Nature of the disease
The disease canker is caused by a protozoan Trichomonas columbae. This is a microscopic single-celled organism. It infects the digestive tract of pigeons, in particular the throat and crop, and can also involve associated areas such as the bile duct. The organism can stimulate an inflammatory reaction in these areas leading to deep ulceration and the accumulation of thick yellow inflammatory debris. As lesions enlarge they can occlude the throat and trachea, making swallowing and breathing difficult. The organism also releases toxins into the bird’s system that can damage the liver and kidneys.
Common symptoms include a general failure to thrive, difficulty swallowing, vomiting, regurgitation, saliva at the beak margins, weight loss, difficulty breathing, visible distension of the throat, yellow material in the mouth and high mortality, particularly in young birds. The organism is fragile in the environment, only surviving for a few minutes once outside the bird. This helps with control of the disease, and means that the birds cannot become infected from the loft or immediate environment as happens with other diseases such as worms and paratyphoid. The organism (Trichomonad) requires intimate contact between birds to be spread and is usually transmitted by saliva or pigeon milk.
Saliva contaminates food and water. As a pigeon drinks, the organism swims away from its beak and, when another pigeon comes to drink, it not only drinks the water but also the Trichomonads there. When a pigeon sorts through grain, each dropped grain may be contaminated with a small amount of saliva. In this way, the disease can also be spread through a feed hopper. Adult birds ‘billing’ can transmit the organism, as do parents when feeding their nestlings.
After exposure to canker organisms, a variety of outcomes can occur. Some birds may develop severe disease. Others may become infected but show no symptoms. Infected birds may or may not subsequently clear the organism from their system. The outcome of exposure is affected by many factors such as the bird’s age, general health and whether or not it has been exposed before and has developed some immunity. Often the appearance of the lesion is highly suggestive of canker. The diagnosis is confirmed by microscopic examination of a saliva sample or crop aspirate (termed a crop flush).
Control of canker during the breeding season
Correct use of medication is important during the breeding season so that the level of natural immunity in the weaned youngster is as high as possible. Because the severity of the disease varies in different lofts, there is no single blanket program that is best for all lofts. There is no drug that, by itself, will cure canker in a loft. It is a matter of using medication correctly so that the birds can establish a strong natural immunity to the disease. It is this natural immunity that, in the longer term, protects them from the disease.
What causes canker to appear during the breeding season?
In health, every time the feeding stock bird feeds its youngsters, it passes on some of its own Trichomonads to them. This gives the youngsters a controlled gradual exposure to the organism, which in turn allows them to establish their own natural immunity. Clinical disease appears in the babies when the stock birds shed an infective dose of canker organisms to their chicks. Just what constitutes an infective dose depends on the outright number of canker organisms, the ability of that canker strain to cause disease and also the general health of the youngsters.
Increased rates of Trichomonad shedding by the stock birds will occur if:
1. the stock birds are stressed for any reason – Anything that stresses the stock bird will lead to an increased rate of Trichomonad shedding. This includes such things as a poorly designed loft, poor management practices, incorrect feeding, and other concurrent diseases.
2. the stock birds’ natural immunity is not high – Stock birds are likely to shed higher numbers more readily when breeding if their own natural immunity to the strains present in the loft is not as yet solid. This can occur if new stock birds carrying different trichomonad strains have been introduced to the loft during the non-breeding time. All birds carry some immunity to the resident Trichomonad strains in their loft. When birds from different lofts mix, they exchange their Trichomonad strains.
Adult stock birds during the non-breeding season are not stressed and so exposure to any new strains brought in by introduced birds is unlikely to lead to disease. They are not moulting, not breeding, and have plenty to eat, and therefore no sign of canker occurs. However, when paired, if their natural immunity to the new different strains is not solid, the stress of breeding will cause them to ‘break down’ and shed larger numbers of Trichomonads. In the same way, the introduced birds need to establish immunity to their new loft’s resident strains.
This is why canker is more of a problem in lofts that are still establishing with birds coming from a variety of other lofts. As the years roll by, fewer new birds are introduced and so the chance of new Trichomonad strains getting into the loft decreases. The birds’ immunity to resident strains becomes solid and the effect of the disease is less marked.
Many fanciers are frustrated when canker appears in the stock loft. With excellent care in a good loft, they wonder just how it is that the disease can occur. Certainly they are on the right track with this approach, because in a good loft under good care, it is less likely that the stock birds will shed large numbers of Trichomonads. However, some strains are so capable of causing disease that problems will arise no matter how well the birds are cared for.
