PubMed Health⌕ Search

Biomedical subjects

C A Farley

Publications and source records attributed to C A Farley.

At least 19 recordsLinked to original sources
PubMed1999

Cryptosporidium oocysts in Bent mussels (Ischadium recurvum) in the Chesapeake Bay.

Filter-feeding molluscan shellfish can concentrate environmentally derived waterborne pathogens of humans, which can be utilized in the sanitary assessment of water quality. In the present study, oocysts of Cryptosporidium were detected in Bent mussels (Ischadium recurvum) at two Chesapeake Bay sites from which C. parvum-contaminated oysters had previously been collected. Spiking of Cryptosporidium-free blue mussel (Mytilus edulis) tissue with C. parvum oocysts showed a 51.1% recovery rate of oocysts, giving an oocyst detection limit of 19 oocysts/0.7 ml of mussel tissue homogenate. The results indicate that Bent mussels, which are common throughout the Chesapeake Bay region, may prove to be useful as biological indicators of water contamination with Cryptosporidium oocysts.

Animals↗
PubMed1998

Survival of infectious Cryptosporidium parvum oocysts in seawater and eastern oysters (Crassostrea virginica) in the Chesapeake Bay.

Oocysts of Cryptosporidium parvum placed in artificial seawater at salinities of 10, 20, and 30 ppt at 10 degrees C and at 10 ppt at 20 degrees C were infectious after 12 weeks. Those placed in seawater at 20 ppt and 30 ppt at 20 degrees C were infectious for 8 and 4 weeks, respectively. These findings suggested that oocysts could survive in estuarine waters long enough to be removed by filter feeders such as oysters. Thereafter, 30 Eastern oysters, Crassostrea virginica, were collected with a dredge or with hand tongs at each of six sites within Maryland tributaries of the Chesapeake Bay in May and June and in August and September of 1997. Hemocytes and gill washings from all oysters were examined for the presence of Cryptosporidium oocysts and Giardia cysts by immunofluorescence microscopy utilizing a commercially available kit containing fluorescein isothiocyanate-conjugated monoclonal antibodies. Giardia was not detected by this method from any of the 360 oysters examined. Presumptive identification of Cryptosporidium oocysts was made in either hemocytes or gill washings of oysters from all six sites both times that surveys were conducted. In addition, during August and September, for each of the six sites, hemocytes from the 30 oysters were pooled and gill washings from the oysters were pooled. Each pool was delivered by gastric intubation to a litter of neonatal mice to produce a bioassay for oocyst infectivity. Intestinal tissue from two of three mice that received gill washings from oysters collected at a site near a large cattle farm and shoreline homes with septic tanks was positive for developmental stages of C. parvum. These findings demonstrate for the first time that oysters in natural waters harbor infectious C. parvum oocysts and can serve as mechanical vectors of this pathogen.

Animals↗
PubMed1998

Giardia sp. cysts and infectious Cryptosporidium parvum oocysts in the feces of migratory Canada geese (Branta canadensis).

Fecal droppings of migratory Canada geese, Branta canadensis, collected from nine sites near the Chesapeake Bay (Maryland), were examined for the presence of Cryptosporidium parvum and Giardia spp. Cryptosporidium sp. oocysts were found in feces at seven of nine sites, and Giardia cysts were found at all nine sites. The oocysts from three sites were infectious for mice and molecularly identified as the zoonotic genotype of Cryptosporidium parvum. Waterfowl can disseminate infectious C. parvum oocysts in the environment.

Animals↗
PubMed1998

Detection of Cryptosporidium oocysts and Giardia cysts in the tissues of eastern oysters (Crassostrea virginica) carrying principal oyster infectious diseases.

The potential cross-reactivity of the combined Cryptosporidium/Giardia direct immunofluorescence antibodies (IFA) of MERIFLUOR and HYDROFLUOR-COMBO tests was examined against tissues containing known developmental stages of 12 pathogens causing the principal infectious diseases in oysters. Spores of Haplosporidium nelsoni and Haplosporidium costale produced positive acid-fast stain (AFS) reactions similar in intensity to Cryptosporidium parvum oocysts. Hexamia nelsoni trophozoites produced positive IFA reactions in both IFA tests; however, the intensity of fluorescence was considerably lower and the fluorescein-staining pattern different than those of Giardia cysts. The applicability of AFS for screening oysters for Cryptosporidium oocysts is low, and positive identification of Cryptosporidium oocysts cannot be accomplished based on the AFS. Presumptive IFA identification of the Cryptosporidium oocysts or Giardia cysts in the oyster tissue should fulfill 3 criteria, i.e., bright-green fluorescence of the same intensity as C. parvum oocysts and Giardia cysts in the positive control, correct size and shape of the fluorescein-stained objects, and oocyst or cyst shell clearly visible.

Animals↗
PubMed1997

Potential Role of the Eastern Oyster, Crassostrea virginica, in the Epidemiology of Cryptosporidium parvum.

Oysters were placed in an aquarium containing artificial seawater, and Cryptosporidium parvum oocysts were added. Oocysts were later found in the gill washings, hemocytes, and gut contents of the oysters. Hemocytes containing oocysts were intubated into four mice. C. parvum stages developed in the ileal epithelia of all of the mice, indicating that the oocysts in the hemocytes remained infective.

Journal Article↗
PubMed1997

In vitro interactions between hemocytes of the eastern oyster, Crassostrea virginica Gmelin, 1791 and Cryptosporidium parvum oocysts.

