Avian Influenza ('Bird Flu') and Pigeons
Gordon A Chalmers, DVM
Lethbridge, Alberta, Canada
The current worldwide concern about the spread of Avian Influenza among humans and poultry in southeast Asia also has many pigeon fanciers interested in the role of pigeons, especially racing pigeons, in this serious disease. On the basis of these concerns, it seems appropriate and timely to take a look at this disease, for the benefit of fanciers.
Influenza has been known since 1878, and is caused by a Type A influenza virus. There are three types of influenza viruses, namely A, B & C. Type A viruses have been recovered from humans, swine and horses, and occasionally, from birds and other mammals. Types B and C are usually isolated only from humans. The virus currently infecting in birds in southeast Asia is a Type A influenza virus.
Thousands of influenza viruses belonging to many subtypes have been recovered from domestic and avian species over the world. Infections in domestic or confined birds have been associated with several forms of the disease, ranging from unapparent to mild upper respiratory disease, to loss of egg production, through to acute fatal disease.
At present, Avian Influenza is recognized in two forms:
- Highly pathogenic avian influenza, also called Fowl Plague, and
- Low pathogenic avian influenza. ('Pathogenic' refers to the ability of an infecting agent to produce disease - hence, a virus that is highly pathogenic is capable of producing severe disease and often, acute death.)
The highly pathogenic form spreads rapidly among flocks of poultry and is often highly fatal. It has been noted that one gram (about 1/30th of an ounce) of contaminated droppings from infected chickens can contain enough highly pathogenic virus to infect 1,000,000 birds. Conversely, the low pathogenicity form generally causes only mild disease.
In general, free-flying wild birds do not develop significant disease following infection with influenza viruses, but infections are widespread in many of these birds. It is particularly important to note that influenza viruses are readily recovered from migratory waterfowl, especially ducks, over the world. There is a great deal of speculation about the importance of this very large reservoir of influenza viruses in wild birds. This reservoir may serve as a source of viruses for other species, including humans, lower mammals, and birds. The high rate of infection allows for the maintenance and emergence of new and potentially highly dangerous strains, by means of mutation and/or genetic reassortment.
Species of birds that become infected with the virus of Avian Influenza shed it from the respiratory tract, from the eyes, and in droppings. Spread of the virus can occur by means of droplets of liquid sneezed by infected birds, or in their droppings. Vehicles, equipment, cages, clothing, and insects in contact with these infective droplets, or with droppings from infected birds, are ready means of spread.
Now, what is the role of pigeons in Avian Influenza? To answer that question more fully, we can look at some past examples of outbreaks of the disease in poultry in North America, plus the current one in Asia, and the tests that were conducted on pigeons collected from areas in which the disease occurred.
In late 1992, antibodies to Avian Influenza were found in blood samples from a commercial flock of turkeys in the north-eastern USA. (Note that antibodies are protective substances that are produced by the defensive network of the body in response to an infection). Investigation showed that there was a possible association between this flock and live bird markets. An influenza virus designated H5N2 was isolated from birds in one location. State jurisdictions were concerned by this situation and took both control and eradication measures when appropriate. Public poultry markets, shows and exhibitions were quarantined and premises on which the virus were isolated and depopulated.
Because of the very great concern by state and federal officials for the health and economics of the poultry industry in several jurisdictions in the USA, racing pigeons were included under the umbrella of domestic poultry, and accordingly, racing was banned in a number of concerned states. To date, however, the body of scientific evidence indicates strongly that pigeons are not involved in the transmission of Avian Influenza to domestic poultry.
During an outbreak of Avian Influenza (H5N2) nine years earlier (1983-84), again in the north-eastern USA, scientists conducted a survey of wildlife to determine the potential of wild birds to spread disease locally among farms, or to carry the virus to more distant locations.
Included in this survey were
- wild and free-flying domestic ducks and geese,
- wild or free-flying domestic birds closely associated with poultry farms, poultry manure, or poultry carcasses,
- mice and rats found inside and around houses containing infected poultry, and
- wild birds of any species reported sick or dead within the quarantine zone.
