ZOONOSES

ZOONOTIC DISEASES IN INDIA:RABIES

April 27, 2022

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ZOONOTIC DISEASES IN INDIA:RABIES

Introduction

Zoonoses are those disease and infections which are transmitted between vertebrates animal and man .Zoonoses is an international and epidemic problem .

Abstract

One health program
Common zoonotic disease
Rabies
Etiology
Host
Transmission
Pathogenesis
Clinical symptoms in man and animal
Diagnosis
Prevention and control

One health program

“One health is a interdependenceof human, animals and environmental health.” One health is a collaborative ,multisectoral and transdisciplinary approach working at a local, regional,national and global level with the goal of achieving the interconnection between people, animal, plants and their environments.

One health issues are implemented to effectively control the threats which are shared by people, animal and the environments.

One health issues include zoonotic diseases,anti microbialresistance,food safety and food security, vector borne diseases,environmental contamination, and others health threat shared by people ,animal,and the environment.

Common zoonotic diseases

Bacterial zoonoses: Anthrax ,Brucellosis,Plague,Leptospirosis,Salmonellosis.
Viral zoonoses: Rabies,Kyasanure Forest disease (KFD),Yellow fever,Influenza
Rickettsialzoonoses:typhus ,Q fever

Some protozoal ,fungal and parasitic diseases are commonly occurring zoonotic diseases

Rabies –Zoonotic disease

Rabies is acute viral encephalitis of all warm blooded animal characterised by altered behaviour, aggressiveness, progressive paralysis and in most cases death also occur. It is OIE List A disease. Rabies is an important zoonotic infection to cause 35000 to 60000 human death worldwide annually .Rabies occurs in all continents with the exception of Australia and Antarctica.

Etiology

Family: Rhapdoviridae

Genus:Lyssa virus

Species: Rabies virus

Physiochemical property of virus

It is readily inactivated by soap, sunlight ,detergent , 40 -70 % alcohol. The virus able to agglutinate Goose RBC at PH 6.2.persists for month in infected nervous tissue.

Host

Reservoir host: Dog, Bat

Dead end host: Human (doesn’t play a any role in its spread to any other host)Foxes ,racoons, coyotes, cattle, pig ,sheep and goat, horse are also susceptible.

Transmission

Rabies virus is predominantly Neurotropic and reaches the saliva in high titre. Transmission mainly by the bite or scratch of rabid animal. aerosol transmission also reported in a person who is working in bat caves.

Pathogenesis

In body rabies virus transmitted only through nervous route not by haematogenous route. course of infection depends upon the virulence ,invasiveness and concentration of virus ,site of bite, amount of nervous tissue near the site of wound area.

Bite

Deliver the virus deep into the striated muscle and replicates in myocytes

Invade the PNSand reaches the CNS via centripetal passive movement

Reaches the limbic system of brain and replicate in neocortex

Replicates extensively (Furious form)( Dumb form )

Spread to other organ( salivary gland ,adrenal cortex , pancreas) from CNS by centrifugal movement via PNS

Virusreaches high titre in saliva

Clinical signs in Human

1^st symptom to appear may be pain and tingling in affected limb
Hydrophobia( due to pharyngeal paralysis , a violent jerky contraction of diaphragm and accessory muscles of inspiration ,so the patient unable to swallow any food and water because of pain) is pathognomonic for rabies
Photophobia, aggressive behaviour also noticed in some cases.

Clinical signs in dog

Prodromal phase: last for 1^st 3 days and is seen as a change in temperament ,aimless snapping and barking at imaginary objects.
Furious form (excitative form): last for 3-7 days .Animal become restless, aggressive ,indiscriminate biting (Mad dog syndrome). Hydrophobia not seen in animals, excessive salivation, hyperaesthesia, laryngeal muscleparalysis , convulsive seizure ,coma and respiratory arrest with death occurring 2to 14 days after onset of symptoms.
Dumb Form (Paralytic form ): lower motor neuron paralysis ,hide inside any bed, anorexia, dropped jaw condition ,cranial nerve paralysis, fever, animal shows docile behaviour.

Clinical signs in cattle

Knuckling of the hind fetlocks, swaying of the hindquarters while walking , decreasedsensaton over the hind quarter, violent attacking with loud and coarse bellowing ,aggressive,alert,salivation.

Diagnosis

Based on symptoms and lesion
- Presence of intracytoplasmic inclusion (Negribody) in neuron in the hippocampus (dog) and purkinje cells in the cerebellum (cattle).
Clinical material
- Live animal: saliva ,corneal smear, skin biopsy ,hair follicle.
- Dead animal: CSF, whole carcass, brain .
Laboratory test
- Negribody demonstration by seller’s method (for unfixed section) or Mann’s method (fixed section ).( Magenta colour round to oval shaped intracytoplasmic inclusion body)
- Gold standard test: Fluorescent antibody technique(FAT)
Viral isolation : virus can be isolated by human diploid cell line,BHK21,vero cell line or by embyonated eggs by inoculating virus in yolk sac route or by lab animal (mouse)

Prevention and control

Epidemiological surveillance Mass vaccination : purified duck embryo vaccine in this low egg passaged vaccine (40 to 50 passages ) for animal , High egg passaged vaccine (180 passages ) for Human to effectively control the disease. Human diploid cell culture vaccine (pitman moorestrain ) also used .vaccination schedule should be 0,3,7,14,28 days later. For wild animal oral pellet vaccines are available.
Dog population management and community participation

Treatment

Pre exposure prophylaxis

Person at risk such as veterinarians, lab workers , animal handlers, wildlife officers ,travellers from rabies free area to rabies infected area should be 3 full IM dose tissue culture vaccine given on day 0,7,28 or 0,28,56 followed by booster at one year and then a booster every 3 year .

Post exposure prophylaxis

In case of animal bites, dog and cat in endemic area must kept in observation for 10 -14 days .

Wound Treatment
- Site of bite should be washed with water or soap
Passive immunisation by rabies immunoglobulin
- Equine or Human rabies immunoglobulin should be instilled around the wound area.
Active immunisation by Antirabies vaccine.