It was demonstrated by an in vitro slide phagocytosis assay that hemocytes of the Eastern oyster, Crassostrea virginica Gmelin, 1791 are capable of rapid recognition and internalization of infectious Cryptosporidium parvum (AUCP-1 strain) oocysts. The incubation of hemocyte monolayers (8.5 x 10(4) cells) that had received 6.8 x 10(5) or 3.4 x 10(5) oocysts was arrested at 5, 15, 30, 60, 90, and 120 min and the oocytes detected by acid-fast stain and immunofluorescent antibody (IFAT). An average of 20.5, 38.3, 50.2, 58.9, 69.0, and 75.0% oocysts were phagocytosed after 5, 15, 30, 60, 90, and 120 min, respectively. The intensity of fluorescence of phagocytosed oocysts significantly decreased over time (P < 0.01), and their round shape was altered. The number of cells containing oocysts and the mean number of ingested oocysts (range: 1.2-4.5 per cell) increased significantly over time (P < 0.01), whereas the numbers of nonphagocytosed oocysts that were adherent to the glass slides significantly decreased (P < 0.05). By extrapolation, the results indicate that Cr. virginica is capable of internalizing up to 6.4 x 10(6) Cryptosporidium oocysts per ml of its hemolymph.

Analysis of Variance↗
PubMed1991

Epizootiology and distribution of transmissible sarcoma in Maryland softshell clams, Mya arenaria, 1984-1988.

Seasonal and geographic studies of transmissible sarcoma in Maryland softshell clams, Mya arenaria, were carried out from 1984 to 1988. Three major epizootics occurred in our sampling location during this time, resulting in prevalences as high as 90%, with comparable mortalities in other high prevalence areas. The disease invaded populations of large adult clams first, later spreading to the small juvenile clam populations. An apparent 2-year cycle was noted with varying seasonal effects. Affected sites tended to be in the main stem of Chesapeake Bay north of Tangier Sound, primarily in the areas where the major harvesting occurs. Several sites, mostly in upstream locations, were consistently free of disease. The epizootiological study supports the interpretation that the disease is infectious exclusively to this species. Regression analysis between sarcoma prevalence and contaminant levels in clam tissues showed a significant correlation (p = 0.0001) between chlordane levels and this disease. No correlations were found with other contaminants that were analyzed.

Animals↗
PubMed1975

Epizootic and enzootic aspects of Minchinia nelsoni (Haplosporida) disease in Maryland oysters.

Minichinia nelsoni disease in oysters (Crassostrea virginica) from Marumsco Bar, Pocomoke Sound, Maryland (an estuarine tributary of Chesapeake Bay) was studied for 8 years (1961-68) to determine epizootiologic relationships concerning life cycle of the parasite, pathologic effects on the host, and effects of physical factors on population density and recruitment of the host and parasite. The study period covered pre-epizootic, epizootic, and post-epizootic disease conditions. Data on the native oyster population as well as annual introductions of previously unexposed, susceptible populations of juvenile oysters from 1965-68 were included. Salinity, water temperature, mortality, prevalence, incidence, life cycle stages, gross pathology, and histopathologic relationships were observed. Mortality was high (45-55% per year) during the first 3 years of the study; however, M. nelsoni prevalences were low (less than 25%) and did not clearly imply a cause and effect relationship. Drought conditions that began in the summer of 1963 and continued through 1967 caused higher salinities, and apparently initiated epizootic disease in the native oyster populations. The epizootic peaked in May 1965 with a diagnosed prevalence in native oysters of 70%. Enzootic levels of annual mortality (40% in 1966, 30% in 1967, and 2% in 1968) and fall prevalence (16%, 24%, and 4%) developed after that time. Introduced populations had a typical epizootiologic pattern in 1965 55% annual mortality, 82% incidence) and 1966 (55% annual mortality, 66% incidence) which declined in 1967 (30% annual mortality, 44% incidence) followed by a disappearance of the disease in 1968. Epizootiologic differences noted between native oysters (adult and juvenile) and the introduced juvenile populations were also evident from the stages of the disease. Infections in native animals tended to be less serious, and in many cases were delayed or attentuated, while infections in introduced oysters progressed to advanced or terminal phases. Occult manifestations (mantle recession thought to be due to M. nelsoni in oysters not showing histologic evidence of infection) were absent in introduced populations and common in the native population. These differences are interpreted as evidence of resistance in surviving native oysters and their progency, and may indicate genetic resistance developed by natural selection and manifested by an increased ability to survive and overcome infection.

Animal Diseases↗
PubMed1972

Oyster herpes-type virus.

A herpes-type virus infection, the first to be found in an invertebrate animal, is reported in the oyster Crassostrea virginica. Intranuclear herpes-type viral inclusions were more prevalent in the oyster at elevated water temperatures of 28 degrees to 30 degrees C than at normal ambient temperatures of 18 degrees to 20 degrees C. The inclusions were associated with a lethal disease at the elevated temperatures.

Animals↗
PubMed1966

Sporulation of Minchinia nelsoni (Haplosporida, Haplosporidiidae) in Crassostrea virginica (Gmelin).

Minchinia nelsoni, which Haskin, Stauber, and Mackin found in connective tissue and-digestive diverticula of the American oyster, is characterized by a distinct peripheral endosome in its plasmodial and spore nuclei and by spores of unique dimension (7.5 by 5.4 micro) This species is believed to be the etiologic agent, formerly reported as "MSX," responsible for extensive oyster mortalities along the Middle Atlantic Coast.

Animals↗