The occurrence of subtilase-cytotoxin-encoding genes in environmental Escherichia coli isolated from a Northern California estuary.

The presence of subtilase-cytotoxin-encoding genes was determined in 397 environmental Escherichia coli strains isolated from water, suspended solids, and sediments sampled from different hydrological and environmental conditions in a California estuary. A total of 7 strains (1.76%) were found to harbor subtilase-cytotoxin-encoding genes. Using primers targeting subA only, we generated PCR amplicons from 2 strains; while using primers targeting the 3' end of SubA downstream to the 5' end of SubB, amplicons of 232 bp were generated from 5 additional strains. The 556 bp subA sequences were almost identical to that in the subtilase-cytotoxin-positive strain ED 591 (98%), while subAB sequences of 2 non-Shiga-toxigenic strains revealed 100% similarity with the Shiga-toxigenic E. coli O113:H21 strain 98NK2 that was isolated from an outbreak of hemolytic uremic syndrome. Additionally, the serogroup O113:H21 was present in this collection of environmental E. coli, and it was found to harbor stx2d, hra1 that encodes the heat resistant agglutinin 1, and a subAB sequence similar to that in the non-Shiga-toxigenic E. coli subtilase cytotoxin strain ED 591. To further understand potential health risks posed by strains encoding SubAB, future epidemiological studies should consider screening isolates for subAB regardless of the presence of Shiga-toxin-encoding genes.

Deposition of Cryptosporidium parvum oocysts in porous media: a synthesis of attachment efficiencies measured under varying environmental conditions.

An extensive set of column experiments was performed with freshly harvested Cryptosporidium parvum oocysts to evaluate the effects of solution chemistry, surface coatings, interactions with other suspended particles, and pore fluid velocity on the fate and transport of this widely occurring waterborne pathogen in sandy porous media. We synthesized our data set with a comprehensive literature survey of similar experiments, to compute attachment (collision) efficiencies (α) used in colloid filtration theory (CFT) using three models for the single collector efficiency (η) across a wide range of experimental conditions. Most prior experiments have observed the transport of surface-treated, sterile C. parvum oocyst in porous media. Our column data confirm for freshly harvested oocysts that the presence of iron coatings on the sand medium and the presence of suspended illite clay drastically enhance oocyst deposition. Increasing ionic strength and decreasing pH also systematically enhance the attachment efficiency. Attachment efficiency decreases only at a very high ionic strength, most likely as a result of steric repulsion and possibly other changes in oocyst surface properties. Attachment efficiencies vary with fluid flow rate but without showing specific trends. We found that the computed attachment efficiency across all reported experiments could be reliably estimated using a regression model based on parameters related to ionic strength and pH. The regression model performed better with the Nelson-Ginn η model and Tufenkji-Elimelech η model than with the Rajagopalan-Tien η model. When CFT is used in environmental assessments, the proposed regression model provides a practical estimator for attachment efficiencies of C. parvum oocyst deposition in porous media for a variety of environmental conditions unfavorable to attachment.

Prevalence, distribution, and diversity of Salmonella enterica in a major produce region of California.

A survey was initiated to determine the prevalence of Salmonella enterica in the environment in and around Monterey County, CA, a major agriculture region of the United States. Trypticase soy broth enrichment cultures of samples of soil/sediment (n = 617), water (n = 252), wildlife (n = 476), cattle feces (n = 795), and preharvest lettuce and spinach (n = 261) tested originally for the presence of pathogenic Escherichia coli were kept in frozen storage and later used to test for the presence of S. enterica. A multipathogen oligonucleotide microarray was employed to identify a subset of samples that might contain Salmonella in order to test various culture methods to survey a larger number of samples. Fifty-five of 2,401 (2.3%) samples yielded Salmonella, representing samples obtained from 20 different locations in Monterey and San Benito Counties. Water had the highest percentage of positives (7.1%) among sample types. Wildlife yielded 20 positive samples, the highest number among sample types, with positive samples from birds (n = 105), coyotes (n = 40), deer (n = 104), elk (n = 39), wild pig (n = 41), and skunk (n = 13). Only 16 (2.6%) of the soil/sediment samples tested positive, and none of the produce samples had detectable Salmonella. Sixteen different serotypes were identified among the isolates, including S. enterica serotypes Give, Typhimurium, Montevideo, and Infantis. Fifty-four strains were sensitive to 12 tested antibiotics; one S. Montevideo strain was resistant to streptomycin and gentamicin. Pulsed-field gel electrophoresis (PFGE) analysis of the isolates revealed over 40 different pulsotypes. Several strains were isolated from water, wildlife, or soil over a period of several months, suggesting that they were persistent in this environment.

