135. Respiratory pasteurellosis of cattle.

Question 1

Occurrence ethiology and epidemiology?

Answer 1

OCCURRENCE, ETIOLOGY & EPIDEMIOLOGY

• Mainly in young animals
• Forms: shipping fever (transit fever),
• bovine respiratory disease complex (BRDC) ʹ endemic (young)
• Caused by P. multocida A (D), M. hemolytica A1, A2
• Predisposing factors
• Non-infectious

1. Management,
2. nutrition,
3. overcrowding,
4. transport,
5. starvation,
6. thirst,
7. cold,
8. mixing animals of different origin,
9. feedlots,
10. age (1-3 months ʹ endemic form)

• Infectious:

1. Virus infections (PI-3, IBR, adenovirus, RS, BVD),
2. Mycoplasma,
3. Chlamydia

Question 2

Pathogenesis?

Answer 2

PATHOGENESIS

• Airborne infection
• colonization of the upper airways, asymptomatic
• Stress and predisposing factors lead to bacterium propagation and colonization of the lungs
• M. hemolytica
• Leukotoxin (Cytotoxin) production ʹ damage of the alveolar macrophages (bacteria can propagate without inhibition),
• production of prostaglandins,
• mediators will attract more macrophages, that also will be lysed
• formation of thrombi and necrosis
• Secondary agents: complication (streptococci, staphylocci, truperella etc.)
• more serious purulent pneumonia

Question 3

Clinical signs and pathology?

Answer 3

CLINICAL SIGNS & PATHOLOGY

• Most frequently in calves between 1-3 months
• Fever,
• anorexia,
• cough (beginning only by provocation, later spontaneously)
• nasal discharge,
• dyspnea (will become more severe as disease progresses)
• weight loss,
• death

Pathology

• Tracheitis, bronchitis :hyperemic and muco-purulent discharge
• Fibrinous pneumonia (mainly in anterior lobes), fibrinous pleuritis
• If very virulent strain
• fibrinous pericarditis
• Histopathology ʹ large amount of inflammatory cell infiltration, hyperemia, and fibrin accumulation

Question 4

Diagnosis?

Answer 4

DIAGNOSIS

• Epidemiology (predisposing factors),
• clinical signs (not so informative)
• pathology (prelim. Diagnosis)
• Detection of the agent - Important in acute form of the disease
• Isolation (best from lungs, sometimes can use mediastinal lymph nodes), identification, IF, PCR
• Detection of antibodies ʹ ELISA, immunoblot, passive hemagglutination
• Enough time is needed for production of antibodies, so not good for diagnosing acute disease
• Detection of primary pathogens
• detection of agents (isolation)
• serology (paired sera sample)
• collect sera in acute phase and a few weeks later
• Differential diagnosis ʹ respiratory diseases

Question 5

Treatment?

Answer 5

TREATMENT

• Isosolation of ill animals
• Antibiotic treatment ʹ tetracyclines, fluoroquinolones, macrolides,
• USA : preventive ab treatment at feedlots
• Elimination of predisposing factors

Question 6

Prevention?

Answer 6

PREVENTION

• Prevent predisp. Factors:
• individual cages for calves,
• vaccination against viral predisposing factors
• Vaccination
• Killed vaccines ʹ P. multocida, M. hemolytica, H. somni ʹ sometimes comb. vaccines with virus strains
• Serotype specific protection
• Toxoid vaccines ʹ contain leukotoxin in inactivated form