Johnes disease

Johne's Disease (pronounced "Yo-nees"), also known as Paratuberculosis, is a contagious, chronic, and sometimes fatal infection that primarily affects the small intestine of ruminants. It is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). This disease is of significant concern in the livestock industry due to its impact on animal health, productivity, and welfare.

Etiology

Johne's Disease is caused by Mycobacterium avium subspecies paratuberculosis (MAP), a hardy bacterium that can survive in extreme conditions for extended periods. It is closely related to the bacteria that cause tuberculosis and leprosy in humans, though the risk of cross-species infection is considered low.

Transmission

The primary route of transmission is fecal-oral. Young animals are most susceptible, often becoming infected by ingesting contaminated feed, water, or milk from infected mothers. The bacteria can also be transmitted through the placenta to the fetus in some cases. Once established, the bacteria multiply in the intestine, leading to the disease's characteristic symptoms.

Symptoms and Diagnosis

Symptoms of Johne's Disease include persistent diarrhea, weight loss despite a good appetite, and reduced milk production in dairy animals. Due to its slow progression, symptoms may not appear until years after the initial infection, complicating early diagnosis and control.

Diagnosis is challenging due to the disease's slow progression and the variability of symptoms. Common diagnostic methods include culture of fecal samples, PCR (Polymerase Chain Reaction), and serological tests for antibodies against MAP.

Prevention and Control

Prevention and control strategies for Johne's Disease focus on interrupting its transmission cycle. Measures include testing and culling infected animals, improving sanitation to reduce fecal contamination of feed and water, and managing calving to prevent infection of newborns. Vaccination is available in some countries but is not universally adopted due to concerns about vaccine efficacy and interference with tests for bovine tuberculosis.

Economic and Public Health Impact

Johne's Disease poses a significant economic burden on the livestock industry due to reduced productivity, increased management costs, and trade restrictions. While the risk of MAP infecting humans and causing disease is still under investigation, its potential link to Crohn's Disease in humans has generated public health interest.

See Also

• Mycobacterium avium subspecies paratuberculosis
• Ruminants
• Zoonotic diseases

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