Paratuberculosis, commonly referred to as Johne’s disease, is a chronic infectious illness that mostly affects ruminant animals, particularly cattle, sheep, and goats. Mycobacterium avium subsp. Paratuberculosis (MAP) is the cause.
Etiology of Johne’s Disease:
Johne’s disease in cattle is primarily caused by a slow-growing bacterium known as Mycobacterium avium subspecies paratuberculosis (MAP). This bacterium primarily targets the lower part of the small intestine, where it leads to chronic inflammation and damages the intestinal tissues.
The infection spreads through the ingestion of food, water, or milk contaminated with MAP. Calves are particularly susceptible, often contracting the disease through the consumption of contaminated colostrum or milk from infected cows. The bacterium has a prolonged incubation period, which can last several years, making it challenging to detect and control.
Host Range:
Numerous ruminant animals, such as cattle, sheep, and goats, are afflicted by Johne’s illness. Other domestic and wild animals are susceptible to infection, albeit usually neither develop a clinical illness.
Johne’s Disease’s Pathogenesis:
The pathogenesis of Johne’s disease in cattle is a multifaceted process that begins with the ingestion of the causative agent, Mycobacterium avium subspecies paratuberculosis (MAP). Once ingested, MAP primarily affects the distal part of the small intestine, particularly the ileum. The bacterium invades the intestinal lining and infects specialized cells known as macrophages. Within macrophages, MAP is able to evade the host’s immune response, eventually forming granulomas, which are collections of infected macrophages, other immune cells, and bacteria. These granulomas can lead to thickening of the intestinal wall and impair nutrient absorption, resulting in chronic diarrhea and weight loss, which are characteristic clinical signs of Johne’s disease. The disease progresses slowly, with a prolonged subclinical phase where animals may shed MAP without showing symptoms.
Transmission of Para-tuberculosis:
Oral-fecal contact is the primary method of transmission for Johne’s illness. The MAP bacteria that infected animals excrete in their feces can contaminate the environment. MAP-contaminated feed, water, or direct contact with contaminated surfaces can cause infection in susceptible animals. It is also possible for infected dams to transmit the disease to their foetuses in pregnancy.
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Clinical Symptoms of Johne’s disease in cattle:
Because of the lengthy incubation period of Johne’s illness, infected animals may not exhibit clinical symptoms for several years after infection.
- Chronic diarrhea
- Weight loss
- decreased appetite
- Decreased milk production Animals have a rough hair coat and look malnourished.
- Animals may experience edema, weakening, and even death in severe phases.
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Diagnosis of Para-T.B:
Johne’s sickness has a gradual course, making it difficult to diagnose, and it is difficult to find MAP bacteria. Typically, it entails a mix of fecal culture, serological testing, and clinical symptoms. While fecal culture is used to isolate and identify the bacteria, serological tests find antibodies against MAP. Detecting MAP DNA in feces can also be done via polymerase chain reaction (PCR) testing.
Post Mortem lesions:
Post-Mortem Lesions: During the post-mortem examination, the intestines can show distinctive lesions. These include inflammation in the ileum and the surrounding lymphoid tissue, thickening of the intestinal wall, and expansion of the lymph nodes. The intestinal lining may be corrugated and ulcerated, and there may be granulomatous lesions.
Treatment of Johne’s disease:
- There is no known treatment for Johne’s sickness.
The bacteria continue to exist in an animal’s intestines after infection. Reducing environmental contamination, eliminating harmed animals to stop the spread of illnesses, and enforcing stringent biosecurity regulations are the main goals of management techniques.
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Prevention and Control for Johne’s disease in cattle:
- There are several different ways to prevent and manage Johne’s illness. This requires stringent herd management procedures include keeping young animals separate from sick adults, avoiding consumption of tainted milk or feces, and maintaining sanitary conditions.
- The disease must be controlled through testing, the killing of afflicted animals, monitoring, and surveillance programs. There are also vaccination programs available in some areas to lower the prevalence of Johne’s illness. For particular advice on preventing, diagnosing, and controlling Johne’s illness, it is crucial to speak with veterinary specialists and local authorities. This is because the strategy may differ depending on the area and the disease’s prevalence.
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