Zoonotic Disease - Rabies

1. Rabies
- SHREYA PAVASKAR

2. Definition
 Rabies (hydrophobia) is an acute highly fatal viral disease of CNS caused
by Lyssavirus type-1.
 Zoonotic disease of warm blooded animals particularly carnivorous.
 Classical hydrophobia is clinically characterized by a long and variable
incubation period, a short period of illness due encephalomyelitis ending
in death despite intensive care.
 Only communicable disease that is ALWAYS fatal.

3. Agent factors
 Agent – Lyssavirus type 1[family-rhabdoviridae].
Virus is excreted in saliva of infected animals.
STREET VIRUS – virus recovered from naturally occurring cases.
pathogenic to all mammals , 20-60 incubation period in dogs.
FIXED VIRUS – One that has short, fixed and reproducible incubation period (4-6
days) when injected intracerebrally into suitable animals
Doesn’t form Negri Bodies ; no longer multiplies in neural tissues ; used in prep
of anti-rabies vaccine
 Source – Saliva of rabid animals

4. Host factors
 All warm blooded animals are susceptible.
 Risk of rabies – Lab staff workers working with rabies virus, veterinarians, dog
handlers, hunters and field naturalists.
Mode of transmission
 Deep bite or scratch by an infected animal.
 Direct contact of infectious material with human mucosa or fresh skin wounds.
Human to human transmission is theoretical.
 Inhalation of virus containing aerosol or via transplantation of infected organ –
Rare.
 Ingestion of raw meat – Not a source.
Incubation period
 Highly variable , commonly 1 – 3 months after exposure ( 7 days to years )

5. Pathogenesis

6. Rabies in man
 Prodromal signs – Headache, malaise, sore throat, slight fever (3-4 days)
Specific sign – Pain or tingling at site of bite (80%)
 Followed by – widespread excitation and stimulation of NS usually in order,
sensory motor sympathetic mental system.
 Intolerant to noise, bright light or cold draught of air, increased reflexes, muscle
spasms, dilatation of pupil , increases perspiration, lacrimation.
 Mental changes – fear of death, anger, irritability and depression.
 Progressively aggravated, swallowing becomes difficult, sight or sound of water
provokes spasm ( absent in animals ) ( HYDROPHOBIA – Pathognomic sign )
 Duration of illness – 2-3 days ( 5-6 days exceptional cases)
 Patient dies adruptly by convulsions or pass to paralysis or coma

7.  DIAGNOSIS – Clinical diagnosis ( History & signs and symptoms )
Antigen detection by immunofluorescence or virus isolation from saliva or other
secretions.
 Treatment – NO SPECIFIC TREATMENT ( Case Management )
1. Isolation of patient
2. Sedatives to relieve anxiety and pain – repeated doses of Morphia in doses
30 – 45 mg.
3. Muscle relaxants
4. Hydration and Diuresis
5. Respiratory and Cardiac support
6. Protection of people in contact from secretions of the patient.

8. Prevention of human rabies
POST EXPOSURE PROPHYLAXIS – Neutralize virus before entering NS
 General consideration – Consider medical emergency
Irrespective of wound class, combined administration of single dose immunoglobulin if
indicated with full vaccine course + local wound treatment – Best specific prophylactic
treatment
 Local wound treatment – To wounds and scratches
To remove virus from inoculation site
CLEANSING – Immediate flushing and washing of wounds
CHEMICAL TREATMENT – Residue should be inactivated by viricidal agents either alcohol
( 400-700 ml ), tincture or 0.01% aqueous solution of iodine or povidine iodine.
SUTURING – applied if necessary only after 24-48 hours with minimal stitches
ANTI-BIOTICS AND ANTI TETANUS APPLICATION

10.  Vaccination of post exposure prophylaxis– Intramuscular administration
 INTRAMUSCULAR -1/0.5 ml into deltoid (or anterolateral in thigh < 2yr ) with
category 2 or 3 exposure.
INTRADERMAL ADMINISTRATION – 2+2+2+2 <2 VIALS , 4 visits , Days – 0,3,7,28

11.  INTRADERMAL ADMINISTRATION – 2- site regimen
 POST EXPOSURE FOR PREVIOUSLY VACCINATED - 1 dose intramuscularly or a
CCV delivered intradermally on 0 and 3 is sufficient.
 Immunocompromised pt – Complete dose and wound care, check for
additional dose requirement.

12. Rabies immunoglobulin
 Passive immunization only once , asap ( not beyond 7th day )
 20 IU/kg bodyweight, equine immunoglobulin – 40 IU/kg
 Should be in or around wound, remaining at distant site
Pre- exposure prophylaxis (PrEP)
IM doses of 1ml or 0.5 ml depending on vaccine type or ID administration of
0.1ml per site per day on 0, 7 and 21/28 days.
Periodic booster ose for extra dose only if antibody titre falls below 0.5 IU/ml.
Nervous tissue vaccines cause severe effects.

13. Rabies in dogs
 Dog rabies control is a key
 Incubation period- 3-8 weeks (short as 10 days or as long as year)
 2 FORMS – Furious and dumb
 Furious rabies – Typical “mad dog” syndrome characterized by
CHANGE IN BEHAVIOUR – aggressive, bites without provocation and unusual
things.
RUNNING AMUCK – wander aimlessly biting others.
CHANGE IN VOICE – hoarseness or unable to bark
EXCESSIVE SALIVATION AND FOAMING
PARALYTIC STAGE
 Dumb rabies – predominantly paralytic
Withdraws itself from being seen or disturbed. Lapses to a stage of sleepiness
and dies in 3 days.

14.  Lab diagnosis – head cut off and sent to laboratory
Tests – Fluroscent antibody test, microscopic examination, mouse inoculation test,
corneal test.
 IMMUNIZATION OF DOGS – primary immunization at 3 – 4 month age and
booster doses regularly
1 – BPL inactivated nervous tissue vaccine ( single dose ) - 5ml dogs , 3ml cats.
Revaccination is advised after 6 months .
2 – Modified live virus vaccine – 3ml single injection and boosters every 3 years.
 CONTROL OF URBAN RABIES - Registration and licensing of all domestic dogs ,
restraint of dogs in public places, immediate destruction of dogs and cats biten
by rabid animals, quarantine for about 6 months of imported dogs, health
education of people regarding the care of dogs and prevention of rabies.
 ORAL vaccines – Under development.