Allergic tests on cattle vaccinated against Johne's disease

Giardia intestinalis cysts were detected in faeces from 12.9% of 124 brushtail possums (Trichosurus vulpecula) trapped in Auckland, Hawke's Bay, the Wairarapa and Wellington; in faecal material from 61.0% of 77 ship rats (Rattus rattus) from areas of Auckland, Hawke's Bay and Wellington; and in faecal material from 25.3% of 182 house mice (Mus musculus) from the North Island. Possums and rodents in forested areas of Auckland and Wellington city water catchments were infected. The role of wild animals in maintaining and spreading Giardia in New Zealand is discussed.     

Mucosal immune response in cattle with subclinical Johne's disease

Mycobacterium avium subsp. paratuberculosis is the causative agent of Johne's disease, a chronic granulomatous enteritis of wild and domestic ruminants. During a long subclinical period, the organism persists in the intestine despite systemic cellular and humoral immune responses. To explore the mucosal immune response in Johne's disease, we isolated mononuclear leukocytes from the ileum of cows naturally infected with M. avium subsp. paratuberculosis and from cows that were not infected. We evaluated the immunophenotype of these cells and the proliferative responses after the addition of M. avium subsp. paratuberculosis sonicate or B-cell or T-cell mitogens. Although the percentage of T cells was increased in infected cows, these cells consisted mostly of memory (CD2+CD62L-) and regulatory (CD4+CD25+) T cells. Further evidence of immune hyporesponsiveness included a decrease in the percentage of T cells with an activated phenotype and a decrease in cells expressing major histocompatibility factor class II (MHC class II). Unlike the spleen, ileal lymphocytes from infected cows failed to proliferate in response to M. avium subsp. paratuberculosis sonicate. Additionally, ileal lymphocytes from infected cows proliferated poorly in response to concanavalin A and pokeweed mitogen, suggesting generalized T cell and B cell hyporesponsiveness. These results indicate that a state of tolerance may exist in the intestine of cows subclinically infected with M. avium subsp. paratuberculosis organisms in subclinically infected cows. This effect may be induced, at least in part, by proliferation of regulatory T cells that nonspecifically suppress mucosal immune responsiveness.     

Skin sensitivity to tuberculins in cattle vaccinated against Johne's disease

Aim: To evaluate the efficacy of a dry-cow antibiotic preparation containing cloxacillin plus ampicillin in a formulation that gives a 10-week duration of action, in comparison to products containing cephalonium (10-week action) or cloxacillin alone (7-week action).

Methods: A total of 493 cows were selected from 6 spring-calving dairy herds in the Manawatu region of New Zealand, according to the criteria of the SAMM plan, to receive intramammary antibiotic therapy at the end of lactation (drying off). Cows were randomly allocated to receive 1 of the 3 dry-cow antibiotic products under investigation. Cows were examined twice during the dry period and twice daily during the first 10 days of their subsequent lactation for the presence of mastitis. Milk samples were collected from individual quarters at the time of drying off and at 7 and 28-35 days after calving, for determination of milk somatic cell counts (SCC). Bacteriology was carried out on milk samples taken from cows that developed mastitis during the first 10 days after calving.

Results: No cows developed mastitis during the dry period. Sixteen cows developed clinical mastitis within 10 days of calving; there was no difference in incidence between treatments. Streptococcus uberis was the most commonly isolated organism. Mean SCC on Day 7 were lower (p = 0.019) in cephalonium-treated quarters (189.9 ± 28.4 × 10³ cells/ml) than in cloxacillin-treated quarters (388.7 ± 71.2 x 10³ cells/ml); values in quarters receiving cloxacillin plus ampicillin were intermediate (252.0 ± 47.0 × 10³ cells/ml). SCC were similar between treatment groups on Day 28–35.

Conclusions: The use of a combination of cloxacillin plus ampicillin was effective for the prevention of mastitis during the dry- and peri-calving-periods in pastured dairy cattle.     

Evaluation of diagnostic tests for Johne's disease in young cattle

OBJECTIVE: To investigate the development of immune responses in calves experimentally and naturally infected with Mycobacterium paratuberculosis and to evaluate the potential for diagnostic tests to detect infected calves. DESIGN: Sequential testing of four treatment groups of calves over a 2 year period. PROCEDURE: Twenty-nine calves were allocated to four groups. Group D calves were orally dosed with M paratuberculosis, group N calves naturally exposed to M paratuberculosis, group V calves vaccinated for M paratuberculosis, and group C were control calves (not infected or vaccinated). Blood and faecal specimens were collected from each calf at monthly intervals to 18 months of age and then every 2 months until they were slaughtered between the ages of 21 and 29 months. Specimens were tested using absorbed EIA, IFN-gamma EIA and faecal culture. The infection status of the calves was confirmed by extensive histopathological examination and tissue culture. RESULTS: M paratuberculosis infection was confirmed in 10 calves, comprising six of eight orally dosed calves, three of five naturally exposed calves and one of nine vaccinated calves. The six artificially infected calves and one naturally infected calf were detected shedding M paratuberculosis in their faeces. Results with positive absorbed EIA were obtained from one artificially infected calf, one naturally infected calf and three vaccinated calves. All calves including controls had positive results on at least one occasion using the IFN-gamma EIA. In addition, seven calves had positive bovine tuberculosis results using the IFN-gamma EIA, even though bovine tuberculosis has been eradicated from Australia. CONCLUSION: Detection of M paratuberculosis infection in young cattle continues to be difficult using current tests.     

