In vitro studies of haemolysis by Leptospira interrogans serovars pomona and ballum

Washed and unwashed red blood cells (RBC) from young calves, adult cattle, hamsters and humans were incubated with Leptospira interrogans serovars pomona and ballum. Washed cells suspended in saline were always haemolysed while unwashed cells and those which were washed and resuspended in plasma were never haemolysed, despite the presence of large numbers of organisms within the culture supernatant. Pomona produced greater haemolysis of cattle and human RBC than did ballum, but with hamster RBC ballum produced greater haemolysis than did pomona. A group of 6- to 9-month-old cattle infected with pomona showed no signs of clinical disease and RBC taken from them before infection and during the development of antibodies to pomona were haemolysed by pomona only after the cells were washed. Plasma therefore appears to have a protective function. This in vitro protective function of plasma even extended to plasma from young seronegative calves.     

The incidence of Leptospira hyos and Leptospira pomona infections in pigs in New Zealand

Extract

The occurrence of leptospirosis in New Zealand was first reported by this station in 1950. when Leptospira pornona was isolated from a calf with haemoglobinuria. Since then it has been demonstrated in most farm animals, including pigs, on many occasions.     

Isolation of Leptospira interrogans serovars tarassovi and pomona from dogs

Extract

This communication reports the isolation of Leptospira inter-rogans serovars tarassovi and pomona from dogs in New Zealand.     

Prevention of Leptospira interogans serovar pomona infection in cattle

A commercial hardjo-pomona vaccine which has previously been shown to be effective against hardjo infection was tested against pomona. Following challenge all 11 six-month-old non-vaccinated calves seroconverted and pomona was isolated from blood or urine on at least one occasion from nine of them. Pomona was isolated once only, on the third day after challenge, from the blood of one of 11 vaccinated calves.