West Nile Virus – 2018

According to the Centers for Disease Control (CDC) as of August 7 2018, human cases of West Nile virus have been diagnosed in the neighboring states of Illinois, Indiana, Ohio, Tennessee, and Virginia,. In addition, non-human cases (birds or mosquitoes) were identified in Missouri and West Virginia. On August 31, 2018, the Department of Public Health and Wellness reported that West Nile (WNV)-infected mosquitoes were collected in traps in 3 areas of Louisville, KY. No human cases of WNV have been reported in the state as of August 5, 2018.

WNV is established in populations of several bird species in the U.S. (especially crows) and circulates from infected to uninfected birds through the bite of certain mosquito species. Studies indicate that raccoons also may serve as sources of the virus. Mosquitoes that feed on infected birds and mammals act as bridge vectors, transferring the virus to susceptible birds to mammals. Humans and equines are affected by the virus to varying degrees.

According to the CDC, most people infected with WNV do not have symptoms. Only about 1 in 5 people who are infected develop a fever and other symptoms: headache, body aches, skin rash, and swollen lymph nodes. About 1 out of 150 infected people develop a serious, sometimes fatal, illness. There are no protective vaccines available for humans.

Easy ways to reduce mosquito breeding sites

The pictures below illustrate some easy ways to reduce the number of mosquito breeding sites. In addition, you can reduce your risk of mosquito bites and WNV by using insect repellent and wearing long-sleeved shirts and long pants to prevent mosquito bites. Protect exposed skin with repellents such as DEET, Picaridin, IR 3535, Lemon eucalyptus oil, or 2-undecanone.

Figure 1. Regularly refresh water in bird baths. (Photo: Lee Townsend, UK)

Figure 2.  Fish can control mosquito larvae in standing water. (Photo: Lee Townsend, UK)

Figure 3. Standing stagnant water is a preferred breeding site for house mosquitoes, important vectors of encephalitis viruses such as West Nile Virus. Bti granules or tablets can be used to control developing larvae. (Photo: Lee Townsend, UK)

Figure 4. In urban areas, grass clippings can collect in storm drains (see Figure 5) (Photo: Lee Townsend, UK)



Figure 5.  Grass clippings that collect in storm drains provide ideal breeding grounds for “green water” mosquitoes. Avoid this by blowing clippings back onto lawns. (Photo: Lee Townsend, UK)

Figure 6. Water in buckets and rain barrels are excellent breeding sites for the Asian tiger mosquito, a fierce nuisance biter and potential virus vector (Photo: Lee Townsend, UK).


Figure 7.  Empty the water from containers and be sure overflows of rain barrels are screened. (Photo: Lee Townsend, UK)



By Lee Townsend, Extension Entomologist





Posted in Human Pests