Experimental paratuberculosis (Johne's disease)--studies on biochemical parameters in cattle

Ten male Holstein-Friesian calves naturally infected by Mycobacterium paratuberculosis were experimentally re-infected orally at an average of 17 days. Monthly measurements were conduced of the following activities, in the period between post infection days 160 and 400: total protein (TPR), albumin (ALB), cholesterol (CHOL), triglycerides (TRIG), Zn and Cu concentrations as well as sorbitol dehydrogenase, lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (alpha-HBDH), gamma-glutamyltransferase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), alkaline phosphatase and fructose-1,6-diphosphate aldolase (ALD). TPR, ALB, TRIG, and CHOL were reduced by day 400, in conjunction with disorders of digestion and absorption. Increased activities of CK, ALD, LDH, alpha-HBDH, AST and ALT primarily indicated damage to skeletal muscle and/or liver. Serum CK and ALD activities as well as TRIG and TPR concentrations may serve as aids to specific diagnosis of paratuberculosis, particularly in the advanced stage of the disease.     

Financial effect of bovine Johne's disease in beef cattle herds in Australia

Objective To assess the financial effect of programs for controlling bovine Johne's disease (BJD) in beef herds. Design A spreadsheet simulation model of a self‐replacing beef herd in south‐eastern Australia selling 400‐kg steers at 15 months old. Methods The model calculated the monthly cash flow, and net present value (NPV) of cumulative cash flow, over 10 years. Four main control options were compared: (1) a base herd (no action to control the disease), (2) test and cull, and (3) partial and (4) total destocking. It was assumed that BJD was eradicated after 3 and 5 years with total and partial destocking, respectively, and not eradicated with a test and cull program. Scenarios were compared for both commercial and stud enterprises. Results If there was no discount on the sale price of cattle in commercial herds, deaths from BJD had to exceed 5% before the NPV of partial or total destocking was similar to taking no action to control the disease over a 10‐year period. When cattle sales incurred a 10% discount, deaths had to exceed 1% before the destocking strategies would break even after 10 years. Conclusion Control options for BJD should be carefully planned on an individual herd basis, as significant production and financial risks accompany destocking programs. Eradication will only be more profitable in the longer term, compared with living with the disease, when discounts on the sale of stock from infected herds are high. This can occur with the selling of store cattle or breeders. In stud herds, BJD will usually cause the total failure of the business.     

Prevalence of paratuberculosis (Johne's disease) in the Belgian cattle population

The national bovine paratuberculosis (PTB) seroprevalence (apparent prevalence) in the Belgian cattle population was determined by a serological survey that was conducted from December 1997 to March 1998. In a random sample of herds (N=556, 9.5%), all adult cattle of 24 months of age or older (N=13,317, 0.4%) were tested for the presence of antibodies using a commercially available absorbed ELISA test kit. The PTB median within-herd seroprevalence (proportion of detected animals within the seropositive herds) and the PTB individual-animal seroprevalence (proportion of detected animals) were, respectively, 2.9% (quartiles=1.6-5.6) and 0.87% (95% confidence interval (CI)=0.71-1.03). The PTB herd seroprevalence (proportion of detected herds) was 18% (95% CI=14-21).Assuming a test sensitivity and specificity of 45 and 99% [Sweeney et al., 1995. J. Vet. Diagn. Invest. 7 (4), 488; Sockett et al., 1992. J. Clin. Microbiol. 30 (5), 1134], respectively, the median true within-herd prevalence and the true individual-animal were estimated to be 7 and 2%, respectively. The true herd prevalence of Mycobacterium paratuberculosis infection was first estimated according to currently accepted methodology. This calculation revealed that the specificity of the used test has a dramatic effect on the estimation; assuming a test sensitivity of 45% and a true within-herd prevalence of 7%, the true herd prevalence estimation decreased from 36 to 0.8% if the test specificity decreased from 99. 9 to 99%, respectively. This sensitivity analysis showed that the practical limits of the accuracy of the used screening test jeopardize the estimation of the true herd prevalence within reasonable confidence limits, because the within-herd PTB true prevalence was low.For this reason we augmented the herd specificity for herds with larger adult herd size (>5). This was done by increasing the cut-off number of positive cattle required (>/=2) to classify a herd truly positive and including herds with one positive test result if there was historical evidence of PTB (previous diagnosis and/or clinical signs). This approach resulted in an estimated true herd prevalence of M. paratuberculosis infection of 6%. The true herd prevalence for dairy, mixed and beef herds was, respectively, 10, 11 and 3%.     

The seroprevalence of Johne's disease in Georgia beef and dairy cull cattle.

