Influence of age and plasma treatment on neutrophil phagocytosis and CD18 expression in foals

The aim of this study was to evaluate the influence of age and plasma treatment on neutrophil phagocytosis, CD18 expression and serum opsonic capacity in foals in field settings. Microbial infections constitute a large threat in young foals and neutrophil functions are crucial for the defense. Blood samples were obtained from 13 foals at seven time points between the ages of 2 and 56 days and once from 16 adult horses. Six of the foals were treated with adult plasma at the age of 1 week. Neutrophil phagocytosis of yeast after various opsonizations and the expression of complement adhesion receptor CD18 were analysed by flow cytometry. Autologous serum opsonization resulted in 52+/-6.1% phagocytic neutrophils in 2-day-old foals (n = 12), a significantly lower rate than in adult horses (mean 84+/-3.1%; n = 16). In foals, yeast ingestion per neutrophil was also lower than in adults. Opsonic capacity increased with age (p < 0.05), reaching adult levels at 3-4 weeks. An increase in serum opsonic capacity followed plasma treatment (p < 0.05). The phagocytic capacity of foal neutrophils at the time-points studied was equal to or higher than that in the adults, when pooled adult horse serum or anti-yeast IgG was used as opsonin. In foals, serum IgG concentration was negatively correlated to serum opsonic capacity. CD18 receptor expression was higher in neutrophils from foals (<21 days old) than in those from adult horses (p < 0.05). The results indicate that foals are transiently deficient in serum opsonic capacity, which negatively affects their capacity for neutrophil phagocytosis. These changes in serum opsonins, unrelated to IgG, may be important factors in susceptibility to infections in foals.     

Serum lactoferrin and immunoglobulin G concentrations in healthy or ill neonatal foals and healthy adult horses

BACKGROUND: Lactoferrin is a colostral glycoprotein with antimicrobial properties. HYPOTHESES: (1) Serum lactoferrin and immunoglobulin G (IgG) concentrations are correlated and increase in healthy foals after ingestion of colostrum; (2) compared to healthy foals, ill foals will have lower lactoferrin concentrations that correlate with their IgG concentration, neutrophil count, the diagnosis of sepsis, and survival; and (3) plasma concentrations of lactoferrin will be less than serum concentrations. ANIMALS: Healthy foals (n = 16), mature horses (n = 10), and ill foals 1-4 days old (n = 111) that were examined for suspected sepsis were used for blood collection. Colostrum was obtained from 10 healthy mares unrelated to the foals. METHODS: Blood was obtained from the healthy foals at birth and 1-3 days of age and from the ill foals at admission. Serum IgG was quantified by single radial immunodiffusion (SRID). Lactoferrin concentrations in colostrum and blood were determined by an enzyme-linked immunosorbant assay. The sepsis score, blood culture results, neutrophil counts, and survival were obtained on ill foals. RESULTS: The mean colostral lactoferrin concentration was 21.7 microg/mL. Compared to values at birth, serum IgG (18+/-2 versus 2,921+/-245 mg/dL, SEM) and lactoferrin (249+/-39 versus 445+/-63 ng/mL, SEM) concentrations were significantly greater in healthy foals 1-3 days old. Serum lactoferrin concentration in 1-3-day-old healthy foals was not different from mature horses or ill foals. IgG and lactoferrin concentrations were significantly correlated only in healthy foals. Serum lactoferrin concentrations were significantly lower in ill neutropenic foals. The serum IgG concentration was significantly lower in ill foals as compared to healthy foals. Only serum IgG was significantly less in ill foals with a positive sepsis score and in nonsurvivors, Plasma lactoferrin concentrations were lower than serum concentrations, although values were significantly correlated. CLINICAL IMPORTANCE: Although both serum IgG and lactoferrin concentrations increase in healthy foals after ingestion of colostrum, only serum IgG is significantly correlated with the sepsis score and outcome.     

