Synonyms.      Viral bovine rhinotracheitis, I.B.R,

Red nose; Necrotic rhinitis

 It is an acute highly contagious viral disease of cattle characterized by high temperature, rhinitis, dyspnoea, abortion, meningo encephalitis, kerato conjunctivitis and pustular vulvovaginitis.

ETIOLOGY

Classification of the causative agent

The disease is caused by bovine herpes virus. The virus is morphologically indistinguishable from other herpes virus group.

Resistance to physical and chemical action

The virus is stable at pH 6.9 and can remain alive for a long-period but is susceptible to lower pH, ether, acetone and alcohol.

Susceptible hosts

  • Cattle of all ages are affected.
  • Besides, cattle, the disease have been traced in goat, swine and water buffalo.
  • The disease has also been identified in wild ruminants. Wild animals remain as reservoir of infection.

Mode of transmission

  • The virus is usually transmitted through infected feed and water.
  • The virus can be spread through ocular, nasal and reproductive secretion and excretion of the infected cattle ( droplet infection)
  • Venereal transmission and transmission through semen via artificial insemination is possible.

Sources of virus

Tears, nasal discharge, coughed secretions, and all secretions and excretions of incubating and sick animals. Bulls may transmit the infection-especially when the bull is in carrier stage.

Predisposing Factors

  • Anti body deficient cularsi fed calves.
  • Treatment with drugs that contribute to immuno-deficiency.
  • Transportation stress
  • Stress during parturition.
  • Parasitic infestations. Eg. Dictyocaulus cularsi
  • Nutritional defiency. Eg. Selenium, Zinc

The disease is widely prevalent in all parts of the cattle in the world .In India, the disease has been recorded from Uttar Pradesh , Kerala,, Gujrat Tamilnadu;, Orissa, AndhraPradesh  and Karnataka.

Pathogenesis

The virus multiplies in the upper respiratory tract and causes inflammatory changes like rhinitis, laryngitis, and tracheitis. Tracheal damage leads to marked depletion of tracheal microvilli  The virus may produce pneumonic changes which may lead to fatality. Lesions may extend to eyes from nasal tract through nasolacrymal duct and may give rise to conjunctivitis and vascularization of the cornea. The virus may enter the brain tissues from nasal mucosa via trigeminal nerves and produce meningo encephalitis. The virus may produce changes in the placenta and foetus and cause abortion. On certain occasions the virus may cause systemic form of the disease with high mortality rate in young calves.

Clinical findings

The clinical signs may vary widely. The clinical signs have been grouped as:

  • Respiratory from
  • Vulvo-vaginal form
  • Occular form
  • Encephalomyelitic form affecting the central nervous system. .
  • Abortive form

Respiratory form.

This form is characterized by mild to severe rise of temperature, depression of appetite, acceleration of respiration and dyspnoea. The nasal discharges are initially serous which later on turn to mucopurulent. Whole of the upper respiratory tract mucosa like pharynx, larynx may show hyperaemia, oedema along with mucopurlent exudation causing dyspnoea. Necrotic plaque may appear on the nasal bones. Animal may exhibit open mouth breathing in severe cases. The mortality rate is comparatively less unless there is super imposed bacterial or viral infection. Animal may show signs of bronchitis and pneumonitis. The disease is more prevalent in feed lot cattle. Due to red appearance of the nasal mucosa, the disease is termed as red nose. The recovered animal may remain as carrier and thus shed the virus for a considerable period. .

Vulvo-vaginal form.

This form is characterized by sharp fall in milkyield and appearance of erythematous and pustular lesions on the vulvar and vaginal mucosa. Vulva may remain swollen and animal may urinate at frequent intervals. There may be muco-purulent discharge from vulva and vagina. Animal is unable to put its tail in normal position following urination due to pain. The virus may produce pustular balanoposthitis in bull. The semen of the affected bull become contaminated and thus pose problem in natural or artificial breeding.
Occular form.

This form may appear along with respiratory form. There is inflammation of the conjunctiva in addition to respiratory changes. But, in some occasions severe conjunctivitis and cular discharge may be noted without respiratory involvement. The cular discharge vary from serous to purulent. Petechial haemorrhage may be noted on the conjunctiva and sometime corneal opacity may appear as main attribute of the disease

Encephalomyelitic form.

The   virus   may   produce   severe encephalomyelitis syndrome in calf terminating in death. The signs of encephalomyelitis comprise of high rise of temperature, incoordination, tremor, circling, falling, coma and death. Death ensues within 4 days following appearance of neurological disorders.

Abortive form.

The pregnant cattle may abort following infection. The abortion may supervene as “abortion storm.” Foetus die at about 4 months of gestation and the foetus is expelled in 1-7 day. Foetus is autolysed in most cases

Lesions

Respiratory system.

White necrotic lesions are noted on the nostrils and muzzle. Due to considerable erosion of the nasal mucosa, the name red nose has been given Degenerative and necrotic changes are noted on the nasal passage, paranasal sinuses, pharynx, larynx and trachea. Lungs show the signs of emphysema and pneumonia.

Reproductive system.

Pustular lesions are noted on the mucosa of vulva and vagina. Foetus may undergo mummification, necrosis and autolysis. Necrotic lesions may appear in the liver and spleen of the foetus

Central nervous system.

Lesions are noted on the cerebral cortex.

Diagnosis

Differential Diagnosis

Pasteurellosis

  • Rinderpest
  • Malignant catarrah
  • Bovine viral culars
  • Rabies
  • Pseudo rabies
  • Parainfluenza
  • Verminous pneumonia
  •  CBPP

Lab: diagnosis.

  • ELISA TEST
  • Serum neutralization test
  • Fluorescent antibody technique using liver and spleen of the foetus
  • Virus isolation

Treatment.

There is no fruitful treatment. Superimposed bacterial infection can be checked by broad spectrum antibiotic or sulphonamide. Ancillary treatment includes restoration of fluid and electrolyte balance and provision of adequate ration and shelter. Hyper immune serum may be tried.

Control

Strict isolation of the affected animals

Vaccinations available.