How are diseases transmitted?
Transmission of diseasesKeeping birds involves breaking through the natural biological balance between the bird and its environment. For example in the cage or loft, if dung isn’t removed regularly, micro-organisms can breed rapidly and cause diseases.
Diseases can spread in three ways:
1. From one bird to another. This can be directly, when feeding (adult – young), or indirectly, through water, feed, feather dust, dung, air, nets, transporting cages or shoes. Worm-eggs, bacteria, moulds and viruses can be transmitted in this way.
2. From the mother-bird to the egg, as with Salmonella and Leucosis.
3. Through a intermediate host, such as a sparrow, a snail, slug, fly, midge. Eliminating those intermediators by hygiene and good accommodation is an important preventive measure. Those intermediators should not be given as food.
Zoonoses,
These are diseases transmitted from vertebrates to humans and vice versa. Import of birds can import also (unknown) zoonoses. The importer has to stay alert.
Stress
This is a condition of the bird bringing the defence mechanism in increased readiness. It breaks into the reserves of the body and can weaken the bird if it takes a longer period.
Stress can be caused by catching, caging, transporting, changes in the food, the temperature, light or humidity, overcrowding, medication or exhibitions.
The symptoms can be subclinical, meaning they aren’t perceptable. In general the bird eats less and has a lowered resistance against diseases. It grows thin and often suffers diarrhoea.
Pathogenicals
Pathogenicals are organisms causing diseases in birds, like: bacteria, viruses, moulds, protozoa, worms and insects. Micro-organisms are only perceptable with a microscope. Bacteria, viruses, protozoa and moulds are micro-organisms. Bacteria are found in all living creatures, some have good functions, like helping the digestion or forming proteins. But also harmful, pathogenic micro-organisms exist. Their harmfulness depends on:
the ability to cause diseases;
the amount of micro-organisms;
the sensitiveness of the bird for the organism. A bird can be a bearer, if he carries the pathogenical organism, but isn’t ill. A bird is infected if the pathogenical organism has made the bird ill, showing the symptoms. The incubation period is the time between the infection and the breaking out of the disease.
What are bacterial infections?
Introduction
Bacteria are one-cell organisms. The smallest bacteria are 20 to 30 times larger than the largest viruses. Bacteria multiply by partition.
Bacteria or their waste products can cause diseases. The seriousness of the disease depends on the ability to cause diseases of the organism and the susceptibility of the bird. The symptoms in infected birds aren’t specific; mostly upright feathers, slowness, loss of appetite, fast breathing and often diarrhoea.
The diagnosis “bacterial infection” can only be affirmed by research of the blood, dung, organs or tissue. Bacteria can be identified by culture or by testing the reaction with a serum of an immunised animal (agglutine test). Some bacteria can be identified through a microscope.
A sensibility test is needed to find the right antibiotic. This test can take some days.
Bacteria can be classified in Gram-positive and Gram-negative bacteria. This classification was introduced by dr. Gram in 1890. Some bacteria (Gram-positive) can be coloured with a certain substance and others (Gram-negative) can’t. Gram-positive bacteria are a.o.: Bacillus, Clostridium, Listeria, Staphylococcus and Streptococcus. Gram-negative bacteria are: Escherichia, Pasteurelle, Salmonella and Yersinia.
Healthy birds feeding on seeds and fruits mostly have no Gram-negative bacteria in their intestines, but they do occur with insectivore and carnivore birds.
Salmonellosis
Salmonella can infect birds, mammals and reptiles. Salmonellosis is a very infectious disease of the digestive tract. It is regularely seen in poultry, waterfowl, pigeons and meat-eating birds. Of the about 1500 serotypes of Salmonella is S. typhimurium the most common.
Birds can be infected by Salmonella through dung, perches, feed and water bowls. Through the ovarium the egg-embryo can be infected. Insects, mice and rats can bring over Salmonella. The incubation period is 1 – 2 days. After 2 – 4 days the sick birds die.
Salmonella can survive in mud until 1,5 year, in still water at least 4 months, in dead meat and dung about 1,5 month. Cage, aviary and bushes even can accommodate Salmonella for 2 years.
Appearance of the disease (see also introduction): the dung mostly is watery and greenish and soils the feathers around the anus. Salmonella bacteria come into the blood through the small intestine, nestle in the joints and cause swellings and stiffness. Infected egg joints can result in limpness, infected wing joints in hanging wings.
Dissection can show a enlarged spleen with yellow bumps. Intestines, liver and heart mostly are inflamed. The general picture is like that of pasteurellosis, pseudo tuberculosis and chlamydiosis. Cultures of Salmonella from the dung can affirm the diagnosis.
Prevention and cure
A sensibility test can show which antibioticum is effective, f.e. chloramphenicol or trimethoprim/sulfa. Prevent salmonellosis by good food and hygiene and a housing free of mice and rats. Healthy birds can be bearing Salmonella bacteria.
