Featured Case of the Month - "Felizshah"
Signalment: 2 month old Arabian filly
History: Felizshah presented to SWEMSC for evaluation of a sudden onset of fever, respiratory distress, and diarrhea. Approximately one month previously, she had been shipped from Tucson to Phoenix for her mother to be bred. She was treated on the farm with intravenous fluids, antibiotics, and Biosponge for one day with no improvement.
- Dull, depressed, and lethargic
- Increased respiratory rate and effort with nostril flare
- Bilateral nasal discharge
- Lungs sounded harsh with crackles and wheezes heard on both sides of chest
- High heart rate
- Increased stifle joint fluid (effusion)
- Blood tests revealed low white blood cells, a high platelet count, elevated fibrinogen, and slightly decreased albumin. These findings are consistent with severe inflammation.
- Due to fever and diarrhea, a fecal culture for Salmonella was performed. The results were negative.
- Radiographs showed multiple abscesses throughout the lungs (Fig A and B)
- Ultrasound of the chest showed bilateral areas of nonaerated lung (comet tail artifacts, pulmonary consolidation) and abscessation (cavitating lesions), predominantly in the 5th-9th rib spaces (Fig C)
- A sample of tracheal fluid was obtained and submitted for cytology, culture, and PCR.
- Cytology - degenerate neutrophils and coccobacilli (consistent with infection)
- PCR - positive for Rhodococcus equi
- Culture - positive for Rhodococcus equi
A) This radiograph of Felizshah's lungs shows multiple pulmonary abscesses caused by R. equi
B) This radiograph shows normal lungs in a similar aged foal.
C) This thoracic ultrasound image shows a cavitating lesion (abscess) caused by R. equi
D) Bilateral stifle synovitis (non-septic inflammation of the joint)
Diagnosis: Rhodococcus equi pneumonia, diarrhea, and synovitis
Horse Owner Education:
Rhodococcus equi is a widespread bacterium that lives in the soil. It grows very well in horse manure and thus may become endemic on some breeding farms. It is an important cause of disease in foals age 1- 6 months. Rhodococcus is an intracellular bacterium which can replicate in the intestine of foals up to about 3 months of age. Most foals are thought to be infected during the first 2 weeks of life when they are most susceptible. However, clinical signs may not develop until months later. Inhalation of contaminated dust particles is the most important route leading to infection of alveolar macrophages. This causes multiple abscesses to form in the lungs resulting in pneumonia. It can also infect the gastrointestinal tract leading to colic or diarrhea. Clinical signs of Rhodococcus infection can include fever, increased respiratory rate and effort, coughing, bilateral nasal discharge, diarrhea, synovitis (inflammation of joints), uveitis (inflammation of the eye). Most affected foals have an increased white blood cell count and fibrinogen (a marker of inflammation). Bacteremic spread from the lungs or gastrointestinal tract may sometimes result in infection of the bones, joints, or abscess formation in other parts of the body, including the spinal cord.
Felizshah was placed on antibiotics (clarithromycin and rifampin) that are able to penetrate abscesses, enter the cells, and kill R. equi. Intravenous fluids were given to maintain hydration and replace fluid losses from the diarrhea. Biosponge and metronidazole were added to absorb toxins and treat other bacterial causes of diarrhea (such as Clostridium). The diarrhea resolved within a few days of treatment. Blood work was repeated and revealed an increased white blood cell count and a very high platelet count. Since Felizshah was stressed from her illness and was grinding her teeth (which may be a sign of gastric ulcers), she was placed on sucralfate and Gastroguard to treat and prevent gastric ulcers. Felizshah continued to have an increased respiratory rate and effort and required intranasal oxygen therapy and bronchodilators to help open up her airways. She developed high fevers which were treated with anti-inflammatory medications and alcohol baths. While in the hospital, Felizshah was very ill; she had a poor appetite and was losing weight. She was offered a variety of feeds and supplemented with corn oil to help add calories to her diet. She also received B vitamins to help stimulate her appetite. After about 2 weeks of antibiotic therapy in the hospital, Felizshah showed enough improvement to be discharged.
Felizshah continued to improve with antibiotic treatment at home. She returned 6 weeks later for a check up. Her respiratory rate and effort were normal and no crackles or wheezes were heard in her lungs. Her white blood cell count, platelet count, and fibrinogen had returned to normal values. Ultrasound of her chest showed only some minor areas of non-aerated lung (consolidation). No abscesses were visualized.
Prevention of Rhodococcus Equi pneumonia in Foals:
- Ensure adequate colostrum intake and check IgG
- Take temperature and auscult lungs often in young foals
- House foals in well ventilated areas
- Remove feces from stalls and paddocks frequently
- Decrease dust formation in stalls and paddocks
- Isolate sick foals
- On farms with enzootic R. equi problems, hyperimmune plasma may be administered during the first week of life.