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INFECTIOUS BOVINE RHINOTRACHEITIS (IBRT)
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Definition
- Highly infectious viral disease of cattle causing variety of clinical signs – along with upper respiratory disease like conjunctivitis, encephalitis mastitis, infectious pustular vulvo-vaginitis, balanoposthitis, abortion and systemic infection in calves caused by Bovine herpes virus type 1 (BHV–1)
Synonyms
- Infectious pustular vulvovaginitis; coital exanthema,Vesicular venereal disease, Vesicular vaginitis, Coital vesicular exanthema
Incidence
- First reported in Colorado, USA
- Also reported in India
Etiology
- Bovine herpes virus type 1 (BHV–1)
Transmission
- Nasal exudate
- Genital secretions
- Semen, foetal fluids and tissues
- Aerosol route
- Venereal transmission in genital diseases
- IBRT virus survives up to one year in frozen semen
Pathogenesis
- Virus enters through the respiratory tract , multiplies in nasal cavities and upper respiratory tract resulting in rhinitis, laryngitis and tracheitis
- Deciliation has an adverse effect on the respiratory defence mechanism
- From the nasal cavities the infection spreads to the ocular tissues through lachrymal ducts and causes conjunctivitis
- Virus also spreads through the trigeminal nerve to the brain resulting in non suppurative encephalitis
- Localisation of the virus in various tissues results in systemic lesions
- The virus is transported through the peripheral leucocytes to the placenta and foetus causing abortion
- Foetus is highly susceptible to IBR virus
Clinical signs
- Respiratory form
- Young cattle are more susceptible
- Morbidity 100%, mortality–10%
- Fever, anorexia, mucus nasal discharge
- Respiratory distress
- Mouth breathing
- Dyspnoea, coughing
- Conjunctivitis
Gross lesions
- Congestion and oedema of paranasal sinuses and mucosa of trachea
- Mucosa thickened and covered with thick mucopurulent exudate
- Stenosis of trachea due to thickeningof mucosa
- Death due to asphyxia or bronchopneumonia
Microscopic lesions
- Necrosis of respiratory tract mucosa
- With neutrophilic and mononuclear cell infiltration of sub mucosa
- Intranuclear inclusion bodies in epithelial cells
Neonatal form
- Affects very young calves
- Generalized form of infection
- Necrosis of respiratory epithelium, liver, kidney, spleen, lymphnode, oesophagus, forestomach
- Intranuclear inclusion bodies
Genital form
- Mainly female genital tract is affected
- Clinical signs occur within 24 -72 hours after coitus with an infected bull
- Reddening of vulval mucosa with dark red punctate foci; vesicles, pustules which soon form a membrane and peelin g of the membrane develop ulceration & necrosis
- Vulva swollen
- Bulls–penis and prepuce show similar lesions Healing of lesions is complete in 2 weeks but recurrence occurs
- Micrscopically, foci of necrosis of epithelium with inflammation and intranuclear inclusion bodies in epithelial cells
Abortion
- Up to 60% pregnant cows in a herd abort
- Abortion in third trimester
- Focal areas of necrosis in liver, spleen, kidney of foetus
- Advanced postmortem autolysis is a striking gross finding in aborted foetuses
- Microscopically, focal areas of necrosis in liver, spleen, kidney and lymphnodes; intranuclear inclusion bodies are found in tissues
Diagnosis
- Based on clinical signs
- Necrotizing lesions with intranuclear inclusion bodies
- Isolation and identification of virus in the nasal swabs
- Enzyme linked immunosorbant assay (ELISA), Immunofluorescence (IFT), Immunoperoxidase (IPT), electronmicrscopy (EM)
- Serological tests – ELISA, passive haemagglutination, virus neutralization test
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Participants