Farm factors associated with the presence of Mycobacterium paratuberculosis infection in dairy herds on the New York State Paratuberculosis Control Program

An extensive questionnaire was developed and used to collect data from 33 herds that were on the New York State Paratuberculosis Control Program, to study farm factors associated with the presence of Mycobacterium paratuberculosis infection in dairy herds. The results of the last whole herd paratuberculosis fecal culture were used to indicate presence of infection in a herd, with herds having one or more animals positive classified as ‘infected’. The average prevalence within herds was 5.2%. Fourteen herds were uninfected and 19 herds had prevalences ranging from 0.7%–28.2%. Data on 31 continuous and 67 categorical risk factors were collected by questionnaire. Ten factors were significantly associated with prevalence risk of infection in the univariable logistic regression. These factors were: the type of farm operation (commercial/registered or both); earlier diagnosis of the disease before entering the control program; number of clinical cases in the previous year; whether clinical cases were raised or purchased animals; typical signs in clinical cases; exposure of calves 0–6 weeks of age to feces of adult cows; contact of young stock with adult animal feces from using the same equipment to clean the housing for both groups of animals; spreading feces on fields from which forage is later harvested and fed to animals of any age group; what is done with animals that are suspected of having paratuberculosis or test positive on culture; and frequency of cleaning the cow barn. Stepwise logistic regression was used to determine the significance of each risk factor while controlling simultaneously for the effect of other factors. The significant factors were the type of farm operation, clinical signs, and exposure of calves to feces of adult cows. Commercial herds, presence of clinical signs typical of paratuberculosis in animals, and exposure of calves 0–6 weeks old to feces of adult cows all indicate a higher likelihood that a herd is infected with M. paratuberculosis.     

Distribution and hybridization patterns of the insertion element IS900 in clinical isolates of mycobacterium paratuberculosis

Reference strains and 31 clinical isolates of M. paratuberculosis, mainly from goats, were analysed for restriction fragment length polymorphism (RFLP). Restriction digests of bacterial DNA were hybridized with a repetitive insertion sequence, IS900, to obtain banding patterns for comparison of strains. Twenty-five of the 31 field-strains hybridized with IS900, and five hybridization patterns were identified. It was not possible to identify specific patterns for goat strains of M. paratuberculosis. Four hybridization patterns were similar, whereas the fifth pattern of a sheep strain diverged considerably in position and number of band. Six goat strains failed to hybridize with IS900, and the absence of IS900 was verified by the polymerase chain reaction and hybridization with an oligonucleotide probe. The six IS900-negative goat strains had diverging phenotypic properties, and the identification of these strains is discussed. The present study shows that M. paratuberculosis strains infecting goats are genetically similar to cattle strains and that IS900 is a specific genetic element for identification of M. paratuberculosis.     

Analysis of antigens in Mycobacterium paratubercuolsis.

Analysis of antigens in Mycobacterium paratuberculosis. Acta vet. scand. 1979, 20, 200–215. — Using crossed immunoelectrophoresis (GIE) and crossed line immunoelectrophoresis (GLIE), antigens from different strains and variants of Mycobacterium paratuberculosis were compared, and cross-reactions between 1 of these strains and Mycobacterium avium and BGG studied. In each of 4 bovine laboratory strains of M. paratuberculosis examined, altogether 44 different antigens were demonstrated. This is the largest number of antigens in M. paratuberculosis which has been described so far. No important difference in the antigenic structure of the strains was found. The 4 laboratory strains are being used routinely in the production of vaccine against Johne’s disease in Norway and Iceland. One of the aims of the present work was to investigate the antigenic relationship between these strains and the goat-pathogenic Norwegian and the Icelandic variant of M. paratuberculosis. Out of 44 different antigens demonstrated in the laboratory strains, 39 and 31 gave cross-reactions against the Norwegian and the Icelandic variant, respectively. This is in accordance with practical experience, as the results of vaccination against Johne’s disease, performed in Norway for many years, are very good.Twenty-seven and 24 cross-reacting antigens between M. paratuberculosis and strains of M. avium and BGG, respectively, were observed. This finding agrees with clinical observations.Another aim of the investigation was to identify species-specific antigens as regards M. paratuberculosis. One antigen showed a marked cross-reaction between the strains of M. paratuberculosis examined, but did not react with antisera against M. avium and BGG. Some other antigens showed partial specificity.The results obtained stress the complicated antigenic situation in mycobacteria which is of decisive significance as regards the diagnosis and classification of mycobacterial infections.     

