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CENTRAL POINT, (541) 779-6460 |
OREGON 97502 Fax (541) 826-8553 |
Several of the 45 known species of mosquitoes on Oregon can carry disease under the right conditions. When a female mosquito takes an animal blood meal, which she uses as nourishment for her developing eggs, she may transmit certain disease causing organisms to humans and other animals. These organisms are taken with blood from infected humans and other animals. The mosquito completes the cycle when she bites the next susceptible host, causing infection. The two most important diseases affecting humans are encephalitis and malaria.
There are two forms of viral encephalitis that can be transmitted by mosquitoes in Oregon, St. Louis, and Western Equine. Both are carried into an area by wild birds that are infected elsewhere. These birds show no symptoms. Infected birds are then fed on by local mosquitoes that can pass the virus on to humans through future bites. Symptoms of encephalitis range from mild flu-like illness to severe brain involvement that can cause death. Western Equine Encephalitis can affect horses and other equine animals as well as humans.
The Life Cycle of the Dog Heartworm: Infected heartworm larvae pass through the mouthparts of mosquitoes as they suck a dog's blood. The larvae burrow into the dog's skin and develop in tissue for 70 to 90 days, penetrating blood vessels and moving to the dog's heart. In five months they become adult worms in the heart and blood vessels. Females give birth to mobile embryos call microfilariae. Mosquitoes that bite the dog ingest these microfillariae, which then develop inside the mosquito and become infective larvae in 10 to 11 days. The cycle repeats when these mosquitoes bite another dog. Below is a 2001 partial map of Oregon showing the number of positive cases of canine heartworm in a few select counties.
The District maintains four sentinel chicken flocks that are located in Talent, Central Point, White City, and Sams Valley. Each flock has ten chickens that are tested every two weeks for the presence of Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), and West Nile Virus (WNV). The Oregon Public Health Laboratory in Portland, Oregon performs the tests.
The District also collects adult mosquito samples with CO2 baited light traps. The samples are brought back to the District's Lab and anesthetized, then sorted by species and sex. Pools of 50 like-specie mosquitoes each are placed in vials and tested in the District's lab for West Nile Virus. In 2007, 447 pools of mosquitoes were tested by the District using the RAMP System (Rapid Anallyte Measurement Platform) which is a rapid and reliable detection system for WNV in both mosquitoes and corvids with sensitivity and specificity approaching PCR. Of those pools tested, 2 pools were positive for WNV and confirmed at the OSU Veterinary Diagnostic Laboratory in Corvallis, Oregon.
