The Fight Against Frounce

The Suffolk Owl Sanctuary’s Raptor Hospital is busy at all year round, but particularly during the warmer weather.

Not only are the patient numbers swelled by a steady flow of young “branchers” that have fallen out of trees, but adult owl and other bird of prey admissions also tend to peak during the Spring and Summer seasons.

In the main, casualties will have suffered some degree of trauma due to incidents such as chimney falls, flights into windows and road traffic accidents. However, around 10% of cases consistently present with symptoms of bacterial infections or disease.

The commonest, but most virulent of these diseases is called Frounce - a yeast infection of the digestive tract (similar to thrush) caused by a protozoan called trichomonas. This debilitating condition is transmitted to birds of prey through eating pigeon meat, the causal bacteria being present in the crop of a dove or pigeon host.

This is why falconers never feed pigeon meat to their birds and why the raptor hospital is unable to accept avian casualties other than birds of prey - the risk of cross contamination from pigeons, doves or other garden birds to the Sanctuary’s resident population or hospital and recuperating inmates being too great.

Compression in the throat caused by the frounce causes the   throat to swell and the eyes to close

Compression in the throat caused by the frounce causes the throat to swell and the eyes to close

Transmission of the Frounce bacteria occurs by the discharge of bodily fluids, during the feeding of young by adult pigeons and doves through regurgitation. It initially manifests itself by white spots around the mouth or crop of the infected bird, often described by falconers as “cheesy plaques”. If not checked, the infection will then spread into the eyes, throat and brain, the latter always resulting in a fatal outcome.

Regrettably, birds suffering from Frounce do not usually arrive at the raptor hospital until they have become so debilitated that their normal functions have become compromised. An infected bird will be unable to hunt efficiently or eat enough to maintain health and condition - it is at this point that they are brought to the hospital for treatment. Frounce is a particularly insidious infection which is difficult to treat once well established, however, there is some chance of a successful outcome if treatment with antibiotics can be initiated early in the developmental cycle of the infection i.e. before it is so entrenched as to prohibit eating and swallowing.

The Tawny Owl admitted to the raptor hospital with classic “cheesy plaque" symptoms of Frounce

The Tawny Owl admitted to the raptor hospital with classic “cheesy plaque" symptoms of Frounce

Just last week a Tawny Owl suffering from Frounce was admitted to the Suffolk Owl Sanctuary’s raptor hospital.  Although lacking in energy and condition, the owl appeared to be relatively fit and alert: an initial assessment revealed the presence of the infection in the bird’s throat and a course of antibiotics was started immediately.  Luckily, the disease did not appear to have spread further, so the prognosis for this Frounce case seemed cautiously positive! The owl now seems to be gaining strength and its condition is improving daily, with the infection stabilised and in the next few days staff hope to see the Frounce markedly subside and the bird’s recovery gain momentum.


Frounce is by no means a “modern” disease and falconers have been forced to contend with its devastating effects for centuries. The National Geographic News recently carried an article shedding new light on parasitic evolution, alluding specifically to the history of the trichomonas organism :

“After surviving countless battles, a giant T.Rex was ultimately taken down by a microscopic parasite akin to one carried by modern pigeons. This finding is a new interpretation of multiple holes in the jawbone of “Sue” the largest and most  complete Tyrannosaurus rex fossil yet found. In a new study researchers …propose that the holes are lesions made by an ancient version of trichomonosis, a single-celled parasite that infects the throats and beaks of modern birds”.

This research appears to explore the possibility that this pernicious disease has actually been decimating bird and animal populations for millions of years. Let us hope that a fuller understanding of the nature of trichomonosis may lead to the development of more efficacious treatments for owls and other birds of prey in the future.