A comparison of foal and adult horse neutrophil function using flow cytometric techniques

Flow cytometric assays were used to compare phagocytic and oxidative burst activity of neutrophils from healthy foals less than 7 days of age with the activity of cells from healthy adult horses. The phagocytosis of Staphylococcus aureus by foal neutrophils was less than that observed for adult neutrophils when autologous serum was used as the source of opsonins in the assay. The use of adult serum did not significantly improve the ability of foal neutrophils to attach bacteria. The oxidative burst activity of foal neutrophils was equivalent to that of adult cells. However, when serum or plasma was incorporated into the oxidative burst assay, foal neutrophils demonstrated greatly reduced autofluorescence and a suppressed response to phorbol myristate acetate (PMA), relative to that demonstrated by adult cells. These results suggest that peripheral blood neutrophils from foals have a reduced ability to phagocytose bacteria relative to that exhibited by adult horse neutrophils and that the oxidative burst activity of foal neutrophils is down-regulated in response to an unidentified serum factor(s). Such changes may contribute to the increased susceptibility of foals to septic disease.     

Effect of plasma transfusion on neutrophil function in healthy and septic foals

OBJECTIVE: To evaluate the effect of plasma transfusion on phagocytosis and oxidative burst activity of peripheral blood neutrophils from healthy and septic equine neonates with sub-optimal passive transfer of maternal immunity. ANIMALS: Nine healthy and seven septic foals with suboptimal passive transfer of maternal immunity (serum IgG < 8 g/L) presented to participating veterinary hospitals for plasma transfusion, and seven healthy foals less than 7 days of age and with circulating IgG concentrations > or = 8 g/L. PROCEDURE: Foals with serum IgG concentrations < 8 g/L were assessed as healthy or septic. Sepsis was recognised by positive bacterial cultures and/or sepsis scores of > or = 11. All foals received between 1 and 3 L of plasma to boost circulating IgG concentrations to > or = 8 g/L. Serum IgG concentrations were determined before and following transfusion by glutaraldehyde coagulation test and confirmed by single radial immunodiffusion assays. Neutrophil phagocytosis and oxidative burst activity were determined before plasma transfusion and at 0 h, 12 h, 24 h, 48 h and 5 d following treatment. Neutrophil function from seven healthy foals less than 7 d of age and with circulating IgG concentrations of > or = 8 g/L was similarly evaluated on a single occasion. RESULTS: Plasma treatment significantly increased circulating IgG concentrations for healthy and septic foals. Oxidative burst activity of neutrophils from septic foals was significantly increased 5 days following treatment, relative to 0 h post treatment. Other differences were not significant but suggested a transient decrease in phagocytosis by neutrophils from healthy foals and increased phagocytosis by neutrophils from septic foals immediately following transfusion. Oxidative burst activity of neutrophils from septic foals tended to be less than that of healthy foals at all sampling times. Serum IgG concentrations were not correlated with neutrophil phagocytosis, but were correlated with oxidative burst activity. CONCLUSIONS: Plasma transfusion did not improve neutrophil function of healthy foals, suggesting that such treatment may be of equivocal benefit for healthy neonates. Conversely, improved neutrophil function was observed following treatment of septic foals, suggesting that plasma transfusion was beneficial for these foals. Oxidative burst activity of neutrophils from septic foals was lower than that of neutrophils from healthy foals and was significantly improved 5 days post treatment, when compared with values obtained immediately following treatment.     

