West Nile

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West Nile Virus

The West Nile Virus (WNV) is a mosquito-borne flavivirus that was first diagnosed
in North America in the New York City area in 1999. WNV primarily causes disease
in birds, humans and horses and is transmitted by many different species of mosquitoes.
Since 1999, over 16,000 U.S. horses have been confirmed for WNV encephalomyelitis.
During 2002, over 15,000 horses were affected with an approximately 30% mortality
rate. WNV is now considered endemic with yearly activity in the United States, Canada,
Mexico and the Caribbean.

Recently it has been reported that the incidence of human cases of WNV has been
increasing. There are many theories as to why this might be. Some speculate weather
related changes, while others have attributed possible viral mutations as causes
for the increase in cases. The ‘outbreak’ of human cases has not resulted in a
similar increase in equine cases. This might be due to diligent vaccination of our
patients or possible mutation of the virus resulting in increased potency to people.

There is a wealth of information that can be found that is up-to-date. The links
below are to the American Association of Equine Practitioners (AAEP) and Texas
Department of State Health Services.

http://www.aaep.org/pdfs/control_guidelines/West%20Nile%20Virus.pdf [http://r20.rs6.net/tn.jsp?e=001xlceMhVD8dGg_S3S7U0ApgyXLxpwKJX7gmm1WtblGc8gH7N0I-1l8Z7zaeAii8YXdpDFcEXDHkqaEf-ttLl7W6nn59f5hPpTDVE1PdEOiOkS_mwbT_gnCsyz2rPzo9et8Da6F8In8nCxGHSebBN86p-LS7jEcPlZtIn-A5M9s17OyKRYgN84Ng==]

http://www.dshs.state.tx.us/idcu/disease/arboviral/westnile/ [http://r20.rs6.net/tn.jsp?e=001xlceMhVD8dHKY4ZeJAZIHyQYjvZb3hMR11pEoLq0OqOohHOtaPr9LoQZTtJ6fmS4lDCbf14SIWIGCanvDClnyM7GpyfCMWjticaD1-rc62BBc2X-Dd1i2zwGVKEnXBoGHlVCPiw15tYOV1z3_vLSzLU2icaJTGJsImcw7aSyKhU=]

All of this information serves as a reminder that we need to continue vaccinating
our horses for West Nile. The West Nile vaccine has become and it appears that it
will continue to be a core vaccine. This means that we need to vaccinate for the
disease annually and also make sure that young horses or horses that have never
been vaccinated receive a booster 3-6 weeks after the initial vaccination.
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