Infectious Bovine Rhinotracheitis (IBRT)

Infectious Bovine Rhinotracheitis (IBRT) also known as Red nose, Infectious pustular vulvo vaginitis, Infectious pustular balanophosthitis and Necrotic rhinitis in animals.

Infectious Bovine Rhinotracheitis (IBRT) is an acute highly contagious viral disease of cattle characterized by high temperature, rhinitis, dyspnoea, 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.

Etiology

• Bovine herpes virus -1 (BHV-1) cause’s respiratory disease, conjunctivitis, abortion, encephalitis and other clinical form of the disease complex. Genetic analysis of various clinical isolates has found three subtypes.
• BHV1.1-Respiratory subtype.
• BHV 1.2- Genital subtype.
• BHV1.3  -Encephalitic subtype, BHV1.3 is renamed as BHV1.5.
• Rarely genital and respiratory form disease occurs together.

Epidemiology

• Occurrence-The disease was recognized in Europe, Asia, North America, Africa and Newzealand .       
• Morbidity and mortality rate are higher in feedlot cattle than dairy cattle.
• Morbidity and mortality rate in dairy cattle- 8% and 3% respectively.
• Morbidity and mortality rate in feedlot cattle-20-30% and 1% respectively.
• Case fatality rate in systemic form of infection in new born calves is almost 100%.

Host affected

• All  breeds and all age group of cattle are susceptible.

Source of infection

• Nasal exudates, coughed up droplets, genital secretion, semen, foetal fluids and tissue of infected animals.

Transmission

• Respiratory disease- through inhalation of aerosol.
• Genital disease-  through venereal transmission.

Immune mechanisms

• Immunity to the virus is complex and consists of relationship between local and systemic antibody and cell mediated immunity.
• Colostral immunity in calves present upto 4-6 months of age.

Pathogenesis

• Respiratory disease: Inhalation of virus- nasal cavity > upper respiratory tract > Rhinitis, laryngitis and tracheitis.
• Encephalitis: Inhalation of virus > nasal mucosae > trigeminal peripheral nerve > trigeminal ganglion > non suppurative encephalitis                                                                                       
• Abortion: Inhalation of virus > local mulitiplication in tonsil > systemic invasion > placenta > infection in last trimester of pregnancy > Abortion, mummification and still birth.

Clinical manifestation

Incubation period is 3-7 days for Infectious Bovine Rhinotracheitis (IBRT) in animals.

Respiratory form

• Rhinitis, tracheitis and conjunctitis (Red nose).
• Sudden onset of anorexia.
• Loud coughing.
• Fever (upto 42^o C).
• Severe hyperaemia of nasal mucosa with  numerous cluster of grayish necrotic lesion in mucous membrane of nasal septum.
• Serous nasal and ocular discharge.
• Increased salivation.
• Sometimes slight hyperexcitability may be noticed.
• Fall in milk yield.
• Increased respiratory rate, but shallow.
• Respiratory distress is evident on exercise.
• Short explosive cough is characteristic of some outbreak.

Dairy cattle

Many animals in the herd become affected within a few days; the disease is usually mild characterized by inappetence, coughing, profuse bilateral serous nasal discharge, excessive salivation, moderate fever, and moderate drop in milk production, corneal edema, conjunctivitis, profuse ocular discharge and recovery within few days.

Respiratory form (Feedlot cattle)

Illness is often more prolonged, febrile period is longer, nasal discharge becomes more profuse and purulent and convalescent period is longer. Some recovered animals may have a persistent snoring respiration.

Ocular form

Conjunctivitis is a common finding in typical ‘red nose’; one or both eyes may be affected. IBR lesions are confined to the conjunctiva and there is no lesion in cornea except diffuse edema. The conjunctiva is reddened and edematous with profuse serous ocular discharge.