Immunoglobulin isotypes in sera and nasal mucosal secretions and their neonatal transfer and distribution in horses

OBJECTIVE: To determine concentrations of IgA and IgG subclasses in serum, colostrum, milk, and nasal wash samples of adult horses and foals. ANIMALS: Seven 2-year-old Welsh ponies, 27 adult mixed-breed horses, and 5 Quarter Horse mares and their foals. PROCEDURE: Serum was obtained from ponies and adult horses. Colostrum and milk were obtained from mares and serum and nasal wash samples from their foals immediately after parturition and on days 1, 7, 14, 28, 42, and 63. Nasal wash samples were also obtained from 23 adult horses. Concentrations of immunoglobulins were determined by use of inhibition ELISA. To determine transfer of maternal isotypes to foals, concentrations in colostrum and milk were compared with those in foal serum. Serum half-lives of isotypes in foals were also determined. RESULTS: IgGb was the most abundant isotype in serum and colostrum from adult horses, whereas IgA was the predominant isotype in milk. The major isotype in nasal secretions of adult horses and foals > or = 28 days old was IgA, but IgGa and IgGb were the major isotypes in nasal secretions of foals < or = 14 days old. Serum half lives of IgGa, IgGb, IgG(T), and IgA in foals were 176, 32, 21, and 3.4 days, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The early immunoglobulin repertoire of neonatal foals comprised IgGa, IgG(T), and IgA; endogenous synthesis of IgGb could not be detected until 63 days after birth. The restricted repertoire of immunoglobulins in foals may influence humoral immune responses to vaccination.     

Serum opsonization capacity, phagocytosis, and oxidative burst activity in neonatal foals in the intensive care unit

BACKGROUND: Phagocytic activity of neonatal foals has been reported to be similar to that of adult horses, but serum opsonization capacity develops with age and may be further altered when opsonins are consumed during infection. HYPOTHESIS: Phagocytosis, oxidative burst activity, and serum opsonization capacity in neonatal foals admitted to an intensive care unit are reduced in comparison with control foals. ANIMALS: Blood samples were collected from hospitalized neonatal foals and from control foals. Hospitalized foals were characterized as sick or septic on the basis of a sepsis score and received intravenous plasma transfusion. METHODS: Phagocytosis, oxidative burst activity, and serum opsonization capacity were tested with flow cytometric analysis. Serum immunoglobulin and complement component 3 concentrations were determined with radial immunodiffusion. Serum amyloid A concentration was assayed with a commercially available solid-phase Sandwich ELISA Kit. Data were analyzed with nonparametric and regression methods. Alpha was set at P = .05. RESULTS: Phagocytic functions of septic and sick foals were lower than control foals in the initial phase of the study (P = .01). Opsonization capacity was significantly higher when bacteria were opsonized with serum from septic (P = .029) and sick (P = .006) foals than from control foals on day 1. Opsonization capacity in septic foals was comparable with control foals on days 2 and 5. This effect was not accompanied by an increase in serum complement C3 or immunoglobulin G concentrations independently. CONCLUSIONS AND CLINICAL IMPORTANCE: Our results suggest that phagocytic function could be decreased in hospitalized foals. The synergistic effect of opsonic elements provided by plasma transfusion may sustain opsonization capacity during sepsis.     

Peripheral Blood Lymphocyte Subpopulations and Immunoglobulin Concentrations in Healthy Foals and Foals with Rhodococcus equi Pneumonia

Infectious diseases are common in foals aged 1-5 months. The objectives of this investigation were to evaluate immunologic parameters in foals from birth to weaning to establish reference values for the proportion of circulating lymphocytes that were helper (CD4+) or cytotoxic (CD8+) T cells, or B cells; to measure serum immunoglobulin (IgM and IgG) concentrations; and to compare these immunologic parameters to values in foals with naturally occurring Rhodococcus equi pneumonia and in adult horses. Peripheral blood lymphocyte subpopulations were determined by flow cytometric analysis, and serum IgG and IgM concentrations were determined by radial immunodiffusion. Flow cytometric analysis of lymphocyte subpopulations suggested age-related changes in the cell-mediated immune system in horses. Absolute circulating CD4+ and CD8+ T lymphocytes and B cells increased linearly up to 3 months of age. Circulating B cell concentrations from birth to 6 months of age were greater than values in adult horses and the lymphocyte differences among the age groups are mainly due to variation in B lymphocytes. Both absolute and proportional B cell concentrations were greater in foals with R equi pneumonia than in healthy foals at the same age. The increase in absolute cell counts of each subpopulation was dependent on the increase of absolute peripheral blood lymphocyte count. Serum IgG concentration increased linearly from 1 to 3 months of age, and serum IgM concentrations increased from 1 to 6 months of age. These data suggest age-dependent cell-mediated and humoral development in young foals.     

