[Ecological bases for the control of ixodid ticks].
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[Control of the tick Dermacentor marginatus].
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Animals↗
Control of equine piroplasmosis in Brazil.
The importance of equine piroplasmosis control in endemic countries has increased in recent years and plays an important role to maintain the international market open to the horse industry. The purpose of this study was to demonstrate the occurrence of equine piroplasmosis (Babesia equi or Theileria equi and Babesia caballi) in Brazil--a country where the disease occurs endemically--in different climatic conditions, and to evaluate the results of a strategy for tick control in order to decrease infection rates. Blood samples were taken from 720 horses on 28 farms from different regions and subjected for complement fixation testing. The strategy was based on the control of the tick population by spraying the horses with acaricides, treating positive horses and preventing cattle and horses from grazing together. A significant association was found in the prevalence of antibody titres in tropical and subtropical areas. A significantly lower prevalence rate occurred on those farms where measures to control tick population were established. Farms in endemic countries may significantly reduce the prevalence of equine piroplasmosis by establishing measures to control the tick population and treating chronic carrier horses. Additional measures for controlling ticks in tropical areas are also discussed.
Animals↗
Performance of two Bm86 antigen vaccin formulation against tick using crossbreed bovines in stall test.
Cattle tick control remains a serious problem for cattle farms in Brazil due to the limited success achieved with chemicals. In Brazil, the use of vaccines for tick control associated with the use of chemicals and pasture rotation may open possibilities for integrated control. However, it is important to know whether regional Boophilus microplus strains are sensitive to antibodies produced by the available antigens: antigen preparations Gavac™ and TickGard(PLUS). The aim of this research was to evaluate the performance of two Bm86 antigen vaccine formulation against tick using crossbred bovines in stall test antigen against a regional B. microplus strain. The experiment was carried out in central Brazil (20 degrees 27'S, 54 degrees 37'W). A trial was conducted in stall conditions on crossbred cattle under controlled infestation. Two groups of 16 animals each, homogeneous in weight and sex, were vaccinated with Gavac™ or TickGard(PLUS), two groups of eight animals as control. Challenge was performed on three alternate days, with 5,000 larvae each time, beginning 21 days after the second injection. The antibody response was measured by ELISA and vaccinated animals presented immune response considering IgG levels. The results showed 49.2% and 46.4% protection efficacy for Gavac™ and TickGard(PLUS), respectively.
Animals↗
An experimental study of east coast fever in Uganda. I. A study of the type of east coast fever reactions produced when the number of infected ticks is controlled.
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Animals↗
Factors related to cattle infestation level and resistance to acaricides in Boophilus microplus tick populations in New Caledonia.
Boophilus microplus, even in the absence of babesiosis, is a major disease of the cattle in New Caledonia where the particular farming system associates continental European breeds and a tropical climate tempered by the Pacific Ocean. In order to have a better understanding of the factors involved in cattle tick infestation, to decrease the possible wastage and use of chemicals and to increase the lifetime of the acaricides, the veterinary authorities investigated the conditions of the chemical treatments. A survey among 148 cattle farms of the whole of New Caledonia was carried out and factors that explain the development of tick resistance and cattle infestation have been determined. From this survey, three typologies for the main characteristics of the farms have been set up, the technical practices of the farmers and the tick control measures applied by the farmers, respectively. Some variables are significantly associated with the tick resistance to deltamethrin but their contribution to the explanation model is always moderate: farms in the south, with a positive resistance gradient from east to west, absence of bush fire and membership to a cattle farmers organization. The more the farmers have intensified their breeding-male castration, weaning, heifer separation, drenching, etc.-and pasture-high stock rate, mowing, extra feeding of the cows, many paddocks, etc.-techniques, the higher was the probability for the ticks in their farm to be resistant to deltamethrin. The technical details of the acaricide treatment had a low contribution to the explanation model. However, the use of a spray generated more resistance than a dip. Furthermore, there is a negative resistance gradient when the farmers increased the treatment interval average. Considering infestation, none of the variables from the three typologies were associated with the two infestation variables (1: semi-engorged tick females and 2: other ticks) at the herd level. However, the seven studied variables-the three typologies, breed, age, body condition score and breeding status-affected significantly the two infestation variables at the cow level, but their predictive ability remained very low (R(2)<3.5%). This result-individual effect more important than herd effect on the infestation-is confirmed by the importance of the variance of the intra-farm factors (99%) when compared with inter-farm factors (1%). Cows of Charolais breed, in poor body condition, old, pregnant or lactating, and those of the farms with irrational and high pressure control of ticks are the most infested.
