Background: Numerous malaria epidemics have occurred in western Kenya, with increasing frequency over the past 20 years. A variety of hypotheses on the etiology of these epidemics have been put forth, with different implications for surveillance and control. We investigated the ecological and socioeconomic factors promoting highland malaria vectors in the dry season after the 2002 epidemic.

Aedes japonicus japonicus was introduced into the northeastern USA in 1998 and has since spread to more than 25 states. Because this species has been shown to be a competent laboratory vector of several viruses, readily feeds on large mammals, and has become a pest in several areas, there is concern that it might serve as a vector of Rift Valley fever virus (RVFV) should that virus be introduced into North America. Infection with RVFV causes mortality in > 90% of young domestic ungulates (e.g., calves, kids, and lambs), as well as causing a febrile illness and occasional deaths in humans. Therefore, we evaluated Ae. j. japonicus captured in North Carolina and in Maryland for their ability to serve as potential vectors for RVFV. After feeding on infected adult hamsters, these mosquitoes were tested for infection, dissemination, and the ability to transmit RVFV after incubation at 26 degrees C for 7-28 days. Both the Maryland and North Carolina populations of Ae. j. japonicus were highly efficient laboratory vectors of RVFV, with infection rates > 90% and dissemination rates > 84% for those mosquitoes that fed on hamsters with viremias > or = 10(8.5) plaque-forming units/ml. Thus, Ae. j. japonicus should be targeted for immediate control should RVFV be introduced into an area where this mosquito is now present.

St. Tammany Parish, Louisiana, experienced an outbreak of West Nile virus (WNV) in 2002, with 40 human cases and 4 deaths, most occurring from June to August. Culex pipiens quinquefasciatus was believed to be the primary vector of WNV during the outbreak, although circumstantial evidence suggests that Aedes albopictus also may have been involved in transmission. Dead bird reports were the 1st indication of the outbreak and were an excellent indicator of WNV activity; however, sentinel chickens were the most effective in tracking viral activity. Although sentinel chickens tested positive 2-3 wk after the 1st dead bird, they peaked at about the same time as human cases, and continued testing positive when viral activity was no longer detected in birds and mosquito pools. Lag time between the 1st positive sentinel chicken and the peak in human cases was 6 wk. If this trend continues in the future, sentinel chickens could be used to predict the peak in number of human cases. The 2002 WNV outbreak had a strong impact on operational budget of the St. Tammany Parish Mosquito Abatement District (88% increase above the 3-year average). Vector control activities accounted for most of the operational increase and consisted of targeted population reduction of known WNV-competent mosquito species. The goal of these activities was to prevent new human WNV cases. The 3- to 10-fold reduction in vector mosquito populations from May to August, together with a dramatic drop in number of new human cases by the end of August, indicated that our strategy was effective.

The presence of Aedes j. japonicus in Florida is reported for the first time. Four adult females were collected by a Mosquito Magnet® X trap baited with pressurized CO in Okaloosa County, FL, in August 2012 and later identified as Ae. japonicus in 2014. Additional adult and larval specimens were collected during 2014-17 from Bay, Leon, Okaloosa, Santa Rosa, or Walton counties, Florida. Notes are provided on the location, general habitats, and mosquito associates that may be found with Ae. japonicus in northwestern Florida. The role of Ae. japonicus in arbovirus transmission within Florida is currently unknown and should be further explored.

Mosquito insecticide resistance (IR) is a growing global issue that must be addressed to protect public health. Vector control programs (VCPs) should regularly monitor local mosquito populations for IR and plan control measures accordingly. In some cases, state/federal resources financially support this testing with expertise and/or training programs. Standardization of methods (eg, Centers for Disease Control and Prevention bottle bioassay, World Health Organization tube testing, dose-mortality bioassay) for monitoring IR must be prioritized. One solution is regional hubs of IR monitoring at the state or other level. Training programs on methodology and interpretation of results should be developed and routinely offered to local VCPs conducting IR testing in mosquitoes. Here, current methods for assessing mosquito IR are discussed and insights into a variety of questions from VCPs are considered. It is critical that methods for IR monitoring and data interpretation are standardized through routine training, with the goal of evidence-driven decision making to improve control of mosquitoes and mosquito-borne disease.