Founded in 1922 to control malaria, Delta Vector Control District has a long history of protecting residents from vector-borne diseases.

1880 – 1899


Carlos Finlay identifies mosquitoes as a potential vector for yellow fever transmission in Cuba. His findings are largely ridiculed by people at the time.



Ronald Ross confirms the link between mosquitoes and human malaria transmission.

Photo credit: Retrieved from the Library of Congress, https://www.loc.gov/item/93511708


Henry Rose Carter discovers the intrinsic incubation period of yellow fever which would later help confirm the link between mosquitoes and yellow fever transmission.

1900 – 1919


Jesse Lazear, a member of the U.S. Army Yellow Fever Commission, confirms the link between mosquitoes and human yellow fever transmission. He died of yellow fever shortly after.


The first recorded mosquito control efforts in California were completed, under the direction of UC Professors and were directed at the salt-marsh mosquitoes in the San Francisco Bay marshlands.


Malaria was devastating the central valley.


The first anti-malaria program in California was started in the Sacramento Valley at Penryn.


California Legislature adopted the ‘Mosquito Abatement Act’ which formed the basis for the formation, governing powers, and functions of mosquito abatement and vector control districts.

1920 – 1939


Delta Mosquito Abatement District was formed with 16 square miles, including all of the city of Visalia at the time plus some adjacent suburban area. Malaria was still a common disease and pest mosquitoes provided an added stimulus for the residents to attempt control. The Visalia Women’s club played a key part in the formation of the District. The Board held meetings downtown at a bank, and Percy Menefee was the first Superintendent. He was hired at the rate of $150/month.


The total budget for the District was set at $1,900 dollars.


The adjacent area North and West of the boundaries were added because of a need to control producers that were sending mosquitoes into the populated areas of the city.


 The District’s budget was increased by $500 to include a new car.

1940 – 1959


US Military requested the District’s help in reducing mosquito numbers at the Visalia Airport, which they were using for military purposes.


The area from Goshen to the Woodlake hills was annexed to the District. Delta MAD and Tulare MAD jointly hired an entomologist that they shared for several years. Land was purchased on Houston Avenue for $600.


1947 - February

The areas North and West of the then current District was annexed to the County line, with the border northeast following a school district boundary.

1947 - Early November

Exeter, Farmersville and Three Rivers areas were annexed into the District.

1947 - Late November

The Three Rivers area was removed from the annexation by board member vote. Aerial spraying was conducted by contracting with private agencies.


The district purchased a used TD-9 tractor for land work.


Approximately 2 1/2 miles were added to the district near the South West corner.


Annexed an area south of Visalia and West of Farmersville into the District.


An Airplane was purchased for aerial spraying.

1960 – 1979


The proposal to provide residents in the City of Lindsay coverage was forwarded and later dropped due to a lack of support.


The District changed its name from ‘Delta Mosquito Abatement District’ to ‘Delta Vector Control District’ to reflect the program, which included the control of mosquitoes, flies and other vectors.


It was proposed to annex an area West of Highway 99 which would include the Visalia Wastewater treatment plant, and an area south along Mooney Blvd to include Mooney’s Grove. This was turned down by LAFCO.


1980 – 1999


West Nile virus appeared in New York.



The first California Human West Nile virus case was reported.


The District bought its first aerial reconnaissance flights looking for neglected swimming pools, which had become a huge problem source, due to high numbers of home foreclosures. The first flights consisted of a man holding the camera out a helicopter window and taking pictures of some areas that had high numbers of mosquitoes trapped.


Commercially available foreclosed property lists were used to identify potentially empty properties with swimming pools. There was an effort to have the Lindsay-Porterville and even the Springville areas included within adjacent District boundaries. The Tulare County LAFCO rendered a decision stating that the Tulare MAD is better positioned to take care of the Lindsay-Porterville area.  The DVCD Board of Directors decided not to pursue the matter in light of economic and geographic circumstances. The boundaries have stood the same since.


High-tech aerial imaging was brought  to Delta. Contracted agencies, armed with expensive, computer controlled cameras and sensitive GPS devices, took hi-resolution images of most urban areas. The images were compared to our in-house database of tracked sources and technicians were dispatched to any newly found green pools. The City of Visalia Code Enforcement office started draining some problem pools and citing property owners. 

2010 – February

Approximately 54,000 Benefit Assessment ballots were mailed to property owners within The District, to determine the level of desire  for a local laboratory facility.

2010 – June

The Benefit Assessment passed.


Aedes albopictus mosquitoes first discovered in California.

Photo credit: CDC James Gathany 2000

2011 – July

Construction began on the new laboratory facility.

2011 – November

The ‘shell’ of the laboratory is nearly complete.


Aedes aegypti first discovered in California.


Aedes aegypti detected in a contained area in Exeter, and eliminated that same year.


The laboratory received its Name “Lourenco Laboratory”, after the retiring Biologist/Assistant Manager.


Aedes aegypti detected in Visalia, unable to be eliminated due to spread.


Murray, Wm. Donald. 1987. ‘Evolution of Mosquito Control in the Delta Vector Control District’. Proceedings and Papers of the Fifty-Fifth Annual Conference of the California Mosquito and Vector Control Association, Inc. Fresno, California. January 25-28, 1987. Published December 31, 1987.

Murray, Wm. Donald. 1966. The Delta Mosquito Abatement District as a Special District. Delta Mosquito Abatement District. Visalia, California.

Service Request? Get in Touch.


1737 West Houston Ave
Visalia, CA. 93291
Ph. 559-732-8606
TF. 877-732-8606
Fax. 559-732-7441


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