West Nile Virus and EEE Cases in Horses Rise from Coast to Coast; But What Do the Numbers Really Tell Us?

Author:
Publish date:
Public awareness is up. Education is up. But so are the number of cases. What do the numbers tell us about horses and mosquito-borne diseases© (State of California graphic)

Public awareness is up. Education is up. But so are the number of cases. What do the numbers tell us about horses and mosquito-borne diseases© (State of California graphic)

The news is full of announcements. No matter where you go in the USA, state health departments are announce each horse that has been diagnosed with West Nile Virus (WNV) or Eastern Equine Encephalitis (EEE).

Here in Massachusetts, we have to worry about both. Fly spray, fly sheets, horses kept in their stalls, town spraying at night--our state is waging a war on mosquitoes, and still the case numbers rise, in both humans and horses.

These diseases are technically known as arboviruses, meaning that they are spread by mosquitoes.

Is this the worst year in recent history or is the ubiquity of the web just giving us more access to more announcements?

I went to the US Government to try to find an answer. I found that you can't lump West Nile and EEE together when it comes to the number of cases reported. I think you can, however, probably lump together the population of horses that are susceptible to either or both diseases. They are the unvaccinated ones, and if a horse is unvaccinated for one disease, it is likely that is hasn't been vaccinated for the other disease, either.

Let's start with the less common disease, EEE: Alabama 7; Florida 18; Georgia 6; Louisiana 27; Massachusetts 2; Michigan 1; Mississippi 26; New Jersey 4; New York 2; North Carolina 10; South Carolina 10; Wisconsin 2. Cumulative Total Entire Country:?115.

Only 67 horses were diagnosed with EEE in 2011. Wisconsin had the highest number of cases, with 34. Louisiana only had 3. Why would EEE jump so high in Louisiana in one year?

Compare that geographic distribution and number of cases with the statistics for West Nile Virus:

When it comes to West Nile Virus, you can see that the virus has spread practically from coast to coast--although it seems to have skipped horses in Nebraska and Kansas, right in the middle!

What I found disturbing is that, once again, Louisiana has the highest number of cases, with 26. Are horse owners in Louisiana less likely to vaccinate their horses or does the state's swampy landscape put unvaccinated horses in that state at a higher risk?

But Mississippi, which was second in the EEE cases and shares the wet environment of Louisiana in its southern regions, is far behind with WNV. And WNV is found in states with relatively dry climates, even Nevada, Arizona and New Mexico.

The total number of horses diagnosed with West Nile so far this year is 187. Compare that with a total of 119 for all of 2011. We still have a month or two before a killing frost will shut down the mosquitoes.

And Louisiana didn't have any horses diagnosed with WNV in 2011, according to the service. Likewise, two horses in Connecticut have been added to the WNV list today. Connecticut, being the wealthiest state in the country, would presumably have a high likelihood of vaccinating against WNV and EEE.

It's important to note that not all horse owners obtain an official diagnosis to ascertain the cause of illness in a horse. So the actual number of cases could be quite higher.

Does the fact that many horseowners are struggling financially influence their decision whether or not to vaccinate their horses? And if an owner's unvaccinated horse becomes ill, will the veterinarian be called?

There's no doubt that these viruses are changing, but horse owners' actions--or lack of actions--may be influencing the increase in cases as well. We have a lot to learn, and a lot of education to do.

[VIDEOSINGLE type="youtube" keyid="gaf2b5bKSzQ", width="560", height="344"]

This video from the University of Maine equine extension department offers basic advice on decreasing your horse's risk for mosquito-born illness.

Speaking of education, horses have a bit of a public relations problem. Perhaps it is because of the word "equine" in Eastern Equine Encephalitis. People say that they won't be going to the fair this year because they are afraid they will get EEE are saying that because they think that the horses are capable of spreading it.

That's just not true. The news media could do horses and equestrian events a favor by clarifying that information. The majority of people who contract EEE and WNV have not been around horses but, year after year, we hear the same fears.

To learn more:

USDA web page on West Nile Virus

USDA web page on Eastern Equine Encephalitis

AAEP handy vaccination chart to download and print

Always consult with a local veterinarian to discuss the risk to your horse, and remember to keep vaccination records handy in case they are needed.


Related