Rabies :Transmission and Clinical features

Rabies, tetanus

Australia

The prinicple routes of transmission of rabies virus are animal bites, licks on abraded skin or mucosa, through aerosols and through person to person contact.

Rabies can also be transmitted through corneal and organ transplants.

Aerosol transmission may occur in caves harbouring rabies infected bats.

Person to person transmission is also on record.

Eg – an infected child biting its parent.

Ingestion of the virus is not believed to transmit the disease as the virus would be destroyed by stomach acid/enzymes.

Ref: Park, Edition 21, Page 252

A rabies free zone is one where no indigenously acquired case of rabies has been reported in the last 2 years.

In India, Andaman and Nicobar islands and Lakshwadip has been declared as rabies free zone.

Furious Rabies generally manifests as headache, fever, irritability, restlessness and anxiety.

It is associated with dilated pupils, lacrimation, salivation and perspiration.

Muscle pains, salivation and vomitting may follow.

A few days following exposure the patient may experience a stage of excitement or muscle spasms initiated from the ingestion of of saliva or water. As a result these individuals have a tendency to drool and begin to fear water or hydrophobia. This excited phase continues for a few days until the patient lapses into a coma and dies.

Dumb Rabies manifests itself in the opposite manner as Furious Rabies. Instead of demonstrating excitement the patient experiences depression and paralysis followed by a coma. Death eventually results from respiratory arrest. This form of the virus is often difficult to diagnose from a clinical perspective.

Ans. is ‘None’

.   The immunity following vaccination with neural vaccines is expected to last for six months only.

.   CNS infection occurs by axoplasmic transport of the virus.

.   It is Bullet shaped enveloped, Single stranded RNA Virus.

.   Rabies virus is of single serotype only, with two strains i.e., street virus and fixed virus.

Ans. is ‘b i.e., Brainstem encephalitis

.      Rabies is a severe encephalitis, mainly involves :

–      Rhombencephalon (Brainstem – Mid brain and floor of the fourth ventricle in the medulla) – Basal ganglia

– Spinal Cord

–       Dorsal root ganglia

Ans. is ‘a’ i.e., Rabies 

Diseases under international surveillance (WHO)

o Rabies                                o Poliomyelitis                     o Salmonellosis                    o Louse born typhus fever

o Malaria                               o Relapsing fever                  o Human influenza

Ans. is ‘a’ i.e., Rabies; ‘b’ i.e., Brucellosis 

Based on the type of life cycle of infecting organism, zoonoses are divided into four categories : -I. Direct zoonoses

                Transmitted from an infected vertebrate host to a susceptible vertebrate host by direct contact, by contact with a fomite or by a mechanical vector.

• The agent itself undergoes little or no propagative changes and no essential developmental change during transmission.

                Example are -3 Rabies, Trichinosis, Burcellosis.

2. Cyclo – zoonoses

                Require more than one vertebrate host species, but no invertebrate host, in order to complete the developmental cycle of the agent.

                Example —> Taeniasis, echinococcosis (hydatid disease).

3. Meta-zoonoses

                Transmitted biologically by invertebrate host.

• In invertebrate host, the agent multiplies or develop.
• Examples —> Arbovirus infections (e.g., JE, KFD), plague, Schistosomiasis.

4. Sporo – zoonoses

• There is non-animal developmental site or reservoir e.g., organic matter (food), Soil and plants.

          Examples -3 Larva migrans and sonic mycoses.

Ans. is ‘c’ i.e., Rabies 

o Among the given options only rubella and rabies are viral infections and rubella is not a zoonosis.

Ans. is ‘c’ i.e., Water 

Rabies

o Rabies is primarily a zoonotic disease of warm-blooded animals, particularly carnivorous such as dogs, Cats, Jackals and wolves.

o It is transmitted to man usually by bites or licks of rabid animals.

o It is the communicable disease which is always fatal.

o Rabies is an enzootic and epizootic disease of world-wide importance.

o Geographic boundries play an important role in the distribution of rabies.

o Water appears to be the most effective natural barriers to rabies –+ So, In India, Lakshadweep and Andman & Nicobar islands are free of the disease.

o A Rabies free area has been defined as one in which no case of indigenously acquired rabies has occurred in man or any animal species for 2 years.

o Countries where rabies is not found -+ Australia, china (Taiwan), Cyprus, Iceland, Ireland, Malta, Japan, Newzealand, Britain.

Ans. B: Street virus

These viruses are enveloped and have a single stranded RNA genome with negative-sense. The genetic information is packaged as a ribonucleoprotein complex in which RNA is tightly bound by the viral nucleoprotein. The RNA genome of the virus encodes five genes whose order is highly conserved: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and the viral RNA polymerase (L).

From the point of entry, the virus is neurotropic, traveling quickly along the neural pathways into the central nervous system (CNS), and then further into other organs.

The salivary glands receive high concentrations of the virus thus allowing further transmission.

The virus recovered from naturally occurring cases of rabies is called street virus and is pathogenic for all mammals and shows a long variable incubation period (20-60 days in dogs).

Ans. is ‘a’ i.e., Rabies

Ans. is ‘d’ i.e., 100%

Rabies

Rabies is primarily a zoonotic disease of warm-blooded animals, particularly carnivorous such as dogs, Cats, Jackals and wolves.