Detailed explanation of other diseases such as duck fungal disease and spirochetosis

Spirochetosis is an acute, septicemic infectious disease caused by Borrelia anserina in poultry and wild birds such as ducks and geese. Its main clinical and pathological features are fever, diarrhea, enlargement of the liver and spleen, and necrosis. The disease has a high mortality rate, and affected birds often die in large numbers after onset. Spirochetosis occurs worldwide, but is more common in free-range poultry in tropical and subtropical regions.

1. Pathogen and epidemiological characteristics The pathogen is Borrelia anserina, which belongs to the order Spirochaetales, family Spirochaetaceae. Spirochetes cannot grow on ordinary bacterial culture media, but can multiply in chicken embryos. In chicken embryos, the spirochete content is highest in the liver, blood and mucous membranes. Borrelia anserina has weak resistance to the external environment. In birds, it requires certain insects as intermediate hosts to survive. However, in poultry carcasses, spirochetes can survive for 31 days at 0°C, in serum for 3 to 4 weeks at 4°C, and when 10% to 15% glycerol is added to infectious blood and stored at -70°C, many spirochetes can be preserved long term. Sick and dead poultry and their excreta are the main source of infection for this disease. Susceptible birds that come into contact with sick or dead poultry and their excreta are often easily infected. The disease can also be transmitted through the bites of arthropods, mosquitoes and poultry mites, but the main transmission vector of this disease is Argas persicus. Natural infection in poultry is often caused by tick bites. The disease can occur in all four seasons, but is more common in warm, humid seasons.

2. Clinical symptoms The incubation period of natural infection is 3 to 12 days, and the mortality rate is 33% to 77%. Affected poultry show obvious clinical symptoms: poor spirits, retracted neck and drooping wings, ruffled feathers, fever, elevated body temperature, complete loss of appetite, lethargy and thirst, diarrhea, passing large amounts of green feces or loose feces mixed with white urates, and rapid emaciation, anemia, marked weight loss, nerve paralysis, paralysis, and finally coma, exhaustion and death. The course of disease is 4 to 5 days. Very few affected birds can survive and slowly recover.

3. Pathological changes Necropsy shows emaciation and anemia in dead birds, feathers around the cloaca soiled with feces, enlarged liver with hemorrhagic spots and grayish-white necrotic foci on the surface, markedly enlarged spleen with hemorrhagic spots and necrotic foci as well, enlarged kidneys, anemia, urate deposits in the ureters, hemorrhagic spots at the junction of the gizzard and proventriculus, hemorrhagic catarrhal inflammation of the intestinal mucosa, and sometimes mild fibrinous pericarditis.

4. Prevention and control measures Eliminate the intermediate host and transmission vector - Argas persicus, as well as mosquitoes and poultry mites. Immersion in 0.5% malathion is commonly used to control young ticks. A 25 to 50 mg/L solution of deltamethrin can also be sprayed or applied by brushing, or pyrethroid insecticide powders can be applied to the body surface and feathers; all of these can kill ticks on the body surface of poultry. In endemic areas, avoid introducing tick-infested poultry into healthy flocks. For affected poultry, antibiotics to which the disease is sensitive, such as penicillin, chloramphenicol, kanamycin and tylosin, all have relatively good therapeutic effects. Abroad, researchers have tried inactivated spirochete vaccines, and immunizing poultry at 8 to 10 weeks of age also has a certain preventive effect.