Cryptosporidium parvum Exposure Associated with Fishing and Crabbing Within The Urban Baltimore Watershed

Authors: Cynthia McOliver, Jennifer Roberts, Thaddeus Graczyk,

and Ellen Silbergeld

Watersheds are used by many populations for fishing, crabbing, and other recreational water activities as well as food supplementation/subsistence. However, urban watersheds not only harbor food organisms such as fish and shellfish, but also pathogenic organisms such as Cryptosporidium parvum (C. parvum). We report on two studies of human contact with the parasite Cryptosporidium parvum, a major cause of waterborne illness in the United States, associated with recreational and subsistence fishing and crabbing in the Baltimore watershed. Cryptosporidium parvum is an anthropozoonotic pathogen associated with substantial morbidity in healthy people and with increased risks of mortality in immunosuppressed populations, including persons with HIV/AIDS. It is a source of concern since there is documented presence in Baltimore’s surface waters, sediments and biota, and because of the high HIV/AIDS prevalence rates in our area. Additionally, there has been extensive and increasing use of the Baltimore Inner Harbor of the Chesapeake Bay and its estuarine tributaries for recreation and fishing. Our first study demonstrated that fishing can be a vector of exposure to pathogens such as Cryptosporidium parvum (Roberts et al 2004, 2006). Urban anglers self-reported demographic information, fishing patterns and locations, fish consumption behaviors, and awareness of fish consumption advisories. We collected samples from the surface of caught fish and from the hands of anglers, and utilized FISH (Fluorescent in situ hybridization) method and immunofluorescent antibodies (IFA) for the identification and viability assessment of Cryptosporidium oocysts in these samples. Ultraviolet light microscopy was used to enumerate oocysts. The second study has been designed to test the hypothesis that fishing, crabbing, and other recreational water use will increase risks of Cryptosporidium exposure in the HIV-positive population in Baltimore. Results from this study will be used to design a cross sectional study of C parvum exposure in the HIV/AIDS population, using molecular serology to determine pathogen exposure. These results will have important public health significance because 1) Cryptosporidium parvum exposure is a major health risk for persons with HIV/AIDS and 2) Sources of Cryptosporidium parvum exposure are largely unknown. Understanding the nature and extent of these fishing-related risks may underpin increased investments in microbial monitoring and in improving water quality.