This disease is associated with many species of birds, but is predominantly found in songbirds. In songbirds it is often referred to as ‘thick liver disease’. The liver becomes enlarged and round. Because the skin of small birds is so thin and transparent, the liver can actually be seen through the skin of the mid-abdomen in the form of a large dark spot.

The disease is caused by Atoxoplasma serini, a single-celled parasite closely related to coccidia. In contrast to the coccidia, which primarily cause problems in the intestines, A.serini is found in more parts of the body. It starts in the blood cells and spreads to other organs, including the liver, spleen and intestines.

Adult birds can be carrier of the parasite while themselves showing little or no signs of illness. The faecal matter does, however, contain oocysts (small egg-like cysts) allowing them to infect other birds and their own young.

Young birds are more prone to illness after infection. The symptoms are difficult to recognise. The birds lose some of their weight, ruffle into a ball and can have diarrhoea. The enlarged liver can often be seen through the skin as a dark spot. Young birds can become acutely sick and severe infection can cause a death rate of up to 80%.

Treatment is complicated because the parasite infests areas where there is little to no access for medication (for instance in tendons and joints). After stopping medical treatment, it's quite possible that the disease comes back because the inaccessible parasites multiply again. Infection occurs when the bird ingests oocysts. The sick birds then discharge them with the faeces.

Diagnosis

Diagnosis is difficult as sick birds do not have the oocysts in their stool every day. As a result, a faecal examination will not always result in an accurate diagnosis.

The best way to find the pathogen is by examining the liver and spleen of the bird after it has died. The parasites located in the organs can be detected under a microscope. In addition, the condition of the deceased bird can also provide a strong suspicion of the disease.

Therapy

Medication is used to kill the parasites, although the problem still remains that birds can easily become infected again and it is difficult to eradicate all parasites. One treatment method that has seen positive results is treating the birds 2 days a week, then waiting for 5 days before recommencing treatment. This is repeated for a period of 2 months. This seems to have the greatest effect on diminishing the influence of the parasite.

In addition, proper hygiene in the enclosure is very important. This prevents the birds from being able to ingest too many oocysts and reinfecting themselves. Despite the extensive treatment method, it is still very difficult to entirely get rid of the parasite from an aviary.

Campylobacter jejuni is a bacterium found in many different bird species. Parrot species can become infected with the bacterium, although problems are rarely seen. Finches and canaries are much more sensitive. Problems can also occur in poultry and pigeons. Campylobacter has a greater chance of causing illness if another infection is already present in the system.

Birds are infected by ingesting the bacteria through the beak. The bacterium causes inflammation of the liver. This results in the birds becoming lethargic and they stop eating. Additionally the intestines and pancreas can be affected, preventing the birds from being able to digest their food properly. They have yellow or light-coloured diarrhoea, and can lose weight rapidly.

Especially finches and canaries, and particularly the young, can die in large numbers. Birds that have a healthy immune system can overcome the bacterium themselves.

Diagnosis

The symptoms alone can provide a strong indication of the disease. Under a microscope the bacteria can be directly identified after use of and appropriate stain for campylobacter The swab can be taken from the faeces or from the organs of deceased birds. The culture of Campylobacter is more difficult than other bacteria. Special plates are needed as well as an environment with a limited amount of oxygen.

Therapy

Antibiotics are used to treat the disease. Birds are easily reinfected through the environment and a return of the bacterium, and therefore the disease, is often seen after the antibiotic treatment has finished. For this reason, it is vitally important to maintain a high standard of hygiene in the aviary.

As with all bacterial infections, it helps to make sure the intestinal flora is well balanced. This can be aided further by adding a probiotic to the feed or water. An infection with a pathogenic bacterium will then have less chance of causing illness.

One of the most common fungal species to cause problems in birds is Candida albicans. Candida is a yeast, this is an organism that consists of a single cell and multiplies by dividing itself. If the conditions are right, Candida can multiply at an explosive rate. Candida is quite common in the digestive tract of healthy birds. It forms part of the natural flora. Sometimes however, the balance in the intestines can be disrupted, for instance if the normal intestinal bacteria are killed during treatment with antibiotics. This enables Candida to multiply without restraint and cause disease. In young birds, yeasts will be more easily pose a threat because of the immaturity of their immune system.

The severity of sickness depends on the overall health of the bird. Most problems with Candida occur in the digestive tract.

One of the most well-known diseases caused by Candida is candidiasis in the crop (‘sour crop’). It is most commonly seen in young birds. The crop is usually the only part of the digestive tract affected, although infection can also occur extend to the glandular stomach and gizzard. If infected with Candida, the cells of the mucous membrane in the crop die off. White plaques of dead mucosa then appear. Also, a whitish to clear mucous forms in the crop.

Candisiasis causes regurgitation, delayed crop emptying, lethargy, loss of appetite and sometimes a completely blocked crop in young birds. Adult birds can have a swollen, mucous-filled crop. The plaques of the inner lining can complicate the crop emptying.

Besides problems in the crop, Candida can also affect the inside of the mouth. White plaques can also form here, covered in mucous. Candida can also cause infections of the trachea in parrots and related species. Particularly after long spells of antibiotics use (for instance used to treat a bacterial infection of the respiratory tract), Candida can emerge in the absence of competition.

