Biomedical subjects

I G Colditz

Publications and source records attributed to I G Colditz.

At least 19 recordsLinked to original sources

PubMed2006

Adjusting worm egg counts for faecal moisture in sheep.

The number of eggs from gastrointestinal nematodes per gram of faeces (worm egg count WEC) is commonly used to determine the need for anti-parasite treatments and the breeding value of animals when selecting for worm resistance. Diarrhoea increases faecal moisture and may dilute the number of worm eggs observed. To quantify this effect, egg counts in sheep at pasture were simulated by dosing 15 animals with chromic oxide particles. The simulated WEC diminished as faecal moisture increased. When faeces were dried, simulated WEC per unit dry matter was not influenced by the amount of faecal moisture present prior to drying. The results suggest that adjustment for faecal moisture may provide an improved estimate of FEC. Drying faeces to calculate the WEC per unit dry matter would provide such an adjustment but may not be practical for industry application. In the past, the CSIRO McMaster Laboratory has used an adjustment factor developed by Gordon based on the classification of faecal consistency derived from the morphology of faeces. To examine the utility of an adjustment factor based on faecal consistency score (FCS), the relationships between FCS and simulated WEC and dry matter were examined. Dry matter and simulated WEC exhibited an exponential decline as FCS increased. The relationship between FCS and dry matter was further examined in 368 samples collected over 12 months from sheep at pasture, where it was observed that dry matter showed a linear decline as FCS increased. Adjustment factors based on dry matter were similar to those proposed by Gordon however adjustment factors predicted from simulated WEC diverged from the remainder for FCS>4. As no samples scored FCS 5 in the study of simulated FEC, the adjustment factors based on the larger study that included samples with FCS 5 was therefore considered more robust. Adjustment factors were given by the equation: WEC(estimated)=(WEC(observed)/(34.21-5.15 FCS))x29.06. This equation estimates for samples with FCS>1 the WEC that would be expected if the samples were FCS 1, the faecal consistency score for normal faeces. The impact of adjustment of observed WEC for faecal moisture predicted by FCS on decision points for treatment and on estimated breeding values requires further examination.

Animals↗

PubMed2003

Serum amyloid A in the serum and milk of ewes with mastitis induced experimentally with Staphylococcus epidermidis.

Mastitis was induced experimentally in ewes with Staphylococcus epidermidis, and the concentrations of serum amyloid A (SAA) in milk and serum, and the somatic cell counts and bacteria in the milk were determined for up to 10 weeks in two experiments, each examining five infected and five control ewes. The somatic cell counts peaked eight hours after infection and preceded an increase in SAA in milk. A maximum concentration of 6460 microg/ml SAA was recorded in milk from the infected sheep, compared with a mean concentration of 1.4 microg/ml in the control sheep. The mean peak concentration of SAA in serum (206.8 microg/ml) occurred earlier (one day after infection) than in milk. The serum concentration of SAA in the healthy animals ranged from 0 to 29.4 microg/ml. There was no correlation between the concentrations of SAA in serum and milk.

Animals↗

PubMed2003

Cytokines in mammary lymph and milk during endotoxin-induced bovine mastitis.

Cytokine kinetics were examined in milk and in afferent and efferent lymph of the supramammary lymph node after intramammary infusion of endotoxin from Escherichia coli. Cows were sampled 0, 2 and 4h after infusion (p.i.). Neutrophils appeared in afferent lymph 2h p.i., and in efferent lymph and milk 4h p.i. The milk contained high concentrations of interleukin-8 (IL-8) at 2 and 4h p.i. IL-8 was also found in lymph, but at lower concentrations. The tumor necrosis factor-alpha (TNF-alpha) concentration tended to increase in afferent lymph at 2h p.i., and increased in milk at 4h p.i. The level of IL-1beta increased at 4h p.i. in milk, but was not detected in lymph. Interferon-gamma was not detected in any sample, at any time. The results indicate a primary role for IL-8 in the recruitment of neutrophils into the gland, and suggest that IL-1beta and TNF-alpha are not necessary for IL-8 production and release in response to endotoxin.

Animals↗

PubMed2002

Immunological responses of the lactating ovine udder following experimental challenge with Staphylococcus epidermidis.

