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A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Wed 13 May 2009
Source: Forbes.com, HealthDay News report [edited]
Man dies of brain inflammation caused by deer tick virus
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In what scientists say might be the 1st case of its kind, a new report
details the story of a 62 year old man in New York state who died last year
(2008) of meningoencephalitis, apparently after being bitten by a deer tick
infected with deer tick virus. This appears to be the 1st reported human
illness from the virus, although the organism was isolated in the brain of
a person in Ontario, Canada. In this instance, there was no description of
illness associated with that infection, said Norma P Tavakoli, lead author
of the paper appearing in the 14 May 2009 issue of the New England Journal
of Medicine [see reference in comment below. - Mod.CP]
"Deer tick virus encephalitis [inflammation of the brain] is rare, but
diagnostic testing is not routinely performed, so there could be cases out
there we're actually missing," said Tavakoli, who is a research scientist
with the Wadsworth Center, New York State Department of Health in Albany.
"Certainly, during early spring to fall in areas where infected ticks have
been reported, testing should be done. It is quite a rare virus," said Dr
Geoffrey Weinberg, a professor of pediatrics in the division of pediatric
infectious diseases at the University of Rochester Medical Center. "I would
advise people not to be overly concerned. Ticks are less commonly infected
with this than with Lyme disease. Also, the odds are 300 to one that
someone infected with the virus will develop encephalitis. The vast
majority have no symptoms at all."
For the average outdoorsman, precautions already recommended to avoid
contracting Lyme disease -- also transmitted via deer ticks -- should
decrease the odds of getting the deer tick virus as well, according to the
study. "Whether or not this will become a real problem, I don't think
anybody knows. Obviously, there is no treatment for the virus so, really,
prevention is the only thing you can do," said Dr Peter Welch, an
infectious disease specialist with Northern Westchester Hospital in Mt
Kisco, NY. "We should always be cautious to do our best to not be bitten by
ticks. Check for ticks when you come out of the woods or anywhere there are
ticks. Wear insect repellant, which contains DEET." Wearing light-colored
clothing, removing any ticks as soon as they are found, and keeping pets
free of ticks can also reduce the risk, Tavakoli added.
Deer tick virus is closely related to Powassan virus, which can also cause
encephalitis and is also transmitted by way of the deer tick, according to
background information in the study. Both are flaviviruses, a group that
includes West Nile virus, St Louis encephalitis virus, dengue, and yellow
fever viruses, all of which are transmitted by mosquitoes. Infection with
one of these viruses sometimes causes severe illness, some combination of
milder symptoms, or no illness at all.
Deer ticks also transmit Lyme disease, which is now widespread in the
United States. In the New York case, a 62 year old man from Putnam County,
NY, arrived at a local hospital in spring of 2008 complaining of fatigue,
fever, rash, and muscle weakness. Doctors first suspected West Nile virus,
but analysis of tissue samples eventually came up positive for deer tick
virus only. The patient spent a good deal of time outdoors, owned horses,
and lived in a county with many reports of Lyme disease, indicating a large
tick population. Although the man had not reported any tick bites, the time
of the year was right for such an event, and many deer ticks are so small
as to remain undetected. Unfortunately, the man's condition continued to
deteriorate, life support was withdrawn, and the man, who also had leukemia
and therefore possibly a weakened immune system, died 17 days after he fell
ill.
In general, Welch said, encephalitis cases of any sort are few, and labs
are not usually able to identify the source, unless it is the herpes
simplex virus. "Since no one has been testing, we really don't know the
incidence of deer tick virus, but it can't be very high, because we don't
have many cases of encephalitis," he said. "What happens in the future will
depend on how many ticks get infected, how easy it is to transmit to
people, and what per cent of people infected get severe disease. It could
be that people with normal immune systems are relatively resistant."
--
communicated by:
ProMED-mail rapporteur Susan Baekeland
[The research described above was published in the 14 May issue of the New
England Journal of Medicine (Norma P Tavakoli, Heng Wang, Michelle Dupuis,
Rene Hull, Gregory D Ebel, Emily J Gilmore, et al. Fatal case of deer tick
virus encephalitis. N Engl J Med 2009; 360: 2099-107.
Summary: "Deer tick virus is related to Powassan virus, a tick-borne
encephalitis virus. A 62 year old man presented with a meningoencephalitis
syndrome and eventually died. Analyses of tissue samples obtained during
surgery and at autopsy revealed a widespread necrotizing
meningoencephalitis. Nucleic acid was extracted from formalin-fixed tissue,
and the presence of deer tick virus was verified on a flavivirus-specific
polymerase-chain-reaction (PCR) assay, followed by sequence confirmation.
Immunohistochemical analysis with antisera specific for deer tick virus
identified numerous immunoreactive neurons, with prominent involvement of
large neurons in the brain stem, cerebellum, basal ganglia, thalamus, and
spinal cord. This case demonstrates that deer tick virus can be a cause of
fatal encephalitis."
Deer tick virus is a newly described member of the mammalian tickborne
virus group. The members of this group are classified as the virus species:
_Gadge Gully virus_, _Kyasanur Forest disease virus_, _Langat virus_,
_Louping ill virus_, _Omsk hemorrhagic fever virus_, _Powassan virus_,
_Royal Farm virus_, and _Tick-borne encephalitis virus_. Of these viruses
deer tick virus is most closely related to Powassan virus. - Mod.CP
A photograph of a deer tick (_Ixodes scapularis_) can be seen at
located on the HealthMap/ProMED-mail interactive map at
.................cp/mj/sh
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