What are virus infections?
Introduction
Viruses vary in size from 10 to 500 millimicron. These organisms, only visible with an electron microscope, are like something in-between living and death substance. Viruses don’t have a metabolism themselves; they need a living cell to multiply. Outside a living cell viruses mostly break apart within a few weeks, except the bird-pox virus. In extremely low temperatures viruses can live outside a living cell for a longer time. Viruses are spread for long distances through the air.
There are no medicines for virus infections. For a minimum risk of virus infections a good housing, care and feeding is important, as well as vaccination in the right time.
Newcastle disease
NCD is a feared virus disease in poultry, ducks and geese. Most poultry is susceptible of NCD and the death rate can be enormous. NCD is also diagnosed in birds of pray, owls, pigeons and imported parrots. To protect the poultry farmers against NCD some juridical regulations are made to prevent bringing this disease into the country with imported birds.
NCD is a zoonosis and can cause eye infections and fever for humans.
The viruses can be brought over through the air or through direct contact. In temperatures of 20 – 30 degrees Celsius after 123 days there were still living NCD viruses on down-feathers of birds in quarantine.
Symptoms
The incubation period of NCD is about 5 days. Newly infected birds have breathing and digestion problems. The symptoms are: irregular breathing, sneezing, shaking of the head and diarrhoea. If the central nerve system is affected the bird is apathetic and suffers from disequilibrium and lame legs and wings.
What are mould infections?
Introduction
Moulds are primitive herbal organisms. Although they are ranked amongst the plants, they miss the green leeve colour chlorophyll.
Moulds produce spores, which are highly resistant to natural influences. The spores are spreaded through the air. Some digestive products of moulds are used for producing antibiotics. In birds moulds commonly cause skin infections. Regular administration of antibiotics stimulates the growth of moulds, like candida and aspergillus. Little amounts of mould don’t make healthy birds ill. Moulds can be identified by comparing a culture with well-known species.
Aspergillosis
About 30 species of Aspergillus exist. Aspergillosis is caused by Aspergillus fumigatus. Most birds are sensitive to this mould. It spreads through breathing the spores or by direct assimilation. Aspergillus flourishes in a humid environment, like badly ventilated sheds, cages and aviaries, breeding machines, nests, greenhouses and soiled transporting boxes.
The bacterial flora of the digestive tract can be disturbed by antibiotics, which can conduce the growth of moulds.
What are parasitical diseases?
Introduction
Parasites are plants or animals. They live on or inside, or feed on their host, in this case a bird. Most parasites live in balance with their host. But when parasite multiply too strong the bird will become ill. The sensitivity to parasites is larger when the birds have a lowered resistance, f.e. for the reason of stress, malnutrition, illness or age.
Cage and aviary can be infected with parasites by the dung of wild birds, mice and rats, newly bought birds, transporting boxes, feed and intermediators. A good hygiene is important for prevention. Two groups of parasites are distinguished:
internal parasites, like protozoa and worms;
external parasites like mites, flees and lice.
Protozoical infections
Protozoa are microscopical one cell organisms. They occur in the digestive tract or in the blood of birds.
Protozoa in the digestive tract:
Coccidiosis
There are two species of coccidia common in birds:
Eimeria, especially in poultry, waterfowl and pigeons;
Isospora in singing birds and birds of pray.
The eggs of coccidia are called oocysts. The ripe oocysts taken by the birds are divided inside the bird’s stomach. The cycts that come free multiply in the stomach wall and damage it so it can become infected by other micro organisms. Inside the bird’s body the cysts melt together and form oocysts. They are excreted with the dung and, after half a day to two days of ripping in a humid and warm environment, the are a new danger of infection for the birds. Oocysts are resistant against many environmental factors.
Symptoms
Infected birds are sitting hunched up on their roost or on the ground. They sleep a lot, have little appetite and become thin. The dung is watery and slimy, so times with blood in it. The feathers around the anus are soiled. The belly is swollen and through the skin of the belly the swollen intestines are visible. In case of acute infection the bird can die within a few days, in case of a chronical affection it can take weeks before the bird dies in an exhausted condition.
Youngs in the nest can be infected by their parents’ dung. They have little defence and the death rate among young is high. The diagnosis can be affirmed by microscopical research.
Prevention and cure
Most birds have oocysts inside their intestines. They only become ill after a certain grade of infection.
Eimeria can be controlled by Amprolium.
Isospora can be controlled by preparates of Sulfa (like Esb3).
Prevent infection by a good housing. Avoid overcrowding, keep feeding and drinking bowls free from dung, avoid humid spots on the floor, remove dung regularly and keep the birds in a good condition.
What is Trichomoniasis?
Trichomoniasis is a common disease in pigeons, but also in quails, birds of pray, canaries, finches, paroquets, etc. Birds are infected in feeding.
