Immunological responses of fluke-infected and fluke-free cattle to Salmonella dublin and other antigens.

Immune responses to heat-killed Brucella abortus strain 19 and to ovalbumin were compared in 15 fluke-infected and 15 fluke-free Friesian heifers. B abortus was injected 16 weeks and ovalbumin 19 weeks after the oral administration of 1000 metacercariae of Fasciola hepatica. Agglutinating antibody responses to B abortus were similar in both groups. Immediate type hypersensitivity to ovalbumin was apparently suppressed in fluke-infected animals when assessed by active and passive cutaneous anaphylaxis two weeks after sensitisation. However, when assessed by Schultz-Dale responses of intestine, in vitro, 36 weeks after sensitisation there was no difference between the groups. The heifers were subsequently given live Salmonella dublin intravenously. The fluke-infected animals which became carriers of S dublin had the most persistently elevated titres of agglutinating antibodies in their sera and the highest incidence of immediate-type hypersensitivity, as assessed by Schultz-Dale responses of intestine, but the weakest cutaneous delayed hypersensitivity reactions to S dublin. The latter might have been related to lymphopenia which developed after fluke infection. The increased susceptibility of fluke-infected cattle to S dublin cannot be attributed to impaired agglutinin responses but may result from effects on cell-mediated mechanisms.     

An ELISA for the detection of anergic tuberculous cattle

An enzyme-linked immunosorbent assay (ELISA) for bovine antibody to antigens in unheated Mycobacterium bovis culture filtrate was standardised against a reference serum from an experimentally infected cow. Two Northern Territory herds with a total of 561 cattle were tested. All cattle reacting in the caudal fold tuberculin test, those giving strong reactions in the ELISA and those with visible lesions of tuberculosis were subjected to a detailed bacteriological examination. Of the 19 cattle which yielded isolates of M. bovis, only 4 were positive to the tuberculin test. Serum samples from 5 cattle gave ELISA values greater than 7.0 units. None of these 5 reacted in the tuberculin-test and 2 had no visible lesions. Of the 10 remaining cattle from which M. bovis was isolated, 3 had ELISA values between 6.5 and 7.0 units and were also without visible lesions. The ELISA values for the remaining 7 infected cattle ranged down to 4.6 units. Forty cattle yielded no M. bovis on culture of their tissues. They included 7 which were reactors in the tuberculin test and 23 with ELISA values of 7.0 units or more. The evident low specificity and sensitivity of the ELISA make it of little value as an alternative to the tuberculin test, but it can detect some anergic cattle at the cost of increasing the number of false positive reactors. This may be acceptable in some circumstances and would justify the use of the ELISA as a complement to the tuberculin test or to an in vitro assay of T-cell immunity. In the 2 Northern Territory herds described, the removal of 5 of the anergic cattle would have required a cull of 28 animals of 5% of the total. A cut off value of 6.5 units would have eliminated 3 more, but at the cost of culling 80 animals or nearly 15% of the cattle. Even so, 7 cattle from which M. bovis was isolated would have remained undetected by either test.     

Salmonella Dublin infection in dairy cattle: risk factors for becoming a carrier

Long-term Salmonella Dublin carrier animals harbor the pathogen in lymph nodes and internal organs and can periodically shed bacteria through feces or milk, and contribute to transmission of the pathogen within infected herds. Thus, it is of great interest to reduce the number of new carrier animals in cattle herds. An observational field study was performed to evaluate factors affecting the risk that dairy cattle become carrier animals after infection with Salmonella Dublin. Based on repeated sampling, cattle in 12 Danish dairy herds were categorized according to course of infection, as either carriers (n = 157) or transiently infected (n = 87). The infection date for each animal was estimated from fecal excretion and antibody responses. The relationship between the course of infection (carrier versus transiently infected) and risk factors were analyzed using a random effect multilevel, multivariable logistic regression model. The animals with the highest risk of becoming carriers were heifers infected between the age of 1 year and 1st calving, and cows infected around the time of calving. The risk was higher in the first two quarters of the year (late Winter to Spring), and when the prevalence of potential shedders in the herd was low. The risk also varied between herds. The herds with the highest risk of carrier development were herds with clinical disease outbreaks during the study period. These findings are useful for future control strategies against Salmonella Dublin, because they show the importance of optimized calving management and management of heifers, and because they show that even when the herd prevalence is low, carriers are still being produced. The results raise new questions about the development of the carrier state in cattle after infection with low doses of Salmonella Dublin.     