Infections in young birds with Candida are often the result of poor hygiene when preparing the birds' formula. Formula that has been standing in the open for some time can contain large numbers of yeasts. Fruit that has been out for a long time can also infect birds.

Diagnosis

The symptoms and background history are usually enough to suspect Candida. Material taken from a crop swab can be microscopically examined. The yeast can then be identified after staining. Because they can normally be found in small numbers, finding low numbers of yeasts does not offer 100% proof that the Candida is the main cause of illness. Clinical candidiasis in the crop often reveals large amounts of yeasts that are seen to be budding.

Treatment

An anti-yeast agent is an effective treatment method. Besides combating the yeast infection, it is also important to look for the reason of the infection. The yeast usually only has the opportunity to cause illness after the bird is weaker because of other factors, such as an infection or poor nutrition.

This disease is caused by a bacterium. The chlamydia bacterium can only multiply inside the cells of its host. The bacterium is found in the droppings and in the nasal and ocular discharge of infected birds. In pigeons it is also found in in the crop milk. Birds can become infected in several ways, for instance through feather dust and dried-up droppings. They can inhale the bacterium or ingest it through the beak. Young birds can also already be infected by the parents while still inside the egg.

Different strains of chlamydia cause different problems. Also, a strain that is fatal for a particular bird species may only cause very mild symptoms in another species. If the bacterium is ingested by a bird, it depends on the immune system of the birds as to what the consequences are. The bacterium can only survive inside a cell of the host. Once it has nestled itself inside a cell, it becomes very difficult for the immune system to get rid of the bacterium. Birds can then become carrier of the bacterium.

It is quite common for a bird to become infected with a strain of the bacterium that hardly causes sickness in that particular species. The body makes antibodies to fight the bacterium, but the birds can shed the bacterium and infect their surroundings. Throughout this time, the bird may show no sign of illness at all. By spreading the bacterium, these birds become a danger to young birds of the same species, but especially to birds of other species. For birds of other species, this strain of bacteria might be extremely pathogenic. Carriers that show no symptoms may become sick themselves in times of reduced resistance or in case of other infections.

Young birds that are infected by a particularly pathogenic bacterial strain can acutely become seriously ill. They become lethargic, have conjunctivitis, start hawking, have respiratory difficulties and have diarrhoea, which can be green or grey and watery. They often die within 8-10 days and those that do survive usually have abnormalities in the plumage.

Birds infected with a bacterial strain to which they are less sensitive can develop a more chronic illness. They lose weight, have greenish diarrhoea and sometimes contract conjunctivitis. Members of the parrot family can also show nervous symptoms, such as trembling, epileptic-like fits and stargazing. Pigeons often show conjunctivitis and nasal discharge. The symptoms can be nondescript and are often not recognised. Birds that do not receive treatment can die within a matter of weeks.

No immunity is built up by birds that survive the illness, which means they are just as susceptible as birds that have never come into contact with the bacterium before. Therefore it is impossible to vaccinate against this disease.

Diagnosis

Because the chlamydia bacteria can only survive in the cell of the host, they are difficult to culture. These days, presence of the bacteria is determined through DNA testing. This can be a blood test or a cloacal swab. Often these tests are combined, to maximise the chance of finding the bacterium.

Treatment

Antibiotics are used to treat sick birds. These can be mixed through the feed or drinking water, whereby it is important to make sure the birds eat or drink enough. Infected birds will continue to spread the bacteria for a few days after the treatment begins as it takes a while for the antibiotics to have sufficient effect.

Another treatment method is through intramuscular injections. This method stops the birds from spreading the bacteria within 24 hours.

Long-term treatment is necessary because the bacteria are located inside the cells of the bird. This makes it difficult for the antibiotic to reach the bacterium. Some birds remain a carrier despite long-term treatment. The disease can reappear in periods of suppressed resistance, for instance if the bird has another illness.

The bacterium is not only dangerous for birds, other animals and even people can also become infected. People who are infected with the bacterium show flu-like symptoms. If not treated, it can cause pneumonia or meningitis.

Escherichia coli (E.Coli) is a bacterium. It is commonly found in the intestines, but becomes a problem when it starts to supplant other bacteria. There are many subspecies of E. coli, each with its own pathogenic characteristics.

One of the most well-known diseases caused by E. coli is colibacillosis, or sweating disease. This disease is seen in young psittacines, but more often in canaries. The E. coli bacterium causes illness by producing toxins. These toxins then cause the intestinal cells to expel large amounts of fluid, liquefying the contents of the intestines and giving the infected birds watery, slimy diarrhoea. This quickly leads to the birds dehydrating and losing valuable nutrients, followed in most cases by death. The nests of the young become very wet (hence the name sweating disease) because the parents aren't able to clear away the watery droppings.

In older birds, the toxins can also affect other organs, as well as the intestines. The birds may start drinking a lot more water (when the kidneys are affected). They start to have trouble walking or flying (if arthritis is involved). Chickens can get an infection of the ovaries and fallopian tubes. They can die if the infection spreads to the abdominal cavity, causing peritonitis.

Coli is quite common in pigeons in combination with an adenovirus. It is commonly believed that the birds are first infected with the virus. The resulting low resistance then allows the E. coli bacteria to enter the body. These illnesses combined make the animals lethargic, have diminished appetite, they often drink more and have thin, slimy droppings. Because of the damage to the liver, the stool can also be a green colour.

