18. Infectious bovine rhinotracheitis (aetiology, epidemiology, pathogenesis, clinical signs, post mortem lesions).

Question 1

Notifiable, History and causative agent?

Answer 1

Infectious bovine rhinotracheitis ʹ IBR

_*NOTIFIABLE*_

• Febrile illness of the cattle with general signs, nasal discharge, conjunctivitis, respiratory
• inflammations, encephalitis, abortion and inflammation of the genital mucosae
• (99% of cases: respiratory signs)
• Respiratory form is most frequent and need to be careful of

History:

• 1954 USA (IBR),
• 1958 (IPV),
• encephalitis (1962),
• abortion (1964)

Causative agent: (Alphaherpesvirinae)

• Bovine herpesvirus 1 and 5 (BHV-1, -5)
• Differences in tissue tropism (IPV, IBP)
• Differences in virulence: from mild - severe
• Can infect other ruminants too

Question 2

Occurrence?

Answer 2

Occurrence:

• worldwide,
• mainly in large cattle farms,
• eradication programs in EU

Question 3

Epizoothiology?

Answer 3

Epizoothiology:

• Introduction with (latently) infected cattle or with semen, contact, airborne spread within herd ʹ
• droplet infection
• bulls may shed through semen for months without signs
• relatively slow spreading, convalescent animals are long-term carrier
• respiratory and genital forms are rarely occurring together
• conjunctivitis, abortion, and encephalitis is usually associated with respiratory form

Question 4

Pathogenesis?

Answer 4

Pathogenesis:

• airborne infection
• multiplication in respiratory mucosa
• inflammation
• viremia
• encephalitis in calves, abortion in cows
• Ascending infections from nose, near the nerves (calf encephalitis)
• (All viral-infected encephalitis = lymphocytic encephalitis)
• Genital form: mucosal epithelia degeneration and inflammation, nodules

Question 5

Clinical signs?

Answer 5

Clinical signs:

• 2 - 5 days of incubation
• 1-6 month old calves: fever, respiratory signs (sneezing, coughing, nasal discharge, conjunctivitis)
• Bovine respiratory disease complex
• Lack appetite, polypnea, coughing, nasal discharge, (diarrhoea)
• In colostrum-protected calves from 6-8 weeks of age, in unprotected even at 1-2 weeks of age (+liver damage)
• Over 6 month of age: respiratory + red nose disease and even necrotic membranes
• Conjunctivitis, blepharitis
• 20-50% morbidity, <5% mortality (if with BCRDC: losses will be higher)
• Simultaneous bacterial infections complicate the disease
• Encephalitis: usually under 5 months of age - lameness, tremor, opisthotonus, death on day 5-7
• Abortion: sporadic, mainly in heifers, in acute stage or weekslater
• Genital form: vulvovaginitis and balanopostitis
• Benign inflammation of repro tract mucosa
• Spread via mating
• Mild fever, vulval- and preputial edema, inflammation
• Greyish/yellowish nodules merge, open up - erosions
• Viscous discharge from vagina
• Acute stage: no fertilization, decrease fertilization index
• No abortion, frequent reactivation

Question 6

Pathology, Histopathology?

Answer 6

Respiratory form

• Nose, pharynx, larynx, trachea: inflammation, hemorrhage, erosions
• Lung: in pure viral phase: interstitial pneumonia, then later in bacterial stage
• bronchoalveolar pneumonia (croupous) bronchitis, (+Pasteurella, Mannheimia), > atelectasis
• Abortion: liver, heart, skin necrotic foci
• Lymphocytic polio- and leukoencephalitis
• Intranuclear inclusion bodies