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1.
A study was undertaken to determine the prevalence of Giardia infections in dairy calves and to compare Giardia and Cryptosporidium infections in calves of different ages. Fresh fecal samples were collected from 386 male and female Holstein calves (newborn to 24 wk) in 20 dairies located in the lower Fraser river valley area of British Columbia. Giardia intestinalis, Cryptosporidium parvum, and Cryptosporidium muris were enumerated in each sample after concentration by sucrose gradient centrifugation and immunofluorescent staining. Giardia was identified at all farm locations. The overall prevalence of Giardia in calves was 73% with a geometric mean cyst count of 1180 cysts per gram of feces (CI, 41 to 5014). Cryptosporidium parvum and C. muris were identified in 80% and 40% of the farms, respectively. The prevalence of C. parvum was 59%, and the geometric mean for oocysts was 457 oocysts per gram of feces (CI, 18 to 160). The prevalence of C. muris was only 2% and the mean oocyst counts were 54 oocysts per gram of feces. Giardiasis was not age dependent, and approximately 80% of the calves from 2 to 24 wk were infected. In contrast, C. parvum infections were predominant in calves 2 to 4 wk, while C. muris was demonstrated in calves older than 4 wk. Fourty-seven percent of calves with diarrhea had high numbers of Giardia cysts in their feces. Giardia infections are highly prevalent in dairy calves and should be considered in animals with diarrhea or failure to thrive.  相似文献   

2.
To determine the prevalence of Giardia genotypes in post-weaned dairy calves, fecal specimens were collected from 3 to 11-month-old dairy calves per farm on two farms in Vermont, New York, Pennsylvania, Maryland, Virginia, North Carolina, and Florida. Specimens cleaned of fecal debris and concentrated using CsCl density gradient centrifugation were stained and examined by immunofluorescence microscopy and also subjected to PCR and DNA sequence analysis. Overall, PCR provided more sensitive detection than IFA. Prevalence of Giardia infection, as detected by PCR ranged from 20% on NC-2 to 81% on VT-2, with an overall prevalence of 52% (237 positive samples out of 456 total). DNA sequence analysis of the 16S rRNA gene revealed 87% of the 237 Giardia isolates were Assemblage E, and 13% were Assemblage A although the prevalence of these genotypes varied greatly from farm to farm, with five farms having no Assemblage A Giardia. Therefore, Assemblage E was present in 45% of all animals tested and Assemblage A was present in 7% of the animals. Thus, while many of the calves were infected with a genotype that is not known to be infectious for humans, post-weaned calves on nine of 14 farms did harbor Assemblage A Giardia. Therefore calves should be considered as a potential source of human infectious cysts in the environment, with some farms representing a much higher risk than others.  相似文献   

3.
Giardia infections in domestic cattle has come under increasing scrutiny owing to the potential contamination of surface and ground waters through manure distribution on fields and pasture runoff. The objective of the study was to determine the prevalence and genotypes of Giardia duodenalis in beef calves in major beef cow calf farms in Alberta, Canada. Fecal samples were collected from beef calves aged 2-10 weeks at nine farms in Alberta. Samples were examined for the presence of G. duodenalis cysts by immunofluorescent staining. Giardia cysts were found in 168 of the 495 fecal samples examined, with prevalence ranging from 7 to 60% among farms. Genotypic analysis of positive isolates utilizing PCR and sequencing of a 292 bp fragment of the 16S-rRNA locus, revealed the hoofed livestock genotype in 41 of the 42 isolates. One isolate was identical to the Assemblage A genotype. The results of this study demonstrate that beef calves in this area are primarily infected with the livestock genotype which is thought to be specific to artiodactyl hosts and non-infective to humans. This suggests that the Giardia carried by beef cattle may be a minimal zoonotic threat.  相似文献   

4.
To determine the genotypes of Giardia intestinalis from domestic and wild animals in Japan, Giardia isolates obtained from feces of 24 dogs kept in households and breeding kennels, three companion cats, five dairy calves and three wild monkeys, Macaca fuscata, were genotyped using the 177 bp sequence of the glutamete dehydrogenase gene (gdh). The genotypes were assemblages A, C, D or A/D for dog isolates, Assemblage F for cat isolates, assemblages A or E for calf isolates and assemblage B for monkey isolates. This is the first report on the genotypes of Giardia isolates from cats, calves and wild monkeys in Japan.  相似文献   