The disease can infect large groups of young birds. Among adult birds it's often the ones already weakened that are mainly affected.

Diagnosis

E. coli can be cultured from the droppings. If the disease has spread through the body, the bacterium can also be cultured from other organs, for instance the liver.

Treatment

The bacterial infection is treated with antibiotics. If treatment does not have the desired effect, an antibiogram can be made. This entails establishing which antibiotics work best against the E. coli that is causing the problems by culturing and performing a sensitivity test on the cultured bacterium.

Pigeons that have a combined infection are also treated with antibiotics. After the E. coli infection has been fought successfully, the pigeon then has to combat the virus itself.

This disease is seen mostly in species of parrots and parakeets. The disease is considered to develop after infection with the bornavirus. Although it is most common in young birds, older birds can also develop the disease. The clinical signs are caused by damage to the brain and to the nerves of the glandular stomach, gizzard and upper part of the small intestine.  The muscle activity decreases in these organs and the organs themselves stretch out and become weak.

Because of the diminished peristaltic activity of the stomach muscles, the food isn’t propelled to further sections of the gastrointestinal tract. Infected birds will start to vomit, undigested seeds can be found in the faeces and the birds become very thin and listless. The symptoms can occur within 3 weeks of being infected, although the signs are sometimes only noticed years after being exposed to the virus.

Besides the signs directly caused by the damage of the nervous system, birds are also much more susceptible to secondary infections. One problem is that the crop is filled for a long period of time due to the poor food passage to the glandular stomach. This can lead to ‘sour crop’ or candidiasis. Diarrhoea is another associated problem that can be seen, as bacteria or fungi can flourish in the weakened bird. They can multiply quickly because food doesn't digest well enough in the intestines, providing them with more nutrients than in a healthy bird.

In addition to the nerves in the gastrointestinal tract, other nerves in some bird species can also be affected. Birds can become weak in the legs if the spinal cord or the leg nerves are damaged. If the disease reaches the brain, birds can get problems with keeping their balance,  get a twisted neck and even become paralysed.

Diagnosis

There are several methods to detect the virus. DNA testing of the blood is one way of revealing the virus. Another method is to measure the antibodies that the bird produces as a result of the viral infection. The advantage of these tests is that they will also show the virus in birds that are not yet (visibly) ill. This can be very important in preventing the disease from spreading within an aviary or in the household. If a bird dies of the disease, a probable diagnosis can be made by examining the internal organs.

Biopsies can be taken from the muscles and the glandular stomach, which are then examined under a microscope. An assessment can then be made of the condition of the nerves. If these are absent in large part, the diagnosis can be made. In a deceased bird, this procedure is quite straightforward. A biopsy can also be obtained if the bird is alive, but this does give the added risk of general anaesthesia and an operation.

If the bird is still alive, radiographs can be made that will show an elongated, enlarged glandular stomach. If more radiographs are taken at intervals, it is also possible to detect if the emptying of the glandular stomach is delayed. Should this be the case, diagnosis is very probable, but not 100% certain. Other conditions or diseases may also show theses signs, for example tumours that partly block the entrance of the glandular stomach.

Treatment

At present, there is no known treatment for this disease. However, supportive treatment can help to improve the condition of the bird. This consists of removing any blockages. Thereafter, softer or liquefied food can be given to the bird, making the digestive passage easier. Pellets also tend to be easier for birds to digest than seeds. In addition to modifying the food, it is important to check whether the bird has any other infections. These also require treatment. Considering the fact that PDD is a progressive disease, prognosis is poor.

Different variants of the virus cause different clinical symptoms. Almost all bird species can be affected by one or more serotypes of the virus.

PMV-1/NDV

The most well-known strain of the type 1 virus is that which causes Newcastle Disease (NDV). This disease is widespread and has a direct effect on the economy. It is best known by its infection of chickens, but the virus can cause sickness or death in almost every bird species. Birds become infected by ingesting the faecal material of sick birds or from birds that spread the virus while not being sick themselves (carriers).

Severely pathogenic strains of the Newcastle Disease virus can cause sudden death without showing any previous sign of illness. Symptoms of the disease that are commonly seen are diarrhoea, not eating and respiratory difficulties. A slower course of the disease can cause symptoms in the chickens' nervous system, such as loss of balance.

PMV-1/Pigeon

Pigeons can also be infected by paramyxovirus type 1, but a different variant thereof. This is very similar to the virus causing New Castle Disease. After the pigeon ingests the virus, it will drink more, eat less, have diarrhoea and possibly regurgitate. Most typical are the nervous symptoms: their wings will tremble and they will become stargazers. Young pigeons can die as a result of the disease, adult pigeons can recover after 3 to 4 weeks.

In other bird species, the type 1 virus can cause a wide range of nondescript symptoms, such as conjunctivitis, respiratory problems, diarrhoea and nervous symptoms.

PMV-3

This variant of the virus mainly causes illness in songbirds and members of the parrot family. The first sign of infection in birds such as the Gouldian finch and other finch species are conjunctivitis, followed by a yellowish diarrhoea, difficulty eating and respiratory problems. Some of the birds infected will die while others can recover.

The most significant signs in parrots and related species are the nervous symptoms. These are identical to pigeons with PMV-1. In addition, the liver and kidneys can be affected and the birds can have diarrhoea.

