Prediction of Packed Cell Volume after Whole Blood Transfusion in Small Ruminants and South American Camelids: 80 Cases (2006-2016).

BACKGROUND: Calculation of desired whole blood transfusion volume relies on an estimate of an animal's circulating blood volume, generally accepted to be 0.08 L/kg or 8% of the animal's body weight in kilograms. OBJECTIVE: To use packed cell volume before and after whole blood transfusion to evaluate the accuracy of a commonly used equation to predict packed cell volume after transfusion in small ruminants and South American camelids; to determine the nature and frequency of adverse transfusion reactions in small ruminants and camelids after whole blood transfusion. ANIMALS: Fifty-eight small ruminants and 22 alpacas that received whole blood transfusions for anemia. METHODS: Retrospective case series; medical record review for small ruminants and camelids that received whole blood transfusions during hospitalization. RESULTS: Mean volume of distribution of blood as a fraction of body weight in sheep (0.075 L/kg, 7.5% BW) and goats (0.076 L/kg, 7.6% BW) differed significantly (P < 0.01) from alpacas (0.103 L/kg, 10.3% BW). Mild transfusion reactions were noted in 16% of transfusions. CONCLUSIONS AND CLINICAL RELEVANCE: The generally accepted value of 8% for circulating blood volume (volume of distribution of blood) is adequate for calculation of transfusion volumes; however, use of the species-specific circulating blood volume can improve calculation of transfusion volume to predict and achieve desired packed cell volume. The incidence of transfusion reactions in small ruminants and camelids is low.

Longitudinal relationship between fecal culture, fecal quantitative PCR, and milk ELISA in Mycobacterium avium ssp. paratuberculosis-infected cows from low-prevalence dairy herds.

Mycobacterium avium ssp. paratuberculosis (MAP), the causative agent of ruminant Johne's disease, presents a particular challenge with regard to infection mitigation on dairy farms. Diagnostic testing strategies to identify and quantify MAP and associated antibodies are imperfect, and certain facets of the relationship between diagnostic tests remain to be explored. Additional repeated-measures data from known infected animals are needed to complement the body of cross-sectional research on Johne's disease-testing methods. Statistical models that accurately account for multiple diagnostic results while adjusting for the effects of individual animals and herds over time can provide a more detailed understanding of the interplay between diagnostic outcomes. Further, test results may be considered as continuous wherever possible so as to avoid the information loss associated with dichotomization. To achieve a broader understanding of the relationship between diagnostic tests, we collected a large number of repeated fecal and milk samples from 14 infected cows, in addition to bulk milk samples, from 2 low-prevalence dairy herds in the northeast United States. Predominately through the use of mixed linear modeling, we identified strong associations between milk ELISA optical density, fecal quantitative PCR, and fecal culture in individual animals while concurrently adjusting for variables that could alter these relationships. Notably, we uncovered subtleties in the predictive abilities of fecal shedding level on milk ELISA results, with animals categorized as disease progressors reaching higher ELISA optical density levels. Moreover, we observed that spikes in fecal shedding could predict subsequent high ELISA values up to 2 mo later. We also investigated the presence of MAP in individual milk samples via PCR and noted an association between poor udder hygiene and MAP positivity in milk, suggesting some level of environmental contamination. The paucity of positive milk samples and the complete absence of detectable MAP in the bulk tank throughout the study period indicate that contamination of milk with MAP may not be of chief concern in low-prevalence herds. An enhanced understanding of the interrelationships between diagnostic tests can only benefit the development of testing strategies and objectives, which in turn may lessen MAP infection prevalence in dairy herds.

Plasma Peak and Trough Gentamicin Concentrations in Hospitalized Horses Receiving Intravenously Administered Gentamicin.

