Report on Feather Diseases - Part I

Less common problems are dealt with in Part II.

Over the past few years fanciers have increasingly reported feather abnormalities in their exhibition type budgerigars. In particular, they have noticed a tendency for birds to lose their tail feathers which then fail to regrow ("tail-less wonders"). Reports of similar abnormalities in larger members of the parrot family increased at the same time.

In view of these reports, discussions took place between the Budgerigar Society Lancashire, Cheshire & North Wales BS and myself. It was decided that the two societies would fund work on feather diseases to be carried out at the University of Liverpool. Their financial support is acknowledged with thanks. The work was begun on 1 July 1993 and concluded on 30 June 1995.

We are grateful to members of the fancy for the supply of birds and feathers together with related information. Birds and other samples were received from all areas ranging from the Isle of Wight to Glasgow and from Cornwall to Norfolk, though the majority came from Lancashire, Merseyside, Cheshire and North Wales. The total number of birds and feather samples received was 198.

Results Published to Veterinary World

A technical version of this report will be produced and submitted to the veterinary press, making the results available to veterinary surgeons. They will then know which diseases commonly occur and will be able to advise clients with feather problems in their birds.

Results

The diseases and other abnormalities found in the survey are summarized in Table 1 (at the bottom of this page). Also in the table are figures from the other comparable work found in the literature. This was a survey of biopsies (small pieces of tissues taken from live animals) from a variety of psittacines with feather disease, which were examined microscopically. The work was carried out in America (Schmidt 1987). It will be noted from the table that the diseases found in the American survey were of a limited nature.

Only some of these were seen in my survey but at a different prevalence. The exception was psittacine beak and feather disease, where the incidence was equivalent in both surveys. In the Schmidt survey the causes of the diseases were not investigated, nor was there any attempt to correlate certain diseases with feather type. Caution is required when interpreting the figures in Table 1. The figures are correct for the birds we received, but some fanciers supplied large numbers of birds with the same condition and this has skewed the results. This was particularly true in the case of psittacine beak and feather disease, where two breeders supplied over half the affected budgerigars. With pulpitis, the same tended to occur, though to a lesser extent. Conversely, many fanciers did not submit birds with French moult as this disease was specifically excluded from the project. For these reasons the figures in the table give only a rough guide to the prevalence of these conditions in the overall budgerigar fancy.

It will be noted from Table 1 that there was an average of 1.48 conditions per bird. Most of these were cases of mite infestation and damage in birds with other feather disorders. In other cases two apparently unrelated feather conditions occurred in individual birds.

Terms

Before considering the results in detail it may be useful to define a few terms.

Viruses

These are a type of germ which lives and breeds inside the cells of animals. They are capable of living outside the animal but will not multiply in this situation. As far as birds are concerned no treatment for viral diseases is available.

Bacteria

These are much bigger than viruses and usually live between the cells of the infected animal and multiply both within the animal and outside. They can usually be killed by antibiotics.

Congenital Disease-

This is a disease which the bird has from the time it hatches, although occasionally the symptoms may not show for months or even years. Such diseases may or may not be inherited.

Inherited Disease

This is a disease which is passed from parent to offspring via the animal's genes. Depending on the mode of the inheritance the parents may, or may not show evidence of the disease.

Vertical Transmission of a Disease

This is transmission of a disease from parent to offspring by contact or via the egg. Such diseases are not inherited although they may appear so.

Horizontal Transmission of a Disease

This is transmission of a disease to other in-contact birds but excludes parent to offspring transmission.

Follicle

A small pocket-like depression of the skin from which the feather grows and by which it is attached to the bird before a moult.

Barb

The branches coming from the feather shaft and forming the bulk of the feathers.

Barbules

These branch off from the barbs and have small hooks on them (barbicels) which lock together the barbs and thus the feather.

The part of the report which follows details the findings in each condition or groups of conditions and gives an indication of the cause and treatment when this is known.

