BIRDS | wildlifediseasesofct

Diseases Threatening CT's Birds

Links are provided if you wish to learn more about a disease.

Wild birds serve as the reservoir for WNV
- Transmitted among wild birds (and humans, among other mammals) primarily by mosquitoes
- Most birds do not become sick if infected - but some do, ESPECIALLY crows and blue jays
  - Though since WNV was discovered in the United States in 1999, the virus has been detected in over 300 species of dead birds
Majority of birds do not show symptoms, but some may include:
- Uncoordinated walking, lethargy, tremors, inability to fly, rapid weight loss, green waste, blindness, lack of awareness, head droop, and abnormal body posture

Contagious infection due to bacterium Pasteurella multocida
- Different strains, but in wild birds, primarily one strain: Type 1
- Transmitted by bird-to-bird contact, contact with secretions or feces of infected birds, or ingestion of food or water containing the bacteria
Signs:
- Convulsions, swimming in circles, throwing head back between wings, erratic flight, and miscalculated landing attempts
- Mucous discharge from mouth or nose; soiling or matting of feathers, eyes, and bill; pasty or blood-stained droppings
Often see cases with large numbers of dead birds in good body condition with few, if any, sick birds present

Paralytic disease caused by ingestion of toxin produced by the bacterium Clostridium botulinum
- Widespread in soil and requires warm temperatures
- Waterfowl, turkeys, pheasants and most wild birds may be affected if they ingest the toxin directly or may eat invertebrates containing it
Signs:
- Paralysis of wings and legs; cannot control third eyelid, neck muscles, and other muscles
Birds with paralyzed neck muscles cannot hold their heads up and often drown (see picture)
- Death can also result from water deprivation, electrolyte imbalance, respiratory failure, or predation

Acute, highly contagious disease of ducks, geese, and swans of all ages, characterized by sudden death, high mortality (particularly among older ducks), and hemorrhages and necrosis in internal organs
Caused by duck herpesvirus 1 (anatid herpesvirus 1) through direct contact or contaminated water
Signs:
- Unable to stand, show weakness and depression
- Nasal discharge, watery or bloody diarrhea
- Ducklings frequently show dehydration and weight loss, as well as blue beaks and blood-stained vents
- Dead males may have prolapse of the penis

Caused by the bacterium Mycoplasma gallisepticum, well-known for causing chronic respiratory tract disease in domestic poultry and gamebirds
- Was not recognized as potentially important pathogen of wild birds until it decimated House Finch populations in the eastern United States in the mid-1990s
Signs:
- Puffy or swollen eyes, crusty appearing eyelids, cloudy fluid drainage
- Rubbing eyes on branches and birdfeeder surfaces, remaining on ground or at birdfeeder after other birds have left, colliding with stationary objects due to impaired vision

Caused by inhalation of spores of fungi in the Aspergillus group, of which A. fumigatus is the primary species responsible for infections in wild birds
All species of birds susceptible
- Majority of reported cases occur in waterfowl, raptors, and gulls
Can cause acute or chronic illness
- Acute:
  - Will die quickly from respiratory distress
  - May exhibit lethargy, dehydration, loss of appetite, diarrhea, gasping for breath
- Chronic:
  - May exhibit loss of body condition, lethargy, difficulty flying and breathing, vomiting, and diarrhea
  - May also show signs of neurological disease
- Both may also have fungus growing on respiratory tissues that resembles bread mold

Parasitic infection caused by a protozoan, different per species
- Commonly Sarcocystis rileyi in waterfowl
  - Especially dabbling ducks (mallard, pintail, shoveler, teal, black duck, gadwall, and widgeon)
- Ingest eggs of parasite in food or water
  - When eggs hatch, parasites move to form cysts at skeletal muscles
Waterfowl affected usually do not look or act sick and generally the disease is not fatal
Occasionally, severe infections may cause muscle loss with resultant lameness or weakness, making them more susceptible to predation

Caused by several different strains of avipoxvirus
Affects variety of birds, including upland gamebirds, songbirds, marine birds, the parrot family, and raptors
Transmission via direct contact with infected birds, ingestion of contaminated food, water or surfaces
- Insects, especially mosquitoes, can also act as mechanical vectors
Two forms: cutaneous pox (most common) and diphtheritic ("wet") pox
- Cutaneous:
  - Wart-like growths, sometimes in large clusters, occur around the eyes, beak, legs - any non-feathered skin
  - Leads to difficulty seeing, breathing, feeding, or perching
- Diphtheritic:
  - Growths form in mouth, throat, trachea and lungs resulting in difficulty breathing or swallowing.
- Birds with either form of pox may appear weak and emaciated

Photo by Andy Davis

Emerged in US in 2012
- Much has yet to be researched
- Believed to be in wild turkey populations throughout eastern US
Some turkeys carry the virus without becoming ill, while other turkeys can develop tumors on the head and feet, can ultimately die from it
- Look very similar to Avian Pox tumors
  - Cannot tell the difference without testing
  - May even be both!

Bacterial disease caused by Salmonella typhimurium
Spread by direct contact between birds, from contaminated surfaces/environments, food or water
- Outbreaks often associated with bird feeding stations
Songbirds, European starlings, blackbirds, common grackles, and mourning doves are most commonly affected.
No definitive signs
- Some may be carriers and appear healthy
- Others may have lethargy, ruffled feathers, droopy head, shivering, diarrhea, loss of appetite, and maybe arthritis
  - Eventually coma and death

Southeastern Cooperative Wildlife Disease Study