Strategies for the control of Rhipicephalus microplus ticks in a world of conventional acaricide and macrocyclic lactone resistance

Abstract

Infestations with the cattle tick, Rhipicephalus microplus, constitute the most important ectoparasite problem for cattle production in tropical and subtropical regions worldwide, resulting in major economic losses. The control of R. microplus is mostly based on the use of conventional acaricides and macrocyclic lactones. However, the intensive use of such compounds has resulted in tick populations that exhibit resistance to all major acaricide chemical classes. Consequently, there is a need for the development of alternative approaches, possibly including the use of animal husbandry practices, synergized pesticides, rotation of acaricides, pesticide mixture formulations, manual removal of ticks, selection for host resistance, nutritional management, release of sterile male hybrids, environmental management, plant species that are unfavourable to ticks, pasture management, plant extracts, essential oils and vaccination. Integrated tick management consists of the systematic combination of at least two control technologies aiming to reduce selection pressure in favour of acaricide-resistant individuals, while maintaining adequate levels of animal production. The purpose of this paper is to present a current review on conventional acaricide and macrocyclic lactone resistance for better understanding and control of resistant ticks with particular emphasis on R. microplus on cattle.

Economic and Health Impact of the Ticks in Production Animals

“…Common signs associated with hemoparasitic disease are: fever, anemia, decreased appetite [9], reduction in milk production [9][10][11], lower weight gain [12,13], loss of body condition, reproductive effects in males and females, abortions in the last third of gestation [9], lower pregnancy and birth rate [13], death in some animals [9][10][11][12].…”

“…The economic impact is strongly linked to the epidemiology of the disease and can be distributed in direct and indirect losses [9]. Its direct effect on production, results in damage to the skins by biting, especially in highly infested cattle [4,11,13,16]; blood loss associated with high parasitic loads, anemia [4,13,16]; severe immunological reactions by the inoculation of toxins (antigens and coagulants in saliva) [4,13]; permanent stress that affects the behavior and welfare of the animal [9,13,16] which also leads to depression of the immune function [17]; loss of energy associated with the constant movement that occurs in response to infestation [13].…”

“…Indirect losses are related to the effects of hemoparasites and other diseases that they can transmit [4,9,11,17]. Other indirect losses correspond to the cost of treatment for clinical cases; expenses incurred in the control of ticks; unearned income or inefficiencies in the production system: use of genetically resistant breeds to ticks but less productive; confiscation by acaricide residues in meat or milk; trade restrictions of animals between areas and countries [9].…”

“…In order to reduce the possibility of resistance, Rodriguez-Vivas et al [11] recommend an integral control of ticks whose strategies include: rotation of acaricides, with active ingredients that have different mechanisms of action, and without cross-resistance potential; correct application of acaricides, in recommended doses and intervals of time. According to Betancur [39], it is always recommended, to use products with proven effectiveness; in addition, the author recommend to reduce the selection pressure of the toxic compound on the pest species, in other words, the complete elimination of ticks in cattle by the pesticide should be avoided.…”

“…Other strategies of an integral control program of ticks are: manual elimination (only practical on farms with small number of infested animals); use of breeds resistant to ticks and the pathogens they transmit; release of sterile male ticks; sowing of plants that are unfavorable for ticks; rotation of pastures with forced breaks in order to interrupt the life cycle of the tick; burning of pastures, exposing the different stages of the ticks at high temperatures, and eliminating the vegetation that protects them; quality animal nutrition to improve resistance to ticks; use of plant extracts and essential oils with acaricidal activity; vaccination; biological control with nematodes, entomopathogenic fungi, ants, birds, among others [11]. The use of chickens as biological controllers of cattle ticks has been suggested, leaving them in the meadows where they consume the ticks that are found in the vegetation [43].…”