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This is a full transcript of the online presentation. For the
presentation itself, go here.
Begin Transcript:
Hello, this is Rebecca Shultz from the Bureau of Community Environmental
Health of the Florida Department of Health.
Rabies is one of the oldest known contagious diseases of man
and animals, yet it continues to be a serious public health threat and
wildlife management challenge. Rabies is a zoonosis, which is a disease
that can be transmitted from animals, both wild and domestic, to humans.
In this presentation, I will provide an overview of rabies from an
epidemiological and biological perspective. I will continue by
discussing both human and animal rabies. Finally, I will conclude by
presenting current prevention and control efforts. Although rabies in
the global and national context is mentioned, the focus of this
presentation is on rabies in Florida.
Rabies is a disease that is almost always fatal. It causes acute brain
infections in warm-blooded animals, including humans. The most common
mode of transmission is through a bite or scratch of an infected
animal.
Worldwide, there are between sixty-five and eighty-seven thousand human
deaths per year attributed to rabies. Most of these deaths are in
developing countries.
In the United States, around the turn of the twentieth century, there
were approximately 100 human deaths per year attributed to rabies.
Currently, there is an average of 1 or 2 deaths annually. According to
the United States Centers for Disease Control and Prevention, over six
thousand cases of animal rabies were reported in the United States in
the year 2004. Over ninety percent of the reported cases were in
wildlife, which indicates an epidemiologic shift when compared with data
from before the 1960s when most cases were in domestic animals.
Over three-hundred million dollars are spent each year on rabies
prevention and control activities in the United States. Most of this
cost is associated with animal vaccination and control efforts,
laboratory operations and maintenance and medical costs associated with
human post-exposure prophylaxis vaccinations, also known as PEP. The
standard PEP protocol for an unvaccinated person exposed to a rabid
animal exceeds $1,000.
In Florida, there have been only three human cases of rabies detected
since the year 2000. These three cases were considered imported
because the victims did not contract the disease in this country. All
three victims were bitten by rabid dogs in either Haiti or Mexico.
The first locally-acquired case of rabies in Florida was reported in
1881 and the last case was detected in 1948 in Hillsborough County.
There have been a total of 73 reported human cases of Florida-acquired
rabies since the first documented case in 1881.
Although the incidence of cases indicates a downward trend, the threat
of rabies still exists. Rabies is considered endemic in Florida, meaning
that is constantly present to a greater or lesser degree in our wildlife
population.
This map of the United States shows the geographic distribution of
rabies virus reservoirs. It highlights the regional variations and
underscores the importance of animal rabies surveillance as a tool for
developing appropriate control strategies. The predominant animal
reservoir for the state of Florida is the raccoon. Bats are important
reservoirs for rabies as well, both in Florida and the rest of the
country. In upcoming slides, I will discuss in more detail other
important animal reservoirs in the state.
Rabies is a highly fatal infectious disease caused by a neurotropic
virus. The virus is characteristically bullet-shaped, with one end
rounded and the other flattened. Despite the menacing shape, the rabies
virus is actually somewhat fragile. It can easily be inactivated by
acids or bases, including the acid found in the gastrointestinal tract.
It can also be inactivated by sun light, drying, heat, and cold. For
these reasons, the skin is actually a very good barrier against rabies
infection. Simply cleansing the wound can also be an extremely effective
way to prevent infection.
The rabies virus pathogenicity, or ability to produce disease,
contributes to its reputation as one of the most feared zoonotic
diseases. Once introduced into the body, rabies initially replicates in
the muscle, connective tissue, or nerves at the site of inoculation.
Subsequently, the virus moves to the nerve endings, which eventually
leads to a migration to the spinal cord and brain. The virus then
spreads from the brain to the salivary glands and other organs. It can
also alter the animals behavior to make it aggressive or unresponsive.
Once the virus spreads to the salivary glands, the infection produces
large volumes of the virus in the saliva. This abundant virus production
promotes opportunities for continued virus transmission. Infected
animals can transmit the virus when they are clinically ill as well as a
number of days prior to onset of illness.
Incubation periods are variable in all species. The majority of cases
develop clinical disease within twenty to sixty days after infection,
although prolonged periods over one-hundred days have been reported in
both animals and humans.
Infection with rabies occurs most commonly when infected saliva is
introduced into an open wound or abrasion of either the skin or mucous
membrane. The most common mode of transmission is through the bite of a
rabid animal. Virus transmission into bleeding scratches from animals
that regularly lick their feet or paws is also a possibility. Recently,
rabies virus was transmitted between people through organ transplants
including corneal, liver, kidney and blood vessel transplants.
Inhalation of aerosolized rabies virus is a possible, though very
uncommon, route of exposure. Two cases of laboratory-acquired rabies
virus have been reported in workers exposed to aerosolized virus in the
laboratory. Individuals that spend time in infected bat caves may also
be exposed to aerosolized rabies virus.
Rabies in humans can produce a variety of symptoms. Initially, these
may be non-specific symptoms such as headache, fever, or malaise. Other
symptoms may include coughing, sore throat, chills, vomiting, nausea,
diarrhea, and abdominal pain. After 2 to 10 days, the first signs of
neurological involvement appear. These include disorientation,
hallucinations, seizures, and paralysis. Coma occurs 4 to10 days after
symptom onset and may continue for hours or days until death, depending
on the intensity of supportive care.
