Intestinal Chlamydial Infections: Introduction

Chlamydiae have been isolated from fecal samples of clinically normal cattle, goats, sheep, and pigs in many parts of the world. Animals with clinically inapparent intestinal infections may shed chlamydiae in the feces for months and possibly years. Accordingly, the GI tract serves as an important reservoir and source for the transmission of these organisms. Chlamydiae, which may cause abortions ( Abortion in Cattle: Overview) and pneumonia ( Chlamydial Pneumonia: Introduction), can readily be isolated from feces of normal sheep and cattle. They have also been recovered from intestinal samples of animals affected with polyarthritis ( Chlamydial Polyarthritis-serositis), encephalomyelitis ( Sporadic Bovine Encephalomyelitis: Introduction), and conjunctivitis ( Chlamydial Conjunctivitis: Introduction). Most fecal isolates from ruminants belong to the species Chlamydia pecorum but some isolates belong to Chlamydophila (Chlamydia) psittaci . The intestinal infection plays an important role as an initiating event in the pathogenesis of several chlamydia-induced diseases. The intestinal infectious phase also plays an important role in avian chlamydiosis ( Avian Chlamydiosis: Introduction).

Equine gastrointestinal anatomy

While most of the intestinal chlamydial infections are clinically quiescent, a primary chlamydia-induced enteritis has been seen under field conditions in newborn calves. Such infections may also lead to a change in the number of Escherichia coli in the GI tract, with abnormally high numbers in the abomasum and upper small intestine. Signs are more severe in colostrum-deprived calves or in those with only a partial transfer of colostral immunity. Affected newborn calves may have a transient watery to mucoid diarrhea with slight fever and nasal discharge. Many veterinary diagnostic laboratories do not routinely check diarrheic feces for chlamydiae; therefore, such an examination must be requested specifically. Treatments of choice are high doses of tetracyclines, administered parenterally or orally, or both.