Small Subunit rRNA Gene Comparisons of Four Actinosporean Species to Establish a Polymerase Chain Reaction Test for the Causative Agent of Proliferative Gill Disease in Channel Catfish

Abstract

Abstract Proliferative gill disease (PGD) causes high morbidity and mortality in cultured channel catfish Ictalurus punctatus. The presence of the myxozoan Aurantiactinomyxon ictaluri (class Actinosporea) is strongly associated with PGD. This parasite, shed as an actinospore from the aquatic oligochaete Dero digitata, infects channel catfish by an undetermined route. Several other actinosporeans have been identified that are shed from D. digitata isolated from catfish ponds, including those designated A. mississippiensis, Helioactinomyxon sp., and the actinospore stage of Henneguya exilis. By the use of multiple sequence alignment of polymerase chain reaction (PCR)-amplified small subunit ribosomal RNA (SSU rRNA) genes of A. ictaluri, A. mississippiensis, and H. exilis, we identified two variable regions. The largest variable region was PCR amplified, sequenced from the Helioactinomyxon sp., and used in addition to the other three sequences in multiple-sequence alignment comparison to develop PCR primers ...