Gastrointestinal and respiratory tract symptoms following brief environmental exposure to aerosols during a pfiesteria-related fish kill

Assessing the Biological Safety Profession's Evaluation and Control of Risks Associated with the Field Collection of Potentially Infectious Specimens

Because the origins of the biological safety profession are rooted in the control and prevention of laboratory-associated infections, the vocation focuses primarily on the safe handling of specimens within the laboratory. But in many cases, the specimens and samples handled in the lab are originally collected in the field where a broader set of possible exposure considerations may be present, each with varying degrees of controllability. The failure to adequately control the risks associated with collecting biological specimens in the field may result in illness or injury, and could have a direct impact on laboratory safety, if infectious specimens were packaged or transported inappropriately, for example. This study developed a web-based survey distributed to practicing biological safety professionals to determine the prevalence of and extent to which biological safety programs consider and evaluate field collection activities. In cases where such issues were considered, the data collected characterize the types of controls and methods of oversight at the institutional level that are employed. Sixty-one percent (61%) of the survey respondents indicated that research involving the field collection of biological specimens is conducted at their institutions. A majority (79%) of these field collection activities occur at academic institutions. Twenty-seven percent (27%) of respondents indicated that their safety committees do not consider issues related to biological specimens collected in the field, and only 25% with an oversight committee charged to review field collection protocols have generated a field research-specific risk assessment form to facilitate the assembly of pertinent information for a project risk assessment review. The results also indicated that most biosafety professionals (73% overall; 71% from institutions conducting field collection activities) have not been formally trained on the topic, but many (64% overall; 87% from institutions conducting field collection activities) indicated that training on field research safety issues would be helpful, and even more (71% overall; 93% from institutions conducting field collection activities) would consider participation in such a training course. Results obtained from this study can be used to develop a field research safety toolkit and associated training curricula specifically targeted to biological safety professionals.

A probabilistic risk assessment of Cryptosporidium exposure among Baltimore urban anglers

In some urban settings, recreational fishing in industrialized waterways may pose a substantial health risk due to the presence of pathogenic microbes such as Cryptosporidium, a pathogen that produces a moderate to fatal gastrointestinal illness in humans. This pilot study examined the risk of exposure to Cryptosporidium based on fish samples and hand wash samples taken from urban anglers. Information regarding fishing frequency and consumption were also collected through an interview questionnaire to further characterize this risk. There were a total of 56 anglers interviewed and 46 fish and hand wash samples collected (18 hand wash samples and 28 fish samples). It was determined that the mean probability of infection using the U.S. Environmental Protection Agency's (EPA) dose-response model for Cryptosporidium and the fish and hand wash samples was 0.11 and 0.81, respectively. Among the positive fish samples, this mean probability was found to be 0.41. Depending on a variety of confounding factors, such as immunity, pre-existing illnesses and other host specific factors, this probability indicated that on average 1 to 8 out of 10 anglers could become infected. The current fish consumption advisories in Maryland and elsewhere provide no apparent information in regard to any microbiological contaminant. This pilot study provided data for possible modifications and improvements to be made to policy and risk communication regarding the potential health risks due to Cryptosporidium exposure from fishing.

Effect of biotic and abiotic factors on in vitro proliferation, encystment, and excystment of Pfiesteria piscicida

Pfiesteria spp. are mixotrophic armored dinoflagellates populating the Atlantic coastal waters of the United States. They have been a focus of intense research due to their reported association with several fish mortality events. We have now used a clonal culture of Pfiesteria piscicida and several new environmental isolates to describe growth characteristics, feeding, and factors contributing to the encystment and germination of the organism in both laboratory and environmental samples. We also discuss applied methods of detection of the different morphological forms of Pfiesteria in environmental samples. In summary, Pfiesteria, when grown with its algal prey, Rhodomonas sp., presents a typical growth curve with lag, exponential, and stationary phases, followed by encystment. The doubling time in exponential phase is about 12 h. The profiles of proliferation under a standard light cycle and in the dark were similar, although the peak cell densities were markedly lower when cells were grown in the dark. The addition of urea, chicken manure, and soil extracts did not enhance Pfiesteria proliferation, but crude unfiltered spent aquarium water did. Under conditions of food deprivation or cold (4 degrees C), Pfiesteria readily formed harvestable cysts that were further analyzed by PCR and scanning electron microscopy. The germination of Pfiesteria cysts in environmental sediment was enhanced by the presence of live fish: dinospores could be detected 13 to 15 days earlier and reached 5- to 10-times-higher peak cell densities with live fish than with artificial seawater or f/2 medium alone. The addition of ammonia, urea, nitrate, phosphate, or surprisingly, spent fish aquarium water had no effect.

Lack of evidence for contact sensitization by Pfiesteria extract

BACKGROUND

Members of the estuarine dinoflagellate genus Pfiesteria are reported to have been responsible for massive fish kills in the southeastern United States. Some reports suggest that exposure to waters having Pfiesteria blooms or occupation-related exposure might result in Pfiesteria-induced dermal irritation and inflammation. Although the toxin has not been isolated and purified, the original data suggested both hydrophilic and hydrophobic toxic components. Some investigators propose that dermonecrotic properties are associated with a hydrophobic fraction.

