Diagnosis and Control of Johnes Disease
This eventually leads to severe loss of condition. An infected sheep can waste away and die. Sheep infected with OJD excrete the bacteria in their manure, contaminating pasture and water supplies and spreading infection to other susceptible sheep. View the final report from the consultation here.
Prevention and Control of Johne's Disease - Beef Cattle Research Council
OJD is often not diagnosed in a flock until a significant proportion of the flock is already infected and deaths are occurring. Infected sheep can be shedding the bacteria in their manure for a considerable period sometimes years even though the flock still looks healthy, but they are contaminating the pasture and infecting other sheep. OJD-infected sheep continue to eat and drink normally until they are too weak to graze, and eventually die.
In some large flocks, the number of deaths may only be appreciated when big discrepancies occur in counts of adult sheep. When obvious OJD deaths are noticed, the disease is likely to be well established. It will take the producer some years to get the situation under control, during which time deaths will continue.
The best place to look for the disease is in 2 and 3-year olds, but sheep from weaners through to older adults can also die from the disease. JD is caused by M. It causes the intestinal wall to thicken and reduces the normal absorption of nutrients from grazing. An infected animal can eventually starve to death. Many wildlife, including rabbits, and exotic species are also susceptible to Johne's disease.
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There is evidence for intrauterine infection of the developing calf in the case of heavily-infected dams Fig 3. There is a long incubation period and clinical disease is not usually apparent until three to five years-old although younger cases are possible. Infected animals may shed organisms in the faeces for over a year before clinical signs appear.
Farmers should look for diarrhoea, poor milk yield and weight loss in cattle three to five years-old with onset often following calving or other stressful event sale, transportation etc. There is no fever and the animal maintains a good appetite until the terminal stages. There is no single reliable test for confirming Johne's disease during the early stages of disease tests described as having a low sensitivity.
Johne’s disease in Australia
Blood tests detect antibodies to crude M. In practical terms diagnosis is best done using a combination of serology blood tests and faecal examination for the causative organism. Control is difficult because of the long incubation period, shedding of infection by animals before they show clinical signs, and diagnostic techniques with poor detection rates in the early stages of disease.
Eradication requires a substantial commitment by the farmer, veterinarian and local laboratory and is based upon the identification and removal of infected animals. Two consecutive herd negatives may indicate eradication. Practical control measures that can readily be adopted to limit losses in a diseased herd include:.
Rearing home-bred heifers rather than buying in breeding replacements may serve to reduce the risk of introducing disease but if Johne's disease is present in the herd it will increase disease prevalence. The pooling of samples will be done in the lab and the individual samples will be catalogued and frozen in an Ultra-Low freezer for PCR if part of a positive pool.
You will not have to re-submit samples. Individual samples from positive pools will be automatically set for PCR and appropriate charges for the individual PCRs applied to the accession. Consequently, results on positive pool samples may take days and this must be considered for timing of testing for optimal use of results. Clinical suspects or high risk samples should not be tested in pools. Paratuberculosis MAP in bovine serum. Potentially, the ELISA could also be used as an adjunct in herds where the goal is complete eradication, and the removal of infected non-shedders is desired.
Since the concern of most farms is the detection of cattle that are shedding MAP, and therefore infectious, it is recommended that this serology test be used in conjunction with antigen detection tests on feces such as direct PCR prior to culling animals. Results are reported as positive or negative, based on lines of precipitin forming in an agar matrix between antigen and serum sample wells. The AGID may therefore be useful in some control efforts, especially for small ruminants and cervidae, especially where culture or PCR assays are either not available or beyond the economic resources for the herd.
Currently reagents are not available for sheep AGID testing.
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See comments for individual animal testing. Phone: Fax: Email: diagcenter cornell. Labeling the tube with the animal ID is also very helpful in keeping samples properly identified. On the accession form, please specify the exact name of the testing option from the table above, as more than one test can be performed on a single sample type.
Use same animal ID from test to test to track progress of animals over time. For forms and information, call Monica at For sample containers and mailers, contact shipping at or see the supplies page. We recommend use of the plastic screw-cap fecal container available for fecal samples from our shipping department. Containers must be clean. Containers should be wide mouthed, unbreakable, sterile screw-cap plastic jars that can withstand internal pressures associated with shipping and bacterial fermentation.
Recommended fecal containers may be purchased from the laboratory supplies page ; ; ahdlshipping cornell. Please submit 2 mls of serum. Follow ALL submission criteria for fecal samples as stated above. Rationale for Selection of Tests for Cattle The recommended test or test combinations depend upon the specific farm situation.
Prevention and Control of Johne's Disease
Selection of Tests for Bovine Herd Testing Testing is most useful at the herd—and not the individual animal—level. May be useful in herds where the goal is complete eradication and removal of infected non-shedders is desired. Testing of Individual Cattle As described above, no single test will detect all infections because animals respond differently at different stages of infection. High sensitivity, rapid turnaround, and reasonable fees make the direct fecal PCR the test of choice for clinical suspects. Since this test becomes positive later in the course of infection, it will miss early infections.
So serum testing in a subset of clinical animals will yield a false negative result. Feces or colon contents can be tested by direct fecal PCR to confirm the diagnosis. Also tissues from the distal ileum, ileocecal junction and associated lymph nodes, and mesenteric lymph nodes can be cultured to confirm the diagnosis. Export and Regulatory Testing It is important to determine which test will be accepted by the buyer or governmental oversight agency in order to satisfy animal movement testing needs.
Rationale for Selection of Tests for Goats The recommended test or test combinations depend upon the specific farm situation, including farm economics and goals. Selection of Tests for Goat Herd Testing Testing is most useful at the herd—and not the individual animal—level. This combination of tests may be necessary to employ in herds in which kids are managed by allowing suckling on their dams until weaning, especially herds of genetically valuable seed stock, in order to reduce the risk of undetected shedding to the absolute minimum possible when young animals are comingled with adults, especially prior to weaning.
Selection of Tests for Ruminants other than Cattle or Goats Testing is most useful at the herd —and not the individual animal —level. Note: the ELISA will not be performed on samples from camelida cervids, or exotic bovidae May be useful in herds and valuable animal collections such as zoos where the goal is complete eradication and removal of infected non-shedders is desired. This combination of tests may be necessary to employ in herds in which young stock are managed by allowing suckling on their dams until weaning, , in order to reduce the risk of undetected shedding to the absolute minimum possible when young animals are comingled with adults, especially prior to weaning.
Since the PCR assay is not fully validated in non-bovine, non-caprine species, the culture should be employed as the gold standard test methodology. However, the longer lag time to get back a culture favors the use of PCR testing to supplement culture when more rapid detection, especially of clinical suspects, is desired. Histopathology with acid-fast staining of tissues from the distal ileum, the ileocecal junction, and the mesenteric lymph nodes and culture of these tissues are also considered diagnostic. If definitive confirmation is important, culture of unfixed post-mortem tissues, especially ileocecal junction and regional mesenteric lymph nodes collected close to the ileocecal junction, are considered the gold standard for diagnosis of MAP infection.
Samples should include composites representing the entire adult herd including dry cows. Samples from common cow alleys including dry cows should represent a commingled sample of all adult cows in the herd on the day of sampling. Sampling large manure storage areas such as lagoons can be complicated because storage samples may represent a commingled sample manure and sometimes milk house waste collected over a longer period of time with dilution effects and declining MAP survival over time.
When possible, sampling from or near common entry pipes delivering fresh manure to the lagoon or tank from the adult barns without milk house waste can reduce some of the dilution and survival issues.