For many years Mississippi businesses and industries with outdoor workers have provided large water coolers or sports drinks to workers to prevent dehydration during the summer heat. Now that the potentially fatal West Nile virus has spread into the state, cans of insect repellent are also standard equipment for outdoor workers.
Most outdoors workers were being provided insect repellents even before the West Nile virus spread into the state. Forestry workers have long been advised to wear insect repellent because of diseases that can be caused by tick bites. The State Forestry Commission sends out regular bulletins about avoiding tick and mosquito bites. In the past few years there have been two cases of forestry workers diagnosed with Rocky Mountain spotted fever, a tick-borne disease. There are also occasional cases of “tick fever,” an infection caused by a bite.
At BellSouth, safety precautions against viruses such as West Nile are taught as part of the company’s health and safety training program. Every BellSouth work center is stocked with insect repellent containing DEET, and technicians carry DEET insect repellent in their work vehicles.
Another major company with a large number of outdoor workers, Entergy Mississippi, has also long provided insect repellents to outdoor workers.
“We also send written materials on the West Nile virus to employees in the field that give information on how the virus is spread and suggestion for decreasing the changes of contracting it,” says Robert Leslie, spokesman for Entergy Mississippi, the state’s largest private utility. “The Health Department advises wearing long pants and long-sleeved shirts. We also give employees information about the symptoms of the West Nile virus, and what to do if an employee believes he or she has contracted the virus.”
Entergy is also considering adding additional mosquito control devices such as insecticide foggers. However, some chemicals in insecticides react to rubber and synthetic rubber. Leslie said no new insecticides will be added before being evaluated for reaction to rubber and flammability.
“Since our crews use rubber gloves for safety, this is a matter we have to clear up before we make any changes,” Leslie said. “Every repellent we use meets health department guidelines as far as mosquitoes. We’re just looking at this to see if we can go the extra mile.”
With agriculture the leading industry in Mississippi, there is also concern about the exposure of farmers to the West Nile virus. David Waide, president of Mississippi Farm Bureau, said in addition to recommending farmers take precautions to avoid mosquito bites, it is important that farmers who get a number of bites be aware of the symptoms of West Nile virus.
“They need to be aware of the symptoms of West Nile and see a doctor as soon as they think they have been exposed,” Waide said. “A trip to the doctor is not expensive if they catch it early compared to the hospitalization cost if they fail to detect it. The odds of a person being saved without serious consequences are tremendously better the earlier it is detected.”
Symptoms include fever, headache and body aches, sometimes accompanied by skin rashes and swollen lymph glands. Most cases of West Nile encephalitis infections are mild. Older people and those with damaged immune systems are more susceptible to serious illness from the infection.
People need to be aware that while West Nile virus is a serious threat, only about one in a 100 mosquitoes carry the varies. And of the people bitten by a mosquito carrying the virus, less than one out of 150 show signs of the disease.
As the number of cases of the potentially fatal mosquito-borne illness mount, addressing mosquito control at Mississippi businesses and industries has taken on new urgency.
“There is a fair amount of concern,” said Dr. James Jarrett, entomology specialist with the Mississippi State University Extension Service. “A lot of people are calling about mosquito control and mosquito control products. Anything that you do around a business building or property that will eliminate the amount of standing water will help.”
Even with the best management it isn’t possible to achieve a 100 percent mosquito free environment in our climate, Jarrett said. Precautions such as wearing mosquito repellent andor wearing long pants and long-sleeved shirts are advised. While covering up from head to toe can be uncomfortable in the summer heat and humidity, it’s easy to sweat off mosquito repellents. Clothing provides longer lasting protection.
“Long clothing will help,” Jarrett said. “We are going to have to do some of these things as long as we have a condition where a disease like this is spreading in the mosquito population.”
Jarrett recommends businesses and industries consider a comprehensive program for the best chance of controlling the mosquitoes.
“You can still have mosquitoes come in from outside because adult mosquitoes are good flyers,” Jarrett said. “But at least don’t grow your own mosquitoes by lessening the amount of standing water and keeping vegetation low. Keeping vegetation down gives less habitat for mosquitoes. Grasses, weeds and grown up areas give adult mosquitoes a place to rest in the day.”
He also recommends cleaning banks around ponds or ornamental pools. If there are fish in the pools, in most cases the fish will control mosquito breeding. Eliminate shallow pools of water and any containers that hold water. If shallow pools of water can’t be eliminated, use a larvaecide such as Bt (Bacillus thurengiensis), making sure to purchase Bacillus thurengiensis israeliensis as other forms of Bt won’t kill mosquito larvae. Jarrett said Bt, sold under trade names such as Dipel, is a form of biological control considered safe and effective.
More information on mosquito control is available at the Mississippi State University Extension Web site, www.msucares.com
Another concern about West Nile virus is the impact on horses. While dogs and cats aren’t susceptible to the virus, it does affect horses and birds. Dr. Stanley Robertson, extension veterinarian, said there have been 14 confirmed cases of West Nile virus in horses in Mississippi as of August 6 and another five suspected cases. The 19 total cases are widespread, coming from 13 different counties in the state.
“It can be fatal in horses up to about 25 percent,” Robertson said. “A lot will show signs as mild as fever, staggering and instability. It can develop into convulsions, seizures and death.”
Other types of encephalitis are of concern, as well. There are more cases of Eastern encephalitis in horses in Mississippi than West Nile virus. Vaccinations for the different types of encephalitis are strongly recommended. The West Nile vaccine has to be given in two shots three to four weeks apart, and then it takes another six to seven weeks before it becomes effective.
The vaccinations must be repeated at least once a year, and possibly twice a year. Robertson said the vaccine has been out only a year, which isn’t long enough to know how long the vaccine is effective. Boosters are needed at least once per year, and some veterinarians believe the boosters will be needed twice per year in areas with long mosquito seasons.
“More experience is needed to see what is going to work out best,” Robertson said.
Contact MBJ contributing writer Becky Gillette at firstname.lastname@example.org or (228) 872-3457.