Agriculture↗
[Results of fumigation in the control of ticks Ixodes persulcatus; results of activities of the combined expedition of the Institute of Malaria, Medical Parasitology, and Helminthology of the Ministry of Public Health of USSR, of the D. I. Ivanovskii Institute of Virology of the Academy of Medicine of USSR, of the Kuibyshev Regional Station for the Control of Malaria during 1954].
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Animals↗
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↗
Boophilus microplus tick burdens on grazing cattle in Colombia.
This study was conducted at Carimagua Research Centre in a well-drained savanna area in the eastern plains of Colombia. The objectives were to note the effect of ecological factors on tick burdens, principally the effect of the environment given by four grasses on the seasonal variations of tick populations. Adult female tick counts were carried out on heifers grazing four pastures and tick larvae on the grass detected by cloth dragging. Tick counts were significantly higher on animals grazing Brachiaria decumbens than those grazing Andropogon gayanus, Melinis minutiflora or native pastures. Tick larvae counts on the grass showed a similar tendency. Introduced grasses and intensification of production will require greater care to control tick infestations since increases in stocking rate and ground coverage could augment tick populations.
Animals↗
A model to simulate the effect of vaccination against Boophilus ticks on cattle.
This paper describes a vaccination model to simulate the effect of cattle vaccination with concealed antigens on Boophilus tick spp. The model considers the vaccination effect in three parts: antibody titer, accumulation of damaging vaccination effects by parasite stages, and the effect of accumulated damage on all tick life stages. Biological parameters for ticks and hosts, as well as parameters describing tick-host interaction, were included. The validity of this model, integrated with the TICKSIM simulation program, was demonstrated for the Bm86-containing vaccine Gavac by comparing simulated and real data for several geographic locations in the Americas. All model parameters were estimated using field data collected in the different geographic locations. The model sensitivity to changes in antibody titer level and titer half-life was studied, and the impact on tick population density of changes in these parameters was evaluated. Simulation results showed that to achieve a higher level of tick control, an increase in the maximum antibody titer levels was more important than extending titer half-life in geographical locations with short seasonal peaks of tick infestation. The TICKSIM program, integrated with the new vaccination model, proved to be a framework for designing and evaluating tick control strategies, including vaccination with GavacTM.
Animals↗
In vitro detection of acaricide resistance in Boophilus microplus (Acari: Ixodidae).
The cattle tick Boophilus microplus causes significant economic losses in cattle in the tropical areas of Central and South America. Acaricides are widely used to control tick infestations, with the consequent selection of tolerant and resistant subpopulations. Detoxifying enzymes, and esterases in particular, have been associated with organophosphate resistance in Mexican isolates of B. microplus ticks. Here, we present results of the biochemical detection of esterases and oxidases in 20 isolates of larvae and adult ticks and the effect of esterase and oxidase inhibitors on larvae and adult stages of the tick. Our results indicate the presence of significant differences both in vivo and in vitro between esterase and oxidase activities of OP-susceptible and OP-resistant isolates, even when samples were collected in the same area. The importance of such differences in regionalized integrated pest management and in the US Tick Eradication Program is discussed.
Acetylcholinesterase↗
Microbiological control of ticks.
