Rabies
 

Definition
Highly fatal viral disease of CNS affect all warm blooded animal producing abnormal behavior, sign of mania and paralysis of most animals it afflicts.
 

Cause
• Rhabdoviruses (Rhabdos = rod).
• Lyssavirus (Lyssa madness) one of the larger virus.
a RNA neurotropic virus
 

• Bullet shape               70          170 nm                 
• Have bilayer envelope.
• Heat labile.
• Ether sensitive.
• Inactivated by:
Formalin.
UV radiation.
Household bleach.
Hospital disinfectant.
Phenol.
Repeated freezing and thawing.
20% fresh soap solution.
2 forms of the virus are exist..
 

1- Fixed
Refers to strains adapted to secondary host for !aoratory ‘iurk and vaccine produobon-replicat well in vero cells (green african monkey kidney ce’ls, Baby hamster kidney (Bl-K 21), chick embryo fibrobiasts.
 

2- Street
Refers to strains isolated from infectea animals replicate well in suckling nouso and suckNrtg ham3te i’1n’ NB: Rhabdciruses causes: Vesicular stomatit Bovine ephemeral fever Bovine ephernera lever ike dheas
• When irritation occur it will be followed by paralysis as the stimuiated n-cells are subseuent uetiuycd but gradually ascending paralysis t ‘ aiters followed by quite severe sign of mania .Nhich oersist unti d:’
• The chv infective nature of the saliva a from passage of the virus along the olfactory nerve to bste buds rather than from The salivary glands.
• Variation in major signs (mania or paralysis) may be pend in  source of the virus.

a- Virus from vampir3 bats — paralysis.
b- Fixed virus 4 paralysis.
c- Street virus furious
- Site of infection and size of inoculum.
- Geogrophical difference, Africa — furious

- America — Paralysis
• The virus may b found in milk, in some organs and in fetuses but can not drnonstrated in the blood at any time.
** Multipilcation of the virus in the fatty tissue of the bat without invasion of the system is the base of reservaring?
 

EPIDEMIOLOG
- Tha disease infect al warm-blooded animal including man
- This disease is one of the oldest and most feared disease of animals and man where it was recognized in Egypt 2300 BC and in ancient Greece where it was described by arstotel.
- The disease is found world-wide except
* Australia never occur
* Great Britain
Japan
* Newzeal never occur
* Hawaii
* Some islands of car.bean
- There is no variation in susceptibility with age
- There is great variation in s:sceptibility with species

Fox, cotton rats, coyotes Ò Extremely susceptible
Cattle, cat, rabbit
Ò Highly 
* Dog, sheep, goat
Ò Moderately
 

SOURCE OF INFECTION
A) Domesticated animals
Dog and cat
B) Wild animals (native Fauna)
Foxes. wolves, skunk, coyotes (wild wolve like dog), vampire, insectivorous and fruit eabnq bats, mogose, squirell
 

MODE OF INFECTION
Biting by rabied animal
Contamination of open wound with saliva containing virus!
scratch

INCUBATIDN PERIOD
2 weeks — several rnonth (5- 6 m) Prodroma: animal do not et or drink, drop in mik. prduction (generalized signs).

 

CLINICAL FINDINGS
Clinical signs of rabies can be devided into three phases prodromal — excitation and paralytic
 

CATTLE
1) Paralytic form (Course 6 — 7 days)
- Knuckling of the hind fetlocks
- Swaying of the hind quarters while walking
- Deviation or flaccidity of the tail to one side
- Decrease sensation especially in hind quarters
- Tenesmus with the paralysis of anus resulting in the sucking in and blowing out of air
- Dro oling of saliva with pharyngeal paralysis
- Yawning movement (vciceless attemipts to below)
- Paralysis (animal goes down and unable to rise)
- Death usually occurs 48 h after recumbency and after total course of 6 —7 days.
- Bulls have paralysis of penis
2) Furious form (course 1 —6 days)
- Animal have tons and alret appearance
- Hypersenstive to sound and movement and attracted by them
- Violent attack of other animals or inanimate objects These attacks are badly directed
- Loud bellowing (characteristic hoarse).
- Sexual excitement, bulls sttempt to mount inanimate objects
- These severe signs continued 24 — 48 h, Then collapse suddenly in paralyzed state
 

SHEEP AND GOAT
Usually rabies occurs in number of animals
- The signs are very similar to that in cattle + vigorous wool pulling - nuscle tremor and salivaton. Excessive bleating does not occur
- Goat more aggressive with ontnuous bleating
 

HORSE ataxia apparent blindness
- Abnormal postures, sweating
- Frequent whinnying, itching at biting site sexual excitement.
- Unexplained aggressiveness and kicking — biting erected ear, chewing of foreign mat. Or own skin.
- Colic
- Lameness in one limb
- Recumbancy the next day (sternal ---- lateral) with paddling convulsion and terminal paralysis
- Muscular twtching of hind1imbs
- Sudden falling and rolling