Tracheal (windpipe) and vent swabs from birds and lungs from mice and rats were examined for virus. As well, in some instances, toes from birds and rodents were also collected for the same purpose. When feasible, blood samples were also obtained from birds and small rodents. Attempts to isolate virus were conducted on 4,132 birds and rodents collected within the quarantine zone. Included in this number were 473 pigeons (92.6% of these pigeons were obtained from known infected farms), 81 pigeon feet (all of them from influenza-affected premises), and seven mourning doves. None of the 4,132 samples was positive for influenza virus. Blood samples from 2,147 non-aquatic birds, including 383 pigeons, were negative for antibodies to Avian Influenza - an indication that infection by this virus had not occurred in these birds. An additional 313 birds, including 50 pigeons, collected from the quarantine zone, were also negative for influenza virus. It is important to note that experimental attempts to infect pigeons with this strain of Avian Influenza did not result in either multiplication of the virus in these pigeons, or evidence of antibodies in the blood. The results of all of these studies indicated that pigeons were not infected with Avian Influenza and did not spread it.
In the 1993 outbreak in the USA, in the period from February to May, blood samples were collected from 17 flocks of meat varieties of pigeons, mainly White Kings located within the quarantine area, for evidence of antibodies to Avian Influenza. Flock sizes varied from 2000 - 3000 birds, and represented a total of about 34,000 - 51,000 birds. Approximately 10 birds per flock were sampled, for a total of 160 birds. In every instance, all pigeons tested were negative for antibodies to Avian Influenza.
Another study published in 1996 on the susceptibility of pigeons to Avian Influenza, found that groups of pigeons inoculated with two strains of highly pathogenic influenza virus or two strains of non-pathogenic virus remained healthy during the 21-day trial period, did not shed virus, and did not develop antibodies to this disease - further evidence that pigeons are not a factor in the spread of this disease.
More recent evidence from experimental work in 2001/02 has shown that pigeons infected experimentally with the highly pathogenic form of the virus (designated H5N1, and of Hong Kong origin) did not develop signs of this disease and did not have detectable changes to this disease in their tissues. As well, virus was not found in their tissues and neither was it re-isolated from swabs of tissues. These findings indicated once again that pigeons (along with starlings, rats and rabbits used in these studies), are largely resistant to infection with this virus.
Despite these reassuring findings, fanciers should be aware of the very slight possibility that if a returning race bird, or any wild bird for that matter, drops into a poultry farm on which the chickens are infected with Avian Influenza; it could pick up the influenza virus on its feet as it walks through droppings from these infected chickens. If this bird were to fly to another poultry farm, in theory it could be a mechanical means of spreading the virus on its feet to chickens on the second farm. The importance of this fact is that Type A influenza viruses can remain viable for long periods at moderate environmental temperatures, for four days in water at 22oC (72oF), and for over 30 days at 0oC (32oF). However, as noted in earlier studies, the feet of pigeons collected from affected poultry farms were examined for influenza virus and all were found to be negative.
Given this information from the scientific literature, it is important to note the non-role of pigeons in the spread of Avian Influenza, and the fact that pigeons themselves are not infected by this virus.
The reasons for the understandable caution and concern by regulatory agencies when they are faced with outbreaks of Avian Influenza include the fact that it can be a very costly disease. For example, the US government spent over $60 million in 1983-84 to eradicate a highly pathogenic H5N2 virus in poultry flocks (both chickens and turkeys).
I hope that this brief look at Avian Influenza and the non-role of pigeons in the spread of this disease to poultry will be of some assurance to concerned fanciers. Further information on this disease can be obtained from federal or provincial/state governmental agencies.
The above article is from 2004.
The following is a more current article which was sent to me by Dr. Gordon Chalmers. I appreciate Dr. Gord's help in keeping this page current.
Avian Influenza - Update Winter 2005
Dr Paul G. Miller PhD, DVM
Pennsylvania , USA.
"For the past few months, Avian Influenza has been in the news, and some of this news has had a negative impact on the pigeon fancy. This is an attempt to clarify and elaborate on some of that information, especially as it relates to pigeons.
