Contamination of Atlantic coast commercial shellfish with Cryptosporidium

Abstract

Shellfish (oysters and/or clams) were obtained from 37 commercial harvesting sites in 13 Atlantic coast states from Maine to Florida and one site in New Brunswick, Canada. Gill washings from each of 25 shellfish at each site were examined by immunofluorescence microscopy (IFA) for oocysts of Cryptosporidium. Gill washings from another 25 shellfish at each site were grouped into five pools of five shellfish each. DNA from each pool was utilized for PCR and genotyping. Oocysts were found in 3.7% of 925 oysters and clams examined by IFA in shellfish from New Brunswick and 11 of 13 states. Cryptosporidium DNA was detected by PCR in 35.2% of 185 pools. Cryptosporidium parvum genotypes 1 and 2, and Cryptosporidium meleagridis,all of which have been identified in infected humans, were identified at 37.8% of the sites. Gill washings from every site were tested for the presence of infectious oocysts by biological assay in neonatal BALB/c mice but no mice were found infected, suggesting that either the oocysts were no longer infectious or infections in mice were below the level of detection. Collectively, these findings indicate that Cryptosporidium species, indicative of pollution from human and animal feces and potentially infectious for humans, were found in commercial shellfish from 64.9% of sites examined along the Atlantic coast by either microscopy or molecular testing. Previous reports link periods of high rainfall with the elevated numbers of pathogen contaminated shellfish. Because shellfish in the present study were examined during a period of exceptionally low precipitation, the data are thought to underestimate the number of Cryptosporidium contaminated shellfish likely to be found during periods of normal or above normal precipitation.

The effects of precipitation, river discharge, land use and coastal circulation on water quality in coastal Maine

“…Shellfish beds, fish hatcheries and beach systems can be affected by faecal pollution within rivers and the buoyant plumes emanating from those and other sources of freshwater to the coastal ocean [ 3 – 5 ]. The detection of the zoonotic protozoan parasites, Giardia and Cryptosporidium [ 6 , 7 ], and pathogenic bacteria, Campylobacter , Vibrio and Salmonella [ 8 ], in water and bivalve samples from estuarine and coastal locations indicates that faecal pollution and the associated pathogens are emerging coastal public health problems.…”

“…Others have reported the detection of Cryptosporidium spp. in mussels [ 7 ] and oysters [ 6 ] after heavy rainfalls.…”

Mussels ( Perna perna ) as bioindicator of environmental contamination by Cryptosporidium species with zoonotic potential

“…To date, the presence of C . meleagridis in the tissue of marine bivalve mollusks has been reported only by Fayer et al. (2003) , and thus, the present study is the second to describe such occurrence and the first to report the presence of this species in South American shellfish.…”

“…parvum together with C . hominis in gill samples from oysters and mussels ( Fayer et al., 2003 ), although descriptions regarding the identification of C . parvum subtypes are scarce.…”