Integrated Management of the Cattle Tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) and the Acaricide Resistance Mitigation

Resistance to insecticides is one of the major obstacles to the control of agricultural pests, as well as species important to human and veterinary health. The World Health Organization has called insecticide resistance “the great little obstacle against vector-borne diseases”. Rhipicephalus (Boophilus) microplus is one of the most important vector, transmitting diseases to cattle such as anaplasmosis and babesiosis. These diseases cause great economic losses that significantly increased because of the appearance of tick populations resistant to acaricides, as a result of the intensive use of pesticides. Resistance to ixodicides in Latin America is a growing problem, since control of disease-transmitting ticks, depends heavily on the use of pesticides. In Mexico, the resistance of R. microplus to organophosphate compounds, pyrethroids, and recently amidines, has been detected in some areas, affected by multiple acaricide resistance to the three families of ixodicides. The cattle tick R. microplus in addition to the great ecological impact represents the most expensive pest for livestock in Mexico, since the producers are directly affected by this tick, due to the decrease in the production of meat, milk and damage to the skin, as well as the indirect damage, such as the transmission of diseases, including Anaplasmosis and Babesiosis, which, in turn, represents a serious limitation for the introduction of specialized cattle in endemic areas. Therefore, the use of integrated management programs is a mandatory issue that should be implemented in all those areas affected by this parasite.

Potential causes of Acaricide Resistance in Rhipicephalus and Amblyomma Ticks (Acari: Ixodidae) in Namwala District, Zambia

Acaricide resistance in ticks poses a great threat to livestock production in many parts of the world where ticks are a problem. The objectives of this study were to screen for acaricide resistance in Rhipicephalus and Amblyomma ticks using phenotypic and molecular assays, and to assess current tick control practices used by cattle farmers in the traditional sector of Namwala District. The larval packet test was used to screen for acaricide resistance in ticks covering concentrations up to twice the discriminatory dose for amitraz, diazinon and cypermethrin. Genetic mutations associated with resistance to amitraz (A22C-T8P and T65C-L22S), and organophosphates/ pyrethroids (G1120A) were screened using polymerase chain reaction and sequencing. Information on tick control practices at the household level was collected using a semi-structured questionnaire. Intermediate resistance (21-50%) to amitraz and cypermethrin was detected in both Rhipicephalus and Amblyomma ticks, with both tick genera showing susceptibility to diazinon (<10%). None of the ticks in this study had the reported acaricide resistance-conferring molecular markers that were screened for. The findings suggest that the resistance detected in the studied tick population may be due to other mechanisms that are yet to be identified. Tick control practices observed amongst the farmers, such as incorrect use of acaricide concentrations and rotations could be fuelling the development of acaricide resistance. It is critical to comprehensively unravel the factors that could be contributing to acaricide treatment failure as this would allow for application of appropriate remedial actions for effective tick control in Zambia.

Short communication: Potential causes of Acaricide Resistance in Rhipicephalus and Amblyomma Ticks (Acari: Ixodidae) in Namwala District, Zambia

Acaricide resistance in ticks poses a great threat to livestock production in many parts of the world where ticks are a problem. The objectives of this study were to screen for acaricide resistance in Rhipicephalus and Amblyomma ticks using phenotypic and molecular assays, and to assess current tick control practices used by cattle farmers in the traditional sector of Namwala District. The larval packet test was used to screen for acaricide resistance in ticks covering concentrations up to twice the discriminatory dose for amitraz, diazinon and cypermethrin. Genetic mutations associated with resistance to amitraz (A22C-T8P and T65C-L22S), and organophosphates/ pyrethroids (G1120A) were screened using polymerase chain reaction and sequencing. Information on tick control practices at the household level was collected using a semi-structured questionnaire. Intermediate resistance (21-50%) to amitraz and cypermethrin was detected in both Rhipicephalus and Amblyomma ticks, with both tick genera showing susceptibility to diazinon (<10%). None of the ticks in this study had the reported acaricide resistance-conferring molecular markers that were screened for. The findings suggest that the resistance detected in the studied tick population may be due to other mechanisms that are yet to be identified. Tick control practices observed amongst the farmers, such as incorrect use of acaricide concentrations and rotations could be fuelling the development of acaricide resistance. It is critical to comprehensively unravel the factors that could be contributing to acaricide treatment failure as this would allow for application of appropriate remedial actions for effective tick control in Zambia.

Acaricide resistance in Panonychus citri and P. ulmi (Acari: Tetranychidae): Molecular mechanisms and management implications

The European red mite, Panonychus ulmi (Koch), and the citrus red mite, P. citri (McGregor) (Acari: Tetranychidae), are destructive mite pests in pome/stone fruit orchards and citrus groves, respectively, the management of these two spider mites species has relied largely on the use of synthetic acaricides. However, frequent, long-term use of acaricides has caused rapid development of resistance in P. ulmi and P. citri populations worldwide. Levels of resistance in P. ulmi and P. citri are exceeded only by that in the two-spotted spider mite, Tetranychus urticae Koch. Recent research on T. urticae has provided new insights into the molecular mechanisms of acaricide resistance. The molecular basis of resistance in P. ulmi and P. citri populations has been less thoroughly studied. In this brief review, the current understanding of the molecular mechanisms of toxicokinetic and toxicodynamic resistance of P. ulmi and P. citri to acaricides, as well as implications of the findings for the resistance management, are discussed.

Rhipicephalus Tick: A Contextual Review for Southeast Asia

Rhipicephalus species are distributed globally with a notifiable presence in Southeast Asia (SEA) within animal and human populations. The Rhipicephalus species are highly adaptive and have established successful coexistence within human dwellings and are known to be active all year round, predominantly in tropical and subtropical climates existing in SEA. In this review, the morphological characteristics, epidemiology, and epizootiology of Rhipicephalus tick species found in SEA are reviewed. There are six commonly reported Rhipicephalus ticks in the SEA region. Their interactions with their host species that range from cattle, sheep, and goats, through cats and dogs, to rodents and man are discussed in this article. Rhipicephalus-borne pathogens, including Anaplasma species, Ehrlichia species, Babesia species, and Theileria species, have been highlighted as are relevant to the region in review. Pathogens transmitted from Rhipicepahalus ticks to host animals are usually presented clinically with signs of anemia, jaundice, and other signs of hemolytic changes. Rhipicephalus ticks infestation also account for ectoparasitic nuisance in man and animals. These issues are discussed with specific interest to the SEA countries highlighting peculiarities of the region in the epidemiology of Rhipicephalus species and attendant pathogens therein. This paper also discusses the current general control strategies for ticks in SEA proffering measures required for increased documentation. The potential risks associated with rampant and improper acaricide use are highlighted. Furthermore, such practices lead to acaricide resistance among Rhipicephalus species are highlighted.