The effects of elevated temperatures and various time-temperature combinations on the development of Brachiola (Nosema) algerae n. comb. in mammaliancell culture

Nosema algerae Vavra and Undeen 1970, a microsporidian known to cause infec tion in mosquitoes, develops in mammalian cell cultures at 24-35 degrees C and in the tails and footpads of athymic mice. More recently it has been re ported to grow at 38 degrees C in human cell culture. The present study is a two-part temperature/development examination. The first part examines the development of N. algerae in rabbit kidney cell culture at 29 degrees C, w hich permits the formation of functional spores within 72 h, and compares t he effect of elevated temperatures (36.0, 36.5, 37 degrees C) on parasite d evelopment. At these elevated temperatures, N. algerae infects but undergoe s only one or two proliferative divisions, with no evidence of sporogony by 72 h post-inoculation. During this time, however, the host cells continue to divide resulting in fewer infected cells over rime and giving the appear ance of a diminished parasitemia. Additionally, at 37 degrees C some organi sms degenerate/hibernate by 72 h while others remain viable/active. It is n ot until 96 h that the parasites appear in large clusters of proliferative stages in the few host cells that are infected. By 120 h post-inoculation. proliferative cells, sporoblasts, and early spores are observed. These resu lts suggest that elevated temperatures impede proliferation rates and the o nset of sporogony. The second part of this study evaluates developmental ch anges in N, algerae when incubation temperatures and times are varied durin g parasite growth, resulting in abnormal parasite morphology. These abnorma lities were not present when parasites were grown at constant temperature ( 29-37 degrees C). This report demonstrates that N. algerae can successfully develop at high temperatures (37 degrees C), justifying its taxonomic relo cation to the genus Brachiola.