Experimental concurrent infection of cattle with Ostertagia ostertagi and Salmonella dublin

Six seven-month-old Friesian steers were given 8.1 X 10(9) Salmonella dublin orally. Four had been infected with third stage larvae of Ostertagia ostertagi on four occasions over the previous three months. All became pyrexic and excreted S dublin in the faeces for eight to 15 days. Intravenous injection of 8.7 X 10(8) S dublin six weeks later produced similarly mild effects in parasitised and control animals alike. Two parasitised animals stopped excreting S dublin after three and five weeks respectively; the other four were still excreting regularly when killed eight weeks after intravenous infection. S dublin was recovered from the carcases of all six. O ostertagi, unlike Fasciola hepatica, did not increase susceptibility to S dublin or predispose to prolonged infection.