A crow is blinded in one eye with an infection of avian pox. (Photo by Kerry Howard)

A crow is blinded in one eye with an infection of avian pox. (Photo by Kerry Howard)

On the Trails: Avian flu ailments

Among the many diseases that afflict wild birds, there is avian flu, which made national news when it began decimating flocks of domestic turkeys and chickens. This very pathogenic strain (known as H5N1) of the avian flu virus emerged from Asia in the 1990s and quickly spread around the world.

It is known to occur in over a hundred species of wild birds. It caused outbreaks in 2004-2006, and as of early 2022, it was officially reported in geese and especially eagles in Alaska. This virus has seriously damaged some wild bird populations: California condors, pelicans in South America, skuas in Scotland, for example. Raptors are said to be very sensitive to flu virus, and waterfowl often carry and transmit it. Songbirds are (so far) less affected. Bird flu is also known to affect mammals of various species.

The virus is shed in saliva, mucus, and feces of infected birds. It is transmitted to other birds by direct body contact, inhalation of air-borne cells, and especially by ingestion (by eating infected birds or carcasses or incidentally ingesting fecal material (such as that dispersed in marshes and ponds).

A raven has a serious case of avian pox on the face, blinding one eye. (Photo by Bob Armstrong)

A raven has a serious case of avian pox on the face, blinding one eye. (Photo by Bob Armstrong)

The bird flu virus affects respiratory and gastrointestinal tracts. Some common strains have relatively low pathogenicity. The very pathogenic strain can cause lack of energy and loss of appetite, diarrhea, nasal discharge, coughing, sneezing, lack of coordination, tremors, swelling and discoloration of featherless parts, decreased egg production, and sudden death.

Less widely known is another nasty virus called avian pox; it’s in the same taxonomic family as smallpox and monkeypox. It can have several different effects; if it becomes (uncommonly) systemic, it can lead to anorexia and depression, or it might invade the mucus membranes and upper respiratory tract, causing respiratory distress. But the best known and most easily visible to observers is the eruption of raised lesions (or “poxes”) on the bare skin of the face, legs, and feet. The external lesions can last as long as a month, sometimes causing blindness, beak deformations, and loss of feet and toes. An afflicted bird can recover and develop antibodies, although the lesions may leave some scars, but a seriously debilitated bird may starve and die. The lesions also create open wounds that bacteria can enter, leading to secondary infections, and the immune system may be suppressed.

Avian pox contributed to the extinction of several bird species in Hawaii. Cases of avian pox in various species here have been reported here in the past, especially in crows and ravens. This year (September 2023) photographers have recorded the pox in crows at The National Shrine of Saint Thérèse and a raven at Eagle Beach. Sadly, the raven seemed to have a really bad case, apparently almost blind and having difficulty feeding (https://youtu.be/eA1mJbTJY5s, thanks to Bob Armstrong for the video). Outlook: not good.

An infected bird in captivity may receive topical treatment of the lesions with an iodine solution such as betadine. The lesions also may be debrided and dosed with antibacterial medicines. And the diet might be supplemented with vitamins and extra fluids to help healing and reinforce the immune system. Local rescuers were able to heal and eventually release an eagle that was cared for in this way.

The virus often enters through openings in the skin, sometimes via a bite of an insect (mosquito, fly, flea) that previously fed on an infected bird. But the virus can also enter from an infected perch or bird feeder through existing skin abrasions. And it can enter a bird via inhalation or ingestion. So it has many ways to get around. But where does it live in the meantime? I’ve (so far) found no information about where it lives in between detectably infecting birds.

Avian botulism can be another serious problem, caused by a Clostridium bacterium that produces a potent neurotoxin. That toxin causes failure of muscles involved with walking or flying, respiratory and cardiac paralysis, and death. The bacterium is widely distributed in soils and water, and can be incidentally consumed by animals that filter their food from sediments or water. Shoveler ducks are good filter-feeders and may take in the bacteria while they feed. Other birds, such as loons and gulls, eat fish and invertebrates that can be infected and pass the bacteria on to the predators. Maggots feeding on dead fish or other animals are a choice food for lots of birds, but those maggots can accumulate the bacteria or the toxins and pass them on to maggot-eaters (this species of Clostridium does not affect mammals, who get botulism from related bacteria). The abundance of botulism bacteria is thought to increase in warm waters with low oxygen, increasing the likelihood of transmission to invertebrates and birds. Botulism has caused or contributed to many avian mortality events around the world. The first recorded botulism outbreak in Alaska occurred in 2021, when there was a considerable die-off of kittiwakes, showing the characteristic symptoms, on Middleton Island.

