Influence of Transmission Period on Primary and Relapse Patterns of Infection of Leucocytozoon spp. and Haemoproteus mansoni

Abstract

Leucocytozoon sp., L. lovati and Haemoproteus mansoni infections in captive blue grouse (Dendragapus obscurus) were monitored weekly throughout primary and relapse periods. Chicks developed primary infections with L. lovati and Leucocytozoon sp. during 5- 9 wk of natural exposure, whereas H. mansoni was transmitted during a 2-3-wk period. Relapse infections of Leucocytozoon sp. and L. lovati in wild blue grouse had constant monthly prevalences (percent infected) and intensities (mean number of parasites). In contrast, prev- alence and intensity increased throughout the relapse period for H. mansoni. The patent period in infrapopulations (within one host) of H. mansoni was 5-11 wk for primary, and 11-26 wk for relapse infections. Likewise, peak intensities appeared 1-4 wk after the start of patency for primary and 5-11 wk for relapse infections. No differences were detected in the Leucocytozoon spp. Precise timing and peak intensity was selected for in H. mansoni which had a short transmission period, but not in Leucocytozoon with long transmission periods. Gametocyte production occurs for a longer period during relapse than during the primary period. This satisfies constraints imposed by a pulse vector on parasite transmission to vertebrate hosts. A model is proposed to explain the evolution of the complex intensity patterns observed in H. mansoni.