Lesions attributed to vaccination of sheep with Gudair for the control of ovine paratuberculosis: post farm economic impacts at slaughter

OBJECTIVE: To determine i) the prevalence of lesions at the site of vaccination with Gudair, and ii) the incidence of discounting of slaughtered sheep carcasses due to the presence of these lesions. DESIGN: A survey of the prevalence of injection lesions and actual discounts applied to 20 consignments of vaccinates slaughtered in abattoirs in New South Wales. PROCEDURE: Consignments of sheep previously vaccinated against ovine Johne's disease (OJD) were assessed on the slaughter chain for the prevalence of vaccination site lesions and any costs associated with carcass trimming were estimated. In addition a telephone survey was conducted to determine the experiences and risk attitudes of 8 abattoirs in south east New South Wales likely to have previously processed vaccinates. RESULTS: The prevalence of lesions observed was 18% for adult (mutton) and 65% for lamb carcasses. The value of the trim removed was insignificant, the labour cost of its removal was nil and no carcass was downgraded to a lower value grade. CONCLUSION: Under the market conditions existing at the time the study was conducted, in sheep vaccinated at the recommended site high on the neck, it is unlikely that OJD vaccination site lesions will be a significant cost to producers or the processing industry and will represent only a very small proportion of the total cost of OJD control by vaccination.     

Survival of Mycobacterium avium subsp. paratuberculosis in bovine monocyte-derived macrophages is not affected by host infection status but depends on the infecting bacterial genotype

In this study we investigated the ability of different Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) strains to survive in bovine monocyte-derived macrophages (MDMs) of cows naturally infected with M. paratuberculosis and control cows. We tested the hypotheses that infection status of cows affects macrophage killing ability and that survival of M. paratuberculosis in macrophages is dependent on the strain. Peripheral blood mononuclear cells (PBMC) were obtained from Johne's disease-positive (n = 3) and age and stage of lactation matched Johne's disease-negative (n = 3) multiparious cows. Following differentiation, MDMs were challenged in vitro with four M. paratuberculosis strains of different host specificity (cattle and sheep). Two hours and 2, 4, and 7 days after infection, ingestion, and intracellular survival of M. paratuberculosis strains were determined by fluorescence microscopy. There was no effect of the origin of MDMs (Johne's disease-positive or control animals) on phagocytosis, survival of bacteria, or macrophage survival. In contrast, important strain differences were observed. These findings suggest that some M. paratuberculosis strains interfere more successfully than others with the ability of macrophages to kill intracellular pathogens which may make it important to include strain typing when designing control programs.     

Effect of Mcl-1 signaling pathway blockers on apoptosis of mouse macrophages infected with Mycobacterium tuberculosis H37Rv

AIM: To explore the effects of Mcl-1 signal pathway blockers on Mcl-1 expression, macrophage apoptosis and Mycobacterium tuberculosis in the model of mice infected with Mycobacterium tuberculosis H37Rv. METHODS: A mouse infection model was established by intraperitoneal injection of H37Rv suspension. The signaling pathway blockers AG490, PD98059 and LY294002 for JAK/STAT, MAPK and PI3K, respectively, were intraperitoneally injected into the mice infected with H37Rv. Cell acid-fast staining was used to observe whether the mouse peritoneal macrophages infected with H37Rv were successfully established. Immunocytochemical method was employed to detect Mcl-1 expression in the mouse peritoneal macrophages infected with H37Rv. The apoptotic rate in each group was measured by flow cytomerty. The scavenging capacity of apoptotic macrophages against H37Rv was determined by Mycobacterium tuberculosis colony counting. RESULTS: The result of cell acid-fast staining revealed the existence of dispersive arrangement of red short antiacid Mycobacterium tuberculosis within infected macrophages. The result of cell immunocytochemistry showed strongly positive expression of Mcl-1 protein in H37Rv infection group, AG490 treatment group and LY294002 treatment group, weakly positive expression of Mcl-1 protein in PD98059 treatment group, and negative expression of Mcl-1 protein in control group. The result of flow cytometry found that the macrophage apoptotic rate in H37Rv infection group was higher than that in control group, while that in PD98059 treatment group was high than that in other groups with statistically significant differences (P<0.05). The result of Mycobacterium tuberculosis colony counting showed that PD98059 treatment had the most significant inhibitory effect on H37Rv strain. CONCLUSION: Mcl-1 signaling pathway blockers increase the apoptotic rate of macrophages infected with Mycobacterium tuberculosis H37Rv and inhibit the growth of Mycobacterium tuberculosis by inhibiting the signaling pathways of JAK/STAT, MAPK and PI3K, among which the MAPK has the most obvious interfering effect on Mcl-1, and leads to the highest apoptotic rate of infected macrophages and the strongest bacteriostasis.     

