DEFINITION
An acute viral infection affecting the nervous system of animals. it can be transmitted to humans by a bite or the exposure of broken skin to the animal’s saliva
CAUSES, INCIDENCE, AND RISK FACTORS
Rabies is transmitted by infected saliva that enters the body by a bite or open wound. the virus travels from the wound along nerve pathways to the brain where it causes inflammation that result in the symptoms of the disease. the incubation period ranges from 10 days to 7 years, with the average period 3 to 7 weeks. in the past human cases usually resulted from a dog bite but most recently cases of human rabies have been linked to rabies virus carried by bats. Bats, skunks, raccoons, foxes, and other animals are other sources of rabies victims. the threat of rabies causes extreme fear on the part of people who think they may have been exposed and health care workers who must contend with possible exposures. in new Hampshire, October of 1994, an unknown number of individuals were exposed to a rabid kitten. because exposure could not be well documented 665 individuals received rabies post-exposure prophylaxis at a cost of $1.5 million. This was an extreme reaction by the public to possible exposure. the Centers for Disease Control is presently making recommendations to help prevent unnecessary treatment in questionably exposed individuals.
PREVENTION
Prevention depends upon enforcement of the following public health policies:
- vaccination of dogs every 2 years where rabies exists in wild animals
- vaccination of people in high-risk occupations
- quarantine regulations on importing dogs and other mammals in disease-free countries
SYMPTOMS
- bite by animal, bug, self or others
- dog bite, bat bite, or bite by a skunk, raccoon, or fox (most common animals to transmit)
- low-grade fever (102 F or lower)
- pain at the site of the bite
- swallowing difficulty (thinking produces spasms of the larynx) or swallowing difficulty with liquids only
- restlessness
- excitability
- muscle spasms
- convulsions
- numbness and tingling
- loss of muscle function
- loss of feeling in an area of the body
- drooling
- anxiety, stress, and tension
- positive Babinski’s reflex
SIGNS AND TESTS
If a person has a history of animal bite, the animal will be observed for signs of rabies. Immuno-fluorescence (fluorescent antibody test) performed on the suspect animal may show that the animal has rabies.
PreventionBecause rabies is almost always fatal, prevention is the only reasonable approach, and all exposures must be evaluated individually. Immunization of household dogs and cats and active immunization of persons with significant animal exposure (e.g., veterinarians) are important. the most important common decisions, however, concern animal bites.In the developing world, education, surveillance, and animal (particularly dog) vaccination programs are preferred over mass destruction of dogs, which is followed typically by invasion of susceptible feral animals into urban areas.Local Treatment of Animal Bites and ScratchesThorough cleansing, debridement, and repeated flushing of wounds with soap and water are important. Rabies immune globulin or antiserum should be given as stated below. Wounds caused by animal bites should not be sutured.Post-exposure ImmunizationTherapy is indicated when the disease is seriously under consideration. the decision to treat should be based on the circumstances of the bite, including the extent and location of the wound, the biting animal, the history of prior vaccination, and the local endemicity of rabies. Any contact or suspect contact with a bat is usually deemed a sufficient indication to warrant prophylaxis. Consultation with state and local health departments is recommended. Post-exposure treatment including both immune globulin and vaccination, should be administered as promptly as possible when indicated.The optimal form of passive immunization is rabies immune globulin (20 IU/kg). As much as possible of the full dose should be infiltrated around the wound, with any remaining injected intramuscularly at a site distant from the wound. if immune globulin (human) is not available, equine rabies antiserum (20–40 IU/kg) can be used if available (it was last produced in 2001) after appropriate tests for horse serum sensitivity. An inactivated human diploid cell rabies vaccine (HDCV) is given as five injections of 1 mL intramuscularly (in the deltoid rather than the gluteal muscle) on days 0, 3, 7, 14, and 28 after exposure.Several cell culture vaccines are available and are preferable to embryonated tissue vaccine (e.g., duck embryo vaccine; DEV) because of better antigenic response and fewer systemic reactions. HDCV availability and cost limit its use in the developing world.Rabies immune globulin and rabies vaccine (HDCV) should never be given in the same syringe or at the same site. Allergic reactions to the vaccine are rare, though local reactions (pruritus, erythema, tenderness) occur in about 25% and mild systemic reactions (headaches, myalgias, nausea) in about 20% of recipients. the vaccine is commercially available or can be obtained through health departments. for patients who previously received preexposure or postexposure vaccine, rabies immune globulin should not be given; vaccine, 1 mL in the deltoid, should be given twice (on days 0 and 3).In other countries, the less costly inactivated DEV or mouse brain vaccine may be available, but the method of administration is more complex, the rate of allergic reactions—including ascending paralysis—is higher, and the efficacy is lower.Exposure to rabies still requires postexposure vaccination, even if preexposure vaccination was received, but the need for immune globulin is eliminated (rabies immune globulin is in short supply worldwide).Neither the passive nor the active form or postexposure prophylaxis is associated with fetal abnormalities and thus pregnancy is not considered a contraindication to vaccination.Preexposure ImmunizationPreexposure prophylaxis with three injections of HDCV intramuscularly (1 mL on days 0, 7, and 21 or 28) or intradermally (0.1 mL on days 0, 7, and 28, over the deltoid) is recommended for persons at high risk of exposure: veterinarians (who should have rabies antibody titers checked every 2 years and be boosted with 1 mL intramuscularly or 0.1 mL intradermally if seronegative); animal handlers; laboratory workers; Peace Corps workers; and travelers to remote areas in endemic countries in Africa, Asia, and Latin America. An intradermal route is available for preexposure prophylaxis only. Immunosuppressive illnesses and agents including corticosteroids as well as antimalarials—in particular chloroquine—may diminish the antibody response.TreatmentThis very severe illness with an almost universally fatal outcome requires intensive care with attention to the airway, maintenance of oxygenation, and control of seizures. Universal precautions are essential. other modalities of therapy that may be beneficial include a combination of rabies vaccine, rabies immune globulin, monoclonal antibodies (investigational), ribavirin, interferon-, amantadine, and ketamine. Corticosteroids are of no use.EXPECTATIONS (PROGNOSIS)
If immunization is given within 2 days of the bite, rabies is usually prevented. once the symptoms appear, few people survive the disease. Death from respiratory failure usually occurs within 7 days. COMPLICATIONS
- allergic reaction to rabies vaccine (rare)
- death from respiratory failure 
Courtesy:Compiled and Shared By: Habib Anwar