Variations mensuelles de Glugea hertwigi (Sporozoa: Microsporida) chez différents tissus et organes de l'éperlan adulte dulcicole et conséquences de cette infection sur une mortalité massive annuelle de ce poisson

Abstract

From September 1964 to September 1965, twelve hundred autopsies were performed at a rate of one hundred per month on the adult stunted population of freshwater smelts Osmerus eperlanus mordax of Heney Lake, Gatineau County, Québec. It is shown that the digestive tract is really the primary site of infection by Glugea hertwigi.Levels of infection are given separately for the anterior, mid, and posterior part of the intestine, for the pyloric ceca, the esophagus, the stomach layers, the anal region, the liver, the male and female gonads, the peritoneum, the air bladder, the adipose tissue, the heart, and kidneys. Glugea cysts in the head, trunk and fin regions were also counted.An increase from 53% to 76% in the general rate of infection happened during the spring (May and June). Since 1960, a mass mortality occurred every spring, in mid-May, and killed around 10 million smelts each year.It is proposed that all organs are susceptible to invasion by Glugea spores and that spring and summer warm water temperature had a positive effect on schizogony and sporogony of Glugea leading to a general infection of the host. It is believed that physiological exhaustion of the adult smelts during spawning time, together with Glugea, is responsible for the massive spring kill.