Johne’s disease (pronounced “yo-knees”) is an infection of the small intestine that affects cattle, sheep, goats, and other ruminants (hoofed animals). It’s caused by a resistant species of bacteria (mycobacterium avium subspecies paratuberculosis) that belongs to the same family as tuberculosis and leprosy.
Johne’s disease is endemic worldwide, including in the United States. The disease is contagious. It typically causes a chronic form of inflammatory bowel disease (granulomatous enteritis) that leads to progressive weight loss, debilitation, and eventually death. Economic losses in infected herds include reduced milk production, early culling, and poor condition at culling.
Signs of Johne’s disease rarely show up until years after the initial infection, which usually occurs shortly after birth. Over time, the intestines become thick and less efficient at absorbing nutrients.
When symptoms are finally noticeable, here’s what you may see:
- Diarrhea and weight loss, despite a normal appetite
- Some infected animals appear malnourished and weak; others have chronic diarrhea.
- It often starts within a few weeks after a stressful event, like calving.
- Soft swelling under the jaw (known as “bottle jaw”) in cattles
- This may occur several weeks after the onset of diarrhea due to protein loss from the bloodstream into the digestive tract.
- Animals at this stage of the disease will not live very long, perhaps a few weeks at most.
- Declining or reduced herd production, especially in 3- to 6-year-old cows
Paratuberculosis, caused by Mycobacterium avium paratuberculosis , is a chronic, contagious granulomatous enteritis characterized in cattle and other ruminants by progressive weight loss, debilitation, and eventually death. Diagnosis is primarily made by PCR. There is no satisfactory treatment. Control requires good sanitation and management to avoid exposure among young animals.
Paratuberculosis is a listed disease by the OIE, meaning it is a priority disease for international trade. The infection has also been recognized in captive and free-ranging wild ruminants as well as omnivores and carnivores such as wild rabbits, foxes, weasels, pigs, and nonhuman primates. Distribution is worldwide. Many countries have national control programs. The highest published prevalence is in dairy cattle, with 20%–90% of herds infected in most major dairy-producing countries. The disease is of economic importance for the goat industry in Spain and the sheep industry in Australia.
Etiology and Pathogenesis of Paratuberculosis in Ruminants
Mycobacterium avium subspecies paratuberculosis (MAP) is excreted in large numbers in feces of infected animals and in lower numbers in their colostrum and milk. It is resistant to environmental factors and can survive on pasture for >1 year; survival in water is longer than in soil. The infection is usually acquired through the fecal-oral route; the dose needed to infect an animal is not known. Herds or flocks become MAP-infected by introduction of subclinically infected carriers.
Infection is acquired early in life—often soon after birth—but clinical signs rarely develop until after animals are sexually mature. Progression to clinical disease occurs slowly. Resistance to infection increases with age but is never complete. Infection is acquired by ingestion of the organism when nursing on contaminated teats; consumption of milk, solid feed, or water contaminated by MAP; or licking and grooming behavior in a contaminated environment. In the later, bacteremic stages of infection, intrauterine infections are seen.
After ingestion and uptake in the Peyer’s patches of the lower small intestine, this intracellular pathogen infects macrophages in the GI tract and associated lymph nodes. It is possible that some animals may eliminate infection through a cell-mediated immune response, but the frequency with which this occurs is unknown. In most cases, the organisms multiply and eventually provoke a chronic granulomatous enteritis that interferes with nutrient uptake, leading to the cachexia typical of advanced infections. This may take months to years to develop and is usually paralleled by a decline in cell-mediated immunity, a rise in serum antibody, and bacteremia with dissemination of the infection beyond the GI tract. Fecal shedding begins before clinical signs are apparent, and animals in this “silent” stage of infection are important sources of transmission.
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Clinical Findings of Paratuberculosis in Ruminants
Paratuberculosis in cattle is characterized by weight loss and diarrhea in the late phases of infection, but infected animals can appear healthy for months to years. In cattle, diarrhea may be constant or intermittent; in sheep, goats, and other ruminants, diarrhea may not be seen. It typically does not contain blood, mucus, or epithelial debris and is passed without tenesmus.
Pipe line diarrhea commonly seen in this disease
Throughout weeks or months, the diarrhea becomes more severe, further weight loss occurs, coat color may fade, and ventral and submandibular edema may develop due to a protein-losing enteropathy. This leads to low concentrations of total protein and albumin in plasma, although gamma globulin levels are normal.
