Pallavi Khajuria, Gurpreet Singh2, Dr. Rachana Sharma4 and Dr. Amit Challana3
1 Assistant Professor, 2 Associate Professor, 3 Assistant Professor, 4 Assistant Professor
Department of Veterinary Physiology and Biochemistry
Department of Veterinary Anatomy
College of Veterinary Science, Rampura Phul
Guru Angad Dev Veterinary and Animal Sciences University
Despite advances regarding prophylaxis and treatment of parasitic diseases, parasites are still responsible for significant morbidity and mortality in companion animals. As ectoparasites are responsible for economic losses to livestock producers, control measures are necessary.
A number of different control methods are available to prevent and/or treat ectoparasites which are enlisted below:
1. Hygiene Management control: One strategy to control fly populations is the systematic removal of dung and manure, coupled with the implementation of proper drainage systems to eliminate breeding grounds. Manure can be consolidated into large heaps where the heat generated during fermentation can effectively destroy fly larvae. Additionally, the application of insecticides on smaller manure heaps can further reduce the prevalence of flies. Grazing practices should be intensified to minimize vegetation growth, supplemented by periodic plowing and cultivation of grazing areas to create an inhospitable environment for ticks and their developmental stages. In regions where pastureland is scarce, ticks may seek refuge in cracks and crevices within animal shelters, necessitating measures to minimize such habitats. Regular grooming of animals and the installation of wire mesh or nets around animal enclosures can also aid in tick control efforts.
2. Chemical control: The most widely utilized method globally for insect and acarid control faces several challenges, including the development of resistance, public concerns regarding residues in food and environmental pollution. Various chemicals such as carbamates (aldicarb, propoxur), chlorinated hydrocarbons (DDT, BHC, aldrin), organophosphates (Diazinon, malathion), synthetic pyrethroids (cypermethrin, deltamethrin, permethrin), formamidines (amitraz), and macrocyclic lactones (ivermectin, melbemycin, doramectin) are employed. Among these, synthetic pyrethroids have demonstrated superior residual activity against a wide spectrum of pests at lower doses. However, macrocyclic lactones are also commonly used. Herbal products like neem seed oil, tea tree oil, and other plant extracts have been explored as alternatives. Nevertheless, many ectoparasites have developed resistance to various insecticide groups, leading to concerns of multiple resistances. The indiscriminate use of insecticides can have adverse effects on non-targeted species and result in unacceptable chemical residues in food, posing health risks to humans.
Various application methods for insecticides and acaricides include topical sprays, hand and powder dust applications, pour-on, spot-on, feed additives, injectables, tail bands, back rubbers, dips, and ear tags. Some insects can be controlled using mist or fog insecticides, baits, larvicidal and residual sprays, especially when targeting them away from hosts. The choice of methodology depends on factors such as the target insects, available labor, current management practices, and the cost-effectiveness of the proposed treatment.
3. Biological control: Biological control involves utilizing, manipulating, and leveraging one life form to reduce the population of another. Bio-pesticides offer several advantages, including a narrow spectrum of activity, targeting only specific insects, gradual impact, ensuring around 90-100% target mortality while preserving beneficial insects. They are cost-effective, typically requiring only two to three applications, and do not lead to resistance development. Additionally, they are biodegradable, leaving no residues and causing no pollution. Biopesticides are safe for livestock, fishes, birds, and humans. They can originate from plants such as grasses or from zoological sources like bacteria, fungi, viruses, parasites, and predators.
Insect growth regulators hinder or control insect growth, inducing sterility, ovicidal effects, reducing reproduction, and causing deformities due to disrupted metamorphosis. These regulators may originate from chemicals (chryomizine, methoprim, chymoprim) or plants (azarone, azadirachtin). Bacteria like Bacillus sphaericus and Bacillus thuringiensis are widely used antagonists developed against mosquitoes, culicoides, and ticks. Bacillus thuringiensis, a gram-positive, spore-forming bacterium, produces insecticidal proteins, primarily Cry and Cyt toxins, during the sporulation phase. These toxins are highly specific to their target insects, harmless to livestock, plants, and humans, and fully biodegradable, making it a viable alternative for insect pest control in agriculture and vector control.
