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Poultry and Livestock |
The West Nile virus story is heating up here in North Carolina. People are worried. That's understandable and wise. Lately, there have been questions about the risk of West Nile virus to animals, and about dealing with potential mosquito breeding sites (watering troughs and buckets) in pastures and around barns, stables or dog pens. Here's some information that should answer many of those questions.
What about animals? Horses, of course, are susceptible to West Nile virus. They have a mortality rate of between 30 and 40 percent (death or euthanasia). The good news is that horses can be vaccinated against the disease. It's encouraging to know that more than 62,000 doses of the vaccine have been sold to North Carolina veterinarians this year. The bad news is that, if you haven't gotten your horses vaccinated, it may be too late. Two injections, 3 to 6 weeks apart, are required, and immunity may take up to 6 weeks to develop. The best one could hope for now would be protection for their horse during the last half of this year's West Nile Virus season.
Most other domestic animals appear to be safe from the disease. Dogs, cats and other animals may become infected, but there's no evidence that they become clinically ill. The lack of illness also means that they are not likely to be reservoirs for the disease. Most animals tend to build antibody levels quickly, and don't develop high levels of the virus in their bloodstream. The same is true for chickens and turkeys. More exotic birds may be at risk, however, as suggested by the loss of some exotic birds in captivity during the 1999 outbreak.
What about mosquito breeding in troughs and buckets used to water livestock or pets? There are two things to consider. First, most mosquito species implicated as possible West Nile Virus vectors aren't likely to be present in large numbers if the water in such containers is consumed or changed frequently. On the other hand, water that is left around in troughs and buckets to go stagnant will become a mosquito breeding ground. The lesson here is to give animals fresh water, and dump or drain watering containers that are used infrequently. Because of this year's drought, use the discarded water for plants if practical. If it is impossible to replace water or empty unused watering containers, the useful life of the water can be extended provided it is not heavily contaminated with organic matter. Shock chlorination is a method used to decontaminate wells, and can temporarily suppress mosquitoes in trough water. Mix in 1/2 fluid ounce of Clorox per gallon of water. This will add enough chlorine (about 200 parts per million) to kill bacteria and algae. The chlorine will dissipate in 12 to 24 hours, leaving relatively fresh water that's less attractive to mosquitoes. Animals may refuse the water until the chlorine dissipates, but a temporary water source can be provided.
The second consideration about mosquito control in water troughs is that there's no larvicide you can add to a watering device to control mosquito larvae. There are products out there that are perfectly safe, but the labels do not expressly say they can be used in water consumed by animals. Consequently, they cannot be legally used until the labeling is changed by the manufacturer.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on August 26, 2002 by Stephen J. Toth, Jr.