Beef and dairy cattle serum samples, collected during 2000 at sale barns throughout Georgia, were obtained from the Georgia State Brucellosis Laboratory and were used to conduct a retrospective epidemiological study. Statistical samplings of 5,307 sera, from over 200,000 sera, were tested for antibodies to Mycobacterium avium ssp. paratuberculosis, (Johne's disease) using a commercial enzyme-linked immunosorbent assay test kit. An overall period seroprevalence in all classes of cattle tested was 4.73%. The period seroprevalence in dairy cattle was 9.58%, in beef cattle it was 3.95%, and in cattle of unknown breed it was 4.72%. It was concluded that the seroprevalence of Johne's disease in cull beef and dairy cattle in Georgia is economically significant.     

Johne's disease in sheep

Extract

Inoculation of susceptible laboratory animals with a suspension of kidney tissue is a widely used method of diagnosing leptospirosis in livestock and of isolating leptospiral serotypes. A recent experience has indicated a potential cause of failure which may not be generally realized in laboratories using this technique.     

Prevalence and distribution of paratuberculosis (Johne's disease) in cattle herds in Ireland

A simple random survey was conducted in Ireland during 2005 to estimate the ELISA-prevalence of paratuberculosis, commonly called Johne's disease (JD), in the cattle population. Serum samples were collected from all 20,322 females/breeding bulls over 12 months-of-age in 639 herds. All samples were tested using a commercially available absorbed ELISA. The overall prevalence of infected herds, based on the presence of at least one ELISA-positive animal, was 21.4% (95% CI 18.4%-24.9%). Herd prevalence levels amongst dairy herds (mean 31.5%; 95% CI: 24.6%, 39.3%) was higher than among beef herds (mean 17.9%; 95% CI: 14.6%-21.8%). However, the animal level prevalence was similar. The true prevalence among all animals tested, was calculated to be 2.86% (95%CI: 2.76, 2.97) and for animals >= 2 yrs, it was 3.30% (95%CI: 3.17, 3.43). For animals in beef herds, true prevalence was 3.09% (95%CI: 2.93, 3.24), and for those in dairy herds, 2.74% (95%CI: 2.59, 2.90). The majority of herds had only one ELISA-positive infected animal. Only 6.4% (95% CI 4.7%-8.7%) of all herds had more than one ELISA-positive infected animal; 13.3% (CI 8.7%-19.7%) of dairy herds ranging from two to eight ELISA-positive infected animals; and, 3.9% beef herds (CI 2.4%-6.2%) ranging from two to five ELISA-positive infected animals. The true prevalence of herds infected and shedding Mycobacterium avium subspecies paratuberculosis is estimated to be 9.5% for all herd types; 20.6% for dairy herds; and 7.6% for beef herds. If ELISA positive animals <2-years-of-age are excluded, the true herd prevalene reduces to: 9.3% for all herd types; 19.6% for dairy herds; and 6.3% for beef herds based on a test specificity (Sp) of 99.8% and test sensitivity (Se) (i.e., ability to detect culture-positive, infected animals shedding at any level) of 27.8-28.9%.     

Johne's disease in sheep

SUMMARY Johne's disease was identified in sheep flocks on 6 farms in one area of the central tablelands of New South Wales. The sources of infection were not determined and no common source of all infections was identified. The disease was not diagnosed in cattle that were run on 4 of the farms.     

An estimate of specificity for a Johne's disease absorbed ELISA in northern Australian cattle

OBJECTIVE: To estimate the specificity of an absorbed enzyme-linked immunosorbent assay kit for Johne's disease (JD) when used in mature cattle populations resident in northern Australia. DESIGN: Blood samples were collected from beef cattle in northern Queensland, the Northern Territory and northern Western Australia, and from dairy cattle in northern Queensland. The specificity of a serological test for JD was estimated by testing the blood samples with an absorbed ELISA kit. Further samples were collected from cattle with positive ELISA results to determine the presence or absence of infection with Mycobacterium avium subsp paratuberculosis. PROCEDURE: During 1995 and 1996, blood, tissue and gut contents were collected from beef cattle at abattoirs in Queensland and the Northern Territory; and blood and faecal samples were collected from dairy cattle in herds assessed to be most at risk for JD in northern Queensland. The blood samples were tested using an absorbed ELISA kit. Tissues and gut contents from beef cattle that had positive ELISA results were cultured for M. avium subsp paratuberculosis, and tissues were examined histologically. Faecal samples from dairy cattle with positive ELISA results were cultured for M. avium subsp paratuberculosis. RESULTS: Estimates of specificity for this absorbed ELISA in mature northern Australian cattle were 98.0% (97.0 to 98.8%, 95% CI) in beef cattle, and 98.3% (96.7 to 99.3%, 95% CI) in dairy cattle. CONCLUSION: Estimates of specificity in this study were lower for beef cattle from the Northern Territory and northern Western Australia and for dairy cattle from northern Queensland than those quoted from studies on cattle in southern Western Australia. This should be considered when serological testing using the JD ELISA is carried out on northern Australian cattle.