Malaria Parasites: Ecology and Evolution
The Schall Lab at the University of Vermont

Jos. J Schall
Department of Biology
University of Vermont
Burlington, VT 05405
Since 1978, J. J. Schall and his students have explored the biology of malaria parasites, with studies of species that exploit reptiles and birds as their vertebrate hosts. Sites for the study of lizard malaria parasites include a long-term project at the UC Hopland Research and Extension Center, near the town of Hopland in Mendocino County California; the Long-Term Ecological Research site at El Verde in eastern Puerto Rico; and the tiny Caribbean islands of Saba and St. Martin. A major project was done years ago in Sierra Leone, west Africa. The Lesser Antilles have provided an excellent system for studies in the biogeography and phylogeography of lizard malaria in Anolis. Vermont, California, and other sites were surveyed for malaria parasites in a diverse range of avian taxa.

The first goal of the overall project was to determine the virulence of Plasmodium in lizard hosts, in which an inventory was made of the full range of pathology and reproductive costs of P. mexicanum for fence lizards at Hopland and three Plasmodium species infecting the endemic anole of Saba. Other studies pursued long-term trends in prevalence at three sites, the dynamics of natural and induced infections, transmission biology and vector ecology at Hopland, and the life history traits of the parasite, including the gametocyte sex ratio.

The powerful techniques of molecular biology have opened important lines of investigation over the past decade. The systematics of malaria parasites was studied, resulting in the largest molecular phylogeny ever presented, and the phylogenetic approach allowed an understanding of the biogeography of the parasites across the Caribbean islands. A set of variable genetic markers (microsatellites) for P. mexicanum have been characterized, and ongoing studies examine the clonal diversity of infections, effect of clonal diversity on the parasite's life history and virulence, and relative proportion of clones within individual infections over time. Blood samples collected from infections for more than 30 years at Hopland are used to follow changes in the genetic makeup of the parasite over time.

The power of an evolutionary theory of sex ratios allows a new look at the life cycle of the parasite, using a combination of molecular techniques (microsatellite markers to determine number and relative proportion of clones within the vertebrate host), experimental manipulation of infections, field work, and classical parasitology (microscope duties).

This site provides details on techniques, a list of publications resulting from the studies, and photographic albums of the parasites of lizards. Information on the current lab group and previous students and their projects is also given.