Infectious Disease Report: Rabies By: Anu Gandhi and Val Riguero

What are Rabies? Rabies virus causes an acute encephalitis (inflammation of the brain) in all warm-blooded hosts. Rabies virus causes an acute encephalitis (inflammation of the brain) in all warm-blooded hosts. Rabies is not, in the natural sense, a disease of humans. Rabies is not, in the natural sense, a disease of humans. The impact of rabies on public health includes an estimate of the animal population that is affected and the steps involved in preventing transmission of rabies from animals to humans. The impact of rabies on public health includes an estimate of the animal population that is affected and the steps involved in preventing transmission of rabies from animals to humans. Raccoons, skunks, foxes, coyotes, and several species of insectivorous bats have been identified as reservoirs for the disease. Raccoons, skunks, foxes, coyotes, and several species of insectivorous bats have been identified as reservoirs for the disease.

Rabies in History Rabies cases have been reported since before 2300 BC. Rabies cases have been reported since before 2300 BC. 1 st century AD a Roman scholar named Aulus Cornelius Celsus gave the first accurate description of the disease 1 st century AD a Roman scholar named Aulus Cornelius Celsus gave the first accurate description of the disease 1 st scientist to test rabies infection through inoculation of saliva was a German scientist named Zinke in st scientist to test rabies infection through inoculation of saliva was a German scientist named Zinke in 1804

Pasteur’s Contribution 1885 he published a method for protecting dogs against rabies 1885 he published a method for protecting dogs against rabies A dog exposed to rabies was protected by inoculation with an emulsion prepared from the dried spinal cord of a diseased rabbit A dog exposed to rabies was protected by inoculation with an emulsion prepared from the dried spinal cord of a diseased rabbit Pasteur had the chance to test this same method on humans when Joseph Meister, a nine-year-old boy who was bitten by a rabid dog was brought to him in July of 1885 Pasteur had the chance to test this same method on humans when Joseph Meister, a nine-year-old boy who was bitten by a rabid dog was brought to him in July of 1885

Joseph was injected over several days with the emulsions prepared from animal spinal cord material Joseph was injected over several days with the emulsions prepared from animal spinal cord material After 2 weeks, Joseph was given an injection of virus that had maximal virulence when tested in a rabbit After 2 weeks, Joseph was given an injection of virus that had maximal virulence when tested in a rabbit Joseph survived as did thousands of others treated by the same procedure. Joseph survived as did thousands of others treated by the same procedure.

Epidemiology In 2001, 49 states, the District of Colombia, and Puerto Rico reported 7,437 cases of rabies in animals to the Center of Disease Prevention and Control and no cases in humans were reported. In 2001, 49 states, the District of Colombia, and Puerto Rico reported 7,437 cases of rabies in animals to the Center of Disease Prevention and Control and no cases in humans were reported. Pennsylvania reported the largest number of rabid domestic animals (46) for any state, followed by New York (43) Pennsylvania reported the largest number of rabid domestic animals (46) for any state, followed by New York (43) The number of rabies-related human deaths in the U.S. has declined from 100 or more each year at the turn of the century to an average of 1-2 each year in the 1990’s The number of rabies-related human deaths in the U.S. has declined from 100 or more each year at the turn of the century to an average of 1-2 each year in the 1990’s

Morphology Order- Mononegavirales Order- Mononegavirales Nonsegmented Nonsegmented Negative stranded RNA genome Negative stranded RNA genome “Bullet” shaped- Rhabdovirus 180nm x75nm “Bullet” shaped- Rhabdovirus 180nm x75nm 400 trimeric spikes on surface of virus 400 trimeric spikes on surface of virus 2 major structural components 2 major structural components –Helical RNP core –Surrounding envelope

Physiology Genome encodes 5 proteins: Genome encodes 5 proteins: –Nucleoprotein- encases RNA –Phosphoprotein- associated with ribonuceoprotein core –Matrix protein- central protein of rhabdovirus assembly –Glycoprotein- forms 400 trimeric spikes –Polymerase- transcribes genomic strand of rabies RNA

Virulence Depends on severity of bite Depends on severity of bite If treatment is given and when If treatment is given and when Once the disease manifests in CNS: ultimate death Once the disease manifests in CNS: ultimate death

Pathogenicity Defined by encephalitis and myelitis Defined by encephalitis and myelitis Perivascular infiltration throughout entire central nervous system Perivascular infiltration throughout entire central nervous system Causes cytoplasmic eosinophilic inclusion bodies (Negri bodies) in neuronal cells Causes cytoplasmic eosinophilic inclusion bodies (Negri bodies) in neuronal cells Several factors may affect outcome of rabies exposure. Several factors may affect outcome of rabies exposure. –Rabies variant –Dose –Route –Location of exposure –Individual host factors

Transmission Begins when infected saliva of host is passed to uninfected animal. Begins when infected saliva of host is passed to uninfected animal. Scratches Scratches Bites Bites

Discharge and Intermediate Hosts Infection of new host via saliva Infection of new host via saliva Death of host Death of host Wild rabid animals may infect domestic animals/people Wild rabid animals may infect domestic animals/people –Cattle, horses, pigs, dogs, cats –Humans Rabid domestic animals may infect humans Rabid domestic animals may infect humans

Vehicles of Transmission Saliva Saliva Mucous membranes Mucous membranes Aerosol transmission Aerosol transmission Corneal transplantations Corneal transplantations

Symptoms of Rabies The first symptoms of rabies may be non- specific flu- like signs, such as malaise, fever or headache which may last for days. The first symptoms of rabies may be non- specific flu- like signs, such as malaise, fever or headache which may last for days. There may be discomfort or paresthesia at the site of exposure (bite) progressing within days to symptoms of cerebral dysfunction, anxiety, confusion, and agitation which eventually progress to delirium, abnormal behavior, hallucinations, and insomnia. There may be discomfort or paresthesia at the site of exposure (bite) progressing within days to symptoms of cerebral dysfunction, anxiety, confusion, and agitation which eventually progress to delirium, abnormal behavior, hallucinations, and insomnia.