The news media abound with fearful stories of some new and treacherous 'Bird Flu' that will 'kill us all', (more precisely 150 million) in the latest pandemic on the horizon, the worst since 1918. Ninety nine percent of this is hype, intended to raise money for the medical bureaucracy establishment and improve business for drug companies and vaccine companies. With West Nile fading fast over the horizon, the medical establishment needs a new poster child, a dreadful disease that will 'surely kill us all' if we don't continue to support their capricious demands.
Some aspects of the current situation do raise concern, but we are light years away from anything remotely resembling a pandemic. In Asia, over the past few years, there have been some cases of humans contracting Avian Influenza from birds; the earliest of any notoriety was in Hong Kong in 1997. This infection was a H5N1 type which did indeed prove fatal in a few humans, but which did not infect pigeons and couldn't be transmitted by pigeons. (The 'H' and 'N' numbers are a technical way of characterizing the Influenza virus used by scientists to distinguish one type of Influenza virus from another; obviously if the numbers are different in two separate outbreaks, so are the sources of infection).
As times have gone on from there, human infections of Avian Influenza have occasionally occurred in Asia; all of these have been in situations where there has been extremely close contact between humans and birds. In many of these cases, the birds were chickens living in the same house as the person infected, often in hygiene and sanitary conditions far below contemporary American standards of personal and household hygiene and sanitation. As these people became ill, they were often diagnosed and treated using local medical professionals and facilities which, in some cases, are not comparable to American medical standards. Under these conditions, the fatality rate of Avian Influenza in humans in Asia has been about 50%.
In most of this, the culprit has been H5N1 type Avian Influenza. This particular strain of the Influenza virus is carried in wild waterfowl and shorebirds. In the past, this virus has not caused disease in these birds, and, as these birds migrate, they act as a wild reservoir for the disease, spreading it along their migration flyways. Domestic birds which come into contact with the virus spread in this manner are likely to become infected, and many infected species are likely to develop disease. With the relatively primitive poultry husbandry practices used in many situations in Asia, domestic poultry can easily become infected through exposure in this manner.
Over the past few years, H5N1 itself has undergone some changes. Just as pigeons are subject to the laws of Genetics, so are viruses, and just as pigeon genes are subject to genetic mutations, so are viral genes subject to mutation. Influenza is an RNA virus, and such viruses tend to have a relatively high rate of mutation. Once a mutation has occurred, the persistence of that mutation is subject to the selection forces in the environment; a favorable pigeon mutation is selected for by the pigeon fancier to produce a winning flier or a show winner. An unfavorable mutation is selected against and culled. Viruses work similarly, but with environmental forces doing the selection: virulent viruses more effectively infect their host, and are spread more efficiently. Less virulent viruses are outnumbered and crowded out. Hence, without any opposition or control, a virus would naturally tend to build up mutations enhancing virulence and it would increase in virulence, propagating more effectively within its host, transmitting more efficiently to another susceptible host and, possibly, even expanding its host range. On the contrary, a situation in which the virus is not allowed to propagate widely would obviously not be favorable for any of this, and establishing a new viral mutation would be a very remote possibility.
This is exactly the situation with the H5N1 virus itself. The H5N1 virus is found world wide, both in North America and in Eurasia. Since the group of species of birds inhabiting North America is distinct from the group of species inhabiting Eurasia, these two groups of birds can be thought of as separate, distinct populations. Also there is very little contact between birds endemic to these two areas; thus, these two populations of birds (American and Eurasian) can be thought of as entirely distinct populations of birds, each with its own unique environment. Also, in each of these populations, the H5N1 virus experiences entirely different selective forces, and hence we have emerging two distinct strains of the H5N1 virus. Just as there are different strains of racing pigeons (e.g. Sions vs Jansens), there are emerging different strains of the H5N1 virus.
In particular, as we have seen above, in Asia, there has been very little effective control over the H5N1 situation, so it has propagated largely out of control, and hence become a distinct, more virulent strain of the H5N1 virus; thus the Eurasian strain of H5N1 has now been specifically named 'Asian H5N1 HPAI'. (The 'HPAI' stands for Highly Pathogenic Avian Influenza). The Asian H5N1 HPAI strain lives up to its name very well. It is pathogenic in its natural hosts (waterfowl and shore birds) and, can still infect humans, cause disease and even death. Unfortunately, it has also extended its host range to now include pigeons. This does not mean that pigeons have become its natural host, but it now can infect pigeons and cause disease in them. Pigeons are still insignificant players in the Eurasian H5N1 scene, but they are now in the host range.
