Osteomyelitis of the pelvis caused by Rhodococcus equi in a two-year-old horse.

The research article discusses a case of a two-year-old horse that was suffering from hind limb lameness, fever, and lethargy. The condition was ultimately diagnosed to be osteomyelitis, a type of bone infection, in the pelvis caused by a bacterium, Rhodococcus equi. Treatment was provided through surgical cleaning of the infected area and administering antibiotics, which led to the complete recovery of the horse.

Clinical Presentation

• The subject of this study was a two-year-old female Quarter Horse that exhibited symptoms like hind limb lameness (difficulty in moving), fever, and lethargy for a duration of two weeks.
• The horse showed signs of hypoproteinemia, characterized by lower than normal albumin levels (hypoalbuminemia) and higher than normal fibrinogen levels (hyperfibrinogenemia).
• Through abdominal ultrasonography, thickening of the horse’s right dorsal colon wall was detected.
• Lameness evaluation suggested the locus of pain to be around the horse’s lumbar vertebrae or pelvis region.

Investigations and Diagnosis

• Despite radiography and nuclear scintigraphy tests showing no abnormalities, ventrodorsal pelvic radiography revealed a specific region of abnormal bone breakdown and growth (bony lysis and proliferation) involving the cranial portion of the pubic symphysis (a joint between the two halves of the pelvis).
• Pus collected from an aspiration procedure bred Rhodococcus equi, a bacterium responsible for causing infections in animals, confirming the diagnosis of osteomyelitis (bone infection).

Treatment and Recovery

• The treatment regimen involved surgical debridement of the abscess (cleaning of the infected and necrotic tissues), combined with oral administration of erythromycin and rifampin (antibiotics). The bacterium was found to be susceptible to erythromycin.
• With the onset of this treatment, the horse’s hind limb lameness completely resolved within 20 days.

Conclusion and Recommendations

• From this case, the researchers concluded that infections of the pubic symphysis can lead to such symptoms in horses.
• They recommended that such infections should be considered when lameness localized to the pelvis region is associated with fever and an abnormal white blood cell count indicating inflammation ( inflammatory leukogram).