Fowlpox is a viral disease of hens, turkeys and many other birds produced by different strains of the Variola avium virus of the Avipox virus, Poxviridae family, which have affinity for the epithelia. Virus are very resistant and can survive for various months in the environment.

The incubation period lasts for 4 to 10 days and is characterized by cutaneous lesions in the skin of the head and/or diphtherial lesions in the mucosae of the upper respiratory and digestive tracts.

Fowlpox is a worldwide distributed disease that can appear in any season of the year. Despite this, outbreaks are related to environmental conditions such as heavy rains and high temperatures, which favor an increase of mosquitoes. These insects are the main vectors and transmit the virus when they bite a sick bird first and, then, a healthy one. They remain infective for many weeks.

Disease causes apathy, somnolence, poor appetite, weight loss and diarrhea. Respiratory disorders cause nasal secretions, lack of air, and noisy breathing. If the infection affects the infraorbital sinus, birds will have a swollen head.

Another transmission route is the mechanical one, when the virus contacts small lesions of the skin or by the exposition of infected air particles to the ocular or respiratory mucosae. Drinkers and feeders used by sick birds can also be a source of infection. Any contaminated cage, feed or clothing must be considered.

Birds raised in high densities are vulnerable, and, commonly, the disease will rapidly spread. Wild birds transmit the disease for long distances. Disease spreads slowly and many weeks can go by before it becomes a health emergency.

Fowlpox, like other poultry diseases, is of importance nowadays, because of the climate change, animal welfare and an increased consumption of ecologically raised backyard poultry. In this production system, birds are highly exposed to reemerging diseases because they are raised in open air facilities, in which it is more likely to contact migratory birds and not to know the health conditions of the neighborhood.

All these situations need to be considered by the companies that offer goods and services, because the global trend is to work towards an environment-friendly production, which is more natural and produces less residues that affect humans. This, together with the protection using vaccines, is the future.

Generally, when the disease takes place, egg production decreases, as well as chickens’ growth.

Lesions vary depending on the disease presentation. The cutaneous form is the most common one, which produces papules, vesicles, pustules, or crusts in the legs, tarsi, base of the peak, comb and wattle and around the eyes. It is often self-limiting, as, with time, lesions disappear and leave scars. Usually, mortality is low. The size and number of lesions depend on the severity of the disease. They can be extensive with galling, which generates secondary bacterial and fungal infections. Death can occur if there is breath obstruction, vision impairment or difficulty in eating feed. Also, because of secondary infections. The clinical picture gets worse when lesions are very extensive. If birds survive, they recover from the disease. Lesions completely disappear after two to four weeks after crusts fall off.

Diphtherial or wet lesions in the mucosae of the upper respiratory airways and upper digestive tract look like yellow or white plates covered by mucosae in the nasal and buccal cavities, nasal sinus, larynx, pharynx, trachea or esophagus. This form is very severe and can cause up to 50% mortality in sick birds.

Often, the conjunctiva, damaged by the fowlpox virus, is a gate for secondary infections by other bacteria, which worsen the clinical picture.

There is no treatment for birds in intensive production systems. Only birds that are valuable pets or are endangered could receive veterinary medication.

The best control measure in domestic poultry and endangered species is the prevention based on vaccination and good management practices in the farms.