, Amblyomma americanum (L.). For Spanish goats, daily oral doses of 20 micrograms/kg resulted in greater than or equal to 2 ppb ivermectin in the blood. This level was sufficient to cause greater than 95% reduction of estimated larvae from feeding ticks. A bioassay with horn flies, Haematobia irritans (L.), was developed to estimate oral intake of ivermectin. Probit analysis of dose-mortality data indicated that a 50% reduction in adult horn fly emergence can be expected when the manure from goats treated orally with ivermectin at 10, 20, 35, and 50 micrograms/kg/d was mixed with untreated cow manure at a rate of 0.345, 0.110, 0.100, and 0.092%, respectively. In studies with white-tailed deer, daily oral doses of 35 and 50 micrograms/kg/d provided 100% control of adult and about 90% control of nymphs that were placed on treated fawns. A single oral dose of 50 micrograms/kg gave greater than 90% control of adult and nymphal ticks attached to treated fawns at the time of drug administration and 70% control of ticks placed on treated deer three days thereafter. When ticks were placed on fawns treated with a single dose of ivermectin (50 micrograms/kg) the engorgement period was longer, ticks were lighter in weight, and females laid fewer eggs than ticks detaching from control fawns. A single oral dose of ivermectin at 20 micrograms/kg prevented about 60% of the adult and nymphal ticks attached at the time of drug administration from engorging, but did not affect other ticks placed on the animals after treatment.
Administration, Oral↗
Methods currently used for the control of heartwater: their validity and proposals for future control strategies.
Major advances made in the last few years in the knowledge of heartwater have not yet resulted in significant improvement of its prevention and control. Acaricide resistance and the high cost of chemical vector control stimulate research on alternative methods of vector control, such as immunization against the tick and the use of pheromones. Recently developed in vitro methods for the culture of Cowdria ruminantium may make it possible to arrive at safe recombinant or molecular vaccines. Specific chemotherapy may be improved by new laboratory screening methods, and studies on the pathogenesis of heartwater could lead to better non-specific treatment as well. Studies on the heritability of natural resistance to heartwater should determine whether or not practical selection and transfer of resistance is feasible. More research is also needed on the immunology and diagnosis of the disease and the factors involved in the resistance of young animals.
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Observations on Hunterellus sp. (Hymenoptera: Encyrtidae) parasitizing Haemaphysalis bispinosa Neumann, 1897 (Acarina: Ixodidae).
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Animals↗
Control of arthropod vectors of disease in Nigeria - a review.
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Animals↗
Control of an exotic tick (Aponomma komodoense) infestation in a Komodo dragon (Varanus komodoensis) exhibit at a zoo in Florida.
A protocol was developed to control an exotic tick (Aponomma komodoense) infestation on three Komodo dragons (Varanus komodoensis) at a Florida zoo without direct application of acaricides to the lizards. With the Komodo dragons secured within their indoor pens, their outdoor enclosures and the exhibition area were sprayed with a formulation of permethrin prepared specifically for use with reptiles. Once the acaricide had dried, the Komodo dragons were allowed to return to their outdoor enclosures, whereupon the indoor pens were closed and sprayed with the same formulation. After this initial treatment, the outdoor and indoor areas were retreated every 2 wk and 8-10 wk, respectively, for 6 mo. The initial on-host and off-host tick count of 301 ticks fell to 0 ticks after 6 mo. No adverse effects of the acaricide treatment were observed on the lizards during daily monitoring.
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Effect of controlling natural field-tick infestation on the growth of N'Dama and Gobra zebu cattle in the Gambia.
