No method of naming diseases is completely satisfactory; for in only a small proportion of cases does a single known microbe cause a recognizable disease. Frequently, one infection can produce several merging or distinct manifestations in various groups of birds, it may also show different signs in different species. Alternatively, one well-recognized group of clinical signs may be caused by several bacteria or viruses as the result of a variety of different pathological changes. Organisms, while not in themselves capable of causing a recognizable disease, may often produce a weakened bird which is the prey to other more pathogenic bacteria capable of creating a clearer picture of disease. In this section diseases will be described which are caused by specific bacteria or groups of bacteria. Clinical diseases in which the cause is multiple or unknown or which are of a local nature, will for the most part be found under the region or system concerned.
Salmonellosis, Paratyphoid or Infectious Enteritis:
These names are given to the disease caused by any one of the numerous related but different species of bacteria called Salmonellae. They are closely related to Escherichia coli and paracolons mentioned later and belong to the family of gut organisms Enterobacteriaceae. Minor reclassification is constantly going on and new members are frequently being discovered. Although only a proportion of species or serotypes are of importance in birds, the disease they produce may under some circumstances be severe. Many of the avian species and strains of Salmonellae are also capable of infecting reptiles, mammals and man. Paratyphoid infections are of special importance in many species of cage birds, especially in mixed aviaries, breeding establishments, pet shops, and indeed all places where a number of birds are kept closely together. Because of the relatively high incidence of the organisms in some wild birds, e.g. house sparrows their presence in rodents and the almost inevitable presence of mice and rats near aviaries, attracted by spilt seed and other food, transmission of infection to captive birds is a constant danger. In indoor aviaries, with brick floors and very fine mesh netting, such unwelcome species can usually be excluded. Salmonella typhimurium, S. enteritidis, S. oranienburg, S. anatum, S. thomson and S. paratyphi are examples of the many types which may be encountered in a wide variety of species which include among many others, doves, quail, pheasants, water birds of all kinds, canaries and other finches, sugar birds, parrots, budgerigars and robins. The majority of infections are caused by S. typhimurium and smaller numbers by other Salmonellae. In some birds, especially waterfowl and poultry, these infections can affect embryos in the egg by contamination of the shell with infected droppings. Less frequently, and notably in waterfowl, embryo infection may be derived from an infected ovary. Because cage-bird eggs are almost all hatched in the nest and seldom artificially incubated, most Salmonella transference to nestlings is probably from the parent birds soon after hatching. Incubator hatching, if perfected for cage birds, would in most species greatly limit spread in the young. The infection of adult or growing stock occurs in three main ways:
1. Contamination of food at source; proprietary egg food is a potential danger.
2. Contamination of food or water by rodents or wild birds in the aviary or store.
3. Contact with a newly-acquired infected bird.
Less commonly, infection is spread at shows or as the result of handling by visitors who have been in contact with the bacteria. Spread throughout an establishment is aided by overcrowding, allowing food to become stale, scattering seed and food where it can attract vermin, and other unhygienic practices. Flies and some parasites are also capable of transmitting the disease, while S. typhimurium is able to live for almost four months in stagnant water in temperate climates.
CLINICAL SIGNS: In an outbreak, the initial picture may depend on the source of infection and the age groups first affected. The severity may also depend to some degree on the type of Salmonella responsible. The severest and most acute outbreaks are usually seen in young chicks, for example, when infected egg food is fed to parents and later to offspring. The parents at this stage may show little evidence of disease. However, low hatchability rates, dead-in-shell or weak newly-hatched chicks, and chicks "fading" during the first few days of life are strongly suggestive of the infection. The blood, other tissues and droppings of such chicks as well as the parents' excreta, are rich sources of the organisms. As little as 10 per cent of all eggs incubated may hatch, and all of these chicks may die before leaving the nest. The effect of a long-established infection, however, may be much less spectacular. Newly-hatched chicks which are affected are likely to be small, weakly, bedraggled and produce loose droppings, giving rise to the condition called "sweating" by some breeders. It is sometimes thought that a single hen has merely been clumsy when the flattened dead chicks are later found in or thrown out of the nest, but poor hatchability in several nests should point to a more serious cause. Losses usually start a few days to two weeks after eating contaminated seed or other food. According to the virulence of the organism and the susceptibility of the species concerned, clinical signs may last only a day or two with occasional losses over several weeks or, within 10 days of the first death, as much as 90 per cent of the growing and adult stock may be dead. Signs range from sudden death to gradual onset of depression over one to three days, accompanied by huddling of the birds, fluffed-up feathers, unsteadiness, shivering, loss of appetite, markedly increased or absence of thirst, rapid loss of weight, accelerated respiration, and watery yellow, green, fawn, or occasionally grey or blood-tinged droppings. The vent feathers become matted with excreta, the eyes begin to close, and immediately before death some birds show apparent blindness, inco-ordination, staggering, tremours, or other nervous signs including convulsions. In addition pigeons sometimes show arthritis, especially of the wings. A really sick bird seldom recovers even with appropriate treatment.