BACKGROUND: Gentamicin is an aminoglycoside antimicrobial commonly used in horses at 6.6 mg/kg IV once daily. Therapeutic drug monitoring (TDM) can confirm desired peak concentration is reached for common bacterial isolates, and detect toxicosis associated with high trough values. OBJECTIVES: Determine the relationship between gentamicin dose and plasma concentration in hospitalized horses, and identify a starting dose range to achieve peaks > 32 µg/mL. ANIMALS: Sixty-five horses (2002-2010) receiving once-daily gentamicin with TDM performed (N = 99 sets). METHODS: Retrospective study. Data from hospitalized horses including weight, dose, plasma peak, and trough gentamicin concentration, creatinine concentrations and presence of focal or systemic disease were collected from medical records. Peak concentrations measured 25-35 minutes after administration were included (N = 77). Data were divided into low (<7.7 mg/kg), medium (7.7-9.7 mg/kg) and high (>9.7 mg/kg) dose groups, and were grouped by the horse having focal or systemic disease. RESULTS: Peak concentrations resulting from doses ≥7.7 mg/kg were 5.74 µg/mL (SE 2.1 µg/mL) greater than peaks from doses <7.7 mg/kg (P = .007). Peak concentrations was 3.6 times more likely to be >32 µg/mL if dose was ≥7.7 mg/kg (P = .04). There were no significant effects of dose on trough or creatinine concentration. At a given dose, horses with focal disease had higher peaks than those with systemic disease (P = .039). CONCLUSIONS AND CLINICAL IMPORTANCE: These data suggest gentamicin dosage should be individually determined in horses using TDM, but support an initial once-daily dose of 7.7-9.7 mg/kg IV to achieve peaks >32 µg/mL and trough concentrations <2 µg/mL. Further studies evaluating the safety of doses >6.6 mg/kg are required.

Gastrointestinal ultrasonography of normal Standardbred neonates and frequency of asymptomatic intussusceptions.

BACKGROUND: Ultrasonographic appearance of the gastrointestinal (GI) tract of equine neonates has not been completely described. OBJECTIVES: To describe (1) sonographic characteristics of the GI segments in normal nonsedated equine neonates, (2) intra- and interobserver variation in wall thickness, and (3) the sonographic appearance of asymptomatic intussusceptions, and (4) to compare age and sonographic findings of foals with and without asymptomatic intussusceptions. ANIMALS: Eighteen healthy Standardbred foals ≤5 days of age. METHODS: Prospective, cross-sectional blinded study. Gastrointestinal sonograms were performed stall-side. Intraobserver variability in wall thickness measurements was determined by calculating the coefficient of variation (CV). The Bland-Altman method was used to assess interobserver bias. Student's t-test and Fisher's exact test were used to test the association among presence of intussusceptions, age, and selected sonographic findings. RESULTS: The reference ranges (95% predictive interval) for wall thickness were 1.6-3.6 mm for the stomach, 1.9-3.2 mm for the duodenum, 1.9-3.1 mm for the jejunum, 1.3-2.2 mm for the colon, and 0.8-2.7 mm for the cecum. Intraobserver wall thickness CV ranged from 8 to 21% for the 2 observers for 5 gastrointestinal segments. The interobserver bias for wall thickness measurements was not significant except for the stomach (0.14 mm, P < .05) and duodenum (0.29 mm, P < .05). Diagnostic images of mural blood flow could not be obtained. Asymptomatic intussusceptions were found in 10/18 neonates. Associations between sonographic variables or age and the presence of intussusceptions were not found. CONCLUSIONS AND CLINICAL IMPORTANCE: Sonographic characteristics of the GI tract of normal Standardbred neonates can be useful in evaluating ill foals. Asymptomatic small intestinal intussusceptions occur in normal Standardbred neonates.

Prevalence of Mycobacterium avium subsp. paratuberculosis fecal shedding in alpacas presented to veterinary hospitals in the United States.

BACKGROUND: The prevalence of Johne's disease in alpacas in the United States is unknown. The limits of polymerase chain reaction (PCR) detection of Mycobacterium avium subsp. paratuberculosis (MAP) in alpaca feces have not been determined. OBJECTIVES: To evaluate the use of PCR for MAP detection in alpaca feces; and to estimate the prevalence of MAP fecal shedding in alpacas presented to veterinary teaching hospitals. ANIMALS: Alpacas presenting to 4 US veterinary teaching hospitals from November 2009 to February 2011. METHODS: Prospective study. Ten dilutions of a wild MAP strain were added to negative alpaca feces and processed for MAP detection by means of a commercial real-time PCR (RT-PCR) assay, and cultured on Herrold's Egg Yolk Medium (HEYM) and liquid broth. The limits of detection for each method were determined. Fecal samples from alpacas admitted to the veterinary teaching hospitals during the study period were evaluated for MAP via PCR and HEYM. RESULTS: The lowest MAP dilution detectable via PCR was 243 MAP colony-forming units (CFU)/g of feces, at which concentration MAP growth was detectable on HEYM. Ten (6%; 95% confidence interval: 3-9%) of the 180 fecal samples collected were positive on PCR. CONCLUSIONS AND CLINICAL IMPORTANCE: Polymerase chain reaction can provide an accurate and rapid detection of MAP fecal shedding in alpacas; and the prevalence of MAP fecal shedding in hospitalized alpacas in 4 US veterinary teaching hospitals was 6%.