In contrast to the Eurasian situation, the American H5N1 remains well controlled. It has never had the opportunity to become highly pathogenic, mainly because it has been stamped out or controlled where ever it has been found. For foreign trade as well as public health reasons, the United States and Canada have always aggressively stamped out or tightly controlled Avian Influenza (regardless of H and N types) whenever it occurred. In this environment, it has not had the opportunity to become highly pathogenic, hence the American H5N1 is termed LPAI, Low Pathogenic Avian Influenza. For this American H5N1 strain, the prior experimental results would indicate that pigeons are largely resistant. Notice that, as much as we dislike government intrusion into our lives, both state and the federal government play a major role in defining this environment, especially keeping Avian Influenza from getting out of hand as it has in Asia.
So where does this leave us ??? Obviously that depends upon the geographic location. In the United States and Canada, the situation is as it was before: the American H5N1 has low pathogenicity, and pigeons (and humans) don't get it. That doesn't mean that we can become complacent and forget about Avian Influenza; we still need to be very vigilant and make sure that all Avian Influenza is well controlled so that we don't get into the situation we have in Asia. In particular, let me reiterate a few precautionary principles.
- Do NOT let your birds mix with migratory birds, especially waterfowl or shorebirds. All wild birds should be kept out of your loft and off your premises. Do NOT feed wild birds around your pigeon loft.
- Do NOT let your birds mix with any other domestic poultry; galliforms and waterfowl can and do get Avian Influenza, and could set up a situation similar to the Asian situation, expanding the host range into pigeons. Don't let this happen.
- Do NOT allow your birds to mix with feral pigeons, and do not allow feral pigeons into your loft.
- Avoid any and all contact with hogs, even indirect. Hogs are the 'mixing vessel' to combine the Avian Influenza strains with human adapted strains. Many of the Avian Influenza cases I have seen in domestic poultry have been associated with hogs.
- When training, keep birds under control, and do NOT allow them to just sit around outside on the loft roof; they should be either in the air or in the loft. Young birds traveling to scout the territory is fine, as long as they are flying. Except for settling, birds should not just sit on the roof.
- Races and training flights should be arranged so that the birds can make it home in a reasonable amount of time. Do NOT release into bad weather, weather 'fronts', low atmospheric pressure, high winds, other races crossing their flight path, etc.
- Do NOT import pigeons from Europe, except through approved USDA quarantine stations. Since the Asian H5N1 HPAI can infect pigeons, we must be VERY CAUTIOUS with anything from Europe. There are plenty of good birds available domestically; it is no longer necessary to import from Europe.
- In the case of an Avian Influenza break in any species, keep yourself and your birds totally clear of any contact, even indirect or incidental.
In the Asian situation, the strategy would be to keep pigeons as a minor, incidental host. Pigeons are not a major player in Asian H5N1 HPAI at this time; they are insignificant at this point. Keep it that way. Do not allow pigeons to become infected, and quickly destroy any that do become infected. Monitor for Avian Influenza by whatever means are available through your local Avian Lab or Avian Vet; and vaccinate if a vaccine becomes available and is approved. The above rules should also be observed, and modified as necessary to fit the situation.
Avian Influenza is not a major problem in pigeons. With a little bit of common sense and vigilance we can easily keep it that way, and continue to enjoy our birds for a long time to come.
Dr Paul G. Miller PhD, DVM"
This page was last up-dated on December 05, 2005
Below are your comments:
|Monday April 12, 2004|
|Although the Federal bureaucracy had almost all pigeons in BC marked for "depopulation" during the recent outbreak of Avian Influenza, fanciers in BC were fortunate for a number of reasons: |
All of this was necessary to have the federal "experts" listen to scientific evidence and abandon their emotional knee-jerk reaction. I thank both of the above gentlemen for their effort which may, some time in the future, assist me and save my pigeons from a senseless extermination. Thanks!