Opsonic capacity of foal serum for the two neonatal pathogens Escherichia coli and Actinobacillus equuli.

Two of the most commonly isolated foal pathogens are Escherichia coli and Actinobacillus equuli. The hypothesis tested in this study was that young foals carry a lower opsonic capacity for these bacteria compared to adult horses. A flow-cytometric method for the phagocytosis of these by equine neutrophils was established. The opsonic capacity of serum from healthy foals from birth to age 6 weeks was evaluated and related to the concentrations of IgGa and IgGb. Phagocytosis of yeast was used as a control. Serum was required for phagocytosis, with higher concentrations for E. coli than for A. equuli. Ingestion of colostrum led to a significantly higher serum opsonic capacity. After that, there was no consistent age-related trend for opsonic capacity for the different microbes. Foal serum showed similar or higher opsonisation of E. coli and A. equuli compared to serum from mature individuals. During the studied period, the predominance among IgG subisotypes switched from IgGb to IgGa. Although the overall correlation between concentrations of IgG subisotypes and serum opsonic capacity was poor, sera with IgGb levels below 1.9 mg/ml induced lower opsonisation of E. coli and yeast, but not of A. equuli. Complement activation was important for opsonisation of all tested microbes. The results of this study are significant to the understanding of a key immunological facet in the pathophysiology of equine neonatal septicaemia in clinical practice.     

Post-Transfusion Survival of 50Cr-Labeled Erythrocytes in Neonatal Foals

Erythrocytes transfused allogeneically into mature horses have a short survival (less than 4 days) compared with an expected erythrocyte life span of 140-150 days. Yet, foals undergo transfusions for neonatal isoerythrolysis successfully. The authors have determined the survival of transfused erythrocytes in neonatal foals, using the stable isotope, 50Cr, to label the erythrocytes. Normal foals underwent transfusions with labeled erythrocytes from three sources: their own erythrocytes (autologous), the erythrocytes of their dam, and the erythrocytes of an unrelated castrated male. After transfusion, samples were taken at 15 minutes and then daily for a week and every 2 or 3 days for 20 days. A stable isotope of iron (57Fe) and 50Cr were determined on diluted-packed erythrocytes by inductively coupled argon-coupled mass spectrometry techniques. 57Fe was used as measure of the sample hemoglobin concentration. The ratio of 50Cr to 57Fe decreased exponentially in all foals. Half-time (T1/2) was 11.7 days (standard error = 2.2) for four foals that underwent autologous transfusions, 5.5 +/- 1.0 days for five foals that underwent transfusions with the erythrocytes of their dams, and 5.2 +/- 1.1 days for five foals that had transfusions with erythrocytes from an unrelated gelding. The authors conclude that erythrocytes that are transfused allogenically into neonatal foals will survive longer than those transfused into mature horses and that 50Cr labeling can be used to measure survival of transfused erythrocytes.     

Influence of age on neutrophil function in foals.

Functional activities (phagocytosis and killing) of neutrophil leucocytes (NL) and immunoglobulin G concentrations were evaluated in six healthy foals from birth to 6 months of age. Peripheral blood NL were reacted with Streptococcus equisimilis in 20 per cent pooled equine serum for 30, 60 and 90 mins and functional activities of NL were determined using a fluorochrome microassay. Values for foal NL function were compared with those of healthy adult horses (n = 28). Foal neutrophil function was influenced by age. Killing capacity of NL decreased, whereas phagocytic capacity increased, until 113 days of age, after which a reversal in trends became apparent. Immunoglobulin G concentrations changed significantly over time and were lowest at 29 to 56 days of age. All foal values for NL function fell within the range of normal values established for healthy adult horses.     