DIAGNOSIS: Diagnosis cannot be made on the basis of clinical signs alone. Confirmation depends on isolating the bacteria from the heart blood or lesions of dead birds and the droppings of live, recovered carriers, but this can only be done in a properly equipped laboratory. In an establishment where occasional losses have been experienced in several age groups, examination of droppings from birds which have been in close contact with the dead birds should be made because salmonellosis can be well established before it is even suspected. When an infection is well distributed throughout the stock and established, but not causing heavy losses, it is said to be endemic or enzootic. When an infection suddenly wreaks havoc in an aviary, causing a high incidence of clinical disease and deaths, it is referred to as an epidemic or epizootic. Paratyphoid or salmonellosis can produce both situations. The blood-testing methods for antibodies (agglutination tests) used in the related pullorum disease or bacillary white diarrhoea (B.W.D.) of poultry and caused by S. pullorum, and fowl typhoid (S. gallinarum infection) have not been used very much for cage birds, but represent a useful means of identifying carrier birds harboring a particular strain of organism. Unfortunately, when small birds are infected, blood testing is impractical as sufficient blood cannot be obtained without seriously jeopardizing the birds' lives. Negative results also sometimes occur in birds previously known to have been infected. However, in cage birds, recognition that a pathogenic strain of Salmonella is present in carcasses or in droppings is sufficient warning to commence remedial measures. Infectious diseases of cage birds, particularly those of an acute nature, often present similar features regardless of cause. Salmonellosis therefore, especially in adults, can be confused with such infections as pasteurellosis or pseudotuberculosis.
TREATMENT AND PREVENTION: It must be stressed that, short of destroying all infected birds, carriers and those in contact, it is unlikely that an establishment can be entirely cleared of the infection. If rodents or wild birds can gain access, they will soon be acting as a reservoir of the organism. Because of the individual financial and sentimental value of cage birds, treatment is more generally attempted than in the case of poultry. This reduces mortality and greatly slows the onset of new cases of clinical illness but masks infected birds by turning them into symptomless carriers. Treatment must be prolonged, and repeated at intervals in all valuable birds. Breeding should also be discontinued for the current year. Some would say that once birds are infected they should never be used for breeding again. Minor or major fresh outbreaks are to be expected in following seasons, especially if sudden change of food occurs, also during a cold spell or breeding, or indeed during any conditions of stress. The greatest success in treatment has occurred with the drugs furazolidone and spectinomycin. Sulphonamides, particularly sulphadimidine and sulphadiazine are also quite effective in reducing losses and checking clinical signs. The tetracyclines, chloramphenicol and neomycin generally appear to be less effective, although some strains respond reasonably well. It is advisable therefore to combine or alternate two or more of these drugs. Where drug-sensitivity tests are available, which indicate the particular efficiency of either one or more drugs, these drugs should of course be used. No commercial vaccines and sera are available, but some success has been reported with vaccines made from Salmonella isolated from birds on the affected premises. These "auto-genous vaccines" are said by their advocates to be helpful in controlling outbreaks where the infection is established. The most important factors for prevention are cleanliness, care in the choice and origin of foodstuffs, vermin-proof premises, isolation of new stock and all stock after visits to shows, and the avoidance of buying any but healthy birds, no matter how much of an asset their possession might appear to be.
