Brazil's battle against Rhipicephalus (Boophilus) microplus ticks: current strategies and future directions

Klafke, Guilherme Marcondes; Golo, Patrícia Silva; Monteiro, Caio Marcio Oliveira; Costa-Júnior, Lívio Martins; Reck, José

doi:10.1590/s1984-29612024026

Cited by 3 publications

References 57 publications

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Resistance intensity test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Jongejan,

Berger,

Homminga

et al. 2024

Parasites Vectors

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Background One bioassay for detecting acaricide resistance in livestock ticks is the adult immersion test (AIT), wherein engorged ticks are briefly immersed into a solution of a particular acaricidal compound and examined for mortality, their egg-laying capacity and offspring hatchability in vitro. Usually, the recommended label dose or an established discriminating dose of an acaricide is used to determine high mortality (≥ 95%) of susceptible tick strains. Such a test intends to detect the presence of resistance in a tick population. However, the adult immersion test does not directly translate the bioassay results to the predicted efficacy in the field. In this paper, we used the AIT as an initial screening bioassay supplemented with the resistance intensity test (RIT), a novel larval-based bioassay, wherein the resistance level can be determined and translated to the expected field efficacy. This was done by adopting World Health Organisation (WHO) guidelines for resistance detection in mosquitoes, which combines a 1 × recommended dose with 5 × and 10 × concentrated doses to reveal low, moderate and high resistance intensity, respectively. Methods Engorged Rhipicephalus microplus ticks were collected from cattle at six different ranches across Rio Grande do Sul, Brazil, as part of the state’s acaricide resistance surveillance program. Groups of adult ticks from each field collection were subjected to the AIT from each field sample. Additionally, engorged female ticks from each ranch were allowed to lay eggs, and their larval progeny aged 14 to 28 days were then used in the RIT. Deltamethrin and a combination of cypermethrin, chlorpyrifos and piperonyl butoxide were used in both tests, and the results were statistically analysed. Results The in vitro efficacy of deltamethrin against adult ticks in the AIT ranged between 8.74% and 25.38%. The corresponding RIT results on their larval progeny indicated a high resistance level. In the immersion test, the in vitro efficacy of the combination of cypermethrin, chlorpyrifos, and piperonyl butoxide against adult ticks ranged between 49.31% and 100%. The corresponding RIT results on their larval progeny indicated a similar response ranging from fully susceptible to low or moderate resistance. The Pearson correlation coefficient (r = 0.883) showed a high correlation between tick mortality at the 1 × recommended concentrations of acaricides in both tests. Conclusions The resistance intensity test is a valuable addition to the range of bioassays currently available for detecting acaricide resistance by determining the level of acaricide resistance. This is relevant to whether or not to continue using a particular acaricidal class for controlling cattle ticks. Graphical Abstract

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Resistance intensity test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Jongejan,

Berger,

Homminga

et al. 2024

Parasites Vectors

View full text Add to dashboard Cite

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Resistance Intensity Test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Jongejan,

Berger,

Homminga

et al. 2024

Preprint

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Background One bioassay for detecting acaricide resistance in livestock ticks is the Adult Immersion Test (AIT), wherein engorged ticks are briefly immersed into a solution of a particular acaricidal compound and examined for their egg-laying capacity and offspring hatchability in vitro. Usually, the recommended label dose or an established discriminating dose of an acaricide is used to determine high mortality (≥ 95%) of susceptible tick strains. Such a test intends to detect the presence of resistance in a tick population. However, the adult immersion test does not directly translate the bioassay results to the predicted efficacy in the field. In this paper, we used the AIT as an initial screening bioassay supplemented with the Resistance Intensity Test (RIT), a novel larval-based bioassay, wherein the resistance level can be determined and translated to the expected field efficacy. This was done by adopting WHO guidelines for resistance detection in mosquitoes, which combines a 1x recommended dose with 5x and 10x concentrated doses to reveal low, moderate, and high resistance intensity, respectively. Methods Engorged Rhipicephalus microplus ticks were collected from cattle at six different ranches across Rio Grande do Sul, Brazil, as part of the state's acaricide resistance surveillance program. Groups of adult ticks from each field collection were subjected to the AIT from each field sample. Additionally, engorged female ticks from each ranch were allowed to lay eggs, and their larval progeny aged 14 to 28 days were then used in the RIT. Deltamethrin and a combination of cypermethrin and chlorpyrifos were used in both tests, and the results were statistically analysed. Results The in vitro efficacy of deltamethrin against adult ticks in the AIT ranged between 8.74% and 25.38%. The corresponding RIT results on their larval progeny indicated a high resistance level. The in vitro efficacy of the combination of cypermethrin and chlorpyrifos against adult ticks in the immersion test ranged between 49.31% and 100%. The corresponding RIT results on their larval progeny indicated a similar response ranging from fully susceptible to low or moderate resistance. The Pearson correlation coefficient (r = 0.883) showed a high correlation between tick mortality at the 1x recommended concentrations of acaricides in both tests. Conclusions The Resistance Intensity Test is a valuable addition to the range of bioassays currently available for detecting acaricide resistance by determining the level of acaricide resistance that is relevant to whether or not to continue using a particular acaricidal class for controlling cattle ticks.

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Role of Tick Commensal Bacteria in the Propagation of Emerging Infectious Diseases: Data Gaps and One Health Implications

Turaga,

Presley

2024

Zoonotic Diseases

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Ticks are obligate hematophagous ectoparasites notorious for their role as vectors of pathogens that affect humans and animals, particularly relative to the propagation of emerging infectious diseases (EIDs). Two important factors facilitating the role of ticks in the propagation of EIDs are their potential for the development of resistance to acaricides and the expansion of nonindigenous tick species into new geographic regions. The acquisition of acaricide resistance enables tick populations to be less susceptible to vector control programs. Expansion of the geographic distribution of tick populations increases the likelihood of access to new host species as well as new pathogens. Understanding of the microbiome of ticks continues to evolve, providing critical insights into tick biology. The tick microbiome largely comprises endosymbionts, pathogenic organisms, and commensal bacteria. Endosymbionts are highly preserved and vertically transmitted in ticks from mother to offspring, and their role in the survival of ticks is well recognized. Similarly, the role of ticks as vectors of pathogens is well established. However, commensal bacteria in ticks are acquired from the environment and while ingesting a blood meal. Because many tick species spend most of their lifetime off the hosts, it can be assumed that the richness and diversity of commensal bacteria are highly variable and dependent on the ecosystem in which the tick exists. This mini-review identifies some of the critical data gaps relevant to the role of and influence of commensal bacteria on the vectorial capacity of ticks. As ticks move into new habitats, are locally acquired commensal bacteria playing a role in adaptation to the new habitat? Apart from the conventionally understood mechanisms of acaricide resistance in ticks, are the commensal bacteria influencing the development of acaricide resistance at the population level?

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Brazil's battle against Rhipicephalus (Boophilus) microplus ticks: current strategies and future directions

Cited by 3 publications

References 57 publications

Resistance intensity test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Resistance intensity test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Resistance Intensity Test (RIT): a novel bioassay for quantifying the level of acaricide resistance in Rhipicephalus microplus ticks

Role of Tick Commensal Bacteria in the Propagation of Emerging Infectious Diseases: Data Gaps and One Health Implications

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