How to manage an outbreak of canker during the breeding season
When canker does appear during breeding, its management is two-fold. It is a matter of:
1. Treating the sick youngsters – In lofts with a canker problem, all youngsters should be checked daily. If a sick youngster is noticed it can be successfully treated, and such youngsters can go on to be successful racers. A variety of medications are available. Your avian vet can advise you here. A common and effective treatment is carnidazole, available in a 10mg tablet called Spartrix. The dose of Spartrix is one tablet per adult bird. Estimate how big the youngster is compared to the adult and give it this proportion of the tablet once daily until well. Usually, one to four doses are required. It is often good to also medicate both the nest mate and parents for two days. Individual pairs that breed youngsters with canker are best mated to different birds for subsequent rounds.
At the same time, it is important to:
2. Decrease the number of fresh cases – This is done by medicating the parents so that the number of Trichomonads they are shedding is reduced. A variety of medications are available here. A common one is ronidazole (e.g. ″Turbosole" 3g/2L of drinking water) mixed fresh daily and provided for 4–5 days. This treatment does not treat the current youngsters that are unwell, but reducing the number of Trichomonads shed by the parents decreases the number of further chicks that will become clinically unwell. The aim of treatment is to reduce but not eliminate the number of Trichomonads that the parents are shedding.
The developing youngsters need some exposure to develop their own natural immunity to the disease. Treating too often means that, although no clinical canker will develop in the youngsters, they do not get the exposure they need to develop their own immunity and will therefore be vulnerable to canker as older birds. The usual indication for a flock treatment is more than 5–10% of nestlings developing the disease. Repeat courses are given when required. One needs to give sufficient courses to limit the number of new youngsters with the disease, but at the same time to avoid overuse of the drug so that the developing youngster is still getting an ongoing exposure to the organism. It is a matter of working between these two extremes.
The important thing always to remember with canker during the breeding season, is that the disease can never be controlled through medication alone. It is the development of a strong natural immunity that protects the birds in the longer term. It is important that medication is used to keep the birds well, but used in such a way as not to interfere with the development of this immunity.
An interesting feature regarding the transmission of canker from carrier parents to their nestlings is that it has been shown that the Trichomonads are able to detect the elevated levels of the hormone prolactin in the parents’ bloodstream associated with the development of crop milk. As prolactin levels rise, Trichomonad numbers in the crop also elevate, leading to more organisms being available to be passed to the growing nestlings. This, presumably, is an adaptation of the Trichomonad organism to ensure that it is passed to the next generation.
Canker organisms magnified 4000x
Preventative programs for the breeding season
In the stock loft that had canker last season
Treat all stock birds for five to seven days before pairing, and consider a further treatment just before hatching. Frequency of subsequent treatment depends on the severity of the problem and the control achieved. Coinciding a treatment period with the time of hatching, when Trichomonad shedding is highest, can be beneficial. If canker is still a problem in certain pairs, try to medicate only these pairs. This can be achieved by breeding from them in individual runs and only medicating their water with Turbosole for three to four days as required or, alternatively, leaving them in the loft and just treating them with Spartrix tablets for two days when needed. Splitting the pair and re-mating each to other birds for the next round may help.
Stock birds can be crop flushed before pairing to identify those birds carrying large numbers of Trichomonads. These birds are not only more likely to shed large numbers of Trichomonads more readily once paired, but also to pass on their genetic susceptibility to canker. In the longer term, it is sometimes best if these birds, when identified, are eliminated. The problem is that they may, in fact, be the winners, and here lies the challenge for the fancier – to breed birds less susceptible to the disease that are also winners.
In the stock loft that had no canker last season
No treatment is required. If there was no problem with canker in last year’s nestlings, then it is best not to medicate for canker. Any medication will stop the paired bird shedding Trichomonads, and therefore interrupt the ongoing exposure of the growing youngster to the organism. This leads to a lower natural immunity and may in fact create a vulnerability to the disease in the post-weaning period.
In the stock loft that had no canker last season but to which new stock birds have been introduced
As discussed earlier, all birds carry in their systems the resident Trichomonad strains of the loft, and usually have a strong natural immunity to them. A newly-introduced stock bird brings these strains with it. These strains may not have been encountered by your own birds and the new birds may not have encountered yours. Both groups of birds, through mixing in the one loft will, with time, become immune to each other’s strains. If introduced in the non-breeding time, when the stock birds are not under any stress (not moulting and in a good loft with plenty to eat) no clinical disease will be seen.