5.
OBJECTIVE: To determine duration of infection and association of infection with diarrhea for dairy calves with naturally acquired cryptosporidiosis and giardiosis. DESIGN: Cohort study. ANIMALS: 20 Holstein calves on a single dairy farm. PROCEDURE: Fecal samples were collected 3 times/wk for the first 45 days after birth, then weekly until calves were 120 days old and examined for Giardia duodenalis cysts and Cryptosporidium parvum oocysts. Calves were monitored for diarrhea during the first 45 days after birth; during each episode of diarrhea, fecal samples were examined for parasitic, bacterial, and viral pathogens. RESULTS: All 20 calves shed Giardia cysts and Cryptosporidium oocysts at some time during the study. Mean ages at which Giardia cysts and Cryptosporidium oocysts were first detected were 31.5 and 16.3 days, respectively. Mean number of Giardia cysts in feces remained high throughout the study, whereas Cryptosporidium occysts decreased to low or undetectable numbers 2 weeks after infection. Eighteen calves had a total of 38 episodes of diarrhea during the first 45 days after birth. Giardia duodenalis was the only pathogen identified during 6 (16%) episodes, C parvum was the only pathogen identified during 9 (24%) episodes, and G duodenalis and C parvum were identified together during 10 (26%) episodes. CONCLUSIONS: Prevalences of giardiosis and cryptosporidiosis were high in these calves, and both parasites were associated with development of diarrhea. Cryptosporidium parvum was an important pathogen when calves were < 1 month old, but G duodenalis was more important when calves were older. Calves cleared C parvum infections within 2 weeks; however, G duodenalis infections became chronic in these calves.  相似文献   

6.
The objective of this study was to compare the occurrence and the genotypes and species of Giardia duodenalis and Cryptosporidium spp. in beef and dairy cattle from farms in the Regional Municipality of Waterloo, Ontario, in an effort to determine the potential for zoonotic transmission from these animals. Pooled manure samples were collected from 45 dairy cattle farms and 30 beef cattle farms. The presence of Giardia cysts and Cryptosporidium oocysts was determined by immunofluorescence microscopy, while nested-PCR and DNA sequencing were used to determine genotypes and species. The overall farm prevalence was very high for both Giardia and Cryptosporidium, and was similar for dairy cattle farms (96 and 64%, respectively) and beef cattle farms (97 and 63%, respectively). However, on dairy cattle farms, G. duodenalis and Cryptosporidium spp. were detected in 44% and 6% of total pooled pen manure samples, respectively, with the occurrence of both parasites being generally higher in calves than in older animals. Most Giardia isolates were identified as either the host-adapted genotype G. duodenalis Assemblage E or the zoonotic Assemblage B. Cryptosporidium parvum and Cryptosporidium andersoni were the most frequently identified species in dairy cattle, while the non-zoonotic species Cryptosporidium ryanae and Cryptosporidium bovis were also found. On beef cattle farms, 72% and 27% of the total pooled pen manure samples were positive for Giardia and Cryptosporidium, respectively, with no obvious correlation with age. All Giardia isolates in beef cattle were identified as G. duodenalis Assemblage E, while all Cryptosporidium isolates were identified by sequence analysis as C. andersoni, although microscopic analyses, and subsequent restriction fragment length polymorphism analyses, indicated that other Cryptosporidium species were also present. The results of this study indicate that although Giardia and Cryptosporidium were identified in a higher overall percentage of the pooled beef cattle manure samples than in dairy cattle, firmly established zoonotic genotypes and species were much more common in dairy cattle than in beef cattle in this region. Dairy cattle, and especially dairy calves, may, therefore, pose a greater risk of infection to humans than beef cattle. However, these results may also provide evidence of potential zooanthroponotic transmission (human to animal).  相似文献   

