At this time of year (February and March) many lofts will be experiencing respiratory infection in some of their young birds. This usually presents as a few birds with one eye becoming red and watery.
Respiratory diseases are common in pigeons. They are a major cause of poor performance and pigeon loss during the race season. Young birds under stress are most at risk of developing respiratory diseases, although healthy old birds can fall ill when exposed to respiratory diseases in the race basket. For birds to give of their best it is vital that fanciers have an understanding of respiratory infection and how to correctly manage it.

Nature of the disease  
Clinical respiratory infection in pigeons is the end result of the interplay of a number of factors, but the type of infective organisms involved and the vulnerability of the birds to infection are particularly important.
The usual organisms involved are Mycoplasma, Chlamydia and a range of bacteria (most commonly, E. coli). Whether or not these organisms actually cause disease in a pigeon, if it is exposed, essentially depends on how well the pigeon is at the time of exposure and also its age and level of immunity. Any factors that cause physiological stress can weaken the bird and make it more vulnerable to developing a respiratory infection. As a general rule, younger pigeons are more susceptible. However, in a bird that is otherwise healthy exposure to the agents that cause respiratory infection does not necessarily make it sick. Exposure to these organisms as the young pigeons grow and develop, rather than cause disease, stimulates immunity to form in a bird that is otherwise healthy.
Predisposing stress factors that can make pigeons more vulnerable to respiratory infection can take the form of:
1. Environmental triggers; e.g. dampness, overcrowding, low hygiene
2. Management triggers; e.g. poor feeding, excessive tossing, or
3. Concurrent disease, in particular parasitism. This includes wet canker. The combination of either worms or elevated trichomonad levels and respiratory disease is very common.
The fancier must establish a healthy loft environment; otherwise respiratory disease will continually recur, despite medication. A good example here is a fancier who was recently in our clinic. He had a group of young birds that had dropped about three flights; that is, were about ten weeks old. A few kept getting ‘eye colds’. He would treat them and they would become well but within two weeks there would be more birds with the same problem. In a 2m x 2m section, he had 40 youngsters, and the humidity reading (from a hygrometer placed on the wall of the loft overnight) was 85%. Reducing the number of birds to 25 per section, and installing an additional vent high on the back wall improved ventilation and reduced humidity. The birds were again treated, but this time the problem did not return.
This article discusses respiratory infection associated with Chlamydia.

Chlamydia are one of the 2 common organisms that cause respiratory infections in pigeons. Chlamydia are an unusual group of organisms. They are what are called intracellular bacteria , ie they actually live inside the tissues of animals. Being bacteria they are antibiotic responsive. As a group, they can cause disease in a variety of animals. One species causes disease in koalas while another causes a venereal disease in humans. The species that infects pigeons is called Chlamydia psittaci. It essentially has two lifecycle stages – a reticulate body and an elementary body. The elementary body can survive in the environment. Pigeons become infected through contact with the elementary body. The elementary body typically attaches itself to the superficial lining cells of the eyelid, throat or upper respiratory tract. The elementary body then penetrates the cell membrane into the cell and becomes a reticulate body. The reticulate body then replicates itself until there are many reticulate bodies in the cell. As the reticulate bodies increase in number, they rupture into adjacent cells causing cell destruction and an advancing wall of inflammation. Alternatively, they rupture back out on to the surface of the cell, once again becoming elementary bodies and further contaminating the environment. Infected birds with active disease shed large numbers of these infective elementary bodies in their saliva, tears, respiratory discharges and droppings contaminating the loft. Poor loft hygiene enables a build-up of the organism in the loft. Combine this with birds that are a bit run-down and a disease outbreak occurs. However in well managed lofts disease is rare. In fact ,as mentioned above, it is thought that low grade exposure to these  Chlamydia elementary bodies may not cause disease but, rather, trigger the development of an immune response in a pigeon that enables it to be more resistant to the disease. The typical situation in most racing lofts is that Chlamydia tends to cycle through the birds. Growing youngsters are passively exposed to the organism from other birds in the loft and their parents. Often this doesn’t cause disease. Most birds, by the time they are six months old, have had multiple low grade exposures and have developed a significant immunity. Disease occurs if the youngsters become ‘run down’ due to stress factors and are therefore unable to mount an immune response or, alternatively, their level of immunity is challenged by a particularly high exposure to the organism. An antibiotic called doxycycline is very effective at treating Chlamydia. If a pigeon is given a 45-day course it has a 98% chance of clearing Chlamydia totally from its system. One would think that it would make sense to treat all the birds for 45 days, eradicating the disease and then not worry about it in the future. The difficulty with this is that if we were to eradicate Chlamydia, it is known that any immunity that the pigeons have would gradually disappear. This would mean that if the birds were subsequently re-exposed, they would be a very vulnerable population and potentially severe disease could occur. Once racing starts, exposure to Chlamydia in the race units is virtually guaranteed. Although drugs can be used to treat Chlamydia again and again if it keeps reappearing in returning race birds this is obviously not desirable. The factor that principally protects the birds in the race unit is the immunity that they are able to form if they are well cared for in the loft while young and maturing . Chlamydia is therefore managed by caring for the birds well ( so that they can mount a good immune response),  by allowing a controlled exposure to the disease  ( to build up a strong immunity)  through the maintenance of loft hygiene and by using medication if required during development in a way that keeps the birds healthy but still allows some exposure to the disease. How is this done?

