Bacterial Pneumonia

When do foals lose maternal antibodies?

6 months old, so need to vaccination 6-12 months of age

What are the C/S of bacterial pneumonia?

Fever, depression, abnormal lung sounds, purulent nasal discharge, fibrinogen and neutrophilic leukocytosis

What are some predisposing factors to pneumonia?

EHV-4, weaning, overcrowding, parasitic pulmonary migration, transportation

What is the most common bacterial pathogen that causes pneumonia?

Strep equi subsp. zooepidemicus

What is Rhodococcus equi?

Gram-positive pleomorphic and intracellular bacteria that multiplies within alveolar macrophages

Gets infected early, but does not show C/S for a few weeks

How is R. equi transmitted?

Inhalation from stalls and paddocks. Most common in foals born in January or February

Infected in first week of life

T/F Rhodococcus equi infection in 2-3 months old is an acute manifestation of chronic disease?

True

What can you find on necropsy of R. equi?

Peripheral abscess formation

What is an extrapulmonary disease common with R. equi?

Diarrhea, immune-mediated polysynovitis, ulcerative enterotyphlocolitis, intra abdominal abscesses, abdominal lymphadenitis

How do you treat R. equi?

Azithromycin ± rifampin for 3-5 weeks

Antiulcer meds, flunixin meglumine, O2, bronchodilation

What are the adverse reactions of macrolides?

Anhidrosis, hyperthermia, enterocolitis, fatal enterocolitis

T/F macrolides cause dose depending induction of anhidrosis?

True

How can you prevent R. equi infection?

Hyperimmune plasma

Avoid overcrowding

Separate affected foals

Monitor herd

US screening

How does hyperimmune plasma prevent R. equi?

Need to be given in first 1-2 days of life and repeated at 28-30 days old to bind circulating bacteria

How is R. equi shed?

Live bacteria in feces from foals which then exposes neonates

Why cant you use FQs in foals?

Cartilage damage

What diagnostics do you want for pneumonia?

CBC/chem

Transtracheal wash

Thoracic US

Thoracic rads

T/F R. equi pneumonia is a young horse disease?

True

What is VapA?

Virulence factor that supports pathogenicity of R. equi

Not all strains have VapA and without it then it is not pathogenic. Can do a PCR to check if it is pathogenic or not

How does R. equi live in the host?

In macrophages and replicates

What type of inflammation does R. equi create?

Granulomatous inflammation

What are the extrapulmonary diseases caused by R. equi?

Tibiotarsal effusion

Anterior uveitis with fibrin in anterior chamber

Can cause granulomatous inflammation in GI

Paravertebral abscesses

What causes bacterial pneumonia in adults?

Rare, usually from a virus leading to secondary invaders, long distance travel stress, or following esophageal obstruction and aspiration

T/F you can use FQs to treat S. equi in adults?

True

What are signs that broncho pneumonia has progressed to pleuropneumonia?

Pyrexia, lethargy, exercise intolerance, long distance transport, esophageal obstruction, abnormal auscultation

Leukopenia acutely then progression to leukocytosis

Hyperfibrinogenemia

Anemia

Azotemia from dehydration

How do horses get pleuropneumonia?

Bronchopneumonia progresses to it

What is a good way to get more info on pulmonary pathology?

US and rads

Might need to remove fluid to get a better view