Treatment and prevention

Pigeons can be vaccinated from the age of 4 weeks. This does not fully prevent the pigeons from becoming sick, but the symptoms are less severe and recovery time is reduced. There is no specific treatment possible for sick birds. Antibiotics may help to combat any secondary bacterial infection.

Birds showing serious nervous signs can have difficulty eating from the food tray. They will need supportive care by hand feeding them to prevent starvation. Birds can fully recover from the virus without any permanent effects. This all depends on the birds' resistance and whether or not any secondary bacteria have caused a concurrent infection.

Birds are susceptible to many types of parasites. Birds that are kept indoors and have minimal contact with the outside world are less likely to be infested with parasites than birds that are kept in an outdoor aviary. There can be many parasites present in or on a bird without you being able to detect any visible signs. Problems are often only noticed if the bird is feeling under the weather for some reason (associated illness, dietary deficiencies, etc.). This is when they can suffer from the presence of parasites.

Worms

Tapeworms

Tapeworms or cestodes reside in the intestines. They can be found in finches and members of the parrot family. If infected, the birds can lose weight and have diarrhoea. Infection can also take place without showing any signs. Because tapeworms require an intermediate host, they hardly ever occur in birds that don't come into contact with the ground or the earth. This is much more common with imported birds.

Roundworms

Roundworms or nematodes are found in the small intestine. The bird is infested when it ingests eggs with larvae inside. These then bury themselves in the mucous membrane of the intestine. There may not be any problems, but if heavily infested it can cause diarrhoea, loss of weight and poor growth. If there are large numbers of worms, they can in fact block the intestines entirely. Eggs are spread with the bird faeces. They can remain contagious in the environment for a long time. Birds that don't come into contact with faecal material of other birds or infected earth have very little chance of being affected.

Threadworms / Capillaria

These are thin worms that are found in the small intestine. They bury themselves in the inner lining of the intestine. Birds with Capillaria can have diarrhoea (sometimes with blood) or can vomit. Because of the damage to the mucosa caused by the Capillaria, the blood loss can also result in anaemia. The birds become pale and have very little energy.

Gapeworms (Syngamus trachea)

This worm nestles itself in the windpipe. It is most common in species of poultry and ducks. Young birds are most susceptible to this worm. Infection causes shortness of breath; the birds start breathing with an open beak and shake the head. If the inside of the windpipe is severely damaged, the blood that the animals shake out can appear around the beak. They can suffocate to death if the windpipe becomes blocked by infected dead tissue.

Diagnosis

Diagnosing a worm infection is performed by means of an examination of the bird stool. The With the aid of a microscope parasite eggs can be identified. If animals have died, the worms can be seen directly in the intestines during an autopsy (or in the windpipe if it concerns gapeworms).

Therapy

Worms can best be treated by using anti-worm medication specifically for birds. If the worms are killed, they can be seen in the stool.

In addition, it is very important to prevent further contamination. Birds have the best chance of avoiding infection if they do not come into contact with faecal material. Worm eggs also stay contagious for a long time in the ground or soil.  Another good method to minimise the risk of contamination is to clean the bird enclosure regularly.

Insects

Lice

Lice cause itchiness and poor condition of the plumage. The lice nestle themselves on the feathers, with their eggs (nits) stuck to them.

Diagnosis can be made by closely examining the bird, if necessary a microscope can be used for more precise examination.

Mites

Scaly leg mite / Knemidokoptes

This type of mite mostly causes problems in budgerigars, which often results in a so-called 'scaly face'. The bird's beak can become very large and deformed, the skin surrounding the beak (eyes and nostrils) can become thick and irregular. In other parrot species, the symptoms are usually limited to the head. The skin becomes thick and flaky and scars can remain after the bird has healed. 

With other bird species, such as chickens, it's the malformed legs that are most noticeable. Scaly grey lesions cause large flakes and the legs become thicker (scaly legs). Canaries can also have abnormalities on the legs as a result of infection. Large amounts of thickened skin build up, making it very difficult for the bird to walk.

If multiple birds are kept in the same enclosure, it is possible some birds are severely affected, while other show no signs of disease. One possibility is that certain inbred lines of birds are more susceptible than others.

It is also more common to see birds that show the symptoms after stressful periods.

Diagnosis

The diagnosis is often made based on the clinical signs. The mite can also be seen under the microscope. The mite is too small to be detected with the naked eye.

Tracheal mites / Sternostoma tracheacolum

These occur in canaries, finches and parakeets. The mite lives in the windpipe (trachea) and the air sacs. Depending on the severity of the infestation, birds can become short of breath, cough or sneeze, or even die of suffocation if very severely infected.

Diagnosis

In some cases, the mites can be seen in the windpipe by holding a bright source of light directly behind the bird's neck. The light shines through the tissue and the mites can be seen as small black dots at the level of the trachea. The eggs can also be identified when examining the faeces.

Feather mites

These usually cause few problems with the natural host. Problems start occurring when they infect a bird that has never been in contact with this mite before. Feather mites can also give problems when located on the skin, instead of the feathers, this is seen in cases of severe infestation. The birds start to itch and the quality of its feathers deteriorates.

