By mid-September the United States was pushing close to 3,000 cases of West Nile and over 120 deaths, at least 50 of those in Texas. West Nile is a virus that pops up every year in the U.S. as it is endemic to our region. This year, weather conditions (and possible other environmental and nonenvironmental conditions) have increased mosquito populations and transmission of the disease. Now, drought doesn’t exactly make one think that mosquitoes will rise, but when we are in a drought and experience a good rainfall, both mosquitoes and birds go to those pools of water. Birds are the reservoir for the West Nile virus. They hold the virus in their bodies in high numbers but do not exhibit symptoms of the virus, and thus continue to live and keep it in the population. Birds carrying West Nile are bitten by a mosquito while both are a water source, and when we have fewer water sources because of a drought, the two key players in the West Nile saga have a better chance of meeting.
The Center for Disease Control (CDC) estimates that 1 in 150 people who contract West Nile will show symptoms. Most of us have no idea! Those few people that come down with symptoms usually have the mild symptoms (thank goodness) – fever, aches, headache, swollen lymph nodes, rash. Very few people will experience severe symptoms: severe headache, neck ache, muscle weakness, vision loss, paralysis, disorientation, and coma.
There is not treatment or cure for West Nile (only treatment of the symptoms), so the best thing is prevention! Avoiding mosquitoes when they are most active, during dawn and dusk is a great idea. If you have to be outdoors, wear light colored, loose fitting, long sleeves and pants, and wear mosquito repellent. The Environmental Protection Agency recognizes four active ingredients as being approved, labeled insect repellents that provide relatively long lasting repellency to disease carrying mosquitoes. Those active ingredients are DEET, Picaridin, Oil of Lemon Eucalyptus* or PMD, and IR3535. For more information on this, visit www.cdc.gov or www.epa.gov.
As a homeowner, treating all the areas around your home for adult mosquitoes isn’t really the best option. It is generally short term and you will never totally eliminate all the mosquitoes. We end up applying too much pesticide, exposing ourselves and the environment, and spending a lot of money. It is much better to go to the source and prevent the mosquitoes from becoming adults. Mosquitoes require standing water to lay their eggs and complete the larva and pupa stages of their life cycle. Water that is still, stagnant, high in organic matter or debris, and generally dirty is a great breeding ground for mosquitoes. Look around your yard for breeding sites: animal water dishes, potted plants, saucers under pots, trash can lids, kiddie pools, bird baths, water running off a gutter, A/C condensation dripping, ponds, low laying areas, etc. are all potential mosquito breeding sites.
Dump the water if you can, and dump it every couple of days. Mosquitoes can complete their lifecycle in 6 days during high temperatures, so a weekly look around the yard is too long! If you cannot dump the water, use Bti mosquito dunks or granules. Bti (Bacillus thuringiensis israelensis) is a bacteria that ONLY effects mosquitoes. You can safely apply it to bird baths, horse troughs, fish ponds and know only the mosquitoes will be effected – no other animal or insect.
Recent, long, soaking rains have increased water pools that will allow more mosquitoes to breed. Cooler weather may slow down their development, but they will be active well into the fall and I anticipate the cases of West Nile will continue to increase until the weather dips into 60s and 50s. Protect yourself by using insect repellent and remember next spring and summer we will likely face the same issues.
For more information about West Nile, visit the CDC’s website: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm or Texas A&M AgriLife’s Bookstore and use the keyword mosquito: http://agrilifebookstore.org
by Molly Keck
Integrated Pest Management Program Specialist