It takes at least two: male partner factors, racial/ethnic disparity, and Chlamydia trachomatis among pregnant women.

Chlamydia trachomatis (CT), the most prevalent sexually transmitted infection in the United States, disproportionately infects women and people of color. This study aimed to identify risk factors for racial and ethnic disparities for CT infection, re-infection, and persistent infection among pregnant women. We present a secondary analysis of births from a retrospective cohort study in Syracuse, NY from January 2000 through March 2002. African American women [OR 3.35 CI (2.29, 4.92)], Latin American women [OR 4.35 CI (2.52, 7.48)], unmarried women [OR 7.57 CI (4.38, 13.10)], and teen mothers [OR 3.87 CI (2.91, 5.16)] demonstrated statistically significant increased risk for infection. In multivariate analyses that included male partner variables, father's race/ethnicity but not the mother's race/ethnicity remained statistically associated with CT. Despite near universal rates of screening pregnant women, challenges to CT control remain and reflect barriers to testing and treatment of male partners.

Regulation of intertidal food webs by avian predators on New England rocky shores.

Although there is a large body of research on food webs in rocky intertidal communities, most of the emphasis has been on the marine benthic components. Effects of avian predation on highly mobile predators such as crabs, remains practically unstudied in rocky shore ecosystems. The crab, Cancer borealis, is an important component of the diet of gulls (Larus marinus, L. argentatus) at the Isles of Shoals, Maine, USA. C. borealis prey include the predatory gastropod Nucella lapillus L., the herbivore Littorina littorea, and mussels Mytilus edulis L. We hypothesized that gulls reduce abundance of C. borealis in the low intertidal and shallow subtidal, thereby allowing C. borealis prey to persist in high numbers. A study of crab tidal migration showed that C. borealis density nearly doubled at high tide compared to low tide; thus, crabs from a large subtidal source population migrate into the intertidal zone during high tides and either emigrate or are removed by gulls during low tides. Results from a small-scale (1 m2) predator caging experiment in the low intertidal zone indicated that enclosed crabs significantly reduced L. littorea abundance when protected from gull predation. In a much larger-scale gull exclusion experiment, densities of C. borealis increased significantly during low and high tides in exclosures relative to the controls. C. borealis density was inversely correlated with changes in the abundance of two mesopredators Carcinus maenas and Nucella lapillus, and with the space-occupier M. edulis. There was a similar negative correlation between abundance of C. borealis and the change in abundance of the herbivore L. littorea, but the trend was not significant. Mortality of tethered L. littorea was associated with C. borealis density across sites. However, preferred algae did not change in response to L. littorea density during the experiment. Thus, we found suggestive, but not conclusive, evidence for a three-level cascade involving gulls, crabs, and L. littorea. Our studies strongly suggest that gulls, as apex predators, generate three-level trophic cascades in rocky intertidal food webs by preventing the highly mobile subtidal predator, C. borealis, from establishing substantial populations in the low-mid intertidal zone thereby indirectly enhancing densities of two key mesopredators (N. lapillus, Carcinus) and blue mussels (M. edulis).