Assessment of the efficacy of parasiticides for the control of tick infection in dogs under field conditions: what's new?

For their biological and ecological characteristics, ticks are vectors of the widest variety of pathogens causing tick-borne diseases (TBDs). Little information is available about the ways in which time spent by ticks to feed on hosts, transmission times and TBD prevention are related and it is exclusively limited to laboratory reports on adult stages. In particular, the time required by immature stages to transmit pathogens has not been determined for most TBDs. Considering their importance for animal and human health, effective control of immature ticks is advisable to reduce the damage ticks cause. Recently, the efficacy of a combination of imidacloprid 10%/permethrin 50% was compared with that of fipronil 10%/S-methoprene 9% against ticks when administered to naturally infected dogs. A semi-quantitative method was used to assess the methodological parameters to calculate drug efficacy on immature stages. On adult ticks, the efficacy of both products was high and overall very similar, whereas for the immature stages the combination of imidacloprid 10% and permethrin 50% had a higher efficacy than fipronil 10% and methoprene 9% throughout the observation period (statistically significant difference on day + 28 only). The semi-quantitative method proposed for the evaluation of immature stages can be considered a useful tool for calculating the efficacy of a drug in the field. Due the important role of immatures in the spread of TBDs, the immature tick load should be calculated to assess the efficacy of acaricidal products both under laboratory and field conditions.     

Tick-borne haemoparasitic diseases in small ruminants in Pakistan: Current knowledge and future perspectives

Livestock industry is an essential part of Pakistan’s economy, and a variety of ruminants (including sheep and goats) are reared for the increasing demand of milk, meat and hide products. Haemoparasitic illnesses such as theileriosis, anaplasmosis, and babesiosis are a significant health risk for small ruminants in our country. Information regarding distribution patterns, the tick species involved and effective strategies to control tick-borne diseases (TBD) in goats and sheep of Pakistan is limited. To this end, it is required to assess the present rank of TBDs in small ruminants of Pakistan with a note on their vector ticks in order to control and identify the gaps in the knowledge of TBDs. This will recommend areas for future research and will add to the understanding of these diseases and will draw attention to the need for better-quality tools for the diagnosis and control of TBDs in small ruminants of Pakistan.     

Historical review and insights on the livestock tick-borne disease research of a developing country: The Philippine scenario

Tick-borne diseases (TBDs) remain to be a global animal health threat. Developing countries like the Philippines is not exempt to this. Despite the potential impact TBDs can give to these countries, local government initiatives and researches remain to be limited. In the Philippines, most epidemiological studies were confined only to specific areas, and predominantly in the Northern Area. Due to its unique geography and limited studies, the current nationwide status of most TBDs could not be clearly established. This review mainly covered published studies and presented challenges in the conduct of TBD research in the Philippines, which may be similar to other Southeast Asian or developing countries. To date, reported livestock TBD pathogens in the Philippines include Anaplasma, Babesia, Theileria, and Mycoplasma spp. With the ubiquitous presence of the Rhipicephalus microplus ticks in the country, it is highly probable that other pathogens transmitted by these vectors could be present. Despite studies on different TBDs in the livestock sector, the Philippine government has not yet heightened its efforts to implement tick control measures as part of the routine animal health program for local farmers. Further studies might be needed to determine the nationwide prevalence of TBDs and the presence of other possible tick species and TBD pathogens. The Philippine scenario may present situations that are similar to other developing countries.     

West African Cattle Farmers’ Perception of Tick-Borne Diseases

Worldwide, cattle production is struggling to face the negative impacts caused by ticks and Rhipicephalus (Boophilus) microplus is one of the most harmful ticks for livestock. Most of the people in West Africa depend on cattle farming and subsistence agriculture. The presence of ticks on cattle is a major problem faced by smallholder farmers who fight for their livelihood. National and regional tick control programs could assist these rural communities in protecting their livelihoods against ticks and tick-borne diseases, but only if they take into account the targeted herders and their perception on cattle management and tick control. This paper aims to provide a better insight in the socio-economic characteristics of Beninese cattle farmers, and their perception on tick burden, as well as to document common tick control strategies. Different tick species and their seasonality are well understood by cattle herders. For tick control, many still use manual tick removal, especially in the north of the country. The high cost of acaricides, the lack of financial means of African farmers, and of the local stockbreeders in particular, limits the use of acaricides in livestock breeding in Benin. While aiming to increase the meat or milk production of their animals, stockbreeders who can afford it sometimes turn to an abusive use of acaricides, which might in time lead to an increase in tick resistance. This study remains one of the rare studies to report extensively on the perceptions of West African cattle herders.     