Post-weaning management
In the post-weaning time Chlamydia cycles through the developing young birds. Some youngsters may have passive immunity acquired through the egg and from their parents in the crop milk. Further exposure in the young bird loft builds on this immunity. Some youngsters take longer to form a protective immunity than others, and these can show symptoms of clinical Chlamydia infection. If the birds are well otherwise, these symptoms are often described as a “one eye cold”. Symptoms are often mild and may include a dirty cere, sneezing, nasal discharge, a partially closed light sensitive eye, inflamed red eyelids, and also tears overflowing the eyelids and becoming air dried on the feathers around the eye. If the number of birds affected is low and the symptoms are mild, often no treatment is provided. With ongoing good care it is likely that the birds will fix themselves and will develop a stronger natural immunity this way. If the symptoms in an individual bird become more severe, particularly if the bird’s development is starting to be compromised, treatment should be provided. The usual treatment is doxycycline 10–25mg per pigeon once daily. If less than 5–10% of birds are affected, it is best to just treat these birds individually. There is no need to separate them from the rest as all birds are likely to have the organism in them. Also young birds tend to recover better if left with the flock in a familiar loft. If more than 10% of birds develop symptoms then a flock treatment should be given. The usual treatment is doxycycline in the water. However, if 10% or more are developing symptoms, this tells you that this group of young pigeons is having trouble developing their natural immunity. And if they are having trouble developing a natural immunity this means that something is stressing them. A review of their management, loft environment and a check for any other (particularly Circo virus and parasitic) disease should be done. In young birds the underlying stress is often overcrowding. In Victoria, Australia, January to May are the respiratory months. Most lofts contain large numbers of young birds having just had the stress of weaning and now having the stress of moulting, coupled with young bird training and establishing themselves in the loft. It is a time of high humidity and fluctuating temperature, conditions that favour respiratory disease. Between 1 December and 1 March (the usual time that the last youngsters are weaned in many lofts in Australia), fanciers must monitor the youngsters, in particular for signs of “one-eye cold”, dirty wattles or sneezing. However, green watery droppings, failure to thrive, shortness of breath and a reluctance to fly may also be indicative of the problem. After 1 March in Australia, as the youngsters get older, fanciers look for signs of poor loft flying, excessive panting after training, and sneezing within the loft. Even in the healthiest lofts, there can be occasional outbreaks of respiratory diseases. It is important to recognise that more than three sneezes within five minutes from 100 birds is a significant indicator of early respiratory disease. One would expect two to three sneezing outbreaks between January and May, even in the best managed loft.

