Parasites of Raptors

Jan 11, 2012 by  Admin

Any parasite relies on survival of the animal in which it lives in order to survive itself. It is therefore not normal for a parasite to lead to the death of the host in which it lives. Under normal circumstances parasite and host will live in a balanced harmony. The exception arises when the normal hosts resistance against the parasite, which usually keeps it’s infestation under some semblance of control, is reduced allowing the parasite to gain the upper hand. Such situations arise when wild birds are short of food, following migration, accident, injury or during extended periods of inclement weather. For the falconer’s bird training, chilling, accident, or other causes of stress may trigger off the same situation. There are exceptions to this rule, where even a small number of parasites can cause disease; this arises where the parasite only needs to live in that host for a short period, in order to complete a life cycle, this done he does not mind if the host becomes diseased and dies. Recently parasitic diseases have been increasing in incidence in captive bred birds, this is as a consequence of increased levels of exposure to the parasite, as a consequence of increased contamination of the aviary by the parents.

External Parasites

A large ecto parasites infestation on a bird is typically a sign of the bird being ill for other reasons, as any fit bird will usually control it’s own parasites. So rather than treating the parasite alone, one should always look for a further cause of illness.

Hippoboscids (keds or flat flies) are perhaps the commonest parasites of raptors. They are blood suckers, although they rarely cause any significant blood loss. There is however now evidence to suggest that they can and do carry blood borne parasites between one bird and another. In particular the blood parasites ‘Leucocytozoon’, ‘Plasmodium, ‘Sarcocystis’ as well as other blood borne infections. In the United Kingdom such blood borne parasites are rare, however in warmer climates such as USA diseases such as malaria are highly significant. After the warmer summers of 1994/95, the incidence has increased, affecting birds aged 3-5 months, to date owls (especially snowy), Harris Hawks and Gyr Falcons have been affected. In one case, the affected bird had caught a magpie only nine days earlier, which had a heavy infestation of hippoboscids, in time it became evident that these had carried a blood parasite infestation, which caused a dramatic and fatal infection of the Harris Hawk in a very short time.

Lice are also a common ecto parasite of raptors. Lice feed off skin debris and feathers, they do not however survive off the host for long, and hence treatment with routine insecticide preparations is relatively easy.

Conversely Dermanyssus gallinae the ‘Red Poultry Mite’, does survive off the host for considerable periods. This mite lives in crevices in the wood work and usually only comes out at night to feed, as such a feather plucking bird may appear free of parasites when examined during the day, whilst the same bird is crawling with them at night.

Any ecto parasite which actually sucks it’s hosts blood can be easily and readily controlled by use of the cattle wormer ‘Ivomec’ (MSD AgVet), however this will need to be diluted, doses and suitable diluants can be arranged by your veterinary surgeon.

Other ecto parasites are best controlled by the use of insecticides, however great care must be taken that only safe preparations are used. Some sprays contain either active ingredients or propellants, which can lead to toxicity or irritation to the air sacs. The new cat and dog flea preparation Frontline’ has proved safe and effective in over 100 birds on which we have used it. It appears to be not only more effective but also far safer than previously recommended ectosparasite preparations.

Internal Parasites

Many bird keepers, falconers and rehabilitators simply worm their birds annually or when they are handled and believe that all is then well. This concept is seriously flawed, and can on occasions lead to serious repercussions.

Fluke: fluke are a relatively common although usually non-pathogenic parasite of raptors. They may inhabit the small intestine or the bile ducts. Diagnosis is made only on faecal examination, and although usually non-pathogenic, when found treatment should be given. The drug which is most commonly used is rafoxanide at a dose of 1Omg/kg, or praziquantel (droncit) 5-10mg/kg daily 14 days or chlorsulon (Curatrem) 20mg/kg by mouth 3x at 2 week intervals. Both the diagnosis, advice on treatment and the drug will be available from your vet.

Tapeworms: tapeworms are a relatively common parasite, but are rarely pathogenic. Clinical illness will only occur in situations in which there is very heavy infestation, which can lead to an obstruction of the small intestine. Treatment is by the use of Praziquantel (Droncit, Bayer), which is available in injection or tablet form, and birds should be dosed at 5-10 mg/kg or chlorsulon as above.

