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World Owl Trust - leading the World in Owl Conservation
Friday 19th December, 2014

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Fighting Flies!

Chaco Owls, Strix chacoensis belong to the genus Strix which includes our own Tawny owl, Strix aluco and come from South America in the regions of Northern Argentina and Paraguay where their habitat is arid scrublands with giant cacti. We first bred them in 1999 and have bred them on several occasions since. The Chaco owls at the Owl Centre have been susceptible to an infection similar to avian malaria, called Haemoproteus. This can also be found in Snowy Owls Nyctea scandiaca and we once found it in another closely related species, the Rusty Barred Owl Strix hylophila.

Malaria-type infections are passed on via blood sucking insects. The infection, itself, is an organism which is called a protozoa and which lives in the host’s blood. The insects which pass on the infection are very specific as their saliva acts as an ideal suspension in which a certain species of blood protozoa may remain alive and be transported to another potential host when the insect bites its next victim. When bloodsucking insects bite they inject the victim with their saliva which acts as a local anaesthetic to prevent early detection thus passing the protozoa to its next host. These insects are known as ‘vectors’.

One of the best known of such ‘vectors’ is the malaria mosquito which helps spread the human-type malaria. (Only female mosquitoes of the genus Anopheles spread human type malaria.) The human-type malaria is caused by a protozoa of the genus plasmodium sub-species of which avian malaria is a distinct subspecies. The vectors for Avian malaria are mosquitoes of genus Culex and Aedes.

Haemoproteus is the protozoa for which the vector is the ‘lousefly’, Hippoboscid; also known as the ‘flatfly’. This bloodsucking insect specialises in sucking the blood of bird species and is shaped to be able to scuttle through feathers. Haemoproteus is harmless to adult birds that may nonetheless carry the infection. A flatfly which has previously dined on an infected host may then pass the infection on to a young bird. Some species of birds have no natural defence against this infection.

There is no way we can eradicate the flatfly as a vector as most wild birds will have them. The adult flatfly dies off in Autumn but as a species survives in nest linings as single laid eggs which hatch in Spring to form the next generation of adults.

We clean all our nest boxes to keep the numbers of flatflies down and as an additional precaution we hand reared this year’s three Chaco owlets from an early age and housed them separately from their parents and any source of infection, in our quarantine unit. So far they have remained healthy and by next year, as adults, they will have built up a resistance to the disease.

Wulf Ingham
Head Keeper

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