Rabies

From Cow
Electron microscopic view of Lyssavirus
Rabies in a cow

Rabies is a viral neurological disease of cattle seen sporadically worldwide[1].

Rabies is caused by a Lyssavirus (Rhabdovirus; ssRNA) resulting in acute, progressive encephalomyelitis that is invariably fatal[2].

Dogs, cats, foxes and other small carnivores serve as reservoir hosts[3].

Cattle become infected by oral inoculation of virus, usually via bites. Incubation periods vary from one to 12 months. Lyssaviruses travel via the peripheral nerves to the spinal cord and ascend to the brain. Virus is shed intermittently in the saliva[4].

Clinical signs

In cattle, clinical signs include ptyalism, behavioural changes (abnormal bellowing), aggression/irritability and hyperexcitability.

In terminal stages, paralysis and lateral recumbency occur prior to death[5].

Diagnosis

Clinical diagnosis is based on circumstantial evidence of neurological signs and death, supported with laboratory testing.

Immunofluorescence microscopy of fresh brain tissue is considered the gold method of diagnosis in most affected animals[6].

A differential diagnosis would include ketosis, BSE, Histophilus spp, sporadic bovine encephalomyelitis, Chlamydophila spp, Echinococcus granulosus and lead poisoning.

Treatment

Government notification is mandatory and culling of cattle herds and all other carnivores in the vicinity is usually required, followed by quarantine methods in the surrounding farms.

Prophylactic vaccine protocols are well established in small animals worldwide[7].

References

  1. Carnieli P Jr, et al (2009) Genetic characterization of Rabies virus isolated from cattle between 1997 and 2002 in an epizootic area in the state of São Paulo, Brazil. Virus Res 144(1-2):215-224
  2. Stein LT et al (2010) Immunohistochemical study of rabies virus within the central nervous system of domestic and wildlife species. Vet Pathol 47(4):630-633
  3. Johnson N et al (2008) Epidemiology of rabies in Southeast Europe. Dev Biol (Basel) 131:189-198
  4. Merck Vet Manual
  5. Favi CM et al (2008) Rabies in Chile: 1989-2005. Rev Chilena Infectol 25(2):S8-13
  6. Chhabra M et al (2007) Development and evaluation of an in vitro isolation of street rabies virus in mouse neuroblastoma cells as compared to conventional tests used for diagnosis of rabies. Indian J Med Microbiol 25(3):263-266
  7. Thiptara A et al (2011) Epidemiologic trends of rabies in domestic animals in southern Thailand, 1994-2008. Am J Trop Med Hyg 85(1):138-145