Evidence of transovarial transmission of Chikungunya and Dengue viruses in field-caught mosquitoes in Kenya

• Authors: Claire J. Heath, Stanford University; Elysse N. Grossi-Soyster, Stanford University; Bryson A. Ndenga, Kenya Medical Research Institute; Francis M. Mutuku, Technical University of Mombasa; Malaya K. Sahoo, Stanford University; Harun N. Ngugi, Chuka University; Joel O. Nbakaya, Kenya Medical Research Institute; Peter Siema, Vector Borne Disease Unit, Msambweni; Uriel Kitron, Emory University; Nayer Zahiri, San Mateo County Mosquito and Vector Control District; Jimmy Hortion, Stanford University; Jesse Waggoner, Emory University; Charles H. King, Case Western Reserve University; Benjamin A. Pinsky, Stanford University; A. Desiree LaBeaud, Stanford University
• Journal Title: PLoS Neglected Tropical Diseases
• Volume: Volume 14, Number 6
• Publisher: Public Library of Science | 2020-06-01, Pages e0008362-e0008362
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pntd.0008362
• Subjects: Biology, Parasitology; Health Sciences, Epidemiology; Biology, Virology; Health Sciences, Public Health
• Keywords: Science & Technology; Life Sciences & Biomedicine; Infectious Diseases; Parasitology; Tropical Medicine; Natural vertical transmission; Rift-valley fever; Trans-ovarial transmission; Aedes-aegypti larvae; Infection rates; Urban areas; Outbreak; Populations; Surveillance

Abstract

Arboviruses are among the most important emerging pathogens due to their increasing public health impact. In Kenya, continued population growth and associated urbanization are conducive to vector spread in both urban and rural environments, yet mechanisms of viral amplification in vector populations is often overlooked when assessing risks for outbreaks. Thus, the characterization of local arbovirus circulation in mosquito populations is imperative to better inform risk assessments and vector control practices. Aedes species mosquitoes were captured at varying stages of their life cycle during different seasons between January 2014 and May 2016 at four distinct sites in Kenya, and tested for chikungunya (CHIKV), dengue (DENV) and Zika (ZIKV) viruses by RT-PCR. CHIKV was detected in 45 (5.9%) and DENV in 3 (0.4%) mosquito pools. No ZIKV was detected. Significant regional variation in prevalence was observed, with greater frequency of CHIKV on the coast. DENV was detected exclusively on the coast. Both viruses were detected in immature mosquitoes of both sexes, providing evidence of transovarial transmission of these arboviruses in local mosquitoes. This phenomenon may be driving underlying viral maintenance that may largely contribute to periodic re-emergence among humans in Kenya.