Avian pox is a viral infection that affects wild and domestic birds. It causes wart-like lesions on the skin and mucous membranes of infected birds. Here is a quick overview of what avian pox looks like on birds:
Cutaneous Form
The cutaneous form of avian pox causes wart-like nodules on the featherless areas of a bird’s body, such as the legs, feet, eyelids, base of the beak, and head. The nodules start out small but can grow large, up to 1-2 cm in diameter. They may be grayish, yellowish, or brownish in color. The nodules have a circular shape and firm, warty texture.
In the early stages, the nodules may just look like raised bumps on the skin. As they develop, the centers often become indented or ulcerated. Scabs may form over the lesions. In some cases, the warts can become so numerous that they coalesce into cauliflower-like masses.
Birds with cutaneous pox may have just a few scattered nodules or have them covering their entire legs and feet. The nodules themselves are usually not painful, but they can cause problems with vision or eating if they grow large on the eyelids or beak.
Diphtheritic Form
The diphtheritic form affects the mucous membranes in a bird’s mouth, throat, trachea, and esophagus. It causes thick, yellowish plaque-like lesions that can cover the entire mucous membrane surface.
These plaque-like masses are composed of cellular debris, bacteria, and avian pox virions. They have an irregular surface and cheesy or curdled appearance. The lesions often become thick enough to obstruct breathing and swallowing.
The diphtheritic form also causes wet, crusty lesions inside the beak and back of the throat. It can lead to problems such as difficulty breathing, swallowing, and feeding.
Which Birds Are Affected?
Avian pox can affect several types of wild and domestic birds, including:
- Chickens
- Turkeys
- Ducks
- Geese
- Pigeons
- Sparrows
- Finches
- Blackbirds
- Crows
- Hawks
- Owls
- Eagles
- Vultures
The disease occurs worldwide and can cause sporadic cases or outbreaks in both commercial and backyard poultry flocks. Wild birds are also susceptible, especially those in the orders Passeriformes and Falconiformes.
Transmission
Avian pox is spread between birds by direct or indirect contact:
- Direct Contact: The avian pox virus can be transmitted directly between birds when they have close contact, such as pecking, mating, or fighting with an infected bird. This allows pox lesions or contaminated secretions to be transferred between them.
- Indirect Contact: The virus can also spread indirectly via mosquito bites. When a mosquito feeds on an infected bird, it picks up viral particles and can then transmit pox to other birds it bites. The disease can also spread through shared feed, water, perches, and equipment contaminated with pox virus shed from lesions.
Mosquitoes are the primary transmission route for avian pox in wild birds, while direct contact is more common in poultry flocks. Once a bird is infected, it takes 10-14 days for visible lesions to appear.
Progression of Lesions
The lesions caused by avian pox tend to progress through several stages:
- Macule Stage: Circular, light-colored spots appear where the virus initially enters the skin or mucous membranes.
- Papule Stage: Small swellings develop where infected cells proliferate. Papules may be white, pink, or yellow.
- Nodule Stage: The papules turn into larger nodules or wart-like growths.
- Pustule Stage: The nodular lesions often develop crusty scabs, ooze fluid, or become ulcerated in the center.
- Scab Stage: Scabs eventually form over the resolving lesions as they heal.
The entire life cycle of a pox lesion may take 2-6 weeks. Lesions typically start regressing after 2-3 weeks. However, birds can remain infected for up to a year after exposure.
Differential Diagnoses
There are some other conditions that could potentially be mistaken for avian pox based on similar skin lesions:
- Fowlpox: Causes wart-like nodules on the skin of chickens and turkeys that can look similar to avian pox.
- Feather cysts: Can produce circular, raised masses on the skin, especially body and wings.
- Avian sarcoma viruses: Cause tumor-like masses in various tissues.
- Cutaneous candidiasis: Fungal infection leading to scaly skin lesions.
- Bumblefoot: Bacterial infection causing swollen foot pads.
However, other disease characteristics like affected species, lesion location, and microscopic appearance can help differentiate these conditions from avian pox.
Diagnosis
Avian pox is typically diagnosed by:
- Identifying characteristic pox lesions during physical exam
- Microscopic exam of lesion scrapings or biopsies
- Serology tests to detect antiviral antibodies
- PCR testing to detect viral DNA
- Virus isolation from scabs or lesion samples
When examined under a microscope, samples from pox lesions often reveal large eosinophilic intracytoplasmic viral inclusions called Bollinger bodies. These inclusions are found within infected epithelial cells.
