Dog or canine heartworm (Dirofilaria immitis) is endemic to the Central Valley and adjacent Sierra Nevada where it is transmitted primarily by Ae. sierrensis, a treehole breeding mosquito. This roundworm causes severe circulatory disease in dogs and coyotes, but also can cause respiratory disease in humans. Mosquitoes become infected by ingesting very small infective stages of the worm (microfilaria). In the mosquito, the worm molts twice and moves to the stylets of the proboscis where they remain until the mosquito refeeds. During blood feeding, the worms move out of the stylets and into the wound. In dogs and other canines, the worms molt to the adult stage and migrate to the large blood vessels and heart where mating and reproduction occur. Disease in dogs occurs when the number of worms becomes sufficiently large enough to impede blood flow and heart function. In humans, immature worms frequently become encapsulated in the lungs where they are detectable by chest x-ray.
San Joaquin County is home to the Aedes sierriensis, primary vector of dog heartworm.
See the study on Canine Heartworm "Prevalence of Dirofilaria immitis (Spirurida: Onchocercidae) Infection in Aedes, Culex, and Culiseta Mosquitoes From North San Joaquin Valley, CA"
or online at westnile.ca.gov
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