Symptoms
The incubation period is about 4 days. If there is a acute Trichomoniasis white sticky substrates are visible inside the bill and the throat. If the Trichomoniasis is chronical the mass is cheese-like. It causes pain and hinder the passage of food. In very bad infections it can affect also the breathing. The birds try to get air with a stretched neck.
In sputum and scrapings from the inside of the nose the microzoa are visible with a microscope. But also candidiasis, pox and shortage of Vitamin A can cause such symptoms in bill and throat.
Prevention and cure
Treat the affected spots several times a day with a solution of Dimetridazole or Carnidazole. Use a soft brush or cotton bud. Tetracycfine is given to prevent infection of the damaged spots.
What is Histomoniasis?
Histomoniasis is caused by Histomonas meleagridis. This disease occurs especially in poultry. The protozoa are 0,5 – 1,5 mm in length. They occur in the eggs of the intestine worms Heterakis gallinae and H. isolonche. Earthworms eating these eggs become intermediators. When birds eat the eggs of the contaminated intestine worms or the earthworms, they become infected. In the caecum or in the liver the protozoa come out of the eggs. They harm the wall of the intestine and liver.
Symptoms
The incubation period is 2 – 3 weeks. Infected birds are weak, sit with feathers upright and hanging wings and tail. Striking is the yellow brownish diarrhoea. In turkeys the disease is called “blackhead”; the naked parts of the head become very dark purple. The death rate in turkeys is high, often even 100%. Especially young poultry is susceptible.
The diagnosis can only be affirmed by dissection. Inside the intestines ulcers or necrotical spots can be found. In the liver round yellow green spots are seen.
Prevention and cure
Treat the animals with Dimetridazole or Furazolidon. Also give them a medicine against intestine worms. Remove old litter, clean the housing and disinfect it.
What are worm-infections?
Introduction
We disecer worms of the digestive tract, of the respiratory organs and of the blood vessels. Some worms can stay inside the intestines of the bird until a certain infection grade without causing any symptoms of illness. When the infection grade is exceeded, or when the bird is in bad condition, the bird will become ill.
Flatworms
Trematopodes, flatworms or suctions worms can vary from 3 to 25 mm. Many species have two suckers at their front- and backside. Flatworms need intermediators for their life cycle. They occur with poultry, waterfowl and pigeons; in some cases with imported parrot species.
The symptoms aren’t specific. The bird looses its appetite, is thirsty, has diarrhoea and has anaemia. The diagnosis can be affirmed by research of the dung (worm-eggs in the dung).
Dissection can prove flatworms, depending on the species, in the small intestine, the large intestine, the caecum, the cloaca, the blood vessels, the liver and other organs.
Tapeworms
Cestodes or tapeworms attach themselves with suckers or hooks inside the intestines, so they can’t be driven out by the peristaltical movements. They feed by absorption through their body. They need a intermediator (snails, slugs, flies, bugs, ants) as well as a host (bird) for their life cycle.
Roundworms
Nematodes or roundworms are round, without segments, have a smooth skin and pointed ends of the body. Among the roundworms are: hairworms, big intestine roundworms and yawn-worms of the respiratory organs.
Hairworms (Capillaria)
Depending on the species, they live in the crop, the gullet, the small intestines or the caecus. Their size is 20 x 0,5 mm. Some species have a direct life-cycle (without intermediator), some a indirect (with intermediator).
Hairworms cause inflammations in the walls of the intestines and anaemia. Eggs excreted with the dung become infectious after 2 weeks and can stay infectious for months, at temperatures between 0 and 35 degrees Celsius and in high humidity even a year. The development of an egg to an adult worm takes 5 to 8 weeks. The eggs are shaped like a lemon with transparent ends. They have a smooth, thick, brownish shell.
Symptoms
Not specific: slowness, upright feathers, no appetite, loss of weight and in a serious infection also thin slimy dung.
Prevention and cure
Fenbendazol is a good medicine.
Ascaridia or big roundworms
They occur a.o. in large fancy birds, parrots, poultry and pigeons.
Ascaridia are harmful for the birds because:
they live inside the intestine walls and hurt them;
large balls of worms can stop the passage of food;
worms can block the entry of the gall-bladder;
worms can feed themselves with the food in the intestines.
Those worms have a direct life-cycle. Their eggs are oval-shaped and have a wall of three layers. They are excreted with the dung at irregular intervals. Outside the bird’s body the larvae develop inside the eggs. After 1 – 2 weeks they are infectious and stay infectious for seceral months. When the eggs come inside a bird’s body, the worms come out.
The most occurring of these worms is Ascaridia hermaphroditae. Their size is 25 to 40 mm of length and 1 mm thick. Large parakeets are very susceptible for these worms. A light infection won’t cause illness in a healthy bird.
Symptoms
loss of weight and diarrhoea. The birds can die because they lock up the intestine.
Prevention and cure
good medicines are Levamisole, Fenbendazol, Mebendazole and Ovorotol."