Intestine, cow
Lesions
Ileum, cow
In dairy cattle and goats, milk yield may drop or fail to reach expected levels. Animals are alert, and temperature and appetite are usually normal, although thirst may be increased. The disease is progressive and ultimately terminates in emaciation and death. As the within-herd MAP infection prevalence rises, so too does the herd cull rate, while dairy herd milk production declines. The disease in sheep and goats is similar, but diarrhea is not a common feature, and advanced cases may shed wool easily. In cervids (deer and elk), the course of the disease may be more rapid.
Diagnosis of Paratuberculosis in Ruminants
- PCR is the primary method currently used
There are many commercially available tests for paratuberculosis, each with their own advantages, disadvantages, and appropriate application. The assays focus on detecting the organism in feces or tissue (culture, PCR), or on detecting antibody to MAP antigens (ELISA). Use of different tests in combination can increase diagnostic sensitivity. Given the biology of the infection and the need to manage it on a herd basis, herd-based testing is as, if not more, important than testing of individual animals.
PCR is more sensitive and more specific than serology. PCR has replaced culture for MAP detection because the organism grows very slowly (2–4 months) and culture is more costly. Pooling of fecal samples (eg, five samples per pool) or manure from farm sites where cattle commingle (environmental sampling) can establish a herd’s infection status at a lower cost, despite some reduction in test sensitivity. Use of a laboratory that has passed a proficiency test for the specific assay being used is recommended. Most strains infecting sheep will not grow on solid media but may be isolated using liquid culture media systems. Commercial PCR kits are as sensitive and specific as fecal culture and much more rapid and less expensive.
Tests of cell-mediated immunity, such as the intradermal Johnin test, lymphocyte transformation test, and interferon-gamma, are used more on a research basis. The genome of MAP has been described and may provide the basis for new diagnostic approaches.
Control of Paratuberculosis in Ruminants
- Prevent exposure of young animals to MAP
- Identify and cull or segregate infectious adult animals
No satisfactory treatment is known.
no treatment as such because it is viral disease….just use antibiotics
Control requires good sanitation and management practices aimed at limiting the exposure of young animals to the organism. Calves, kids, or lambs should be birthed in areas free of manure, removed from the dam immediately after birth in the case of dairy cattle, bottle-fed colostrum that has been pasteurized or obtained from dams that test negative, and then reared segregated as much as possible from adults and their manure until >1 year old. Use of milk replacer is recommended instead of waste milk unless the waste milk has been pasteurized.
A routine testing program for adults can help focus efforts in controlling the disease. Low-cost tests (eg, ELISA) have the greatest cost benefit for commercial dairy herds that are confirmed infected by culture or PCR. Animals testing positive, particularly heavy shedders or those that have strong-positive ELISA results, should be sent to slaughter as soon as economically feasible.
Herd replacements should be obtained from herds believed to be free of the disease, and the replacements themselves should be tested before introduction to the new herd. More general procedures to minimize fecal contamination on the farm can also help, eg, elevating food and water troughs, providing piped water in preference to ponds, and harrowing frequently to disperse feces on pasture. Herd owners should be advised that paratuberculosis control takes at least 5 years.
Zoonotic Risk of Paratuberculosis in Ruminants
There are conflicting data on the involvement of the causative organism in Crohn disease, a chronic granulomatous enteritis of unknown cause in people. However, MAP is consistently detected by PCR in people with Crohn disease. This fact, coupled with its broad host range, including nonhuman primates, indicates that paratuberculosis should be considered a zoonotic risk until the situation is clarified.
FAQ,s about jhone’s disease
What is Johne’s disease and which animals are affected?
Johne’s disease is a chronic, contagious bacterial infection that affects the intestines of ruminants like cattle, sheep, and goats. It’s caused by Mycobacterium avium subspecies paratuberculosis (MAP).
How do animals get infected with Johne’s disease?
Infection usually occurs early in life through contaminated milk, water, or manure, but signs may not appear until years later. The bacteria damage the intestines, leading to weight loss and diarrhea.
Can Johne’s disease be cured or treated?
There is no effective cure for Johne’s disease becuase it is viral disaese. Management focuses on prevention, testing, culling infected animals, and improving hygiene to limit the spread.
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