Publications

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field testing of prophylactic measures against cryptosporidium parvum infection in calves in a california dairy herd.to test the ability of oral vaccination or probiotic treatment with lactic acid-producing bacteria to protect calves from cryptosporidium parvum infection under field conditions.19968915434
the prevalence of shedding of cryptosporidium and giardia spp. based on a single fecal sample collection from each of 91 horses used for backcountry recreation.cryptosporidium parvum and giardia duodenalis are now recognized as primary enteric pathogens in animals and humans. regulatory agencies, such as the environmental protection agency are under increasing pressure to reduce the concentration of these protozoa in surface waters. given the popularity of recreational riding of horses on public land in california backcountry, concerns have been raised by various regulatory agencies as to whether horses used for backcountry recreation are a significant ...19979087926
prevalence of and associated risk factors for shedding cryptosporidium parvum oocysts and giardia cysts within feral pig populations in california.populations of feral pigs (sus scrofa) may serve as an environmental reservoir of cryptosporidium parvum oocysts and giardia sp. cysts for source water. we conducted a cross-sectional study to determine the prevalence of and associated demographic and environmental risk factors for the shedding of c. parvum oocysts and giardia sp. cysts. feral pigs were either live-trapped or dispatched from 10 populations located along the coastal mountains of western california, and fecal samples were obtained ...19979327560
dna sequence similarity between california isolates of cryptosporidium parvum.we evaluated whether nucleic acid amplification with primers specific for cryptosporidium parvum followed by automated dna sequence analysis of the pcr amplicons could differentiate between california isolates of c. parvum obtained from livestock, humans, and feral pigs. almost complete sequence identity existed among the livestock isolates and between the livestock and human isolates. dna sequences from feral pig isolates differed from those from livestock and humans by 1.0 to 1.2%. the referen ...19989546195
evaluation of periparturient dairy cows and contact surfaces as a reservoir of cryptosporidium parvum for calfhood infection.to determine whether periparturient cows or contact surfaces to which newborn calves are exposed are reservoirs of cryptosporidium parvum oocysts.19989736387
age, geographic, and temporal distribution of fecal shedding of cryptosporidium parvum oocysts in cow-calf herds.to evaluate fecal shedding of cryptosporidium parvum from california cow-calf herds with respect to age, geographic region, temporal effects, and association with watery feces.199910211683
association of herd composition, stocking rate, and duration of calving season with fecal shedding of cryptosporidium parvum oocysts in beef herds.to evaluate the association of herd demographics, parturition variables, stocking rate, and rotational grazing practices with the probability of fecal shedding of cryptosporidium parvum from beef cow-calf herds in california.199910613218
cross-sectional study of faecal shedding of giardia duodenalis and cryptosporidium parvum among packstock in the sierra nevada range.faecal specimens from 305 horses and mules used as packstock at one of 17 commercial or governmental (national park service, us forest service) operations were examined for giardia duodenalis and cryptosporidium parvum using immunofluorescent microscopy. fourteen packstock (4.6%) were shedding g. duodenalis cysts, with herd-level prevalences ranging 0-22%. number of packstock in the corral, size of corral and density of packstock in the corral were associated with the odds of shedding g. duodena ...200010836481
active, multisite, laboratory-based surveillance for cryptosporidium parvum.cryptosporidium parvum leaped to the attention of the united states following the 1993 outbreak in milwaukee, wisconsin, which sickened 400,000 people. other outbreaks in the united states have been associated with drinking and recreational water, consumption of contaminated foods, contact with animals, and childcare attendance. despite its public health importance, the number of people who become infected each year is not known. in 1997, active surveillance for c. parvum was added to the foodbo ...200011037779
recovery of cryptosporidium oocysts and giardia cysts from source water concentrates using immunomagnetic separation.immunomagnetic separation (ims) procedures for the simultaneous isolation of cryptosporidium oocysts and giardia cysts have recently become available. we validated dynal's gc-combo ims kit using source water at three turbidity levels (5000, 500 and 50 nephelometric turbidity units [ntu]) obtained from different geographical locations and spiked with approximately 9--11 (oo)cysts per ml. mean recoveries of cryptosporidium oocysts and giardia cysts in deionized water were 62% and 69%, respectively ...200111311391
