What is a Vector?

Mosquito on hand

According to the California State Health and Safety Code, Section 2002(K): “Vector” means any animal capable of producing discomfort or injury, including, but not limited to, mosquitoes, flies, other insects, ticks, mites, and rats but not including any domestic animals.

Vectors can transmit infectious organisms that cause human and animal disease. These diseases can be serious and sometimes fatal. In San Joaquin County, certain mosquito species are capable of transmitting western equine encephalomyelitis (WEE), Saint Louis Encephalitis (SLE), and most recently West Nile virus (WNV). Other mosquito species have the potential to carry malaria and dog heartworm. Ticks in California can carry a variety of pathogens, including Rocky Mountain spotted fever, ehrlichiosis, babesiosis, and Lyme.

There are 17 species of mosquitoes found in San Joaquin County. Regardless of the number, there are several species that are of public health concern; Culex tarsalis, is the vector of western equine encephalitis and West Nile virus, Culex pipiens, is the vector of West Nile virus, Anopheles freeborni, the vector of malaria, Aedes Melanimon, is the vector of West Nile Virus, and Aedes Sierriensis, currently the vector of dog heartworm. Canine Heartworm Study PDF

Additional Heartworm Information:

Among the many diseases that mosquitoes can carry, WNV is of most concern in San Joaquin County. West Nile virus was first recognized in San Joaquin County in 2004 with early indications in 2005. Epidemic levels were reached in 2005, 2006 and 2007, 2008 & 2012. West Nile virus activity continues to be prominent and is now considered endemic in San Joaquin County.

Other Vectors / Pests of Homes, Structures, People and Pests:

The District provides identification and information of other vectors and pests, however the District does not provide control for these organisms. For control of everything else other than mosquitoes, a private pest control company would need to be contacted. The University of California Agriculture & Natural Resources has comprehensive information for the following: "Pests of Homes, Structures, People and Pets."


West Nile Virus and
Dead Bird Hotline

(877) 968-BIRD (2473)

or online at westnile.ca.gov


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