#02-091

Complete

Date Full Report Received

05/08/2003

Date Abstract Report Received

07/24/2006

Investigation

Institution:
Primary Investigator:

This information is important because it would help swine practitioners to understand the potential role of mosquitoes in transmission of PRRSV. It has been documented that mosquitoes can travel for the distances of 2.5 to 10 km and can collect blood meals multiple times in their life. Furthermore, mosquitoes frequently inhabit the interior of transport vehicles and livestock trailers, enhancing contact with pigs that are potentially infected with PRRSV, and allowing them to travel over greater distances during shorter period of time. All this information, along with previous evidence of the ability of mosquitoes to mechanically transmit PRRSV from infected to naïve pigs under experimental conditions, suggests that while mosquitoes may play a role in area spread of PRRSV during warm whether, they serve strictly as mechanical vectors and not as biological vectors. Their inability to serve as biological vectors may limit the significance of the mosquitoes in transmission of PRRSV; however, further studies such as on-farm investigations and large scaled epidemiological studies are needed to make a final conclusion regarding the significance of mosquitoes throughout commercial swine producing areas. Mosquitoes used in the study were identified for their genus and species, and the majority (95.6%) of the insect population was Aedes vexans. It has been reported that Aedes vexans is generally distributed over the whole North America including Canada, United States, and Mexico. However, this species is specially abundant in Midwest areas in United States, and is a majority of wild mosquito populations observed in Minnesota (R Moon; personal communication 2002). Therefore, we believe that insect population used in the study was reliable to represent the wild mosquito population in Midwest areas in United States.
In conclusion, PRRSV can survive within the intestinal tract of mosquitoes for up to 6 hours following feeding on an infected pig; however, the infectious PRRSV is restricted to the intestinal tract and does not replicate or disseminate systemically within mosquitoes during a 14-day incubation period. This study suggests that while mechanical transmission of PRRSV by mosquitoes is possible, mosquitoes (Aedes vexans) are not likely to serve as biological vectors of PRRSV.