Immunologic Profiles of Peripheral Blood Leukocytes and Serum Immunoglobulin G Concentrations in Perinatal Mares and Neonatal Foals (Heavy Draft Horse)

The purpose of this study was to examine sequential changes in the immunologic parameters of perinatal mares and neonatal foals of the heavy draft horse. Blood samples were collected from clinically healthy pregnant mares and their newborn foals every week from 1 month before the expected foaling date, and 1 hour, 1 day (24-48 hours), and 1, 2, 3, and 4 weeks after foaling. Peripheral blood samples were used to examine total leukocyte counts (n = 20), differential leukocyte counts (n = 20), lymphocyte subpopulations (n = 13), lymphocyte responses to mitogens (n = 10), neutrophil phagocytic function (n = 12), and serum immunoglobulin G (IgG) concentrations (n = 10). In perinatal mares, remarkable changes observed included increased neutrophils, decreased lymphocytes, decreased CD4⁺ T lymphocytes, and decreased lymphocyte responses to mitogens at delivery. These changes were speculated to be the result of physical stress associated with delivery. In neonatal foals, increase in the phagocytic function of neutrophils, and increase in serum IgG concentration after suckling colostrum and increase of lymphocytes accompanied by physiologic growth were observed. Compared to dams, foals showed lower phagocytic function of neutrophils before suckling and fewer lymphocytes and lower lymphocyte responses to mitogens within 1 day after birth. This study revealed immunologic dynamics in perinatal mares and neonatal foals. Immunologic functions are suppressed in foaling mares and are immature in neonatal foals, especially before colostral intake. We expect these data will be useful for further studies in the field of clinical immunology, and preventive medicine.     

Evaluation of intravenous administration of concentrated immunoglobulin G to colostrum-deprived foals.

Ten foals of various breeds were deprived of colostrum from birth to 36 hours of age, then were allotted to 2 groups. Foals of group 1 (n = 6) were given 20 g (200 ml) of purified equine IgG IV in a 10% solution, and foals of group 2 (n = 4) were given 30 g (300 ml) of the same preparation. Total administration time for each 10 g of IgG in 100 ml was approximately 10 minutes. Serum IgG concentration in foals was assessed prior to, between 24 and 48 hours, and at 7 and 14 days after IgG administration. Between 24 and 48 hours after IgG administration, mean serum IgG concentration in group-1 foals was 425 mg/dl (range, 350 to 480 mg/dl). Mean body weight for this group of foals was 50.3 kg (range, 43.3 to 54.7 kg). For group-2 foals, mean serum IgG concentration was 768 mg/dl (range, 640 to 920 mg/dl) between 24 and 48 hours after administration of IgG. Foals of this group had mean body weight of 43.2 kg (range, 36.5 to 47.5 kg). Serum IgG concentration in group-2 foals at 24 to 48 hours was significantly (P = 0.005) greater than that in group-1 foals. Mean total IgG recovery at 24 to 48 hours, calculated on the basis of 94.5 ml of plasma volume/kg of body weight, was approximately 100%. Values of IgG measured in all foals 1 and 2 weeks after administration of the IgG concentrate were equivalent to values expected after normal decay of passively acquired IgG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum ferritin, serum iron, and erythrocyte values in foals

Twenty-one healthy Thoroughbred and Quarter Horse foals were studied from birth until 1 year of age. Foals had access to an iron-supplemented creep feed before weaning and were fed an iron-supplemented concentrate as part of their diet after weaning at 4 months of age. Initial blood samples were taken before foals were allowed to nurse. Serum iron concentration, total iron-binding capacity, and PCV decreased during the foal's first 24 hours of life. Serum iron concentration decreased rapidly from 446 +/- 16 micrograms/dl (mean +/- SE) at birth to 105 +/- 11 micrograms/dl at 3 days of age. Serum ferritin concentration increased from a mean of 85 +/- 8 ng/ml at birth to 159 +/- 11 ng/ml at 1 day of age. Thereafter, ferritin concentration decreased gradually to a minimum of 61 +/- 6 ng/ml at 3 weeks of age, and then at 6 months increased to values similar to those from reference adult horses. The ferritin concentration in colostrum at birth was 354 +/- 42 ng/ml, compared with 25 +/- 2 ng/ml in milk 1 day later. The decrease and then increase in serum ferritin concentration occurred concomitantly with opposite changes in serum total iron-binding capacity. The mean PCV decreased gradually to a minimum at 3 months of age. This decrease was associated with an increasing number of microcytes, as determined with a cell-size distribution analyzer.     

