Taxonomic name: Avipoxvirus
Common names: avian diptheria (English), canary pox (English), contagious epithelioma (English), fowl pox (English), junco pox (English), mynah pox (English), pigeon pox (English), poxvirus infection (English), psittacine pox (English), quail pox (English), sparrow pox (English), starling pox (English), turkey pox (English)
Organism type: micro-organism
Avian pox is a relatively slow-spreading viral disease in birds, characterised by wart-like nodules on the skin and diphtheritic necrotic membranes lining the mouth and upper respiratory system. It has been present in birds since the earliest history. Fowl pox can be transmitted by direct or indirect contact. Direct contact with infected birds, ingestion of food and water contaminated by sick birds or carcasses, or contact with contaminated surfaces such as bird feeders and perches. Avipoxvirus is transmitted in locations where birds are in close contact, such as in aviaries and rehabilitation centers. The virus enters through abraded skin. Insects, especially mosquitoes, may act as mechanical vectors.
According to Esposito (2002), virions are enveloped, pleomorphic, brick-shaped, and 200 nm in diameter. The nucleocapsids are brick-shaped with obvious regular surface structure (knobby tubular or thread-like material wound around the particle).
According to Hansen (2001), avian poxvirus can withstand considerable dryness, thereby remaining infectious on surfaces or dust particles. Mosquitoes are an important vector, and the virus appears to correspond with seasonal mosquito cycles. Whitmarsh (1997) explains that each virus strain is infective for a number of species of birds. This includes a variety of birds worldwide: upland game birds, songbirds, marine birds, parrots, some raptors, and a small number of waterfowl. Pox outbreaks are commonly reported in aviaries, rehabilitation centers, and other places where confinement provides close contact among birds (Hansen, 2001).
Whitmarsh (1997) explains that the disease can be a significant mortality factor in some upland game bird (fall and winter), songbird (winter), and raptor populations. Fowl pox usually spreads slowly, and a flock may be affected for several months. The course of the disease in the individual bird takes three to five weeks. Affected young birds are retarded in growth. Laying birds experience a drop in egg production. Birds of all ages that have oral or respiratory system involvement have difficulty eating and breathing. The disease manifests itself in one of two ways: cutaneous pox (dry form) or diphtheritic pox (wet form). Dry pox starts as small whitish foci that develop into wart-like nodules. The nodules eventually are sloughed and scab formation precedes final healing. Lesions are most commonly seen on the featherless parts of the body (comb, wattles, ear lobes, eyes, and sometimes the feet). Wet pox is associated with the oral cavity and the upper respiratory tract, particularly the larynx and trachea. The lesions are diphtheritic in character and involve the mucous membranes to such a degree that when removed, an ulcerated or eroded area is left.
Hansen (2001) indicates that avian pox can be caused by several strains of poxvirus and has been reported in at least 60 species of birds from 20 families, such as turkeys, hawks, owls, and sparrows.
Native range: Avian pox occurs worldwide (Hansen, 2001) and is viewed as an endemic disease (present at all times) in birds (MDNR, 2003).
Local dispersal methods
Other (local): Mosquitoes act as carriers of the disease and infect birds with their bites. Hansen (2001) notes that avipoxvirus is transmitted in locations where birds are in close contact, and it can be transmitted by direct or indirect contact. The virus may enter directly from infected birds through abraded skin, through ingestion of food and water contaminated by sick birds or carcasses, or by contact with contaminated surfaces, such as bird feeders and perches.
Whitmarsh (1997) explains that birds can survive with supportive care, food, water, and protection from secondary infections. Warty scabs contain infectious viral material. Disease control recommendations are site specific. Decontamination of bird feeders, birdbaths, transport cages and banding equipment with 10% bleach and water solution is recommended. In some situations, removing infected birds can be important to reduce the amount of virus available to vectors and noninfected bird populations.
Preventative measures: Vector control may be considered in affected areas, and according to DNR (2003), eliminating standing water will control mosquitoes, the primary vectors.
Members of Poxviridae replicate in the cytoplasm of infected cells (Smith and Simpson, 2002).
Reviewed by: Prof. M.V. Dr. Ivan Literák, CSc.Department of Biology and Wildlife Diseases
Faculty of Veterinary Hygiene and Ecology. University of Veterinary and Pharmaceutical Sciences Palackého, Czech Republic.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 13 April 2005