Amblyomma variegatum and associated diseases in the Caribbean: strategies for control and eradication in Guadeloupe

Amblyomma variegatum, introduced into Guadelopue 150 years ago, has recently spread in the Lesser Antilles and threatens North America. Two important diseases are associated with the tick: heartwater and dermatophilosis. Heartwater occurs in Guadeloupe, Marie-Galante and Antigua; acute dermatophilosis exists almost everywhere the tick is present. Both are very pathogenic for upgraded or newly-infested cattle. After 15 years of A. variegatum control in Guadeloupe, a balance is established between a tick population maintained at a low level by spraying acaricides and an animal population either completely resistant to heartwater and dermatophilosis (creole cattle) or regularly treated against ticks (upgraded cattle). An eradication campaign against A. variegatum in Guadeloupe, to avoid the spread of the associated diseases, appears technically difficult but possible, economically profitable, but socially completely utopian. We suggest for Guadeloupe a reinforced control of the tick with a persistent acaricide, hoping that a general decrease of the tick infestation rate on cattle will eliminate heartwater and acute dermatophilosis.     

Strategic tick control in Burundi

Strategic tick control is an attempt to control ticks and reduce losses in animal production due to tick infestations while decreasing the cost for this control. Tick control is understood as a necessity to achieve maximum animal production from animals raised in tick-infested areas. At the same time, it has become difficult to justify intensive, year-round tick control for local breeds and their crosses. The increasing costs of acaricides, maintenance of the infrastructures, salaries for personnel, etc. have created a tick control programme where the benefits may not be adequate to justify the expense. This has been the case in Burundi. This programme with adequate participation from the cattle owners of Burundi and organizational support from government personnel can help solve this economic problem. The strategic programme reduces the period of tick control to four months each year. Once optimal participation is achieved, this period can probably be reduced to three months (Kaiser et al., 1988). The period of treatment corresponds to when there is maximal feeding activity of adult female ticks on the bovine population within a certain region. Cattle should be treated once each week throughout the four-month period in order to prevent female tick engorgement (based on the life cycle of R. appendiculatus). This will greatly reduce the number of female ticks which are available to recycle the population of ticks in the participating area. At the same time, a certain population of ticks must be maintained in order to assure contact between the cattle, ticks, and tick-borne diseases of this particular region.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetics and tolerance to tick-borne diseases in South Italy: experience in studying native Apulian and exotic sheep breed

Tick borne diseases (TBDs), though neglected, are possibly the major constraints for livestock and agricultural production in southern Italy. The diseases affect mainly the livestock imported from foreign Northern countries. But now, very timidly indeed, the awareness that the use of native breeds could contribute to reduce the ravages of these diseases is growing. Over a period of many centuries Apulian farm animals have naturally developed the ability to thrive in TBDs endemic areas. This trait, which can be defined as tolerance to TBDs is associated with the ability to control parasitaemia and to resist the development of anaemia in the face of infection. It is a matter of fact that the hematological features of Apulian native farm animals are rather peculiar as the authors highlighted by studying the blood of these animals over a period of more than ten years. In the light of their experience the authors considered that the phenomenon of tolerance is a broad-based one and possibly not unrelated to the erythropoietic system of the Apulian animals. Thus the ability to resist anaemia per se was tested in four Altamurana sheep compared to that of four Romanov sheep. This work summarises the results obtained from the experimental anaemization of the above two breed groups and discusses the findings on the basis of a review of the authors' experience in studying TBDs in sheep.     