Absorption of bovine colostral immunoglobulins G and M in newborn foals

The uptake of colostral IgG and IgM, their serum half-lives, and the rates of endogenous synthesis of IgG and IgM were evaluated in 6 newborn foals fed bovine colostrum (principals) and 6 foals allowed to suckle their dams (controls). The principal foals were fed 400 ml of bovine colostrum (IgG, 10,000 mg/dl and IgM, 200 mg/dl) at 2-hour intervals, from 2 to 20 hours after foaling (total dose, 4 L). Serum IgG and IgM concentrations were determined by single radial immunodiffusion from birth to 98 days of age. At foaling, principal foals had no detectable serum equine IgG, but 1 control foal had serum equine IgG of 185 mg/dl. After ingestion of colostrum, there was no significant difference in the maximal serum bovine IgG concentration (range, 1,350 to 3,300 mg/dl) in the principal foals, and maximal serum equine IgG concentration in the control foals (range, 500 to 6,000 mg/dl). The calculated biological bovine and equine IgG half-life in the principal and control groups was 9.4 and 26 days, respectively. Endogenous IgG synthesis was first detected in 1 principal foal at 3 days of age, but was detected first between 28 and 42 days in the other principal foals. Starting on day 56 there was no significant difference in serum equine IgG concentration between groups. At foaling, foals in both groups had low equine IgM concentrations. In the control foals, there was marked individual variation in the increases in equine IgM concentration (range, 5 to 73 mg/dl) after ingestion of colostrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum bile acids concentrations in healthy and clinically ill neonatal foals

BACKGROUND: Reference ranges for serum bile acids (SBA) concentration are well established in healthy adult horses. Increased values are indicative of hepatic disease. HYPOTHESES: SBA concentrations are significantly greater in the neonatal period compared with mature horses, and illness in the neonatal period will further increase SBA. ANIMALS: Ten healthy mature horses, 12 healthy foals, and 31 clinically ill foals. METHODS: Prospective cross-sectional study. Blood samples were obtained once from the mature horses, from healthy foals immediately after birth, at 2 days, and at 1, 2, 3, 4, and 6 weeks of age; and from ill foals less than 1 month of age at the time of admission to the Veterinary Teaching Hospital. SBA concentrations were determined enzymatically and by radioimmunoassay. Total and direct bilirubin and triglyceride concentrations were measured, as well as sorbitol dehydrogenase (SDH) and gamma-glutamyltransferase (GGT) activities. RESULTS: There was a significant negative correlation between age and SBA concentration. Compared with mature horses, SBA concentrations were significantly greater in healthy foals at each collection time over the first 6 weeks of life. Radioimmunoassay values were lower than enzymatic SBA values, with increasing bias as the mean difference between values increased. When comparing age-matched values between healthy and ill foals, there were no significant differences in SBA. None of the ill foals had a primary diagnosis of hepatic disease. There was no significant correlation between the SBA concentration and the bilirubin or triglyceride concentrations or the GGT activity. There was a significant direct correlation between increased SBA and serum SDH activity in healthy foals only. CONCLUSION AND CLINICAL IMPORTANCE: SBA concentrations in foals are significantly higher in the early neonatal period, underscoring the importance of using age-matched references when evaluating clinical pathology values during the neonatal period.     

