Effects of temperature on the development of Loma salmonae and resistance to re-infection in rainbow trout (Oncorhynchus mykiss)

Loma salmonae, an economically important microsporidian parasite of farm-reared Pacific salmon, causes severe branchial infections. No treatment currently exists to control L. salmonae infections. Consequently, other mechanisms of control are essential. Water temperature has a regulatory effect on the life cycle and development of many pathogens and has been used to control some infectious diseases. It may be used as a means of controlling parasitic infections with Loma salmonae; however, little is known about the relevant pathobiology of this parasite. Objectives of this research were to determine the permissive developmental range for the life cycle of L. salmonae, the effect of temperature on xenoma development rate and the abundance of branchial xenomas that develop, and to examine resistance induction for controlling parasitic infections. Juvenile rainbow trout reared in freshwater were exposed to infective tissue by either intubation or feeding of infective gill material. They were then reared at water temperatures of 5$\sp\circ,\ 7\sp\circ,\ 9\sp\circ,\ 10\sp\circ,\ 11\sp\circ,\ 13\sp\circ,\ 15\sp\circ,\ 17\sp\circ,\ 19\sp\circ,\ 20\sp\circ$ or 21$\sp\circ$C. Since exposure time was known, a polynomial regression model and a thermal unit summation model ($\sp\circ$C-days) were useful for predicting time of xenoma onset. (Abstract shortened by UMI.).