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Lost in the Gut: Why is Johne's Disease in Cattle So Hard to Detect?
Johne's Disease, formally known as intestinal tuberculosis, is a contagious, chronic, and sometimes fatal infection caused by the bacterium Mycobacterium avium subspecies paratuberculosis that primarily affects the small intestine of ruminants. . The disease is difficult to diagnose and can even lead to the death of animals in severe cases, but it is often overlooked during veterinary examinations, raising questions about whether it is an important factor affecting cattle health.
Enteroscopic TB usually begins to show itself in cattle between four and seven years of age and is often diagnosed in a single animal.
Etiology
The causative agent of Johne's disease is Mycobacterium leprae, an acid-reactive bacillus abbreviated as MAP. The bacterium is related to Mycobacterium tuberculosis, the bacterium that causes human tuberculosis, but has significant differences in growth rate and ecological distribution. MAP grows more slowly, requires additional iron transport compounds to facilitate its growth in the laboratory, and generally reproduces efficiently when infecting ruminants.
Symptoms and Pathophysiology
When cattle are infected with Johne's disease, the main symptoms observed include diarrhoea and weight loss. Initial symptoms are usually subtle and may be limited to weight loss, decreased milk supply, and coarse coat. As the disease worsens, animals develop what is known as “bottleneck jaw edema,” a clinical manifestation caused by protein loss.
The diarrhea is usually free of blood, mucus, or epithelial residues and may be intermittent.
Difficulties in diagnosis
Diagnosing Johne's disease is challenging because initial infection is asymptomatic and most warning signs may not appear until years after infection. Even when these changes are witnessed, delays in diagnosis can result in significant losses in productivity on farms.
Detection and prevention measures
Due to the insidious nature of Johne's disease, regular testing is essential to detect the disease early. Many farmers should perform testing once or twice a year to keep their herd healthy. If infected individuals are found, according to U.S. federal regulations, these individuals cannot be moved at will after diagnosis unless they are used for slaughter.
Diagnosing this pathogen is challenging because initial infection does not cause obvious symptoms.
Human risks
Although Johne’s disease primarily affects ruminants, new research suggests that Mycobacterium leprae may be associated with certain diseases in humans, particularly Crohn’s disease. Although there is no clear evidence that Johne's disease is contagious, the human health problems it may cause cannot be underestimated. ConclusionJohnson's disease in cattle is a common disease worldwide; however, its long incubation period and diverse clinical manifestations make it extremely difficult to diagnose. It is critical for farm operators and animal health professionals to understand how Johne's disease is transmitted and its potential impact on cattle health. In the face of such an insidious and dangerous disease, what actions should we take to ensure the health of animals and humans?
