Molecular detection of dengue virus serotype-3 from wild-caught Aedes aegypti across arboviral endemic regions of Ethiopia.

BACKGROUND: Arboviral infections, especially dengue fever and chikungunya, are emerging diseases that pose a significant public health challenge in Ethiopia. These viruses are primarily transmitted by the widely spread Aedes aegypti (Ae. aegypti). Studies on arboviruses using molecular techniques are limited in Ethiopia, but it is important for informing public health decisions. This study aimed to molecularly detect dengue and chikungunya viruses in wild-caught Aedes mosquitoes across the arboviral endemic regions of Ethiopia. METHODS: Larvae and adult stage Aedes mosquitoes were collected using Pasteur pipettes, standard CDC manual mouth aspirator, and improved Prokopack aspirators from four study sites between October 2022 and June 2023. The mosquitoes were pooled by species, date of collection, and collection site into 1 mL prefilled DNA/RNA Shield tubes with bead beats. After the RNA was extracted from the mosquito homogenates, it was screened for dengue and chikungunya viruses by Real-Time PCR. Results were interpreted based on the Ct values, maximum likelihood estimation (MLE), CDC pooled methodology, and Clopper-Pearson binomial bounds to determine the dengue infection rate in the population. RESULTS: A total of 3,510 Aedes mosquitoes were collected, with the majority identified as Ae. aegypti (88%) and the remaining 12% were Ae. simpsoni complex. DENV was detected in three mosquito pools, comprising one from Dire Dawa and two from Afar. Subsequent serotyping revealed that all DENV-positive pools belonged to serotype 3 and were derived from Ae. aegypti. No positive pools for CHIKV were found. We found a low MLE in both Dire Dawa and Afar sites. CONCLUSIONS: We detected DENV-3 in Ae. aegypti from Afar and Dire Dawa before an outbreak happened. We reported low level of MLE value from both sites. The finding provides valuable information for public health decision-making. Continuous surveillance at different times is important to detect early signs of an outbreak and identify information needed for timely responses. CHIKV was not detected in the current study, and by considering the past outbreaks and regional transmission, continuous surveillance remains important. Aedes aegypti was predominantly reported from three of the study sites, whereas Ae. simpsoni complex is predominantly reported from Wolaita Sodo, and its vectorial role is uncertain. Further studies recommended to explore the screening of other arboviruses and use of advanced techniques to gain insights into the circulating arboviruses in Aedes mosquitoes in Ethiopia.