PCR and virus isolation provide the most definitive diagnosis by confirming the presence of avipoxvirus particles in a lesion.
Treatment
Unfortunately, there is no specific treatment for avian pox itself. Supportive care aims to minimize complications until the infection runs its course:
- Keep infected birds warm, hydrated, and well-nourished.
- Soft, moist food may be easier to eat around oral lesions.
- Clean and disinfect lesions to prevent secondary bacterial infections.
- Treat any secondary infections with antibiotics if needed.
- Remove excessively large facial lesions that obstruct vision or feeding.
- Use insecticides or nets to control mosquito populations and transmission.
- Separate infected birds to avoid spread to other flock members.
Birds that survive infection usually recover fully within 2-6 weeks as the lesions regress. However, secondary bacterial infections are common and can be fatal in debilitated birds.
Prevention
Preventing avian pox involves both sanitation measures and vaccination:
- Avoid introducing infected carrier birds into an unaffected flock.
- Isolate and test any new birds before adding them to a flock.
- Control mosquito populations around birds.
- Disinfect any equipment used for infected birds.
- Quarantine and promptly remove any birds showing lesions.
- Vaccinate high-risk birds using live fowlpox vaccines.
- Maintain good sanitation and biosecurity practices.
In commercial operations, vaccination with live fowlpox vaccines helps protect flocks by inducing cross-protection against pathogenic avipoxviruses. However, these live vaccines can sometimes cause mild cases of avian pox themselves.
Prognosis
The prognosis for avian pox depends on the severity of infection and the bird’s overall health. Mild infections with few skin lesions generally resolve on their own. More severe cases have a poorer outlook, especially if the lesions obstruct feeding or breathing.
Cutaneous pox usually has a good prognosis if secondary infections are successfully treated with antibiotics. The diphtheritic form often has a poorer outlook since the plaque-like lesions can severely impact breathing and swallowing.
Young birds, stressed or malnourished birds, and wild birds tend to suffer higher mortality from avian pox. But for healthy birds provided supportive care, the prognosis is often good for full recovery.
Key Takeaways
- Avian pox causes wart-like skin nodules and plaque-like lesions in the mouth and throat.
- It is spread between birds by mosquitoes or direct contact.
- Diagnosis involves microscopic exam and PCR testing of lesions.
- Treatment is supportive care until lesions resolve.
- Prevention involves sanitation, mosquito control, and vaccination.
- Prognosis is good in mild cases but poorer with extensive lesions.
Frequently Asked Questions
What do avian pox lesions look like?
Avian pox causes two types of lesions – cutaneous form on the skin and diphtheritic form in the mouth/throat. Cutaneous pox causes circular, wart-like nodules on the head, legs, and unfeathered areas. Diphtheritic pox causes yellowish plaque-like masses covering the mucous membranes.
How do birds get avian pox?
Avian pox is transmitted between birds by infected mosquito bites or direct contact with open lesions and contaminated secretions. Sharing surfaces, feed, water, and equipment can also spread pox between birds through contact with infected skin cells and fluid.
What birds get avian pox?
Many species of domestic poultry like chickens and turkeys are affected. Various wild birds can also get pox, especially passerines (sparrows, finches) and birds of prey (hawks, eagles). The disease occurs worldwide in both commercial operations and backyard flocks.
How is avian pox diagnosed?
Avian pox is diagnosed by microscopic examination of skin/lesion samples, PCR testing, virus isolation, and serology. Finding characteristic large viral inclusions called Bollinger bodies is highly suggestive. PCR provides the most definitive diagnosis by detecting viral DNA.
How is avian pox treated and prevented?
There is no specific treatment for avian pox itself. Supportive care helps birds recover. Preventive measures include mosquito control, sanitation, quarantine, and vaccination. Live fowlpox vaccines help prevent disease by inducing cross-protection against pathogenic avipoxviruses.
What is the prognosis for avian pox?
Mild infections generally resolve well if birds are cared for supportively. More severe cases with extensive skin or mouth lesions have a poorer prognosis. Overall, the outlook is good for healthy birds to fully recover once the 2-6 week infection runs its course.
Conclusion
Avian pox is a challenging viral disease for both commercial and backyard poultry operations. Proper control measures are necessary to limit its spread and impact. When outbreaks do occur, supportive care helps most birds recover fully within several weeks as the characteristic skin and mucosal lesions regress. Vaccination helps prevent disease in flocks at high risk of exposure.