OBJECTIVES

A bioactive C18-bound putative toxin (CPE) extracted from Pfiesteria-laden aquarium water during active fish-killing conditions was examined in the present study to evaluate its potential to produce inflammation and dermal sensitization and to determine whether the inflammation and dermatitis reported in early human exposure studies were allergic or irritant in nature.

RESULTS

This fraction was cytotoxic to mouse Neuro-2A cells and primary human epidermal keratinocytes (NHEK) at a concentration of 1 mg/mL. Balb/C mice exposed to 50-200% CPE by skin painting exhibited a 6-10% increase in ear swelling relative to vehicle-treated mice in a primary irritancy assay. There was no increase in lymph node cell proliferation as measured using the local lymph node assay. Exposure to CPE in culture up-regulated interleukin-8 in NHEK, whereas granulocyte macrophage-colony-stimulating factor and tumor necrosis factor alpha were only minimally altered.

CONCLUSIONS

This study suggests that CPE is cytotoxic to keratinocytes in culture at high concentrations and that it induces mild, localized irritation but not dermal sensitization.

Occupational exposure to pfiesteria species in estuarine waters is not a risk factor for illness

BACKGROUND

Exposure to the dinoflagellate Pfiesteria has, under certain circumstances, been associated with deficits in human learning and memory. However, uncertainties remain about the health risk of chronic, low-level exposures (as seen among occupationally exposed commercial fishermen), particularly in light of studies suggesting that Pfiesteria strains are widespread in the estuarine environment in the U.S. mid-Atlantic region.

METHODS

We selected an initial cohort of 152 persons, including 123 persons with regular, occupational exposure to the Chesapeake Bay ; 107 of the cohort members were followed for the full four summer "seasons" of the study. Cohort members were questioned biweekly about symptoms, and data were collected about the areas of the bay in which they worked. These latter data were matched with data on the presence or absence of Pfiesteria in each area, based on polymerase chain reaction analysis of > 3,500 water samples. Cohort members underwent neuropsychological testing at the beginning and end of each summer season.

RESULTS

No correlation was found between work in an area where Pfiesteria was identified and specific symptomatology or changes on neuropsychological tests.

CONCLUSIONS

Although high-level or outbreak-associated exposure to Pfiesteria species (or specific strains within a species) may have an effect on health, routine occupational exposure to estuarine environments in which these organisms are present does not appear to pose a significant health risk.

Chronic biotoxin-associated illness: Multiple-system symptoms, a vision deficit, and effective treatment

Blooms of toxigenic organisms have increased in spatial and temporal extent due to human activities and natural forces that alter ecologic habitats and pollute the environment. In aquatic environments, harmful algal blooms pose a risk for human health, the viability of organisms, and the sustainability of ecosystems. The estuarine dinoflagellate, Pfiesteria piscicida, was discovered in the late 1980s at North Carolina State University as a contaminant in fish cultures. P. piscicida was associated with fish death in laboratory aquaria, and illness among laboratory workers who inhaled the mist above aquaria. Both the fish and humans exhibited signs of toxicity. During the 1990s, large-scale mortality among fish and other aquatic organisms was associated with high concentrations of Pfiesteria sp. in estuaries on the eastern seaboard of North America from New York to Texas. Illness among humans was associated with direct exposure to estuaries and exposures to estuarine aerosols around the time of Pfiesteria-related fish kills. This review of the scientific literature on associations between Pfiesteria and human illness identified some of the possible mechanisms of action by which putative Pfiesteria toxins may have caused morbidity. Particular attention was given to the Pfiesteria-associated, human-illness syndrome known as Possible Estuary Associated Syndrome (PEAS). PEAS was characterized by multiple-system symptoms, deficits in neuropsychological tests of cognitive function, and rapid and severe decrements in visual contrast sensitivity (VCS), an indicator of neurologic function in the visual system. PEAS was diagnosed in acute and chronic illness cases, and was reacquired during re-exposure. Rapid normalization of PEAS signs and symptoms was achieved through the use of cholestyramine therapy. Cholestyramine, a non-absorbable polymer, has been used by humans to lower cholesterol levels since it was approved for that use by the U.S. Food and Drug Administration in 1958. When dissolved in water or juice and taken orally, cholestyramine binds with cholesterol, bile acids, and salts in the intestines, causing them to be eliminated rather than reabsorbed with bile during enterohepatic recirculation. Cholestyramine also has been reported to bind and eliminate a variety of toxic substances. The efficacy of cholestyramine therapy in treatment of PEAS supported the hypothesis that PEAS is a biotoxin-associated illness.

