Prevent the Spread of Tuberculosis and Malignant Catarrhal Fever in Your Cattle Herd

Tuberculosis in Cattle

Bovine Tuberculosis is a contagious disease that affects cattle and is caused by the bacterium Mycobacterium bovis. This bacterium can also infect and cause disease in various other mammals, such as humans, goats, pigs, cats, and dogs. Although Bovine Tuberculosis is primarily a respiratory disease in cattle, clinical symptoms are infrequent.

Tuberculosis is an infectious disease that is characterized by the gradual formation of tubercles in almost any organ of the body, except for the skeletal muscles. This disease is a zoonosis, which can be transmitted between animals and humans, and is of significant economic importance in some countries for cattle, pigs, and poultry.

Causes of Tuberculosis in Cattle

Tuberculosis is a disease caused by a bacterium called Mycobacterium bovis (M. bovis) which primarily affects cattle. However, this bacterium is also capable of infecting and causing disease in various other mammals such as humans, deer, goats, pigs, dogs, cats, poultry, and badgers.

Mycobacterium bovis, which is a slender rod-shaped microorganism, possesses the unique characteristic of being acid-fast due to the presence of a waxy layer that prevents the absorption of commonly used staining dyes. It also exhibits resistance to external factors such as exudates and fecal materials. Nonetheless, high temperatures and disinfectants at higher concentrations are effective in killing this bacterium.

As for Mycobacterium tuberculosis, it causes tuberculosis in humans. Mycobacterium avium, on the other hand, is responsible for avian tuberculosis in poultry.

Transmission of Tuberculosis in Cattle

The primary route of transmission for this disease is through the exchange of respiratory secretions between infected and uninfected animals. This can occur through nose-to-nose contact or by inhaling aerosol droplets that have been exhaled by an infected animal.

The disease can also be transmitted directly from one animal to another through the inhalation of infected droplets, ingestion of infected discharges, and open lesions in lymph nodes. It can also be transmitted through feces, milk, and urine. Droplet inhalation is more likely when cattle are housed in close proximity with poor ventilation, while infection through skin abrasions is less likely.

Animals may retain microorganisms for many years in encapsulated lesions in their lungs, which can break down and release the microorganisms. Drinking milk from infected udders (in calves and pigs) is a common way the disease spreads. Acid-fast bacteria are bacteria that resist decolorization by strong acid solutions, and they include tubercle bacillus, leprosy bacillus, Johne's bacillus, and others.

There are different staining methods used to identify the disease, such as Gram stain (for bacteria and protozoa), acid-fast stain (Ziehl-Neelsen), and Loeffler's alkaline methylene blue stain.

Clinical Signs of Tuberculosis in Cattle

Bovine TB is a disease that is challenging to diagnose based on clinical signs alone. During the early stages of TB, clinical signs may not be apparent. However, as the disease progresses, clinical signs such as emaciation, lethargy, weakness, anorexia, low-grade fever, and pneumonia with a chronic, moist cough may be observed. In addition, lymph nodes may become enlarged.

The signs exhibited by an infected animal will depend on which organ is affected. For instance, progressive emaciation and a variable appetite are frequently observed, particularly in cases where the disease has been present for several months. Furthermore, any stress, such as calving, may trigger a particular syndrome.

The Pulmonary Form/Syndrome of Tuberculosis

Pulmonary tuberculosis (PTB) is an infectious disease caused by Mycobacterium tuberculosis, which can infect not only the lungs but also other organs such as the brain, kidneys, and lymph nodes.

The most common signs of PTB include a low, moist cough at irregular intervals, which can be initiated by exercise, increased respiratory rate and depth, dull sounds on auscultation, respiratory distress associated with lymph node enlargement pressing on air passages, coughing with yellow discharge, and involvement of mediastinal lymph node enlargement pressure and occlusion of the esophagus. This can lead to suppression of eructation and gas retention in chronic or marked tympany.

