April's Ag Advice by April Borders We have heard it on the radio, you have heard it in the news and I know that you have read it in the paper. But I feel that we should revisit this subject again. It is the West Nile Virus (WNV). I know that you are probably tired of hearing about it or maybe you don't think that it is important but it is. You might even think that it is too cool for the mosquitoes but they are here too. So we want you to be prepared.
One of the species of mosquitoes that carries the WNV actually overwinters in South Dakota as an adult. So as soon as the temperatures exceeded 40 degrees this mosquito became active. So they are alive and ready to begin feeding. There are also 20 other species of mosquitoes in the state that are potential vectors of the West Nile Virus.
It seems rather early for these insects to be out but believe me they are here. We are also starting to pick up reports from surrounding states of animals that have tested positive for the WNV already this year. In Canada, a crow that was found dead tested positive for WNV. The crow's death comes almost a month earlier than the first avian case of last year.
Recently Minnesota reported the first equine WNV case of the season. The pregnant Quarter Horse mare was euthanized five days after the onset of symptoms. This horse had received a single shot of the vaccine in May 2003 but had not received the recommended booster. This showed up nearly two months before it was expected. Many horse owners have yet to give the vaccinations and booster shots.
The most recent case reported was also in a horse located in Fargo, ND. This case raises concerns since the majority of West Nile Virus cases usually appear from July through September. This serves as a reminder that the virus is here and we all need to take precautions.
People with horses should be vaccinating them now or giving them their booster shot. For initial immunization of adult horses, two vaccinations three to six weeks apart are needed to "prime" the immune system. The maximum immune response is not obtained until three weeks following the second vaccination. That means a total of six weeks is required from the time of first vaccination until the horse is considered immunized. Don't underestimate the time it will take to bring your horse to full protection.
Following the initial series, it is currently recommended that horses be boostered at least annually (in spring to summer). In areas with a prolonged mosquito season, horses should be boostered every four to six months during the mosquito season. In South Dakota, if horses receive the annual booster in April/May, protection should be sufficient until September/October, which is at the end of the mosquito season.
People need to take precautions too. Limit outdoor activities between dusk and dawn when mosquitoes are most likely to bite. When possible, wear long pants and long-sleeved shirts when outside. Eliminate stagnant water in containers around homes where mosquitoes can lay their eggs (e.g., buckets, flowerpots, old tires, wading pools, and birdbaths). Keep mosquitoes from entering your home by repairing screens in windows and doors. Also keep the grass around your house trimmed.
You can also protect yourself by using insect repellent that contains DEET and is approved by the Environmental Protection Agency. Make sure that you read all instructions carefully. Our office has a list of all personal mosquito repellents available in South Dakota that contain DEET. It also lists the percentage of DEET contained in the product.
West Nile virus is a mosquito-borne infection that can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). Most people infected with the disease will experience no symptoms or have only mild symptoms such as fever and headaches. More severe infections can include high fever, severe headaches, stiff neck, altered mental state and death. Although the very young and the elderly are more likely to have severe infections, anyone who develops symptoms should consult a physician.
Last year, Clay County had seven horses and four birds that were confirmed positive for WNV. No human cases were reported in Clay County.
For more information on the West Nile virus and how to protect yourselves or your animal, please contact the Extension Office at 677-7111.