My Experience with Pigeon Circovirus

By Clint Robertson

First let me give you some background about myself and my loft management. I have been successfully breeding and showing pigeons since 1974. Along with my sons we keep 50 pairs of Jacobins, 15 pairs of Voorburg Shield Croppers, 15 pairs of W.O.E.Ts, 6 pair of Flying Rollers, several pair of Helmets, 10 pair of Oriental Frills and 100 pairs of Racing Homers primarily as foster parents. All breeds are kept segregated and are housed in 25 different compartments in 10 separate lofts spread out over a large area in two different yards. We do not fly our birds. Our birds are never crowded, always dry and all birds have access to large open fly pens and lots of sunlight and fresh air with no drafts. Our fly pens are covered and only open to the south. We feed a balanced ration of whole grain most of which is grown locally and consists largely of hard red spring wheat, peas, whole corn with lesser amounts of canola, lentils, red millet, canary seed and sunflower. I also keep the birds on the Chisholm Trail program which provides lactobacillus as well as vitamins and is mixed with the feed. I use Red C which is a race horse supplement liquid rich in trace minerals and vitamins to mix in the feed so the Chisholm Trail powder sticks. I also provide fresh water daily and twice a day in warm weather. I give acid pack 4 way in the water every other day. This is a product used in weanling pigs and it increases the level of acidity in the gut to discourage harmful bacteria. It is the same idea as giving vinegar in the water but much better. This product also enhances absorption of nutrients, such as vitamins and minerals as well as medications given at the same time. I no longer use chlorine in the water as I now understand this will actually kill the beneficial gut bacteria that are so important for good health. I also provide oyster shell and grit at all times. I deworm my birds twice a year.

I feel all this information is important so it can be better understood how different lofts, different management systems and different breeds of pigeons can be affected differently by the same illness.

Our breeding season started off quite normally. We mated up our birds in late March when the weather started to turn nice and our birds appeared strong and healthy with no signs of illness. We had introduced several new birds in late January as well as a couple in late February from several different lofts in several different breeds. These birds had all been quarantined for a month and put on doxycycline** for 10 days as a precaution. They then all appeared healthy and were introduced to our population. We had also attended one show in January and our show birds were treated the same. Doxycycline is a powerful antibiotic but it is also quite expensive. It's best not to waste it. The best approach is to measure (or estimate) how much water the birds drink at one time (say, after feeding), place this amount of water in a drinker and add the doxy at the rate of 500 to 1000 mg per 4 litres of water. Let the birds drink this amount of water and that is the treatment for one day. Fresh water is supplied for the rest of the day. This antibiotic remains for a longer period in the system than other antibiotics, so only one treatment period per day is required. There is no need to leave doxy in the drinkers all day every day. Treatment period is about 5 days. Once the 5-day period is over, immediately follow up with several days of a good avian-source probiotic to restore populations of normal intestinal bacteria. This is very important because after every treatment with oral antibiotics, the intestine is highly susceptible to infection with disease-producing bacteria (because of the antibiotic destruction of normal protective bacteria.)

Things started out good however soon problems started to appear. Nothing serious it seemed but many little things that started to ad up to big problems. First fertility was not as good as it should have been and many of our hens were not laying. At first I blamed it on the weather and the fact that so many of our breeders were young and even late hatches from the previous year. The eggs that were fertile hatched very well and the young birds appeared strong at first. However soon I started having many babies that just stopped growing at about a week of age. I discovered a higher than normal occurrence of canker ( trichomaniasis ) appearing in the throat, navel and liver so I treated for that. Others seemed weak and survived but were not developing properly. I then started to have some young birds that were crippled when it was time to leave the nest. Their legs were stiff at the hock joints but there was no apparent swelling in the joints but some did have swelling in the ball of the foot. I saw others with stress lines on the feathers and they were not growing well. A few others had deformed toes when they hatched. Even more hens that were laying stopped but otherwise appeared healthy. Fertility went down and my old birds started to do a poor job feeding the youngsters. I began to see an increase in the incidence of Herpes Virus in the weaned babies (this appears as a wet yellow crust in the throat and sinuses) . Other young birds that were weaned started to go light. Nothing felt right. I could just feel it in my loft, something was really wrong. By this time I was losing about 50% of the babies I was hatching between banding and weaning with many different symptoms. However not a single old bird appeared sick or died. It was also interesting that the Racing Homers were not nearly as affected and most of the young Homers and Rollers hatched and went on to grow and develop normally. The Jacobins, Voorburgs and Frills seemed most affected. I then suspected Paratyphoid (Salmonella) but first I wanted to know for sure. In the past I had sent birds to labs for testing but the work done was never as thorough as I wanted. This time with the help of my own local vet and Dr. Gordon Chalmers we sent birds to two different labs for testing under experienced avian vets. The results showed no Salmonella in the birds I sent. What did show up was Pigeon Circovirus. The birds I sent had virtually no immune systems with no antibodies present. These birds were vulnerable to even the most common illnesses and that is what was killing them. My Vet told me this was like AIDS in pigeons and all of the natural immunities that my birds had developed over the years were not being passed on to the young birds due to the Circovirus destroying the ability of the young birds to pick up the antibodies from the parents and develop their own immune system. Common ailments that normally would not have affected my birds were killing the young ones. I was told that because my old birds were not stressed and were very healthy they were able to remain healthy. The only thing I did notice was the poor fertility and the hens not laying (by this time close to half of my hens were not laying).