Intestinal involvement can also occur, presenting as chronic diarrhea and lymph node enlargement causing pressure on adjacent organs. It is important to note that milk from infected udders is a common cause of tuberculosis in humans, leading to enlargement and induration of the udder, commonly affecting the rear 1 out of the tits. Supramammary lymph node enlargement can occur, and milk may flocculate on standing.

In addition, tuberculosis can also cause reproductive syndromes, such as abortion in late pregnancy or generalized tuberculosis in full-term calves. Conception failures and thick, purulent, yellow-colored discharge from the vagina may also occur.

Postmortem Finding of Tuberculosis in Cattle

associated with the lungs. The lesion consists of a caseous core surrounded by fibrous tissue. Over time, old lesions tend to merge, resulting in an uneven shape and the enclosed material may calcify. A thicker fibrous tissue capsule also develops around the lesion.

When there are numerous small lesions present, it is known as military tuberculosis. It is advisable to take smears from the inner layer of the fibrous tissue capsule for diagnosis.

Differential Diagnosis of Tuberculosis in Cattle

Differential diagnosis of Tuberculosis in cattle includes distinguishing it from other forms of mastitis such as tuberculous mastitis, which presents with induration and painless enlargement at the base of the quarter rather than near the teat.

It also involves distinguishing tuberculosis metritis from other forms of metritis which can be identified by the discharge of yellow-colored pus and lymphadenopathy. Additionally, in Actinobacillosis, the infection only affects those of the head.

Treatment of Tuberculosis in Cattle

The recommended treatment for tuberculosis in cattle involves the use of isoniazid and rifampicin for a period of six months, with pyrazinamide and ethambutol administered during the first two months of this treatment period.

While isoniazid is commonly used to treat tuberculosis in humans, it is generally not recommended for use in animals due to the high cost of prolonged treatment, unreliable results, and the potential for animals under treatment to spread tuberculous microorganisms in milk. Instead, the preferred approach is to use a tuberculin test to identify infected animals, which can then be eliminated to prevent the spread of the disease.

Control of Tuberculosis in Cattle

To control tuberculosis in cattle, there are several methods that can be employed. First, it is recommended to purchase animals only from accredited tuberculosis-free herds. Before purchasing new animals, it is important to test them and isolate them for 60 days. After this period, they should be retested before being introduced to the herd. It is also important to restrict or eliminate contact between your herd and other herds.

Methods for controlling tuberculosis in cattle are effective when done on a country or wide area basis. One such method involves examining all cattle in the area and slaughtering clinical cases. Additionally, all cattle should be tested and reactors separated from the others.

Vaccination is another method that can be used. An attenuated strain of Mycobacterium bovis, known as Bacille Calmette-Guérin, can be used. However, the immunity produced by this method is short-lived (about one year), and its use interferes with the tuberculin test. Therefore, these two methods cannot be used simultaneously.

The tuberculin test involves injecting a small quantity (0.1 ml) of a culture of tubercle bacilli intradermally into an animal. Diseased animals will react 72 hours later by showing swelling at the site of injection.

Bovine Malignant Catarrhal - (BMC) (Malignant Catarrhal Fever)

Bovine malignant catarrhal fever is a highly fatal viral disease that affects cattle, but it does not seem to spread directly from one cattle to another. The disease is marked by acute inflammation of the mucous membranes, especially those of the respiratory system. Although some animals may recover from mild infections, the disease can be deadly in most cases.

In terms of prevalence, Bovine malignant catarrhal fever is sporadic in nature, but outbreaks have been reported, leading to the involvement of a large number of animals.

Causes of Bovine Malignant Catarrhal Fever

The causes of Bovine Malignant Catarrhal Fever are as follows: the herpes virus, which can be easily destroyed through exposure to heat, disinfectants, and freezing. Additionally, the virus can only survive for a short period outside of the animal body. This disease is common in cases where sheep and cattle are housed together and typically affects animals that are under 13 months old.                                                        

Transmission of Bovine Malignant Catarrhal Fever

Bovine malignant catarrhal is caused by a virus transmitted from pregnant or recently lambed sheep or goats to cattle although months may elapse between the time of contact and the time of appearance of clinical signs of the disease and the actual method of transmission to cattle is unknown.

