145. Actinobacillus pleuropneumonia of swine.

Question 1

Occurence, ethiology and epidemiology?

Answer 1

OCCURRENCE, ETIOLOGY AND EPIDEMIOLOGY

• Worldwide, common occurrence, have high economic impact
• Caused by A. pleuropneumoniae
• 2 biotypes: 1: NAD is needed, 2: NAD is not needed
• Virulence variants: due to different combination of cytotoxins produced by the bacteria
• Virulence factors: 4 cytotoxins, adhesins, capsule, outer membrane proteins, LPS
• 19 serotypes : geographical differences
• Low resistance
• Only pigs are susceptible, carrier pigs are responsible for introduction
• All age groups are susceptible, but disease generally occur above 6-8 weeks of age (after maternal Ab)
• Predisposing factors
• Quality of air, nutrition, overcrowding, mixing, ventilation, mycotoxins
• Infective agents: circovirus, PRRS, mycoplasma, Pasteurella
• Difference between biotypes
• 1: high virulence: high morbidity and high mortality
• 2:low virulence: low morbidity and low mortality

Question 2

Pathogenesis?

Answer 2

PATHOGENESIS

• Aerosol infection by inhalation
• colonization of the respiratory tract
• Predisposing factors
• replication in the lungs
• Cytotoxins: damage the alveolar macrophages causing release of cytokines, which will help the
• replication of the bacterium
• pleuropneumonia
• Also damage endothelial cells, result in microthrombi
• block blood vessels, necrosis
• Sometimes (rare) hematogenic spreading to kidney, brain, joints (cause local clinical signs)
• Remain carriers after recovery

Question 3

Clinical signs and pathology?

Answer 3

CLINICAL SIGNS & PATHOLOGY

• Peracute: fever, depression, cyanosis, respiratory signs death
• Acute: fever, cyanosis, labored breath, dyspnea, nasal discharge (blood, foam (due to incr. breathing rate)
• Chronic: respiratory signs (mild), decreased production (weight gain), sometimes returning cough
• Pathology: both biotypes cause same lesions PM, so cannot differentiate
• Hemorrhagic-necrotic pneumonia, foci, most typically in the diaphragmatic lobe
• Have a mottled ʹ marble-like appearance due to the different lobes are in different phases of
• the disease
• Fibrinous pleuritis on surface of the lungs
• Chronic ʹ demarcation of lesions
• Histopathology ʹ strong cellular infiltration, elongated nuclei in alveoli (due to cytotoxic effect)

Question 4

Diagnosis and differential diagnosis?

Answer 4

DIAGNOSIS

• Epidemiology, clinical signs and pathology ʹ can make the diagnosis on the farm!
• Detection of the agent: isolation of the bacterium, IF, co-agglutination, PCR
• Detection of the antibodies ʹ agglutination, CFT, ELISA,
• Detection of antibodies against APxIV ʹ 4th cytotoxin (only produced by A. pleuropneumoniae), the other
• cytotoxins can also be produced by bacilli
• Differentials
• Generalized diseases : CSF, ASF, swine influenza
• Respiratory diseases : pasteurellosis, mycoplasmosis, Aujeszky disease, PRRS

Question 5

Treatment?

Answer 5

TREATMENT

• Antibiotics: beta-lactam, macrolides (concentrated in the lungs), fluoroquinolones
• Individual (parenteral injections) and mass treatment (metaphylactic treatment of asympt. animals),
• remain carriers after treatment
• Improve hygienic conditions

Question 6

Prevention?

Answer 6

Prevention

• Prevent introduction, prevent predisposing factors
• Vaccine: inactivated bacteria (type specific protection), toxoid (inactivated cytotoxins and surface proteins = wider protection),
• recombinant vaccines
• Eradication:
• selection + antibiotic treatment,
• generation shift + antibiotic treatment,
• herd replacement

Question 7

A.suis ?

Answer 7

A. SUIS INFECTION

ETIOLOGY AND DISEASE FORMS

• Caused by A. suis,
• produce cytotoxins, normally present on the nasal mucosa
• Adult: septicemia, abortion, metritis, arthritis, nephritis; Piglets ʹ intra-uterine infection, septicemia
• Sometimes infect Foal and calf: cause sporadic septicemia

CLINICAL SIGNS AND PATHOLOGY

• Clinical signs: fever, labored breath, arthritis, cyanosis
• Pathology: hemorrhages, enlarged parenchymal organs, hemorrhagic and necrotic pneumonia

DIAGNOSIS, TREATMENT AND PREVENTION

• Epidemiology, clinical signs and pathology;
• isolation of the agent
• Differentials: generalized diseases
• Treatment: antibiotics