Other Salmonellae and Related Bacteria of the Gut. (Salmonella pullorum and S. gallinaram):
These are both pathogens of poultry and only affect a relatively small proportion of the birds with which we are mainly concerned. Most species appear to be resistant to pullorum disease and fowl typhoid (S. gallinarum infection), but canaries, parrots and some finches in particular can become infected occasionally. Reports are few and signs differ so much between outbreaks that no purpose would be served by listing them. The symptoms are very similar to those described for paratyphoid above, and bacteriological examinations are essential for an accurate diagnosis. Paracolon infections are even less common, the bacteria being distinguished by their biochemical properties rather than from the disease which they produce. Eseheriehia coil Coliform organisms, of great importance in calves, pigs and several other domestic mammals, are closely related to Salmonella. They are mostly normal inhabitants of the guts of healthy animals. A few strains are capable of causing disease in cage birds, especially when introduced into a different part of the body, for example, the oviduct, or abdominal cavity. It is possible that some underlying illness-such as chilling or a viral infection--enables Escherichia coli to gain access to these sites. In cage birds E. coli may give rise to a septicaemia; an inflamed oviduct associated with egg-binding or retained egg material; peritonitis; pneumonia in association with a failing circulation or aspergillosis; septic arthritis such as "bumble foot", and chronic air sacculitis. The organism is seldom discovered until necropsy is performed and bacteriological examination carried out. Diarrhoea or sudden death are often the only signs with septicaemic and peritoneal infections; young, previously weakened birds are most likely to succumb. Canaries, pigeons, quail and budgerigars are among species liable to be infected. E. coli is not a normal inhabitant of budgerigars' intestines and the finding of this organism, even in the droppings from apparently normal birds, should be looked upon with suspicion.
TREATMENT: When there are surviving, ailing, birds, the tetracyclines, furazolidone, or sulphonamides are most likely to be effective.
Pasteurellosis, Avian Cholera, or Haemorrhagic Septicaemia ( Pasteurella septica; P. avium or P. multocida infection):
Infections with Pasteurella septica occasionally occur in cage and aviary birds. The disease may occur either in epidemic form or sporadically. Some birds may remain carriers, shedding a few bacteria in nasal discharges or droppings for at least a year. As with other infections, external parasites and flies are of importance in infecting a hitherto clean establishment. Vermin, including wild birds contaminating the aviary with droppings, are probably a more dangerous source. Transmission occurs by inhalation of infected material in the form of water droplets or dust and by eating infected food. Probably all avian species, including poultry, gamebirds, waterfowl, some birds of prey, pigeons, and numerous species kept as cage birds or in zoological gardens are susceptible to some degree.
CLINICAL SIGNS: The pattern of disease varies. Multiple rapid deaths with few warning signs may occur three to ten days after introduction of the infection. Sometimes the illness may last a few days and show a wide range of clinical signs, while a residual group of birds which are sickly may survive and become carriers. When a bird actively shedding bacteria is introduced into a "clean" aviary the mortality is likely to be high and can approach 100 per cent. A previously fit bird may suddenly become quiet and depressed and sit motionless on the perch or floor. Within a few hours the depression deepens, the eyes close, feathers become fluffed up, the bird becomes unsteady on its feet and collapses. Before death, fluttering or convulsions may be noted, or the bird may stiffen, throw back its head, or possibly utter a squeaking sound and become limp. Rapid breathing is frequently seen in the early stages. Death can occur during flight, or while eating or scratching, without being preceded by any signs of malaise. When birds become infected later in an outbreak, and in more resistant individuals or species, the symptoms are clearer. Again, there is a degree of listlessness, shivering, and huddling. There may be pasty, fawn, or yellow droppings and sometimes rattling respiratory sounds, sneezing and sticky nasal discharges. The feathers around the vent, eyes, and beak may become matted. Appetite may persist, at least until late in the disease, and the thirst is also often unaffected. The droppings may become blood stained due to ulceration of the intestines. Death in this type of the disease is not inevitable and survivors tend to show signs of the chronic type of the infection. The chronic disease is characterized by marked loss of weight, moderate loss of bodily activity and appetite, swelling of the abdomen, lameness and swelling of the joints, and in some cases scaly or crusty lesions on the un-feathered parts of the head. Diagnosis depends on isolating the causal bacteria from blood or other tissues of a dead or sick bird. Blood-testing for Pasteurella antibodies is not yet reliable.
