Infectious Diseases of Poultry & Management of Lethal Poultry Diseases
A. Janmaat* and R. Morton,
Biosecurity and Product Integrity, Darwin * Formerly of DoR
Introduction To Infectious Diseases of Poultry
Poultry that have an infection
show a variety of symptoms, such as respiratory problems, diarrhea and
paralysis. It should be emphasized at the outset that prevention of infection
in a poultry flock through sound management is very important. This is because
although some infectious diseases can be treated, for many it is a waste of
time and money and infected birds should be disposed of immediately.
Infectious organisms may be
divided into four classes:
- Protozoa
- Bacteria
- Fungai
- Virus
Specific
drugs are usually recommended for bacterial, protozoan and fungal infections,
while some viral diseases can be prevented by vaccination. For more information
on suitable drugs, consult your local veterinarian.
BACTERIAL DISEASES
(a) Colibacillosis
This is the common name for a
large variety of diseases, including yolk-sac infection of chicks, reproductive
disorders and peritonitis in layers, and septicemia (blood poisoning) in
growers. They are all caused by the bacterium Escherichia coli, which is found
in the intestines of all warm-blooded animals. Affected birds can be treated
with antibiotics. To prevent further spread of this organism, disinfect the
premises and the pens with a commercial disinfectant, and provide good
drainage.
(b) Salmonella infection
(i) Paratyphoid (salmonellosis)
Salmonella infections may affect all domestic poultry, although adult birds
often do not show any symptoms. Salmonella bacteria may also contaminate
hatching eggs, which results in diarrhoea, depression and death in young
chicks. Paratyphoid is highly infectious and can be transmitted by mice, rats,
other birds and/or through contaminated feed. Symptomless adult birds
constitute a human health risk if meat and egg hygiene are not adequate.
(ii) Pullorum (bacillary white
diarrhoea) usually a symptomless disease in adults, pullorum is transmitted to
young chicks through the egg. This results in fatal diarrhea within the first
four weeks of life. Adult birds may suffer from infection of the ovaries, or septicemia.
This disease can be eliminated with good hatchery hygiene. No cases have been
reported in the NT in recent years. All poultry entering the NT must come from
pullorum-free hatcheries. To avoid this disease, buy chicks only from a
reputable hatchery.
(c) Psittacosis
Psittacosis is found mainly in
psittacine birds (parrots, lorikeets, galahs, cockatoos, budgerigars etc), but
may also affect pigeons, turkeys and chickens. In chickens, symptoms may pass
unnoticed or the birds may exhibit general weakness, diarrhoea and discharge
from the eyes and nose. All infected birds should be culled and burned. The
remainder of the flock should be treated with antibiotics in the feed. As the
disease can be transmitted to humans, great care must be taken when handling
infected birds. In humans, the disease resembles influenza but can progress to
a severe, and possibly fatal, pneumonia.
(d) Avian spirochaetosis (tick fever)
In chickens and turkeys the blood
parasite Borrelia anserina causes a relapsing fever-like condition. This
disease, which is transmitted by the fowl tick Argas persicus, has been
diagnosed in Darwin, Alice Springs and on many stations. Birds of all ages may
be infected. They become feverish, have green diarrhoea and may become
paralysed in the wings or legs. The disease can be controlled by eliminating
ticks from the flock (see Agnote K2 External Parasites of Poultry). In backyard
flocks, the painting of perches and woodwork with sump-oil or creosote and
removing and disposing of wood and rubbish from yards is usually an effective method
of control.
(e) Staphylococcus infections
The bacterium Staphylococcus
aureus is widespread in the environment and causes a variety of opportunistic
infections in poultry, especially in the tropics. These include foot abscesses,
infections of joint membranes and dermatitis of combs and wattles. These
infections may be treated with suitable antibiotics in the feed. Badly-infected
birds are best removed and destroyed, as full recovery does not usually occur.
The premises should be disinfected.
(f) Infectious coryza
Infectious coryza is caused by a
small bacterium Haemophilus gallinarum, which mainly infects growing and laying
fowls under conditions of poor hygiene, ventilation and nutrition. Symptoms are
discharge from the eyes and nostrils, a swollen face, a drop in egg production
and sometimes diarrhoea. It is a chronic disease, which can result in
mortalities when complicated with other infectious agents. Infected birds
should be culled, as they may remain carriers for several months after
infection. Preventative measures include rearing growers away from older birds,
culling of carrier birds and improved management.
