Mosquitoes: “convulsions and death,” etcetera

--Cartoon courtesy of The Haggin Museum

As mentioned in today’s column, the state proposes to flood 100,000 acres of Delta land for habitat restoration as mitigation for the tunnels project. Unfortunately, when the state restores habitat for fish, it also will restore habitat for Stockton’s historic scourge, mosquitoes.

Here’s the state’s take on the mosquito-breeding effects of its plan.

“The optimal conditions for mosquitoes to carry out their complete growth and reproduction cycles can be found in areas of standing water with non-stagnant pond surface water, such as ponds subject to daily tide flushes or wind-driven wave action” …

A.k.a. a swamp. ”Suitable mosquito breeding habitat is in close proximity to urban areas along the Sacramento River and the south Delta (that would be us); therefore, the current urban population is already exposed to vector-borne diseases …”

What diseases? The report lists them.


Malaria is a mosquito-borne disease caused by a single-celled parasite, Plasmodium (Reiter 2001). This parasite infects and destroys the red blood cells of its host. The disease is usually transmitted through the bite of an infected mosquito; a mosquito becomes infected from feeding on people carrying malaria in the blood (Zucker 1996). Malaria occurs in tropical and subtropical areas with high humidity and temperatures, including Africa and Central and South America. Although no longer considered an endemic disease in California, malaria cases continue to be reported in the United States (CalSurv 2012). In the United States there are approximately 1,200 diagnosed cases 8 each year (Marin/Sonoma Mosquito and Vector Control District 2009). In California, the primary 9 vectors of this disease are female western malaria mosquitoes.


Encephalitis is a virus with symptoms characterized by swelling or inflammation of the brain and spinal cord. Mosquito-borne encephalitis is directly transmitted to humans by mosquitoes and maintained through the contact between virus-carrying birds and mosquitoes. It is most commonly found in California as a consequence of the WNV, SLE virus, and WEE virus. Horses and birds are usually the most important carriers and also the most vulnerable and susceptible to these viruses (California Department of Public Health 2010a, 2010b).

West Nile Virus

WNV is a mosquito-borne virus introduced to North America in 1999 (San Joaquin County Mosquito and Vector Control District 2009). The Culex mosquito genus has been identified as the primary transmitting vector of the virus (Goodard et al. 2002). The majority of victims of this virus develop very few or no symptoms. Some of the common symptoms identified are fever, nausea, body aches, headache, and mild skin rash. A very small proportion (less than 1%) of victims may also develop brain inflammation (encephalitis), which could lead to partial paralysis and death (Marin/Sonoma 24 Mosquito and Vector Control District 2009).

St. Louis Encephalitis

 SLE is distributed throughout California and generally affects non-human mammals, principally horses. The western encephalitis and house mosquitoes are the main transmitting vectors (CalSurv 28 2012). The main sources of infection for mosquitoes are birds; once infected, the mosquito can transmit the virus to other animals and, on few occasions, humans. Symptoms tend to be very mild and usually include fever, headache, and dizziness. However, the disease may also lead to convulsions and death, and carries a fatality rate that ranges from 3–30% (Contra Costa Mosquito and Vector Control District 2011; CalSurv 2012). From 1964 through 2009, an average of 102 cases were reported annually in the United States. From 1964 through 2010, 123 cases of SLE were reported in California (Centers for Disease Control and Prevention 2011).

Western Equine Encephalitis

Seasonal viral activity is at its highest for WEE from late spring to early summer, especially in areas with highly irrigated agriculture and stream drainages. The disease has a fatality rate of 33% and affects young children most severely (Marin/Sonoma Mosquito and Vector Control District 2009). The western encephalitis mosquitoes are generally identified as primary transmitters. In California, the pale marsh mosquito is also a major vector. Symptoms range from mild flu-like illness to encephalitis, which could lead victims into a coma and death (Napa County Mosquito Abatement District 2006). Between 1964 and 2005, 639 cases of WEE were reported in the United States (Centers for Disease Control 2005).





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    Michael Fitzgerald

    Mike Fitzgerald is The Record’s award-winning metro columnist. His column runs in the paper three times a week. Born in San Francisco, he was raised in Stockton. His column covers diverse beats including, sometimes, the offbeat. Read Full
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