Fungi, such as Beauveria bassiana and Metarhizium anisopliae, can grow on insect cuticles, causing damage and mortality. Metarhizium anisopliae has shown effectiveness against Boophilus microplus ticks. Parasites like Hunterellus hookeri serve as natural enemies of ticks, while fire ants prey on Amblyomma ticks, and birds like Bubulcus africanus and B. erythrhynchus help control tick populations. Gambusia affinis preys on mosquito larvae, and guppy fish has been employed against culicoides and mosquitoes. Certain plants, like Andropogon gayanus and Melinis minutiflora, possess tick repellent properties, while various extracts of Stylosanthes exhibit acaricidal properties.
4. Immunological control: Vaccines present several advantages compared to traditional chemical acaricides. They provide sustained action, are typically residue-free, inherently specific, cost-effective, and resistant to resistance development. Various antigens sourced from ticks have been examined as vaccine candidates.
Extensive experiments led to the discovery of the concealed BM86 antigen, which has been expressed in E. coli and Pichia pastoris to produce recombinant tick vaccines Tickgard and Gavac, respectively, targeting Boophilus microplus. A second-generation vaccine, Tickgard plus, has also been developed for B. microplus, offering enhanced and prolonged immunity.
Additionally, another recombinant antigen, Bm95, extracted from Boophilus microplus ticks, has been utilized to combat resistant tick strains alongside Bm86. It is proposed that Bm95 could serve as a universal antigen protecting against infections by various geographical strains of Boophilus microplus. Immunizing animals with synthetic peptides derived from the Bm86 glycoprotein of Boophilus microplus gut has demonstrated effectiveness in tick control. Recent studies focusing on a dual-action anti-tick vaccine, targeting both exposed and concealed antigens, have shown promising outcomes. Ticks that fed on immunized animals elicited a sustained inflammatory response and increased antibody titers, leading to the demise of engorged ticks due to mid-gut damage.
5. Pheromone-mediated control: Specific pheromones play crucial roles in the mating behavior of arthropods and in attracting females to susceptible hosts. Some pheromones, known as aggregation attachment pheromones (AAP), facilitate the aggregation or attachment of unfed nymphs and adult ticks. These AAPs can be strategically utilized by integrating them into plastic tags infused with insecticides. As the tags release pheromones gradually, they attract ticks, effectively serving as “tick decoys.”
6. Sterile insect technique: Sterile insect release is a biological control method involving the release of large numbers of sterile insects. Typically, only male insects are released since it is the females that cause damage by laying eggs in crops or, in the case of mosquitoes, by taking blood meals from humans. The sterile males compete with wild males for female insects. When a female mates with a sterile male, it produces no offspring, thereby reducing the population of the next generation. Repeated releases of sterile insects can eventually lead to population reduction, although it’s often more practical to aim for population control rather than complete eradication. However, the sterilization process using radiation can weaken newly sterilized insects if doses are not properly administered, making them less competitive against wild males.
7. Genetic tick control: The use of acaricides is a common method employed to manage cattle ticks. However, misuse of these chemical compounds has led to the development of tick resistance to various pesticides available in the market, consequently shortening the effectiveness of these products. Additionally, concerns about the presence of chemical residues in meat, milk, and the environment have underscored the necessity for improved monitoring of their application. Therefore, researching genetic resistance to ticks among different breeds of cattle can aid in developing alternative control methods. It is well-established that Bos indicus cattle exhibit greater resistance to ectoparasites compared to Bos taurus animals. Significant differences exist between these two breeds concerning their susceptibility to parasitism by cattle ticks. Efforts are underway to intensify studies on the crossbreeding of these two groups, aiming to produce animals that are more resistant to tropical conditions and remain proficient meat producers.
Conclusion: Management of ectoparasitic infestations in dairy animals is crucial for maintaining their health and productivity. Ectoparasites like ticks, mites, lice, and flies can cause irritation, skin damage, and transmit diseases, leading to economic losses in dairy farming. Effective management involves a combination of preventive measures and treatment strategies. Thus implementing these management practices, dairy farmers can effectively control ectoparasitic infestations, improve animal welfare, and optimize milk production. Regular monitoring and adaptation of control strategies are essential for long-term success.