(g) Chronic respiratory disease
(CRD)
CRD is caused by Mycoplasma
gallisepticum. Its symptoms are sniffling, sneezing and depressed egg production
in chickens and sinusitis in turkeys. Its severity often depends on the
concurrent presence of other diseases. Both turkeys and fowls of all ages can
be infected. This disease is transmitted by inhaling infected air droplets,
through eggs to the next generation, or by mechanical means, such as boots and
equipment. The organism will die in a day or two when pens are empty, but
recovered birds may remain carriers for some time. CRD may be treated with
specific antibiotics and vitamin supplements in the feed if only a few birds
are involved. Another bacterium of this group, Mycoplama synoviae, causes
subclinical upper respiratory tract infection and may be involved in air
sacculitis associated with Newcastle disease and infectious bronchitis. Consult
your veterinarian for antibiotic recommendations for these diseases. Vaccines
are available for both of them.
(h) Fowl cholera
All domestic poultry are
susceptible to this highly infectious disease, caused by the bacterium
Pasteurella multocida. Fowl cholera may be deadly, or may linger in infected
birds. Symptoms are variable and include respiratory problems and diarrhoea. It
is spread through the flock by contaminated water, in droppings and in nasal
discharges. All infected birds should be culled and burned. The disease can be
treated with a number of antibiotics or sulphonamide drugs. It can be prevented
by good management and vaccination.
(i) Tuberculosis (Mycobacterium avium)
Rarely found in young chicks,
this infection is a "wasting" disease of all domestic poultry,
canaries, parrots, pigeons and wild birds kept in captivity. Avian tuberculosis
may be transmitted to humans, cattle and pigs. Symptoms are not specific and
may include gradual loss of weight, diarrhoea, lameness, general weakness and eventually,
death. Treatment is not recommended. All infected birds should be culled and
burned. The premises should be cleaned with a phenolic disinfectant or lime and
then left for two years before introducing a new flock. Notify the Department
of Resources if you suspect tuberculosis in your poultry.
FUNGAL DISEASES
As all domestic poultry, wild
birds, other animals and humans can be infected by fungi, take great care when
handling infected birds. Transmission occurs by inhaling fungal spores from
sick birds, contaminated litter or feed.
(a) Aspergillosis
The most common fungal disease in
birds is Aspergillus fumigatus, which causes pneumonia or enteritis in all age
groups, especially in the presence of other infections. Treatment is not
recommended. Infected birds should be culled and burned. All mouldy litter
should be removed and burned and the pens should be sprayed with 1% copper
sulphate.
(b) Candidiasis or thrush
Candidiasis is another common
fungal disease, which is found in younger age groups of all domestic poultry.
It usually affects the mouth and crop, with sour-smelling crop content. It may
also cause diarrhoea. It primarily affects stressed birds. Check for unsanitary
conditions, overcrowding and coccidiosis. Treat with nystatin to provide effective
control.
PROTOZOAN DISEASES
(a) Coccidiosis
Coccidiosis is one of the most
common diseases of poultry. It is caused by a number of species of protozoa
called coccidia. Fowls, turkeys, ducks and geese are all affected. However,
coccidia are host-specific, so fowls are not affected by duck coccidia and vice
versa. The disease usually affects birds over three weeks of age. The symptoms
include ruffled feathers, drooping wings, pale combs and diarrhoea, sometimes
streaked with blood. Most losses occur in young birds, but adult birds can also
be affected. Large numbers of chickens may die suddenly without apparent
symptoms. The coccidia live in the intestine or caecum of the bird and pass out
through the droppings. They become infective in damp surroundings and are
spread from bird to bird when infected droppings are eaten. Coccidia may
survive for long periods in the litter. Good management will help prevent
serious outbreaks of coccidiosis. If birds are denied access to droppings, the
life cycle will be broken. This is achieved when birds are raised on wire. Damp
litter around water troughs will allow coccidia to become infective. Medication
in feed is often necessary to prevent outbreaks of coccidiosis. Young birds
raised on the ground should be routinely treated with a coccidiostat. As the
wet season provides ideal conditions for coccidia to become infective,
medication is recommended at that time.
(b) Blackhead
The protozoon that causes this
disease is Histomonas meleagridis. Both young fowls and turkeys are affected by
this protozoon but turkeys are far more susceptible and are more likely to
contract this disease when run with poultry than when run on their own.
Histomonads live largely in the caecum (blind gut) and invade other organs from
there. Symptoms of blackhead include a drooped and huddled appearance, dark
colouration of the head, shrunken comb and wattles and yellowish diarrhoea.
Living in the caecum places the histomonads in contact with the caecal worm
(Heterakis gallinae) and the eggs of the worm become infected with the
protozoa. Blackhead is transmitted when birds eat droppings containing these
infected worm eggs. Drugs are available to treat blackhead. To prevent
re-infection, control caecal worms at the same time with good management.
Turkeys and fowls should not be run together.
