75. Diseases caused by bovine respiratory syncytial virus and parainfluenza-3 virus.

Question 1

Bovine respiratory syncytial virus Occurrence?

Answer 1

Bovine respiratory syncytial virus

• Paramyxoviridae, Pneumovirinae, Pneumovirus genus, Bovine respiratory syncytial virus

Occurs:

• worldwide Hosts: Bo (Ov, Cap)
• Appears in 2 forms: either enzootic or epizootic (if it is introduced)
• Enzootic: calves 3 weeks- 6 months as maternal Ab level decreases
• Part of BCRDC (the virus alone will not kill the animal)
• Epizootic: if no RS present previously & someone brings an animal with the virus, highly lethal btwn 6-12 month old calves (lung emphysema, pneumonia, anaphylactic shock-like signs)

Question 2

Epizootiology of Bovine respiratory syncytial virus?

Answer 2

Epizootiology

• Intro with infected animal, More frequent in autumn, winter
• 6 months - 2 years old calves get mainly sick (6-24 months) (2-6 month: BRDC)
• Quick spread in the farm, contagious ʹ 100% morbid, 1-2% mortality
• Shed through excretes air-borne infections, long term carry may occur
• Calves of convalescent cows are protected by maternally derived Abs
• Frequent co-infection with PI-3 virus

Question 3

Pathogenesis of Bovine Respiratory syncytial virus?

Answer 3

Pathogenesis

• Aerosol: Alveolar epithelia infection
• alveolitis, bronchiolitis ʹ instl oedema
• Alveoli produce hyaline membrane
• pneumonia, allergic reaction, interstitial emphysema
• Air may get through lymphatic vessels under the skin
• If 2dary bacterial , severe!!
• Immune reaction gives long lasting protection
• 6 months- 2 years, independently serious pneumonia, allergic reactions
• Droplet infection ʹ highly contagious

Question 4

Clinical signs of Bovine respiratory syncytial virus?

Answer 4

Clinical signs

• 2-3 days incubation, high fever (41.5oC), general signs
• Laboured breath (gasp for air), dyspnoea, dry cough, serous nasal discharge ,wet cough
• SC emphysema, alveoli filled with hyaline membrane ʹ inhibit gas
• Bacterial complications ʹ croupous pneumonia
• exchange (forced breathing)

Question 5

PM lesions of Bovine respiratory syncytial virus?

Answer 5

PM Lesions

• Alveolitis, interstitial pneumonia, interstitial (bullous) emphysema
• Trachea: Foam, mucosal haemorrhage
• Syncytium, cytoplasmic inclusions

Question 6

Diagnosis of Bovine respiratory syncytial virus?

Answer 6

Diagnosis

• Age, signs, lesions
• Agent: RT-PCR, IF, ELISA (viral isolation complicated)
• Serology: VN (paired sera), ELISA
• Enzootic infection: serological tests

Question 7

Differential diagnosis, treatment control and prevent?

Answer 7

Differential diagnosis

• Bovine parainfluenza: mildersigns
• IBR: mucosal lesions, abortions +/-
• Pasteurella, Mannheimia, Histophillus ʹ severe pneumonia

Treatment:

• rest,
• anti-histamine,
• Abs (for 2dary bacterial infections)

Control:

• Technology (closed farming, isolation of age groups, hygiene)

Prevent:

• Vaccines , inactivated, polyvalent: with those above for BRDC (can give after 2-3 months if no colostral
• protection)
• vax at 5-6 month, then 2nd shot 3 weeks later
• live attenuated vaccine͗s
• Intranasal spray(local immunity)
• Benefit is it’s not inhibited by maternal antibodies

Question 8

Occurrence and epizootiology of Bovine Parainfluenza ?

Answer 8

Bovine parainfluenza-3

Occurrence:

• worldwide, frequent
• Causative agent: Paramyxoviridae, Respirovirus genus, Bovine parainfluenza virus 3

Epizootiology

• Ubiquitous
• Susceptible: mainly cattle, but also Ov, Cap, other Ru
• Introduction with infected animal
• Usually enzootic in cattle farms (because herd always young)
• In autumn, winter more frequent ʹ seasonality

Question 9

Pathogenesis of Bovine parainfluenza?

Answer 9

Pathogenesis

• Shedding via discharges ʹ airborne infections, replicate in respiratory epithelia
• Infection of bronchial epithelia ʹ hyperemia, necrosis, exfoliation
• Hyaline membrane production in the alveoli; coughing ʹ bleeding, emphysema
• Simultaneous virus infections (BAdV, IBRV, RSV); bacterial complications
• Part of BCRDC (bovine chronic resp disease complex)
• Usually in young animals, growers, stress can facilitate (shipping fever ʹ in adults too)
• Morbidity high, mortality low (calves btwn 1 & 3 months become susceptible as maternal Absdecr)

Question 10

Clinical signs and Pathology, Histopathology of Bovine parainfluenza?

Answer 10

Clinical signs:

• Short incubation period (a few days)
• Fever, coughing, nasal discharge (clear Æ mucoid), laboured breath
• With bacterial complications more severe resp signs

Pathology, histopathology:

• Bronchitis, bronchotracheitis, bronchointerstitial pneumonia, mild pleuritic ʹ anterior lobe
• Cytoplasmic inclusion bodies

Question 11

Diagnosis, differential diagnosis and treatment of Bovine parainfluenza 3?

Answer 11

Diagnosis:

• Age, clinical signs, pathology lesions
• RT-PCR, IF
• Isolation (strong CPE), HA
• Serology: HAI, VN, ELISA
• Paired sera: atbs present could be from recovery/vaccine ʹ so should do 2
• during acute phase and 2-3 weeks after
• If increases by 4 x
• current infection

Differential diagnosis:

• IBR: mucosal lesions, abortion +/-
• Bovine resp syncytial virus: more severe signs
• Pasteurella, Mannheimia, Histophilus ʹ severe pneumonia
• Co-infections are frequent

Treatment:

• supportive + ABs

Question 12

Control and prevention of Bovine parainfluenza 3?

Answer 12

Control:

• farm management (closed farming, isolation of age groups), hygiene

Prevention

• Live, inactivated, usually combined vaccines
• Vaccination of pregnant cows in the 3rd trimester ʹ increased colostral immunity
• Vaccination of calves at 4-5 months of age
• Intranasal at 3 weeks of age(maternal antibodies dont interfere)