Could insecticide‐treated cattle reduce Afrotropical malaria transmission? Effects of deltamethrin‐treated Zebu on Anopheles arabiensis behaviour and survival in Ethiopia

Anopheles arabiensis Patton (Diptera: Culicidae) is the most widespread vector of malaria in the Afrotropical Region. Because An. arabiensis feeds readily on cattle as well as humans, the insecticide-treatment of cattle--as employed to control tsetse (Diptera: Glossinidae) and ticks (Acari: Ixodidae)--might simultaneously affect the malaria vectorial capacity of this mosquito. Therefore, we conducted field experiments in southern Ethiopia to establish whether Zebu cattle (Bos indicus L.) treated with a pour-on pyrethroid formulation of 1% deltamethrin, widely used to control ticks and tsetse, would be effective against An. arabiensis or cause the female mosquitoes to feed more frequently on humans, due to behavioural avoidance of insecticide-treated cattle. Contact bioassays (3 min exposure) showed that the insecticide remained effective for about 1 month (kill rate > 50%) against mosquitoes feeding on the flanks of treated cattle. A novel behavioural assay demonstrated that An. arabiensis readily fed on insecticide-treated cattle and were not deflected to human hosts in the presence of treated cattle. DNA-fingerprinting of bloodmeals revealed that An. arabiensis naturally feeds most frequently on older animals, consistent with the established practice of applying insecticide only to older cattle, while allowing younger untreated animals to gain immunity against infections transmitted by ticks. These encouraging results were tempered by finding that > 90% of An. arabiensis, An. pharoensis and An. tenebrosus females feed on the legs of cattle, farthest from the site of pour-on application along the animal's back and where the treatment may be least residual due to weathering. Observations of mosquitoes feeding naturally on insecticide-treated cattle showed that the majority of wild female anophelines alighted on the host animal for less than 1 min to feed, with significantly shorter mean duration of feeding bouts on insecticide-treated animals, and the effective life of the insecticide was only 1 week. Thus the monthly application of deltamethrin to cattle, typically used to control tsetse and ticks, is unlikely to be effective against An. arabiensis populations or their vectorial capacity. Even so, it seems likely that far greater impact on anopheline mosquitoes could be achieved by applying insecticide selectively to the legs of cattle.     

Livestock production and animal health in Sicily, Italy

In Sicily, as in other Mediterranean areas, livestock represents one of the most important resources for the island economy. This sector involves more than 16,000 farms of cattle and 10,000 farms of sheep and goats (respectively 6% and 15% of national production) which are actually increasing their number. Most livestock in Sicily is owned by small holders and pastoralists. Regional production of milk feeds some industries, which involve a large and increasing occupational area. Due to its peculiar geographic aspect Sicily is constituted by hill areas with sporadic grasses, therefore extensive grazing methods represent an ancient, traditional practice for using poor lands. For the control of infectious diseases Veterinary Services (VS) are based on the public regional network that is coordinated by the Ministry of Health in Rome. Even if Sicilian VS had to solve many constraints related to traditional "pastoral management system", to the lack of any sanitary background of this sector, to unknown data on the numbers of the whole livestock, the effort done in the last years has allowed to monitor for brucellosis, bovine leukemia virus (BLV), bovine TBC, swine vescicular disease (MVS) and other diseases for the majority of the farms. Tick-borne diseases (TBDs) still represent a serious impediment to the improvement of meat and milk production in the region. Every year, several outbreaks related to Theileria, Babesia or Anaplasma infections in cattle are recorded. Imported breeds pay the most expensive tribute often with a mortality rate of 100%. In the last five years more than 170 outbreaks of TBDs have been notified by our Institute although the pathogen prevalence and economical impact in the Sicilian livestock is still unknown. The outdoor grazing of the animals, far away from observation, a subclinical course of the disease, can in fact create difficulties in discovering infection and therefore the therapy is often too late. New diagnostic and control methods (PCR, vaccination) are being developed at the Istituto Zooprofilattico Sperimentale of Sicily in cooperation with other national and international laboratories (such as the University of Utrecht).     

Perspectives of creation of vaccines against tick bite for nonspecific prophylaxis of vector borne diseases

Prophylaxis of infectious diseases transferred by ticks is an important problem of contemporary medicine. One of the perspective approaches to solve this problem is the creation of vaccines against tickbite (anti-tickvaccines). Contemporary methods of the control of infectious diseases transferred by ticks are described in the review. Features of naturally and artificially acquired immunity against ticks are examined. Candidate tick antigens for the construction of vaccines against genus Ixodes tick bite are described. Perspectives of use of anti-tick vaccines against tick vector borne diseases are evaluated.     

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. This revised version was published online in July 2006 with corrections to the Cover Date.     

