Malaria - Manager's Note 7-13-23


Human malaria is caused by one of four species of microscopic parasites: Plasmodium falciparum, P. vivax, P. malariae, and P. ovale. The name malaria originates from the Italian word “bad air,” reflecting the association of the disease with damp breezes from marshes. People get malaria through the bite of a malaria-infected mosquito. [Durso, 1996]

The different malaria parasite species can be recognized in human blood by their size, shape, and staining characteristics and clinically by the severity of the infection and the pattern of fever and chills. The most severe form of the disease is caused by P. falciparum which can cause kidney failure, brain damage, severe anemia, and death. However, this species lacks residual stages and does not relapse. P. vivax causes a more common and less severe form of the disease. However, this species characteristically has a residual liver stage that may cause relapse for several years after the infection if untreated. The remaining two species, P. malariae and P. ovale, are limited in global distribution and cause comparatively less illness in humans. [Durso, 1996]

Malaria parasites spend most of their life cycle within humans’ liver or blood cells but require Anopheline mosquitoes for sexual reproduction and biological transmission. Malaria parasites can also be transmitted mechanically by contaminated blood products or hypodermic needles. [Durso, 1996]

Malaria (mostly P. vivax) was introduced into and became established in the Central Valley of California during the 1800s. Many older mosquito control districts were initially formed to combat this disease through Anopheles mosquito control [Durso, 1996]. As stated in an article by the Lodi News Sentinel, September 7, 2007, “The first effort to combat mosquitoes was during the Great Depression of the 1930s. In the mid-to-late 1930s, Civilian Conservation Corps workers in Lodi cleared brush alongside ditches and the banks of the Mokelumne River to cut down on mosquito breeding areas.”

The article also said, “World War II changed our local war on mosquitoes. Concern and public awareness of malaria heightened during the war as troops were sent to tropical areas of the world. Also, the war pushed technology to improve so that an effective program to fight mosquitoes was possible.”

Because malaria involves only the human population, control in California continues to focus on promptly diagnosing and treating imported relapsing cases. Epidemiological information concerning recent and past travel is critical in determining if the infection was acquired locally. [Durso, 1996]

Although there are three species of the Anopheles mosquito in San Joaquin County, the Anopheles freeborni is the most commonly found. The District monitors this species population through surveillance provided by our laboratory personnel. Known habitat locations where Anopheles mosquitoes develop are monitored and treated by the District’s certified technicians. For San Joaquin County, contracting malaria through the bite of an infected mosquito is very unlikely.
Durso, S. (1996) The Biology and Control of Mosquitoes in California. (p.45-46)

 CDPH Malaria information in California

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