TREATMENT AND PREVENTION: Vaccines have not yet proved effective or safe. Dead, chemically treated Pasteurellae as used in vaccines are poor stimulators of antibody production. When an infectious disease such as pasteurellosis is suspected, remedial measures should be applied at once. Sulphonamides are the most effective drugs, particularly sulphadimidine. The antibiotics, except streptomycin which is too toxic for most species, are generally much less effective than sulphonamides both in lowering mortality and in checking the occurrence of the more chronic stages. Treatment must be continued during alternate weeks for at least six weeks to enable a reasonable check to be made on the disease. Severely ill birds, those with chronic nasal discharges, intermittent diarrhoea, and birds showing any signs of malaise should be treated in isolation if very valuable, but preferably killed and burnt. If the general principles of good husbandry are observed, in particular strict hygiene, the risk of introducing this disease into a collection will be minimized.
Pseudotuberculosis ( Yersinia pseudotuberculosis or Pasteurella pseudotuberculosis infection):
Pseudotuberculosis, so named because it produces yellowish or whitish, tuberculosis-like lesions in various tissues during the later stages of the disease is primarily a disease of birds, rabbits and rodents. It is not uncommon in monkeys and may be more common in man than generally realized, because it produces symptoms resembling appendicitis. Numerous species of mammals and birds are susceptible. The disease tends to arise sporadically, infecting one or two individuals, rather than whole aviaries of birds. The disease was first reported in the canary and this together with turkey, is the species most commonly and severely affected. The infection also occurs in pigeons, sparrows, finches, toucans, members of the Corvidae (crow family) and gamebirds. The organisms are usually introduced into the body via the alimentary tract, or occasionally through skin wounds. The disease begins as a septicemia which is very short lived and need not be apparent clinically. During this brief period the organisms can be isolated from the blood. In a few cases, especially with canaries, death may occur during this phase. More often, the infected bird survives a little longer and many of the bacteria are killed in the circulation, whilst others thrive and become localized in the liver, spleen, kidney, lungs, gut wall or under the skin, producing the characteristic cheesy masses or nodules.
CLINICAL SIGNS: The incubation period between infection and development of clinical signs, varies from two days to two weeks. Short of unheralded death, the earliest signs are not distinct, being similar to any septicaemia with depression, fluffing of feathers, panting and diarrhoea including watery urate excretion. Those birds with a more chronic form of the disease show dullness, loss of weight, ruffled plumage, intermittent diarrhoea or occasionally abnormally hard droppings. The breathing may at times also be labored. Loss of weight may extend to emaciation, this being one of the "going light" diseases of cage birds. As depression deepens, appetite falls sharply. The chronically affected bird is reluctant to move and, if hustled, may show a lameness or unsteady gait, marked weakness, or even appear paralyzed, according to the tissues mainly involved.
TREATMENT AND PREVENTION: Broad spectrum antibiotics as indicated by sensitivity tests and given by injection, may help to reduce losses. No really satisfactory treatment is available, however, and no reliable vaccine has been produced. The disease is extremely difficult to prevent because it is carried by many species of free-living birds and rodents, which may contaminate both the quarters and the food.
These small, round bacteria, which tend to form chains, are capable of causing abscesses, infecting wounds and producing valvular disease of the heart. They are less important in birds than in mammals. Birds which may become infected occasionally, include canaries, various finches, sparrows, and parrots. The infection enters via wounds and probably the respiratory or alimentary tracts.
