The poultry red mite (Dermanyssus gallinae) causes severe welfare concerns for laying hens arising from anaemia and disease transmission, and has been identified as an associated risk factor in cannibalistic feather pecking. Previous work suggests that essential oils may offer an alternative to synthetic acaricides to control D. gallinae. Such alternatives are needed due to the limitations of synthetic acaricides (eg availability, resistance, environmental concerns and product residues). The aim of the current study was to ensure that selected essential oils have no negative impact on either hen welfare or egg production. To achieve this aim, small groups of laying hens were confined in poultry huts for a period of eight weeks during which time the interior of the huts was sprayed at weekly intervals with one of four different treatments: i) Thyme essential oil at 5× the LC90 level (the concentration of oil previously found to kill 90% of D. gallinae under laboratory conditions) for D. gallinae in 500 ml of water, ii) Pennyroyal essential oil at 5× the LC90 level for D. gallinae in 500 ml of water, iii) Solvent-only (huts treated with 500 ml of water); and iv) Pseudo-spray where huts were not treated with any product, but subjected to sham-spraying. The results suggest that pennyroyal essential oil would not be suitable for further development as an acaricide for D. gallinae, since this treatment had to be terminated early in the study period as a result of concerns about the welfare of hens exposed to this oil. Conversely, there were few differences in feather condition, hen weight, feed intake, feeding efficiency, egg production or egg weight between thyme-treated huts and huts that were either pseudo-sprayed or sprayed with solvent-only (water). It is concluded that thyme essential oil is a promising candidate for further development as an acaricide for D. gallinae to help safeguard the welfare of laying hens in commercial poultry systems.

Parasite-mediated apparent competition occurs when one species affects another through the action of a shared parasite. One way of controlling the parasite in the more susceptible host is to manage the reservoir host. Culling can cause issues in terms of ethics and biodiversity impacts, therefore we ask: can treating, as compared to culling, a wildlife host protect a target species from the shared parasite? We used Susceptible Infected Recovered (SIR) models parameterized for the tick-borne louping ill virus (LIV) system. Deer are the key hosts of the vector (Ixodes ricinus) that transmits LIV to red grouse Lagopus lagopus scoticus, causing high mortality. The model was run under scenarios of varying acaricide efficacy and deer densities. The model predicted that treating deer can increase grouse density through controlling ticks and LIV, if acaricide efficacies are high and deer densities low. Comparing deer treated with 70% acaricide efficacy with a 70% cull rate suggested that treatment may be more effective than culling if initial deer densities are high. Our results will help inform tick control policies, optimize the targeting of control methods and identify conditions where host management is most likely to succeed. Our approach is applicable to other host-vector-pathogen systems.

Glutathione transferases (GSTs) are a family of multifunctional enzymes with fundamental roles in cellular detoxication. Here we report the molecular characterization of 3 recombinant GSTs belonging to the mu- and delta-class from the parasitic mite Sarcoptes scabiei. Kinetic constants were determined, and the effect of acaricides, including organothiophosphates, pyrethroid esters, a formamidine, a macrocyclic lactone, an organochlorine as well as a bridged diphenyl acaricide, on the activity of the GSTs were tested using 1-chloro-2,4-dinitrobenzene (CDNB) as model substrate. Our results showed that enzymes from the same class and with high amino acid sequence identity have significantly different kinetic properties. For instance, one mu-class GST lost more than 50% of its activity in the presence of one of the organothiophosphates while the activity of the second mu-class GST was only slightly reduced under identical conditions. Tertiary structure modulations indicated that structural differences were the crucial factor for the different kinetic patterns observed. Genome analysis showed that the two mu-class GSTs are organized in tandem in the S. scabiei genome. Taken together these results show that GSTs might be involved in the metabolism of acaricides in S. scabiei.

The development of new acaricides is a long and very expensive process. Worryingly, there is increasing resistance to available acaricides worldwide leading to the real possibility that our dwindling supply of effective acaricides will be exhausted unless action is taken to increase the number of new acaricidal products and reduce the rate of resistance development. In 1995, eight major animal health pharmaceutical companies formed the Veterinary Parasite Resistance Group (VPRG) to act as an expert consultative group to guide the FAO in resistance management and collaborate in the prudent use of acaricides. In this paper, members of the VPRG discuss the problems and processes in acaricide development, resistance in the field to commonly used acaricides and the different considerations when targeting the cattle and pet market, and give their view of the future for tick control from the perspective of the animal health industry.

Toward the end of the nineteenth century a complex of problems related to ticks and tick-borne diseases of cattle created a demand for methods to control ticks and reduce losses of cattle. The discovery and use of arsenical solutions in dipping vats for treating cattle to protect them against ticks revolutionized tick and tick-borne disease control programmes. Arsenic dips for cattle were used for about 40 years before the evolution of resistance of ticks to the chemical, and the development and marketing of synthetic organic acaricides after World War II provided superior alternative products. Most of the major groups of organic pesticides are represented on the list of chemicals used to control ticks on cattle. Unfortunately, the successive evolution of resistance of ticks to acaricides in each chemical group with the concomitant reduction in the usefulness of a group of acaricides is a major reason for the diversity of acaricides. Whether a producer chooses a traditional method for treating cattle with an acaricide or uses a new method, he must recognize the benefits, limitations and potential problems with each application method and product. Simulation models and research were the basis of recommendations for tick control strategies advocating approaches that reduced reliance on acaricides. These recommendations for controlling ticks on cattle are in harmony with recommendations for reducing the rate of selection for acaricide resistance. There is a need to transfer knowledge about tick control and resistance mitigation strategies to cattle producers.

Ticks have always been a major obstacle to livestock production due to the devastating diseases which they transmit especially in the tropics. The control of ticks which has relied heavily on the use of acaricides is now faced with serious problems e.g. increased resistance in ticks, high costs and toxicity to the environment. Over the last few decades, alternative tick control methods which utilize natural factors with little or no acaricides have been sought and those which have shown some promise are discussed in this paper. They include release or conservation of biological control agents e.g. parasitoids, predators and pathogens; anti-tick grasses and pasture spelling. The possibility of integrating some of these factors into low cost environmentally-safe tick control strategies affordable by resource limited farmers is also discussed.

Deltamethrin (IR, 3R)-3(2,2-dibromovinyl)-2, 2-dimethylcyclopropane carboxylate of (S)-alpha-cyano-3-phenoxy-benzyl, was observed in the field in Zambia to offer a better residual effect against adult Rhipicephalus appendiculatus of up to 7 days post-treatment during a high infestation pressure period than on organophosphorus (OP) acaricide. A group of 20 cattle sprayed with deltamethrin wash of approximately 0.005 w/v at 14 days intervals carried an average of less than 12 ticks per head by the 7th day post-treatment, whereas two groups of 20 cattle each, dipped weekly in an OP at 0.05% w/v had an average of over 60 ticks per head. In a theileriosis infected area 14 days' treatment with deltamethrin would probably be unsuitable for disease control during high infestation period, but 7–10 days would probably yield better results than those likely to be obtained with OPs.