fecal shedding of giardia duodenalis, cryptosporidium parvum, salmonella organisms, and escherichia coli o157:h7 from llamas in california.to evaluate fecal shedding of giardia duodenalis, cryptosporidium parvum, salmonella organisms, and escherichia coli o157:h7 from llamas in california with respect to host factors and management practices.200111327478
incoming ntz blocked by us customs. people with aids health group.u.s. customs in chula vista, california, seized an incoming shipment of nitrazoxanide (ntz), the first drug that shows promise against cryptosporidium parvum infection in people living with hiv/aids. cryptosporidiosis is a source of diarrhea that has resulted in the death of thousands of people with aids. ntz, approved in mexico with a broad anti-parasitic indication, is the first therapy to show effectiveness in more than half the patients treated for cryptosporidiosis. the pwa health group, an ...199611363831
quantitative shedding of two genotypes of cryptosporidium parvum in california ground squirrels (spermophilus beecheyi).sixteen percent of california ground squirrels (spermophilus beecheyi) were found to be shedding an average of 53,875 cryptosporidium parvum oocysts/g of feces. male squirrels had a higher prevalence and higher intensity of shedding than did female squirrels. the majority of c. parvum isolates matched a bovine-murine genotype, with a few isolates resembling a porcine genotype. higher intensities of shedding by males may enhance dissemination and genotypic mixing of this protozoa given males' pro ...200111375204
an examination of risk factors associated with beef cattle shedding pathogens of potential zoonotic concern.the prevalence of three waterborne zoonotic pathogens (campylobacter sp., giardia sp. and cryptosporidium parvum) in rectal faecal samples from a random sample of adult beef cattle was determined. management factors that may be associated with shedding of these organisms were examined. for campylobacter sp. prevalence was 5.0%, and the number of females on the farm was positively associated with the proportion that tested positive. for giardia sp. prevalence was 6.5%, and none of the management ...200111561967
the serologic response to cryptosporidium in hiv-infected persons: implications for epidemiologic research.advances in serologic assays for cryptosporidium parvum have made serology an attractive surveillance tool. the sensitivity, specificity, and predictive value of these new assays for surveillance of immunocompromised populations, however, have not been reported. using stored serum specimens collected for the san francisco men's health study, we conducted a case-control study with 11 clinically confirmed cases of cryptosporidiosis. based on assays using a 27-kda antigen (cp23), the serum specimen ...200111747729
disease reporting from an automated laboratory-based reporting system to a state health department via local county health departments.the authors assessed the completeness of disease reporting from a managed care organization's automated laboratory-based reporting system to the california department of health services (cdhs) via local public health departments.200112034915
endemic cryptosporidiosis and exposure to municipal tap water in persons with acquired immunodeficiency syndrome (aids): a case-control study.in persons with acquired immunodeficiency syndrome (aids), cryptosporidium parvum causes a prolonged, severe diarrheal illness to which there is no effective treatment, and the risk of developing cryptosporidiosis from drinking tap water in non-outbreak settings remains uncertain. to test the hypothesis that drinking tap water was associated with developing cryptosporidiosis, we conducted a matched case-control study among persons with aids in san francisco.200312515584
seasonal shedding of multiple cryptosporidium genotypes in california ground squirrels (spermophilus beecheyi).twelve percent of 853 california ground squirrels (spermophilus beecheyi) from six different geographic locations in kern county, calif., were found to be shedding on average 44,482 oocysts g of feces(-1). the mean annual environmental loading rate of cryptosporidium oocysts was 57,882 oocysts squirrel(-1) day(-1), with seasonal patterns of fecal shedding ranging from <10,000 oocysts squirrel(-1) day(-1) in fall, winter, and spring to levels of 2 x 10(5) oocysts squirrel(-1) day(-1) in summer. j ...200415528541
clams (corbicula fluminea) as bioindicators of fecal contamination with cryptosporidium and giardia spp. in freshwater ecosystems in california.this study evaluated clams as bioindicators of fecal protozoan contamination using three approaches: (i) clam tissue spiking experiments to compare several detection techniques; (ii) clam tank exposure experiments to evaluate clams that had filtered cryptosporidium oocysts from inoculated water under a range of simulated environmental conditions; (iii) sentinel clam outplanting to assess the distribution and magnitude of fecal contamination in three riverine systems in california. our spiking an ...200515862580