The effect of tick infestations on liveweight gain (LWG) was assessed by comparison of weight changes in flumethrin-treated N'Dama and Gobra zebu cattle (16-20 months old) with respective control groups submitted to natural tick challenge over 1 year. Flumethrin was applied monthly, fortnightly or weekly. Preventive treatments against anaplasmosis, babesiosis and trypanosomosis were given. Mortality rate was recorded and post-mortem examinations carried out. In both treated and control animals, significantly fewer Hyalomma spp. and Amblyomma variegatum were found on N'Dama than on Gobra zebu cattle. Both breeds are equally susceptible to Rhipicephalus senegalensis infestation. Total annual tick burdens did not cause significant differences in LWG between acaricide-treated and control cattle in either breeds. LWG was also not affected during or after the annual peak of tick infestation (composed mainly by A. variegatum and R. senegalensis). Equally-high mortality (35%), due to unidentified causes, was recorded in acaricide-treated and control Gobra cattle; mortality in N'Dama cattle was 7.5%. In both breeds, about the 90% of mortality occurred at the end of the dry season. Breed differences in tick burden confirm previous results. If tick-borne infections do not influence LWG or mortality, then it is concluded that intensive tick control is not justifiable in Gambian livestock.
Anaplasmosis↗
Simulation of control strategies for the cattle tick Boophilus microplus employing vaccination with a recombinant Bm86 antigen preparation.
Current strategies for the control of the cattle tick Boophilus microplus include the use of chemicals as the principal control method. These methods, however, have met with partially successful results. The recent development of immunological methods for the control of the cattle tick has opened new possibilities for the design of control strategies. Employing the results obtained by us in experiments testing the effect of vaccination with the recombinant vaccine, Gavac (Heber Biotec S.A.), on tick populations, we have developed a model to evaluate, through a computer program, the efficacy of the vaccine as a control method. The action of the vaccine on the control of tick populations was simulated and the specific serum antibody titers required to decrease the tick population in the field were calculated. The specific serum antibody titer required to decrease the tick population in the field after the first vaccination scheme was found to be > or = 57,200 and the antibody titer required to maintain this effect when the vaccine is already acting and after successive revaccinations was found to be > or = 27,500. Considerations about revaccination schemes and combination between vaccination and acaricide treatments as possible control strategies are discussed.
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Diagnosis of amitraz resistance in Boophilus microplus in New Caledonia with the modified Larval Packet Test.
The tick Boophilus microplus represents a serious pathological constraint to livestock production in New Caledonia. Cattle ticks are controlled by chemical application of two acaricides that are currently used in New Caledonia; deltamethrin is used at 46% of the cattle production facilities and amitraz at the remaining 54% premises where resistance to deltamethrin has been identified. In 2003, a modified Larval Packet Test (LPT) was used to conduct a survey for amitraz resistance. Ticks were collected from 29 farms, including farms using deltamethrin (n=8) or amitraz (n=21). Of eighteen different tick populations, sixteen populations were defined susceptible to amitraz and two populations were considered amitraz-resistant. This is the first report of populations of B. microplus being resistant to amitraz, using the modified LPT in New Caledonia. A thorough survey of tick susceptibility to amitraz in cattle farms of the country should be conducted to assess the presence of amitraz-resistant populations. The emergence of amitraz resistance so soon after its introduction has some important implications for the strategy and organisation of tick control in New Caledonia, and this paper discusses some of the urgent actions that should be undertaken.
Animals↗
A reappraisal of vector control strategies for babesiosis.
This review suggests that we are on the threshold of a new epoch in the control of ticks and the diseases transmitted by them. Ecological studies of parasitic and non-parasitic stages of the tick life cycle have shown how strategic dipping can lead to effective control of Boophilus ticks. However, this approach can lead to drastic reduction in tick populations which may favour the development of enzootic instability. On the other hand, mathematical models and field studies indicate that we can eradicate babesiosis without eradicating the tick vector. As no well-established vaccine exists for babesiosis or its vectors, it is important to anticipate the possible effects of low or fluctuating populations of ticks caused by strategic control programmes. Under these conditions, it is probable that babesiosis will disappear before the tick vector does. Prudent use of tick bionomic data from several centres of field research, as well as models to analyse these data, should accelerate the latter process. Epidemiological models should be included in the analysis of babesiosis in areas that run the risk of converting from stable zones to unstable zones due to strategic dipping. These observations and projections underscore the value of integration of traditional and modern techniques in the control of babesiosis and other vector-borne diseases.
Analysis of Variance↗