Red mites / Dermanyssus gallinae

Are sometimes also known as chicken mite or poultry mite. These mites feed on blood and can cause anaemia with birds. During the day, the mites hide in the nooks and crannies of the enclosure. At night, when the birds are resting, they begin their attack. For this reason, diagnosis can't be made by examining the birds during the day. The mites can only be found on the birds at night and you can in fact see them with the naked eye.

Therapy against infections caused by insects

An antiparasitic medicine for birds can be used in treating insect infestation. One (or more) drops on the skin in the neck is often sufficient to rid the bird of parasites. In addition, the area the bird lives in must be treated. Using an effective anti-parasite spray is a proven method.

Unicellular parasites

Flagellates (Trichomonas, Giardia, Hexamites)

Trichomonas: see trichomonas / canker

Giardia

This parasite lives in the intestines. Birds do not necessarily show any symptoms. Infected birds excrete giardia parasite with their droppings. This means they can pass on the parasite to other birds. Birds showing signs of infection can have a rather smelly stool, slimy diarrhoea and can become very thin. Eventually, they can be very lethargic and stop eating. Because their physical condition deteriorates, it makes them susceptible to other diseases. If heavily infested, young birds can have poor growth or even die.

Hexamites

These parasites resemble Giardia, but are smaller. They also reside in the intestines. If infected, the bird can show mild diarrhoea that will not improve.

The parasite can be found in the intestines of healthy pigeons. They can cause problems if the pigeon becomes ill for another reason.

Diagnosis

The active stage of the parasite can best be seen in a very fresh stool sample (Hexamites and Giardia) or a fresh crop smear (Trichomonas). The moving parasites can be seen under a microscope. Once the stool sample/smear has cooled down, the parasites stop moving and are difficult to recognise.

The dormant stage of the parasites can also be found in the faecal material. These are called cysts.

Treatment

There are several anti-parasitic medicines available to treat birds that have these parasites. Unfortunately, resistance is a phenomenon that occurs more and more, especially in the case of Trichomonas. The medication can be given straight into the beak or crop, or it can be mixed into the drinking water.

Coccidia (Eimeria, Isospora, Atoxoplasma)

Eimeria and Isospora

A bird can be infected by these single-celled parasites without showing any symptoms. Other birds will have blood in the stool, listlessness, diarrhoea, will stop eating and, if severely infested, may even die.

Eimeria parasites are usually found in songbirds and the parrot family. Isospora parasites are mainly found in galliformes (fowl) and pigeons. It is a major cause of inflammatory bowel disease in these birds.

Animals become infected when ingesting water or feed that has been infected by faeces of other birds.

Diagnosis

The dormant stage of the parasite (oocysts) can be seen in the stool under a microscope.

Treatment

This can be done by giving the bird an anti-parasitic medicine in its drinking water or directly into the beak. It is also very important to prevent recontamination and to minimise the number of oocysts in the direct vicinity. The dormant stages of unicellular parasites (the oocysyts) are very resistant to most cleaning products. The surest way to kill as many cysts as possible is by using a high-pressure hose. Small parts of the cage or aviary, such as feeding trays and perches, can be put in boiling water for 15-30 minutes. This also kills the oocysts.

Atoxoplasma

See atoxoplasmosis.

This disease is caused by a circovirus and is most commonly diagnosed in members of the parrot family. Birds are infected by ingesting the virus through the beak or by inhalation. The virus particles are often found in the droppings and feather dust of infected birds and are highly resistant to cleaning agents. The disease manifests itself in different forms.

There is the acute form. This is most common in birds that have already been infected at a young age. The first signs of the disease are seen when the young birds lose their down feathers and start developing adult plumage. The growing feathers die, break, bend or bleed from the shaft. Feathers can also fall out prematurely if they do grow to full length. Besides abnormalities in feather growth, birds can also experience lethargy, loss of appetite and delayed emptying of the crop. They can die within one to two weeks.

The chronic form of PBFD causes the plumage to deteriorate. The virus influences the development of new feather. The first abnormalities are usually seen in the down feathers, because these are continuously moulting. The large flight feathers and contour feathers become more deformed with each moulting period. The feathers that do come through stop growing prematurely. They may have an abnormal shape or are fragile and break easily. It is also possible that only the colour of feathers show abnormalities in the first stage. If a bird lives with the disease long enough, it will eventually become bald.

Problems can also affect the beak; it may elongate, break and the mucous membrane in the oral cavity may become infected or the cells may even die off.

Besides the effects of the virus on the plumage and the beak, it also causes a weakened immune system. As a result, infected or sick birds are much more susceptible to a range of other infections and will become sick earlier in less than ideal conditions.

In addition to birds with obvious signs of the disease, there are also those that are carriers. These birds contain the virus and can excrete it, infecting other birds. They may show no signs of the disease themselves. They can, however, develop the disease in case of a malfunctioning immune system. For instance when they have a different illness, have nutritional shortages or in case of stress.

Diagnosis

The virus can be seen by testing the blood. Birds with feather or beak abnormalities that also test positive in a blood test have an active PBFD infection. Birds that don't show any symptoms of the disease but test positive can either be a carrier or have recently been infected with the virus and do not show any signs yet. Some birds manage to get rid of the virus after being infected because their immune system has an effective response. For this reason, birds that were tested positive without any clinical signs should be tested once again after 90 days. They may then test negative.

