Prevention and treatment of tuberculosis in chickens

Chicken tuberculosis is a chronic contagious disease caused by Mycobacterium fowl. The disease is characterized by chronic progression, progressive weight loss, anemia, reduced egg production or no egg production. During the autopsy, tuberculosis nodules were observed in various tissues and organs, especially in the liver, spleen and intestinal tract. In the outbreak of poultry farms, most of them are chronic, growth and development and production performance are affected, egg production decline and death, resulting in serious economic losses. However, due to different feeding methods, mainly short feeding days, broiler chickens and stuffed ducks were slaughtered quickly and rarely found; although breeding birds were raised for a long time, the pollution area was small and the incidence rate was low.

Pathogenic pathogen

The pathogen of this disease is Mycobacterium tuberculosis, which is a kind of Mycobacterium, which is characterized by short and polymorphic bacteria. The bacteria is slender, upright or slightly curved, sometimes in the shape of rod, cocci or chain ball, etc. The two ends of the cell are obtusely round, 1.0 ~ 4.0 μ m long and 0.2 ~ 0.6 μ m wide. This bacteria has no spores, no capsule, no flagella, and can not move; this bacteria is not easy to stain with general aniline dyes, Gram-positive and acid-resistant. Mycobacterium tuberculosis is red when stained with Nissl's staining method, while some other non-mycobacteria are stained blue. This staining characteristic can be used for the diagnosis of this disease.

This strain is a specific aerobic bacteria and has strict nutritional requirements. It can only grow in a special medium containing serum, milk, yolk, potato, glycerin and some inorganic salts. The optimum growth temperature is 3940 ℃ and the optimum culture medium is pH6.5~6.8.

When isolating Mycobacterium tuberculosis for the first time from the materials of natural cases, a special culture medium should be selected. 2% glycerol was added to the culture medium and cultured in 5%-10% carbon dioxide environment to promote its growth. The growth of Mycobacterium tuberculosis is slow, and after about 10 to 21 days of isolation, round, raised, smooth and glossy colonies can be seen, from light yellow to yellow, and turn to bright yellow with time; some strains grow smooth, flat, translucent gray-white colonies in some culture media. In the liquid medium such as glycerol broth, the culture with particle precipitation and viscous bacterial membrane was grown.

In the biochemical test of Mycobacterium tuberculosis, nitrate reduction, urease, hydrolysis of Tween 80 and nicotinic acid formation were all negative; glycerol could promote growth, reduce tellurite and contact enzyme test was positive. These biochemical characteristics are of differential significance.

The surface of Mycobacterium tuberculosis contains a large amount of lipids and waxes, which has strong resistance to the external environment, especially to drying. The bacteria in the secretion can survive for 6-8 months in dry environment and 18-31 days in sunlight, live in feces and water for 5 months, live in soil for 2 years or more, decrease in direct sunlight for 1 h, and all die in 4 h. Mycobacterium tuberculosis has weak resistance to damp and heat, loss of vitality at 60 ℃ 30min, strong resistance to low temperature, and 4 to 5 months below 0 ℃.

Bacteria are also resistant to chemicals and sensitive to fat-dissolving ion cleaners; 2% Lysol, 5% carbolic acid, 3% formaldehyde, 10% bleach, 70% 75% alcohol. 30min in 4%NaOH, 3%HCl and 6%H2S04 has relative tolerance and its activity is not affected, so in the experiment, it is often used to deal with miscellaneous bacteria in disease materials, and it is also often added to the culture medium to control miscellaneous bacteria.

Mycobacterium tuberculosis is not sensitive to commonly used sulfonamides and antibiotics. Antibiotics such as streptomycin, cycloserine and isoniazid, aminosalicylic acid and rifampicin have bacteriostatic or bactericidal effects.

Epidemiology

Mycobacterium tuberculosis mainly affects poultry and birds, pigs also have susceptibility, followed by cattle, sheep, human, dog, cat and deer. All birds can be infected with avian tuberculosis. The susceptibility of experimental animals to rabbits was high. Poultry of all breeds and different ages can be infected. Due to the slow development of the disease, it is often found in aging and slaughtering.

Diseased poultry is the main source of infection. a large number of tuberculosis bacteria are excreted through feces, and respiratory secretions may also be excreted. The bacteria pollute feed, drinking water, poultry houses, soil, bedding and the environment. After being fed by healthy chickens, ducks and geese, they are mainly infected through the digestive tract. It can also be infected through the respiratory tract by inhaling bacteria-carrying dust. Sick poultry and healthy poultry are raised in the same group to spread the disease. People, breeding and management equipment, vehicles and so on can also promote communication. If the water source is contaminated, ducks and geese graze, play in the water and wild birds inhabit, they may also be infected. A considerable part of tuberculosis in waterfowl is infected by diseased chickens.

The occurrence of the disease can be promoted by poor sanitation of poultry house and environment, lax disinfection, poor management, excessive density, dark humidity, poor ventilation and so on.

Popular characteristics

All poultry animals can be infected with Mycobacterium tuberculosis, and rabbits, pigs and minks are also highly susceptible. The disease is mostly sporadic and the incidence is very low. Chicks are more susceptible than adult chickens, but most of the diseased chickens are adult chickens.

Clinical characteristics.

The sick chicken is depressed in spirit, has a normal appetite, but loses weight. Emaciation, chest muscle atrophy, sternum deformation, body size, chicken crown, meat lobe and earlobe faded and atrophied. Sick chickens often have dysentery and some are paralyzed.

Lesion characteristics

The liver of the diseased chicken was enlarged, with yellow-white tuberculosis nodules ranging from millet grains to soybeans, and some fused into large nodules. The splenomegaly is several times larger, with most of the yellow-white hard nodules. Tuberculosis nodules can be seen in small intestine, cecum, lung, bone and other tissues and organs.

Prevention and cure measures

Eliminate infected chickens, abandon old chicken sheds and old equipment, and thoroughly disinfect them. It is strictly forbidden to introduce sick chickens from other places, and quarantine should be carried out when introducing chickens. Generally speaking, treatment is not advocated for sick chickens, but can be eliminated in time. According to the characteristics of tuberculosis in chickens, preventive measures can be taken in the following aspects.

1. When tuberculosis is found in chickens, ducks and geese in poultry farms, it should be dealt with in time. Burning or burying sick and dead birds.

2. The poultry house and environment should be thoroughly cleaned and disinfected. Removed faeces, stacked fermentation, retting manure. For example, waterfowl raised on the ground should remove their feces and disinfect them with caustic soda water. If they are on the soil floor, they should shovel off the topsoil, disinfect and replace the new soil. It is difficult to completely remove the pathogen from the contaminated site, and the pathogen has remained virulent in the soil for several years.

3. If tuberculosis continues to occur in poultry flocks (such as tuberculosis during autopsy), diseased birds and emaciated old birds with little or no eggs should be eliminated. Because these birds (chickens) may be sick birds (chickens), laying few eggs, old age, from an economic point of view, there is not much breeding value, so it is more advantageous to eliminate the whole flock.

4. For layers with tuberculosis, it is the most economical and best measure to eliminate all the chickens in the flock after the first peak of egg production. Because the old chicken lays fewer eggs, the illness is more serious, and the old chicken dies, which is the most dangerous source of infection.

5. When necessary, breeding birds and rare birds (birds) should be examined for allergic reaction or rapid plate agglutination reaction with avian tuberculin. Birds with positive reactions should be eliminated to eliminate the source of infection. The rapid plate agglutination reaction is suitable for grass-roots poultry farms. The elimination of the whole group is more ideal.

6. The eggs of diseased birds cannot be used for breeding.