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The use of a 4% (w/w) deltamethrin collar (Scalibor ProtectorBand) in the extended control of ticks on dogs.

Deltamethrin (4%, w/w) formulated in a polymer matrix system (Scalibor ProtectorBand, Intervet International BV) was evaluated for the prevention of ticks on dogs. Controlled laboratory trials were conducted, wherein dogs wearing anti-tick collars were compared with control dogs and artificially infested by adult Ixodes ricinus and/or Rhipicephalus sanguineus ticks. The activity of the collars increased from 24 to 48 h post-treatment (pt) wherein tick numbers were reduced to 78.7% for I. ricinus and to 77% for R. sanguineus. The proportion of ticks controlled after the second infestation on D7 pt increased to 99% for I. ricinus and 99.5% for R. sanguineus. For I. ricinus adult ticks, an efficacy of 95.4% was reached over a period of 5.5 months and approximated 90% for R. sanguineus. Hence, the efficacy of the deltamethrin-impregnated dog collar was >90% for 6 months against both tick species. There was no significant difference between the efficacy of the collar against either R. sanguineus or I. ricinus. A subsequent field study wherein 82 dogs were wearing the collar and monitored for tick infestation indicated that the duration of efficacy was between 5 and 6 months.

Animals↗

Effect of different East Coast fever control strategies on disease incidence in traditionally managed Sanga cattle in Central Province of Zambia.

A clinical trial, including five East Coast fever (ECF) control strategies (involving tick control and/or immunisation by infection-and-treatment) in five different groups of traditionally managed Sanga cattle, was conducted in Central Province of Zambia over 2.5 years between 1992 and 1995. Two groups were kept under intensive tick control by weekly acaricide treatment by hand spray; (one immunised and one non-immunised), two groups were under no tick control (one immunised and one non-immunised), and a fifth, immunised group was maintained under strategic tick control (18 sprays yr-1). ECF-specific mortality was highest in the non-immunised and non-treated group, while no difference in ECF-specific mortality could be observed between animals treated for ECF by immunisation or by tick control. Acaricide treatment and/or immunisation reduced the risk of clinical ECF by 92%. The results of an artificial challenge experiment at the end of the field trial indicated that about 60% of the animals in the control group had become infected with Theileria parva without showing clinical signs. ECF incidence in non-vaccinated cattle markedly declined six months after immunisation--suggesting that the carrier state induced by immunisation did not lead to a persistent high incidence, and might accelerate the progress to endemicity.

Animals↗

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↗

Methods for control of tick vectors of Lyme borreliosis.

During the IVth International Conference on Lyme Borreliosis in Stockholm, 1990, a workshop on control of Lyme disease vectors briefly reviewed: basic ecological principles for tick control; biocontrol of ticks; chemical control, including the use of repellents and use of permethrin-treated rodent nest material; tick control by habitat modification; and reduction of tick host availability. It was concluded that, although much research work remains, Lyme borreliosis is to a large extent a preventable infection. Avoidance of heavily tick-infested areas, personal protection using proper clothing, and prompt removal of attached ticks remain the most effective protective measures. Many other prophylactic measures are available and could be efficiently integrated into schemes to reduce the abundance of vectors. However, since the ecology of the infection varies greatly between different localities it may be necessary to apply different combinations of control methods in different endemic regions.

Animals↗

A critical evaluation of the role played by the red-billed oxpecker Buphagus erythrorhynchus in the biological control of ticks.

Buphagus erythrorhynchus uses 4 feeding methods--scissoring, plucking, pecking and insect catching. During the day the birds spend 68% of their time feeding, with peaks of activity during the early morning and late afternoon. A total of 21 641 ixodid ticks were found in 53 stomachs examined, with a range of between 16 and 1 665 per stomach. Boophilus and Rhipicephalus were the most important genera eaten. Thirty Diptera, also found in the stomachs, accounted for 0,4% of the diet by mass. The food of the nestlings consisted of 45,6% ticks, 19,4% Diptera and 35,0% hair and tissues. When kept in captivity, Buphagus was able to account for an appreciable reduction in the numbers of Boophilus on cattle, reaching a figure of 95,7% reduction for adult ticks. In controlled experiments Buphagus showed the highest preference for Boophilus decoloratus, Rhipicephalus appendiculatus and Hyalomma truncatum. The daily food intake of a captive bird was 14,7% g, which is equivalent to 7 195 engorged Amblyomma hebraeum larvae. Three acaricides, namely, amitraz, chloromethiuron and DDT, did not cause any clinically detectable toxicity in captive birds during a 5-day period.

Animals↗

Effect of different East Coast Fever control strategies on fertility, milk production and weight gain of Sanga cattle in the Central Province of Zambia.

Five different East Coast Fever (ECF) (Theileria parva infection) control strategies, based on tick control and/or ECF immunization, were tested in groups of traditionally managed Sanga cattle in the Central Province of Zambia over a period of 2.5 years. Two groups were kept under intensive tick control (sprayed weekly), one group immunized and one non-immunized. Two further groups were under no tick control, one group immunized and one non-immunized, while a fifth group was immunized against ECF and maintained under strategic tick control (18 sprays per year). Tick control increased milk production and weight gain but not fertility. Immunization had neither marked detrimental nor beneficial effects on the cattle productivity. The combination of strategic tick control and immunization resulted in the highest level of production and at the same time reduced the potential risk from other tick-borne diseases.