As mentioned earlier, there is an effective human vaccine against
rabies. The vaccine can be used for both pre and post rabies exposure
treatment. Pre-exposure prophylaxis is a series of three doses of
vaccine generally recommended for individuals who have regular or
prolonged contact with animals, workers in laboratories who conduct
rabies testing, and travelers to an area with a widespread rabies
problem. Post-exposure prophylaxis, or PEP, is also available to people
after they have been exposed to a rabid animal. This involves a series
of vaccines given over a 28-day period; two doses are given to immunized
individuals and 5 doses of vaccine and immunoglobulin are given to
people with no prior history of rabies vaccinations. The vaccine is safe
and effective, however, as with other vaccines it should only be given
when necessary. Minor side effects include pain, swelling, and itchiness
at the site of the injection. Some may experience additional reactions
including nausea, abdominal pain, muscle aches, and dizziness. In
addition to the side effects, PEP can also be quite costly. The standard
protocol for an unvaccinated human exceeds $1,000.
Once a human develops symptoms, rabies is essentially untreatable and
supportive care is initiated. Survival has been documented in 6
symptomatic cases, each of whom had some history of previous rabies
vaccinations. However, mortality is virtually 100% among the
unvaccinated.
We will now focus our discussion on animal rabies, specifically the
animal rabies situation in Florida. Rabies can affect both domestic and
wild animals. In Florida, cats are reported as having rabies more often
than any other domestic animal. This is due in part to the growing
free-roaming cat population. These cats are largely unvaccinated and may
frequently come into contact with both wild animals and people. In
addition, cat owners are less likely to vaccinate their cats against
rabies then they are their dogs. However, vaccination of dogs, cats and
ferrets, is currently mandated by Florida law.
The raccoon is the primary rabies virus reservoir in Florida, though
any mammal can catch the disease. Public health authorities perform
rabies testing on animals that bite people or other animals. Many
different types of wild and domestic animals have been found infected
with rabies in Florida, including those listed here. As expected,
raccoons are more often found infected with rabies than any other animal
species. Skunks and otters can also be involved in rabies outbreaks as
incidental hosts. Rabid rodents and properly vaccinated pets are very
uncommon. It is important to remember that it may be possible for
raccoons, as well as other animals, to shed and transmit rabies virus
before showing symptoms of the disease.
Bats are another animal capable of transmitting rabies. In fact, bat
rabies has accounted for most of the recent human infections in the
United States. Bats are unique in that they have very small teeth, and
their bites can often go undetected. For this reason, anti-rabies
treatment may be recommended if a bat comes into contact with an
unattended child or a sleeping or impaired person. However, its also
important to remember that most bats are healthy and have a valuable
role in the environment.
Animals infected with rabies may show a variety of symptoms. They may
act unusually aggressive or engage in unprovoked attacks. Some wild
animals may act very tame. Many animals will show difficulty swallowing,
eating, or drinking, and may have excessive salivation. They can also
appear unbalanced or paralyzed.
A variety of measures are utilized to prevent and control the spread of
rabies in Florida. As mentioned earlier, it is important that the
vaccination requirements for domestic animals are adhered to. Domestic
animals may be quarantined or isolated for a specified time period to
ensure that it is free of disease.
Another important tool is the management of domestic and wild nuisance
or stray animals. This can minimize contact between humans and animals
of unknown vaccination or disease status. If a person is exposed, the
animal can be captured, and quarantined or euthanized, and submitted to
the laboratory for testing. In some situations, wildlife disease can be
managed by the use of an oral rabies vaccine. Pictured on the bottom
right of this slide are edible baits filled with vaccine. These are
aerially distributed over an area where high levels of raccoon rabies
activity have been documented. Raccoons that consume these baits produce
antibodies to rabies that last between 8-9 months. Studies of oral
rabies vaccine programs have shown them to be effective in reducing
raccoon rabies cases in the targeted area.
Educating and informing the public is an essential piece of rabies
prevention and control. The implementation of public information
campaigns will not only raise awareness about rabies, but will ensure
that the appropriate steps are taken by citizens who find either
themselves or their pets in a situation where rabies exposure is
possible.
Finally, it is necessary to provide education and training to health
care providers, animal control officers, and employees of other partner
organizations. Fostering close ties and communication between agencies
that deal with different aspects of rabies prevention and control is
imperative for a successful program to be achieved.
For additional information on rabies in Florida, please refer to the
Rabies Prevention and Control in Florida, 2006 Guidebook, available on
our website at www.doh.state.fl.us/environment/community/rabies/rabies-index.html.
This document was prepared by the Florida Rabies Advisory Committee, a
group comprised of representatives from the major institutions,
agencies, and organizations involved with rabies prevention and control
throughout the state.
Also on the website, you will find samples of educational materials
created by the Florida Department of Health. These include brochures and
fact sheets in three languages that can be downloaded and printed for
distribution. The website also contains instructions for ordering
materials from the Department of Health distribution center.
Thank you very much for the opportunity to discuss rabies with you
today. For additional information or questions, please contact the State
Public Health Veterinarian, Dr. Carina Blackmore at Carina_Blackmore@doh.state.fl.us,
or by phone at (850) 245-4732.
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