PREVALENCE OF SALMONELLA INFECTION IN SHEEP AT SLAUGHTER

The prevalence of subclinical Salmonella infection in sheep at slaughter was monitored at two slaughter-houses in the southem part of the North Island over a 17-month period during 1975 and 1976. The crude prevalence rate was 4.7% (96/lOl7). Prevalerates were greatest in the 2 and 4-tooth age group, with maximum monthly rates of3O%and 32% during 1975 and 1976 respectively. The seasonal distribution of infections was similar in each age group, prevalence rates being greatest in March, April and May, and least in October, November and December. Salmonella typhimurium was found in 78% of the infected sheep, and phage-type 1 caused 72% of these infections. Other serotypes isolated were S. bovts-morbiftcans, S. derby, S. newington, S. saintpaul. S. analum and S. enteritidis. The organisms were all fully sensitive to nine antibiotics. On the grounds that 87% of the infected sheep had salmonellae in their intestinal lymph nodes, it was deemed likely that most of the infected sheep harboured their infections while still on the farms of origin. © 1979 Taylor & Francis Group, LLC.