The responses of five lactating ewes to experimental mammary infection with Staphylococcus epidermidis were examined. Infection caused an intense but transient influx of neutrophils into milk, which peaked at 8 h and was accompanied by mild fever and mild leukopaenia in blood. No other signs of systemic infection were observed. Number of staphylococci in milk decreased logarithmically until 24 h, were absent from three ewes at 48 h and then increased in number or re-emerged in four of the five ewes at 72 or 144 h. At all times milk appeared grossly normal. Expression of the adhesion molecules CD11b and CD18 increased on neutrophils in milk at 24 h then tended to decline over subsequent days. The proportion of lymphocytes positive for CD4, CD8, WC1 and MHCII tended to decrease from 24 to 72 h then increased at 144 h. Cytokines in milk were measured by ELISA. IL-8 was elevated in infected glands at 2 h, peaked at 24 h and remained elevated until the final sampling at 144 h. IL-6 was transiently elevated at 4 and 8 h while IL-1beta remained elevated from 8 until 144 h. The results suggest that the intense early neutrophil infiltrate eliminated most but not all bacteria and a state of subclinical infection ensued. After 24 h , leukocyte numbers in milk declined while cytokines, especially IL-8 remained elevated, suggesting that sensitivity or responsiveness of gland to inflammatory signals decreased as infection progressed. This attenuation of the host defence response may have contributed to the failure of the gland to eliminate bacteria and may be an important feature of the development of chronic and subclinical mastitis.

Animals↗

PubMed2002

Use of lectin binding characteristics to identify gastrointestinal parasite eggs in faeces.

Identification of the presence and abundance of species is important when choosing therapies and control strategies for internal parasitism of livestock. Here we examine lectin binding characteristics of eggs isolated from sheep faeces as a means for identifying the parasite genera contributing to infection. The intensity of lectin staining varied with incubation time, incubation volume, concentration of lectin and concentration of eggs. Formalin fixed eggs had greater autofluorescence but exhibited the same lectin staining pattern as fresh eggs. The stage of egg development did not influence staining. Eggs from Haemonchus contortus, H. placei, Trichostrongylus colubriformis, T. vitrinus, Ostertagia circumcincta, Nematodirus spathiger and the cestode Monezia expansa were incubated with a panel of fluoroscein isothiocyanate (FITC)-labelled lectins. Lectin binding exhibited a genus specific pattern. Haemonchus spp. stained strongly positive with peanut agglutinin (PNA), and were positive for concanavalin A (ConA), Ricinus communis agglutinin (RCA) and Maclura pomifera lectin (MPA). Trichostrongylus spp. were PNA-, ConA-, RCA- and strongly MPA+. O. circumcincta were weakly positive for PNA, MPA, ConA and negative for RCA. N. spathiger were weakly positive for the four lectins, and M. expansa were weakly positive for PNA, RCA and MPA and were strongly ConA+. The genus specificity of lectin staining was used to identify the presence of Trichostrongylus and Haemonchus eggs in faeces from sheep with mixed field infections, however correspondence between lectin staining and larval differentiation for identifying a low prevalence of Ostertagia in the field infection was poor. Refinements in methods for rapid egg isolation may improve egg differentiation on the basis of lectin staining, which could be undertaken by flow cytometry or microscopy.

Animals↗

PubMed2002

Production of antibodies to recombinant antigens from Lucilia cuprina following cutaneous immunisation of sheep.

Immunological control of cutaneous myiasis of sheep caused by Lucilia cuprina larvae has been an elusive goal. Antibody to antigens derived from the peritrophic membrane can stunt or kill larvae in a dose dependent fashion. Thus efficacy of vaccines employing these antigens may be limited by the amount of antibody in skin available for ingestion by larvae. The potential for elevating antibody concentrations in skin by intradermal immunisation with the recombinant peritrophic membrane antigens peritrophin-44, peritrophin-48 and peritrophin-95 was therefore examined. Using within-animal comparisons, specific antibody was significantly higher in skin transudates from locally immunised sites than from adjacent adjuvant control sites. It was concluded that cutaneous immunisation may assist immunological control of blowfly larvae.

Animals↗

PubMed2002

Effect of transcutaneous immunization with co-administered antigen and cholera toxin on systemic and mucosal antibody responses in sheep.

