RabiesRabies is an infectious disease of animals which is a member of a group ofviruses constituting the family Rhabdoviridae. The virus particle is covered ina fatty membrane, is bullet-shaped, 70 by 180 nanometres and contains a singlehelical strand of ribonucleic acid (RNA). Although rabies is usually spread among domestic dogs and wild carnivorousanimals, all warm-blooded animals are susceptible to infection. The virus isoften present in the salivary glands of infected animals, referred to as rabid,and is excreted in the saliva.
The bite of the infected animal easilyintroduces the virus into a fresh wound. In humans, rabies is not usually spreadfrom man to man, rather the majority of infections occur from rabid dogs. Aftera person has been inoculated, the virus enters small nerve ends around the siteof the bite, and slowly travels up the nerve to reach the central nervous system(CNS) where it reproduces itself, and will then travel down nerves to thesalivary glands and replicate further. The time it takes to do this depends onthe length of the nerve it must travel – a bite on the foot will have a muchlengthier incubation period than a facial bite would.
This period may last fromtwo weeks to six months, and often the original wound will have healed and beenforgotten by the time symptoms begin to occur. Symptoms in humans present themselves in one of two forms: furious rabies’, or dumb rabies’. The former is called such because of the severe nature and rangeof the symptoms. The virus, upon reaching the CNS will present the person withheadache, fever, irritability, restlessness and anxiety. Progression may occuron to muscle pains, excessive salivation, and vomiting.
After a few days or upto a week the person may go through a stage of excitement, and be afflicted withpainful muscle spasms which are sometimes set off by swallowing of saliva orwater. Because of this the afflicted will drool and learn to fear water, whichis why rabies in humans was sometimes called Hydrophobia. The patients are alsoextremely sensitive to air or drafts blown on their face. The stage lasts onlyfews days before the onset of a coma, then death.
Dumb rabies begins similarlyto furious rabies, but instead of symptoms progressing to excitement, a steadyretreat and quiet downhill state occurs. This may be accompanied with paralysisbefore death. Rabies diagnosis in this type of cases can be missed. Unfortunately with both furious and dumb rabies, once the disease has taken holdclinically, rapid and relentless progression to invariable death occurs despiteall known treatments.
Treatment for the recently infected would include washing the wound with soap,detergent, and water. Then an anti-rabies serum can be administered to humans. Alternative to the serum, an effective and intensive treatment after infectioncan be obtained through the use of a killed virus vaccine, because of theunusually long incubation period. The vaccine, a Human Diploid Cell Vaccine(HDCV) is grown in human fibroblasts (the principal nonmotile cells ofconnective tissue) and is quite safe for human use. When used, the vaccine diddramatically cut the rabies death toll.
Previous killed virus vaccines, whichhad been made from infected neural tissue, were not completely effective atimmunisation and had caused adverse side effects. Since contact with wild animals is the main source of infection for humans andtheir pets, avoidance of any direct contact with these animals reduces the riskof being bitten quite dramatically. Raccoons that are wandering in the daylighthours, or any animal that seems friendly’ should be avoided as well. Otherhigh-risk animals include skunks, foxes, jackals, wolves, as well as an oddassociation with bats.
