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SASTM Newsflash - Invasive mosquito - California, U.S.A.


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SASTM Newsflash




Madera County


The yellow fever mosquito (_Aedes aegypti_) was identified this week [week of 20 Jun 2013] in a several block area on the west side of the city of Madera. This aggressive day-biting mosquito is not native to California; however it is a common mosquito in urban areas of the southeastern United States.


The Madera County Mosquito and Vector Control District is working with the California Department of Public Health and the Madera County Department of Health to evaluate the extent of the infestation and will aggressively target problem areas to prevent its spread. "Our goal is to eradicate this population" said Leonard Irby, the District's Manager. "We definitely do not want this mosquito to become established in our communities."


The District will expand the search this week [week of 20 Jun 2013] and go door-to-door in surrounding neighborhoods to undertake control measures including education, source reduction, larval control, and local ground-based adulticiding (fogging) as necessary to target adult mosquitoes. Fogging will begin immediately in the infestation area.


Unlike our most common mosquito species in Madera, this tiny (approx. 0.25 inch) distinctive black and white mosquito is a very aggressive day-biter. While they may be active around dusk and dawn, it is their day-biting habits that are most characteristic. _Aedes aegypti_ is an efficient vector (transmitter) of dengue, yellow fever, chikungunya, and several viruses that cause encephalitis.


Residents experiencing mosquito bites during the day are urged to report them to the District. "We need the public's help on this one," urged Irby. "Anything holding even the smallest amount of water must be overturned and stored upside down. Please survey your property and discard any unneeded containers, cans, buckets, and tires, or move them into the garage. This mosquito is even known to lay eggs in water-filled holes in asphalt and concrete."


Avoid mosquito bites! Use personal protection to avoid mosquito bites. Wear long sleeve shirts, long pants, socks, and shoes when mosquitoes are most active, especially at dusk and dawn.


Apply repellents such as DEET, picaridin, oil of lemon eucalyptus, or IR3535 only to exposed skin and/or clothing (as directed on the product label). Do not use repellents under clothing. In addition to wearing repellent, you can protect yourself and your family by using mosquito netting over infant carriers, cribs, and strollers, and installing or repairing window and door screens to keep out mosquitoes.


The Madera County Mosquito & Vector Control District is a public health agency dedicated to the control of mosquito and other vector-borne diseases.


Fresno County

One day after Madera announced a yellow fever mosquito was found there, authorities announced the Mosquito Abatement District has detected the same type of mosquito in Fresno County. Authorities say no illnesses associated with this mosquito have been reported so far.


_Aedes aegypti_, yellow fever mosquito, is a small, dark mosquito with white markings and banded legs. It may be active around dusk and dawn but bites most often during the day and often bites indoors.


"The public's help is needed to eradicate this mosquito population before it can become established in our community," states Steve Mulligan, Manager of the Consolidated Mosquito Abatement District. "Residents who experience mosquito bites during the day are asked to contact the District."


Fresno County residents who live in valley communities are urged to:

- - Report mosquito bites received during the day. Also report any mosquitoes which match the description above. Call the Consolidated Mosquito Abatement District toll-free at 1-800-821-1577.

- - Apply insect repellents that contain DEET, picaridin, oil of lemon eucalyptus, or IR3535 according to label instructions.

- - Use repellent, especially in the early morning and in the evening.

- - Make sure that doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens that have holes.

- - Use mosquito netting over infant cribs, carriers, and strollers.

- - Eliminate standing water and containers that can hold water from around the home. This mosquito lays its eggs in water holding containers.

- - Get FREE mosquito fish for backyard ponds or water features from mosquito abatement


Communicated by: ProMED-mail


[These reports are not good news. The detection of _Aedes aegypti_ for the 1st time in different locations in 2 adjoining southern California counties makes one wonder if these mosquitoes are more widely distributed than just in those localities. Having this competent vector of dengue and chikungunya viruses established in the an area that would probably permit ongoing breeding because of its relatively warm temperatures year around is of serious public health concern. One hopes that the eradication efforts are successful.


This is another example of introduction of a very important mosquito that has never been in this area (California, USA) before.  Should it become established, as it has been for very many years in Florida, the risk is greater that it could transmit dengue or chikungunya viruses should they  be introduced into the area by a viremic person, just as chikungunya virus was introduced into Italy a few years ago or dengue virus into south Florida.  As in these examples, the viruses may not become endemic  in southern California because of screens and AC, and especially because of effective vector control that most areas in California have. However, the risk remains for sporadic introduction of these viruses with limited outbreaks.  These 2 areas in California where Ae aegypti has been found illustrate two important points; (1) the importance of ongoing surveillance to detect their presence very early on while they are still geographically limited, and (2) rapid response by vector control officials and the public.  Few areas in the world have developed this capability, nor even all areas in the USA.

That is why we have the Asian tiger mosquito (Ae albopictus) established in the eastern USA and southern Europe.




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The content and opinions are neither pre-screened nor endorsed by the SASTM. The content should neither be interpreted nor quoted as inherently accurate or authoritative.

The information provided in SASTM Newsflashes is collected from various news sources, health agencies and government agencies. Although the information is believed to be accurate, any express or implied warranty as to its suitability for any purpose is categorically disclaimed. In particular, this information should not be construed to serve as medical advice for any individual. The health information provided is general in nature, and may not be appropriate for all persons. Medical advice may vary because of individual differences in such factors as health risks, current medical conditions and treatment, allergies, pregnancy and breast feeding, etc. In addition, global health risks are constantly evolving and changing. International travelers should consult a qualified physician for medical advice prior to departure.

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