- The untiring work of our expert Dr Gordon Chalmers
- The untiring work of our dedicated fancier with a legal background, Kevin Ball
- Involvement of the media
|Tuesday April 13, 2004|
|Good people in the right place at the right time with a desire to inform. Many thanks guys!|
|Thursday April 15, 2004|
Halifax, Nova Scotia
|We are lucky to have a few ammong us with the skills, energy and knowledge to learn and inform on this important matter.|
|Friday August 20, 2004|
|thanks four everytingh|
|Monday November 15, 2004|
East London, South Africa
|In the course of our surveillance of HPAI in Ostriches in South Africa during July-November 2004 we tested blood samples from 53 pigeons and all of them were negative for antibodies to AI H5N2. Previous findings sush as those you have reported coupled with our own experience prompted us not to depopulate pigeons.|
wasmi al azmai email@example.com
نادي الاتحاد الكويتي لسباق حمام الزاجلkuwait, Friday October 21, 2005
|Dir seer: We are lucky to have a few ammong us with the skills, energy and knowledge to learn and inform on this important matter wasmi al azmi kuwait وسمي العازمي نادي الاتحاد الكويتي لسباق حمام الزاجل firstname.lastname@example.org|
|Wednesday October 26, 2005|
Brooklyn, New York
|I think that as pigeon fanciers we all are accountable for future problems we may encounter. I have been racing since the age of 7 and am 45 right now as i write this. Insted of sedning a sick bird to the race to elimanate it or spend the funds that you have to purchase the proper medications to cure it. I have constantly watched pigeon flyers send sick pigeons to the races, and its disturbing, and unfair to the pigeon and the other compeating fancier! Now as a result of this selfish act you have contanimated the race team of other fanciers and spread the problem.We need to more strictly enforce a health code when it comes to racing , if a bird is clearly sick then it should be stoped from being allowed into the race crate, this will nodoubtly creat a problem but its necessary. We as fanciers owe each other the respect to be concencious and not send that sick bird, insted leave it home , don't send decause it has the band for the race. If we can show that we collectively make an honest effort to police ourselves then just maby when new desises such as this Avian flu arise people will not associate our birds with the problem. My thanks to all of you who have helped us keep our beloved birds as a result of your expertise|
|Sunday November 6, 2005|
Santa Cruz de Tenerife, Santa Cruz de Tenerife
|What about the three pigeons infected in Australia?|
|Wednesday November 9, 2005|
|Please view link: http://www.inspection.gc.ca/english/corpaffr/newcom/2005/20051021e.shtml To reas about the three pigeons NOT infected with AV in Australian|
|Thursday December 8, 2005|
Ponca City, Oklahoma
|When we are banding, whom ever is handling the bird to enter will say. "Something is wrong with this bird, It cannot go." It is as simple as that when you find a sick bird. When I am crating for the banding, Ron & I look over the birds real good. If they are not in a good physical apperance they do not go. We do have to respect the Race Secretary's decisions and respect a club members comment. I agree If a pigeon is not healthy enough to send to a race and you do not expect them back home, they should not be in the crates. I would like to extend my Thanks to Dr Chalmers and the Attorney for their efforts in this World Wide event. If it were not for the work that is already overseen in the Sport of Pigeon Racing, the Fancy & Racing would be a lost cause. THANK YOU GENTLEMEN! I have only been racing for 7 years and I am hoping for a very long relationship with my Racers and fellow flyers. The feeling is like my first 600 mile day bird this past OB season 2005. I just cannot Thank those who have worked so hard all these years to keep the sport going and the pigeons flying.|
|Thursday December 15, 2005|
|Thanks for the up to date information, there were a few hundred birds in alaska( wild birds)that were tested and found negative. I dont think we are completly free and clear since snow geese from Wrangell Island (Off the coast of northern Siberia)can be found in the Central valley of California in the winter. There are millions of wild turkeys in north America that could help infected waterfowl spread virus. I live in a trailer park frequented by Ravens, Gulls and Eagles I can only assume that by eating any dead waterfowl that it is possible for them to shed live virus in their feces. I have a dog trained to keep my pigeons off the ground, and will minimize roof time. Thanks for the help.|
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