The pathogenesis of experimental endo-bronchial Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula)

Aim. To study the nature and development of experimentally induced respiratory tuberculosis in possums and compare the lesions observed with those seen in the natural disease.

Methods. Thirty-three adult possums were inoculated via the endo-bronchial route with 20–100 colony forming units of Mycobacterium bovis. The possums were killed at 1, 2, 3 and 4 weeks after inoculation and the nature and distribution of the lesions studied in detail histopatbologically. Alveolar macrophages recovered from the infected possums were also studied ultrastructurally.

Results. Macroscopic lesions were largely confined to the respiratory tract, increasing in size and number with time. Histology greatly increased the detection of the total number of lesions. The most common sites affected outside the respiratory tract were the liver and hepatic lymph nodes, but lesions were less common in peripheral lymph nodes than is observed in the natural disease. Intra-pulmonary lesions were centred on blood vessels and their associated lymphatics. Peripheral blood lymphocyte blastogenic responses to M. bovis antigens were first detected at 3 weeks after inoculation, which was 1 week after lymphocyte infiltrations were detected in the lungs, but 1 week before the majority of infections became generalised.

Conclusions. Differences in the nature of pulmonary lesions and the distribution of lesions were observed between experimentally induced and the natural disease. Rapid haematogenous and lymphatic spread occurs early in the experimentally induced disease.     

Intra-uterine transmission of Mycobacterium avium subsp paratuberculosis in subclinically affected red deer (Cervus elaphus)

AIM: To determine the rate of transmission of Mycobacterium avium subsp paratuberculosis (M. ptb) from hind to fetus in utero, and the risk of transmission from dam to fawn via infected colostrum and milk in subclinically affected red deer hinds.

METHODS: Hinds were sourced from farms in Otago or Southland and selected for the study if they were positive to the immunoglobulin G1 (IgG1) modified enzyme-linked immunosorbent assay (ELISA) (Paralisa) and exhibited no clinical signs of Johne's disease. The hinds (n=35) were sent to a deer slaughter premises (DSP; n=31) or were killed on-farm (n=4). All post-mortem samples were collected from the fetus first and then from the dam, taking care to avoid cross contamination between samples. Fresh samples (n=185) were collected for culture, and tissue samples (n=72) were collected from 24 hinds and their fetuses for histopathological examination.

RESULTS: A total of 24/35 hinds selected were suitable for inclusion in the study. Eighteen of these pregnant hinds were culture-positive for M. ptb, and 14 of these had culture-positive fetuses, representing a transmission rate of 78% (95% confidence interval (CI) =0.58–0.98) from dam to fetus. Of the 16 mammary glands sampled, 11 (69%) were culture-positive for M. ptb while 12/15 (80%) mammary lymph nodes sampled were also culture-positive.

CONCLUSIONS: This study demonstrated a high rate of transmission of M. ptb from dam to fetus in red deer, and a potential risk of transmission to fawns suckling from mothers that are subclinically affected with Johne's disease.     

Adenovirus precipitating antibodies in the sera of brush-tailed possums in New Zealand

Sera collected from the Australian brush-tailed possum Trichosurus vulpeculu in New Zealand in 1975 and 1989 were tested for the presence of antibodies to adenovirus. Of the 231 sera tested in an agar gel diffusion test, eight (3.5%) had precipitating antibodies to the group specific antigen of mammalian adenoviruses. Available data allowed 99/231 sera to be classified as being obtained from either adult (total 62) or sexually immature (total 37) possums. From the adult animals, 4/62 (6.5%) sera were positive, while no reactive sera were detected among the 37 immature animals. The results provide evidence that natural infection by an adenovirus occurs in possums in New Zealand. Further work needs to be carried out to isolate this adenovirus to enable detailed serological and epidemiological studies to be performed. A species-specific “possum adenovirus” could have potential in the biological control of this species.     

A survey of rats trapped in the wellington area for ectoparasites and organisms of the salmonella,pasteurella, and leptospiral groups

Extract

It has long been established that rats can play an important part in the transference of infectious diseases to man. With this fact in mind, the late Dr J. H. Blakelock, former Director of the National Health Institute, Wellington, began a survey of the rat population in the Wellington district and of rats brought to the area by overseas ships. This work has been continued, the trapped rats being examined for the presence of Xenopsylla cheopis, a flea known to be the chief vector of plague, for Pasteurella pestis, the causative organism of plague, for organisms of the Salmonella group, and for evidence of leptospiral infection.