Direct application of antigens to skin together with an adjuvant, a procedure called transcutaneous immunization (TCI), can induce systemic immune responses in mice, humans, cats and dogs. In previous studies we found that cholera toxin (CT) applied topically on unbroken skin induces systemic antibody and lymphocyte proliferative responses in sheep. The current study examined whether concurrent administration of CT and tetanus toxoid (TT) delivered transcutaneously could induce specific antibody responses to both antigens in sheep. Antibodies to both TT and CT were induced by TCI although antibody titres in serum to TT were higher in sheep receiving TT plus alum by intramuscular injection (n=5) than TT plus CT by TCI (n=5). The ratio of IgG1/IgG2 antibody to TT in serum was near unity, and the route of immunization, TCI versus injection, did not influence this ratio. In contrast, the ratio of IgG1/IgG2 antibody differed significantly between the two antigens, TT and CT, delivered by TCI, with a higher proportion of IgG1 antibody in serum to CT than TT. Antibody to TT was detected in lung washes from TCI and injection groups, with IgG1 predominating over IgG2 in both groups. IgA antibodies to CT and TT were detected in sera of CT and TT-immunized groups respectively but in lung washes IgA antibody to TT was detected only in the injection group. Results show that TCI induced systemic antibody responses to CT and the co-administered antigen TT, whereas no evidence was obtained for mucosal IgA responses following TCI.

Administration, Cutaneous↗

PubMed2002

Immunosuppressive effects of Marek's disease virus (MDV) and herpesvirus of turkeys (HVT) in broiler chickens and the protective effect of HVT vaccination against MDV challenge.

Much of the impact of Marek's disease in broiler chickens is considered to be due to immunosuppression induced by Marek's disease virus (MDV). The present study evaluates the effects of an Australian isolate of pathogenic MDV (strain MPF 57) and a non-pathogenic vaccinal strain of herpesvirus of turkeys (HVT) (strain FC 126) on the immune system of commercial broiler chickens for 35 days following challenge at days 0 or 3 of age. It also investigates the extent of protection provided by HVT vaccine against MDV-induced immunosuppression. Immune system variables, including relative lymphoid organ weight, blood lymphocyte phenotype (CD45+/CD3+, putatively T, and CD45+/LC+, putatively B) and antibody production following vaccination against infectious bronchitis (IB) at hatch, were used to assess the immune status of chickens. Immunosuppression was also assessed by susceptibility to secondary challenge with pathogenic Escherichia coli on day 29 post-MDV challenge. MDV infection reduced the weight of the thymus and bursa of Fabricius, the numbers of circulating T lymphocytes and B lymphocytes, and IB antibody titre. The timing of these effects varied. MDV infection greatly increased susceptibility to E. coli infection. HVT alone caused mild depletion of T and B lymphocytes but no effect on immune organ weight or IB titre. Vaccination with HVT provided good protection against most of the immunosuppressive effects of MDV but not against MDV-induced growth impairment and reduced responsiveness to IB vaccination, suggesting that recent Australian strains of MDV may be evolving in virulence to overcome the protective effects of HVT.

Animals↗

PubMed2001

Simulated solar UVB exposure inhibits transcutaneous immunization to cholera toxin via an irradiated skin site in cattle.

Transcutaneous immunization (TCI) is a new needle-free vaccination technology with the potential to reduce the risk of needle-borne disease transmission and carcass damage within the livestock industries. The principal antigen-presenting cell involved in TCI is thought to be the epidermal Langerhans cell. Langerhans cell function is inhibited by cutaneous ultraviolet-B radiation (UVB) exposure. Such exposure may inhibit TCI through sun exposed skin sites due to the phenomenon of local low dose photoimmunosuppression. TCI of cattle to cholera toxin (CT) resulted in the generation of a serum anti-CT-specific IgG(2) response. However, exposure of cattle to a sub-inflammatory dose of simulated solar UVB (2.43 x 10(3)J/m(2)) significantly (P<0.05) inhibited TCI to CT via irradiated skin sites.

Administration, Cutaneous↗

PubMed2001

Effects of dietary protein types on immune responses and levels of infection with Eimeria vermiformis in mice.

