Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids.

Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

Breast cancer and aging: results of the U13 conference breast cancer panel.

Breast cancer is predominantly a disease of older women, yet there is a knowledge gap due to the persisting misalignment between the age distribution of women with breast cancer and the age distribution of participants in clinical trials. The purpose of this report is to state the U13 conference breast cancer panel's recommendations regarding therapeutic clinical trials that will fill gaps in knowledge regarding the care of older patients with breast cancer. The U13 conference was a collaboration between the Cancer and Aging Research Group and the National Institute on Aging and the National Cancer Institute (NCI). Clinical trials should be developed for frail and vulnerable patients who would not enroll on the standard phase III trials, as well as efforts need to be made to increase enrollment of fit older patients on standard phase III trials. As a result of this conference, panel members are working with the NCI and cooperative groups to address these knowledge gaps. With the aging population and increasing incidence of breast cancer with age, it is essential to study the feasibility, toxicity, and efficacy of cancer therapy in this at-risk population.