Thursday, 28 March 2013

Mystery of the toxic quail

Common Quail (by Callie Jones)
Some 3,500 years ago, according to the Bible, Moses led the Israelites out of Egypt into the wilderness. When they became hungry and demanded flesh to eat, God sent a wind that deposited quails for miles round their encampment. But when they gathered and ate the quails, “the Lord smote the people with a very great plague” (Numbers 11:31–33).

Later, ancient Greek and Roman writers also described sickness after consuming quails, and severe illness still occasionally afflicts quail-eaters — sometimes killing elderly victims. 

The sickness, known as coturnism, is caused by a toxin in the fat and flesh of the wild European Quail, or Common Quail, Coturnix coturnix. The toxin causes rapid breakdown of skeletal muscle (rhabdomyolysis), leading to muscular weakness and producing breakdown products that damage the kidneys and may lead to acute renal failure. Other symptoms include vomiting, respiratory distress, excruciating pain and paralysis. Sufferers who recover may take 10 days to get over the symptoms. 

The whys and wherefores of coturnism are a mystery. Although there are various other species of quail, only C coturnix has been implicated in the syndrome. And the toxicity occurs only during certain stages of migration and by no means in every bird. 

European Quails are tiny game birds that feed on seeds and insects. They spend the summer in Europe and the winter in sub-Saharan Africa. They follow two main migratory routes, with some crossing the Mediterranean at its eastern end and others at its western end. Toxicity in birds using the eastern flyway occurs only when they migrate south in autumn, while in those using the western flyway it occurs only during the northerly movement in spring.

It has been suggested that coturnism is caused by alkaloids (coniines) in the flesh of birds that have fed on the seeds of hemlock, Conium maculatum. But hemlock cannot be responsible for all cases because it is not in seed in spring when western flyway birds are toxic. The quails must therefore derive their poison from other food sources. 

Another plant named as a suspect is the annual yellow-woundwort, Stachys annua, which sets seed in the various parts of its range at the same time as the quails become toxic. Its seeds have been found in the digestive tracts of quails that have caused coturnism, but investigators have as yet failed to identify any toxins in the seeds. 

Definitive research is needed before the mystery of coturnism can be fully explained.

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