Another serious source of avian disability and mortality comes from pesticides. Some are acutely toxic, while others have less immediate detrimental effects. Pesticides are applied to both terrestrial and aquatic environments, and run-off from treated lands to water distributes the pesticides more widely. The chemistry of these pesticides and their effects would fill books, so here I’ll just note that pesticides taken up by the “pests” (insects, rodents, etc.) are passed on to avian consumers, with serious negative effects. So birds that eat worms or bugs or fish from pesticide-treated areas are exposed to the dangerous chemicals, with documented cases of reproductive failure, morbidity, and die-offs. Also, seeds treated with pesticides can pass on those toxins to seed-eating consumers. These problems could be avoided by choosing and applying pesticides with great care.

I haven’t space to discuss the documented cases of avian mortality resulting from toxic run-off from mining activities. But that has been a serious problem in some regions and is a continuing threat wherever mining activities drain into rivers and lakes, including several river drainages in Southeast.

• Mary F. Willson is a retired professor of ecology. “On The Trails” appears every Wednesday in the Juneau Empire.

More in Neighbors

A reflection of a cold-water dip in Sitka Sound. (Photo by Bethany Goodrich)
Woven Peoples and Place: We are coming out of the water

For the second year, the Sustainable Southeast Partnership is releasing “Woven” as… Continue reading

(Photo by Gina Del Rosario)
Living and Growing: The call to pray the rosary

In many of the Marian Apparitions all over the world, the Blessed… Continue reading

Rich chocolate cream pie. (Photo by Patty Schied)
Cooking For Pleasure: Rich chocolate cream pie

About once a year I indulge myself with chocolate cream pie, using… Continue reading

Brent Merten is the pastor of Christ Lutheran Church, Juneau. (Courtesy photo)
Living and Growing: It wasn’t ropes or nails

Christianity Today published an online article during Holy Week titled, “Was Jesus… Continue reading

Jennifer Moses is a student rabbi at Congregation Sukkat Shalom. (Photo provided by Jennifer Moses)
Living and Growing: How we live our lives and pass on our values to our children

When my mother was dying of the breast cancer that had spread… Continue reading

Decluttering starts with making room on a desk for a list. (Winnie Au/The New York Times)
Gimme A Smile: Declutter like a boss

I’m trying to declutter. I pronounce those words in the same abashed… Continue reading

(Michael Penn / Juneau Empire file photo)
Living and Growing: It is all about the resurrection

This past weekend Christians celebrated the resurrection of Jesus. His resurrection from… Continue reading

Tortilla “dry soup” ready to consume. (Photo by Patty Schied)
Cooking For Pleasure: Tortilla ‘dry soup’ (sopa seca de tortillas)

This recipe is based upon one in an old Mexican cookbook I’ve… Continue reading

A rainbow spans the University of Alaska Southeast campus in September of 2024. (University of Alaska Southeast photo)
Sustainable Alaska: Reading relations

For the program’s 14th iteration, UAS’s One Campus, One Book committee selected… Continue reading

(Photo provided by Gina Del Rosario)
Living and Growing: Holy Week

Filipinos are known all over the world for their strong faith in… Continue reading

The downtown Juneau cruise ship dock on a clear March day. (Mark Sabbatini / Juneau Empire file photo)
Living and Growing: Seeking joy during times of great uncertainty

“This is the greatest act of power I have come to know:… Continue reading

Mary’s extreme bars, ready to slice. (Photo by Patty Schied)
Cooking For Pleasure: Mary’s extreme bars

For at least 20 years, my sister Mary Watson has been making… Continue reading