CLINICAL SIGNS: The diseases caused by Streptococci in birds may be localized infections of repeatedly injured or pecked wounds, septic arthritis known as "bumble foot" or egg peritonitis. Generalized systemic or septicaemic illness may also occur. Septicaemia is the spread of infection throughout the body by the blood stream when the Streptococci are liable to cause death within 24 hours. The body temperature rises 2-4°F., and panting, fluffing of feathers, huddling, gaping, and depression may be observed 6 to 12 hours before death. At necropsy all the internal organs are congested, being a dark, purplish red in colour. They are also swollen, and samples of blood are found to be rich in Streptococci. The losses, in an outbreak may sometimes be high, especially in canaries. In some birds the depression is replaced by nervous stimulation, the birds becoming excitable, jumping at a sharp sound, flash of light, or quick movement, and flying or blundering wildly against the bars of the cage or the aviary. Convulsive fits, with complete inco-ordinafion and nervous derangement may lead to self-inflicted damage, particularly to the head. For this reason haemorrhages over and within the cranium may be seen in this form of the disease. These hemorrhages, which are also found elsewhere in the body, are more likely to be the result rather than the cause of the inco-ordinated activity. In cases of rapid death, there is the possibility that it is due to streptococcal waste products or toxins which are produced outside the body in stale food (especially egg food) and then eaten. The bacteria may also be eaten and digested, and the toxins absorbed. Sometimes a more prolonged, chronic or gastrointestinal illness is seen. This takes the form of loose droppings of various coloration, occasional regurgitation, progressive and extreme loss of weight and dull plumage. During the course of one or two weeks canaries may develop a greenish diarrhoea. The bird loses weight and develops a preference for soft food. The body temperature slowly falls and is markedly subnormal shortly before death. Affected birds often continue eating until death is imminent, which may be preceded by twitching or other nervous signs. Although muscle wastage is severe, the abdomen is usually enlarged. The congested intestines and other organs give rise to a purplish coloration which is visible through the abdominal wall. Differential diagnosis includes other bacterial and viral infections and poisoning by organo-phosphorus and other compounds. The disease therefore is virtually impossible to diagnose without recourse to bacteriological examination.
TREATMENT: In an isolated case, it is unlikely that the cause will be recognized at least until necropsy and laboratory examinations have been carried out. It is inevitable therefore, for treatment to be empirical, as is so frequently the case when treating single sick birds. When a series of losses occur, it is essential to submit carcasses for necropsy and bacteriological examination irrespective of which disease is suspected, so that treatment can be placed on a more secure, scientific footing. Theoretically, streptococcosis should respond well to antibiotics, because the bacteria are sensitive to most antibiotics when grown in the laboratory. Subject to laboratory recommendations, penicillin and the tetracyclines are most likely to be effective. The best route of administration depends on the drug to be used, the species and other factors. Good nursing, moderate warmth, a preliminary gentle laxative and an easily digested diet are essential.
CLINICAL SIGNS: Staphylococci, like the Streptococci, do not often produce purulent lesions in birds. Wounds most usually infected are those which are repeatedly pecked or knocked by the bird, especially on the breast, cere, bastard wing and eyelids. Foot lesions are commonly infected ("bumble foot") and also the most likely to develop pus formation. Joints are the characteristic sites for staphylococcal infections although the route by which they become infected is not always apparent. When one or both hock joints are involved, it is probable that infection arose through the skin in the region, but when several joints are affected it implies that the organisms were previously circulating in the blood and later became localized in the joints. Such a form of arthritis usually weakens the bird, causing loss of weight and eventually death. Staphylococcal arthritis of the feet or legs causes lameness and usually swollen joints. Eventually the bird can only shuffle on its hocks and beak. The hocks and plantar surfaces or undersides of the toes are the most common sites, but any joint of the legs, wings, and even the spinal column can be involved. Swollen joints are painful when squeezed or manipulated. The "joint oil" or synovial fluid instead of being small in quantity and a clear, straw-coloured, slimy fluid, increases in amount and becomes opaque, filled with pus and later cheese-like in consistency. The circumstances in which staphylococcal arthritis can occur are partly managemental such as the use of coarse sand paper for cage floors, rough perches and hard, rough, concrete floor for aviaries. In outside aviaries frost bite may be a predisposing cause. Similarly birds with bone diseases and other affections causing partial paralysis of the feet or limbs are most likely to be affected, as well as those showing general weakness and debility. This is because such birds tend to spend a lot of time on the floor; minor abrasions and scratches easily occur and these are invaded by ever-present organisms. Eventually the affected joints fill with scar tissue, further restricting movement, and distortions of the limb due to tendon contraction result. It is usually adult and middle-aged birds which become affected and those with long toes and legs such as wading birds. These and various other semi-aquatic species when kept in captivity are particularly prone to arthritis. Indeed it is one of the hazards of rehabilitating previously oiled sea birds such as guillemots and razorbills. Staphylococcal infection of the air sacs occasionally occurs if they have been directly exposed to the outside air by external injury, the organisms sometimes being associated with other bacteria and fungi such as Aspergillus.
