There are three potential diseases which may cause oral lesions detailed below:
Trichomoniasis (Oral Canker, Frounce, Roup)
Oral canker is caused by Trichomonas gallinae (a motile protozoal parasite). It tends to be an opportunistic pathogen taking advantage of any damage to the oral, oesophageal or crop mucosa. The parasite is widely present in wild birds and can be spread through shared drinking water (not through the faeco-oral route). Pigeons are a well recognised source of the parasite. The parasite causes caseous lesions which are often described as ‘yellow buttons’. Once infection takes hold the bird becomes reluctant to eat leading to weight loss.
Oral Canker – before treatment
Oral Canker – after treatment
Diagnosis is based upon using microscopic examination (X40) using warmed slides to look for motile flagellate protozoa. This must be done within minutes of sampling before the parasite dies. The lesions when present on post mortem examination are reasonably diagnostic.
There is no currently licensed treatment in the UK, however oral Metronidazole has been used successfully at 50mg/Kg. The BSAVA formulary recommends treatment for 5-7 days however I have found it necessary to continue treatment until the lesions are fully resolved. Due to concerns regarding public health about the use of Metronidazole, tetracyclines are commonly used at 60mg/Kg for several days. It is thought that tetracyclines work by controlling secondary bacteria rather than directly harming the parasite itself. Since the organism can be spread through the drinking water it is advisable to remove the infected bird from the flock and ensure all the birds in the flock have access to fresh clean drinking water.
The prognosis is moderate for this condition with not all lesions responding fully to treatment.
Prevention is based upon discouraging wild birds and ensuring poultry have continuous access to clean water.
Crop Mycosis/Thrush/Monilaisis
Thrush is caused by a disruption of the normal flora of the upper digestive tract leading to a fungal overgrowth of Candida albicans. (It should be noted that whilst this is most commonly a condition of the crop other areas of the digestive tract including the oral mucosa may be affected). Affected birds often present as being dull and inappetant. Occasionally these birds will often have a yeast-like odour to their breath.
Whilst there is no single cause for thrush, the main predisposing factors are mouldy feed and antimicrobial usage both of which disrupt the normal flora allowing for fungal overgrowth.
Diagnosis is usually based upon seeing raised white/yellow areas on the oral mucosa. However smears can be made of the lesions to look for Candida.
On post mortem examination the upper digestive tracts of affected birds will often have raised, white, circumscribed lesions together with ulceration and mucosal necrosis. These lesions can be anywhere from the oral cavity right through to the oesophagus and crop.
Treatment involves identifying and removing the underlying predisposing factors. However antifungal agents such as Nystatin may be given at 100,000-300,000 IU p.o. daily for 10 days under the cascade.
The prognosis is usually favourable but repeat treatments may be necessary.
Prevention is based upon ensuring an appropriate diet along with avoiding the excessive use of antimicrobials.
Fowl Pox
Fowl Pox is caused by a pox virus which is usually spread mechanically (e.g. by biting insects or through pecking related wounds) or more rarely by the inhalation/ingestion of the virus. As such there are two forms of fowl pox- the ‘wet form’ and the ‘dry form’. The ‘dry form’ occurs through mechanical transmission and can lead to the formation ‘pocks’ on featherless skin such as the comb or snood. These lesions begin as nodules which progress to become scabs. The oral route of infection can more rarely lead to the formation of small white nodules in the buccal cavity which progress to become more extensive caseous lesions. In extreme cases these lesions can progress to become diphtheritic. This is known as the ‘wet form’. In severe cases these oral lesions may restrict breathing causing respiratory signs.
The virus has an incubation period of 4-10 days with the subsequent lesions resolving in between 2 and 8 weeks. The virus is not highly infective and as such its spread throughout a flock can be slow.
Whilst these lesions being found either during clinical examination or on post mortem examination are highly suggestive of fowl pox; virus isolation, histopathology or PCR can be used to provide a definitive diagnosis. Serology may also be used to provide a diagnosis retrospectively.
There is no specific treatment for fowl pox and the majority of cases have an uneventful recovery. However practitioners should ensure that in the ‘wet form’ of fowl pox the diphtheritic membrane doesn’t obstruct the larynx and that the bird is kept both hydrated and nutritionally supported. Antimicrobials may be beneficial in such cases to control secondary bacterial infection. In the face of an outbreak vaccination can be used.
Prevention is based upon good hygiene and biosecurity. Like other pox viridae, fowl pox virus can be difficult to remove from a holding. Potentially a live attenuated vaccine can be given through cutaneous scarification usually on the wing web. However in the UK there is no currently licensed fowl pox vaccine. The pigeon pox vaccine is more readily available and offers some cross protection against fowl pox.
Fowl pox
