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Objective

To determine whether horses in New York should be vaccinated against equine monocytic ehrlichiosis (EME).

Design

Decision-tree analyses of data from a cross-sectional study and a case-control study.

Sample Population

Horses in New York.

Procedure

Annual expected monetary loss per horse attributable to EME was calculated for vaccinated and nonvaccinated horses in New York. Because risk of being seropositive was dependent on county in which the horse was located, farm elevation, and use of each horse, decision-tree analyses were stratified by these factors.

Results

Annual expected monetary loss per horse attributable to EME for horses vaccinated by veterinarians ranged from $21 to $21.83/horse/y; for horses vaccinated by owners ranged from $10 to $10.83/horse/y; and for nonvaccinated horses ranged from $0 to $4.03/horse/y. Assuming 78% of vaccinated horses were protected and mean losses associated with EME included costs for horses that died, annual incidence density at which expected monetary loss for vaccinated horses was equal to that for nonvaccinated horses was 12 cases/1,000 horses/y and 25 cases/1,000 horses/y for horses vaccinated by owners or by veterinarians, respectively.

Clinical Implications

Annual vaccination minimizes monetary losses attributable to EME only when the annual incidence density exceeds 12 to 25 cases/1,000 horses/y. In New York, expected monetary losses are minimized when horses are not vaccinated because of the low annual incidence density in most regions. (J Am Vet Med Assoc 1996;208: 1290–1294)

Free access
in Journal of the American Veterinary Medical Association

Objective

To determine whether preferentially vaccinated horses were at risk for exposure to Ehrlichia risticii, whether horses with equine monocytic ehrlichiosis (EME) were likely to have been nonvaccinated, and whether clinical severity and financial costs associated with care and treatment of EME were less for vaccinated horses with EME than for nonvaccinated horses with EME.

Design

Cross-sectional and case-control studies.

Procedure

Information on usage of E risticii bacterins to control EME was collected for 2,587 horses located on 511 farms throughout New York. Each horse was tested for serum antibodies directed against E risticii. Data on efficacy of vaccination to reduce the prevalence and clinical severity of EME and monetary losses associated with EME were collected from 68 horses with EME and 132 clinically normal horses.

Results

A correlation was not detected between the county seropositive proportion and the proportion of horses vaccinated against EME. Among horses diagnosed for EME, median date of diagnosis was not delayed for vaccinated horses, compared with that for nonvaccinated horses. Mean cost per case was not significantly different for nonvaccinated horses, compared with that for vaccinated horses ($1,082 and $1,001, respectively). Vaccination was not associated with a reduction in prevalence or in severity of EME-related clinical signs.

Clinical Implications

Administering killed E risticii bacterin once a year to control EME in New York appears to have limited success. Among horses in which EME was diagnosed, severity of illness and financial costs attributable to EME were indistinguishable for vaccinated and nonvaccinated horses. (J Am Vet Med Assoc 1996;208: 1285–1289)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate seasonal patterns and risk factors for Escherichia coli O157:H7 in feces in a beef cattle herd and determine strain diversity and transition in E coli over time by use of multiple-locus variable-number tandem-repeat analysis (MLVA) and pulsed-field gel electrophoresis (PFGE).

Sample Population—456 samples of freshly passed feces collected over a 1-year period from cattle in a range-based cow-calf operation located in the foothills of the Sierra Nevada Mountains in California.

Procedures— E coli O157:H7 was recovered from feces by use of immunomagnetic separation and 2 selective media. Virulence factors were detected via reverse transcriptase-PCR assay. Escherichia coli O157:H7 isolates were subtyped with MLVA and PFGE. Prevalence estimates were calculated and significant risk factors determined. A dendrogram was constructed on the basis of results of MLVA typing.

Results—Overall prevalence estimate for E coli O157:H7 was 10.5%, with the prevalence lowest during the winter. Mean temperature during the 30 days before collection of samples was significantly associated with prevalence of E coli O157:H7 in feces. Nineteen MLVA and 12 PFGE types were identified.

Conclusions and Clinical Relevance—A seasonal pattern was detected for prevalence of E coli O157:H7 in feces collected from beef cattle in California. Subtyping via MLVA and PFGE revealed a diversity of E coli O157:H7 strains in a cow-calf operation and noteworthy turnover of predominant types. Given the importance of accurately determining sources of contamination in investigations of disease outbreaks in humans, MLVA combined with PFGE should be powerful tools for epidemiologists. (Am J Vet Res 2010;71:1339–1347)

Full access
in American Journal of Veterinary Research

Abstract

Objective—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.

Animals—354 llamas from 33 facilities.

Procedure—Fecal specimens were collected and examined for G duodenalis and C parvum by means of immunofluorescent microscopy. Salmonella organisms were cultured by placing feces into selenite enrichment broth followed by selective media. Escherichia coli O157:H7 was cultured by use of modified tryptocase soy broth followed by sorbitol MacConkey agar, with suspect colonies confirmed by means of immunofluorescent microscopy.