TREATMENT AND PREVENTION: Treatment with furazolidone or tetracyclines may limit the infection, especially by controlling infection of internal organs, but the arthritis is rarely cleared by such treatment. Incising the joint, scraping, and washing out the exudate with saline solution and packing it with an appropriate antibiotic and compound containing a digestive enzyme is more likely to succeed. Such treatment must of course be carried out by a veterinarian because it is very easy to cause permanent damage to joints. Staphylococcal infections are nearly always sporadic and, although the organisms are ubiquitous, healthy, active stock is unlikely to be troubled. The infection can usually be avoided by good management and nutrition.
Erysipelas (Erysipelothrix insidiosa or E. rhusiopathiac Infection):
The bacteria which cause erysipelas are widespread and occur in soil. The disease occurs only occasionally in birds. The pig and turkey are its most usual hosts among domesticated ' animals and outbreaks in unvaccinated pigs are often severe. Rats and biting arthropods have been incriminated as sources of infection. In pigs, the bulk of outbreaks are at the height of summer, so it is believed that warmth encourages rapid multiplication of the organisms in the soil. Many species of birds have been found to be susceptible to erysipelas, although susceptibility varies considerably. Most cases other than turkeys, have been described in gamebirds and pigeons, the latter being especially susceptible to this disease. It is probable that infection is through injuries to the skin or mucosal surfaces, particularly as the disease is commonest in male turkeys following fighting. Cage birds are not commonly affected, but should an outbreak occur, losses may be as great as 25 per cent.
CLINICAL SIGNS: These include dullness, general weakness, lack of appetite and greenish-yellow, loose droppings. As depression deepens, affected birds huddle with "head-in-chest", eyes closed and tail down. There may be accentuated chest movements. In species with fleshy appendages of the head, these tend to fill with blood or oedematous fluid. Death occurs in 1 to 4 days according to species and individual susceptibility. Conjunctivitis has been observed as a symptom of erysipelas in budgerigars, the birds being reluctant to fly and preferring to move around the aviary by clinging to the wire netting and other objects by means of their beak and feet. Diagnosis can only be made on post-mortem and bacterio-logical examinations. Recovered birds develop an immunity to further attacks and the antibodies representing this immunity can be measured by blood (agglutination) tests.
TREATMENT AND PREVENTION: Erysipelas is fortunately quite responsive to treatment. Penicillin, either given twice daily as the soluble salt of calcium or in a longer acting form should rapidly cure most cases. All birds which have been in contact should also be treated. When response to this treatment is poor or doubt exists as to whether other infections are also present, then the tetracycline antibiotics can be used. Erysipelas vaccines and serum are available. The vaccine has proved of practical value in preventing outbreaks in turkeys where annual occurrences are common. The serum, whilst not being particularly effective in the treatment of sick birds, is of value for the protection of other birds on affected premises.
Listeriosis or Listerellosis (Listeria or Listerella monocytogenes Infection:
This organism only occasionally causes disease in cage birds, although it has been reported in other birds and mammals in widely separated countries. In canaries, outbreaks with quite high losses have been reported in both the Old and New Worlds.
CLINICAL SIGNS: These range from sudden death in adults as the result of septicaemia, to a wasting disease in young birds. Occasional cases show central nervous system involvement. Diagnosis depends on bacteriological examination and isolation of the organism from various organs, especially the brain.
TREATMENT: Broad spectrum antibiotics are likely to be the most effective drugs.
