Dr. Rupprecht FAX'ed me a copy of the Rabies abstract today. Here is a
transcribed copy.
Dick B.
Pathogenesis of rabies virus variants in domestic ferrets
M. Niezgoda, D.J. Briggs, J. S. Shaddock, C.E. Rupprect
Domestic ferrets are popular companion animal in the United States, raising
critical questions for public health officials responsible for the management
of ferret bites to human beings, as regards the potential risk for rabies.
Healthy vaccinated ferrets that bite human beings may be routinely
euthanatized and examined for rabies, rather than be held and observed,
largely from lack of information on response to rabies virus infection.
Neither clinical signs nor virus excretion in saliva are well documented.
Recent studies have investigated ferret response using virus variants
associated with North American wildlife. Ferrets received intramuscular
viral inocula and were held over 120 days. Samples included oral cavity
swabs, body weights, rectal temperatures, and blood.
Bat rabies virus isolates included those associated with the big brown bat
(Eptesicus fucus), Mexican free tailed bat (Tadarida brasiliensis), silvered
haired bat (Lasionycteris noctivagans), and the red bat (Lasiurus borealis)
at doses that ranged from 10^4.7 to 10^3.4 MILCD50.
To date, 23 of 42 (55%) ferrets were euthanitized with clinical signs of
rabies. Mean incubation period was 22 days (range 10 - 44 days), and mean
morbidity period was 3 days (range 1 - 6 days). Clinical signs included
ataxia, lethargy, fever, paresis, parapareses, paralysis and cachexia. Ten
of 23 (44%) had aggressive behavior. Three of 23 (13%) rabid ferrets
contained rabies virus in their salivary glands, and one of these shed virus
in their saliva (concomitant with clinical signs).
In contrast to previous studies, ferrets given a skunk rabies virus variant
at doses that ranged 10^5.5 to 10^1.5 MICLD50 had mortality rate of 33/50
(66%). Mean incubation period was 33 days (range 16-96 days), mean
morbidity period was 4-5 days (range 2 to 10 days). No ferrets given skunk
virus had signs of aggressive behavior. Only 1 of 33 (3%) rabid ferrets
contained rabies virus in their salivary glands, and none shed virus in
their saliva.
In ferrets given a raccoon rabies virus variant at doses that ranged 10^5.8
to 10^4.0 MICLD50, 19/51 (37%) ferrets were euthanatized due to rabies.
Mean incubation period was 28 days (range 17 to 63 days), while mean
morbidity period was 4 to 5 days (range 1 to 8 days). Clinical signs
included inactivity, lethargy, constipation, hypothermia, ataxia, paresis,
paraparesis, and paralysis. Two of 19 (10%) rabid ferrets had signs of
aggressive behavior. From the 19 ferrets euthanatized with clinical signs,
rabies virus was isolated from the salivary glands of 12 (63%); nine of
these (47%) shed virus in their saliva (largely concomitant with clinical
signs).
Preliminary studies have also investigated ferret response to a coyote
rabies virus variant at doses that ranged from 10^3.3 to 10^2.3 MICLD50;
mortality was 11/12 (92%), preliminarily, mean incubations period was 14
days (range 11 to 19 days), and mean morbidity period was 4 to 5 days (range
3 to 6 days). Clinical signs included ataxia, lethargy, pareses, paralysis,
myoconus, and fever. The majority of rabid ferrets (10/11), 91%) had signs
of aggressive behavior. To date, 5 of 6 salivary glands collected from
these rabid ferrets contained virus and 3 shed virus in their saliva. [no
number given]
Clearly, ferret response to rabies virus infection regarding susceptibility,
aggressive behavior, spread of virus to salivary glands and excretion , were
significantly dependent on the virus variant.
[Forgive the typos.]
[Posted in FML issue 2132]
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