Some species of mosquitoes found in the San Gabriel Valley are involved in the transmission of important human diseases such as malaria, St. Louis encephalitis (SLE), Western equine encephalomyelitis (WEE) and other encephalitis viruses. Additionally, secondary infections can occur from scratching mosquito bites, and some people can exhibit a significant allergic reaction to the bite itself. Several of our local mosquito species are also capable of transmitting Dirofilaria immitis, the causative agent of the often fatal canine heartworm.
Mosquito-transmitted disease such as malaria, yellow fever, dengue, and encephalitis are responsible for more deaths annually than any other cause worldwide. In southern California, St. Louis Encephalitis (SLE) and Western equine encephalomyelitis (WEE) are currently of greatest concern. However, increased international travel routinely creates the potential for new virus or parasite introductions into the region.
Beginning in 1999, a virus never before detected in the western hemisphere became responsible for human illness and death along the United States' eastern seaboard. West Nile virus (WNV) has since caused the deaths of thousands of birds, horses, and other animals and cost taxpayers millions of dollars in mosquito control and disease prevention. The rapid spread of WNV across the United States will likely continue with its appearance expected in California within the next two years.
These diseases are transmitted through the bite of infected female mosquitoes. Encephalitis virus occurs naturally in wild bird populations and is maintained and passed from bird to bird by feeding mosquitoes. Occasionally, infected mosquitoes pass these viruses to humans or other animals. Only rarely do people actually become seriously ill, but infection in young, elderly, or immune compromised individuals having a lower tolerance to disease can prove fatal. Reducing the number of adult mosquitoes in the environment is the best and most effective approach to minimizing disease transmission.