Tuberculosis (Mycobacterium Infection):
There are three main types of tubercle bacillus (Mycobacterium) in warm-blooded animals: bovine, human and avian. Although the avian type occurs frequently in various species of mammals, the mammalian types are very rare in birds. However, parrots and other larger psittacines, such as macaws, are susceptible to both the human and bovine tubercle bacilli as well as the avian, whilst ornamental game birds are very susceptible to the latter. Budgerigars, canaries, and the hardier finches are fairly resistant, possibly due to their more complete adaptiveness to domestication. Tuberculosis is a chronic disease with a slow, insidious stage of development during which the bird is apparently normal or only slightly off-colour. In a well nourished, active bird this stage may pass with no further signs of illness. In such cases the tubercular lesions are walled off by scar tissue and become inactive. After many months, the organisms in the lesions die; but if another disease or stress challenges the bird in the meantime, the disease may again flare up. Birds which have been recently imported and which have under-gone stresses on their voyage including change of diet are most likely to succumb to the disease. Imported foreign birds are usually accustomed to very different climatic and other conditions from those they meet at their destination. Overcrowding, lack of sunlight, increased or decreased humidity or poor hygiene are all predisposing factors. Aviaries previously used for poultry, rearing pheasants, or waterfowl should never be used, as the disease is relatively common in these groups. Wild birds are often infected, especially woodpigeons in Europe and Great Britain. If possible therefore, aviaries should be protected from the droppings of wild birds.
CLINICAL SIGNS: The main signs are pallor of mucous membranes, loss of weight, listlessness, usually diarrhoea, bedraggled, fluffed-up and dull plumage. Breathing often becomes rapid as the disease progresses, the eyes appear sunken, the bald parts of the head may be pale or greyish, and the sharp edge of the breast bone can be easily felt. In parrots, skin lesions appear as dry, flaking swellings, or raised ulcers mainly on the head. The picture is characteristically one of "going light" in bird keepers' terminology and is similar to any type of chronic, debilitating illness. Although tuberculosis may probably attack birds of all species, especially adults, it must not be assumed that every bird "going light" over a period of weeks or months is tuberculous. Other chronic diseases, especially pseudo-tuberculosis and also pox, leukosis, heavy parasite burdens, aspergillosis, abdominal tumors, arthritis, gout and foreign bodies in the alimentary tract are all capable of causing slow debility with additional signs such as diarrhoea, skin lesions, lameness and anaemia. Although post-mortem findings may be highly suggestive of the disease, only microscopic identification of the characteristic organisms and other bacteriological examinations really confirm the diagnosis. At necropsy, tuberculosis is easily suspected by the presence of whitish nodules or tubercles scattered throughout the internal organs, but more especially the liver and spleen. Without bacteriological examination it can be easily confused with pseudotuberculosis.
TREATMENT AND PREVENTION: Treatment should not be attempted because the risk of fresh cases occurring is too great and the response to drugs is too poor to warrant therapy. Added to this is the risk to other animals and sometimes to man. The tubercle bacillus in addition to being relatively slow in producing disease is also a moderately resistant organism, capable of living for considerable periods in carcasses and other infected material. All birds readily become infected by pecking at or eating contaminated matter and therefore diseased carcasses, droppings, and other material should be incinerated. It is virtually impossible for practical reasons, to prevent the disease because infected birds or mammals are capable of shedding the organisms long before they become obviously ill. In one case infection and death of a parrot occurred long before the source of the disease was detected--the bird's owner. Tuberculin testing in order to detect the disease before clinical signs are apparent has not been developed for cage birds, but can be used for the domestic fowl. It may be tried, however, in larger species with fleshy head structures suitable for injection, such as ornamental gamebirds.
Spirochaetosis (Spirochaete Infection):
This group of blood-borne organisms, which swim actively, is related to the causal organisms of syphilis and Weil's disease in man, and has occasionally been met with in birds other than the domestic fowl.