7.
A total of 364 fecal specimens from randomly selected pre-weaned calves, aged up to 4 months, from 5 different farms in the south of Western Australia and 1 farm from New South Wales were screened for the presence of Cryptosporidium and Giardia using PCR. There were substantial differences in prevalence between the farms and the overall prevalence was 22.3% (81/364) and 26.9% (98/364) respectively for Cryptosporidium and Giardia. For Cryptosporidium, 70 positives were identified at the 18S locus. At a unique diagnostic locus, an additional 12 C. parvum positives were identified. Sequence analysis at the 18S ribosomal RNA locus was successful for 59 of the 70 positive isolates; of these 14 were C. parvum, 28 were C. bovis, 15 were C. ryanae, 1 was pig genotype II and 1 was a mixed C. ryanae/C. parvum infection. Sub-typing analysis at the glycoprotein 60 (gp60) locus for 24 C. parvum isolates identified all as IIa; 17 were A17G2R1, 1 was A18G3R1 and 6 were A20G3R1. For Giardia, 75 positives were identified at the 18S locus and an additional 23 positives were identified at the gdh locus. The majority of the isolates sequenced were assemblage E, however assemblage A and B and mixed A and E and A, B and E infections as well as the quenda genotype were identified. The findings of the present study indicate that pre-weaned calves are not an important source of zoonotic Giardia species in Australia but may be an important source of zoonotic Cryptosporidium.  相似文献   

8.
In order to investigate the genotypes of Giardia duodenalis from domestic and farm animals in Italy, 21 Giardia isolates, 17 from dogs, 1 from cat and 3 from dairy calves, were genetically characterised by SSU-rRNA gene sequencing. Among dogs, 76.5% of isolates showed the dog-specific genotypes (Assemblages C, D and C/D mixed Assemblage) and 23.5% exhibit potential zoonotic genotypes (Assemblage A and A/C mixed Assemblages). The cat isolate belonged to assemblage A, whereas the sequences among the isolates from calves were found to correspond to hoofed-livestock genotype, namely Assemblage E. These findings suggest that infection of humans by zoonotic genotypes from domestic animals could be of low epidemiological significance, although possible. The present study represents the first contribute to the knowledge of G. duodenalis genotypes in domestic and farm animals from Italy.  相似文献   

9.
Prevalence of Giardia duodenalis genotypes in pre-weaned dairy calves   总被引：1，自引：0，他引：1  
To determine the prevalence of Giardia genotypes in pre-weaned dairy calves, fecal samples were collected from a minimum of 18, 1-7-week-old dairy calves per farm on two farms each in the states of Vermont, New York, Pennsylvania, Maryland, Virginia, North Carolina, and Florida. Samples cleaned of fecal debris and concentrated using CsCl density gradient centrifugation were stained and examined by immunofluorescence microscopy and also subjected to PCR and gene sequence analysis. Prevalence by PCR ranged from 9% on a farm in Pennsylvania to 93% on a farm in Vermont, with an average prevalence for 407 calves on 14 farms of 40%. Gene sequence analysis of the TPI, beta-giardin and 16S rRNA genes revealed 85% of the positive samples to be Assemblage E, while 15% were Assemblage A, although the percentages of these genotypes varied greatly from farm to farm. Some farms had no Assemblage A Giardia. Thus, while a majority of the calves were infected with a genotype that is not known to be infectious for humans, calves on 7 of 14 farms did harbor Assemblage A Giardia. Calves should be considered as a potential source of human infectious cysts in the environment.  相似文献   

10.
Molecular epidemiology of bovine rotavirus from the Charolais area (France). Faecal samples from 164 diarrhoeic calves under 60 days of age were collected from the Charolais area of France during winter of 1998. The samples were tested by an enzyme-linked immunosorbent assay (ELISA) to detect the presence of rotavirus antigen. Of 164 dairy calves tested, 45.1% were positive for rotavirus antigen. The presence of rotavirus was confirmed by electrophoresis of genomic segments. Genomic segment 9 coding for the surface glycoprotein VP7 was amplified by RT-PCR using amplimeres corresponding to a conserved sequence located at the 5' and 3' ends. Nucleotides of the region 29 to 320-560 (average 427) was determined by the Taq dye deoxynucleotide cycle sequencing method. By comparison to the 175 sequences of gene 9 previously published, sequence analysis demonstrated that all of the isolates from the present study belong to the genotype G6. This result confirms previously published data indicating the prevalence of rotavirus G6 in bovine, and suggests that a monovalent vaccine based on G6 antigen would be sufficient to elicit a good protection.  相似文献   

11.

Background

The primary aims of this study were to determine the incidence of Giardia infections in dairy herds on farms in the New York City Watershed region and to evaluate risk factors associated with infections. Because co-infections of Giardia and Cryptosporidium spp. are common in this population, we also evaluated the effect of herd infection status on Giardia infections.

