Grantee Research Project Results

ECOHAB: Occurrence of Free-Living Pathogenic Amoebae in Tidal Tributaries of Chesapeake Bay

EPA Grant Number: R827191
Title: ECOHAB: Occurrence of Free-Living Pathogenic Amoebae in Tidal Tributaries of Chesapeake Bay
Investigators: Webb, Stanley R. , Garman, Greg C. , Brown, Bonnie L. , McIninch, Stephen P.
Institution: Virginia Commonwealth University
EPA Project Officer: Packard, Benjamin H
Project Period: July 1, 1998 through December 31, 1999
Project Amount: $54,000
RFA: Ecology and Oceanography of Harmful Algal Blooms (1998) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Harmful Algal Blooms , Water

Description:

We propose a targeted study to investigate an hypothesized role for pathogenic, free-living amoebae (FLPAs) in recent epizootic events involving fish in Chesapeake Bay tributaries and estuaries. Although several of these widely-publicized occurrences during 1997, and particularly in Maryland waters, were probably related to Pfiesteria complex organisms (PCOs), other such events have no apparent link to toxic algae. Preliminary studies by VCU and others have isolated several FLPA taxa, including the genera Naegleria, Vannella, Acanthamoeba, Mayorella, Vahlkamphia, and Hartmannella, from fish lesions and water and sediment samples in Chesapeake Bay tributaries. These initial findings suggest that outbreaks of FLPAs in tidal rivers and estuaries may mimic the effects of HABs on fish and may be initiated by some of the same environmental conditions that are related to HAB events. If true, FLPAs may represent a previously unrecognized agent of fish disease in Atlantic coastal waters. Specifically, the proposed research will 1.) evaluate the temporal and spatial distribution of FLPAs in fishes and other ecological components for major coastal rivers of Virginia; 2.) develop rapid and accurate molecular techniques for the taxonomic identification of selected amoeba genera in environmental samples; and 3.) attempt to correlate environmental parameters, including river physicochemistry with the incidence of fish lesions and FLPAs.

Approach:

During the project period, environmental samples, including water, sediment, and fish will be collected regularly and following established protocols from representative transects (geo-referenced using GPS) in tidal freshwater and oligohaline reaches of Virginia coastal rivers. In addition, any epizootic events involving fish with lesions in Virginia coastal waters will be characterized within 48h of the outbreak. Samples will be screened in the laboratory for the presence of FLPAs and subsamples of any fish exhibiting lesions or other related pathologies will be subjected to detailed analysis. Representative and relatively unbiased sampling of the fish assemblage at each location will be used to quantify the incidence of lesions and of FLPA taxa among resident and migratory fish species. At the time of sampling, a suite of physicochemical and biological parameters (e.g. temperature, dissolved oxygen, fecal coliform bacteria) will be measured at each location. Pathogenic amoebae will be isolated from environmental samples and cultured following published procedures. Amoebae taxa will be identified to the lowest possible level (usually genus) using both morphological (e.g. examination of cysts and trophozoites) and molecular techniques, and identifications will be confirmed by American Type Culture Collection personnel. PCR-based methods (e.g. microsatellites) for the rapid detection of FLPA genera and species in environmental samples will be developed and evaluated for future field testing.

Expected Results:

Findings are expected to contribute to the incomplete understanding of putative Pfiesteria life-history stages, several of which are amoeboid in form and may represent mis-identification of free-living amoebae. The study will also clarify the potential role of FLPAs as fish pathogens in coastal waters and the possible link between environmental conditions, including pollution, and temporal and spatial distribution of FLPAs. Finally, this research expects to develop molecular tools for the rapid identification of pathogenic amoebae in environmental samples.

Supplemental Keywords:

free-living pathogenic amoebae, Naegleria, Vannella, Acanthamoeba, fish lesions, Chesapeake Bay., RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Geographic Area, Water, Waste, algal blooms, Ecological Risk Assessment, State, Chesapeake Bay, Oceanography, Contaminated Sediments, Ecology and Ecosystems, ECOHAB, fish lesions, contaminated sediment, bloom dynamics, coastal habitats, fish kills, tidal tributaries, marine ecosystem, pathogenic amoebae, pfiesteria, taxonomic identification

Progress and Final Reports:

1999

Final