Invasion of West African cattle by the tick Amblyomma variegatum

Studies in Cameroon and Burkina Faso examined the invasion process of cattle by adult Amblyomma variegatum Fabricius (Acari: Ixodidae) ticks. Nearly all the ticks picked up in the pasture during grazing were found on the limb ends, near the hooves, where they temporarily attached. Then when the cattle lay down, the ticks moved from the feet towards the predilection sites, where they attached definitively. Many ticks disappeared during this displacement. All the female ticks and approximately 70% of the males were thus unable to attach to the predilection sites as long as the pioneer males had not attached and started to produce attraction-aggregation-attachment pheromones. Nevertheless, A. variegatum females and males attached to the feet in similar numbers during grazing, whether the cattle were already infested or not, indicating that stimuli originating from the hosts are powerful enough to attract both sexes. After attachment of the pioneer males, the number of ticks that successfully reached the predilection sites increased. However, even on infested animals, 40-50% of A. variegatum ticks found near the hooves after the grazing periods disappeared during the night following their capture. When moving from the temporary attachment sites towards the final ones, one-third of the ticks changed the individual host. Considering this two-stage infestation process, it is suggested that a targeted tick control, using a foot-bath, might greatly reduce cattle infestation. In particular, it could be effective in traditional herds, with animals grazing permanently during the day, lying down only once back in the night pen.     

Two initial vaccinations with the Bm86-based Gavacplus vaccine against Rhipicephalus (Boophilus) microplus induce similar reproductive suppression to three initial vaccinations under production conditions

Background

The cattle tick, Rhipicephalus (Boophilus) microplus, affects livestock production in many regions of the world. Up to now, the widespread use of chemical acaricides has led to the selection of acaricide-resistant ticks and to environmental contamination. Gavac^plus is a subunit vaccine based on the recombinant Bm86 tick antigen expressed in yeast, capable to control infestations of R. microplus under controlled and production conditions. The vaccine constitutes the core element of broad control programs against this ectoparasite, in which acquired immunity in cattle to Bm86 is combined with a rational use of acaricides. At present, the conventional vaccine scheme consists of three doses that should be administered at weeks 0, 4 and 7, followed by a booster every six months.

Results

In this study we assayed a reduction in the number of the initial doses of Gavac^plus, evaluated the time course and the level of bovine anti-Bm86 antibodies elicited, and analyzed the vaccine effect on ticks engorging on immunized cattle under production conditions. Following three different immunization schemes, the bovines developed a strong and specific immune response characterized by elevated anti-Bm86 IgG titers. A reduction in the weight of engorging female ticks, in the weight of the eggs laid and also in R. microplus viable eggs percentage was obtained by using only two doses of Gavac^plus administered at weeks 0 and 4, followed by a booster six months later. This reduction did not differ from the results obtained on ticks engorging on cattle immunized at weeks 0, 4 and 7. It was also demonstrated that anti-Bm86 antibody titers over 1:640, measured in bovines immunized at weeks 0 and 4, were sufficient to affect weight and reproductive potential of female ticks as compared with ticks engorging on unvaccinated animals. In addition, no statistically significant differences were detected in the average weight of eggs laid by ticks engorged on immunized cattle that showed anti-Bm86 specific titers in the range of 1:640 to 1:81920.

Conclusion

The administration of two initial doses of Gavac^plus containing 100 μg of Bm86 antigen to non-immunized cattle under production conditions is sufficient to affect the weight and the reproductive capacity of R. microplus engorging females. According to these results, cattle herds' manipulation and vaccine costs could be potentially reduced with a positive impact on the implementation of integrated control programs against R. microplus.     

A comparison of Ixodes rubicundus (Acari: Ixodidae) infestations on Friesian and Bonsmara cattle in South Africa

This study was conducted to compare the relative resistance of crossbred Bos indicus X B. taurus Bonsmara and B. taurus Friesian cattle to Ixodes rubicundus (Karoo paralysis tick) infestations. During periods of peak abundance of the ticks, Friesian oxen harboured almost twice or more than twice as many ticks as either Bonsmara oxen or cows. During periods of low tick abundance tick burdens on both cattle breeds were closely similar. It is envisaged that cattle can play an important role in an integrated control strategy against the Karro paralysis tick.     

