Long segmented filamentous organisms in broiler chicks: possible relationship to reduced serum carotenoids.

Over the past several years, broiler-flocks at the author's laboratory have exhibited low serum carotenoid levels. This phenomenon has not been related to exceptionally low carotenoids in the feed or to known protozoan or viral infections. However, long segmented filamentous organisms (LSFO) have been identified in the pale chicks. An inverse correlation between LSFO counts and serum carotenoid levels was not observed, but prevention of LSFO infection consistently resulted in higher carotenoid values. Young chicks were very susceptible to naturally acquired LSFO infection, but the organisms decreased in number with time and became very difficult to find by the time the chicks were 7 wk old. Segments of LSFO containing endospores were detected in mucosal smears. This observation, along with the extreme ease of natural infection, suggests that LSFO are transmitted by dust-borne spores. Transmission can be prevented by fumigation of housing with formaldehyde vapors.