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Viral Disease - Infectious Bovine Rhinotracheitis

Synonyms

Infectious pustular vulvovaginitis, viral bovine rhinotracheitis, Red nose, Necrotic rhinitis

Etiology

Caused by Bovine herpes virus type 1 (BHV-1)

Introduction

It is an acute highly contagious viral disease of cattle characterized by high temperature, rhinitis, dyspnea, abortion, meningoencephalitis, keratoconjunctivitis and pustular vulvovaginitis.

Dairy and beef cattle are equally susceptible. Besides cattle, the disease also reported in goat, swine and water buffaloes. The disease is widely prevalent in all parts of the world.

Cattle of all ages are affected.

The virus is transmitted through infected feed and water.

The virus can spread through ocular, nasal and reproductive secretion and excretion of infected cattle.

Droplet infection is the important way of transmission.

Clinical Manifestations

The clinical signs have been grouped as

  • » Respiratory form
  • » Vulvo-vaginal form
  • » Ocular form
  • » Encephalomyelitic form
  • » Abortive form

Respiratory form

This form is characterized by mild to severe rise of temperature, depression of appetite, acceleration of respiration and dyspnea.

The nasal discharges are initially serous which later turn to mucopurulent. Whole of the upper respiratory tract show hyperemia, edema along with mucopurulent exudation causing dyspnea.

Affected cattle may exhibit open mouth breathing in severe cases. Animal may show signs of bronchitis and pneumonitis.

The nasal mucosa is severely congested hence the disease is named as "Red nose".

The recovered cattle may remain as carrier and thus shed the virus for a considerable period.

Vulvo-vaginal form

This form is characterized by sharp fall in milk yield and appearance of erythematous and pustular lesions on the vulvar and vaginal mucosa.

There is swelling of vulva and frequent urination. There may be mucopurulent discharge from vulva and vagina.

Animal is unable to put its tail in normal position after urination due to pain. The virus produces pustular balanoposthitis in bull.

The semen of the affected bull become contaminated and thus pose problem in natural or artificial breeding

Ocular 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 ocular discharges may be noted without respiratory involvement.

The ocular discharges vary from serous to purulent.

Petechial hemorrhages 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 to death.

The signs of encephalomyelitis comprise of high rise of temperature, incoordination, tremor, circling, falling, coma and death.

Death ensures within 4 days following appearance of neurological signs.

Abortive form

The pregnant cattle may abort following infection. The abortion may supervene as "abortion storm".

Foetus died at 4 months of gestation and expelled. Foetus is autolysed in most cases.

Lesions

In uncomplicated IBR infections, most lesions are restricted to the upper respiratory tract and trachea.

Petechial to ecchymotic hemorrhages may be found in the mucous membranes of the nasal cavity and the paranasal sinuses.

Focal areas of necrosis develop in the nose, pharynx, larynx, and trachea.

The lesions may coalesce to form plaques.

The sinuses are often filled with a serous or serofibrinous exudate.

As the disease progresses, the pharynx becomes covered with a serofibrinous exudate, and blood-tinged fluid may be found in the trachea.

The pharyngeal and pulmonary lymph nodes may be acutely swollen and hemorrhagic.

The tracheitis may extend into the bronchi and bronchioles; when this occurs, epithelium is sloughed in the airways.

Samples to be collected

Live animals- nasal swabs or genital swabs or conjunctival swabs during the acute phase of infection, aborted materials, tissue samples from the fetal liver, brain, and spleen, semen, placenta, uterine mucus and serum

Dead animals- Lymph nodes, liver, lungs, brain, aborted foetal liver, brain and spleen

Diagnosis

Uncomplicated BHV-1 infections can be diagnosed based on the characteristic signs and lesions.

However, because the severity of disease can vary, it is best to differentiate BHV-1 from other viral infections by viral isolation.

Samples should be taken early in the disease, and a diagnosis should be possible in 2-3 days.

Gross and microscopic lesions detected shortly after death may help to establish a diagnosis.

Diagnosed by identification of virus and serological test

Differential diagnosis

All diseases associated with bovine respiratory tract disease: pneumonic pasteurella, viral interstitial pneumonia, Haemophilus pleuro-pneumoniae, allergic rhinitis

Treatment

Antimicrobials for secondary bacterial infections

Prevention and Control

No successful treatment. Antibiotics given to avoid or prevent secondary bacterial complications

Best way to control this disease is to prevent contact between infected animals and sero negative animals.

Since the virus is latent in seropositive animals, they should be identified and eliminate them from the herd

Good hygiene, management and isolation do not seem control the disease adequately

Most control efforts are based on vaccination. The best practice is to vaccinate females kept for breeding once or twice prior to their first breeding with modified live virus vaccines or inactivated vaccine. Age of vaccination - calves after 5 months of age. Immunity develops within 10-14 days.

Live vaccines induce a relatively rapid immune response comprising both humoral and cell-mediated responses, including mucosal immunity that resembles a natural infection.

Live attenuated vaccine administered through intramuscular or intranasal route, but modified live virus (MLV) vaccines contraindicated in pregnant cows because MLV have the property of abortigenicity. In outbreaks- intranasal route selected. Vaccine may be instilled into one or two nostrils.

Killed vaccines are administered by intramuscular route. Primary and secondary inoculation should be given four weeks apart followed by booster inoculations annually.

Vaccination of young breeding herd replacements using modified live virus or inactivated virus vaccines. Subunit and marker vaccines becoming available are superior to conventional vaccines. Some countries eradicating infection by identifying and eliminating seropositive animals

The current strategies for control are natural exposure, biosecurity, vaccination, or eradication of the virus from a herd or even the cattle population of a country.

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