PBFD-positive birds must always be kept separate from healthy birds, particularly from young parrot species. People who come into contact with sick birds should also be very aware that the virus can easily be transmitted by handling the bird or by feather dust.

Infected birds can pass the virus on to their young. They can already be infected while still inside the egg or the parents can infect their young when feeding from the crop.

Treatment

There is no specific treatment for the virus itself. A sick bird can survive longer if supportive care is given and no secondary bacterial or fungal infection occurs. Excellent nutrition and hygiene are therefore extremely important. 

Pokken worden veroorzaakt door het pokkenvirus. Dit virus bestaat in veel verschillende varianten, elk specifiek voor een vogelsoort of ondersoort. Het virus komt binnen door wondjes in de huid of slijmvliezen. Dit kan tijdens een gevecht gebeuren, maar ook de steek van een insect kan het virus overbrengen.

Bij een besmetting met een zwak virus (voor die vogel) kan de enige uitingsvorm van de ziekte een bultje op de plaats van besmetting zijn. Bij een sterker virus gaat de besmetting het hele lichaam rond.

Er zijn verschillende ziektebeelden bekend:

Huidvorm/droge pokken

Deze wordt vooral gezien bij roofvogels en zangvogels. Er ontstaan bulten op de onbevederde huid rond ogen, snavel, neusgaten en aan de voeten. De bultjes worden blaasjes die opengaan. Er ontstaat een korst die er na een aantal dagen tot weken afvalt. Bij ongecompliceerde besmettingen blijven geen littekens achter. Als in de open blaasjes besmetting met een bacterie of schimmel optreedt, kan de genezing ernstig vertraagd worden. In sommige gevallen blijven de bultjes intact. Afhankelijk van de plek zullen ze problemen geven, of niet.

Natte pokken

Komt vooral voor bij papegaai- en parkietachtigen, sommige duiven en fazantachtigen. Hierbij ontstaan de pokken op het slijmvlies van de tong en keel. Deze geven problemen met eten en zelfs ademen. Ook bloeden ze gemakkelijk.

Vorm met bloedvergiftiging

Dit is de meest dodelijke vorm. Het komt vooral voor bij kanaries en vinken. Het virus zorgt voor een longontsteking en de vogels zijn erg benauwd. Ze ‘happen’ naar lucht (hapziekte). De vogels zijn acuut ziek, ze zitten bol, stoppen met eten en het grootste deel (70% tot wel 99%) sterven binnen drie dagen. Er zijn vaak geen pokken op de huid te zien, daarom is de diagnose tijdens het leven moeilijk te stellen. De ziekte kan ook langzamer gaan, de vogels sterven dan vaak na enkele maanden.

Tumoren

Sommige pokkenvirussen kunnen de gevoeligheid voor tumoren vergroten. Dit komt vooral voor bij zangvogels en duiven. De tumoren zijn snelgroeiende wratachtige woekeringen die gemakkelijk bloeden. De therapie is verwijdering door chirurgie.

Diagnose

Bij de huidvorm is het vaak aan het uiterlijk al een zeer waarschijnlijke diagnose. De natte vorm en die met bloedvergiftiging is moeilijker. Hier moet het virus in de cellen aangetoond worden.

Behandeling

De behandeling bestaat uit het voorkomen van bijkomende besmettingen met bacteriën en schimmels. Tegen het virus zelf is geen behandeling

Inenting

Inenting is mogelijk. Dit beschermt een klein jaar. Vogels die al een besmetting onder de leden hebben, mogen niet ingeënt worden. De verschijnselen kunnen dan verergeren.

Dit is een ziekte die wordt veroorzaakt door een virus. Bij verschillende vogelsoorten geeft het verschillende symptomen.

Grasparkieten

Bij deze vogels is een vorm die bekend staat onder de naam kruipersziekte. Hierbij verliezen de jonge grasparkieten, rond het tijdstip van uitvliegen, hun slag- en staartpennen. Deze kunnen uitvallen of afbreken, waarbij ze behoorlijk wat bloed kunnen verliezen. De vogels kunnen niet meer vliegen en kruipen door het hok. Deze vorm kunnen de vogels overleven. Het ziekteverloop kan ook meer dodelijk zijn. De grasparkieten kunnen dan plotseling sterven op een leeftijd van 10-15 dagen. Hiervoor zijn er geen verschijnselen gezien. Als de ziekte wat langzamer gaat, kan gezien worden dat de buik vergroot is. Er kunnen bloedingen onder de huid ontstaan, de vogels kunnen moeite hebben met het evenwicht en de veren zijn afwijkend.

Papegaaiachtigen

Ook hier kunnen de ziektebeelden sterk verschillen. Jonge vogels die geïnfecteerd raken kunnen plotseling sterven, dit kan gaan zonder voorafgaande verschijnselen. Als de ziekte iets langzamer gaat, ontstaan er eerst verschijnselen zoals sloomheid, niet willen eten, gewichtsverlies, diarree, onderhuidse bloedingen en bemoeilijkte ademhaling. Ziekte komt het vaakst voor ten tijde van het uitvliegen. Na begin van de symptomen sterven de meeste jongen binnen 12 tot 48 uur. Jongen die overleven, worden dan vaak dragers die het virus blijven uitscheiden.