The present study reports the dietary effects of bovine alpha whey fraction, bovine casein and soy protein isolate on the immune responsiveness of C57BL/6J mice infected with Eimeria vermiformis. During the patent period, mice fed alpha whey fraction had significantly higher blood total white cell, CD4+ and CD8+ lymphocyte counts and higher Con A-stimulated IFN-gamma production by spleen cells than those fed other protein sources, but there was no significant difference in output of faecal oocysts. Casein-fed mice had significantly higher levels of Con A- stimulated IFN-gamma production and a lower output of faecal oocysts than soy-fed mice. The study demonstrated that dietary proteins have different impacts on immune responsiveness and level of parasitic infection in the gut; however, the mechanisms affecting level of infection are not clear. These effects appeared not to be solely related to nutritional properties of the diets. Further research into the underlying immune mechanisms and possible direct interactions between bioactive proteins and the parasite E. vermiformis should be fruitful.

Animals↗

PubMed2001

Expression of cell surface adhesion molecules by peripheral blood eosinophils during Trichostrongylus colubriformis infection in sheep.

The effect of infection of sheep with the gastrointestinal nematode parasite Trichostrongylus colubriformis on expression of adhesion molecules CD11a, CD11b, CD11c, CD18, CD44, CD49d and CD62L by peripheral blood eosinophils was examined by flow cytometry. Initially, to establish the sensitivity of adhesion molecules to inflammatory signals, eosinophil-rich exudates were elicited in non-lactating mammary glands of immune sheep by infusion of 50 microg of soluble antigen extract from T. colubriformis third stage larvae. Eosinophils comprised 40.8% of mammary leucocytes and 4.5% of peripheral blood leucocytes. In comparison with blood, the percentage of eosinophils expressing CD18 increased and the percentage expressing CD62L decreased in exudates and the mean fluorescent intensity, an indicator of receptor number per cell, for CD11a and CD49d also decreased on exudate eosinophils. Peripheral blood eosinophils were examined over 8 weeks during trickle infection of immune sheep with infective or irradiated third stage larvae of T. colubriformis. During the last 3 weeks of infection, CD11a staining decreased in infected sheep and CD44 staining decreased in sheep receiving either infective or irradiated larvae. Other surface markers did not change. The results indicate that systemic changes in expression of adhesion molecules by eosinophils occur during T. colubriformis infection in sheep.

Animals↗

PubMed2000

Induction of systemic immune responses in sheep by topical application of cholera toxin to skin.

Cholera (and related) toxins (CT) when applied topically on unbroken skin induce systemic immune responses in mice, a procedure called transcutaneous immunization (TCI). The current study examined the capacity for TCI to induce systemic immune responses in sheep. Three groups (n=5 per group) were immunized at day 0 (priming) and day 28 (boosting) with 250 microg of CT in water by TCI, with 25 microg of CT in alum by intramuscular injection, or not immunized. Serum samples were taken at days 0, 28, 42, 56 and 70 after immunization for measurement of CT-specific IgG as well as CT-specific IgG1, IgG2, IgA and IgM antibodies by ELISA. After immunization, IgG, IgG1 and IgG2 antibody in immunized groups were significantly higher than in the control group, and boosting further increased these titres. IgG, IgG1 and IgG2 in the injection group were significantly higher than in the TCI group. There was a preponderance of IgG1 antibody, relative to IgG2, in both immunized groups. CT-specific IgA and IgM were detected in both immunized groups. Lymphocyte proliferation to CT was measured at day 90. A CT-specific lymphocyte proliferative response (stimulation index>2) was detected in all sheep from the injection group, in two sheep from the TCI group and in none of the controls. Results demonstrated that TCI induces primary and secondary antibody responses and specific proliferative responses to CT in sheep.

Administration, Cutaneous↗

PubMed2000

Effect on systemic antibody concentrations of topical application of choleratoxin to skin of sheep.

OBJECTIVE: To examine the ability of a vaccine formulation combining choleratoxin with an experimental antigen to induce a systemic antibody response when applied topically on unbroken skin of sheep. DESIGN: Seven treatment groups of five adult sheep received systemic or topical priming followed 4 weeks later by systemic or topical boosting with choleratoxin and/or bovine serum albumin. Topical vaccines were administered to clipped skin on the ventral abdomen for 2 h. Booster immunisations were repeated 8 weeks after initial boosting. Serum antibody titres to choleratoxin and bovine serum albumin were determined by ELISA. RESULTS: An antibody response to choleratoxin was observed in serum, but no antibody response to bovine serum albumin was detected. CONCLUSION: Transdermal delivery may be feasible for livestock vaccines, however, further work is necessary to develop formulations that induce protective immunity by this route.