Methods

Farms were grouped into three cohorts based on their prior infection status with Giardia and/or Cryptosporidium spp. The sampling plan included collecting fecal samples from all calves below 30 days of age and proportional sampling of calves, young stock, and adults. A total of 10,672 fecal samples were collected and analyzed for the presence of Giardia cysts using zinc sulfate flotation. Herds enrolled in the study were sampled seasonally for a study period of two years. The probability of shedding cysts past a certain age and the factors that influenced the likelihood of shedding were evaluated using survival analysis. Linear regression was used to evaluate factors that were associated with the intensity of shedding.

Results

The majority of Giardia infections occurred in calves within their first 180 days of age, with the most number of calves shedding Giardia cysts between 11 and 20 days of age. The incidence of shedding of Giardia cysts ranged from 0.0004 per animal day for cattle in the low risk cohort to 0.0011 per animal day for cattle in the high risk cohort. The likelihood of shedding was influenced by the prior infection status of the herd and the season of collection. Infected animals shed on average 9,658 cysts/gram and the intensity of shedding Giardia cysts varied significantly with the age (p < 0.0001) and the season of collection (p = 0.0151 for Spring).

Conclusion

Giardia infections are common in dairy herds in the New York City watershed, particularly in calves less than 6 months of age. Seasonality may be an important factor in the perpetuation of infections based on changes in management practices corresponding to weather patterns of a particular season. A dairy herd''s prior infection status with Cryptosporidium influences the likelihood of infection with Giardia.  相似文献   

12.
9 Giardia-free calves were artificially infected with 1.5-5.1 x 10(6) Giardia cysts originating from Swiss cattle ("bovine isolates"). In 4 of these animals the course of infection was examined. After prepatent periods of 7-8 days all calves excreted high numbers of Giardia cysts for 60-112 days. During patency on 44% of the examination days Giardia cysts and antigen could be detected simultaneously in faecal samples using the flotation method and a sandwich-ELISA, respectively. With the exception of light diarrhoea lasting only for some days at the beginning of patency no other symptoms occurred. Further 5 artificially infected calves were submitted to autopsy. Giardia trophozoites were detected in 4 calves in the jejunum and in 1 animal in the ileum (peroxidase-antiperoxidase method). All animals were simultaneously infected with Campylobacter spp. and/or Rota- and Corona-virus. Electronmicroscopically mucosal attachment sites of Giardia trophozoites had intact microvilli and enterocytes. In various parts of the intestine blunting and flattening of the villi and cellular infiltrations of the mucosa were present. These alterations in calves are generally associated with bacterial and/or viral infections of calves. A Swiss bovine Giardia cyst-isolate was transmitted to 4 Giardia-free conventionally maintained lambs which excreted Giardia cysts after prepatent periods of 10-21 days for 31-61 days.  相似文献   

13.
AIM: To investigate the prevalence of Giardia and Cryptosporidium spp in calves born during two spring-calving seasons in a rapidly intensifying dairying region in the South Island; to evaluate potential correlations between the prevalence of the organism and age, characteristics of faeces, and animal-housing practices; and to compare the results with those from established dairying regions in the North Island. METHODS: A longitudinal study was conducted in 2005 and 2006 on 10 dairy farms located in the Otago region, South Island, New Zealand. A total of 1,190 faecal samples were collected from calves 1-7 weeks old. Direct immunofluorescent microscopy was used to screen the faecal samples for Giardia cysts and Cryptosporidium oocysts. The prevalence of Giardia and Cryptosporidium spp detected in calves in Otago was compared with that previously measured in calves from dairying regions in the Waikato and Manawatu, in the North Island . RESULTS: On average, Giardia and Cryptosporidium spp were detected in 31% and 2.6% of all samples, respectively. The prevalence of Giardia spp cysts in faeces was higher in calves >or=3 weeks of age in 2005 (por=2 weeks of age in 2006 (p=0.07) than in younger calves. No age-related pattern was observed for Cryptosporidium spp in either year. No correlations were evident between characteristics of faeces or animal housing practices and the prevalence of either organism, which did not differ between the two dairy farming regions. CONCLUSIONS: Prevalence rates of Giardia and Cryptosporidium spp in calves 1-7 weeks old did not differ between the two geographical regions, nor did the regions' distinct climate conditions appear to influence the prevalence of either pathogen. Considering data from both years together, the presence of Giardia spp cysts in faeces appeared to increase in the first week or two after birth, so that, on average, 30-40% of animals from 3-6 weeks of age were affected. CLINICAL RELEVANCE: This is the first study to report the prevalence of Giardia and Cryptosporidium spp in dairy calves in the South Island of New Zealand.  相似文献   

