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United States Department of Agriculture

Agricultural Research Service


Location: Mosquito and Fly Research Unit

Title: Blood Meal Analysis of and Virus Detection in Mosquitoes Collected during a Rift Valley fever Epizootic/Epidemic: Implications for epidemic disease transmission dynamics

item Lutomiah, J -
item Omondi, D -
item Masiga, D -
item Mutai, C -
item Mireji, P -
item Ongus, J -
item Linthicum, Kenneth
item Sang, R -

Submitted to: Vector-Borne and Zoonotic Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 5, 2014
Publication Date: N/A

Interpretive Summary: Mosquitoes were collected in 2 locations in Kenya during a Rift Valley fever virus outbreak in domestic animals and people. Using molecular biology techniques the mosquitoes which had recently fed were analyzed and the source of the blood meals determined. In eastern Kenya Aedes species mosquitoes fed predominantly on goats, followed by cattle, donkeys, sheep and humans. In west-central Kenya Mansonia species mosquitoes fed predominantly on sheep, followed by frogs, duikers, cattle and goats. Rift Valley fever virus was found in some Aedes and Mansonia species mosquitoes that had fed on cattle and sheep.

Technical Abstract: Rift Valley fever (RVF) is a zoonosis of domestic ruminants in Africa. Bloodfed mosquitoes collected during the 2006-2007 RVF outbreak in Kenya were analyzed to determine the virus infection status and animal source of the bloodmeals. Bloodmeals from individual mosquito abdomens were screened for viruses using Vero cells and RT-PCR. DNA was also extracted and the cytochrome c oxidase 1 (CO1) and cytochrome b (cytb) genes amplified by PCR. Purified amplicons were sequenced and queried in GenBank and Barcode of Life Database (BOLD) to identify the putative bloodmeal sources. The predominant species in Garissa were Ae. ochraceus, (n=561, 76%) and Ae. mcintoshi, (n=176, 24%), and Ma. uniformis, (n=24, 72.7%) in Baringo. Ae. ochraceus fed on goats (37.6%), cattle (16.4%), donkeys (10.7%), sheep (5.9%) and humans (5.3%). Ae. mcintoshi fed on the same animals in almost equal proportions. RVFV was isolated from Ae. ochraceus that had fed on sheep (4), goats (3), human (1), cattle (1) and unidentified host (1); with infection and dissemination rates of 1.8% (10/561) and 50% (5/10) respectively; and 0.56% (1/176) and 100% (1/1) in Ae. mcintoshi. In Baringo, Ma. uniformis fed on sheep (38%), frogs (13%), duikers (8%), cattle (4%), goats (4%) and unidentified hosts (29%); with infection and dissemination rates of 25% (6/24) and 83.3% (5/6) respectively. Ndumu virus (NDUV) was also isolated from Ae. ochraceus with infection and dissemination rates of 2.3% (13/561) and 76.9% (10/13); and Ae. mcintoshi, 2.8% (5/176) and 80% (4/5) respectively. Ten of the infected Ae. ochraceus had fed on goats, sheep (1) and unidentified hosts (2), and Ae. mcintoshi on goats (3), camel (1) and donkey (1). This study has demonstrated that RVFV and NDUV were concurrently circulating during the outbreak, and sheep and goats were the main amplifiers of these viruses respectively.

Last Modified: 9/21/2014
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