 

DOGS

Prodromal (2 — 3 days)

- Increase sensitive to noise (sound) and light

- Marked change in behaviour

- Sullen animals   Ò Alert. friendly Amicabl aggressive and attack without provocation or become depressed and hide in dark place

- May be slight pyrexia

- Dilatation of pupils with impaired corneal reflex

- Annual self mutilate at the site of the bite

 

EXCITATIVE STAGE (one week)

- Gradually the excitement phase become predominate
- Animal become nervous, irritable and vicious
- Animal attempt to bite and attack
- Disorientation
- Far-off look in the eyes
- Spasm (and paralysis) of muscles of deglutition lead to difficulty in swallowing and drooling and frothing of saliva
- Dogs may also showed pica
- Chaiacteristic high-toned bark (laryngeal paralysis)

 

PARALYTIC PHASE
- Muscular incoordination
- Convulsions
- Generalised paralysis
- Coma and death
 

DIAGNOSIS
1- Clinical signs
2- PM finding
3- Histopathology
Rabies can be confirmed by detection of intracytoplasmic inclusion bodies in thin sections made from medulla, cerebellum and hippocampus. Negri bodies observed only in 70 — 80 % of rabied animals at the same time attempt should be made
4- Mouse inorculation test
1 part brain + 9 part saline
Ò centrifugation 2000 rpm/5 min
0.03 ml injected intracerebraly into mouse
 

Result
Convulsion
Paralysis of hind legs (after 7 days -21 days-30 days)
* We can use saliva treated with antibiotics
5) Virus isolation
The virus can isoiated from brain or saliva Homogenization in cell growth medium Centrifugation 2000 rpm/5 min.
The suspension inoculated into cell culture incubation 1 — 4 days then examined by FAT Very slow and cumbersome
6) FAT
- Tissue impression made from medulla, cerebellum and hippocomp us by light touching of freshly cut tissue withslide
Or tissue smearing by crushing of 1 -mm of tissue (brain) between 2 slide
- Fixation by aceton at —20 °C for 2 — 4 h.
- Air dried
- Staining with fluorescence iso thiocyanate (FITC) labeled monodonal rabies antioody conjugate for 30 —45 min in humid chamber

RESULT
Rabies antigen identify by characteristic apple green fluorescence that appear as dust like or as large masses.
The result of FAT is 97 — 98 % correlated with virus isolation

7) ELISA
A) Double sandwitch
B) Dot
8) RT-PCR
9)lmmunohistochernistry (ABC)

- Paraffin sections from examined tissues were cuted 4 pm and picked up from warm water in the usual way on poly-L-Lysin coated slide and dry overnight in oven 37°C
- Sections were deparaffinized and rehydrated by sequential imersionof the slides in xylene followed by graded concentraion of ethanol, then tap water
- Enobgenous tissue peroxidase activity blocked by immersion o slide in 0.5 % H2o2 in methanol for 30 min at room temp.
- Proteolytic treatment
Section + 0.25 trypsin in PBS for 60 min.
- The sections washedtimes each for 5 mm in tris PBS  

 Secticns overlaid with normal rabbit serum diluted 1: 10 in PBS for 20 min. toinhibit nonspecific binding immunoglobulin binding
- The slides were then washed 3 times in tris PBS
- The primary monoclonal mouth antibodies diluted in 1 : 100 in PBS incubated with section for 16 — 18 n. at 4°C in humid chamber
- The biotinylated secondary antibodies rabbit anti-mouse immune globulin diluted 1: 200 in PBS were applied for 30 min

 

DIFFERENTfAL DIAGNOSIS
- Acute and subacute lead poisoning Twitching of eyelids and ears (twitching of facial muscles) blindness - grinding of the teath
- Lactation tetny and avitarninosis A More convulsions
- Polioencephalomalacia Blindness, nystagmus No salivation, no bawling, No tenesmus
- Listeriosis Circling — facial nerve paralysis
- Enterotoxaemia lambs
- Pregnancy toxaemia Pregnant ewes - ketonuric
- Louping ill Transmitted by insects — seasonal occurrence

 

TREATMENT
- No treatment should be attempted after clinical signs
 

VACCINE
1- Original pasteur vaccine Fixed virus in spinal cord of rabbit Ò drying with KDH
2- Hogyes vaccine (Hungaian) Fxed virus in spinal curd of rabbit
Ò emulsified Ò dilution 1/5000
3- Harris vaccine Fixed virus in spinal cord of rabbi
Ò frozen with Co2 snow Ò ground tc powder Ò suspended in saline
4-Flury vaccine (Avianized vaccine) Made from strain called flury (Isolated from brain of child called flury)
Fixed by serial passage (intracerebral) in day did chick attenuated cy serial passage in embryonated chicken
LEP   40-50
HEP   178
No post vaccinal reaction