14.
In various districts (Cantons) of Switzerland 815 calves (a few days up to 6 months old), 382 lambs and 20 young goats (both groups 1-6 months old) were selected randomly for a single coprological examination (flotation method) for Giardia infection. In average 26.6% of the calves, 29.8% of the lambs and 4 of 20 young goats excreted Giardia cysts. In 9 Cantons the percentages of cyst excretors among the calves varied between 15 and 32, but these differences were not significant. Further there were no significant differences in the frequency of cyst excretion between calves of 3 different breeds and 2 age groups (up to 3 months old and 3 to 6 months). The intensity of cyst excretion was high and varied in random samples between 4.1 x 10(3) and 3.0 x 10(5) cysts per g of faeces in calves and between 2.2 x 10(3) and 1.6 x 10(5) in lambs. In 5 of 7 farms where calves and lambs were maintained simultaneously both animal species were Giardia infected. As expected, trophozoites of Giardia isolates from calves and lambs belonged to the Giardia duodenalis type and could not be differentiated on a morphological basis. Giardia cysts from calves (average measurements: 13.7 x 9.1 microns) and lambs (13.8 x 9.2 microns) were indistinguishable both morphologically and morphometrically. The results indicate that Giardia infections are frequent and geographically widely distributed in calves and lambs in Switzerland.  相似文献   

15.
Giardia duodenalis and Cryptosporidium spp. infections, and the patterns of cyst and oocyst shedding, were observed in a herd of dairy calves in Ontario over a period of 3 mo. Cysts and oocysts were detected and enumerated in fecal samples using immunofluorescence microscopy; Giardia and Cryptosporidium DNA was detected using the polymerase chain reaction. The prevalence of G. duodenalis increased during the course of the study, reaching a peak of 93.1% when calves were 43 to 54 d old, and then decreased. Conversely, Cryptosporidium spp. prevalence was highest (75.9%) when calves were 11 to 22 d old, and subsequently decreased. The numbers of cysts and oocysts shed per gram of feces were positively correlated over time with the respective prevalence rates. Along with genotyping data, temporal changes in prevalence and shedding patterns should be considered when testing dairy calves for the presence and concentrations of cysts and oocysts, and when considering the potential for zoonotic transmission.  相似文献   

16.
In a previous study, Giardia infection patterns were studied in newborn dairy calves over a 4-month period. Chronic Giardia infections were observed in all calves with initial cyst excretion occurring at approximately 1 month of age. In the work presented here, the passive immunity and serological immune response associated with these Giardia infections were examined. Colostrum and milk samples were collected from the dams of these calves, and monthly serum samples were collected from each calf. The colostrum, milk and sera samples were analyzed by ELISA and Western blot for the presence of anti-Giardia IgG antibodies. In addition, the in vitro anti-Giardia activity of milk and colostrum was examined using a miniculture adherence assay. When examined by ELISA, mean anti-Giardia antibody titres were found to be significantly higher in colostrum compared to milk. The monthly mean serum antibody titres in the calves were not found to differ significantly at any time point during the study. Western blot analysis revealed that colostrum from the dams reacted strongly with many different Giardia antigens between 205 and 7.5kDa, while milk reacted with few antigens in the same size range. Sera collected from the calves when 30 and 60 days of age reacted with few Giardia antigens, but as the calves aged, IgG antibodies in their sera began to react with antigens of 21, 50, 65, 73 and 79kDa. The miniculture adherence assay demonstrated that colostrum had significantly more anti-Giardia activity in vitro compared to milk. These results suggest that the calves in this dairy did not mount a significant humoral immune response against Giardia following infection. However, colostrum contained a high level of anti-Giardia antibodies and exhibited anti-Giardia activity in vitro. Therefore, colostrum may have the potential to provide initial protection against Giardia infections in calves, but the lack of a strong, specific humoral immune response by these calves could account for the high prevalence and chronic duration of the infections.  相似文献   

