Section III. ZOONOSES: RABIES
Rabies is an acute viral infection of mammals--particularly the carnivores--characterized
by severe irritation of the central nervous system, followed by paralysis and death.
a. Importance to Humans. It is not an important disease from the standpoint of
morbidity, since few human cases occur. Psychologically, however, rabies is extremely
important, in that it is, for all practical purposes, an invariably fatal disease once the
symptoms have appeared. Only one case of a survivor has been documented in the
b. Transmission. The agent causing rabies is a virus present in the saliva of a
rabid animal. The domestic dog is the most important reservoir in transmitting the
disease to man; but many wild animals--especially foxes, wolves, skunks, raccoons,
and bats -- also carry the disease and occasionally have been involved in human cases.
The disease is usually transmitted from animal to animal or animal to man when
infected saliva enters a break in the skin, usually by means of a bite. It is also possible
for the disease to be transmitted by exposure of a fresh wound or skin abrasion to
infected saliva. From the site of entry, the virus travels to the central nervous system
and to the salivary glands.
7-10. CLINICAL FEATURES
a. Incubation Period. The incubation period for rabies is from 30 to 50 days in
man and 3 to 8 weeks in animals, although it has been known to vary from 10 days to
over a year.
In cases where the patient has been bitten extensively or about the head,
the incubation period is shorter.
b. Infective Period. The infective period, during which the virus is present in
the saliva, is from 3 to 5 days before symptoms appear until death, in dogs and cats. In
other animals, it may be much longer.
c. Symptoms in Man.
The early symptoms of rabies in man are mental depression,
restlessness, malaise, and fever.
Restlessness increases to uncontrollable excitement, and spasms of the
pharyngeal muscles cause extreme pain --particularly when trying to swallow or drink
(hence the term hydrophobia, or fear of water).