Rabies
Disease
of all warm-blooded animals
Etiology:
·
Rabdoviridae/Genus/Lysa
Virus
Clinical Importance:
·
Zoonotic and
acute type of encephalomyelitis
Characteristics of Virus:
·
Bullet shaped
·
RNA
·
Capsid Proteins
·
Surface
glycopeptide serve as a neurotoxin for this virus, its helps to enter virus in
nerves due to presence of surface glycopeptide receptor on nerves (Lipid
receptors)
Transmission:
· Always through
bite of infected or carrier animal
· Mainly dogs,
wild carnivores particularly foxes, racoons are important while rodents (rate
bite in KPK) and bats (not common in our area, Important in America and African
continents)
· Saliva is rich
in rabies virus
· Its present in
world wide but countries are considered rabies free like Australia, New-zeland,
Norway, England and Sweden.
Pathogenesis:
·
Virus enters
through bite (Saliva inject virus)
·
Initial
replication occurs in local tissues
·
Virus reaches at
neuromuscular junction
· Enter into
peripheral nerves, from nerves travel in axons via retrograde manner and then
reach spinal cord and brain affected (Specially forebrain), then moves
centrifugally through trigeminal nerve (Cranial Nerve) to salivary gland and
comes in saliva. (Rabies also occur through wound, where dog lick, cats pawing
on skin and has licking habit, In USA cats are major carrier)
· Bats which cause
rabies not in Pakistan, vampire virus responsible transmission of this disease
in nerves.
Incubation period vary depends upon;
·
Distance from
site of bite
·
Intensity of innervation
·
Amount of virus
in inoculum
· Speed of rabies
in nerves is 100mm/day, if area more nervated then speed is 400mm/day.
·
No aerosol transmission
· Rabies 2nd
name is death because when virus enter in nerves then there is no recovery
· Negri bodies
formed in brain
- Before appearing nerves signs, virus began to shed from saliva
Clinical Findings:
·
Clinically
course 3-10 days
·
Incubation
period is 4-24 weeks in dogs, 2-6 weeks in cats, years in human (up to 17
years)
·
Acute behavioral
changes
·
Sudden onset of
anorexia (esophageal obstruction leads to drooling of saliva)
·
Nervousness
·
Hyperexcitability
·
Changes in temperament
·
All above signs
in esophageal shocking but not enter mouth of animal
Phases:
1. Prodromal
2. Dumb/Paralytic
3. Furious
Prodromal Phase:
·
Nervousness
·
Anxiety
·
Variable fever
·
Erratic behavior
·
Loneliness and solitude
·
Corneal and palpebral
reflexes are very slow
·
Pupillary
dilation
· Licking at site
of wound (If excessive chewing either self-mutilation in rabies)
Furious Form:
·
Vigor in
movement and forebrain effected
·
Incubation
period is 2-4 days
·
Restlessness
·
Irritated behavior
- Include
auditory and visual response
Photophobia:
·
Hyperexcitation
·
Barking at inanimate
objects and pica like behavior
·
Muscular
incoordination
·
Seizure and
death
Paralytic/dumb form:
·
Incubation
period is 2-4 days
·
Whole nervous
system involved
· Progressive
motor lower nerve paralysis (ascending paralysis). It starts where bite, limbs and
head paralysis
·
Laryngeal
paralysis which leads to horror sounds
·
Dyspnea due to
laryngealparalysis
·
Change in bark,
hoarse sound due to laryngealparalysis
·
Pharyngeal
paralysis leading to hypersalivation and dysphagia
·
Lockjaw
·
Masticatory
paralysis or dropped jaw
·
Paralysis of
respiratory muscles and cause comma and death
· In cattle
there is frequent urination and bellowing which is confused with estrous. In
estrous not continuous bellowing, in paralysis continuously and sounds heavy
Diagnosis:
·
Case history
·
Stole test in
which Fluorescent Ab technique is used (standard test)
·
In cats there is
hyperexcitation and no carrier stage
Treatment:
·
No treatment,
prophylactic vaccine, canvac, Rabisin and hexadoy
·
First vaccine at
day zero- post exposure
·
If mother
vaccinated, then 6th week pup
·
At 4 weeks age,
first deworming then first shot after 3 weeks, 2nd shot. 6, 9, 12th and15th
week then annual booster which depends on manufacturer
·
3 weeks 3
months, annual+ then 3 years in book
·
Serological titer
does not show complete protection
Post exposure or of vaccinated:
·
Day zero 1 ml s/c
·
Day 7 1ml s/c
In Non-vaccinated:
·
Zero-day 1ml S.c
·
7-day 1ml S.c
·
14-day 1ml S.c
·
21-day 1ml S.c
·
28-day 1ml S.c
·
In buffalo: 4ml,
2cc IM, 2cc s/c, 7, 14, 21 days 3ml each
·
In horse: 3ml
initially and then 2,2 ml
· IGs and vaccine
must be given, after exposure 2-8 weeks disease disappear
· In vaccine 3 weeks
takes for Abs, so no immediate treatment; so, IGs given but not available so
keep it under observation. If behavioral abnormality then euthanizes it
immediately
·
In humans: 5
injections, only 18% chances of death if vaccinated
·
In donkey, if
dog bite then rabies occurs