new genotypes and factors associated with cryptosporidium detection in mussels (mytilus spp.) along the california coast.a 3 year study was conducted to evaluate mussels as bioindicators of faecal contamination in coastal ecosystems of california. haemolymph samples from 4680 mussels (mytilus spp.) were tested for cryptosporidium genotypes using pcr amplification and dna sequence analysis. our hypotheses were that mussels collected from sites near livestock runoff or human sewage outflow would be more likely to contain the faecal pathogen cryptosporidium than mussels collected distant to these sites, and that the ...200515993883
seasonal temperature fluctuations induces rapid inactivation of cryptosporidium parvum.this study measured the inactivation rate of bovine genotype a cryptosporidium parvum oocysts attributable to diurnal oscillations of ambient temperature and solar radiation typical of california rangelands and dairies from spring through autumn. we first measured the relationship between air temperature and the internal temperature of bovine feces exposed to sunlight on commercial operations throughout california. once maximum air temperature exceeded the mid 20 degrees c, diurnal thermal regim ...200516047784
environmental load of cryptosporidium parvum oocysts from cattle manure in feedlots from the central and western united states.the first step in assessing the risk of water contamination by cryptosporidium parvum oocysts from feedlot cattle (bos taurus) production systems is to quantify the number of c. parvum oocysts present in the fecal material deposited by feedlot cattle. our primary objective for this project was to estimate the daily environmental load of c. parvum oocysts in fecal material deposited by feedlot cattle from across the central and western usa. our secondary goal was to genotype isolates of c. parvum ...200616391291
influence of organic carbon loading, sediment associated metal oxide content and sediment grain size distributions upon cryptosporidium parvum removal during riverbank filtration operations, sonoma county, ca.this study assessed the efficacy for removing cryptosporidium parvum oocysts of poorly sorted, fe- and al-rich, subsurface sediments collected from 0.9 to 4.9 and 1.7-13.9 m below land surface at an operating riverbank filtration (rbf) site (russian river, sonoma county, ca). both formaldehyde-killed oocysts and oocyst-sized (3 microm) microspheres were employed in sediment-packed flow-through and static columns. the degree of surface coverage of metal oxides on sediment grain surfaces correlate ...201020116824
estimating environmental conditions affecting protozoal pathogen removal in surface water wetland systems using a multi-scale, model-based approach.cryptosporidium parvum, giardia lamblia, and toxoplasma gondii are waterborne protozoal pathogens distributed worldwide and empirical evidence suggests that wetlands reduce the concentrations of these pathogens under certain environmental conditions. the goal of this study was to evaluate how protozoal removal in surface water is affected by the water temperature, turbidity, salinity, and vegetation cover of wetlands in the monterey bay region of california. to examine how protozoal removal was ...201425016109
the development and implementation of a method using blue mussels (mytilus spp.) as biosentinels of cryptosporidium spp. and toxoplasma gondii contamination in marine aquatic environments.surveillance monitoring for microbial water quality typically involves collecting single discrete grab samples for analyzing only one contaminant. while informative, current approaches suffer from poor recoveries and only provide a limited snapshot of the microbial contaminants only at the time of collection. to overcome these limitations, bivalves have been proposed as effective biosentinels of water quality particularly for their ability to efficiently concentrate and retain microbial contamin ...201526358104
effects of sediment-associated extractable metals, degree of sediment grain sorting, and dissolved organic carbon upon cryptosporidium parvum removal and transport within riverbank filtration sediments, sonoma county, california.oocysts of the protozoan pathogen cryptosporidium parvum are of particular concern for riverbank filtration (rbf) operations because of their persistence, ubiquity, and resistance to chlorine disinfection. at the russian river rbf site (sonoma county, ca), transport of c. parvum oocysts and oocyst-sized (3 μm) carboxylate-modified microspheres through poorly sorted (sorting indices, σ(1), up to 3.0) and geochemically heterogeneous sediments collected between 2 and 25 m below land surface (bls) w ...201121634424
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