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In cattle, Coxiella burnetii infections are generally asymptomatic but can also be associated with reproductive disorders. Metritis is considered as one of the symptoms of C. burnetii infections, but reliable information is lacking. Therefore, information on the presence of C. burnetii in the uterine content of cows with metritis is important to increase our knowledge on this pathogen. In this study, the uterine content of 45 dairy cows with metritis belonging to 12 herds was tested for C. burnetii with a real-time PCR assay. Only one uterine sample tested PCR (highly) positive, all other samples were PCR negative. The PCR positive cow tested also positive for antibodies. Three other cows from other herds tested antibody positive. The bulk milk (BM) samples of these 12 herds were tested by real-time PCR assay and antibody-ELISA. Six BM samples (50%) were positive in PCR and 10 (83%) were positive in ELISA. Culturing the uterus samples by bacteriology, the most frequently cultured bacteria were arcanobacterium (n=24), E. coli (n=16), other streptococci (n=10), Streptococcus uberis (n=8) and Streptococcus dysgalactiae (n=5). This study indicates that C. burnetii is not an important cause for metritis in dairy herds, although apparently C. burnetii was or had been present in most of these herds., (Copyright © 2010 Elsevier B.V. All rights reserved.)

In the past decades, vaccination against paratuberculosis in cattle was performed in The Netherlands only on a limited scale. Because of its interference with the diagnosis of bovine tuberculosis, vaccination was restricted to herds with a high prevalence of clinical cases of paratuberculosis and was meant to aid in the economical survival of the farm. Recently, a voluntary paratuberculosis certification program has started, based in part on serological screening of cattle of at least 3 years of age. Herds that have been vaccinated against paratuberculosis are, therefore, likely to encounter problems when entering this program. The aim of this study was to evaluate the immune response resulting from vaccination with a heat-killed paratuberculosis vaccine. Over a period of 12-14 years, new-born calves were vaccinated in two herds. The B-cell response was evaluated using both the complement-fixation test (CFT) and an enzyme-linked immunosorbent assay (ELISA) and the cell-mediated immune response was evaluated using the gamma-interferon assay. Data obtained show a marked and prolonged effect of the vaccination on both cellular and humoral immune responses, in particular to the paratuberculosis antigen but also to the bovine tuberculosis antigen, using the respective tests. These responses were detected rapidly after vaccination. The individual responses were highly variable between animals with respect to both the level and to the duration of the evoked immune response. No relation between the results obtained with the ELISA and the CFT was observed. In conclusion, for a large number of vaccinated cattle, a long lasting interference is to be expected with the presently available immunodiagnostic methods for both bovine tuberculosis and paratuberculosis.

A total of 50 sheep originating from 15 Dutch farms with a known paratuberculosis infection in their cattle herd, but with no history of paratuberculosis infection in their sheep flock, were examined for infection with Mycobacterium avium subsp. paratuberculosis (Map). The sheep had been grazing on the same pastures as the cattle or on pastures fertilised with manure from these cows. The sheep were screened for paratuberculosis by serum biochemistry, serology and intradermal skin tests. At necropsy they were examined macroscopically, microscopically and bacteriologically for paratuberculosis. From 10 sheep, originating from eight flocks, Map could be isolated from various tissues but not from the intestinal contents, after an incubation period of 2.5-4 months. Six of these culture-positive sheep had no macroscopic signs of paratuberculosis at necropsy. Seven sheep were Map culture negative but showed macroscopic and microscopic lesions consistent with a paratuberculosis infection. Results of serology and skin tests did not correlate with the results of bacteriological culture. Serum concentrations of calcium, albumin and total protein of the infected, suspected and negative sheep were not different. These results indicate that a substantial number of the sheep examined were infected with Map. Even though this bacterium was not isolated from their faeces, the possibility that these sheep could have been shedding Map with their faeces below detection level or at a later stage of the disease cannot be eliminated. Map infected sheep should, therefore, be considered as a possible factor in the epidemiology of with Map infected cattle herds in The Netherlands. At necropsy bacteriological culture of Map should be performed on a routine basis to improve the diagnosis of paratuberculosis in sheep.

In the Netherlands a survey was conducted to estimate the prevalence of paratuberculosis in dairy herds. In total 15822 cows of at least 3 years of age, belonging to 378 herds were tested using an absorbed ELISA. Of these herds, 55% (n=207) had one or more serologically positive cows. Of the positive non-vaccinated herds, most had one (n=98) or two (n=49) positive cows. The percentage positive cows per herd was 2.5+/-3.2%.The true prevalences on cow and herd levels, based on a test sensitivity that ranged from 0.3 to 0.4 and a specificity that ranged from 0.985 and 0.995, were estimated at 2. 7-6.9% and 31-71%. Seven herds had been vaccinated against paratuberculosis and these herds had a significantly higher percentage of serologically positive cows (23%) than the non-vaccinated herds (2.5%). In conclusion, a small percentage of the dairy cows and a high percentage of the dairy herds in the Netherlands is serologically positive. The percentages true infected cows and herds are difficult to estimate precisely due to uncertainties in test sensitivity and specificity.

An antigen prepared from a mucoid strain of B. abortus was repeatedly injected intradermally into cattle to determine whether it sensitizes cattle so that they test false positive with the skin delayed-type hypersensitivity (SDTH) test. Cattle (n = 14) that were experimentally inoculated. with microorganisms that serologically cross-react with B. abortus, and uninfected cattle (n = 15) were tested with the antigen 2 to 5 times over a period of 16 to 17 weeks. An increase in skinfold thickness of > or = 2.0 mm on the injection site was considered a reaction elicited by the antigen. The sera from the cattle were tested with the serum agglutination test, complement fixation test, and an enzyme-linked immunosorbent assay for antibodies against B. abortus. Results showed that none of the animals had an increase in skinfold thickness of > or = 2.0 mm on the injection site of the antigen, which is considered a positive reaction. However, cattle experimentally inoculated with microorganisms other than B. abortus tested seropositive for brucellosis after one SDHT test only. We conclude that the B. abortus antigen inoculated intradermally does not sensitize cattle after repeated inculations, and therefore does not interfere with the subsequent use of the SDTH test in the diagnosis of brucellosis.

A study was conducted to determine whether an allergen that has been prepared from a mucoid strain of Brucella abortus triggers a serum antibody response that interferes with the interpretation of serologic tests results. Fifteen cattle seronegative for Brucella antigen were tested with the SDTH test several times. Blood samples were collected weekly and tested with the serum agglutination test and complement fixation test. Results show that some cattle tested seronegative after each of the SDTH tests while other cattle tested weakly positive with the serum agglutination test or the complement fixation test. All seropositive cattle tested seronegative 4-7 weeks after the last SDTH test indicating an antibody response of a transient nature. We conclude that serologic tests results indicating infection are reliable when recorded four weeks after a single SDTH test. If cattle are tested with the SDTH test several times an interval of seven weeks should be observed after the last test to ensure a reliable interpretation of the serologic test results.