Passive transfer failure in horses: incidence and causative factors on a breeding farm

A prospective study was performed to determine the incidence and associated maternal and managemental factors of failure of passive transfer (FPT) in foals on a breeding farm. The zinc sulfate turbidity test (ZSTT) and latex agglutination test (LAT) were compared for accuracy in estimating serum immunoglobulin (Ig)G of foals, as determined by single radial immunodiffusion (SRID). Complete past and present foaling histories of 136 Standardbred mares were obtained. All foalings were witnessed by farm attendants, and colostral samples were collected from mares within 2 hours after parturition. Foals that did not rise and nurse were supplemented with colostrum from the dam, using a bottle or nasogastric tube. Serum samples were prepared from foals and mares between 24 and 36 hours after parturition, and from some mares 45 to 90 days before parturition. Serum IgG concentrations of mares and foals and colostral whey were determined, using SRID. Serum IgG also was estimated in foals, using ZSTT and a commercially available LAT. Four of the 136 foals (2.9%) had FPT (serum IgG less than or equal to 400 mg/dl). Serum IgG concentrations in foals significantly correlated with colostral IgG (P less than 0.001). A significantly larger proportion of foals with FPT were bottle-fed their colostrum (P less than 0.01). Month of parturition, mare age, parity, number of barren seasons, incidence of assisted births or retained placenta, or prepartum serum IgG concentrations did not significantly affect colostral IgG concentrations or serum IgG concentrations in foals. As serum IgG concentrations in foals decreased and as colostral IgG concentrations decreased, the proportion of mares that prelactated significantly (P less than 0.01) increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Equine haptoglobin: isolation, characterization, and the effects of ageing, delivery and inflammation on its serum concentration.

Haptoglobin (Hp) was isolated from equine serum by ammonium sulphate precipitation, anion-exchange chromatography and gel filtration. Equine Hp which migrated to the alpha 2-globulin region in electrophoresis, contained 2 fractions with molecular weights (NW) of 108,000 and 105,000, and each fraction consisting of 2 subunits. Quantitative measurement of Hp in equine serum was performed by the single radial immunodiffusion method using anti-equine Hp serum. In clinically normal horses, the highest concentration of serum Hp was found in newborn foals and a high value was maintained until 12 months of age. The concentration then decreased with age. Normal Hp values were 5.25 +/- 2.36 mg/ml in foals (less than or equal to 12 months old), 2.19 +/- 1.54 mg/ml in adult horses (greater than or equal to 18 months old) and 3.62 +/- 0.81 mg/ml in all horses. Serum Hp concentration in mares during the perinatal period in comparison with the normal adult female was high for 4 months pre-partum, a passing increase at delivery, and then decreased at 2 weeks post-partum returning to normal within 1 month of delivery. In horses with experimentally-induced inflammation, serum Hp concentration began to increase immediately after treatment and reached the highest value, 1.5 to 9 times higher than those of pre-treatment at 2 to 5 days, then decreased within 4 weeks. It was also elevated in most cases of horses with clinically inflammatory signs.     

Clostridium difficile: prevalence in horses and environment,and antimicrobial susceptibility