Psittacine Beak and Feather Disease

It came as a considerable surprise that this topped the list of diseases occurring in 21.2% of all the birds submitted, because in the first year no cases were seen at all. One possible explanation is that the disease has only recently been introduced into the exhibition budgerigar and only became widespread in the last year or so.

The disease is caused by a virus. Infected birds may be symptomless carriers although no such cases were found in the survey. This was to be expected as only sick birds were seen. Fanciers were unlikely to send in a symptomless bird for examination. There appeared to be two manifestations of the condition depending on the age of the bird. In budgerigars less than 6 months old the feathering was poor with extensive bald or semi-bald areas on the body and legs, loss of most or all of the large wing and tail feathers, and loss also of some of the smaller feathers in these sites. The remaining feathers tended to be of poor quality and sometimes misshapen. Young affected birds tended to be small for their age. In older birds the contour feathers were usually unaffected, but all, or some of the primaries, secondaries and large tail feathers were missing. Regardless of age of the bird the head and upper neck was spared. In no cases was the beak abnormal. Affected birds seemed lively and active and no bird died from the condition, although such birds were kept at the university, only a few months at most.The disease is transmitted to other birds on the premises both horizontally and vertically, although transmission tends to be relatively slow. There is no treatment for the disease, nor are there any preventative treatments in the UK. Measures such as cleanliness, the testing of new arrivals and the isolation of affected birds, will reduce the rate of the spread of the disease. An experimental vaccine has been shown to be effective in the USA. Should fanciers or societies wish to support further research into this disease I can provide a contact name in America.

Pulpitis

This is an inflammation of the pulp of the growing feathers, especially the large ones of the wing and tail. Such diseased feathers may break off or be shed prematurely. Once shed the feather may not regrow. A significant proportion of the birds submitted with this disease had been sent in as "tail-less wonders". Pulpitis is believed to be a major cause of this condition. The cause of pulpitis is usually a bacterial infection,predominately Staphylococci or Streptococci although about 15% of cases are probably of viral origin. These germs are thought to live on the bird's skin but only cause problems when they invade the growing feathers. There is a strong correlation between this condition and markedly buff, suggesting there may be something inherent in buff feathers which makes them susceptible to this condition. There is also some evidence of vertical transmission.

While in theory, prolonged antibiotic treatment might cure the condition when a bacteria is the cause, this has not been tried. Repeated bathing of the birds in Virkon S seems to cure about 40% of cases. A few appear to recover spontaneously. At the present time there appears no way of predicting which birds will respond to treatment and which will not.

Mites

Feather mites of a variety of species are very common on budgerigars, but are not usually seen by the fancier as they are mostly very small. They are visible only under microscope. They also tend to live deep in the feathers close to the skin. In the majority of birds they cause no problems at all. Occasionally mites can cause feather disease in a number of different ways. There were feather abnormalities in all the cases of mites listed in the table. Firstly, in heavy mite infestations these active parasites caused irritation. This in turn led the birds to scratch and bite their plumage, leading to tatty feathers, or feathers which had been bitten off at various positions along the shaft. As mites prefer to live on a bird's rump, the tail feathers are frequently the most affected. Secondly, some species of mite will eat small segments of the growing feathers, so when they are fully formed a small part of the feather is seen to be missing. These are most obvious on the large wing and tail feathers, although the contour feathers can be affected at times. The third way mites can affect the feathers is by invading the follicles, which results in the growth of a distorted feather. Only the follicles of the large feathers of the wing or tail seem big enough for the parasite to enter, and usually only one or two feathers are affected. These are frequently very short or horn-like.

The diagnosis of this condition depends first on finding the mites. However, as these parasites are so common, one has to eliminate the causes of the feather disease before a diagnosis of the mites can be made. Treatment with any of the proprietary anti-mite drugs is effective.

Feather Cysts

It had not been anticipated that this condition would be such a common cause of feather abnormalities. The other unexpected feature of this condition was, that in the vast majority of the cases, the cyst or cysts had not been spotted by the fanciers. The birds had been sent to me because they had feathers which would not regrow.

