Rabies
Rabies is an infectious viral disease
affecting human, domestic and wild animals. Human get this infection from
infected animals, usually from the saliva of dog when it bites. Other rabid
animals that can carry this virus are bat, monkey, cat, fox, raccoon,
mongoose, pig and several other species. All reported rabies infections are
from mammals.
Rabies human deaths are estimated to be 50,000
each year. But the actual infected population may be higher as no global rabies
monitoring system exists.
The World Health Organization
(WHO) reports:
99%
of reported annual rabies deaths occur in Asia, Africa and South America.
90%
deaths occurs in Asia.
60%
deaths occurs in India; incidence is 3 in 1,00,000 population a year.
Rabies
virus belongs to the Lyssavirus genus. There are 7 types in Lyssavirus,
in which classic rabies virus represents the type 1. Once transmitted, the
incubation period (time between exposure to the virus and symptoms become first
apparent) is generally between 20 and 90 days, but it can also be of 4 days to
several years in certain extremes cases.
Rabies virus is nuerotrophic which affects the
nervous system of human and animals. As the virus spreads in the central nervous
system (like brain), progressive inflammation of the brain (encephalitis)
develops. The initial symptoms of rabies are often pain, mild fever or abnormal
sensation of the skin like pricking, tingling or numbness (paraesthesia) of the
limb. Once symptoms develop, rabies is fatal to both animals and humans, if
not treated immediately. Advanced symptoms
include hydrophobia (difficulty swallowing liquids), aerophobia (difficulties in
inhalation, breathlessness), photophobia (excessive sensitivity to light and
tendency to avoid light) and (or) paralysis.
Nerve
Tissue Vaccines (inactivated rabies infected brain tissues from animals) is once
a staple in rabies prevention and is being phased out as it has serious side
effects human such as paralysis. Modern rabies vaccines such as, cell culture
rabies vaccines (CCRV) and purified chick-embryo cell vaccine (PCECV) and
purified Vero cell rabies vaccine (PVRV) are in common use and administered by
intradermal (inside the skin) or intramuscular (inside the muscle) routes.
Human rabies in Indian context
Most
animal bites in India are due to dogs (92%), followed by monkeys (3%), cats (2%)
and other mammals. Rural areas account for 76% of human rabies cases. In many
cases the human victim follows dogs closely for symptoms of rabies. If dogs are
non-symptomatic the human victim is unlikely to seek any medical advice.
Approximately 59% of animal bite victims resort to faith healing, herbal therapy
or self treatment. An Indian scientific report in 2008 suggests that rabies incidence
is reducing from 3 in 1,00,000 to 2 in 1,00,000 (0.003 to 0.002%) in human.
Table 1. WHO
compilation of human rabies data in Asia for 2004.