Indirect fluorescent antibody test and surface antigen ELISAs for antemortem diagnosis of equine protozoal myeloencephalitis.

BACKGROUND: Recent research suggests that serum : CSF titer ratios could provide the most accurate antemortem diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. OBJECTIVES: The purpose of this study was to assess the utility of two commercially available tests, the indirect fluorescent antibody test (IFAT) and the surface antigen 2, 4/3 ELISA (SAG2, 4/3 ELISA), using archived paired serum and CSF samples. ANIMALS: Samples were obtained from 4 types of clinical patients. Confirmed positive cases (n = 9 horses; 11 sample sets) had neurologic deficits and postmortem lesions consistent with EPM. Confirmed negative cases (n = 28) had variable clinical signs and postmortem lesions consistent with another disease. Suspected positive cases (n = 6) had neurologic deficits consistent with EPM, marked improvement after treatment, and exclusion of other diseases. Suspected negative cases (n = 14) had variable signs with a strong presumptive diagnosis of another disease. METHODS: For each test, descriptive statistics were calculated using serum results alone, CSF results alone, and a serum : CSF titer ratio. RESULTS: Overall accuracy was highest for SAG2, 4/3 ELISA titer ratio at 0.97 (95% CI 0.88-0.99) with sensitivity = 0.88 (95% CI 0.66-0.97) and specificity = 1 (95% CI 0.92-1). IFAT CSF and titer ratio results also showed high accuracy at 0.88 (95% CI 0.77-0.94), but lower sensitivity = 0.65 (95% CI 0.41-0.83). CONCLUSIONS AND CLINICAL IMPORTANCE: Using serum results alone was least accurate for both test types. The more accurate methods, such as the SAG2, 4/3 ELISA serum : CSF titer ratio, should be utilized.

Paratuberculosis (Johne's disease) in cattle and other susceptible species.

Paratuberculosis (Johne's disease) is a widespread and costly disease. This consensus statement will summarize recommendations regarding diagnosis, control, and treatment of Johne's disease in cattle and other species. Each section of recommendations is followed by a statement that subjectively characterizes the strength of the supporting evidence. The role played by Mycobacterium avium subsp. paratuberculosis (MAP) in the pathogenesis has been a matter of controversy for many years. This statement concludes with an assessment of the evidence in favor of MAP as a potential zoonotic pathogen.

Antimicrobial activity of gallium nitrate against Mycobacterium avium subsp. paratuberculosis in neonatal calves.

BACKGROUND: Mycobacterium avium subsp. paratuberculosis (MAP), the agent of Johne's disease in cattle, is a facultative intracellular bacterium that is dependent on ferric iron for its survival and replication. Gallium (Ga), a trivalent semimetal that shares many similarities with ferric iron and functions as an iron mimic has been shown to have in vitro antimicrobial activity against several microorganisms, including MAP. OBJECTIVES: (1) To investigate the antimicrobial activity of Ga in calves experimentally infected with MAP; and (2) to monitor for potential adverse effects of Ga on calf health. ANIMALS: Twelve Holstein calves. METHODS: Randomized blind controlled experiment. Beginning at 10 days of age (study day 1), the experimental calves (n = 6) were treated with 20 mg/kg gallium nitrate daily for 45 days. On study days 4 and 5, all calves were challenged with a PO dose of a live field strain MAP. Treated calves were monitored daily for adverse effects. Calves were euthanized on study day 100, and 29 tissue samples and 1 fecal sample were collected from each calf. Samples were cultured for MAP by MGIT liquid culture system, Herrold's Egg Yolk Medium culture, or both. RESULTS: No adverse effects were observed in the treated calves. Treatment was associated with a significant reduction in MAP tissue burden when compared with control calves (P = .017). CONCLUSIONS AND CLINICAL RELEVANCE: Chemoprophylactic treatment of calves with Ga before and during the period of high susceptibility decreased MAP tissue colonization in experimentally infected neonatal calves.

Utility of 2 immunological tests for antemortem diagnosis of equine protozoal myeloencephalitis (Sarcocystis neurona Infection) in naturally occurring cases.