Results—12 of 354 fecal specimens (3.4%) had G duodenalis cysts. Younger llamas (crias) were more likely to be shedding cysts, compared with older llamas. Farm-level factors that increased the risk of shedding were large numbers of yearlings on the property (> 10), smaller pen sizes, large numbers of crias born during the previous year (> 10), and large pen or pasture populations (> 20). None of the 354 fecal specimens had C parvum oocysts. Seventy-six (from 7 facilities) and 192 (from 22 facilities) llamas were tested for Salmonella organisms and E coli O157:H7, respectively. All fecal specimens had negative results for these bacteria.

Conclusion and Clinical Relevance—Shedding of G duodenalis was primarily limited to crias 1 to 4 months old. Llamas from properties with large numbers of crias born in the previous year, resulting in large numbers of yearlings in the current year, were at greater risk of infection. In addition, housing llamas in smaller pens or pastures and managing llamas and crias in large groups also increased the risk of G duodenalis shedding. (Am J Vet Res 2001;62:637–642)

Full access
in American Journal of Veterinary Research

Objective

To determine whether treatment with a commercially available nonspecific immunomodulating biologic product would alter the clinical course of disease in neonatal calves.

Design

Systematically randomized, controlled cohort study.

Animals

200 Holstein bull calves 1 to 5 days old.

Procedure

Assessments were performed that included evaluation of fecal consistency, attitude, appetite, and hydration status. Calves with abnormal results were enrolled in the study. Calves were systematically assigned to control or treatment groups (100 calves/group). Calves in the treatment group were given a single IV injection of the biologic product at the time of enrollment, whereas control calves were not given the product. Calves were assessed daily for 5 days to evaluate fecal consistency, attitude, appetite, hydration status, and rectal temperature. Assessments were made without knowledge of group assignment.

Results

Treatment with the immunomodulating product was not associated with a decrease in the number of calves that had moderate or severe departures from clinically normal conditions for attitude, appetite, or hydration on days 1 though 5, compared with control calves. Fecal consistency scores were significantly greater for treated calves on days 1 (P = 0.03) and 5 (P = 0.02), compared with scores for control calves.

Clinical Implications

Administration of the nonspecific immunomodulating biologic product did not significantly affect outcome of clinical disease for calves in the treated group, compared with calves in the control group. On the basis of results of this study, we cannot recommend use of the nonspecific immunomodulating biologic product for the treatment of undifferentiated diarrheal disease in neonatal calves. (J Am Vet Med Assoc 1998;213:1308-1311)

Free access
in Journal of the American Veterinary Medical Association

Objective

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.

Design

Cross-sectional study.

Sample Population

38 beef cow-calf operations.

Procedure

Fecal specimens were collected and examined for C parvum oocysts, using immunofluorescent microscopy. Association between various demographic and management factors and the probability of shedding C parvum were statistically evaluated.

Results

Adjusted for age and month of collection of a fecal sample, cattle from herds with a high number of young calves (≤ 2 months old) on the day of sample collection, a high stocking rate (No. of cattle/acre/mo), or a longer calving season were more likely to shed C parvum oocysts, compared with cattle from herds with fewer young calves, a lower stocking rate, or a shorter calving season. Cattle from herds with a higher number of older calves (> 2 months old) on the day of sample collection were less likely to shed C parvum oocysts, compared with cattle from herds with fewer older calves. Using our multivariate model, rotational grazing systems or season of onset of calving were not associated with shedding status for C parvum oocysts.

Conclusions and Clinical Relevance

Reproductive management that would result in a shorter calving season and use of a lower stocking rate for cattle may be associated with reduced risk of C parvum shedding. Intensive rotational grazing systems and time of year for onset of calving season apparently have little effect on reducing prevalence of oocyst shedding. (J Am Vet Med Assoc 1999;215:1833–1838)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine whether mean annual frequency and destination of equine travel was associated with exposure to Ehrlichia risticii and whether these associations were modified by horses’ place of residence.

Design

Cross-sectional study.

Sample Population

511 equine operations containing 2,587 horses were visited in New York state from a target population of 39,000 operations.

Procedure

Each horse was tested for serum antibodies against E risticii, using indirect fluorescent antibody. Information on the horse's travel history, farm's management practices, and surrounding ecology was obtained by personal interview and resource maps. Statistical analyses were performed on 2 cohorts of animals: all horses enrolled in the study and horses born on the property or that resided at least 4 years on the farm. Three countybased risk regions (RR) were identified by use of cluster analysis.

Results

Mean seroprevalence for each of the 3 RR was 2.4 (low risk), 8.5 (moderate risk), and 18.5% (high risk) for cohort 1 and 2.5, 8.0, and 18.4% for cohort 2. Among cohorts 1 and 2, pleasure riding and breeding trips were associated with exposure to E risticii, but horse residence (low, moderate, or high RR) was an effect modifier for these associations. Among cohort 1 and stratifying the analysis according to the RR for the travel destination, trail riding at low RR and trail riding at high RR were associated with exposure. Among cohort 2 and stratifying the analysis according to the RR for the travel destination, breeding trips were associated with exposure, and strong effect modification was present for horse residence (low, moderate, or high RR).