Adjuvants, Immunologic↗

PubMed1999

The effect of dexamethasone on some immunological parameters in cattle.

Immunosuppression as a consequence of acute and chronic stress can increase the susceptibility of cattle to a range of infectious diseases. In order to develop a panel of immune function assays for investigating the effects of potential stressors on immune competence in cattle, the effect of treatment with short- and long-acting preparations of the synthetic glucocorticoid dexamethasone was examined. Short-acting dexamethasone (dexamethasone sodium phosphate 0.08 mg/kg) followed 37 h later by long-acting dexamethasone (dexamethasone-21 isonicotinate 0.25 mg/kg) was injected intramuscularly and blood was collected to assess immune functions at intervals over the subsequent 11 days from 6 treated and 6 control Hereford steers. Dexamethasone induced leukocytosis (neutrophilia, eosinopenia, lymphopenia, monocytosis), an increased neutrophil:lymphocyte ratio, an elevated percentage of CD4+ lymphocytes, a decreased total CD8+ lymphocyte count, decreased total and percentage WC1+ lymphocytes, an elevated percentage of IL-2 receptor alpha (IL-2Ralpha)+ lymphocytes, and an elevated percentage of B lymphocytes. In vitro chemotaxis of peripheral blood neutrophils to human C5a and ovine IL-8 was increased by dexamethasone treatment. Lymphocyte proliferation in the presence of phytohaemagglutinin, and serum concentrations of IgM, but not IgA or IgG1, were suppressed by dexamethasone treatment, whereas mitogen-induced production of interferon-gamma (IFN-gamma), neutrophil expression of CD18, neutrophil myeloperoxidase activity and natural killer (NK) cell activity were not influenced by dexamethasone treatment. The results indicate the potential for haematology and immune function assays to reflect elevated activity of the hypothalamic-pituitary-adrenocortical axis in cattle. Immunological parameters may thus provide a useful adjunct to cortisol and behavioural observations for assessing the impact of stress on the welfare of cattle.

Animals↗

PubMed1999

The effect of experimental infectious mastitis on leukocyte subpopulations and cytokine production in non-lactating ewes.

The interactions between leukocytes and cytokines during the acute response to intramammary infections in the dry mammary gland of sheep were studied. Dry ewes were experimentally infected in one udder half with either Staphylococcus aureus or Escherichia coli, or infused with saline as control. Udder secretion samples, blood samples and udder tissue samples were collected before and 4, 8 and 24 h after infections/infusions. Total and differential leukocyte counts were calculated in both blood and mammary secretions, and flow cytometry was used to detect the presence of CD4+, CD8+, WC1+, IL-2R+, CD18+ or L-selectin + lymphocytes, CD18+ or L-selectin + neutrophils, and CD14+ leukocytes. Moreover, the concentrations of interleukin-1 beta (IL-1 beta), interleukin-8 (IL-8) and granulocyte-macrophage colony stimulating factor (GM-CSF) in udder secretions were measured using ELISA, and RT-PCR was used to detect the presence of corresponding cytokine mRNA in udder tissue biopsies. The results suggest an association between the concentrations of IL-1 beta, IL-8 and the intensity of neutrophil infiltration of the infected gland. Immunologically relevant changes in proportions of lymphocyte subpopulations might also occur in the acute phase of the inflammatory reaction of the udder. Greater cellular and cytokine responses to E. coli infection may have contributed to the milder clinical picture and more rapid resolution of infection than that seen for S. aureus. Enhancing the production of pro-inflammatory cytokines may improve defence against bacterial mastitis.

Animals↗

PubMed1999

Effect of intramammary infusion of beta-1,3-glucan or interleukin-2 on leukocyte subpopulations in mammary glands of sheep.