However, with the stress of breeding, any immunity already developed will be put to the test. If immunity is not solid at the time of breeding, excessive Trichomonads will be shed and the youngsters may develop canker. For this reason, new birds, especially if introduced immediately before pairing, should ideally be mated in individual runs and the youngsters monitored. Once hatching begins, check the chicks every one to two days. If unwell chicks appear, treat them individually (for example, with "Spartrix") and be prepared to give flock treatments (for example, with "Turbosole") if more than 5–10% of youngsters develop disease, as discussed earlier.
Control at weaning
In lofts with a canker problem, all youngsters can be treated with "Turbosole" for three to five days at weaning, to avoid any check in their development through this stressful time. In the longer term, however, the important thing during this time is that, ideally, only youngsters with the disease should be treated so as not to interfere with the developing natural immunity of the flock as a whole. Affected birds should be separated and treated with either one-quarter of a "Flagyl" tablet (metronidazole 200mg) or one whole "Spartrix" tablet once daily until well. This usually takes one to three days. Alternatively, the unwell youngsters’ water can be medicated with "Turbosole" (½ teaspoon [i.e. 1.5g] to one litre of water).
It is important, however, to ensure that any unwell youngster is still able to drink. Turbosole can also be mixed into a paste and the youngster’s throat painted with this using a cotton bud. The group of youngsters, as a whole, should only be treated if more than 5–10% of youngsters are showing signs, usually with Turbosole for three to five days. However, in this situation it is best to seek veterinary advice as other concurrent health problems may be involved. Once the youngsters are weaned and settled in the loft they should be monitored for canker. If individual birds develop clinical canker they are treated as above. If more than 5–10% of birds develop clinical disease then a flock treatment is given.
Most youngsters at weaning will have some Trichomonads in their throat, but will not develop clinical disease. Detecting Trichomonads in a crop flush in an otherwise well youngster is not an indication for treatment. As the birds continue to mature, this low-grade ongoing exposure stimulates the development of their immunity to canker. In many good lofts, most birds, by the time they have finished moulting, have a good natural immunity to canker and crop flushes will show that there are no Trichomonads present.
Control during the pre-race time
In the last four to six weeks before racing, a selection of birds from the race team should have crop flushes done to make sure that they are not still carrying Trichomonads (that is, have wet canker). In many lofts the birds will have developed a good immunity and no trichomonads will be found. If any Trichomonads are found, the birds will need to be treated. We want to start the season with healthy birds. Having given the birds as long a time as possible to develop immunity, any persistent infection is cleared with a medication course, such as ronidazole for five to seven days.
Control during the race season
If canker was a problem during the breeding season, this tells us that the birds have the potential to have trichomonad flare-ups in response to stress and that canker has the potential to be a problem during racing. However, through good management and the correct use of medication, it is hoped that most birds have developed a reasonably strong natural immunity by the start of the race season. The stress of racing will put any immunity that the birds have formed to the test.
Depending on what stresses the birds are under, and also trichomonad exposure in the race baskets, trichomonad levels will rise and fall. When high, they have a typical parasitic effect, weakening the bird, in the process creating a vulnerability to secondary infection (particularly respiratory infection) and compromising race performance. They also produce a toxin that makes the birds feel unwell. Birds with elevated trichomonad levels are said to have ‘wet canker’. Signs of infection can be subtle and quite varied. Typical signs that would alert the fancier to its possible presence include:
1. ‘Penguin’ posture – Associated with proventricular (glandular stomach) and crop pain. Birds will lean back on their tails and gulp. Noticed particularly after eating and drinking.
2. ‘Dry feather’ – Due to lack of down feather drop and bloom production.
3. ‘Leady’ feel – Affected birds will not come into condition and feel heavy in the hand.
4. Wet droppings – Inflammation in the digestive tract creates a thirst, leading to elevated water intake and urine production. This produces a clear watery rim around the dropping.
5. Green droppings – Due to digestive tract irritation and, in some birds, decreased food intake.
6. Inflammation in the throat – Tonsillitis and increased clear to grey bubbly mucus.
7. Interference with crop function – Delayed crop emptying and sometimes vomiting.
8. Increased food consumption by team as a whole – Due to the Trichomonads’ parasitic effect, the birds feel overly hungry.
9. Dry yellow canker – In birds of any age, this tells you that many other birds have elevated Trichomonad levels, which have not yet passed the threshold for yellow material to form.