Rabies Diagnosis in animals The direct fluorescent antibody test (dFA) is the test most frequently used to diagnose rabies. This test requires brain tissue from animals suspected of being rabid. The direct fluorescent antibody test (dFA) is the test most frequently used to diagnose rabies. This test requires brain tissue from animals suspected of being rabid. The dFA test is based on the fact that infected animals have rabies virus proteins (antigen) present in their tissues. The dFA test is based on the fact that infected animals have rabies virus proteins (antigen) present in their tissues. Positive dFA Negative dFA

Rabies Diagnosis in humans Saliva can be tested by virus isolation or reverse transcription by polymerase chain reaction (RT-PCR). Saliva can be tested by virus isolation or reverse transcription by polymerase chain reaction (RT-PCR). Serum and spinal fluid are tested for antibodies to rabies virus. Serum and spinal fluid are tested for antibodies to rabies virus. Skin biopsy specimens are examined for rabies antigen in the cutaneous nerves at the base of hair follicles. Skin biopsy specimens are examined for rabies antigen in the cutaneous nerves at the base of hair follicles.

Methods of Cure Rabies Vaccine: A killed virus vaccine (Human Diploid Cell Vaccine, HDCV) grown in human fibroblasts is available for safe use in humans. Rabies Vaccine: A killed virus vaccine (Human Diploid Cell Vaccine, HDCV) grown in human fibroblasts is available for safe use in humans. The unusually long incubation period of the virus permits the effective use of active immunization with vaccine post-exposure. The unusually long incubation period of the virus permits the effective use of active immunization with vaccine post-exposure. If rabies has not been diagnosed and the victim is not treated with a vaccine and the clinical disease manifests, it is nearly always fatal, and treatment is typically supportive. If rabies has not been diagnosed and the victim is not treated with a vaccine and the clinical disease manifests, it is nearly always fatal, and treatment is typically supportive.

Related Studies In the journal Antibiotics and Chemotherapy, an article was published which presented the results of an experimental study of the action of rifampicin on the process of rabies infection in albino mice contaminated with 1-10 LD50 of the fixed rabies virus. In the journal Antibiotics and Chemotherapy, an article was published which presented the results of an experimental study of the action of rifampicin on the process of rabies infection in albino mice contaminated with 1-10 LD50 of the fixed rabies virus. Exposure to rifampicin in doses of mg/mouse resulted in survival of % of the animals respectively while the controls did not exceed %. Exposure to rifampicin in doses of mg/mouse resulted in survival of % of the animals respectively while the controls did not exceed %.

The infection of target cells by rabies is effected through membrane receptors; it has been suggested that nicotonic receptors could be used by the virus. The infection of target cells by rabies is effected through membrane receptors; it has been suggested that nicotonic receptors could be used by the virus. In a study published in Neuroscience Letters, mouse dorsal root ganglia cells were treated with various nicotonic antagonists (mecamailamine, d- tubocurarin, hexametonium, etc.). In a study published in Neuroscience Letters, mouse dorsal root ganglia cells were treated with various nicotonic antagonists (mecamailamine, d- tubocurarin, hexametonium, etc.). After incubation the cultures were infected with the rabies virus, the cells were then processed for immunodetection of rabies virus. After incubation the cultures were infected with the rabies virus, the cells were then processed for immunodetection of rabies virus. Treatment with mecamilamine or d-tubocurarine reduced the % of infected neurons. Treatment with mecamilamine or d-tubocurarine reduced the % of infected neurons.

Control and Prevention Pre-exposure prophylaxis vaccination Pre-exposure prophylaxis vaccination Post-exposure prophylaxis Post-exposure prophylaxis If you are exposed to a possible rabid animal: If you are exposed to a possible rabid animal: –Wash wound with soap and water –Seek medical attention immediately

Control and Prevention Be a responsible pet owner Be a responsible pet owner –Keep vaccinations up to date –Keep pets under direct supervision –Spay and neuter pets Enjoy wild animals from far away Enjoy wild animals from far away Don’t adopt wild animals Don’t adopt wild animals “Love your own, leave others alone” policy “Love your own, leave others alone” policy

References National Center for Infectious Diseases National Center for Infectious Diseases Microbial Life, Perry Microbial Life, Perry Keen, Anthony Keen, Anthony Rabies.com Rabies.com Antibiotiki Khimioterapiia Antibiotiki Khimioterapiia Zubovich,I K Volume 34, Issue 2, Feb 1989, Partial inhibition of the in vitro infection of adult mouse dorsal root ganglion neurons by rabies virus using nicotinic antagonists Partial inhibition of the in vitro infection of adult mouse dorsal root ganglion neurons by rabies virus using nicotinic antagonists Castellanos, J E, Neuroscience Letters, Volume 229, Issue 3, July 4, 1997