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Fw: Re: USA News: WEST NILE VIRUS
I got a request from someone whose name and address got deleted from my
email in a computer crash regarding whatever information we might have on
West Nile Virus. I checked with a horse friend who works at the Naval
Medical Research Unit and this is what she sent me. Wish I could say we were
hot on the track of a vaccine, but we don't seem to be. However, unstressed,
healthy animals have so far had little or no problem with it here.
Maryanne Stroud Gabbani
----- Original Message -----
From: Elizabeth A Dykstra <DykstraE@namru3.med.navy.mil>
To: 'Maryanne Stroud Gabbani' <firstname.lastname@example.org>
Sent: Tuesday, April 04, 2000 11:10 AM
Subject: RE: Re: USA News: WEST NILE VIRUS
> Dear Maryanne,
> Good morning. Looking up what I have on West Nile virus (or west nile
> fever = WNF). As you probable know by now, it's a mosquito-transmitted
> disease. The mosquitoes in the Culex genus that have been incriminated as
> vectors, as a rule, prefer to lay their eggs in still bodies of water and
> their larvae can survive quite well, thank you, in the nasty water that
> see in the canals over by Giza. If there's not too much of a current in
> them, that is.
> Most of the clinical information that I have is from a PAHO (branch of
> the WHO) publication from 1992, and the literature search I ran on medline
> using "west" "nile" "virus" and "horse*" turned up 2 recent abstracts (Jan
> 2000, Jun 1999) that pretty much support the older PAHO info.
> Horses appear to be the only domestic animal that has shown clinical
> manifestations, although sheep and cattle have also been found with the
> virus (but with no clinical presentation). The virus is maintained in
> nature in a mosquito-bird cycle, with the primary bird reservoirs (on
> record) being crows and pigeon-type birds. Humans and their domestic
> critters are accidentals in the cycle and are what we would term "dead-end
> hosts" i.e., they're not part of the natural cycle, although I'm not sure
> whether or not the mosquitoes could pick up the virus from horses -
> probably a good likelihood they could.
> Clinically, horses show symptoms similar to meningoencephalitis,
> most horses will be asymptomatic and you'll only know they were infected
> the presence of antibodies in the blood. The clinical disease is usually
> mild and only in a few cases will the infection cause encephalomyelitis.
> Affected horses have shown ataxia (an inability to coordinate voluntary
> muscular movements), weakness and paresis (slight or partial paralysis) of
> hindlimbs. In 6 fatal cases, there was paraparesis (Paraplegia- complete
> partial loss of sensation and movement of the legs) progressing to
> tetraplegia (same as paraplegia, except that all 4 legs involved - my
> interpretation - couldn't find it in the dictionary!) and recumbency
> 2 to 9 days.
> A WNF outbreak in 1962-64 in Camargue, France among the horses there
> had a 10% morbidity (10% became ill) and a 25% fatality rate (of those
> 25% died).
> So, with all the above that I've thrown at you, in a nutshell, yes,
> horses can get sick and die from WN virus, however, it's very rare when
> happens. The vast majority of horses will show no symptoms and have no
> problems. As far as vaccines, there's not one at the moment for either
> horses or humans.
> Below is a website URL that has some additional information on WN.
> Hope this answers your friends' questions. Let me know if I can be of
> further help!
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