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)     

Use of an ELISA for serodiagnosis of parasitic bronchitis in cattle.

The enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of parasitic bronchitis in cattle was evaluated in naturally injected, experimentally infected and vaccinated animals. Significant antibody titres could be demonstrated from five weeks after animals had been exposed to the parasite, so that infected animals could be identified during the summer. The test did not give false positive results in vaccinated animals. The technique proved particularly useful in revealing latent infections in milking herds in the autumn when heavy burdens of worms in the lungs do not generate any larvae in the faeces.     

Salmonella dublin in Danish dairy herds: frequency of change to positive serological status in bulk tank milk ELISA in relation to serostatus of neighbouring farms

Bulk tank milk from 1,429 herds were collected in 3 rounds from 19 different geographic areas. The milk samples were tested by use of indirect LPS-ELISA procedure to detect Salmonella dublin antibodies. From the obtained OD-values herd seroprevalence in the given area was determined and GR-scores calculated for each herd by addition of the number of positive sampling rounds by the 5 geographically closest neighbour herds. In the 19 different areas the calculated prevalence ranged from 0.01 to 0.41. Totally 3,697 GR-scores were given. The mean GR-scores in the areas ranged from 0.0 to 6.5. Higher GR-scores were found in herds changing to seropositive status compared with herds seronegative throughout the study period. The results indicate that the risk for a dairy herd to receive S. dublin infection increases with the disease status among the nearest neighbours and with the prevalence of seropositive herds in the geographic area.     

牛皮蝇蛆病间接ELISA诊断方法的建立

以纹皮蝇Ⅰ期幼虫粗提蛋白为包被抗原,通过方阵试验确定了血清最佳稀释倍数为80倍,抗原最佳包被浓度为26.64μg/mL,并对其特异性、敏感性和重复性进行了试验,建立了牛皮蝇蛆病间接ELSIA诊断方法。再以建立的ELISA诊断方法对采自内蒙古地区的233份牛血清进行了检测。结果表明,所建立的牛皮蝇蛆病间接ELISA诊断方法具有较好的特异性、敏感性和可重复性,可用于牛皮蝇蛆病的血清学检测。     

Investigation of a cutaneous delayed hypersensitivity response as a means of detecting Salmonella dublin infection in cattle

Delayed hypersensitivity reactions developed 48 to 96 h after intradermal injection of killed Salmonella dublin in 25 of 28 cattle which had been inoculated intravenously, and in five of 10 cattle which had been inoculated orally with S dublin 24 to 493 days previously. Control animals showed no delayed hypersensitivity reactions. Persistence of infection in five of the intravenously inoculated and in four of the orally inoculated animals was confirmed by isolation of S dublin from the carcases at necropsy one week after skin testing. Failure to isolate the organism from the carcases of 21 animals which had reacted positively to the intradermal test did not eliminate the possibility of their being carriers of S dublin. Skin testing was concluded to be a reliable means of identifying animals which had been, and possibly still were, infected systemically with S dublin. However recovered animals might be falsely identified as infected. Repeated testing gave misleading results.     

Detection of Salmonella dublin mammary gland infection in carrier cows, using an enzyme-linked immunosorbent assay for antibody in milk or serum