17.
Giardia intestinalis has been reported in newborn calves world-wide; however, information on the extent of G. intestinalis in New Zealand calves has to date been very limited. The current study attempted to establish the prevalence rate of G. intestinalis in calves up to 8 weeks old in New Zealand. More than 700 calf fecal specimens were collected during the spring calving seasons of 1998 and 1999 from two regions in North Island, New Zealand (Manawatu and Waikato) and tested for the presence of G. intestinalis. In addition to determining the presence of G. intestinalis in newborn calves, sequence analysis was performed using specific amplification primers developed to target a section of the ribosomal DNA (rDNA). This locus is considered to be rapidly evolving, and therefore, suitable for use in the elucidation of phylogenetic relationships between G. intestinalis isolates. Sequencing was performed using G. intestinalis DNA extracted from cysts collected directly from the calf fecal matter. There was no culturing of the G. intestinalis isolates either in vivo or in vitro. Over 40% of all collected calf fecal specimens contained G. intestinalis cysts and rDNA sequence analysis revealed two different sequences among calf isolates. These sequence differences were not found to correspond to a particular season, geographical region or farming practice. Preliminary phylogenetic analysis suggests that these two rDNA sequence types are indicative of calf hosts.  相似文献   

18.
Prevalence of Giardia duodenalis in dairy and beef cattle on farms around Charlottetown, Prince Edward Island (Canada) was determined by analyzing feces using direct immunofluorescence antibody microscopy. Genotypes were determined by 16S-rRNA sequencing. Fecal samples (n = 892) were collected from adult cattle in dairy tie-stall, dairy free-stall, and beef herds (10 herds each), and from calves (n = 183) from 11 dairy farms. Prevalence rates were 38% and 51% in cows and calves, respectively. Giardia duodenalis was present in all dairy herds, in 9/10 beef herds and in calves from 10/11 herds examined. Prevalence rates were 40% and 41% for cows in tie- and free-stall herds, respectively, and 27% for beef cows. Zoonotic Assemblage A was found in 12.2% of calves concomitantly infected with Assemblage E. All successfully sequenced samples (114/128) from cows corresponded to Assemblage E. Giardia duodenalis is highly prevalent in cattle herds in Prince Edward Island and Assemblage A in calves is a potential public health concern.  相似文献   

19.
Giardia lamblia which parasitize humans belong to either of two genotypes, A or B, based on specific signature sequences in the 5' end of the small subunit (16S) ribosomal RNA (rRNA) gene. These two genotypes also were found in cysts from fecal samples of animal origin such as dogs, cats, some farm animals and wild animals. In addition, trophozoites recovered from cysts obtained from environmental samples belonged to these two genotypes as well, suggesting that the G. lamblia genotypes A and B are widespread and possibly zoonotic. Trophozoites were recovered from rats and these isolates might belong to another genotype of G. lamblia. Deer mice and one dog appeared to be parasitized by genotypes of Giardia with close affinity to G. microti. This species, therefore, also consists of a genotype complex.  相似文献   

20.
OBJECTIVE: To determine the total number of Cryptosporidium parvum oocysts and Giardia spp cysts shed by dairy calves during the period when they are most at risk after natural infection. ANIMALS: 478 calves naturally infected with C. parvum and 1,016 calves naturally infected with Giardia spp. PROCEDURE: Oocysts or cysts were enumerated from fecal specimens. Distribution of number of oocysts or cysts versus age was used to determine the best fitting mathematic function. Number of oocysts or cysts per gram of feces for a given duration of shedding was computed by determining the area under the curve. Total number of oocysts or cysts was calculated by taking the product of the resultant and the expected mass of feces. Results: Intensity of Cparvum oocyst shedding was best described by a second-order polynomial function. Shedding increased from 4 days of age, peaked at day 12, and then decreased. An infected 6-day-old calf would produce 3.89 x 10(10) oocysts until 12 days old. Pattern of shedding of Giardia spp cysts was best described by exponential functions. Intensity of shedding increased from 4 days of age, peaked at day 14, and then decreased. An infected calf would produce 3.8 x 10(7) cysts from day 50 until day 56. CONCLUSIONS AND CLINICAL RELEVANCE: The large number of oocysts and cysts shed indicates that shedding by dairy cattle poses a risk for susceptible calves and people. Estimates reported here may be useful to aid in designing cost-effective strategies to manage this risk.  相似文献   

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