Almost all the feather cysts occurred on the outer parts of the wing or the tail, although some were seen on the necks of birds. The cysts were of three types, the first and most common for 70% of the cases, was roughly spherical, up to 1.25cm (just over half an inch) in diameter. Cysts of this type were either very hard or slightly soft, depending on the thickness of the fibrous capsule. This capsule surrounded a core of yellow cheesy material, and the distorted remains of one or more feathers.

The second type was very similar to the first, but the surrounding skin was inflamed and thickened. As most of the lesions had not been noticed by the fanciers it was not possible to establish whether the damage to the skin came before or after the development of the cyst.

The third type was only seen on wings and accounted for fewer than 10% of cases seen. These were multiple and long and narrow in shape, lying side by side with one cyst corresponding to the follicle of one primary feather. They contained cheesy material as in the other cysts but in a proportion, a very short malformed feather was protruding from the tip of the cyst.

There was a very strong correlation between the first two types of cysts and marked buffness. Birds with this type of inherited plumage have a strong tendency to develop cysts. Unfortunately fancier's records were insufficiently detailed to show if cysts themselves are inherited, as is the case with the equivalent condition in canaries (lumps).

Research suggests buff feathering is linked to feather problems. There is no treatment for this condition other than surgical removal and it must be borne in mind that the birds will never regrow the feathers. It is probably not advisable to breed from birds with feather cysts or from their close relatives.

Stress Marks

Under this category we will look also at the absence of barbs and barbules, poorly formed barbs or barbules, and improperly shed sheaths. Stress marks are lines on the feathers where the barbules have not formed. Sometimes there is a line of weakness in the shaft at the same level, and the feather may break off at this point. If the barb and barbules are absent from a section of the feather, or if they are poorly formed, the feather does not hold together, giving the bird a tatty appearance. Improperly shed sheaths is a condition when the feather sheath is not shed in the usual way and instead persists over a greater part of the feather than is normal.

Occasionally, fully-formed feathers are totally enclosed in their sheath. In all three conditions the abnormality is most easily seen in the large wing and tail feathers.

In all these conditions, the changes seen in the feathers usually indicate something wrong in the bird's system in general. This needs to be attended to rather than concentrating on the feathers. With stress marks, the disturbance is general short lived, a matter of a few days to a week or thereabouts. The other conditions are associated with longer periods of illness, which can be quite mild, periods of stress or poor diet. When one or two birds in a flight are affected, this does not mean that the overall diet is unsatisfactory. Some budgerigars are very pernickety feeders and while different foods need to be supplied, it does not mean every bird will eat all of them. Provided the underlying problem is identified and corrected, the birds will almost certainly grow a set of normal feathers at the next moult.

Feather Dusters

This well known condition in which the feathers of the affected birds grow continually is noted very shortly after the birds begin to feather up. Such birds usually die at 6 to 8 weeks of age. the budgerigar that we had for a long time eventually died at 2 years. It grew contour feathers up to 24cm (9.5 in) long.

Some, and probably all, cases of this disease have a genetic inherited basis. There is a strong correlation between affected birds and buff feathering. A paper by Kevin Eatwell in Budgerigar World said that unaffected siblings of feather dusters are excessively buff and therefore may be retained for breeding. My view is this is not advisable.

The 8 conditions described above were responsible for two-thirds of the cases seen. The other 29 diseases accounted for the remaining third. These will form the second part of this report.

Table 1 - Main Feather Diseases found in a Survey of 198 affected budgerigars
Data from another survey of all types of psitticines are included for comparison purposes (Schmidt 1987)

Condition	No of cases	% of cases	Schmidt data%
Psittacine Beak and Feather Disease	42	21.2	24.4
Pulpitis	40	20.2	4.2
Mites	36	18.2
Feather cysts	29	14.6
Stress marks	16	8.1
Barbs & Barbules missing or poorly framed	12	6.1
Feather dusters	12	6.1
Improperly shed sheaths	12	6.1

Original text copyright 1996, Dr John R Baker

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