What are Poxvirus Infections?

Poxvirus is a legitimate concern for many bird owners, especially come springtime when the greatest number of avipoxvirus cases occur. The timing of viral proliferation in the case of poxvirus is no accident, as springtime brings with it an entirely new batch of buzzing and biting pests looking to feed upon our avian companions.

Biting insects such as mosquitoes, mites and other blood-suckers serve as the primary means of transmission for the virus. In addition, poxvirus can be transmitted directly from infected bird to uninfected bird; however, the virus must first find an “access route,” such as a cut or open sore, to penetrate the dermis and infect the bird. Skin to skin contact between birds, if the flesh is intact, is not sufficient for the spread of poxvirus. 

There are typically two prominent forms of lesions: the cutaneous form and the diphtheritic form. The cutaneous lesions, usually called “dry pox,” occur in wart or “pea-like” formations beneath featherless skin, and in areas surrounding the eyes, legs and at the base of the beak. These lesions typically recede and scab over without causing lasting damage. However, the diphtheritic “wet pox” develop along mucus membranes, including the trachea, tongue and esophagus.

Other significant locations for the lesions may include the bronchi, where they may cause respiratory distress. The mucus membranes are more vulnerable to bacterial or fungal attacks, and sick birds are at advanced risk of secondary infections.  Lesions appear to be dependent not only upon the species and age of a bird, but also upon the time of year when the bird becomes infected. Most infections occur during the wettest, warmest times of the year –  the months when mosquitoes are most prevalent.

Poxviruses are DNA viruses that infect over 60 different species of birds, both captive (caged) and free; infections may be mild or severe.

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Symptoms of Poxvirus Infections in Birds

  • Lesions, both beneath and on the skin
  • Abscesses
  • Scabs around eyes and mouth
  • Blue tint of skin
  • Breathing distress
  • Lethargy
  • Depression
  • Anorexia
  • Swelling
  • Eye discharge
  • Inflammation of the tongue, esophagus and trachea

Types

There are two forms of Avian Pox, cutaneous, or “dry pox” and diphtheritic or “wet pox.” The more common form, dry pox, has a wart-like appearance, and develops under the skin, or grows on the featherless areas around the eye and the beak, as well as the legs and feet.  The second form, wet pox, is more complicated and dangerous as the lesions occur on mucous membranes in the mouth, trachea, and sometimes on the bronchi and the lungs. Due to breathing impairment and an inability to eat, birds affected by wet pox become very ill and may develop bacterial or fungal infections.

Causes of Poxvirus Infections in Birds

Poxviruses are DNA viruses that infect over 60 different species of birds, both captive (caged) and free. Though they are just as vulnerable to a poxvirus as any bird, pet and aviary birds rarely become infected due to lesser interaction with wild birds and mosquitos. Infections occur in birds all over the world, a fact that contributes to the ongoing need for import control and quarantine. Though all avian strains of poxviruses are similar, there exists some variation per the specific type of host bird.

Each avipoxvirus is named per the avian host; examples include canary poxvirus, magpie poxvirus, quail poxvirus and psittacine poxvirus. Some birds share strains, while other viruses are species specific. While a bird may be infected with one strain of avipoxvirus, other strains, for some reason, spontaneously become innocuous to what would be a typically susceptible host.

Even though strains can cross contaminate, they remain most destructive when infecting their native hosts. A quail poxvirus may cause extreme illness or even death in a galliforme, yet may cause only mild symptoms in a psittacine (parrot). Other characteristics of avipoxviruses that may be specific to the species include the type, appearance and number of pox lesions that form on the bird. Some generalized, scattered lesions may be observable and have a wart-like appearance.

Diagnosis of Poxvirus Infections in Birds

To diagnose poxvirus in a live bird, the veterinarian will typically rely on a physical examination of the skin and lesions, as well as a reporting of the bird’s history and other signs and symptoms. A true diagnosis is accomplished dependent on the findings of viral bodies in affected tissues. A specialist may use electron microscopy to look for the bodies or else try to isolate the virus by growing it in a culture. If there are lesions around the eye, the bird may be excreting fluids or pus. It is important to distinguish such symptoms from conjunctivitis.

Treatment of Poxvirus Infections in Birds

There is no specific treatment for poxvirus infections. Supportive care is given to birds that may benefit from fluids, vitamins and supplements, assisted feedings, antibiotics and ointments in case of an eye infection. The veterinarian will discuss treatment of the lesions, but cleaning is always recommended to promote healing. 

Recovery of Poxvirus Infections in Birds

Follow veterinary directions for care of lesions and infections, and dietary changes. Mosquito prevention strategies such as eliminating or disinfecting standing water are essential. Unfortunately, poxviruses are stable, and can survive on inanimate objects, including gloves, for unknown periods of time. Sanitation and disinfection are paramount when taking care of birds because any infected surface can transmit the virus. Vaccines to prevent avipoxviruses are currently available for different species, including pigeons, chickens, canaries, turkeys, quail, waterfowl and falcons.