CLINICAL SIGNS: The organisms are transmitted mainly by ticks from one bird to another, being introduced into the bloodstream by blood-sucking ticks. A spirochaete infection therefore usually indicates a tick infestation, and sometimes vice versa. Not all spirochaetes, however, are particularly pathogenic. In the more pathogenic species the incubation period is between three and seven days. In the early stages, during which period the organisms multiply in the blood-stream, signs, of fever, panting, thirst, fluffed-up feathers, depression and diarrhoea are seen. Later, coma and death may occur. Survivors thrive poorly. Isolated cases are liable to occur in birds recently imported by air from affected tropical or warm regions.
TREATMENT AND PREVENTION: Penicillin has been found of some use in treatment of the disease in the fowl. It is also necessary to treat the affected bird for ticks and take steps to prevent further infestation.
Mycoplasmosis (Mycoplasma or P.P.L.O. Infection):
Mycoplasma organisms have similarities both to bacteria and to the organisms known as rickettsiae. They are primarily pathogens of cattle in which they produce a disease known as pleuropneumonia, hence the abbreviation P.P.L.O. which stands for pleuropneumonia-like organisms. Identical or very similar organisms affect poultry, turkeys, gamebirds, pigeons and various species of cage birds. The organisms are sometimes associated with chronic disease of the respiratory tract. They occur in nasal and ocular discharges associated with infra-orbital sinusitis, and also in congested and oedematous lungs of pigeons, gamebirds and occasionally budgerigars, parrots and canaries. Both nestlings and older birds can become clinically affected, although youngsters are most susceptible. It is probable that transmission to young stock occurs from the parent through the egg; but opportunity for infection directly from parent to nestling is much more important, because the organisms can be transmitted by inhalation of infected water droplets in the air. Overcrowding encourages transmission.
CLINICAL SIGNS: Infections are nearly always chronic and result in gradual debility and lowered susceptibility to other organisms, some of which may be present in normal healthy birds. Before clinical illness is apparent, stresses such as chills, exposure to draughts, or in the case of racing pigeons an exhausting flight, may result in the flare-up of an underlying infection and produce obvious illness. In racing pigeons this is reflected first in poor performance. Nasal and ocular discharges of various types, rattling respiratory sounds, partial closure of one or both eyes, depression, reduced appetite, progressive loss of weight, and "sneezing" are all signs which may be seen. In young birds and in some adult budgerigars, little is observed except for a day or two of slight dullness which may be followed by death. The infection can be endemic in an aviary with little evidence of its presence except for a few cases of vague respiratory signs, "one-eye colds", sinusitis or debility. The disease is essentially an inflammation of mucous membranes resulting in congestion of blood vessels, swelling and discharges which may be watery at first and later become mucoid or cheesy. Mortality is usually low. Diagnosis can only be made by identifying the causal organism in nasal or ocular discharges, nasal scrapings or air sac material in the case of dead birds. The main difficulty, however, is that the organism may be associated with bacteria or viruses and may not necessarily play the primary role in the production of disease.
TREATMENT: Treatment is often unsatisfactory. In most cases the illness is mild or vague and laboratory confirmation is unlikely to be sought until a death occurs. Response to antibiotics is rather poor, but some success can be obtained by using tetracyclines given by subcutaneous injection or by nasal drops. Such treatment sometimes reduces the discharges and usually checks the loss of weight. In advanced cases, the thick exudate which accumulates in the airsacs, nasal chambers, sinuses and beneath the eyelids remains relatively unaffected. Eye and sinus lesions can, however, be treated by fomentation and by local applications of oily or water-based antibiotic creams and curettage.
Other Bacterial Infections:
Only the most important infections have been dealt with above. But there are several others which have been reported in birds. Some of these are omitted because they are beyond the scope of this article being mainly diseases of domestic poultry or intensively reared game birds, e.g., in-fectious coryza caused by Haemophilus gallinarum, vibriosis due to Vibrio metchnikovi infection, vibrionic hepatitis, goose influenza and ulcerative enteritis of quail. Other diseases are rare and poorly documented in birds, such as anthrax, Edwardsiella tarda infection, Corynebacterium ovis infection and pseudomoniasis (Pseudomonas aeruginosa infection). These diseases can only be diagnosed after death with the aid of bacteriological and histological examinations.
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Hamilton & District Budgerigar Society Inc.