History, pathology, clinical symptom and prophylaxis of rabies

Ronald Panmei *

Rabies apprehension at Churachandpur on January 15 2015 :: Pix - TSE

Rabies, also called Hydrophobia (Lyssa, Rage or Mad dog) is a deadly virus spread to people or another animal from bites of rabies infected animal. It is an acute viral encephalitis(inflammation of brain) which affects man and other warm blooded animals.The symptoms are characterized by signs of abnormal behavior, nervous disturbances, impairment of consciousness, ascending paralysis and death. Animals like dog, fox, wolf, jackal, skunk, mongoose, cat, rat, squirrels, vampire bat are extremely susceptible in tropical areas of the world.

Cattle, goat and sheep are moderately susceptible but Reptiles and birds don't get rabies. Rabies in animals exist in 2 epidemiological types Urban type i.e.transmission takes place through dogs (stray) and another type is Sylvatic type i.e through wildlife (e.g. fox, jackal, wolf, skunk, mongoose, vampire bat, hyena, etc.

HISTORY OF RABIES

Virus was 1st documented in Egypt before 2300 B.C. and in ancient Greece, where it was described by Aristotle but in India report of rabies was in 5000 years ago in Vedic period and The method of transmission of rabies was not recognized until 1804. India is a rabies endemic area estimated population of 5000 die every year. A scientific or experimental approach to rabies was delayed until 1793, when John Hunter published his very important paper, "Observations and heads of enquiry on canine madness".

Hunter suggested that the transmission of rabies should be studied by inoculating saliva from rabid animals and humans into dogs and that attempts should be made to inactivate the "poison" in the saliva. These ideas may have inspired the experiments by Zinke (1804) and Magendie and Breschet (1813). Zinke used a paintbrush to introduce saliva from rabid dogs into incisions made in the skin of dogs, cats, rabbits, and chickens, which duly developed signs of rabies.

In the same year Magendie and Breschet infected dogs with saliva from human patients with hydrophobia. Galtier (1879) was responsible for an important technical advance. He found that rabbits could be infected with rabies and were far more convenient experimental animals than dogs. Pasteur adopted the use of rabbits in his studies of rabies begin in 1880.He was the first to recognize that the major site of infection was the CNS.

Attenuation of the fixed virus was achieved by desiccation of rabbit spinal cord for up to 14 days. Pasteur was able to protect dogs from challenge by immunizing them with the desiccated material, and in 1885 he used his vaccine for the first time in Joseph Meister, a boy severely bitten by a rabid dog and was successful.Improvements in Pasteur's vaccine were achieved by Semple and Fermi, who killed the virus rather than attenuated it, and by Fuenzalida and Palacios developed a suckling mouse brain vaccine which carried a lower risk of neuroparalytic complications.

The use of passive immunization with equine hyperimmune serum has been vindicated by the famous natural experiment following an attack by a rabid wolf on 29 people in Iran in 1954. Usually rabies is transmitted in the saliva, when an infected animal bites another (virus in saliva 2 days before onset of signs). Less often, spread by any contact between infectious saliva or neurological tissues, & mucous membranes or breaks in skin.

Virus is not transmitted through intact skin. Rarely Aerosol transmission has been documented in laboratories and bat caves with a high density of aerosolized virus particles.It has also have documented that it has been transmitted by ingestion of laboratory animals.

The pathology condition is that virus enter via animal bite,then virus replicate in muscle at the sie of bite then virus infect the nerve in peripheral nervous system moves by retrograde transport then virus replicate in spinal cord to brain,brain got infected,virus travels from brain via nerve to other tissue such as eye kidney salivary gland.

Clinical sign in man : After several days, anxiety, confusion & agitation may appear, and progress to insomnia, abnormal behavior, hypersensitivity to light and sound, delirium, hallucinations, slight or partial paralysis, hypersalivation,difficulty swallowing, pharyngeal spasms upon exposure to liquids, and convulsions. Either an encephalitic (furious) form with hyperexcitability, autonomic dysfunction and hydrophobia, or a paralytic form characterized by generalized paralysis, may predominate.

Death usually occurs within 2 to 10 days; survival is extremely rare. Animals can display aggressive behavior, ataxia, irritability, anorexia, lethargy or excessive salivation. Cats are more likely to be aggressive than dogs.

Hydrophobia : Patient can't swallow because of violent jerky contraction of diaphragm and accessory muscles of inspiration when patient attempts to swallow liquid. Patients will be terrified during this reaction and may even experience this at the sight of water or if water touches their face. Aerophobia:an extreme fear of air in motion can be elicited from some patients. This can also cause violent muscle spasms in the neck and pharynx, hallucinations, seizures, ataxia, focal weakness and arrhythmias can occur.Other form is "dumb" or paralytic rabies. Management of rabies are of No effective treatment exists yet but Postexposure Prophylaxis/PEP are of 3 steps :

1. Wound care : immediate thorough washing with soap and water and a virucidal agent such as povidine-iodine or 1-2% benzalkonium chloride. Shown to be protective if performed within 3 hours of exposure. If puncture, swab deeply in wound and around edges.

2. Passive Immunization : Human rabies immunoglobulin (HRIG) 20 IU/kg ASAP, but not longer than 7 days after vaccine is given. Infiltrate entire dose around wound, any remaining IG inject IM at a site distant from the vaccine.

3. Human diploid cell vaccine (HDCV): 1 ml (deltoid) on days 0,3,7,14,28. Vaccine : Do not give in gluteal. If injected into fat, no antibodies formed. HRIG and HDCV: Give in different anatomical sites and never in the same syringe. Reactions : Itching, erythema, pain, swelling

Systemic : HA, myalgia, nausea.