Comparative study of hatching estimation methods of Rhipicephalus (Boophilus) microplus eggs

Area of Science:

• Veterinary Entomology
• Parasitology
• Chemical Ecology

Background:

• Reproductive parameters of Rhipicephalus (Boophilus) microplus are crucial for evaluating acaricide resistance and efficacy of plant-derived compounds.
• The Adult Immersion Test (AIT) is a standard method for assessing these parameters, but the accuracy of egg hatching assessment techniques requires scrutiny.

Purpose of the Study:

• To compare the accuracy and reliability of visual estimation versus quantification by sampling for determining egg hatching rates in Rhipicephalus (Boophilus) microplus within the AIT.

Main Methods:

• Engorged Rhipicephalus (Boophilus) microplus females were treated with plant extracts in the AIT.
• Egg hatching was assessed using two methods: visual estimation (%) and quantification by sampling (counting eggs and larvae in 100-individual samples under a stereo microscope).
• Statistical analysis was performed to compare the results from both methods and within repetitions of the sampling method.

Main Results:

• Significant differences (p≤0.05) were observed between visual estimation (56.8% hatching) and quantification by sampling (48.0% hatching), with visual estimation yielding higher rates.
• Visual estimation's overestimation is attributed to infertile eggs being concealed.
• The quantification by sampling method showed high consistency across repetitions (p=0.99, correlation=0.96), indicating that a single sample is sufficient and results are evaluator-independent.

Conclusions:

• Quantification by sampling is a more accurate and reliable method for assessing Rhipicephalus (Boophilus) microplus egg hatching rates in the AIT compared to visual estimation.
• Both methods are reliable for determining tick resistance status (95% cutoff point).
• This study provides insights for improving AIT protocols and encourages the adoption of more precise techniques for egg hatching assessment.