Oudere vogels die besmet raken worden vaak niet ziek. Dieren die wel ziek worden hebben vaak een meer slepende vorm van de ziekte. Hierbij eten ze af en toe wat minder, drinken veel, zijn gevoeliger voor allerlei andere infecties, zoals veroorzaakt door bacteriën en schimmels. Soms hebben ze ook een afwijkend verenkleed, maar dit komt niet zo vaak voor als bij grasparkieten. Vogels kunnen herstellen, hoewel een deel van deze dieren later alsnog overlijdt aan nierschade die het virus heeft veroorzaakt. Oudere vogels kunnen een verspreider van het virus worden zonder ooit ziekteverschijnselen te hebben laten zien.

Diagnose

Bij levende vogels kan bloed afgenomen worden, hierin kan DNA van het virus worden aangetoond. Bij dode vogels kan een het virus in lever en nieren gevonden worden. Ook kan een swab genomen worden uit de cloaca. Hiermee wordt echter alleen aangetoond of de vogel het virus uitscheidt of niet. Een negatieve uitslag betekent daarom niet automatisch dat de vogel niet besmet is. De uitscheiding van het polyoma virus kan wisselend zijn. Een bloedtest is hierom betrouwbaarder.

Oudere vogels die besmet raken, kunnen door een goede afweer het virus weer kwijt raken. Daarom wordt aangeraden bij een vogel die positief is, de bloedtest na 45-60 dagen te herhalen. De vogel kan dan negatief zijn.

Behandeling

Er is geen specifieke behandeling mogelijk tegen het virus. Oudere vogels die besmet raken, worden vaak ziek na een periode van stress. Het voorkomen van stress is daarom belangrijk. Jonge vogels waarbij de bloedstolling verstoord is (waarbij dus onderhuidse bloedingen optreden) kunnen injecties met vitamine K krijgen. Deze helpen met de bloedstolling. Als een vogel echter al zo ziek is, zullen ze in de meeste gevallen snel sterven.

Preventie

Het belangrijkste is voorkomen van besmetting. Het is daarom erg belangrijk bij aankoop van nieuwe vogels, om zeker te weten dat deze niet besmet zijn en zo het virus kunnen introduceren. Er wordt aangeraden voor aankoop een bloedtest te laten doen, dit is zeker belangrijk als u thuis al vogels heeft.

Salmonella is a bacterium that affects many animals. Birds become infected by ingesting the bacteria. Salmonella mainly causes sickness in birds if they are already weakened, if the normal intestinal bacteria are not present or if the intestinal flora is disrupted.

Chicks that are still inside the egg can already be infected. If heavily infected, most chicks will die before hatching. Chicks that aren't severely infected will survive inside the egg and hatch normally. However, they act as carriers and, as Salmonella lives in the intestines, can transmit the bacteria to other birds via the droppings. They usually aren't sick themselves. In periods of reduced resistance though, these birds will also show signs of sickness if the Salmonella gets the upper hand.

Symptoms

There are many different Salmonella types, and some are more capable of causing sickness than others. A virulent Salmonella is a strain which is more likely cause disease. These bacteria often are capable of penetrating the intestinal wall and infect the rest of the body. This then causes sepsis/ blood poisening. Birds infected with virulent bacteria often display acute sickness. They are lethargic, stop eating, drink a lot and have diarrhoea. Healthy birds with a good functioning immune system can survive, but many will perish when infected.

Less virulent Salmonella bacteria can only spread to other parts of the body if the mucous membrane in the intestines is already damaged. For instance after an infection with another pathogen. Otherwise healthy birds can become infected by this type of Salmonella without showing any obvious signs. If the less virulent Salmonella manages to penetrate the intestinal wall, it will cause similar symptoms to those of the virulent Salmonella.

If a bird doesn't die from the blood poisoning, it can develop a more chronic illness. This can involve various symptoms, such as an affected nervous system, arthritis, shortness of breath and conjunctivitis.

Diagnosis

In birds that are ill, but still alive, the Salmonella can be detected in the faeces. A stool culture is used to diagnose infection. This method also enables the veterinary surgeon to determine which antibiotics have the greatest effect in combating that specific Salmonella.

If the bird has already died, a necropsy can be performed. The organs are thoroughly examined and abnormalities in affected organs can be cultured. After a few days it becomes clear whether Salmonella was present inside the organs.

Therapy

Birds are treated with antibiotics. Treatment is also recommended for birds that show no visible signs of sickness, but are infected. The reason for this is that the bacteria can still cause problems in periods of reduced resistance, but also due to the fact that carriers can still infect other birds by spreading the bacteria through their droppings. What's more, it's quite possible for children and people with a weakened immune system to become infected with Salmonella.

It is often very difficult to eradicate the bacterium in birds that have been infected prior to hatching and birds with a long-term chronic infection. It is therefore wise to check the effects of the antibiotics at the end of the treatment. This can be done by once again perform a stool culture.

Prevention

Proper hygiene in the bird enclosure is of the utmost importance. In case of repeated problems, it could be very useful to find out if there are any other birds in the enclosure that carry the Salmonella bacterium inside them. These birds continuously excrete the bacterium and can continue to infect otherwise healthy birds.