Methods currently used for the control of East Coast fever: their validity and proposals for future control strategies

Restriction of cattle movements, vector control, treatment and immunization are identified as the main control methods against East Coast fever (ECF). The effectiveness of these methods is very much influenced by cultural practices, economic and political pressures and development of resistance by ticks to acaricides. The proposed strategies for the future include continued restriction of cattle movements, less intensive vector control in enzootic areas so as to maintain enzootic stability, chemotherapy and immunization of the improved cattle. In addition, research efforts to evaluate strategic vector control, develop cheaper drugs, improve the quality and delivery of the stabilate vaccine, and identify and mass produce appropriate immunogenic subunit vaccines should be intensified.     

Topically applied myco-acaricides for the control of cattle ticks: overcoming the challenges

In the absence of commercially viable and environmentally friendly options, the management of cattle ticks is heavily dependent on the use of chemical acaricides. Due to recent advances in production, formulation and application technology, commercial fungus-based biological pesticides (myco-insecticides, myco-acaricides) are becoming increasingly popular for the control of plant pests; however, they have not been used against animal ectoparasites. The literature clearly demonstrates that entomopathogenic fungi are pathogenic to ticks under laboratory conditions. Pasture applications have also shown promise while experiments on topical application have had variable results. These results suggest that major research hurdles still exist especially for the latter. Although literature on ticks and their interactions with entomopathogenic fungi exists, there is not a clear understanding on how this can be influenced by the microenvironment of the cattle skin surface. This paper critically reviews pathogen, tick target and host skin microenvironmental factors that potentially affect pathogenicity of the applied entomopathogen. Factors influencing the route of infection for topically applied myco-acaricides are also reviewed. Major researchable constraints and recommendations are identified and prioritized. In particular, there is the need for basic studies to understand the interaction of entomopathogenic fungi with the components of the skin microenvironment, to identify suitable strains, and to develop improved formulations to overcome the various challenges.     

Footbath acaricide treatment to control cattle infestation by the tick Amblyomma variegatum

Previous studies have shown that about 90% of adult Amblyomma variegatum Fabricius (Acari: Ixodidae) picked up daily by grazing cattle are still attached to the interdigital areas in the evening, when the animals return from pasture. It was therefore postulated that a targeted treatment, designed to kill the ticks attached to the feet, would limit infestation of the predilection sites. Footbaths filled with various pyrethroid formulations were used over 3 years, at the beginning of the rainy season (from mid-May to the end of July), to assess the efficacy of such a control method. It proved efficient in preventing the ticks from attaching to the predilection sites. Although five to 12 A. variegatum adults attached to each treated animal daily, and although the tick burden of the predilection sites of control cattle increased each day by four to 10 ticks, the average infestation of the predilection sites of treated cattle that were initially highly infested (over 100 ticks/animal) continuously decreased to reach a level of about 10-30 ticks/animal after 6-8 weeks of treatment. In herds with a lower initial tick burden (40-70 ticks/animal) this level was obtained within 2-3 weeks and the mean infestation subsequently remained consistently low. Footbath treatment carried out every other day during the adult peak infestation period should therefore greatly limit losses due to ticks. This method was appreciated by traditional livestock farmers, essentially because it is not time-consuming and because it requires only c. 200 mL aqueous formulation per animal at each passage. The cost of the acaricide needed to treat one animal during the peak infestation period was assessed at c. euro 0.20. This control method might also have an impact on some species of tsetse flies and mosquitoes, thereby contributing to trypanosomiasis and malaria control.     

Identification of Four Novel Rhipicephalus annulatus Upregulated Salivary Gland Proteins as Candidate Vaccines

The control of Rhipicephalus annulatus ticks in Egypt and other countries relies principally on the application of acaricides which have many drawbacks. Recently, cattle vaccination against ticks showed a potential unconventional approach to control ticks. As a target, salivary glands contain various proteins that may play specific roles during attachment, feeding and may modulate the immune system of the host. We have performed immunoscreening on expression normalized cDNA library to identify unique R. annulatus proteins from salivary gland (RaSal) that are particularly expressed during engorgement. We also present the cloning and sequencing of four novel cDNAs (RaSal1–4) from salivary glands that are expressed during feeding. RaSal4 shows 13 cysteine amino acid residues forming 6 potential disulfide bonds. We detected the expression level of the four genes during embryogenesis in eggs collected at 6, 12 and 18 days after oviposition. RT-PCR analysis detected these proteins at days 12 and 18 while slight amplification was detected at day 6 for only RaSal2. The expression of these salivary genes may put forward new vaccines to control tick infestations and tick-borne diseases.