Testing for the potential effects of Karenia brevis on school absences [poster]

Abstract

We analyzed a potential relationship between changes in school absences in Sarasota County and Karenia brevis (Kb) count data. Brevetoxins released during Kb blooms could be a reason for students experiencing increased respiratory or gastrointestinal illnesses, causing an increase in absence rates. We designed a map to relate the locations of Sarasota County schools and the distributions of those Kb counts with a minimum of 10,000 cell counts per liter and above. Due to the proximity of Kb counts, we hypothesized that brevetoxins could have a greater effect on the schools near the coast of Florida rather than the schools inland. Because individuals could be affected by brevetoxins up to several days after being exposed, we expected to find a lagged effect of a bloom occurrence on school absences. Using a regression approach, we were unable to detect an association between Kb counts and student absences. In some cases, the direction of the effects were opposite to what would be expected (i.e., an increase in Kb counts was associated with a reduction in the percent absent rate). The results indicated that over 70% of the variation in the school percent absent rate could be explained by the latent characteristics of individual schools (such as variations in student populations across different schools), by school week, by month (such as the effects of flu outbreaks or and other seasonal factors), and by year.