Isolation of Campylobacter fetus subspecies fetus in a two-year-old quarterhorse with chronic diarrhea of an undetermined etiology.

The research article is about a case study of a two-year-old quarterhorse suffered from chronic diarrhea and weight loss for undetermined reasons. The researchers identified the bacteria Campylobacter fetus subspecies fetus as a possible cause for this condition, a notion endorsed by the transient improvement on treatment with a specific antibiotic and the inability to identify the bacteria at nine months.

Case Overview

• The study is centered around a two-year-old quarterhorse suffering from chronic diarrhea and weight loss for a period of five weeks.
• Despite carrying out numerous diagnostic tests, no specific cause for the horse’s condition could be identified.
• The horse was normally kept at a pasture, where household waste vehicles were cleaned. The cleaning effluent was allowed to run onto the field, suggesting possible exposure to environmental contaminants.

Diagnostic Findings and Its Implications

• Initial diagnostic tests for several infectious agents, such as Salmonella spp., Cryptosporidium spp., and Clostridium spp, were negative. Tests for endoparasites and infiltrative bowel disease also returned negative.
• A histopathological examination of rectal tissue did not identify spirochetal organisms or submucosal infiltration with cells, excluding some potential causes of chronic diarrhea.
• However, a biopsy of the rectal tissue and fresh fecal sample identified the presence of many Campylobacter organisms, not previously associated with the horse’s clinical signs. This was confirmed with molecular testing that identified the species as Campylobacter fetus subsp. fetus, suggesting a possible association with large bowel disease in the filly.

Treatment and Response

• It was observed that the bacteria were sensitive to fluoroquinolone antimicrobials in laboratory conditions.
• The filly showed transient improvement 72 hours after the commencement of therapy, with the occurrence of discrete fecal balls.
• Notably, at a five months follow-up, the horse had gained weight and displayed increased alertness and responsiveness, although the diarrhea returned.
• At the nine months mark, a reculture of the feces was unable to identify any Campylobacter organisms, indicating a possible eradication of the bacteria from the horse.

Significance of Findings

• This report is the first of its kind to identify Campylobacter fetus subsp. fetus in the feces and tissue of a horse using molecular methods. This suggests the organism may play a role in chronic diarrhea in horses, highlighting a new pathogen of concern in equine medicine.
• While the horse only showed a transient response to the therapy, elimination of the bacteria from the system suggests it may have contributed to the originally observed illness in the horse.