Ramping-Up Zika Virus Mosquito Surveillance--(Zika (ZIKV) Virus in Albany)

Let us examine this situation, and come to an understanding of our relative health risk from the Zika virus that is rapidly expanding in the southern hemisphere and now has arrived in the continental United States.

Two mosquitoes not native to California, Aedes aegypti and Aedes albopictus (see California distribution map and photographs) are invasive species of mosquitoes, recently detected in several parts of California, which actively feed on humans during the day, and are efficient vectors of ZIKV, as well as Dengue fever (DENV), Chikungunya (CHIKV) and Yellow fever viruses (YFV). Neither of these two species is known to be established in Alameda County, though two Aedes aegypti mosquitoes were trapped last year in Hayward. Subsequent surveillance has not detected more of these mosquitoes, and the hope is we have seen the last of them, but on-going enhanced mosquito surveillance that includes these Aedes species, is the plan for the extended future in Albany.

To date, we have 170 cases of Zika virus diagnosed in California, with 10 in Alameda County. Last year, 103 cases of Dengue virus and 178 cases of Chikungunya virus were reported in California from persons who travelled to, or arrived from areas where these diseases are all too common. There have not been any locally acquired cases of Zika virus in California, like the recent outbreak in Florida. With global travel, there will always be a risk of importing vector-borne diseases and this risk skyrockets when you have an efficient vector of the specific disease.

Your public health department receives confidential reports, investigates to make sure the facts are clear, and verifies that it is indeed a case of Dengue, Chikungunya (CHIK), Yellow Fever, Malaria, or ZIKV. The travel history is investigated, and confirmed, as well as any other potential cases in the family, or travelling party. What we want to know from the vector control side is whether the patient was viremic while residing locally, because this sets up the potential for disease transmission, but since we do not have the invasive Aedes mosquitoes, the risk is still very low.

Quite a lot is known about the transmission cycle of Dengue, Chikungunya, and Yellow Fever, but Zika is an emerging and neglected mosquito-borne disease, that still has some vague details of its ecology, and which vector species of mosquito may be of local concern. What we do know is that the invasive Aedes aegypti and Aedes albopictus mosquitoes pose a known threat in that they feed significantly on humans, and are known to have the vectorial capacity to maintain and transmit the afore mentioned diseases to people. Our local mosquito species as vectors of Zika virus, is literally, unknown, though thought to be of lesser significance as vectors, but there is planned research in the near future to verify. One study did confirm that one common mosquito, Culex pipiens, the Northern House Mosquito, is not an efficient vector of Zika virus.

Alameda County Vector Control Services District provides mosquito surveillance and control service to the City of Albany. We have biweekly adult mosquito trapping during the warmer months of the year for West Nile Virus, as well as larval mosquito surveillance of historical larval mosquito development sites. Part of this mosquito-borne disease surveillance program is the use of sentinel chickens, which are tested weekly for mosquito-borne diseases.

Our Zika and invasive Aedes mosquito surveillance includes the use autocidal gravid ovitraps (AGO) traps specifically designed to survey for invasive Aedes mosquitoes. The female mosquitoes are trapped when they seek a place to lay their eggs.

The best way the public can help is to avoid standing water in your yards, property, or businesses, and report any day-biting mosquito encounters to us at Alameda County Vector Control: 510-567-6800, or on our website www.acvcsd.org, as well as capturing and reporting any mosquito similar to the included Aedes images.

Here is a link to a great review of Insect Repellents for Aedes aegypti:

http://jinsectscience.oxfordjournals.org/content/jis/15/1/140.full.pdf