10. Indirect signs – Poor loft flying, poor tossing, respiratory problems that respond poorly to medication or quickly relapse, a dramatic improvement in the birds’ general vigour in response to anti-canker medication are all suggestive.
Definitive diagnosis, however, depends on microscopic examination of a crop flush. Microscopic changes that are suggestive of the problem also develop in the droppings. These changes are associated with the stress of the disease and include elevated E. coli and yeast levels. These changes, however, do not occur in all birds. For fanciers who live at a distance from a veterinarian, “Trich Pouches” or Avian Lab’s Quick tests for trichomoniasis can be used (see “Diagnosis at the Distance”).
During the racing season birds are continually being exposed to canker organisms in the race baskets. Exposure, however, doesn’t necessarily equal infection. Birds that have a strong natural immunity and are being well cared for in their home loft are more likely to mount a good immune response and resist infection. If birds do become infected, however, this dramatically compromises their ability to compete successfully. Wet canker is the most common health cause of good pigeons failing to realise their full potential during racing. Wet canker is more likely to become established in the racing loft if:
1. There has been incorrect use (usually overuse) of medication during the breeding, weaning and pre-race times allowing insufficient exposure to the organism.
2. There are flaws in the loft management or environment that weaken the birds making them more vulnerable to infection – most commonly overtraining and incorrect feeding.
3. There is exposure to particularly pathogenic (disease-causing) strains of Trichomonad in the race basket. One of the nastiest Trichomonad strains known is a strain called the Barnes-Jones strain. In one experiment, a single Trichomonad organism of this strain was given to 20 adult pigeons. Over half died within a week, of canker.
The strains of canker that cause wet canker in race units are now ubiquitous and it is important for ongoing success either to have monitoring crop flushes done to check for the organisms’ presence through racing, ideally every two to three weeks or, if this is not possible or practical, to treat the birds periodically for wet canker through the racing season so that the disease cannot become established and interfere with the team’s performance as a whole. In most lofts, once racing is progressing, if the team hasn’t been treated for more than three weeks we would expect to find some birds with canker in more than 90% of teams.
The usual treatment is ronidazole for three to four days every third week. Something as simple as this is adequate to keep the problem under control in the majority of lofts. If possible, it is a good idea to have regular monitoring crop flushes done to make sure that the drug being used is still effective. Often it can be good to use a different drug periodically to head off the development of any Trichomonad resistance.
A very successful fancier that I dealt with in Europe several years ago had his veterinarian come to the loft every Tuesday. He had multiple race sections, each containing a number of widowhood cocks. The vet would crop flush one or two birds from each section. Those sections that contained birds that were positive would be treated and no birds from that section raced that weekend. The sections that were clear would be considered for racing.
In Australia, a common medication protocol is to give the ronidazole-based "Turbosole" for three to four days every third week; every fourth treatment dimetridazole ("Emtril") is used as an alternative to prevent ronidazole-resistant strains becoming established in the loft. Ronidazole has the big advantage of being very safe and quickly excreted from the pigeon’s body. If medication stops two days before basketing then the birds go to the race as drug-free birds. Dimetridazole has the disadvantage of a narrow safety margin, and therefore needs to be accurately dosed. It is, however, the only other water-soluble canker drug available for flock treatment in Australia. In smaller teams, dosing with tablets such as "Spartrix", "Flagyl" or "Ronsec" becomes a practical way of giving an alternate medication.
It is worth noting that these periodic treatments to control wet canker through the race season in race teams are best given on days when the whole team is there. Some fanciers treat on the day of the race or on the following day when there may be stragglers coming through. These stragglers may be late because they have wet canker and yet will have less access to medicated water the later they are, particularly if the loft is treated for a specific time. I think it is much better, in most lofts, to use Monday, Tuesday and possibly Wednesday as treatment days for a Thursday or Friday basketing. On these days all birds are in the loft and are most likely to receive a therapeutic dose. If a new strain of Trichomonad is introduced with a returning race bird then treating every few weeks is sufficient to prevent it becoming established and can affect the form of the team as a whole.
It is naïve of certain fanciers to think that for some reason their birds will naturally be resistant to wet canker. Fanciers who don’t treat and don’t monitor cannot expect to be as consistently successful as they might otherwise be. Some fanciers may think it is overkill to test birds every three weeks during racing. I would strongly encourage them to do this at least for one to two years. What we often find is that the interval between treatments and the length of treatment that effectively keeps the trichomonad number low or zero, becomes predictable for that loft. Provided the loft parameters (the genetic make-up of the birds, the loft’s location, management practices, loft design and loft environment) remain unaltered then a program that has proved successful in the past can be successfully reapplied year after year.