Risk factors for Toxoplasma gondii infection in wild rodents from central coastal California and a review of T. gondii prevalence in rodents.

Sera from 523 wild rodents were tested for Toxoplasma gondii antibodies using either an indirect fluorescent antibody test (IFAT) (rats and mice, with titer >or=80 considered positive) or a latex agglutination test (LAT) (voles, squirrels, and pocket mice, with titer >or=32 considered positive). Seventeen percent (88/523) of the rodents, including 26% (85/328) of the Peromyscus sp. and 8% (3/37) of Spermophilus beecheyi, were seropositive. Fourteen percent (23/161) of rodents captured in trap sites next to Morro Bay (California) and 15% (16/109) of rodents from sites adjacent to riparian habitats had antibodies to T. gondii, compared to 19% (49/253) of rodents captured in habitats not associated with water; this difference was not statistically significant (P = 0.32). Significantly fewer rodents were captured <200 m from residential housing compared to locations further away (11% vs. 30%, respectively). Factors associated with an increased risk for T. gondii seropositivity in rodents were capture location >or=200 m from residential housing and adult age.

Detection of Toxoplasma gondii-like oocysts in cat feces and estimates of the environmental oocyst burden.

OBJECTIVE: To estimate the analytic sensitivity of microscopic detection of Toxoplasma gondii oocysts and the environmental loading of T gondii oocysts on the basis of prevalence of shedding by owned and unowned cats. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 326 fecal samples from cats. PROCEDURES: Fecal samples were collected from cat shelters, veterinary clinics, cat-owning households, and outdoor locations and tested via ZnSO(4) fecal flotation. RESULTS: Only 3 (0.9%) samples of feces from 326 cats in the Morro Bay area of California contained T gondii-like oocysts. On the basis of the estimated tonnage of cat feces deposited outdoors in this area, the annual burden in the environment was estimated to be 94 to 4,671 oocysts/m(2) (9 to 434 oocysts/ft(2)). CONCLUSIONS AND CLINICAL RELEVANCE: Despite the low prevalence and short duration of T gondii oocyst shedding by cats detected in the present and former surveys, the sheer numbers of oocysts shed by cats during initial infection could lead to substantial environmental contamination. Veterinarians may wish to make cat owners aware of the potential threats to human and wildlife health posed by cats permitted to defecate outdoors.

Evaluation of two Toxoplasma gondii serologic tests used in a serosurvey of domestic cats in California.

We evaluated the sensitivity (Se) and specificity (Sp) of an IgG enzyme-linked immunosorbent assay (ELISA) and IgG indirect fluorescent antibody test (IFAT) for detection of Toxoplasma gondii-specific antibodies in sera from 2 cat populations using a Bayesian approach. Accounting for test covariance, the Se and Sp of the IgG ELISA were estimated to be 92.6% and 96.5%, and those of the IgG IFAT were 81.0% and 93.8%, respectively. Both tests performed poorly in cats experimentally coinfected with feline immunodeficiency virus and T. gondii. Excluding this group, Se and Sp of the ELISA were virtually unchanged (92.3% and 96.4%, respectively), whereas the IFAT Se improved to 94.2% and Sp remained stable at 93.7%. These tests and an IgM ELISA were applied to 123 cat sera from the Morro Bay area, California, where high morbidity and mortality attributable to toxoplasmosis have been detected in southern sea otters. Age-adjusted IgG seroprevalence in this population was estimated to be 29.6%, and it did not differ between owned and unowned cats. Accounting for Se, Sp, and test covariances, age-adjusted seroprevalence was 45.0%. The odds for T. gondii seropositivity were 12.3-fold higher for cats aged >12 mo compared with cats aged <6 mo.