I was informed that as most of you likely know we cannot treat a virus. Dr. Chalmers said that what I must do is treat the secondary illnesses as they appear and make sure that there is no additional stress on the birds. By this time I knew of at least three other lofts with similar problems to mine. I immediately started my birds on Baytril (active ingredient is 10% enrofloxacin ) for 14 days. (Correct dosage for this strength of Baytril is 5 to 7cc [one to one and a half teaspoons] per 4 litres of water.)Within 21 days almost all of my hens were laying and the fertility started to improve dramatically. The babies from that point on were strong and losses dropped to next to nothing and I was able to salvage the rest of the breeding season. This said to me that I must have had some type of bacteria present that was sensitive to enrofloxacin. Another breeder I know treated with Doxycycline and had equally good results and yet another who had not used any medications for years used Tetracycline 250 and had good results but only after he had lost most of his young birds. What needs to be stressed here is that without medicating many of the young will die. In one case a friend left it to run its course and was only losing young birds until the birds went into a heavy moult and then it turned cold. At that point the old birds started to die quickly. By simply putting them on Tetracycline he was able to save the rest. Of course it will totally depend upon what secondary illness is affecting the birds in order to know what to treat with. The other problem is you may not have time to get every sick bird tested before you have losses. It is important to have some knowledge of your own on illnesses and treatments, a good vet or at best a knowledgeable pigeon breeder you can consult. However nothing can compare to a properly done lab test to let you know exactly what you are dealing with. I am positive that there are many breeders who have been treating the secondary illnesses not realizing the underlying problem was Circovirus. Another interesting note is that those breeders who medicate more (and I am not saying that is a good or bad thing) would likely not even know if they had Circovirus because the meds would keep the secondary illnesses in check and temporarily replace the weak immune systems.

There is still not enough known about Circovirus. It can transfer through the eggs so by stopping breeding for a few months you should be able to stop the cycle. A veterinary contact of Dr. Chalmers in Belgium reported that he is not aware of a carrier state in pigeons for Circovirus. However a copy of a 2006 scientific paper obtained by Dr. Chalmers suggested that carriers may be possible in this disease. On that basis, carriers definitely cannot be ruled out. I know that without further medication all our birds are doing fine now. Circovirus has also been commonly referred to as young bird disease. I was also informed by Dr. Chalmers that if any birds have Circovirus at the time of vaccination it may limit the effectiveness of any vaccines they get by blocking the immune responses which create antibodies. (This is why some research opinions from Scotland suggest early vaccination against paramyxovirus (PMV) - beginning at 3-4 weeks of age (in racing pigeons) in the hopes of developing some level of immunity before the circovirus invades. Waiting until the YBs are several months of age before vaccinating stands the risk of having circovirus infect these youngsters and preventing the development of good immunity to PMV.)

The following information was recently sent to me by Dr. Chalmers and is from a 2006 article (from Belgium) that contained the following final comment, quote: "Although it is possible that some birds were infected, but not excreting (virus), at weaning, it is more probable that the majority of birds became infected in the rearing loft. As there is a generally high prevalence of circovirus infection in racing pigeons, as well as a high prevalence of infection in adult birds and embryos, it is likely to be extremely difficult to produce young pigeons free of circovirus infection. However, it is possible that reductions in the amount of infectious virus to which the young pigeons are exposed may help to reduce the severity of the effects of infection. Improved hygiene within the rearing loft may be the best way to achieve this."

It is now late May of 2010 and our birds have never appeared healthier. We have gone through the entire winter not having lost or medicated a single bird. We are now well into the breeding season and everything appears normal with hens laying regularly, good fertility and hatchability. The young birds are developing normally and we have more than 100 weaned in all breeds with no problems at all. We have not introduced any new birds. Anyone with questions can feel free to contact me any time.

I am hoping that by sharing this information with all fanciers I can help someone so they can react more quickly and learn from our experience. I would like to thank Dr. Gordon Chalmers for his assistance in preparing this article.

All print appearing in Italics is information submitted by Dr. Chalmers.