Rabies Guide 2010.pdf - the South African Veterinary Council

RABIES IN HUMANS
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Epidemiology of human rabies
Rabies is an ongoing scourge exacting an
unnecessarily large toll on human life. The World
Health Organization estimates about 55 000 human
deaths in canine rabies endemic areas (31 000 in
Asian countries and 24 000 in African countries)
annually. 43, 44, 45, 159 Rabies virus is transmitted via the
saliva of infected animals and has the highest case
fatality rate of any known human infection if the
disease has manifested. Once the virus has entered
the central nervous system of the host, the resulting
encephalomyelitis is fatal. Fortunately the availability
of efficacious and safe vaccines and immunoglobulin
has prevented many fatalities and almost 10 million
people receive post-exposure prophylaxis annually
after potential rabies exposure, mostly following dog
bites.
Rabies and the developing world
Rabies remains endemic throughout the world except
for certain Western European countries and a number
of islands, but more than 99% of all human rabies
deaths occur in the poorest developing countries. 45,46,47
Recorded deaths in developing countries probably
provide a gross underestimate of the true situation as
these areas generally have notoriously poor notification
systems. Reasons underlying the preponderance of
rabies cases in poor countries are complex but include
opposing needs and limited resources for veterinary
control, the prohibitive cost of post-exposure vaccine
and immunoglobulin, poorly informed communities,
inadequately trained health and veterinary staff, and
inaccessibility of health-care facilities. 48,49,50
Of considerable concern is the re-emerging status of
rabies in Africa. 51,173 This trend has been attributed
to rapid population growth with parallel dog
population growth directed by security concerns,
for example a growth of 4,7% in the dog population
in Zimbabwe between 1954 to 1986, mobility of
human populations, particularly political refugees,
high rates of urbanisation and a disintegration
of veterinary rabies control. 52,53,54 The latter is of
particular importance as dog rabies vaccination is a
more cost-effective measure for preventing human
rabies than reliance on post-exposure prophylaxis for
dog-bite victims. 55
Distribution in South Africa
During the first half of the 20th century most human
rabies cases in South Africa resulted from herpestid,
particularly yellow mongoose, bites in the central
plateau areas. However, following the introduction of
canid virus into Limpopo Province in the late 1940s,
and later into KwaZulu-Natal in 1961, dogs became
the most important source of human infection. In
recent years (Table 9) the vast majority of South
African human rabies cases have followed bites from
infected dogs in KwaZulu-Natal. 56,57 An outbreak of
rabies in dogs coincided with a dramatic increase in
the number of human cases in the Limpopo Province
in 2006. 184
Most victims have been children under the age of 10
years. Children are particularly vulnerable because of
their height, inquisitive nature, interest in animals
and inability to protect themselves. Surveillance of
human rabies is poor in many parts of South Africa
and it is likely that the situation may be worse than
that reflected by official notifications. A careful
history taken from a victim’s family has demonstrated
a high sensitivity for diagnosing rabies in other
African settings and may prove a useful approach in
areas suspected of having rabies cases that have not
been notified. 58
Canine vaccine delivery targeted to highest risk
populations and broad intersectoral collaboration are
believed to have contributed to the marked reduction
in human rabies in KwaZulu-Natal during the latter
part of the 1990s. 59,60
Transmission to humans
Human rabies cases result from viral introduction
through broken skin or mucosa through encounters
with rabid animals, particularly bites but also scratches
and nicks. Virus is usually present in the saliva of the
affected animal during clinical disease but secretion
may be intermittent. Experimental demonstration of
virus in salivary glands or saliva several days before