From Vector Control (!):
The San Gabriel Valley Mosquito & Vector Control District regularly monitors mosquito populations and tests samples of mosquitoes for diseases such as West Nile virus, St. Louis encephalitis, and western equine encephalomyelitis. Mosquito traps set in April collected high numbers of Aedes sierrensis, the western treehole mosquito. This small (about ¼ inch) mosquito is the primary vector (or transmitter) of the Dirofilaria immitis, the parasite which causes heartworm disease in dogs, coyotes, and occasionally cats in the San Gabriel Valley. Although human hearts are not affected, canine heartworms can in very rare cases cause nodules to form in the lungs or under the skin if people are bitten by infected mosquitoes.
Animals may become infected when bitten by a mosquito carrying the parasite. Female mosquitoes pick up the parasite when they bite an infected animal. Heartworm has rarely been detected in Southern California. It is most often seen in dogs that have traveled to, or have been imported from, areas of the United States where heartworm is endemic. However, last year, the County of Los Angeles Veterinary Public Health & Rabies Control Program reported an apparent increase in locally acquired cases of canine heartworm in Los Angeles County. Between 2005 and 2008, 25% of all reported heartworm cases (6 of 29) were suspected of being locally acquired. In 2009 alone, 23 cases were reported and 11 (48%) were believed to have been contracted locally. Additionally, a small cluster of cases was identified from the western edge of the San Gabriel Valley.
Mosquito trapping in the San Gabriel Valley rarely detects the primary vector of heartworm (Aedes sierrenesis). In 2010 however, the San Gabriel Valley Mosquito & Vector Control District has trapped 244 western treehole mosquitoes in April alone, indicating a potential increased risk of heartworm in the region’s pet population. The District will be testing the female mosquitoes collected to see if they are carrying the parasite.
The western treehole mosquito prefers to lay eggs in water that collects in treeholes in mature oak and walnut trees but will utilize other trees or suitable sites such as abandoned tires, buckets, and small containers that fill with rainwater and contain leaves. “The increased rainfall we’ve received this year has filled up treeholes and containers allowing dormant eggs of this species to hatch” notes Kenn Fujioka, the District’s Assistant Manager. This mosquito is most active at dusk but may be active and biting in shaded areas during daylight hours. The District encourages pet owners to protect their pets from mosquito bites and consider placing their pets on heartworm preventive medications available from veterinarians.
Removing standing water from properties is key to breaking any mosquito life cycle. Check and dump water from any container after every rain. Treeholes of any size should be covered to prevent water entry or filled with sand or water absorbing gel polymers (polyacrylamide). These products provide a protective barrier against mosquitoes that lasts for years and can be found at most garden or floral suppliers. Homeowners can contact a certified arborist for specific recommendations for their trees.
West Nile virus is transmitted every year by local mosquitoes – keep yourself and your family safe!
□ Keep properties free of standing water
□ Report inoperable swimming pools to the District
□ Wear repellents and protective clothing outdoors at dusk and dawn when mosquitoes are most active
□ Report all dead birds to the WNV hotline (877) 968-2473 or at www.westnile.ca.gov
□ In Los Angeles County, all veterinarians are required to report heartworm cases to Los Angeles County Veterinary Public Health and Rabies Control at (877) 747-2243 or online at: www.publichealth.lacounty.gov/
vet/disintro.htm
For more information, visit www.sgvmosquito.org and www.publichealth.lacounty.gov/
vet/heartworm.htm
The San Gabriel Valley Mosquito & Vector Control District is a non-profit public health agency dedicated to the control of mosquito and other vector-borne diseases. The District can be reached at 626-814-9466 or on the web at www.sgvmosquito.org.
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