What we are aiming for is the lowest amount of medication that will keep the problem under control. Testing will identify this and once the control protocol for that loft has been developed it can continue to be used. Occasionally there can be a ‘spike’ after an unusual event (for example, a particularly hard toss during cold weather) and an unusual Trichomonad flare-up can occur. Interestingly, however, we do tend to find that as the season progresses, the need for medication declines. As the season progresses the birds are getting older, their levels of fitness and natural immunity rise and, in particular, in Victoria, the weather becomes warmer.
Other sites of canker
As fanciers would be aware, most canker lesions are found in the bird’s throat. However, canker can affect a variety of other sites. Navel Canker
If pigeon milk is spilt into the nest bowl and this, in turn, contaminates a nestling’s navel that has not fully healed, a canker nodule can develop on the navel. Treat the nestling with the correct dose of "Spartrix " daily (usually for one to four days). Antiseptics (such as Betadine) can be applied to the navel daily until the area has dried. After several days, the nodule can be ‘popped’ like a scab and separated from underlying healthy tissue.
The condition must be caught early for treatment to be successful and for the youngster to be of value racing. The condition is more likely to occur when nest conditions are poor, leading to delayed navel healing, and is therefore often associated with ‘wet nests’ and with inappropriate nesting material. The condition is also more likely to occur if the parents are shedding large numbers of Trichomonads. A suggested course of treatment is to:
• Treat youngster and both parents daily with "Spartrix"
• Dab navel daily with "Betadine"
• Clean nest
• Treat parents for ‘wet nest’ if appropriate (pink minerals and probiotics)
• Improve nest conditions
Sour crop
In pigeons with sour crop, at least 90% have an internal canker nodule located at the base of the crop or within the glandular stomach (proventriculus). As the nodule increases in size, it squashes the windpipe, making breathing difficult and blocking the crop outlet. This interferes with crop emptying, leading to bacterial infection of the crop and secondary starvation and dehydration due to the crop contents not being able to pass into the bird’s system.
Usually by the time the bird is noticed to be unwell, the condition, frustratingly, has passed the point where it will respond to treatment. Deaths often occur due to the nodule growing through the stomach wall, leading to stomach contents leaking into the chest. Alternatively, the nodule can damage the heart or large blood vessels within the chest, causing sudden and severe bleeding. Such birds are often found dead on the floor with blood coming from the mouth. It is always worth attempting to treat valuable birds and I suggest:
• manually emptying the crop
• giving electrolytes in water; e.g. "Electrolyte P180"
• treating the bird with 0.4ml "Baytril" 2.5% once daily
• treating the bird with 1 tablet of "Spartrix" or ¼ Flagyl tablet or 0.5ml "Flagyl" syrup, once daily
• separating the unwell bird from loft mates
Cloacal Canker
The cloaca is an organ inside the pigeon’s vent. It contains several chambers. Within its dorsal wall is a gland called the Bursa of Fabricius. This gland is an important part of the youngster’s immune system. It shrivels up and disappears during puberty. If pigeon milk containing trichomonads contaminates the nest bowl, the trichomonads can cause a trichomonad abscess to develop in this gland.
Affected birds are usually noticed to be a bit quiet or their growth is slightly retarded compared to others of their age. On examination of the vent, a firm lump can be felt in the skin above it. Sometimes these lumps do not become apparent until the post-weaning period. Affected birds should be treated daily with either "Spartrix" or "Flagyl", usually for three to four days, by which time the abscess has usually localised and can be expressed by gentle but firm pressure, through the vent.
Canker nodule in the throat or crop
Older youngsters or mature stock birds with a reasonably strong natural immunity will often try to localise a canker infection, leading to abscess formation. If in the throat, these abscesses can usually be seen or, if in the crop wall, can usually be felt as firm mobile lumps ranging in size from 0.5cm to 4cm in diameter. Affected birds are treated daily with Spartrix or Flagyl tablets. Once localised (usually one to four days) throat lesions can usually be teased free with a cotton bud, or crop lesions pinched free into the crop. Occasionally, surgical removal is necessary. Premature attempts at removal usually result in excessive bleeding.