Clinical Signs of Bovine Malignant Catarrhal Fever

The symptoms of this disease typically include fever, depression, discharge from the eyes and nose, lesions in the buccal cavity and muzzle, swelling of the lymph nodes, the opacity of the corneas leading to blindness, inappetence, and diarrhea. Some animals may also exhibit neurologic signs such as ataxia, nystagmus, and head pressing.

Bovine malignant catarrhal fever is caused by a virus that attacks the blood vessels in multiple organs, resulting in a wide range of clinical signs. These signs can vary greatly and may include an incubation period of 2-8 weeks or longer, high fever, rapid pulse, enlargement of superficial lymph nodes, and swelling of joints.

In the head and eye form of the disease, there is congestion of the buccal and nasal mucosae, mucopurulent discharge from the nose, sloughing of the skin on the muzzle, profuse lacrimation leading to edema and opacity of the cornea, and ulceration.

Other signs of the disease may include diarrhea, which may be bloody, sudden death, depuration (the animal separating itself from the rest of the herd with its head down), cloudy or ulcerated eyes, and salivating.

Clear watery mucus dripping from the nose and swollen joints may be seen 10-12 days prior to the onset of symptoms, along with difficulty in urinating and frequent urination with pain or bloody urine.

How To Treat Bovine Malignant Catarrhal Fever

There is no specific treatment for Bovine malignant catarrhal but antibiotics are given to counteract secondary bacterial infections. Affected cattle must be euthanased immediately for welfare reasons.

There are not currently any vaccines for malignant catarrhal fever. Control relies on avoiding contact with sheep but such management is not always possible on most mixed-stock farms.

Control And Prevention of Bovine Malignant Catarrhal Fever

Malignant catarrhal fever is usually prevented by separating susceptible animals from sheep, goats, wildebeest, or other reservoir hosts. The degree of susceptibility can influence separation requirements.

No satisfactory vaccine has been produced yet for Bovine malignant catarrhal, separation of sheep and cattle has been an effective control measure, and recovered cattle develop solid immunity which may last 2-3 years.

Conclusion

In conclusion, tuberculosis and bovine malignant catarrhal fever are two distinct diseases that can affect cattle. Tuberculosis, caused by Mycobacterium bovis, is a contagious disease that primarily affects the respiratory system of cattle but can also impact other organs. It is a zoonotic disease, meaning it can be transmitted between animals and humans. Clinical signs of tuberculosis may include emaciation, lethargy, anorexia, low-grade fever, and pneumonia.

On the other hand, bovine malignant catarrhal fever is a viral disease caused by the herpes virus. It is characterized by acute inflammation of the mucous membranes, particularly those of the respiratory system. Clinical signs of bovine malignant catarrhal fever include fever, depression, nasal and ocular discharge, lymph node swelling, and neurologic symptoms.

To control tuberculosis in cattle, measures such as purchasing animals from accredited tuberculosis-free herds, testing and isolating new animals, and restricting contact between herds can be implemented. Vaccination with Bacille Calmette-Guérin (BCG) is an option, but it interferes with the tuberculin test. Diagnosis of tuberculosis involves tuberculin testing and postmortem examination of lesions.

Preventing bovine malignant catarrhal fever requires separating susceptible cattle from sheep or other reservoir hosts. There is no specific treatment for the disease, and affected animals may need to be euthanized. Antibiotics can be used to address secondary bacterial infections.

Overall, proper management practices, including regular testing, isolation of new animals, and biosecurity measures, play a crucial role in controlling and preventing these diseases in cattle. It is essential for farmers and livestock owners to work closely with veterinarians and follow recommended protocols to minimize the impact of these diseases on animal health and production.