SALMONELLA-ENTERITIDIS, PHAGE TYPE-4 INFECTION IN A COMMERCIAL LAYER FLOCK IN SOUTHERN CALIFORNIA - BACTERIOLOGICAL AND EPIDEMIOLOGIC FINDINGS

Salmonella enteritidis, phage type 4 (SE PT4), was isolated from five of six 27-wk-old layer chickens submitted for necropsy from a flock of 43,000. Bacteriologic and epidemiologic investigations on the ranch r evealed that five of the eight flocks (n = 176,000) were infected. The prevalence of SE PT4 in randomly selected healthy birds ranged from 1 .7% (in caged birds) to 50% (in free-range birds) and prevalence in cu lled birds (kept on dirt floor houses) ranged from 14% to 42%. The est imated overall prevalence of group D Salmonella in eggs cont aminated with group D Salmonella was 2.28 per 10,000. The estimated prevalence of group D Salmonella in eggs from caged birds in three infected house s ranged from 1.5 to 4.1 per 10,000, whereas in two houses of free-ran ge birds, prevalence was 14.9 to 19.1 per 10,000. Three of the eight f locks on the ranch remained negative for Salmonella between May 1994 a nd December 1995 or until removed from the ranch. Salmonella enteritid is PT4 was also isolated from 12.5% (6 of 48) of mice; 57% (four of se ven) of cats; and two of two skunks tested. Environmental drag swabs a nd well water samples yielded multiple serotypes of Salmonella (23/180 and 5/14, respectively) but not S. enteritidis.