MYXOBOLUS-CEREBRALIS IN TUBIFEX-TUBIFEX FROM A WHIRLING DISEASE EPIZOOTIC IN MONTANA

Aquatic oligochaetes from a whirling disease enzootic area in southwes t Montana were examined for infection with Myxobolus cerebralis. Anter ior portions of oligochaetes were preserved for specific identificatio n, whereas DNA was purified from posterior portions. The purified DNA was used in a nested polymerase chain reaction (PCR) assay specific fo r M. cerebralis small-subunit ribosomal DNA. Naturally infected oligoc haetes were identified by a resulting 415-bp fragment of amplified par asite DNA. A total of 704 oligochaetes was tested from April through S eptember 1997. Eighteen (2.6%) oligochaetes were infected with M. cere bralis as defined by the nested PCR assay. Two of these were identifie d as mature Tubifex tubifex, and the others were likely T. tubifex but were immature and lacking the diagnostic reproductive structures. Thi s is the first report of T. tubifex naturally infected with M. cerebra lis.