BACKGROUND: Antemortem diagnosis of equine protozoal myeloencephalitis (EPM) is challenging. Limited information is available regarding a commercial test (surface antigen 1 [SAG-1] ELISA). Performance of another commercial test (indirect fluorescent antibody test [IFAT]) using samples from an independent group has not been well described. HYPOTHESIS/OBJECTIVES: The primary goal was to evaluate the SAG-1 ELISA and IFAT using naturally occurring EPM cases. A secondary goal was to obtain more information regarding clinical presentation. ANIMALS: Hospital cases were admitted over 20 months and classified into 4 groups. Confirmed positive cases (n = 9) had asymmetric or multifocal neurologic deficits or both and postmortem lesions consistent with EPM. Confirmed negative cases (n = 17) had variable clinical signs and postmortem lesions consistent with another neurologic disease (or no lesions). Suspected positive cases (n = 10) had asymmetric or multifocal deficits or both, marked improvement after treatment for EPM, and other likely diseases excluded. Suspected negative cases (n = 29) had orthopedic disease and no neurologic deficits. METHODS: Results of immunological testing (SAG-1 ELISA and IFAT on serum or cerebrospinal fluid [CSF] or both), neurologic examinations, CSF analyses, and postmortem examinations were analyzed retrospectively. RESULTS: SAG-1 ELISA sensitivity was 12.5% (95% CI, 1.6-38.4) and specificity was 97.1% (95% CI, 84.7-99.9) using serum. IFAT sensitivity was 94.4% (95% CI, 72.7-99.9) and specificity was 85.2% (95% CI, 66.3-95.8) using serum; sensitivity was 92.3% (95% CI, 64.0-99.8) and specificity was 89.7% (95% CI, 72.7-97.8) using CSF. CONCLUSIONS AND CLINICAL IMPORTANCE: Low sensitivity of the SAG-1 ELISA limited its usefulness for antemortem diagnosis of EPM in this patient population.

Coagulation abnormalities and complications after percutaneous liver biopsy in horses.

BACKGROUND: Liver biopsy is useful in the diagnosis of liver disease in horses. However, bleeding is the major complication. Liver dysfunction can result in abnormalities in coagulation, although there is no definitive association between risk of hemorrhage after biopsy and coagulopathy in humans. Frequency of coagulopathies in horses with liver disease and the nature and frequency of complications after liver biopsy are not reported. HYPOTHESIS/OBJECTIVES: To determine whether there is an association between coagulopathy and hemorrhage after liver biopsy in horses. ANIMALS: Horses with suspected liver disease from which a liver biopsy had been obtained. METHODS: Retrospective study. Variables indicative of coagulation were recorded. The frequency and nature of complications after biopsy were assessed using clinical and hematologic data. The association between abnormal coagulation variables and complications was assessed. RESULTS: Seventy biopsies were obtained from 66 horses. At least 1 coagulation profile abnormality was identified in 58% of the 43 horses with histopathologically confirmed liver disease. Complications were observed in 4/32 monitored horses (33 biopsies). Three horses had a decrease in the packed cell volume suggestive of subclinical bleeding, and 1 horse developed a diaphragmatic hematoma. There was no association between coagulation profile abnormality and complications. CONCLUSION AND CLINICAL IMPORTANCE: Abnormalities of coagulation are common in horses with liver disease. Liver biopsy appears to be a safe procedure in the horse. An abnormal coagulation profile is not clearly associated with an increased risk of complications after biopsy.

Tissue predilection sites and effect of dose on Mycobacterium avium subs. paratuberculosis organism recovery in a short-term bovine experimental oral infection model.

The objective of this study was to develop a short-term experimental infection model for Mycobacterium avium subsp. paratuberculosis (MAP) in cattle, using small oral doses of organisms. Specifically, the effect of dose size was evaluated, as well as specific tissue predilection sites for recovery of MAP. Oral doses as low as 1.5 x 10(6) CFU reliably produced infection that could be detected 3 weeks following infection. Detection of infection required culture of multiple intestinal samples (jejunum and ileum) for MAP. Histological examination did not permit detection at this early stage. Results from this study suggest intestinal mucosa, rather than tonsil, as the primary portal of entry for MAP. The experimental infection model described here is useful for studying the early effects of preventive and therapeutic interventions for paratuberculosis in cattle.

Hypokalaemia as a cause of recumbency in an adult dairy cow.

A 3-year-old Holstein cow was presented for evaluation of recumbency. Physical examination and laboratory evaluations resulted in a diagnosis of hypokalaemia causing extreme skeletal muscle weakness. Treatment involved intravenous and oral potassium supplementation, antimicrobial and anti-inflammatory therapy, and management of recumbency using a flotation tank (the Aquacow Rise System). The cow recovered and returned to the milking herd. Multifactorial elements were identified as the cause of hypokalaemia including inappetance, treatments for ketosis and administration of dexamethasone.