Birds that are in good health should have enough resistance to prevent the Salmonella from causing sickness. The normal intestinal bacteria play an extremely important role in prevention. If they are in good shape, there is simply 'no room' for the Salmonella bacteria. Infection doesn't lead to these birds falling ill as they can pass the bacteria out again. Providing the bird with a probiotic supplement can offer significant help.

A vaccination is available for pigeons and chickens against Salmonella. For other birds, vaccination is not yet widely used.

Veel problemen bij vogels zijn terug te leiden op voeding die niet optimaal is samengesteld. Er komen veel tekorten in de voeding voor, maar ook een te grote hoeveelheid vitaminen kunnen problemen veroorzaken.

Zaadmengsels zoals in dierenspeciaalzaken verkocht worden zijn niet geschikt als compleet voer. In deze mengsels missen een aantal onmisbare voedingsstoffen, waaronder bepaalde vitamines, mineralen en aminozuren. Daarom is het nodig aan het zaadmengsel een voedingssupplement toe te voegen. Hierbij is het belangrijk dat op de verpakking vermeld staat wat er precies inziet. Als dit niet zo is, kan de samenstelling per keer veranderen.

Voer van een niet optimale samenstelling kan voor verschillende problemen zorgen:

Vetzucht

Vogels zullen een voorkeur hebben voor bepaalde delen van het zaadmengsel. Vaak zijn dit de zonnepitten. In zonnepitten zit erg veel vet. Als de vogels naast het selectief eten ook nog weinig bewegen, kunnen ze snel veel te dik worden. Vooral kaketoes, amazones en grasparkieten zijn hier gevoelig voor. Ze kunnen vettumoren (lipomen) ontwikkelen, er kan schade aan de lever ontstaan en hartfalen.

Vitamine tekorten

Vitamine A

Dit wordt in de lever gevormd uit bètacaroteen. Als deze bouwstof te weinig in het voer zit kunnen tekorten ontstaan. Vitamine A is belangrijk in de vorming van slijmvliezen en huid. Slijmvliezen vormen de binnenbekleding van verschillende belangrijke organen. Bij een tekort aan vitamine A worden deze dikker dan normaal. Dit zorgt voor allerlei problemen. Zo kunnen de vogels problemen krijgen met de nieren als de afvoergangen hiervan dicht gaan zitten door de te dikke slijmvliezen. Ze kunnen benauwd worden als de luchtpijp (deels) dicht gaat zitten.

Behalve de slijmvliezen kan ook de huid op de poten afwijkend worden. Ook deze zal dikker worden. Als dit op de voetzolen gebeurt, verhoogt dit de kans op het ontstaan van bumblefoot.

Vitamine D

Een deel van het vitamine D wat een vogel gebruikt nemen ze op uit het voer. Daarnaast worden bouwstoffen voor vitamine D onder invloed van zonlicht in het lichaam omgezet in vitamine D. Als er onvoldoende vitamine D in het voer zit, en daarnaast wordt de vogel binnen gehouden (zonder direct contact met zonlicht) kunnen er gemakkelijk tekorten ontstaan.

Vitamine D zorgt ervoor dat calcium in het voer goed wordt opgenomen. Een tekort aan vitamine D kan ervoor zorgen dat dit minder gebeurd en zo kan ook een tekort aan calcium ontstaan, zeker als dit toch al weinig in het voer aanwezig is.

Bij jonge vogels kunnen botten vervormen omdat ze niet sterk genoeg worden door het gebrek aan calcium. Oudere vogels krijgen botontkalking en kunnen sneller de botten breken. Bij leggende vogels worden vaak eieren met een erg dunne schaal gezien.

Vitamine E

Vitamine E is een antioxidant. Dit betekent dat het door schadelijke stoffen weg te vangen schade aan cellen voorkomt. Als er naast een tekort aan vit E ook een tekort is aan het mineraal selenium kunnen spieren aangetast worden. De vogels zijn zwak, soms lijken ze verlamd. Als ook de spieren in de spiermaag zijn aangetast verteren ze het voer minder goed.

Een gebrek aan vitamine E kan ook zorgen voor hersenverschijnselen, vooral bij kippen is dit een bekend verschijnsel. De vogels hebben last van het evenwicht, kunnen trillen en draainekken.

Mineralen tekorten

Calcium

Dit is belangrijk voor de vorming van botten en eischalen, en speelt een rol in de aansturing van spieren. Bij tekorten in de voeding zal het lichaam calcium die het nodig heeft uit de botten gaan halen. Deze worden als gevolg daarvan broos en breken gemakkelijk.

Bij de grijze roodstaart komt daarnaast een ziekte voor waarbij het lichaam calcium nodig heeft maar het niet lukt dit uit de botten te halen. De vogels krijgen hierbij aanvallen waarbij ze van de stok vallen en erg slap zijn. Deze vogels hebben levenslang extra calcium in het voer nodig.

Jodium

Dit is nodig om schildklierhormoon aan te maken. Als er te weinig jodium in het voer zit, zal de schildklier als compensatie sterk gaan vergroten. De schildklier zit bij vogels onderaan de nek, net voor de ingang tot de borstholte. Vergroting van de klier kan zorgen dat de luchtpijp voor een deel wordt dichtgedrukt. Dit veroorzaakt benauwdheid. Als de klier op de uitgang van de krop drukt, kan een vertraagde kroplediging ontstaan of de vogel kan het opgenomen voer weer uitbraken.