Pseudorabies
Syn: Aujeszky’s disease or Infectious Bulbar Paralysis or Mad Itch
- It is a viral disease primarily affecting pigs but also occurs in other species, i.e. cattle and buffaloes.
- In young pigs, it produces fatal encephalitis and in other species, it produces marked local pruritis.
Etiology
- Herpes virus
- Virus is sensitive to ether and chloroform, can be inactivated by trypsin, chymotrypsin, UV-light
Epidemiology
- Disease was first recorded by Aujeszky in 1902 from infected ox.
- Disease has been reported from Central and Eastern Europe comprising Yugoslavia, Romania, Poland, Italy
- In 1939, it was first reported in UK.
- Disease was first recognized among cattle in Denmark in 1965
- Disease has been reported from India by Bhattacharya in 1973
Transmission
- Through bite, abrasion or injury- Natural route
- Through inhalation or aerosol way of transmission
- Transplacental transmission
- Ingestion of contaminated food and water.
Pathogenesis
- Following oronasal infection of virus, virus enters respiratory system
- Virus first replicates in epithelium of nasopharynx and tonsils.
- Virus then spreads to region of lymph node via lymphatics
- Virus spread to olfactory, glossopharyngeal, and trigeminal nerve and reaches to CNS via axons of these nerves
- Virus then dissipates from CNS on 8th day after infection. Virus from local abrasion enters peripheral nervous system and causes pruritus.
Clinical Signs
- Pigs:
- Anorexia, vomiting, diarrhoea
- Fever upto 107°F
- Muscles spasm, muscle tremor, paddling movement
- Snoring sound during respiration
- Tilting of head, nystagmus, ocular discharge, convulsion
- Incoordination develops in posterior limb which force animal to move sideways
- Blindness and encephalitis
- Significant weight loss and poor growth rate
- Coughing, nervous symptoms and reproductive failure
- Abortion in pregnant sows in late pregnancy
- Mummification, maceration of fetus, still born or weak piglet in late pregnancy
- Cattle and buffalo:
- Incubation period of 3-6 days
- Fever 106-107°F following infection
- Intense, intolerant pruritis in nose, eye, lower jaw, chest, limbs, udder, flanks and anal region, ear
- Bellowing loudly due to pruritis
- Profuse salivation and sweating
- Animals lick or rub affected part of body leading to depilation, excoriation, hemorrhages and mutilation of skin
- Animal refuse to eat due to intense itching and drop in milk production
- Animals becomes recumbent and unable to rise due to paralysis
- Neurological signs; excitement, restlessness, bellowing, rolling up and down, stumping on ground, aimless staggering, aggressiveness, circling in either direction.
PM Findings
- Congestion of meninges, cerebrum, cerebellum
- Edema, hemorrhage and necrosis of lungs
- Necrotic placentitis in case of aborted placenta
- Necrotic tonsils on nasal septum
- Ecchymotic and petechial hemorrhage in large intestine, bladder and kidney
- Hemorrhage under endocardium and hydropericardium in case of cattle
- Depilation, bruises and laceration on skin due to rubbing.
Diagnosis
- Based on history and clincal findings
- Based on PM findings
- Animal inoculation test; suspected materials is inoculated on rabbit or baby hamster. Animals shows intense pruritis and death within 8-10 days
- Isolation and identification of virus
- Serum virus neutralization test
- ELISA, PCR
Differential Diagnosis
i. Rabies:
- Profuse salivation, altered behavior
- Dropped jaw
ii. Listeriosis:
- It is caused by bacteria Listeria monocytogenes
- Facial paralysis, circling
- Abortion in pregnant cattle
iii. Polyencephalomalacia:
- History of carbohydrate engorgement
- No rise of temperature
- Respond to thiamine therapy
iv. Poisoning:
- History of poisoning
- No fever and tympany
Treatment and Control:
- No effective treatment. Hyperimmune serum @5ml through SC route in sucking piglets.
- Avoid rodent population in farm.
- Isolation of pig from other species
- Avoidance of uncooked offals of pig to dog and cat.
- Vaccination of pigs; gene-deleted modified live vaccine may be tried.