REASONS FOR PERFORMING STUDY: Clostridium difficile has been associated with acute colitis in mature horses. OBJECTIVES: To survey C. difficile colonisation of the alimentary tract with age, occurrence of diarrhoea and history of antibiotic therapy; and to study the occurrence and survival of C. difficile in the environment and antimicrobial susceptibility of isolated strains. METHODS: A total of 777 horses of different breeds, age and sex were studied. Further, 598 soil samples and 434 indoor surface samples were examined. Antimicrobial susceptibility of 52 strains was investigated by Etest for 10 antibiotics. RESULTS: In horses that developed acute colitis during antibiotic treatment, 18 of 43 (42%) were positive to C. difficile culture and 12 of these (28%) were positive in the cytotoxin B test. Furthermore, C. difficile was isolated from a small number of diarrhoeic mature horses (4 of 72 [6%]) with no history of antibiotic treatment, but not from 273 healthy mature horses examined or 65 horses with colic. An interesting new finding was that, in normal healthy foals age < 14 days, C. difficile was isolated from 1/3 of foals (16 of 56 [29%]). All older foals (170) except one were negative. Seven of 16 (44%) nondiarrhoeic foals treated with erythromycin or gentamicin in combination with rifampicin were also excretors of C. difficile. On studfarms, 14 of 132 (11%) outdoor soil samples were positive for C. difficile in culture, whereas only 2 of 220 (1%) soil samples from farms with mature horses were positive for C. difficile (P = < 0.001). By PCR, it was demonstrated that strains from the environment and healthy foals can serve as a potential reservoir of toxigenic C. difficile. The experimental study conducted here found that C. difficile survived in nature and indoors for at least 4 years in inoculated equine faeces. The susceptibility of 52 strains was investigated for 10 antibiotics and all were susceptible to metronidazole (MIC < or = 4 mg/l) and vancomycin (MIC < or = 2 mg/l). CONCLUSIONS: C. difficile is associated with acute colitis in mature horses, following antibiotic treatment. Furthermore, C. difficile was isolated from 1 in 3 normal healthy foals age < 14 days. POTENTIAL RELEVANCE: Strains from healthy foals and the environment can serve as a potential reservoir of toxigenic C. difficile.     

A study of bovine and equine immunoglobulin levels in pony foals fed bovine colostrum

As part of a project to raise specific pathogen free (SPF) Welsh Mountain Pony foals, free from exposure to Equid herpesvirus type 1, foals were removed from their dams at birth and fed bovine colostrum. This study characterises the uptake of bovine colostral immunoglobulin and production of endogenous immunoglobulin, in 10 SPF foals. An enzyme-linked immunoadsorbent assay was developed to measure serum concentrations of bovine IgG1 (boIgG1) to assess the efficiency of transfer, and rate of elimination of boIgG1 by the foal. The endogenous production of equine IgG was studied using a single radial immunodiffusion test. Foals were given 1.2 to 2 litres of bovine colostrum achieving peak serum boIgG1 concentrations of 18.9 to 34.2 g/litre (mean 28.0). The mean half-life of boIgG1 in the foals was 7.4 days. Endogenous immunoglobulin production resulted in equine IgG concentrations greater than 2 g/litre in six of 10 foals by 14 to 19 days of age, and greater than 7 g/litre in eight of 10 foals by 37 to 50 days of age. All foals had equine IgG serum concentrations greater than 10 g/litre by 102 to 135 days of age.     

A follow up study on antibodies against Lawsonia intracellularis in mares and foals from two breeding farms in Germany

Equine proliferative enteropathy (EPE) caused by Lawsonia (L.) intracellularis is an emerging disease in foals, particularly in North America. Since a case report in Germany exists, the objective of this study was to examine the incidence of L. intracellularis-antibodies in healthy horses from two German breeding farms. In group 1, serum samples from 24 (year 1) and 16 (year 2) Haflinger mares and their foals were taken. In group 2, over a period of five months, serum samples of six warmblood mares and foals were collected monthly from birth until the foals became seronegative. Serum samples were tested using an ELISA system. Results are expressed as Percentage of Inhibiton (PI). All adult mares (100%) of both groups were seropositive at each point in time (PI-value > 30). In group 1,7/24 foals (29.2%) in year 1 and 4/16 foals (25%) in year 2 had antibodies.The seropositive foals from year 2 had the same dams as the seropositive foals from year 1. In group 2 five of six foals were seropositive after birth. Antibodies decreased from March to July in mares and foals. In July, all five foals tested negative for the first time between the ages of 82 and 141 days (median 115 days). PI-values of mares were significantly correlated with PI-values of their foals. Higher PI-values were seen in younger foals and early in spring. Loss of antibodies in foals at the age of three to five months could be a risk factor for infection and appearance of EPE.