Internal Canker
Canker can infect internal sites associated with the digestive tract, notably the bile duct, which drains bile from the liver into the bowel. Birds with an internal canker infection usually display non-specific signs of illness, including weight loss, lethargy, reluctance to eat and green diarrhoea. Frustratingly, the final diagnosis is often made at autopsy. For valuable birds, blood tests x-rays or an exploratory laparotomy under anesthetic may be necessary to reach a diagnosis. In lofts with a canker problem, it is usually best to include a daily "Spartrix" or "Flagyl" tablet in the treatment regime of an unwell breeding bird until shown that this is the problem, as a delay in the start of treatment dramatically reduces the chance of the bird recovering.
Sinus Canker
Sometimes canker organisms can invade the sinuses through the ‘slot’ (choana) in the roof of the mouth and form a canker abscess here. The birds present with a firm swelling across the forehead between the base of the cere and the eyes. Canker medication is given for four to five days to kill the active infection. After this, lancing the area by making an incision in the skin over the most prominent area of the abscess enables the canker abscess to be expressed. Once the abscess is removed, it is best to continue with canker medication for several days. Healing is usually uneventful.
Other sites
It is important not to confuse infection in other parts of the body with canker. Trichomonads, partially because of their fragility, can only infect the digestive tract and associated structures. Pigeons are very restricted in their response to infection. Their white blood cells lack many of the enzymes (called lysosomes) that are normally found in mammals, and therefore cannot produce pus. For this reason, no matter where the site of infection, the resultant reaction often looks like a canker infection. Bacterial (or other) infections of the skin, feet and eye, etc., for this reason are often confused with canker because of their appearance.
Left-A pigeon with a canker nodule in its sinus before surgery. Right-The same pigeon after surgery
Available medications
Any one of a group of medications called nitro-imidazoles is effective against Trichomonads. There are five commonly in use:
1. Dimetradazole – The common brand name is "Emtryl", available as a water-soluble powder. Dimetradazole was the first nitro-imidazole available and is still an effective drug, although Trichomonad resistance to it in some areas is a problem, because it has been used the longest. It must be used with care as it has a narrow safety margin. Overdose leads to a reversible loss of balance and coordination and, in high doses, death. The medication can interfere with sperm production in cocks, leading to a temporary infertility, and so is not recommended for use during breeding. The usual dose is 1 teaspoon (3g) to 4½–8 litres of water. Lower dose rates should be used in stock birds feeding youngsters and during hot weather, when water intake increases and evaporation occurs from drinkers, increasing the concentration of the medication.
2. Carnidazole – The common brand name is "Spartrix". It is only available in tablet form. It has a wide safety margin and is very useful for individual bird dosing, particularly for youngsters in the nest. The dose is one 10mg tablet daily to an adult pigeon.
3. Metronidazole – The common brand name is "Flagyl". This is available as a water-soluble syrup and as tablets in a variety of strengths. It is very economical, with the tablets being useful to dose individual birds. Individual birds are given ¼ of a 200mg "Flagyl" tablet once daily. "Flagyl" syrup (metronidazole, 40 mg/ml) is water-soluble and is given at the dose of 10ml per litre, but it is sugary and not very palatable to the birds.
4. Ronidazole – This is available as a water-soluble powder under a number of brand names world-wide, including "Ridsol-S", "Turbosole", "Tricho-Plus" and "Ronivet". The usual strength used is 10%. The dose at this strength is 1½g per litre. Weaker preparations are available but the birds need to be treated longer with these.
The drug is very bitter, so preparations stronger than 10% tend to be unpalatable to the birds. It has a very wide safety margin and is safe to use during breeding, racing and moulting. World-wide, ronidazole is the current medication of choice to treat canker. However, in some countries it is not available for use in pigeons, authorities being concerned that resistant organisms may develop. As the drug is used in food-producing animals such as pigs, its use is reserved for these.
5. Secnidazole – A long-acting anti-canker medication taking over 24 hours to exert a therapeutic affect but then staying in the system for 2–3 days. Combined with the short-acting ronidazole in "Ronsec". When pigeons are given a "Ronsec" tablet, the ronidazole starts working straight away. After 24 hours, as the ronidazole is being cleared, the secnidazole starts to work and then works for 2 days. This means that a single "Ronsec" tablet can exert its effect for 2–3 days. Clinical notes from the manufacturers of "Ronsec" state that 2 tablets given 48 hours apart will clear up to 95% of Trichomonad strains, including some hyper-resistant strains.
In any canker-control program, it is often best to rotate between at least two of these medications in order to decrease the chance of a resistant trichomonad strain developing. Currently, ronidazole-based preparations are used as the primary treatment, because of their effectiveness and wide safety margin, but it is a good idea to swap to one of the other available drugs every third or fourth treatment.