CANKER - ITS PREVENTION, CONTROL AND TREATMENT By Dr. Collin Walker.

Nature of the disease

The disease canker is caused by a protozoan Trichomonas columbae. This is a microscopic single-celled organism. It lives within the digestive tract of pigeons, in particular the throat and crop, and can also involve associated areas such as the bile duct. 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 contains 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. 

Control of canker during the breeding season

Correct medication is vital 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 too many trichomonads over a given period of time to their youngsters. 

 

 

Medications Available

Any one of a group of medications called nitro imidazoles are effective against trichomonads. There are four commonly in use:

1. Dimetradazole - The common brand name here 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 for 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 (3 grams) 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. Carnadazole - The common brand name here is Spartrix. It is only available in tablet form. It has a wide safety margin and is very useful for individual bird dosing, particularly youngsters in the nest. The dose is one 10-mg tablet daily.

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 200-mg Flagyl tablet once daily. Flagyl syrup is water soluble and is given at the dose of 5 - 10 ml per litre but is very 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 ½ teaspoon 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. 

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. 

 

 

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