Twelve isolates (9 spore-forming bacteria and 3 fungi) were obtained from a dead adult tick (female) that had failed to lay eggs. There were different internal changes in the tick's eggs, caused by inoculation with these isolates. Such changes differed according to the type of microorganisms under study. However, fungi were more effective than spore-forming bacteria in decreasing hatching percentage of tick's eggs at 28 degrees C. Generally, inoculation with these isolates decreased the longevity of unfed larvae of ticks.
Animals↗
The efficacy of ethion EC (1010 g/l) against cattle ticks in Morogoro, Tanzania.
Ethion, an organophosphorus insecticide/acaricide, was found to be effective against the various cattle ticks present in Morogoro Tanzania after it was sprayed on cattle twice weekly for 1 year. The pre- and post-replenishment concentrations of ethion ranged between 0.04 and 0.05%. Ethion was found to be stable in the spraywash. The good efficacy makes ethion a good alternative to dioxathion in tick control in Tanzania.
Animals↗
The induction of host resistance to tick infestation with a salivary gland antigen.
Salivary gland antigen, SGA, derived from partially engorged female Dermacentor andersoni was shown to be capable of inducing resistance to tick infestation in guinea pigs never previously exposed to ticks. Immunization regimens involved the administration of SGA by different routes and with or without the use of adjuvants. Induced resistance was expressed by significantly fewer larvae engorging, and the weight of larvae which did engorge was reduced. Salivary gland antigen has been shown to interact with the immune effector elements of animals which acquired and expressed tick resistance due to infestation. These findings demonstrated the potential for an immunologic approach to tick control.
Adjuvants, Immunologic↗
Flea (Siphonaptera:Ceratophyllidae, hystrichopsyllidae) and tick (Acarina:Ixodidae) control on wood rats using host-targeted liquid permethrin in bait tubes.
The efficacy of a liquid permethrin-treated bait tube controlling fleas and ticks on Mexican wood rats, Neotoma mexicana Baird, was evaluated during a 1-yr study in north-central Colorado. Results indicated that the bait tubes were effective for reducing flea and tick infestations on wood rats. The effects of treatment persisted throughout the study, despite the fact that bait tubes were replenished with bait and permethrin only during the first 4 mo (4 replenishments). Our results suggest that these bait tubes provide an effective, economical, and environmentally acceptable means of controlling vectors of flea or tick-borne diseases, although slight modifications of the basic bait tube design might be required to maintain the effectiveness of the tube under different ecological conditions.
Animals↗
Tick resistance to acaricides in western Ethiopia.
A survey of acaricide resistance was performed on ticks collected from 18 dairy farms and 6 veterinary clinics in western Ethiopia. Boophilus decoloratus collected from most of the dairy farms were resistant to toxaphene, but no resistance was detected in ticks collected from indigenous cattle. There is a need in Ethiopia to replace toxaphene on dairy farms and formulate a rational tick control policy for the whole country.
Animals↗
Tick survey on goats and sheep in Kenya.
A tick survey was done on sheep and goats in Siaya and Kakamega Districts, Kenya between October 1980 and October 1981. Most of the animals were found to carry one to 10 ticks with no significant difference between sheep and goats. The most abundant species was R. appendiculatus followed by R. evertsi. There were more male than female ticks found on the animals. Thirty per cent of the farms visited practised the hand picking method of tick control while 14% regularly dipped their animals.
Animals↗
Study on immunobiology in ectoparasites of public health interest: Rhipicephalus sanguineus.
The recently defined range of Mediterranean Spotted Fever (MSF) in Sardinia coincides with that of the widely studied Rickettsia conorii vector, the brown dog tick Rhipicephalus sanguineus. This tick is major vector of disease in humans, domestic and wild animals. Characteristic features of the vector with respect to their seasonal activity, abundance as well as incidence of human-tick contact and how these factors influence the incidence of MSF were studied. This paper also looks at host, pathogen and tick vector interactions, re-examining some of the immunobiological parameters involved. However, the primary objective of this research is to develop a strategy that will allow better and safer tick control.
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