VECTOR COMPETENCE OF AEDES-ALBOPICTUS FROM PINE-BLUFF, ARKANSAS, FOR A ST-LOUIS ENCEPHALITIS-VIRUS STRAIN ISOLATED DURING THE 1991 EPIDEMIC

The vector competence of Aedes albopictus from Pine Bluff, AR, was ass essed for a St. Louis encephalitis (SLE) virus strain isolated during the 1991 epidemic. Aedes albopictus were fed on hamsters with viremia levels of 10(4.6)-10(4.9) Vero cell plaque-forming units (PFU)/ml. At 7 and 15 days postbloodfeeding, transmission trials were conducted usi ng individual suckling mice. Three of 313 Ae. albopictus were determin ed to be infected with SLE virus with titers of 10(6.3)-10(7.0) PFU/mo squito. At 15 days postbloodfeeding, one of 209 Ae. albopictus that re fed transmitted virus resulting in a 15-day population transmission ra te of 0.5%. The infection threshold (i.e., the amount of virus require d to infect from 1 to 5% of mosquitoes) was determined to be approxima tely 10(2.3) PFU/mosquito. Virus inoculated intracoelomically into Ae. albopictus replicated and reached mean titers above 10(6.0) PFU/mosqu ito on day 6. The combination of low susceptibility to infection and a mammalophilic bloodfeeding pattern suggests that Ae. albopictus is un likely to play a significant role in SLE transmission.