resp notes good 3

Question 1

hydrothorax
- what is this?
- major mechanisms?

Answer 1

• Think of this as “edema of the pleural space”
• Clear fluid (transudate) fills the pleural cavity and compresses the lungs
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  The major mechanisms of fluid transudation (and their common causes) are:
• Increased venous pressure (right heart failure in all species, plus left heart failure in cats; excessive intravenous fluids; lung lobe torsion)
• Reduced oncotic pressure: (hypoproteinemia)
• Lymphatic obstruction (eg by a tumor, abscess, granuloma)
• Increased vascular permeability: but, this causes an exudate rather than transudate; thus, the fluid is usually cloudy rather than clear & watery
• Finally, if there is ascites, some of the peritoneal fluid can leak into the pleural cavity through tiny pores in the diaphragm

Question 2

chylothorax
- what is this?
- major causes?

Answer 2

• Milky opaque pleural fluid, rich in triglyceride and lymphocytes, arising from loss of lymph fluid into the pleural space
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• The major causes are:
• Heart failure. Increased central venous pressure prevents drainage of lymph from the thoracic duct into the vena cava.
• Lung lobe torsion.
• Many cases are idiopathic.
• Uncommonly due to obstruction of the thoracic duct by tumours, or other masses, or rarely due to traumatic rupture of thoracic duct.

Question 3

hemothorax
- causes

Answer 3

• trauma (e.g. fractured ribs)
• ruptured tumours (especially hemangiosarcoma)
• idiopathic hemothorax in dogs
• anticoagulant rodenticide toxicity
• thymic hemorrhage syndrome in young dogs

Question 4

pleuritis
- what is it? common causes?

Answer 4

• Inflammation of the pleural cavity usually represents bacterial infection
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• bacteria arrive via 3 routes:
• External penetrating injury
• Extension from bacterial pneumonia or rupture of a lung abscess (common in adult horses)
• Hematogenous spread

Question 5

pneumothorax - external vs internal

Answer 5

• External pneumothorax: penetrating injury that allows air into the pleural space
• Internal pneumothorax: rupture of a pulmonary bulla, or penetrating injury that punctures the lung

Question 6

pleural neoplasms, how they cause clinical signs

Answer 6

• lung tumours may invade the pleura and spread widely in the pleural space
  > metastatic tumour leaks fluid into the pleural cavity, which is the basis for clinical signs of respiratory distress

Question 7

Pneumonic pasteurellosis
- what is this?
- who is affected?
- agents? where are they found?
- how does disease arise?

Answer 7

• bronchopneumonia caused by any bacteria of the family Pasteurellaceae
• affects cattle of various ages; dairy and veal calves, adult dairy cows, and “shipping fever” in beef calves
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  The major causes are bacteria of the family Pasteurellaceae:
• Mannheimia haemolytica
• Bibersterinia trehalosi
• Histophilus somni
• Pasteurella multocida
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• These bacteria carried in the nasopharynx of normal calves
• Disease is thought to require a predisposing cause, such as stress or viral infection

Question 8

Histophilus somni causes what conditions?

Answer 8

• bronchopneumonia
• bacteremia and vasculitis that result in encephalitis (ITEME), polyarthritis, myocarditis, pleuritis, uveitis, and endometritis

Question 9

Mannheimia haemolytica toxin, effects

Answer 9

• leukotoxin
  > causes necrosis of ruminant macrophages and neutrophils

Question 10

pneumonic pasteurellosis clinical signs

Answer 10

• acute onset and mainly reflect the acute phase response: fever, depression, anorexia, lack of rumen fill, and holding back from the feed bunk
• Other clinical signs result from local effects within the respiratory tract: coughing, mucopurulent nasal discharge, tachypnea, dyspnea.

Question 11

shipping fever gross lesions

Answer 11

• cranioventral bronchopenumonia
  > consolidation and reddening, as a result of fibrinopurulent exudate in the alveoli
  > palpably hard
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  Acute cases often have:
  1. Hemorrhagic purple-black lobules, giving a red/tan checkerboard pattern
  2. Loosely adherent fibrinous exudate on the pleural surface
  3. Interlobular septa distended by edema and fibrin
  4. Foci of necrosis visible on the cut surface

Question 12

Chronic cases of shipping fever may develop what lesions?

Answer 12

• tough fibrous adhesions on the pleura
• abscessation of lung tissue
• bronchiectasis
• sequestrum formation.

Question 13

Pneumonic pasteurellosis diagnosis

Answer 13

• by far the most common cause of respiratory signs in cattle
• cranioventral and mostly symmetrical gross lesions

Question 14

Cranioventral bronchopneumonia with concurrent necrosis of tracheal epithelium suggests:

Answer 14

infectious bovine rhinotracheitis, with a fatal secondary bacterial pneumonia

Question 15

Cranioventral bronchopneumonia in which the consolidated lung contains multifocal white circular crumbly foci of necrosis indicates:

Answer 15

Mycoplasma bovis

Question 16

Consolidation affecting predominantly the caudal lung lobes could be caused by what? what should we do?

Answer 16

• Dictyocaulus; open the caudal bronchi to carefully look for worms

Question 17

Pneumonic pasteurellosis sequelae

Answer 17

• Animals may die acutely due to sepsis or “toxemia”, and often not due to respiratory failure
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  Chronic sequelae:
• chronic bronchopneumonia
• abscessation
• sequestrum formation
• bronchiectasis
• pleural adhesions
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• Relapses following apparently successful treatment often occur because these chronic lesions are a persistent source of infection that resists antibiotic treatment.

Question 18

Mycoplasma bovis
- causes what disease?
- when do we see this vs pneumonic pasteurellosis?
- non-lung diseases?

Answer 18

• “chronic pneumonia and polyarthritis syndrome”
• often in conjunction with other pathogens
• many animals may be infected, but only few may develop disease > may cause minimal damage alone but predispose/perpetuate other infections
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• appears in the second month after arrival in feedlots
  > vs pneumonic pasteurellosis in the first few weeks
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• also spreads from the nasopharynx via the auditory tube into the middle ear to cause otitis media with droopy ears or head tilt
• blood-borne spread to the joints to cause fibrinopurulent polyarthritis and tenosynovitis with chronic lameness
• cow-to-cow transmission via the teat canal to cause mastitis

Question 19

Mycoplasma bovis characteristic lesions

Answer 19

caseonecrotic bronchopneumonia:
- cranioventral bronchopneumonia in which the consolidated areas contain multiple, circular, white, raised, friable foci of caseous necrosis

Question 20

• Major reasons for aspiration pneumonia in cattle include?
• lesion characteristics?

Answer 20

• Force-fed milk replacer, liquid medicines, misplaced esophageal tube.
• Cleft palate. Be sure to look for this in young animals with pneumonia.
• Recumbency: milk fever or mastitis.
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• cranioventral
• localized or unilateral lesion
• often foul-smelling and necrotic/friable due to anaerobic bacterial infection

Question 21

major risk factors for bacterial pneumonia in cattle

Answer 21

Viral infections, along with stressors