Assessment of insecticide resistance of Aedes aegypti (Diptera: Culicidae) populations to insect growth regulator pyriproxyfen, in the northeast region of Brazil

Detection of arboviruses in Aedes aegypti through transovarian analysis: A study in Goiânia, Goiás

BACKGROUND

Arboviral diseases are a group of infectious diseases caused by viruses transmitted by arthropods, mainly mosquitoes. These diseases, such as those caused by the dengue (DENV), Zika (ZIKV), chikungunya (CHIKV), and yellow fever (YFV) viruses, have a significant impact worldwide. In this context, entomological surveillance plays a crucial role in the control and prevention of arboviruses by providing essential information on the presence, distribution, and activity of vector mosquitoes. Based on entomological surveillance, transovarian transmission provides information regarding the maintenance and dissemination of arboviruses. The objective of this study was to detect these arboviruses in Goiânia, Goiás, and analyze the occurrence of transovarian transmission.

METHODS

Aedes aegypti eggs were collected from different regions of Goiânia and cultivated under controlled laboratory conditions until the emergence of adult mosquitoes. Adult females were grouped into pools containing their heads and thoraxes. These pools were subsequently evaluated using reverse-transcription quantitative polymerase chain reaction (RT-qPCR) assay.

RESULTS

A total of 157 pools (N=1570) were analyzed, with two pools testing positive for CHIKV and one pool testing positive for ZIKV, indicating that the offspring resulting from transovarian transmission are potentially infectious.

CONCLUSIONS

In summary, the demonstration of the vertical transmission mechanisms of CHIKV and ZIKV in A. aegypti serves as an alert to health authorities, as these diseases are still underreported, and their primary urban vector has likely acquired this capacity, contributing to the dissemination of these infections.

Regionality in vector control: effect of fluctuating temperature in the susceptibility of Aedes aegypti (Diptera: Culicidae) larvae to Pyriproxyfen

Using Pyriproxyfen in controlling Aedes aegypti shows great potential considering its high competence in low dosages. As an endocrine disruptor, temperature can interfere with its efficiency, related to a decrease in larval emergence inhibition in hotter environments. However, previous studies have been performed at constant temperatures in the laboratory, which may not precisely reflect the environmental conditions in the field. The aim of this study was to assess the effect of the fluctuating temperatures in Pyriproxyfen efficiency on controlling Aedes aegypti larvae. We selected maximum and minimum temperatures from the Brazilian Meteorological Institute database from September to April for cities grouped by five regions. Five fluctuating temperatures (17-26; 20-28.5; 23-32.5; 23-30.5; 19.5-31 °C) were applied to bioassays assessing Pyriproxyfen efficiency in preventing adult emergence in Aedes aegypti larvae in five concentrations. In the lowest temperatures, the most diluted Pyriproxyfen treatment (0.0025 mg/L) was efficient in preventing the emergence of almost thrice the larvae than in the hottest temperatures (61% and 21%, respectively, p value = 0.00015). The concentration that inhibits the emergence of 50% of the population was lower than that preconized by the World Health Organization (0.01 mg/L) in all treatments, except for the hottest temperatures, for which we estimated 0.010 mg/L. We concluded that fluctuating temperatures in laboratory bioassays can provide a more realistic result to integrate the strategies in vector surveillance. For a country with continental proportions such as Brazil, considering regionalities is crucial to the rational use of insecticides.