Learning impairment caused by a toxin produced by Pfiesteria piscicida infused into the hippocampus of rats

Pfiesteria piscicida, an estuarine dinoflagellate, which has been shown to kill fish, has also been associated with neurocognitive deficits in humans. With a rat model, we have demonstrated the cause-and-effect relationship between Pfiesteria exposure and learning impairment. In several studies, we have replicated the finding in Sprague-Dawley rats that exposure to fixed acute doses of Pfiesteria cells or filtrates caused radial-arm maze learning impairment. Recently, this finding of Pfiesteria-induced learning impairment in rats has been independently replicated in another laboratory as well. We have demonstrated significant Pfiesteria-induced learning impairment in both the win-shift and repeated-acquisition tasks in the radial-arm maze and in reversal learning in a visual operant signal detection task. These learning impairments have been seen as long as 10 weeks after a single acute exposure to Pfiesteria. In the current study, we used a hydrophilic toxin isolated from clonal P. piscicida cultures (PfTx) and tested its effect when applied locally to the ventral hippocampus on repeated acquisition of rats in the radial-arm maze. Toxin exposure impaired choice accuracy in the radial-arm maze repeated acquisition procedure. The PfTx-induced impairment was seen at the beginning of the session and the early learning deficit was persistent across 6 weeks of testing after a single administration of the toxin. Eventually, with enough practice, in each session, the PfTx-exposed rats did learn that session's problem as did control rats. This model has demonstrated the cause-and-effect relationship between exposure to a hydrophilic toxin produced by P. piscicida and learning impairment, and specifically that the ventral hippocampus was critically involved.

Regulation of translation initiation in mussels (Mytilus galloprovincialis, lam.) following contamination stress

The use of mussels (Mytilus sp.) as bioindicators of the aquatic environment is a valuable approach to monitor environmental contamination. Applying batteries of biomarkers is an essential prerequisite, since the complexity of environmental contaminants can induce in mussels a variety of structural and functional responses, which are not necessarily correlated. In an attempt to correlate translation responses to contamination stress, the sedimentation profiles of runoff ribosomes isolated from digestive gland cells of control or contaminated Mediterranean mussels (Mytilus galloprovincialis, Lam.) were examined and the efficiency of these ribosomes to accomplish protein synthesis was determined. While the major species of ribosomal material was 80S monomers, native 60S and 40S ribosomal subunits were also detected independently of the contamination level in the surrounding waters. However, concomitant with the increase of contamination stress, the level of 80S ribosomes was reduced in favor of free ribosomal subunits. In addition, ribosomes isolated from contaminated mussels and programmed with poly(U) were less efficient to enzymatically bind AcPhe-tRNA, compared with ribosomes from control samples. These results suggest that the contamination stress causes stoichiometric aberrations in the ribosomal particle pool and reduction of translation machinery capability to initate protein synthesis. Data support the notion that downregulation of translation is an important component of the cellular stress response and may be exploited as a biomarker of environmental contamination.

Characterization of the rRNA locus of Pfiesteria piscicida and development of standard and quantitative PCR-based detection assays targeted to the nontranscribed spacer

Pfiesteria piscicida is a heterotrophic dinoflagellate widely distributed along the middle Atlantic shore of the United States and associated with fish kills in the Neuse River (North Carolina) and the Chesapeake Bay (Maryland and Virginia). We constructed a genomic DNA library from clonally cultured P. piscicida and characterized the nontranscribed spacer (NTS), small subunit, internal transcribed spacer 1 (ITS1), 5.8S region, ITS2, and large subunit of the rRNA gene cluster. Based on the P. piscicida ribosomal DNA sequence, we developed a PCR-based detection assay that targets the NTS. The assay specificity was assessed by testing clonal P. piscicida and Pfiesteria shumwayae, 35 additional dinoflagellate species, and algal prey (Rhodomonas sp.). Only P. piscicida and nine presumptive P. piscicida isolates tested positive. All PCR-positive products yielded identical sequences for P. piscicida, suggesting that the PCR-based assay is species specific. The assay can detect a single P. piscicida zoospore in 1 ml of water, 10 resting cysts in 1 g of sediment, or 10 fg of P. piscicida DNA in 1 micro g of heterologous DNA. An internal standard for the PCR assay was constructed to identify potential false-negative results in testing of environmental sediment and water samples and as a competitor for the development of a quantitative competitive PCR assay format. The specificities of both qualitative and quantitative PCR assay formats were validated with >200 environmental samples, and the assays provide simple, rapid, and accurate methods for the assessment of P. piscicida in water and sediments.

Human health effects and Pfiesteria exposure: a synthesis of available clinical data

An association between human illness and exposure to Pfiesteria was first observed among laboratory personnel working with the microorganism. In 1997, in the setting of Pfiesteria activity on the Pocomoke River in Maryland, difficulties with learning and memory were epidemiologically associated with high-level exposure to waterways in which the organism was known to be present. In the Maryland studies, neurocognitive function of affected persons returned to within normal ranges within a period of 3-6 months. Persons with the most severe neurocognitive deficits were significantly more likely to have skin lesions characterized on biopsy by evidence of a toxic/allergic inflammatory reaction. Acute high-level exposures to waterways where Pfiesteria has been identified have been linked with eye and respiratory irritation, headache, and gastrointestinal complaints. Recent data, collected using molecular techniques, suggest that the organism is present in multiple locations in the Chesapeake Bay environment; available data are insufficient to comment on the possible cumulative health impact of chronic low-level environmental exposure to Pfiesteria.