1. Pathogens and Causes
Bovine actinomycosis is mainly caused by the infection of bovine actinomycetes. Staphylococcus aureus and Actinomyces Linnaeus can also cause it. Bovine actinomycetes can be found in contaminated soil, drinking water, and feed, as well as in healthy bovine oral and digestive tract flora. The pathogen has a variety of forms, belonging to Gram-positive bacteria, which can mainly damage the skeleton of dairy cows. In diseased tissues, the fungus is often entangled into mycelial clusters, arranged in a radial pattern around it, like a chrysanthemum.
The mycelium granules are slightly brown or yellow and look like sulfur granules from the outside. The bacterium has a weak resistance. It can be killed in about 5 minutes at 80 C and high temperature. The general disinfectant also has a good disinfection effect. When the oral mucosa of dairy cattle is damaged, it is easy to invade pathogenic bacteria, such as the oral mucosa is stabbed by foreign bodies such as coarse fiber feed, iron wire and wood thorn, which will lead to the infection of bovine actinomycetes in bone and teeth, thus causing the disease.
That is to say, actinomycosis can occur spontaneously when the skin or oral mucosa of dairy cows is damaged. When the pathogen invades and settles in the maxillary and mandibular depth of dairy cows, and causes periostitis and osteomyelitis, it can invade the surrounding tissues of alveolar, and form bacterial aggregates, gradually forming granuloma.
2. Clinical symptoms and pathological changes
The Spotted cow infected with the disease will form rigid vegetation in the lesion area, that is, actinomycete swelling, which is painless and fever-free and will also lead to swelling of the surrounding lymph nodes. When the maxillary bone of dairy cows is infringed, the swelling of the third and fourth molars is usually obvious and can not be moved, which is a slow swelling process, leading to not easy to be found, only when the body has difficulty in chewing; when the soft tissue is infringed by pathogens, it usually occurs in the head, submandibular, neck, and other parts; when the hyoid muscle is invaded by pathogens; When the disease occurs, the tongue tissue will be markedly swollen and hardened, also known as "wooden tongue disease", which causes the symptoms of prolongation and difficulty in chewing.
When the breast is invaded by pathogens, it will lead to the formation of lumps in the breast or the swelling and deformation of the whole breast, and the milk production is more sticky, often mixed with abscess; the lungs are invaded by pathogens. When harmful, it often forms chronic granuloma. If the course of the disease is relatively slow, it will form an incurable fistula in the wound of the skin, discharging milky yellow pus, which contains small yellow-white bacteria, boneless but relatively hard, like sulfur-yellow granules. The granuloma formed is yellow-brown round bulge and mushroom-like. This is the case. When the skeleton of dairy cows is damaged and invaded by pathogens, the skeleton becomes swollen and osteoporosis occurs. By dissecting the dead cattle, we can not only see abscess, induration, and fistula around the lesion but also abscess in larynx, esophagus, reticulum, rumen, and liver.
3. Diagnostic Essentials
The disease can be preliminarily diagnosed according to the epidemic characteristics and clinical symptoms, and laboratory examinations should be carried out if it is confirmed. Generally speaking, actinomycosis has special symptoms and will not be mixed with other diseases, but we should pay attention to the difference between actinomycosis and other local chronic proliferative inflammation.
Press microscopy. A small amount of pus was taken out from the diseased cattle and diluted by adding an appropriate amount of water. Sulfur granules were found and rinsed in water. Then they were placed on the slide, dripped with 15% potassium hydroxide solution 1 drop, covered with a glass slide, pressed hard, and examined under a microscope. Characteristic radial hyphae can confirm the occurrence of the disease.
Paraffin section microscopy. The pathological tissues of diseased cattle were taken for a series of treatments, and then paraffin sections were made. After hematoxylin-eosin staining, the structure of actinomycete granuloma and the morphology of actinomycete colonies could be seen by microscopic examination. Microscopic examination showed that the fungus was rose or chrysanthemum, and the mycelium in the center was filamentous and globular. Gram staining showed positive results. Radial sticks around the fungus were negative, and hematoxylin-eosin staining showed strong eosinophilic.
Surgical resection. If the diseased cattle form a larger induration, they can be removed surgically. If a fistula is formed, the fistula should also be completely removed. The head of the diseased cattle is fixed, the hair is cut off and routinely disinfected. The skin of the lesion was incised with a sterilized surgical knife for purulent discharge, and the wound cavity was cleaned with hydrogen peroxide and saline. The newly created cavity formed after resection can be filled with gauze impregnated with iodine tincture and replaced once 24-48 hours apart.
It can inhibit the activity of actinomycetes mainly through iodine preparations, at the same time, it can corrode the infected parts of bacteria, and make local wounds fester and burst as soon as possible, to avoid the spread of infectious bacteria in a large area. Also, according to the size of the wound cavity in the affected area, the appropriate length gauze can be selected, folded after unfolding, and a thin layer of potassium permanganate powder can be sprayed on the lower layer, and drained after covered by the upper gauze.
Because potassium permanganate is very corrosive, it is necessary to control the dosage of potassium permanganate. Otherwise, the wound cavity will be corroded excessively and the healing will be hindered. Meanwhile, 2% Ruggo's solution or 10% iodoform ether was injected around the wound cavity.
Use potassium iodide. Adult dairy cows were treated with 5-10 G potassium iodide daily and cow babies with 2-4 G potassium iodide for 2-4 weeks. If the symptoms of diseased cattle are serious, 50-100 mL 10% potassium iodide can be injected intravenously every day, once every day, 3-5 times continuously. In the course of treatment with potassium iodide, if the diseased cattle suffer from iodine poisoning such as skin eruption, hair loss, emaciation, tears and redness of mucosa, the dosage of iodine should be stopped for 5 to 6 days or reduced. Two 1.6 million IU penicillin and 2 mL procaine was injected at 4 o'clock around the tumescent lesions for local closure twice a day for 2 weeks.
Antibiotic therapy. Antibiotics were injected around the affected female cows once a day for 5 days. Besides, antibiotics and potassium iodide can be used simultaneously to treat soft tissue infections and hyoglossus, and aureomycin can also be used.