Notebook: Equine Respiratory System 2

Treating pleural pneumonia Start with broad spectrum antibiotics (4 quadrant coverage): penicillin, gentomycin, metronidazole. Gas specks in lungs (on ultrasound) probably indicate anaerobic infections; also brown or red nasal discharge and stinky breath. These horses need to be put on metronidazole. Strep. zooepidemicus is the number one isolate; enrofloxacin doesn't get it! Oral drugs: TMS (nice but a lot of resistance), doxycycline, rifampin (not rifampin by itself!).

Will often put on anti-inflammatories (NSAIDs) to increase patient's comfort level. Remember to consider effects on kidneys and stomach. Use thoracic drains if necessary (if there's a lot of fluid). Support with calories very very early.

Increased pleural effusion decreases lymphatic drainage, leading to edema.

When do you stop the antibiotics? Recheck frequently with US (consolidation and abscesses), check fibrinogen and WBC counts, make sure afebrile for 4-5 days afterwards. May also re-check the tracheal wash (though a bit invasive).

Can do rib resection if you encounter "pizza pleura."

Epidemiology: Young racehorses being shipped are at top risk. Next is esophogeal obstruction in older horses, then post-anesthesia and recent viral infection.

Aspiration: When horses aspirate, it goes to the "triangle of death."

Prognosis is good for pleural abscess; horses with pleuritis -- prognosis is a lot worse.

Lympadenopathy, fever and nasal discharge is strangles (Strep. equi equi) until proven otherwise! Gets submandibular and retropharyngeal lymph nodes. Let the dz run its course; treat symptomatically; may want to use NSAIDs; drain abscesses when they're "ripe"; more severe cases will need tracheostomy; put complicated cases on penicillin. Prevention: isolate effected horses until they have a negative culture. May need to identify carriers if barn problems persist. Rare to get strangles twice. 2 vaccines available: new intranasal modified live vaccine is much more effective than the other vaccine. Always give it as the last vaccine because it is a modified live vaccine!

Bastard strangles: metastatic strangles. Lymph nodes in any part of the body are affected; can end up with problems in brain, liver, kidney etc. Diagnose with a titer for Strep. M protein. Treatment: long-term antibiotics. Penicillin works well.

Immune-mediated problems associated with Strep:
Purpura hemorrhagica is a vasculitis associated with the body getting confused by the Strep. Results in severe edema. Penicillin and corticosteroids; good prognosis. If outbreak, don't vaccinate horses that have possibly been exposed! Greater chance that they will develop purpura. Only vaccinate horses that you are really sure have not been exposed.