Improved quantitative estimates of low environmental loading and sporadic periparturient shedding of Cryptosporidium parvum in adult beef cattle.

Our primary goal was to generate an accurate estimate of the daily environmental loading rate of Cryptosporidium parvum oocysts for adult beef cattle, using immunomagnetic separation coupled with direct immunofluorescence microscopy for a highly sensitive diagnostic assay. An additional goal was to measure the prevalence and intensity of fecal shedding of C. parvum oocysts in pre- and postparturient cows as an indicator of their potential to infect young calves. This diagnostic method could detect with a > or = 90% probability oocyst concentrations as low as 3.2 oocysts g of feces(-1), with a 54% probability of detecting just one oocyst g of feces(-1). Using this diagnostic method, the overall apparent prevalence of adult beef cattle testing positive for C. parvum was 7.1% (17 of 240), with 8.3 and 5.8% of cattle shedding oocysts during the pre- and postcalving periods, respectively. The mean intensity of oocyst shedding for test-positive cattle was 3.38 oocysts g of feces(-1). The estimated environmental loading rate of C. parvum ranged from 3,900 to 9,200 oocysts cow(-1) day(-1), which is substantially less than a previous estimate of 1.7 x 10(5) oocysts cow(-1) day(-1) (range of 7.7 x 10(4) to 2.3 x 10(5) oocysts cow(-1) day(-1)) (B. Hoar, E. R. Atwill, and T. B. Farver, Quant. Microbiol. 2:21-36, 2000). Use of this highly sensitive assay functioned to detect a greater proportion of low-intensity shedders in our population of cattle, which reduced the estimated mean intensity of shedding and thereby reduced the associated environmental loading rate compared to those of previous studies.

Fecal shedding of Giardia duodenalis, Cryptosporidium parvum, Salmonella organisms, and Escherichia coli O157:H7 from llamas in California.

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. CONCLUSIONS 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.

Effect of blood sampling and shipment to slaughter on plasma catecholamine concentrations in bulls.

The effect of venipuncture on blood serum catecholamine concentrations was studied in five yearling Red Angus bulls. Treatments consisted of sampling jugular vein blood via indwelling cannulas in a squeeze chute every 10 min for 1 h; sampling jugular vein blood from an indwelling catheter before, during and after venipuncture simulation; sampling jugular vein blood by venipuncture in a chute after shipment of 320 km to a slaughter plant; and sampling pooled blood from the neck during exsanguination at slaughter. Plasma epinephrine (E) and norepinephrine (NE) concentrations were determined by high performance liquid chromatography (HPLC) with electrochemical detection (ECD). Prevenipuncture NE and E in blood sampled from an indwelling catheter extended through a solid wall were 1.0 and .5 pmol/ml plasma, respectively. Plasma NE and E during venipuncture (1.6 and 1.1 pmol/ml, respectively) and immediately after cannulation in a squeeze chute (1.8 and 1.2 pmol/ml, respectively) were higher than prevenipuncture concentrations. Plasma NE and E, 1.9 and 1.2 pmol/ml plasma after shipment of 320 km, increased during exsanguination to 135.8 and 81.3 pmol/ml plasma, respectively. The NE and E in blood samples collected by venipuncture in a chute or box stall do not represent resting concentrations of these catecholamines.