 Pre-race management
As racing approaches, the birds have been given as long as possible to develop their natural immunity. It is important, however, that there is no active Chlamydial respiratory infection in the birds when racing starts. The can lead to poor race results and potentially disastrous returns. Chlamydia tests can be done by your veterinarian to see if the disease is still active and if the birds have formed a good immunity. The usual tests available are the Chlamydia immunocomb test, or Chlamydia PCR test.
A team should only be treated for Chlamydial respiratory infection before racing if it fits into one of the following categories:
1. If testing shows that the disease is still active in the birds, even if they look normal.
2. If Chlamydial respiratory infection was a problem during the early part of the racing season the previous year and the loft parameters have not changed (i.e. same loft design, same genetics, etc.)
3. If there was a significant amount of respiratory disease in the post-weaning time.
4. If the birds have a current clinical respiratory infection.
If the loft fits into one of the above categories then it is usual to treat the birds for 7–20 days with doxycycline, finishing two to three weeks before racing starts. Just how long an individual team is treated depends on the severity of the problem and the response to treatment. If they do not fulfil one of these criteria then no treatment is required.
I have had several fanciers tell me that they have been advised by a vet that the best thing to do prior to racing is treat their birds regardless with doxycycline. They were told that if it makes their birds sick then they don’t need it. If it does not make them sick then they must have Chlamydia and a long course of the drug should be given. I find this advice hard to believe as coming from a vet . It would see potentially tens of thousands of pigeons given antibiotics they don’t need in an absolute bogus way of assessing Chlamydia status. Such a suggestion is nonsense.

Management during racing
Ongoing exposure to Chlamydia occurs during the racing season. The natural immunity the birds have formed through development should be high enough to protect them; however, because of the stress associated with racing and potentially high exposure to the organism it may not be. Fanciers should monitor their birds closely for symptoms and have their birds regularly checked by an avian vet. If the birds become unwell or race performance is compromised due to Chlamydia, then the team is treated as a single unit and a flock treatment of doxycycline is given. Birds return to health fairly quickly, but not to race form. Sometimes a race needs to be missed and then the level of work gradually increased as the birds regain their health and fitness. If Chlamydia is diagnosed through the racing season, what should the fancier do?
1. Conduct a health profile
– i.e. examination of the saliva and droppings and sometimes other tests as suggested by your veterinarian to assess any concurrent disease that may need treatment. Provide general ongoing good care to ensure a good response to medication.
2. Return to exercise gradually. Always, with respiratory infection, there is an extended convalescence usually of 1–3 weeks. The birds must be given time to recover their fitness once medication has cleared the infection. They should not be forced to fly around the loft and once it is apparent that their vigour for flying has returned, short tosses only should be given (less than ½ – 1 hour) initially. Observe the birds closely for signs of breathlessness on landing from these tosses and only when they are handling these well should longer tosses be given. When managing tosses of 1–1½ hours well, it is usually safe to resume racing. In well-managed lofts with no other health problems, response to treatment can, however, be dramatic and I have had an interesting experience where two fliers both diagnosed with respiratory infection in their teams succeeded in gaining 1st and 2nd Federation (3000 birds) in an all-day 800km race 3 weeks after treatment.
  3. Give good food, good care and an appropriate multivitamin supplement to speed recovery.
 4. Give appropriate medication. The choice of drug is often dependent on the involvement of secondary organisms, but usually the antibiotics doxycycline and tylosin are given together, or a blend of doxycycline, tylosin and spiramycin. An initial course usually of 3–10 days is given, depending on the severity of the infection and response to treatment.

