West Nile virus is a flavivirus (a genus of Japanese Encephalitis and closely related to Louis Encephalitis) commonly found in Africa, West Asia and the Middle East (it was first discovered in Uganda, Africa in 1937). It was discovered in the United States in 1999 in the New York City area and has been moving across the U.S. since.WNv is primarily a mosquito/bird disease, but incidental infections can occur with humans and many other animals.
Mosquitoes become infected when they feed on infected birds, such as ravens and crows. After an incubation period of 5 to 15 days, the mosquito can then transmit the virus to humans and animals by biting them. Following this transmission, the virus multiplies in the bloodstream. In severe cases the virus crosses the bloodbrain barrier, reaching the brain and causing inflammation of the brain tissue. This inflammation interferes with the central nervous system.
For the collection of adult female mosquitoes (male mosquitoes do not 'bite') Midway Abatement uses dry ice CO2 traps. These traps are based upon a CDC (Centers for Disease Control) designed CO2 (carbon dioxide) trap. The top portion is a 1gallon cooler with holes drilled in the bottom.
Approximately 5 lbs of dry ice is placed into the cooler and as the dry ice sublimates carbon dioxide is released. Carbon dioxide is a longrange attractant for mosquitoes. A batterypowered fan hangs beneath the dry ice cooler and as the female mosquitoes approach the CO2 source, they are sucked into a catch bag.
These traps are set out in the afternoon and then collected the following morning. The mosquitoes are then identified by species, counted, and some mosquito samples are tested for the presence of disease.
Our Inhouse testing uses the RAMP (Rapid Analyte Measurement Platform) Reader West Nile virus test. The RAMP Reader is a highly accurate device that can provide relatively quick test results on either mosquito samples or throat swabs of dead birds. The system (test cartridge) uses specific antibodies to detect the presence of WNv antigens. Positive samples may be sent off to a state accredited laboratory for confirmation. State confirmation provides a higher degree of accuracy and rules out the possibility of false positives. Though the RAMP system is not 100% accurate, it is the most reliable system available to small programs that do not have full statelab capabilities. RAMP provides quick results on field collected mosquito samples and serves as an 'early warning system' in our effort to detect WNV before it infects people, pets and/or livestock.