Experimental infection of Peromyscus californicus with Toxoplasma gondii.

Eight female Peromyscus californicus were infected with 10(2) or 10(4) Toxoplasma gondii culture-derived tachyzoites (Type II or X) isolated from southern sea otters. All but 2 mice survived infection and developed antibodies to T. gondii. The 2 fatally infected mice were inoculated with 10(4) tachyzoites of the Type X strain. Parasite detection by immunohistochemistry (IHC) and DNA amplification with 2 polymerase chain reaction (PCR) methods was compared for brain, heart, lung, liver, spleen, biceps muscle, and tongue, at a mean of 41 days postinfection. Parasites were detected most commonly by IHC in spleen (8/8) and brain (6/8). DNA amplification by PCR was most successful from brain, heart, and spleen.

Outdoor fecal deposition by free-roaming cats and attitudes of cat owners and nonowners toward stray pets, wildlife, and water pollution.

OBJECTIVE: To estimate cat population size, management, and outside fecal deposition and evaluate attitudes of cat owners and nonowners to stray animal control, water pollution, and wildlife protection. DESIGN: Cross-sectional survey. SAMPLE POPULATION: 294 adult residents of Cayucos, Los Osos, and Morro Bay, Calif. PROCEDURES: Telephone survey. RESULTS: The region's cat population was estimated at 7,284 owned and 2,046 feral cats, and 38% of surveyed households owned a mean of 1.9 cats/household. Forty-four percent of cats defecated outside >75% of the time. Annual fecal deposition (wet weight) by owned cats in the 3 communities was estimated to be 77.6 tonnes (76.4 tons). Cat owners were more likely to oppose cat licensing and impounding stray cats and support trap-neuter-return for stray cats and less likely to be concerned about water pollution, than were noncat owners. CONCLUSIONS AND CLINICAL RELEVANCE: Feral cats represented a sizeable proportion (22%) of the free roaming cats in this area and could be contributing 30.0 tonnes (29.5 tons) of feces to the environment per year. However, feral cats are not the principal source of fecal loading because owned cats defecating outdoors contribute an estimated 77.6 tonnes (76.4 tons) or 72% of the annual outdoor fecal deposition.

Prophylactic use of decoquinate for infections with Cryptosporidium parvum in experimentally challenged neonatal calves.

OBJECTIVE: To evaluate the effect of daily oral administration of decoquinate to neonatal calves experimentally challenged with various numbers of Cryptosporidium parvum oocysts. DESIGN: Clinical trial. ANIMALS: 75 calves. PROCEDURE: Calves were purchased from a commercial dairy during a 5-week period. Calves were housed in individual hutches and fed milk replacer with or without decoquinate (2 mg/kg [0.9 mg/lb per day]). Calves were randomly assigned to treatment and 1 of 5 challenge groups (0, 50, 100, 1000, or 10,000 C. parvum oocysts in 60 mL of saline [0.9% NaCl] solution administered p.o. on the day after arrival). Calves were maintained in the study for as long as 28 days. Calves were clinically assessed for diarrhea and dehydration. Fecal samples were submitted for oocyst enumeration 3 times each week. RESULTS: Treatment did not affect number of days to first watery feces (diarrhea), number of days to first oocyst shedding, or duration of diarrhea or oocyst shedding. Duration of oocyst shedding was significantly associated with challenge dose of oocysts administered to calves and number of days to first oocyst shedding. Duration of diarrhea and number of days to first oocyst shedding were significantly associated with week of arrival and number of days to first watery diarrhea. CONCLUSIONS AND CLINICAL RELEVANCE: Daily treatment with decoquinate at the dosage used in this study did not affect oocyst shedding or clinical signs associated with cryptosporidiosis. However, there was an indication that if the number of oocysts calves received could be reduced, then the duration of oocyst shedding and, hence, environmental loading of C. parvum oocysts could be reduced.