Fowlpox is a highly contagious disease caused by avipoxvirus. Avipoxvirus belongs to the genus Avipoxvirus, subfamily Chordopoxvirinae, family Poxviridae. The virus is abundant in lesions of the skin and mucous membranes and is highly resistant to environmental conditions. It can survive for several months or even longer in dried scabs. This disease is widespread around the world. It often slows the growth of affected birds and reduces egg production, particularly in large poultry farms. Secondary infection with Staphylococcus or Escherichia coli can cause mass mortality, especially among young birds, often resulting in severe losses. 

　　I. Epidemiological Characteristics

　　This disease occurs mostly in autumn and early winter. Mosquitoes and ectoparasites can transmit it. Mosquitoes can carry the virus for up to 10 to 30 days. Transmission often begins through contact between sick and healthy chickens. Shed and fragmented scabs are the main means by which the virus spreads. Birds of any breed, sex, or age can be infected.

　　II. Symptoms and Postmortem Changes

　　The incubation period is 4 to 8 days. Depending on the site affected, the disease is classified as cutaneous (also known as the dry form), mucosal (the wet form), or mixed.

　　The cutaneous form commonly occurs on the comb, wattles, corners of the beak, eyelids, and earlobes. A distinctive pox rash may also develop on the legs and feet, cloaca, and inner sides of the wings. Early in the disease, a thin, gray, bran-like covering appears on the skin, and nodules rapidly develop, becoming yellowish gray with a rough, dry, hard surface. When numerous, the nodules may merge and form large scabs, causing the eyes to close completely. Affected chickens become lethargic, lose their appetite, have rough, disheveled feathers, and grow slowly or stop growing. In the later stages, black pox lesions and scabs the size of soybeans form on the comb, wattles, and other areas.

　　Mucosal form: Pox lesions appear mainly on the mucous membranes of the mouth, throat, and eyes, as well as on the mucous membrane of the larynx and trachea. It is also known as the diphtheritic form. Early symptoms include rhinitis, sneezing, nasal discharge, panting, and rattling sounds in the trachea. The discharge is initially serous and later becomes purulent. The conjunctiva becomes inflamed; the eyes are initially moist, then discharge tears with fine bubbles, and the eyelids gradually swell. As the disease progresses, thick, pale-yellow pus appears in the eyes. The affected chicken's eyes become markedly swollen, and the upper and lower eyelids stick together, causing keratitis and blindness. 2一一3 days after rhinitis symptoms appear, pox lesions develop on the mucous membranes of the mouth, throat, and other areas. Initially, they appear as round yellow spots, which gradually spread into large deposits, also known as pseudomembranes. These then thicken into brown scabs with an uneven surface and cracks. The scabs are difficult to remove; forcibly tearing them off leaves a red surface that bleeds easily. If the pseudomembrane extends deep into the larynx, it may cause difficulty breathing. The symptoms resemble infectious laryngotracheitis: the chicken stretches its neck and breathes with its beak open, and may even suffocate and die.

　　Mixed form: The chicken has both the cutaneous and mucosal forms.

　　III. Prevention and control measures

　　Maintain cleanliness and sanitation at the poultry farm and in the surrounding area, disinfect regularly, and promptly control insects and mosquitoes. If the disease is detected, immediately isolate affected birds; cull severely ill birds; deeply bury or incinerate dead birds; and promptly destroy removed scabs.

　　The most effective way to prevent this disease is planned vaccination. Use a live attenuated fowlpox vaccine adapted to quail, diluted with sterile physiological saline, and administer it by subcutaneous wing-web puncture in an area without blood vessels. Give one puncture at 10～20 days of age; the immunity period is 2 months (in autumn, vaccination can be given earlier, at 6～7 days of age). Give the second vaccination at 90～100 days of age before the onset of lay; the immunity period is 4～6 months. Check the puncture site 3～4 days after vaccination. Mild redness, swelling, and scab formation indicate successful immunization; otherwise, revaccinate. To prevent fowlpox in autumn, give susceptible, healthy birds a booster vaccination against fowlpox in early 8 to raise antibody levels and strengthen immunity.

　　Pox lesions on the skin of affected chickens generally do not require treatment. If treatment is given, carefully remove scabs from the comb, nostrils, eyelids, and other areas with forceps, then disinfect the wounds with iodine tincture or gentian violet. Remove pseudomembranes from oral lesions with forceps, rinse with a 0.1% potassium permanganate solution, then apply Bingpeng San. For chickens with swollen eyes, first squeeze out the cheese-like material, then rinse with a 2% boric acid solution. In chickens with difficulty breathing, carefully remove the pseudomembrane from the larynx with forceps and apply iodine-glycerin.

　　In the early stages of fowlpox in chicks, emergency vaccination with fowlpox vaccine at 2–3 times the dose can control disease progression.

　　IV. Case Description

　　Lv, a resident of Chenquetun Village, kept 1000 laying hens. The disease began at 30 days of age. Initial respiratory symptoms included sneezing and nasal discharge. Some chickens developed photophobia in one or both eyes, tearing and swelling, and a few died.

　　1, Clinical Symptoms

　　Affected chickens were lethargic, with ruffled feathers and reduced appetite. They showed symptoms of rhinitis, sneezing, nasal discharge, and rattling sounds in the trachea. Their eyes were sensitive to light and watering, and their eyelids were swollen. In severe cases, the nasal and ocular discharge was purulent, and the upper and lower eyelids became stuck together, causing blindness. Thin, grayish-white, bran-like coatings appeared on the comb and wattles, later forming raised lesions about the size of a soybean that merged into patches and turned dark brown after drying. Severely affected chickens had difficulty breathing and could even die from suffocation.

　　2, Postmortem Findings

　　Rice-grain-sized nodules developed on the comb, eyelids, and conjunctiva. The conjunctival sac was filled with purulent discharge. When the eyelids were pried open by hand, caseous material could be seen. After it was squeezed out, the eyeball was found to be atrophied, and blindness could result. On dissection, small yellowish-white nodules were found on the mucous membranes of the mouth, throat, and trachea; some formed caseous pseudomembranes. Removing the pseudomembranes exposed red, bleeding surfaces. Some pseudomembranes blocked the throat, causing death by suffocation.

　　3, treatment

　　Isolate chickens that have fallen ill and cull severely ill chickens. Disinfect the flock once daily. Administer interferon by eye drops at 2 times the dose. Mix antiviral Chinese herbal medicines, such as Isatis leaf, Banlangen, and Astragalus, into the feed for the entire flock and use for five consecutive days; results are good.