A few newsletters ago, I talked about the viruses that struck the pigeon harder than they used to. I discussed shortly these viruses, whereby I emphasized the practical consequences. With these newsletters arose a lot of questions about these various viruses. So in the near future I will give more information on these different viruses and discuss them a bit more meticulously.

One of the viruses in the pigeon who can cause problems is the Circovirus (PiCV). It is possible the Circovirus contributes to the apparent strengthening of several other viruses. The Circovirus is surely a virus that resides in the immune cells of the pigeon and, from there, causes its harmful effects. The Circovirus contributes to the Youngsters Disease Syndrome which increasingly affects our pigeon for many years.

The Circovirus was first described for pigeons at the end of the 20th century in Europe. The first encounter with the Circovirus was in Canada in 1986. This disease only occurs in young pigeons, from two weeks to one year old. Up to four months, the pigeons are most vulnerable.

This virus is not a seasonality virus, like the classical Adenovirosis. The mortality rate amongst nestlings and recently weaned pigeon youngsters can rise to a 100%. It is also possible that the mortality minimal is. Death occurs three to four days after the first signs of the Circovirus.

The Circovirus occurs frequently amongst young birds. How the virus infection spreads is unknown. A possibility is contamination through droppings. Also dispersion through the powder on the feathers is a possibility.

It is probably true that the majority of the youngsters are infected with the Circovirus in the dovecote for young birds. It is thought that the virus suppresses the resistance of the immune system (immunosuppression). Often when the virus is detected, they are accompanied by other diseases. It is unclear whether the deviations found at the necropsy are related to the Circovirus or the other diseases. The accompanying diseases are often the cause of death. The suppression of the resistance of the immune system is responsible for the manifestation of the secondary infection.

There is often a stress factor required for the disease to emerge. It is probable the disease is associated with poor general health of the pigeons and death amongst nestlings. This happens trough virus replication in the organs of the immune system. This results in an immune deficit and, for example, no good response to vaccination follows.

Animals, which are infected with the Circovirus at a young age, can develop a delayed growth. They can huddle together in the loft and show signs of the secondary infection that occur as a result of immunosuppression.

It is possible that many youngsters react asymptomatic on the infection. The consequences of the infection are limited when the birds are infected on a later age. At a necropsy, the findings are most likely a pale or swollen spleen, semi-liquid green stool and a green colored content of the stomach. In the bursa of Fabricius (an immune organ at the cloaca of the pigeon) inclusion body are found.

Using the PCR, the DNA of the virus was detected in the respiratory tract, kidneys, liver, ovaries and testis. When there is virus DNA found in the embryos, the transfer of the virus from the parent to the eggs is not excluded. There were also older healthy birds that contained the DNA of the virus.

Research revealed that young bird can carry the virus for more than 26 weeks. The pigeons involved in this study did show symptoms of the virus, like respiratory problems, vomiting, diarrhea and weight loss.

Diagnostics
The diagnosis was previously made based on histological evidence of inclusions bodies (using microscopic sections) in bursa. Today there is a sensitive PCR test which shows the virus in the cloaca, the bursa of Fabricius, the liver and the blood. Researched showed that the virus is longer detectable in the cloaca swabs than in blood. In practice, this could make diagnosing the Circovirus easier.

Control
Circoviruses appear to be fairly resistant against commonly used disinfectants. The virus is also well adapted to heat. Half an hour at 60 degrees Celsius does not destroy the Circovirus.

Treatment
Diagnosing this disease is, in normal field conditions, hard. When the symptoms persist, further research is necessary. Further diagnosis is possible with the development of the sensitive PCR/PCT test.

Vaccination for this virus does not exist (yet). This makes treatment difficult. Supportive therapy, which supports the resistance of the immune system, should help to curb disease severity.

Discussion
What are the practical effects of this Circovirus?

How does a pigeon contract this virus? That a question I hear often in the office when we discuss the possibility that the youngsters are infected with the Circovirus. That is a good question. It is not always clear where the virus originated. For example, the flu viruses. By mixing viruses of pigs, chickens and/or humans, there can suddenly arise to a new variant which can create even more damage. In humans of animals with a low resistance the damage will be much greater than the humans or animals with a healthy resistance. Hence, the idea had been suggested that the improper use of cortisone in the last century contributed to, in case of the Circovirus, the easy access to the pigeons. After all, these cortisones reduce the immune response of the body of pigeons with these aforementioned consequences.

The fact is that the mass of the pigeons carry the virus. Indeed, research show that a lot of birds, even much older pigeons, carry the genetic material of the virus. That does not mean the pigeon is ill, but it gets you to think. The Belgian researcher Tavenier conducted a research and the results are as following. The screening showed about 19% of the young birds was infected with the virus. In March, April and May, the percentage was even higher, between 25-31%.

A substantial part of the youngsters comes in contact with this virus. This does not always lead to a disease. A research in which they tried to artificially infect the pigeons, did not led to the desire effect. Apparently, there has to be a stress factor involved, will the pigeons actually become ill. And that condition is in the pigeon easily met. Especially if the infection pressure of the virus is high. In travel baskets, but also by adding youngsters in the loft, the stress level will rise. The virus can seize the opportunity and make the birds sick.

