Notebook: Equine Respiratory System 3

These are notes taken on cases presented by Dr. Rose Nolen-Walston.

Diagnostic plan fever and abnormal lung sounds: rads, ultrasound, sample.
Rads: miliary pattern. Only a few causes: cancer (metastases), sepsis, fungal dz, silicosis. Nothing good that looks like this on rads! Probably not viral or bacteria.

Plan at this point: How to sample? Use BAL (not trans trach) because it's diffuse. Get fungal hyphae, indicates fungal pneumonia, which is rare. Can be primary or secondary (usually secondary doesn't cause a problem). If suspect primary, get a travel history. Treat with systemic anti-fungals. Tends to be $, and prognosis is poor. Best treatment: Itraconazole. (Case study presented in class resulted in full recovery).

Up to 70% of trach washes have fungal hyphae; THIS IS NORMAL! Do not treat with anti-fungals unless you see evidence of fungal pneumonia: i.e., large numbers of intra and extracellular fungal elements, consistent rad changes, or history.

Pneumocystis (and others) is an opportunistic bug (i.e., SKID foals, recent GI dz, other reasons for immuosuppression). Exactly the same diagnostics, but also test for immune function. Prognosis is poor.

Other possibility for miliary pattern: Interstitial pneumonia (pretty rare)
- present with severe clinical signs, i.e. cyanosis, profound respiratory distress, wasting away, cough, fever, pretty hypoxemic
- diagnose with rads (parenchymal disease)
-- pattern must be diffuse. Do BAL.
- Interstitial pnuemonia may be associated w/ viral dz (like flu), systemic inflammation (ARDS), equine nodular pulmonary fibrosis (may be associated w/ EHV5, pattern looks more nodular than miliary), silicosis: granulomas form around silicon, or ideopathic
- treatment is often futile. Euthanasia often elected if owner decides not to treat. (If you sit and wait, the horse may be fine!)
- prognosis is guarded to poor.

Case presented: foals with puffy joints, no lameness
- if foal w/ puffy joints is lame: septic arthritis (EMERGENCY)
- on ultrasound, see what may be neoplasia/ abscess/ granuloma
- rads pathognomonic Rhodococcus equi.
- Rhodococcus equi causes abscess-forming pneumonia.
- puffy joints but not lame: don't tap
- diagnosis: use cytology (pleomorphic cocci), culture, PCR
- on PCR, only VapA is really bad
- transmission: shed in feces
- use macrolides to treat b/c they go into the cell. Azithromycin stays at effective levels in pulmonary macrophages for 30 days! Treat with macrolides + rifampin.

- Rhodococcus is not the only thing that causes pneumonia in foals: top cause is Strep. zooepidemicus. Diagnose with imaging (rads/ US), sampling (trach wash). Put on broad spectrum (but not penicillin).