Genetic variation in Australian isolates of myxoma virus: an evolutionary and epidemiological study.

Myxoma virus and the European rabbit have been coevolving in Australia since the introduction of the Standard Laboratory Strain (SLS) of myxoma virus as a biological control agent for rabbits in 1950. To examine the degree of genetic variation that has occurred in the virus between 1950 and 1995 and to find genetic markers to use for epidemiological studies, we have examined 37 recent field isolates of myxoma virus for restriction fragment length polymorphisms (RFLPs) by comparision with the progenitor SLS released in 1950. Fifteen RFLPs in Australian isolates have been identified and characterized by mapping and partial DNA sequence analysis. The RFLPs that are most common are deletion and insertion events in regions of tandem repeats. Some of these RFLPs have been investigated by using polymerase chain reaction to identify them in archival tissue samples. In epidemiological studies we characterized two polymorphisms which occur in the Lausanne strain of myxoma virus (widely introduced into Australia from the 1970s) but not in SLS and showed that all of the viruses we isolated were derived from the SLS.