An ELISA has been developed for measurement of milk and serum IgG concentrations directed against Salmonella dublin. Four groups of cows were studied: group A--7 experimentally challenge-exposed cows (infected, recovered group); group B--6 normal uninfected randomly selected control cows; group C--7 naturally occurring S dublin carrier cows; and group D--6 normal uninfected S dublin negative cows from the same herd as group C. Group-A cows were inoculated orally, or inoculated orally and then IV, but none became a S dublin carrier. As expected, all 7 group-A cows responded with a marked increase in ELISA titer after oral exposure to virulent S dublin, starting with a mean serum titer of 17.7% and reaching a peak mean serum titer of 79.3% approximately 76 days after initial exposure. As determined by necropsy and organ culturing of the remaining cows, none of the group-A cows became carriers. The mean serum ELISA titer for group-B uninfected control cows was 14.1% (SD +/- 12.8%). The mean milk ELISA titer was -1.0% (SD +/- 5.5%). Colostrum and then milk gave false-positive results for up to 2 weeks after onset of lactation. Group-B cows were culture negative for S dublin in feces and milk during lactation, and when tissues were cultured after euthanasia. Milk and serum samples for ELISA, and milk and fecal samples for culturing were taken from all group-A and -B cows twice a week for 6 months. Statistical correlation (P less than 0.05) was found between serum and milk ELISA titers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunizing efficacy of aromatic-dependent Salmonella dublin in mice and calves

Mice immunized with an aromatic-dependent (aro-) S. dublin strain CS101 by either the intraperitoneal (i.p.) or oral route, were protected against oral challenge with a virulent S. dublin strain CS90, the degree of protection being the greatest when mice had received 3 immunizing doses at weekly intervals. Mice immunized with an aromatic-dependent (aro-) S. typhimurium strain CS332 by the i.p. or oral routes were protected against challenge with virulent S. dublin strain CS90 at 1 or 2 weeks but not at 3 or 4 weeks post-immunization. Mice immunized with 1 dose of aro- S. dublin strain CS101 by the i.p. route developed low levels of lipopolysaccharide (LPS) and flagellin-specific antibody but no delayed-type hypersensitivity (DTH) whereas those immunized with 2 or 3 doses developed significantly higher antibody titres and DTH. In contrast, mice immunized by the oral route developed neither significant antibody response nor DTH. The aro- S. dublin strain CS101 could not be detected beyond day 28 post-inoculation in visceral organs including liver, spleen, mesentery, small intestine, caecum or large intestine of mice inoculated by the i.p. route or in mice inoculated by the oral route with the exception of day 42 post-inoculation. Challenge of mice previously immunized with 3 doses of the aro- S. dublin strain CS101 by the i.p. or oral route with virulent S. dublin strain CS90 resulted in their rapid clearance from the above visceral organs. Calves immunized with the aro- S. dublin strain CS101 by either the intramuscular (i.m.) or oral routes were significantly protected against oral challenge with virulent S. dublin strain CS90. In contrast to the observations in mice, somatic (O) and flagellar (H) antibody titres of calves immunized by either route were negligible as were anti-LPS antibody titres. However, flagellin-specific antibody titres were higher in calves immunized by the i.m. than the oral route. These results indicate that the protection observed in immunized mice or calves against oral challenge with virulent S. dublin was unlikely to have been mediated by humoral salmonella-specific immune mechanism(s).     

Effect of calf age and Salmonella bacterin type on ability to produce immunoglobulins directed against Salmonella whole cells or lipopolysaccharide.

A commercially available Salmonella bacterin was administered to Holstein calves starting at 1 to 19 weeks of age. Serum samples were obtained before administering bacterin and at 2-week intervals thereafter. An ELISA with Salmonella dublin lipopolysaccharide (LPS) or S dublin whole cells as antigen, was used to measure specific IgG and IgM responses. Antibody responses to LPS were not detected from calves < 12 weeks old inoculated with killed bacterin. Immunoglobulin responses to whole-cell antigen were detected from all age groups of calves inoculated with the same killed Salmonella bacterin. Calves < 11 weeks old are able to produce immunoglobulins to some whole-cell antigens, but are unable to produce anti-LPS immunoglobulins when inoculated with killed Salmonella bacterin. This age-related response to killed Salmonella antigens may account, in part, for increased susceptibility to salmonellosis in calves < 12 weeks old. In comparison to the response for killed antigen, 8 calves given modified-live aromatic-dependent S dublin bacterin at 1 to 3 weeks of age had detectable anti-LPS immunoglobulins after immunization, although the response was not as rapid and was of a lesser magnitude than that of older calves given killed Salmonella bacterin.