The Perspective

Vector Surveillance: Science and Art

The Southern Nevada Health District’s Vector Surveillance Program began in 2004 when West Nile virus was first detected in Clark County. Each year since, with the exception of 2010, West Nile-positive mosquitoes have been trapped in Southern Nevada. In fact, more than 150,000 mosquitoes have been trapped and sent to be tested for mosquito-borne illnesses including St. Louis Encephalitis, Western Equine Encephalitis and West Nile with about 8,000 of these testing positive for West Nile virus. In more than a decade, the Health District has confirmed 108 cases of West Nile virus and four cases of St. Louis Encephalitis.

Mosquito surveillance is used as an early warning for the introduction of new diseases into the community. Since 2014, the Health District’s Vector Surveillance program has included surveillance for the two Aedes mosquito species, which are responsible for Zika virus, as well as diseases such as chikungunya and dengue. To date, Aedes albopictus and Aedes aegypti have not been identified in Clark County.

“Vector surveillance is an opportunity to get ahead of the curve with regard to potential mosquito-borne diseases in Clark County. We can take steps to minimize the risk and provide information to people in the community so they can take steps to remove breeding sources and protect themselves and their families from mosquito bites,” said Jacqueline Reszetar, the Southern Nevada Health District’s Director of Environmental Health.

Throughout spring and summer, the six-person Vector Surveillance team identifies locations that will provide a good indication of mosquito activity in the community including flood channels, washes, golf courses, plant nurseries or residences of people who are confirmed to have West Nile virus or St. Louis Encephalitis. Traps can also be set in locations where the Health District has received complaints of mosquito activity. Traps are set and picked up 24 hours later. The mosquitoes are then sorted by sex (only females bite) and species. Mosquitoes are then ‘pooled’ together, packaged up and sent to the Nevada Department of Agriculture to be tested for disease. One pool would include no more than 50 female mosquitoes of the same species that come from the same trap.

When a submission pool is confirmed to have mosquitoes that are positive for disease, the team works with the appropriate jurisdictional agency, management staff, or community representatives on how to identify and eliminate mosquito breeding sources, as well as minimize mosquito bites. Fewer breeding sources result in fewer mosquitoes, or potential ‘disease vectors’ that can bite and spread the virus.

Between November and March, the team prepares for the spring and summer. What does this entail? Planning and projections for the upcoming season. What is expected in terms of breeding sources, surveillance resources, and necessary community outreach materials?

With the potential of new diseases like Zika, the Health District and its Vector Surveillance team has had its surveillance in place, response plans prepared and activities are ongoing as the situation evolves. Mosquito lifecycles are short, but Vector Surveillance is a year-round enterprise.

For more information about mosquito surveillance, mosquito breeding prevention, or to obtain mosquito fish, visit the Southern Nevada Health District’s Mosquito Surveillance page.

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