Conclusions

Only certain types of travel to specific RR were associated with higher risk of exposure to E risticii. In many instances, travel was not associated, or was associated, with a reduced risk of exposure.(Am J Vet Res 1996; 57: 272-277)

Free access
in American Journal of Veterinary Research

SUMMARY

A retrospective study was designed to determine the distribution of equine monocytic ehrlichiosis among the equine population in New York state, and to identify factors associated with risk of disease. Serum samples submitted to the diagnostic laboratory of the university during the period from January 1985 through December 1986 were examined for antibodies to Ehrlichia risticii, using the indirect fluorescent antibody technique. Factors evaluated included geographic origin and date of submission of the sample, and age, breed, and sex of the horse. Logistic regression analysis was used to identify which factors were significantly associated with the risk of seropositivity to E risticii, while simultaneously controlling for other factors.

Of the 2,579 tested samples, 1,950 (76%) had positive results. Factors significantly associated with risk of seropositivity to E risticii were: breed of the horse (Thoroughbreds were 3 times more likely to have been exposed to E risticii, compared with non-Standardbred, non-Thoroughbred breeds); sex (female horses were 2.7 times more likely to have been exposed, compared with male horses); age of the horse (the risk of being exposed to E risticii increased with age, peaked at around 12 years, and decreased thereafter); and month of submission (horses tested during November and December had the highest odds of being seropositive [odds ratio = 2.1], and horses tested during March through April were least likely to be seropositive [odds ratio = 0.5], compared with horses tested during January and February).

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To locate counties within New York state with a high seroprevalence among the equine population, to determine host, management, and environmental factors that were associated with seropositivity to Ehrlichia risticii, and to determine evidence for arthropod- or helminth-mediated transmission of E risticii to horses.

Design

Cross-sectional study.

Sample Population

A random sample of 3,000 of the 39,000 equine operations in New York state was selected, and 2,587 horses from 511 operations were tested.

Procedure

Blood samples were collected from horses and tested for seropositivity, using the indirect fluorescent antibody technique. Data on each horse and each farm's management were obtained by personal interview. The significance of each factor on the risk of seropositivity was evaluated, using mixed-effect logistic regression.

Results

The seroprevalence among E risticii-nonvaccinated horses was 7.3%. The county-specific seroprevalence ranged from 0 to 27%, with higher-risk counties located at low elevation. Farms at higher risk for having seropositive horses were located predominately at low elevation with no bodies of water nearby.

Risk of seropositivity was associated with time spent in a stall or run-in shed, with frequency of application of fly spray, and, depending on duration of residency at the farm, with frequency of deworming with benzimidazole and pyrantel. Standardbreds were 2 to 3 times more likely to have been exposed, compared with Thoroughbreds. Depending on duration of residency at the farm, male and middle-age horses were at higher risk.

Up to 32% of the variance for a horse to test seropositive for E risticii on the logit scale was attributable to farm-level random effects, but the nested social group random effect was not significant.

Conclusions

Arthropods and helminths may have a role in the transmission of this disease. Several management factors may directly or indirectly modify the risk of exposure to E risticii, allowing for the possibility of additional control measures besides traditional vaccination strategies.(Am J Vet Res 1996;57:278-285 )

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether sampling feces off the ground replicates prevalence estimates for specific pathogens obtained from fecal samples collected per rectum of adult cows, and to determine characteristics of feces on the ground (fecal pats) that are associated with subsequent identification of Campylobacter spp, Cryptosporidium parvum, and Giardia duodenalis.

Animals

A random sample of adult beef cattle from 25 herds located throughout California.

Procedure

1,115 rectal and ground fecal samples were obtained. Samples were submitted for culture of Campylobacter spp and examined, using a direct fluorescent antibody assay, to detect C parvum oocysts and G duodenalis cysts. Characteristics of fecal pats, such as volume and consistency, were recorded.

Results

Prevalence of Campylobacter spp was 5.0% (20/401) for rectal fecal samples, which was significantly greater than prevalence determined for ground fecal samples (2/402; 0.5%). Most isolates were C jejuni subsp jejuni. Prevalence of C parvum was higher in rectal fecal samples (6/557; 1.1%) than in ground fecal samples (1/558; 0.2%), but this difference was not significant. Prevalence of G duodenalis did not differ for rectal (36/557; 6.5%) versus ground (26/558; 4.7%) fecal samples.

Conclusions and Clinical Relevance

Evaluation of ground fecal samples may not accurately indicate the prevalence of Campylobacter spp or C parvum in cattle but may reflect prevalence of G duodenalis Differences in prevalence estimates between the 2 methods suggest inactivation of pathogens in feces after cattle have defecated. Prevalence estimates generated by evaluation of ground fecal samples, however, may more accurately estimate environmental pathogen burden. (Am J Vet Res 1999;60:1352–1356)

Free access
in American Journal of Veterinary Research