Roundworms: these are the largest and most significant group of endo parasites. The group includes the ‘Syngamus trachea’ and ‘Serratospiculum sp” which affect the wind pipe, and air sacs respectively. Both will cause respiratory signs in infected birds, however in both cases it is particularly important that the diagnosis is made prior to treatment being given. In the case of Syngamus even after the worms are killed they will remain in the airways for up to six weeks slowly rotting away causing respiratory signs and occasionally pneumonia in the meantime. Serratospiculum is most commonly found in this country in imported birds (coming from warmer countries) The worm itself does not usually cause any clinical signs, and may live in the air sacs happily for several years. However if the worm is killed it will rapidly putrefy often causing a severe air sacculitis and death. If the worm is diagnosed then the preferable treatment is to treat the bird with wormer daily for 14 days and then to surgically remove the worm from the air sac.

Drugs which have been used in the treatment of roundworms include pipeazine, levamisole, benzimidazoles (e.g. Panacur or Mebenvet or Pyrantel) and ivermectin (Ivomec). Some of these are now old fashioned and ineffective, others have very narrow safety margins and can be dangerous, others are potentially toxic at certain times of year (especially during the moult), others are safe.

Protozoa: This group of parasites includes ‘Trichomonas gallinae’ the agent which causes ‘Frounce’. The most common source of infection is from pigeons. Many falconers believe that just because the pigeon looks clean, or by avoiding feeding the crop, the disease can be avoided; this is not invariably the case – even the breast muscle itself can carry the infective agent. Any pigeon fed to raptors should be frozen first as this freezing kills off virtually all the organisms. The disease is seen as white plaques in the mouth, throat or crop. However the condition must be differentiated from infection with Capillaria, Candida or Vitamin A deficiency or owl Herpes Virus (in owls). The differential diagnosis can be easily made by your vet. Treatment is with Carnidazole (Spartrix) 25mg/kg once. The single treatment as opposed to the previously recommended daily treatment for 5 days makes therapy a lot easier, particularly for young wild or captive birds still on a nest being fed by the parents.

The same group of parasites also includes coccidia, which may be present and cause or not cause disease, depending which exact species of coccidia is involved. Likewise if disease does occur the clinical signs and treatment required will be different. Coccidia have been recognised as increasing due to a build up of infection in captive breeding aviaries. The disease affects primarily young birds, prior to their having developed any immunity of their own. The condition is treated with Toltrazuril (baycox) at 10mg/kg once daily on three consecutive days, or Clazuril (Appertex) at 5-10mg/kg once daily on three consecutive days. Giardia and Hexamita are two further protozoa, which can cause clinical disease.

Coccidiosis in Merlins: as most readers will be aware, coccidiosis in Merlins has been an increasing problem for a number of years. In a paper presented at the Small Falcon Conference in 1991, it was shown by this author to be the single largest cause of death in captive Merlins. Since that time the condition has increased in incidence, and in the last two years has also been shown to be affecting considerable numbers of Goshawks and Peregrines. Although the therapeutic regime recommended above is effective in preventing death in affected birds it is still not effective in totally eradicating the organism from the birds system. As a consequence some months later the bird will start to shed the organism again, (although not becoming ill itself). This shedding will lead to considerable contamination of the aviary, leading to the future infestation of other birds. It is generally only young birds, or those who are ill for any other reason that will actually succumb to the disease. This disease is subject of considerable on-going research at the Clockhouse Veterinary Hospital. We are still happy to test free of charge mute samples from any captive Merlins, so long as the keepers are prepared to to send samples on a regular monthly basis. It is only by this continued research that we hope we can finally get on top of this disease which has serious future implications for the captive breeding of raptors, not only in the UK but also in other parts of the world.

Above all the important fact that all keepers should realise is that no one treatment will be effective against any more than one of these groups of parasites. Treatment will lead to a false sense of security, may be unnecessary, and moreover can be dangerous. Prior to any treatment a faecal sample can be quickly and cheaply examined by your veterinary surgeon who can then advise and supply the most suitable agent.At the Clockhouse Veterinary Hospital, we run a fast, efficient and cheap service for the testing of mute samples for parasites. Keepers sending a sample are requested to telephone after 12 noon on the day (weekday), that we receive the sample, and we will inform them of the result.