Animal Husbandry↗

Heartwater in Ghana: implications for control of ticks.

Heartwater, an often fatal rickettsial disease of domestic ruminants transmitted by Amblyomma variegatum ticks, ranks with the A. variegatum-associated skin disease dermatophilosis as a major constraint to the upgrading of livestock productivity in Ghana. An epidemiological survey, using new diagnostic tests, is being carried out to determine the incidence and distribution of heartwater and other tickborne diseases in Ghanaian cattle, sheep and goats. Preliminary results from a longitudinal survey being carried out at sites in the Greater Accra Region indicating that although the vector ticks and the disease agent are widespread outside urban areas, not all animals are being exposed to heartwater during the first few months of life when an inverse age related resistance allows development of immunity without clinical disease. Thus a susceptible sub-population, at risk from heartwater, can exist even in areas of high tick challenge. The significance of these results for present and future tick and disease control strategies is discussed.

Animals↗

Immunology of the tick-host interaction and the control of ticks and tick-borne diseases.

The first experimental vaccination against ticks was carried out 60 years ago. Since then, progress has been slow, although the recent commercial release of a recombinant vaccine against Boophilus microplus is significant. The nature of naturally acquired protective immunity against ticks is poorly understood, particularly in the important, domesticated ruminant hosts. Characterization of the antigens of naturally acquired immunity remains limited, although more has been achieved with 'concealed' antigens. Crucial questions remain about the true impact of tick-induced immunosuppression and the effect of immunity on the transmission of tick-borne diseases, despite some fascinating and important recent results, as discussed here by Peter Willadsen and Frans Jongejan.

Animals↗

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↗

Autocidal control of ticks by silencing of a single gene by RNA interference.

Ticks impact human and animal health worldwide and new control methods are needed to circumvent drawbacks of tick control by acaricide application including selection of drug resistant ticks and environmental pollution. Using RNA interference we silenced the expression of a single gene, subolesin, and produced ticks with diminished reproductive performance and prevented successful mating and production of viable offspring. We propose a sterile acarine technique (SAT) for reduction of tick populations by release of subolesin-silenced ticks. Conservation of subolesin among tick species suggests that SAT may be useful for control of many medically and economically important tick species.

Animals↗

Effectiveness of fenitrothion for area control of ticks Ixodes ricinus (L.).

Susceptibility to fenitrothion in all stages of unfed ticks Ixodes ricinus increases with their age and this fact is reflected in the effectiveness of various dosages of insecticides applied for area control. The following minimum, but fully effective dosages of the dust Metation P-5 and the spray Metation E-50 (both preparations contain fenitrothion) for application in separate seasons have been ascertained: In September and October 1 kg of fenitrothion per ha of treated area ensures complete control of unfed ticks until the winter of current year. In Aril 3 kg of fenitrothion per ha is necessary, if tick control is to be ensured until the appearance of the new generation, i.e. until the end of August. In May the control of unfed ticks is ensured by 1 kg of fenitrothion per ha, in June to August by 0.3 kg per ha is fully efficacious.

Animals↗

The effect of East Coast fever immunisation and different acaricidal treatments on the productivity of beef cattle.

A trial was performed on a farm in the Coast Province of Kenya to study the effects of East Coast fever immunisation and different acaricidal treatments on the productivity of immunised and unimmunised beef cattle. Eighty cattle were immunised against Theileria parva parva (Marikebuni) by the infection and treatment method and a similar group was left as an unimmunised control. Immunisation had no deleterious effect on the cattle. After immunisation, the immunised and control groups were each subdivided into four groups of 20 and each subgroup was managed under a different tick control regimen. The tick control regimen were, acaricidal spraying twice a week or once every three weeks, the application of acaricide-impregnated ear-tags, and no tick control. During a nine-month exposure period there were 18 cases of East Coast fever among the 80 immunised cattle, three which were severe and the others mild. Among the 80 unimmunised cattle there were 57 cases of East Coast fever, 50 of which were severe. The highest morbidity and mortality occurred in the groups under limited tick control or without tick control. Overall weight gain in the immunised cattle, irrespective of the tick control regimen, was better than the weight gain in the unimmunised groups. Within the immunised groups, the weight gain of the cattle sprayed twice weekly was comparable to the weight gain of the animals with acaricidal ear-tags and was significantly higher than the weight gains in the groups sprayed once every three weeks or with tick control. Preliminary cost/benefit analysis showed that it was uneconomical to maintain unimmunised cattle under limited or no tick control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Reproductive and safety assessment of vaccination with Gavac against the cattle tick (Boophilus microplus).