Systemic form in newborn calves

• In new born calves under 10 days of age, systemic form of disease is severe and highly fatal.
• Sudden onset of anorexia, fever, excessive salivation and rhinitis, often accompanied by unilateral or bilateral conjunctivitis are common.
• Hyperaemia of oral mucous membrane, erosion of soft palate covered by tenacious mucus.
• Acute pharyngitis covered by tenacious mucopurulent exudates.
• respiratory distress.
• Bronchopneumonia, loud breath sound, crackles and wheezes associated with consolidation of lungs may be present.
• Diarrhoea and dehydration occur in some calves.

Abortive form

• Abortion in last trimester is common sequel and occurs some weeks after clinical illness or parenteral vaccination of non immune pregnant cows with MLV vaccine of bovine tissue culture origin. Retention of placenta often follows.
• The endometritis, poor conception rate and short oestrus can occur after insemination with infected bull semen.

Vulvo-vaginal form

• Frequent urination and tail elevation.
• The vulva is swollen, papules, erosions and ulcers are present on the mucosal surface.
• Mucosal ulcers may coalesce and sloughing of brown tissue may occur.
• Mucoid or mucopurulent exudates in vagina.
• Recovery usually occurs in 10-14 days.

Balanophosthitis

• Papules, erosion and ulcer present on the glans penis and preputial mucosa.

Necropsy Finding

• Acute inflammation of the larynx, trachea and bronchi.
• Profuse fibrino-purulent exudate in the upper respiratory tract in severe cases.
• Chronic ulcerative gastro-enteritis in feedlot cattle.
• Lung emphysema.
• Secondary bronchopneumonia.

 Diagnosis

• Based on clinical signs.
• Isolation of virus from nasal swab.
• PCR  assay is   a practical alternative for rapid detection of virus in clinical sample.
• Detection of antibody by ELISA, VNT and indirect immunoflourescence test.
• IgM –ELISA test is useful for diagnosis of recent infection with BHV-1.
• Micro ELISA  is being used for control program of BHV-1 infection in switzerland.

Sample collection

• Live animal-Sterile nasal swab and semen, paired sera sample and aborted foetal contents.
• Dead animal- lung.

Differential diagnosis

• Pneumonic pasteurellosis
• Bovine viral diarrhoea
• Malignant catarrhal fever
• Calf diphtheria
• Viral pneumonia of calves
• Allergic rhinitis

Systemic form of IBR in new born calves should be differentiated with pneumonia, septicaemia and toxaemia.

Treatment

• Broad spectrum antimicrobials are indicated if secondary bacterial tracheitis and pneumonia are present.
• Isolation of infected animals and monitored frequently for evidence of secondary bacterial complication and then treated accordingly.

Control

• Natural exposure
• Vaccination
• Eradication

Natural exposure

Cattle that have recovered from a natural infection with a virus are immune to further clinical disease. However natural exposure is risky because, not all animals in the herd will become infected and become immune.

Vaccination

Vaccines available for IBR are:

1. Modified live virus vaccine (MLV)
   • (a) Parenteral vaccine – abortogenic  in non immune cows.
   • (b) Intranasal vaccine- non abortogenic to pregnant animal, which is used during an outbreak.
2. Temperature sensitive BHV-1 MLV (virus multiplication restricted to the upper respiratory tract)- vaccine is efficacious and safe for use in pregnant animals.
3. Inactivated vaccine: vaccine do not cause abortion, mummification and safe for use in pregnant animals.
4. Subunit vaccine: contain major surface glycoprotein of BHV-1-stimulate protective immunity.
5. Marker vaccine: based on deletion  mutants of one or more microbial antigen, which is  used for differentiation of vaccinated from infected animals.
6. Combination or multivalent vaccine: for BHV-1, BRSV, PI-3 and BVDV.

Eradication

• Annual serological testing of the national herd.
• Restriction of trade with seropositive animals.
• First priority of eradication was given to farms with breeding animals.
• Stepwise elimination of seropositive animals.