OBJECTIVE: To investigate effects of intramammary infusion of beta-1,3-glucan or recombinant ovine interleukin-2 (rOvIL-2) on blood and mammary leukocyte subpopulations and their expression of various surface antigens in sheep. ANIMALS: 12 healthy multiparous, nonpregnant, nonlactating fine-wool Merino ewes. PROCEDURE: Beta-1,3-glucan in pyrogen-free saline solution (PFSS; n = 6), rOvIL-2 in PFSS (3), or PFSS (3) was infused on days 0 and 7 in 1 udder half of each ewe. Jugular vein blood and mammary secretion samples were taken before infusion and on days 2, 7, and 21 after infusion. Total and differential leukocyte counts were obtained, and blood and mammary cells were labeled for flow cytometry. RESULTS: Slight swelling of the mammary glands was observed on day 2 after rOvIL-2 but not after beta-1,3-glucan infusion. Both substances induced significant increase in mammary secretion leukocyte numbers, compared with controls. Beta-1,3-Glucan induced an influx of monocyte/macrophages, whereas neutrophils were the predominating cell population after rOvIL-2 infusion. Beta-1,3-glucan induced selection for CD4+, B-cell+, WC1+, and L-selectin+ lymphocytes on day 14 after infusion. By comparison, rOvIL-2 induced selection for B-cell+ and L-selectin+ lymphocytes on days 14 and 21 and depletion of CD8 and, to some degree, of IL-2R+ lymphocytes. Beta-1,3-Glucan induced an increase in the proportion of CD14+ leukocytes, indicating selective migration of monocyte/ macrophages to the nonlactating udder. CONCLUSION: Beta-1,3-Glucan and rOvIL-2 can modulate nonspecific immunity in the udder of sheep but may exert their effects by differing mechanisms. Clinical Relevance-Stimulation of the nonspecific defense against udder infections may improve control of mastitis.

Animals↗

PubMed1998

Expression of surface antigens on blood and mammary leukocytes in lactating and dry ewes.

Flow cytometry was used to study the expression of CD4, CD8, CD14, CD18, WC1, MHCII, B-cell and L-selectin on CD45+ leukocytes in ovine blood and mammary secretions from lactating and dry ewes. The proportion of CD4+ lymphocytes was significantly lower and the proportion of CD8+ lymphocytes significantly higher in mammary secretions than in blood. This suggests that a selective migration to or retention of CD8+ cells in favour of CD4+ cells occurs in the mammary gland. L-selectin staining intensity on lymphocytes and neutrophils was lower in mammary secretions than in blood. In contrast, CD18 staining intensity was higher on leukocytes in milk, but not in dry secretions, than on corresponding cells in blood. These changes in adhesion molecules are in accord with shedding of L-selectin and up-regulation of CD18 during transendothelial migration. Expression of leukocyte antigens differed with lactational status mainly in mammary secretions. In milk, the staining intensity of CD18+ lymphocytes and neutrophils was higher than in dry secretions and more milk neutrophils expressed L-selectin. In contrast, greater numbers of IL-2R+ and MHCII+ lymphocytes and CD14+ leukocytes were observed in dry secretions. An increased proportion of these subpopulations could lead to increased immunological responsiveness of the udder during the dry period.

Animals↗

PubMed1998

Variation in the immune status of two Australian pig breeds.

OBJECTIVE: To investigate the variation in immune competence of two Australian pig breeds. DESIGN: A panel of immune tests were used to assess breed and sire differences in weaner piglets of Large White and Duroc breeds. PROCEDURE: All piglets were immunised against porcine leptospirosis. Blood samples were taken for studies on lymphocyte phenotypes, mitogenic responses of blood cells and serological analysis. RESULTS: Significantly larger blood leucocyte numbers were found in Large White piglets compared with Duroc piglets after vaccinations. No significant difference in concanavalin A induced blood cell proliferation was found between these two breeds before or after vaccinations. Some significant breed variation in blood lymphocyte phenotypes was found. While the age-related changes of lymphocyte phenotypes were similar for the two breeds, the Large White breed had significantly larger numbers of CD2+ and CD4+ cells than the Duroc breed after the two vaccinations. There were also significant sire effects on CD8+ cells within the Large White breed after the first vaccination. No significant breed difference was detectable in serum IgG concentrations but sire differences within each breed before the primary vaccination were found. The serum antibody response to vaccination against leptospirosis was generally small, and showed no variations due to either breed or sire. No gender effects were found during the entire study. CONCLUSION: The study demonstrated significant differences in some important immune components of the pig breeds studied. This may in turn indicate the variation in their immune competence or disease resistance. However, further investigation into the heritability and correlation with specific immune responses is required.

Agglutination Tests↗