HAEMOLYSIS AS A MEANS OF DISTINGUISHING BETWEEN LEPTOSPIRA INTERROGANS SEROVARS BALCANICA AND HARDJO

Leptospires of the Hebdomadis serogroup have been isolated from a wide range of vertebrate hosts throughout the world (Communicable Diseases Center, 1966 and 1973). Only two serovars, hardjo and balcanica, belonging to this serogroup are known to be present in New Zealand.

Hardjo appears to be maintained by cattle (Johnson, Allan and Dennett, 1974; Ellis and Michna, 1977; Hellstrom, 1978), whereas balcanica has a wider host spectrum. Balcanica is endemic in possums (Trichosurus vulpecula) in New Zealand (Hathaway, Blackmore and Marshall, 1978) and in Australia (Durfee and Presidente, 1977); the original strain, 1627 Burgas, was isolated from a patient in Bulgaria (Babudieri and Mateew, 1961; Manev and Siromashkova, 1970), and subsequent strains were isolated from cattle and pigs in the Soviet Union (Semenova, Soloshenko and Ananyin, 1965).

Balcanica and hardjo are antigenically similar and the infections that they produce are not easily differentiated serologically (Hellstrom, 1978; Hathaway and Marshall, 1979). At present, the usual means of differentiating balcanica and hardjo is agglutinin absorption, which is not a routine procedure in most diagnostic laboratories.

Several serovars of various serogroups are known to be haemolytic; haemolytic activity has not been found in any serovar of the Hebdomadis serogroup (Russell, 1956; Kmety and Bakoss, 1961; Kasârov, 1970; Hodges, 1974) except serovar haemolyticus, strain Marsh (Alexander et al., 1956). This report describes the in-vitro haemolytic activity of balcanica for human, bovine, ovine and possum red blood cells (RBC). This activity may be used as the basis of a simple test for the preliminary differentiation of balcanica and hardjo isolates.