The moment when the virus reaches the pigeon is crucial for the course of the possible infection. After all, a defense organ has yet to develop. In pigeons, this is the case in the first year of life. If the virus reaches the pigeon shortly after birth, the harmful effect are much greater than when this happens later in life. Indeed, at a young age, the defense systems are not yet fully developed.

The defense organ has to develop just like the rest of the body and organs. Through the bursa of Fabricius, the little organ next to the anus, the immune cells are distributed throughout the whole body. This makes it understandable that if the infection occurs at a young age, the effects are much more severe. I once compared this to an exploding powder magazine. When all cells (powder) are distributed the effect of an explosion will be smaller than when all powder is stored centrally.

If the infection of the Circovirus is diagnosed, all hell is about to break loose. All kinds of infections that normally are easy to resolve, prove to be much more problematic. The animals are much more receptive for all additional infections. When these infections suppress the resistance even more, the death rate will increase even more.

Young Pigeon Disease

Lately, we have use the term Young Pigeon Syndrome more than the former name: Coli.

In the nineties, it was mainly the Adenovirus, whether or not in combination with E. Coli, who could cause problems. Now, we mostly see mixed infections, where on times the Herpes virus predominates and the other times the Adenovirus, with or without E. Coli, predominates.

The treatments that used to be quick and successful, in some cases, are nowadays much less effective.
The cause, therefore, could as well be an underlying infection, like the Circovirus. The viruses that were less of a problem, like the Herpes virus, have developed because of the diminished immune response of the pigeons. Since 2005, we are seeing more and more infections of the Herpes virus at young pigeons. Hopefully, we can soon begin vaccinating against this virus, so our problems with the Young Pigeon Syndrome become more manageable. In my opinion, a single vaccine against the Herpes virus is not the answer, as long as there is not a vaccine against the Circovirus. But, we will take anything.

Paramyxovirus vaccination

The risk of infection at a young age with the Circovirus is one of the reasons that vaccinations take place at a preferable young age of five weeks. Paramyxosevirosis is amongst one of them. After all, if the pigeon is not infected with the virus, the immune reaction will protect the pigeon against the Paramyxovirus. However, if the pigeon is infected with the Circovirus, the protection by the vaccine is moderate to nil. After all, the Circovirus settles preferably in the immune cells of the pigeon, which the reaction of these cells hardly exists. Even more, these immune cells are destroyed by the Circovirus. This means, in case of the Paramyxovirus vaccination, that the vaccines have little to no effect. The pigeons can still develop symptoms of the Paramyxovirus. And of course, we will shout out about the vaccine, about their affectless. But in these cases, the quality of the vaccines is not to blame. The reason is the damned Circovirus. In some cases, I will advise to administer twice the Paramyxovirus vaccine.

But even if we want to vaccine against other viruses than Paramyxovirus, we can administer the vaccine as early as possible for these reasons. An exception is the small pox vaccination. The pigeons can not be vaccinated earlier than five weeks because of the reaction on the vaccination.

The virus can possible survive in the respiratory tract in old pigeons, and for this reason can this virus remain in the dovecot. This could be the reason why some pigeon fanciers do not experience a great death rate amongst their youngsters (in the breeding loft). If there is no clarity through bacteriological cultures, because of E. Coli or Streptococci, the Circovirus test proves to be useful. This will not resolve the problem, because this is an infection and there are no known drugs for. These tests can clarify why the administered drugs had no effect.

The Circovirus can lead to disappointing flight performances, so our goal is to keep the infection pressure as low as possible. We can achieve this through upgrading the hygiene. But we also have to realize that this virus is accustomed to high temperatures and a number of commonly used disinfectants. Disinfection can help, but not everything will be resolved.

The same goes for antibiotics. It concerns a viral infection, and viruses are not susceptible to antibiotics. Using antibiotics, we can fight the secondary diseases, but not the Circovirus itself.

Everything has to be focused on keeping the resistance of the immune system as high as possible for pigeons of all ages. Especially when it is more than likely the stress factor is an important factor in activating the virus. So increasing the resistance of the immune system is important.

In the fall it is important to give the moulting birds optimum support. Also testing of banal infections after moulting is important, so there are no infections in the immune system of the pigeons, so the resistance stays high.

As you all know, I am a great partisan in the natural support of the resistance of the immune system of the pigeons. Starting at a young age, can help us lower the infection pressure which is a threat to our pigeons. Thus, we have to prevent that our young pigeons infect other youngsters in breeding period. This is the only way to break the cycle and prevent the fanciers form another disappointing year.

Young Pigeon Disease can be considered as a syndrome in which multiple diseases contribute a bit. Many of these diseases have a chance of infecting the (young) pigeons, because of the low resistance of the immune system.
So it is on one hand important to fight of secondary diseases, like E. Coli, coccidiosis, worms and trichomatosis. The infections are treatable. On the other hand, supporting the immune system and if possible, vaccination against the most common infections amongst youngsters are also important. It is to be expected that the vaccine against the Herpes virus soon available is. So we can fight yet another assassin in our pigeon midst.

Natural resources to support the resistance of the immune system
In my previous newsletters, I talked about the fact that the fall is the ideal time to seriously support the general health of your pigeons through natural resources. Last September we have launched a new website that fully supports the natural approach of Bony Farma: www.bonyfarma.com

Good luck!

Peter Boskamp