Symptoms of Chlamydial Respiratory Infection
In young birds, symptoms are usually confined to the upper respiratory tract and the most common signs observed are a dirty cere, nasal discharge and a red watery eye. In some birds, however, the organism can infect various internal organs including the liver and spleen and also deeper parts of the respiratory tract, particularly the air sacs. These birds may just be quiet, be reluctant to fly, lose weight and develop a green mucoid dropping. Birds with inflamed air sacs often become breathless after moderate exercise and are sometimes forced to land wherever they are. This may include buildings or trees near the loft. By the start of racing the birds are older, their natural immunity is higher and their response to disease is different. The signs observed are modified by these factors and are often very subtle. Older birds with respiratory infection have lost their zest for life, and this is reflected in their race results. Birds that are reluctant to fly, quiet in the loft and with dry feathers (no bloom) are suggestive of respiratory infection. Irritation to the upper airway usually shows itself as an increased rate of sneezing. Sneezing (more than three times in five minutes from 100 birds), scratching at the nose, yawning, repeated exaggerated swallowing, stretching the neck and wiping the nose on the wing butt all indicate irritation of the upper airways. On opening the beak, inflamed tonsils may be seen, a thick white mucus may be extending into the throat from the windpipe or from the ‘slot ‘in the roof of the mouth, which may be closed due to swollen edges, the top of the windpipe may be red and inflamed, the beak at the nostril opening may be wet, the cere may be slightly discoloured or there may be a slightly mucous component to the birds’ grunt. The lining of the throat or the muscles may be bluish. Chronically-infected birds show delayed recovery after a race and will develop green droppings after stress because of damage to the liver. Sometimes the only symptoms in race birds, however, are poor performance and increased losses. Birds with inflamed sinuses tend to cope particularly poorly on cold head-wind days. Presumably the cold winds buffeting the already inflamed sensitive sinuses across the face act a bit like an ‘ice cream freeze’ making the going hard. Chlamydia can be carried throughout the body in the bloodstream and in birds of any age severe systemic disease can occur. Here birds become severely unwell and, without prompt correct treatment, some will die. In some birds the gonads will be damaged. This can lead to decreased fertility in both cocks and hens. Hens with a Chlamydial infection of the ovary often have late or irregular ovulations or no ovulations at all. If an egg is produced, sometimes Chlamydia can be incorporated in the egg, where it can either kill the developing embryo or lead to the hatching of a weakened chick.

It is important not to confuse symptoms with a diagnosis. Many pigeon diseases have similar symptoms. The symptoms described earlier are all suggestive of the problem, but an accurate diagnosis can only be reached through testing. The tests used today provide a speed and accuracy not available to vets or fanciers in the past. The tests in common use are:
1. The Chlamydia Immunocomb test – a serology test, and therefore can only be done on whole blood. A drop of blood is collected. The veterinary technician then follows a series of steps. The test detects the presence of a particular immunoglobulin, IgG, in the blood, formed in response to Chlamydia exposure. Results are available in 4 hours.
2. Chlamydia PCR test – detects the presence of Chlamydial DNA. PCR tests are available for Chlamydia and also Mycoplasma. The test is usually done on a swab collected from the throat, slot and eye. Results are usually available in 2–4 days. A very accurate test.

Worldwide the medication of choice for Chlamydia is doxycycline ( for example, Doxyvet™). Some other antibiotics do have an affect against Chlamydia, notably enrofloxacin (Baytril™) but are not as effective as doxycycline. Baytril™ stops Chlamydia replicating, but fails to clear it from the pigeon’s system. It therefore reduces clinical symptoms and treated birds appear to get better, but relapses are common. Doxycycline actually stops the organism replicating and clears it from the pigeon’s system. In preparations made for racing pigeons, doxycycline is often combined with tylosin (commonly used to treat Mycoplasma); for example, Doxy-T™, and sometimes also spiramycin (also called suanovil); for example, Triple Vet™, that treats many of the bacteria involved with respiratory infection. These combinations aim at providing a broader respiratory treatment targeting all of the likely organisms involved. Doxycycline absorption from the bowel is compromised by concurrent use of calcium-based supplements and so it is best to remove grit, pink minerals and picking stones during treatment. Also, doxycycline is absorbed slightly better from the bowel in a weakly acidic environment. Adding citric acid (3g/6L water) during doxycycline administration is recommended by some vets. Drinkers made from non-glazed pottery or galvanised metal can also adversely affect doxycycline action. Drinkers should also be kept out of direct sunlight as UV light and heat can inactivate the antibiotic. Contamination with organic material such as droppings can also denature the doxycycline.


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