Recent developments in cattle tick control have incorporated the use of recombinant Bm86 vaccines against this ectoparasite. The vaccine developed by our group (Gavac) contains an antigen expressed in Pichia pastoris, and has been successfully employed for the control of tick infestations and transmission of tick-borne diseases. Here, we examined the safety and effect of the Gavac vaccine on reproductive parameters in cattle. Toxicity tests in mice and guinea pigs demonstrated the safety of Gavac. To study the adverse effects of vaccination on reproduction, a field trial involving 9,500 animals in Cuba was conducted. The cattle at 3 farms were vaccinated while those on a fourth farm were left unvaccinated and served as the control. Following vaccination, the control of tick infestation and the transmission of babesiosis were used to demonstrate the efficacy of the vaccine. No adverse effects were observed in any of the reproductive parameters studied when comparing the data before and after vaccination with Gavac and between the vaccinated farms and the control farm. These results demonstrate that under the conditions of our study vaccination with Gavac is safe for use on cattle.

Abortion, Veterinary↗

Control of ticks.

A number of different acaricides provide highly effective control of tick populations on dogs and cats. These acaricides are formulated as sprays, dips, dusts, or shampoos for use on the animal. Further protection of the animal from reinfestation with ticks can be achieved with the use of acaricide-impregnated flea and tick collars. Some of these acaricides are registered with the EPA for indoor and outdoor use as controls for free-living populations of ticks. Caution should be used when applying these materials. The label directions for the application of the acaricide and disposal of the acaricide containers should always be followed. Removal of underbrush and leaf litter, thinning trees, and frequently mowing grasses help reduce the number of free-living ticks. Any reduction in the amount of wildlife food sources and cover areas potentially decreases populations of ticks and thus reduces the potential of these ticks parasitizing a dog or cat. Application of an acaricide for area-wide control of free-living ticks in the spring, summer, and autumn also reduces the number of ticks. New approaches to area-wide control of ticks by use of acaricides that are focused on controlling the ticks attached to small mammal hosts are discussed. Although research has shown that reductions in tick numbers can be achieved using these methods, acceptance of these methods by regulatory agencies and the public requires further research.

Animals↗

Long-term studies on the economic impact of ticks on Sanga cattle in Zambia.

Three different tick control policies were tested in groups of traditionally managed Sanga cattle in the Central Province of Zambia over a period of 3 years. One group was given strategic tick control using 12 pyrethroid acaricide spray applications between the onset and the end of the wet season (October to March). The productivity of this herd was compared with that of a group with no tick control and a group under an intensive tick control regimen of spraying every week in the wet season and every 2 weeks in the dry season (36 applications per year). The highest output was associated with intensive tick control, followed by strategic control and then no tick control policies. However, when the costs of tick control were taken into account, the strategic tick control policy produced the best economic result, followed by the intensive and then the no tick control policies. Neither the strategic nor the intensive tick control policy was sufficient to prevent the transmission of East Coast fever (ECF) infection when this disease was introduced to the area.

Animals↗

Control of the bush tick (Haemaphysalis longicornis) with Zebu x European cattle.

Brahman x Hereford cattle carried only one-quarter as many engorging adult bush ticks (Haemaphysalis (Kaiseriana) longicornis) as Hereford. Simmental x Hereford or Friesian x Hereford cattle when grazed together on the north coast of New South Wales. Fourteen percent of a Brahman x Hereford herd carried half of the engorging ticks suggesting that infestation levels would be further reduced by culling procedures. The results indicate an additional advantage to those already established for Brahman x Hereford cattle on the north coast of New South Wales and have important implications for tick control.

Animals↗

Pesticide use by licensed applicators for the control of Ixodes scapularis (Acari: Ixodidae) in Connecticut.

To assess the use of insecticides for tick control by commercial applicators in Connecticut, a questionnaire was mailed to 897 individuals and businesses with ornamental and turf pesticide applicator licenses. In total, 348 completed surveys were returned (38.8%). The majority of the respondents considered themselves lawn care (41.1%), landscape (31.3%) or tree care (12.6%) providers. Tick control services were offered by 16.4% (n = 57) of the respondents, all of whom apply insecticides for tick control, mainly for Ixodes scapularis Say. Over half (n = 33) also treat for the American dog tick, Dermacentor variabilis (Say). Most respondents (66.7%) began applying pesticides for the control of I. scapularis during the period from 1990 to 1996. The principal acaricide used for tick control was cyfluthrin (n = 21), with chlorpyrifos 2nd (n = 18), carbaryl 3rd (n = 12), and fluvalinate (n = 4) 4th. When asked about what other pesticides were used for tick control, the top 3 chemicals also were the principal alternatives. Past success with a product was the dominant factor in selecting a pesticide, but information provided by the Connecticut Agricultural Experiment Station (New Haven), Cooperative Extension (University of Connecticut, Storrs), and scientific studies were important. Half of the respondents (49.1%) indicated that their tick control business had increased slightly or dramatically since 1991, although tick control comprises < 5% of their overall business for 63.1% of these applicators. Residential properties comprised 90% of the business for half of those treating for ticks, and the median charge for 0.4 ha was $180. Many respondents (43.8%) also indicated that they planned to expand their tick control services. Tick control represents a small but growing business in Connecticut.

Animals↗