First indications of Dog Heartworm found in O.C. mosquitoes

Garden Grove, CA. The Orange County Mosquito and Vector Control District (OCMVCD) has confirmed two mosquito species collected in 2021 tested positive for dog heartworm (Dirofilaria immitis). In 2021, the OCMVCD laboratory expanded testing capabilities to include mosquito sample screening for dog heartworm. Due to this new testing process, these are the first positive dog heartworm mosquitoes collected in Orange County. The samples were collected from the cities of Seal Beach, Fullerton, and Huntington Beach.

“The detection of positive dog heartworm mosquitoes indicates that heartworm disease is active in Orange County. Residents need to be proactive in protecting their pets from mosquito bites and prevent mosquito breeding sources,” said Amber Semrow, Director of Scientific and Technical Services.

Heartworms can only be transmitted from animal to animal by mosquitoes. When a mosquito bites an infected animal, the dog heartworm enters the mosquito’s system. The mosquito can then transmit the heartworm larvae into another animal once it feeds again.

“Heartworms are a preventable, but serious and potentially fatal parasite,” stated Monica Schmidt, Assistant Director, OC Animal Care. “As such, annual testing and prevention is key, and OC Animal Care recommends pet owners speak to their veterinarian about heartworm.” Heartworm preventative medication is a prescribed medication.

The Orange County Mosquito District staff will continue to conduct surveillance and test for diseases in mosquitoes. All residents can do their part by reducing mosquito breeding sources around their properties. Mosquitoes lay their eggs in water and develop through larval and pupal stages in the water before emerging as adults. The Aedes mosquito which, is a common backyard breeder, is a prominent vector of dog heartworm.

Checking for standing water and dumping it out at least once a week will interrupt the mosquito’s life cycle and prevent them from emerging as adults. OCMVCD provides a comprehensive backyard checklist for residents to use when looking for stagnant water sources. The checklist can be found at: https://bit.ly/MosquitoChecklist

Mosquito control is a shared responsibility. Eliminating mosquito breeding sources and taking preventive methods to protect your dogs is critical to preventing the spread of dog heartworm.

To prevent mosquito bites, take action and follow these tips:

• Dump and drain containers filled with water at least once a week
• Clean and scrub bird baths and pet water bowls weekly
• Dump water from potted plant saucers

For more information, visit www.ocvector.org.