Diseases in Bald Eagles

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A checkup for a young eaglet. Dr. Mike Jones gives a checkup to a young eaglet at AEF. © American Eagle Foundation.


 Aspergillosis is a very lethal fungal infection, from which only 25 percent of infected birds will recover. Many organ systems can be affected, but aspergillosis usually targets the respiratory system.

It is caused by inhaling the spores of fungi in the Aspergillus group. Aspergillus fungi are everywhere in the environment. Wildlife and humans can contract this discease, but the disease is not contagious from animal to animal or animal to person.  If a Bald Eagle’s immune system has been compromised (for example, by ingesting lead), it makes the eagle more susceptible to the disease.

Avian Pox

There are many different variants that are generally considered to be species-specific. The virus is distributed worldwide and is spread by biting insects such as mosquitoes and biting flies, but also directly by contaminated fomites (such as gloves). The virus can survive for years in dried scabs, so strict quarantine procedures and decontamination should be followed. The virus cannot pass through intact skin so there must be some sort of wound through which it gains entry. This virus is not considered a zoonotic risk. The dry or cutaneous form affects the featherless areas on the feet, around the eyes, and mouth. Nodular, ulcerated wounds with scabs form and will enlarge and worsen for 2 weeks. Most eventually regress and heal but secondary bacterial infection and substantial scarring around the eyes and eyelids can occur in the process. In addition, damage to the germinal layer of the beak can result in beak growth deformities.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott

Avian Vacuolar Myelinopathy (AVM)
This is a neurologic disease that affects water birds as well as raptors, including the bald eagle. It is believed to be caused by a toxin produced by a cyanobacterium (a blue-green alga). This bacterium grows well on aquatic plants such as Hydrilla verticillata. Eagles become affected after consuming water birds, especially coots, which have fed on this plant. It has only been reported in the south-eastern USA and has a peak in November and December.
Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott
Bumble Foot

Bumblefoot, or pododermatitis, refers to any injury, lesion, or inflammatory process on the pads of the feet and toes. It is primarily caused by pressure necrosis. It is rare in wild birds but can be commonplace in captive raptors. Bumblefoot will develop for any reason when weight cannot be borne on the contralateral leg. Therefore, it is common to see bumblefoot on the “good” foot when a bird is recovering from a fracture or other non-weight-bearing injury in the opposite leg.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott


This flagellated protozoan infects the oral cavity and upper GI tract. Pigeons and other columbiforms, as well as some passerines, commonly carry it, causing a disease known as “canker”. Raptors are usually infected after eating fresh pigeons and the disease is known as “frounce”. Large caseous/cheesy lesions are commonly found in the mouth under the tongue and around the choana. The masses can get so large that eating and breathing can become difficult and it is not uncommon for birds to become emaciated as a result.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott

Highly Pathogenic Avian Influenza

Migratory birds, especially waterfowl and poultry, can act as a reservoir but can also become clinically ill after infection. The virus is spread by aerosolization of respiratory secretions, fecal material, and by ingestion of infected waterfowl and poultry. Several strains of highly pathogenic avian influenza (HPAI) have been identified that are related to the Asian bird flu isolated in China in 2005 (Krautwald-Junghanns et al., 2008). A particularly severe outbreak occurred in the USA in 2015 and the primary wildlife vector was determined to be a species of duck. This disease is potentially zoonotic, contagious, and can have devastating consequences for local populations and the poultry industry. Kelly et al. (2008) provide a good review of HPAI pathogenesis, prevention, and control.

Clinical signs vary widely depending on the virulence of the particular strain and can range from anorexia, depression, respiratory signs, diarrhea and neurologic signs to sudden death.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott

Newcastle Disease

The disease is known as Newcastle Disease in poultry. Raptors can be infected by consuming poultry that have been vaccinated for PMV. This disease can be zoonotic and causes a mild conjunctivitis in people.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott

Sour Crop

Bacterial or yeast overgrowth due to crop stasis. Crop stasis can be caused by systemic illness and dehydration and it is more common in severely emaciated and debilitated birds.

Source: Raptor Medicine, Surgery, and Rehabilitation, D.E. Scott

West Nile Virus

Causes loss of interest in food, weight loss, listlessness, weakness, fever, tremors or seizures.

West Nile Virus is carried by mosquitos and infects humans, domestic animals, and wildlife. In wildlife, WNV typically kills scattered individuals of susceptible species in late summer and early fall. The Great Salt Lake is a major water bird migration site, and in November and December 2013, the Utah Division of Wildlife Resources estimated that 10,000 to 20,000 of the 2 million eared Grebes (Podiceps nigricollis) that were on the GSL during migration died and 85 of the 750 to 1,250 Bald Eagles (Haliaeetus leucocephalus) were found sick or dead.