Distribution and abundance of two malarial parasites of the endemic Anolis lizard of Saba Island, Netherlands Antilles.

The ecology of 2 parasites, Plasmodium floridense and Plasmodium azurophilum, was studied in the endemic lizard, Anolis sabanus, on Saba island in the eastern Caribbean. Prevalence of the two parasite species was similar, but prevalence varied among sites. Lowest prevalence occurred at dry, windy sites or cool, wet mountain peaks (0-20%); the parasites were more common at most other locations on the island (40-80% infected; overall prevalence = 47%). High and low prevalence sites sometimes were only a few hundred meters apart. Prevalence was similar for males and females but increased with body size except for a decline in the largest ( = oldest) lizards. A surplus of mixed infections (P. floridense and P. azurophilum together in the same host) existed compared with chance proportions. Parasitemia generally was low; 70% of P. floridense infections were < or = 100 parasites/10,000 erythrocytes, and 70% of P. azurophilum infections were < or = 50/10,000. Parasitemia in solitary infections averaged more than twice that seen in mixed infections for both species.