Disposition of flunixin meglumine injectable preparation administered orally to healthy horses.

An injectable preparation of flunixin meglumine was administered orally and intravenously at a dose of 1.1 mg/kg to six healthy adult horses in a cross-over design. Flunixin meglumine was detected in plasma within 15 min of administration and peak plasma concentrations were observed 45-60 min after oral administration. Mean bioavailability of the oral drug was 71.9 +/- 26.0%, with an absorption half-life of 0.76 h. The apparent elimination half-life after oral administration was 2.4 h. The injectable preparation of flunixin meglumine is suitable for oral administration to horses.

Evaluation of a commercial ELISA for diagnosis of paratuberculosis in cattle.

OBJECTIVE: To evaluate sensitivity and specificity of a new ELISA for antibodies against Mycobacterium avium subsp paratuberculosis. DESIGN: Cross-sectional observational survey. SAMPLE POPULATION: Serum samples from 590 cattle that were infected with M avium subsp paratuberculosis and 723 cattle that were not infected. PROCEDURE: Serum samples were tested by use of an ELISA for antibodies against M avium subsp paratuberculosis. RESULTS: Sensitivity of the test varied from 15.4 to 88.1%, depending on the clinical stage and bacterial shedding status of the cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Results obtained with use of the new ELISA agreed favorably with those of a previous ELISA. Practitioners must be aware of variability in the sensitivity of the test, which depends on the clinical and shedding status of the cattle, because this may affect interpretation of test results.

ELISA and fecal culture for paratuberculosis (Johne's disease): sensitivity and specificity of each method.

The sensitivity and specificity of the ELISA and fecal culture tests for paratuberculosis in dairy cattle are examined. ELISA and fecal culture data from seven dairy herds where both fecal cultures and ELISA testing was done concurrently are included. A cohort of 954 cattle including 697 parturient adults, cultured every 6 months from 10 herds followed over 4 years served as the basis to determine fecal culture sensitivity. The fecal culture technique utilized a 2g sample with centrifugation and double incubation. Of the 954 cattle cohort of all ages (calf to adult) that were fecal sampled on the first herd visit, 79 were culture positive. An additional 131 animals were detected as culture positive over the next seven tests at 6-month intervals. The sensitivity of fecal culture to detect infected cattle on the first sampling was 38%. Of the 697 parturient cattle cohort, 67 were positive on the first fecal culture, while an additional 91 adult cattle were culture positive over the next seven tests, resulting in a sensitivity of 42% on the first culture of the total animals identified as culture positive. Animals culled from the herds prior to being detected as infected and animals always fecal culture negative with culture positive tissues at slaughter are not included in the calculations. Both groups of infected cattle will lower the apparent sensitivity of fecal culture. Infected dairy herds tested concurrently with both fecal culture and ELISA usually resulted in more than twofold positive animals by culture compared to ELISA. The classification of infected cattle by the extent of shedding of Mycobacterium paratuberculosis in the feces helps define the relative proportion of cattle in each group and therefore the likelihood of detection by the ELISA test. ELISA has a higher sensitivity in animals with a heavier bacterial load, i.e. high shedders (75%) compared to low shedders (15%). Repeated testing of infected herds identifies a higher proportion of low shedders which are more likely to be ELISA negative. Thus, the sensitivity of the ELISA test decreases with repeated herd testing over time, since heavy shedders will be culled first from the herds.

Tolerance of a rice-based oral rehydration solution given to normal calves.

The objective of the study was to test the tolerance of a rice-based oral rehydration formula when fed to calves. Six healthy Holstein calves, 1 week of age, were fed the formula instead of milk replacer for 3 days. Pre- and posttreatment results of clinical examination and laboratory parameters were compared. Vital signs, attitude, appetite, clinical hydration status, urine specific gravity, and most routine serum biochemistry test results did not vary and remained within the normal range. Five of the 6 calves developed diarrhea when fed the rice-based formula, which was accompanied by a reduction in fecal pH and presence of reducing sugars in the feces. This effect was reversed when calves were returned to the milk replacer diet at the end of the study. Diarrhea was accompanied by increased water consumption, which allowed the calves to maintain normal hydration status. These results suggest that calves are unable to properly digest the rice-derived carbohydrate, and this type of formula is not recommended for oral rehydration of calves.