(c) Trichomoniasis
Trichomoniasis is caused by
Trichomonas gallinae. It is a disease of the upper digestive tract. It has been
found in pigeons, doves and kites in the NT but may invade hens and turkeys if
they drink infected water or eat infected feed. Affected pigeons will go
off-feed, appear ruffled, become emaciated and die, with a green yellow fluid
dripping from the beak.
VIRAL DISEASES
Viral diseases are the most
common cause of losses, not only in large commercial flocks, but also in
backyard chickens. Mostly, they do not respond to drug therapy. Treatment
relies on supportive measures. Prevention and control relies on vaccination
where this is effective, or by limiting exposure to infected birds. If a
secondary bacterial infection is also present, antibiotics may reduce the
severity of an outbreak.
(a) Marek's disease (MD)
This disease usually affects
birds two to five months old and causes lymphoid tumours. Symptoms vary
according to the position of the tumours. Usually the nerves are affected and
spastic paralysis occurs either in the legs, wings or neck. The virus of MD can
remain infective for many months in litter or dry feathers. MD is prevented
very effectively by vaccinating day-old chicks. Buy only vaccinated chicks.
(b) Lymphoid leucosis
This disease is normally found in
chickens more than four months old. They pick it up in the first few weeks of
their life, or from the mother which, if affected, passes leucosis through the
egg. The tumours develop slowly; birds become sickly, pale and thin, and often
have an enlarged abdomen. There is no known effective treatment for leucosis,
nor are there any vaccines available. Affected birds should be culled from the
flock.
(c) Fowl pox
This is a highly infectious
disease caused by various host-specific strains of the pox virus. Many birds
are affected by these viruses to some extent. The virus can be transmitted
directly by infected birds, or be carried by mosquitoes, or other blood sucking
insects. By eliminating breeding areas for these insects, the rate of spread of
the virus will decrease. The fowl pox virus attacks the skin and the surface of
the mouth and throat. Depending on its location, pox is referred to as either
skin pox or wet pox. Skin pox forms wart-like sores, which eventually enlarge
and form masses of yellow, dirty crusts. In about a week, these scabs darken
and fall off. Wet pox forms cheesy masses in the mouth, nose and throat, which
interfere with eating and drinking.
Antibiotics may be administered
to prevent bacterial infections but the best method of control and prevention
is by vaccination of day-old chicks. This virus is capable of surviving for a
long time in infected material, such as scabs and litter. Such material should
therefore be incinerated.
(d) Infectious bronchitis (IB)
IB is an acute, highly infectious
disease of poultry, which may kill young chicks and lower egg production in
adult birds. Birds sneeze and have a moist cough. The entire flock will be
affected. Laying birds will stop laying and it may take a very long time for
them to return to production. There is no effective treatment for this disease.
Maintenance of a correct, even temperature in the brooder and a high quality
diet will help to minimise losses. Commercial flocks are routinely vaccinated.
(e) Infectious laryngotracheitis (ILT)
ILT is a disease of all ages of
poultry, although usually it is seen in adult birds. An acute form may attack
100% of a flock and cause severe mortality. In the acute form, affected birds
exhibit a nasal discharge, gurgling breath sounds, gasping and coughing up of
blood-stained mucus. In the mild form, birds are unthrifty, lay poorly and have
watery eyes and a persistent nasal discharge. There is no effective treatment
but vaccination of unaffected birds may limit an outbreak. Vaccination is
effective in preventing the appearance of the disease.
(f) Reticuloendotheliosis (RE)
RE became an important disease of
commercial flocks in 1976 and, occasionally, still appears in an epidemic form.
It causes runting, increased susceptibility to other diseases and feathering
defects in growing chicks. In adult birds, it causes Iymphoid tumours. No
treatment or vaccination is available.
(g) Avian encephalomyelitis (AE)
AE is a disease of poultry,
turkeys, pheasants and quail, which affects only chicks from hatching to about
two months of age. The symptoms are dullness, tremors of the head, staggering,
paralysis and prostration. Adult birds show no symptoms other than a decline in
egg production, but they carry the virus and pass it on through the egg. The
disease may also spread from chick to chick and up to 60% of birds may be
affected. There is no treatment for AE but vaccination will prevent it.
EXOTIC DISEASES
Exotic diseases are those which
are present elsewhere in the world but not in Australia. There are three which
particularly threaten the Australian poultry industry.
(a) Newcastle disease
This virus is found in Australia
in a mild form only. The dangerous form is widespread throughout the rest of
the world. If it became established in Australia, the cost to the poultry
industry could be enormous. Newcastle disease is a highly contagious, lethal
disease of chickens and turkeys, although nearly all avian species are
susceptible. It may also cause conjunctivitis in humans. In poultry, it may
take the form of haemorrhagic enteritis and paralysis, or an acute respiratory
disease.
Also Read: Management & Treatment of ND "New Castle Disease" with Homeopathic Medicine - Guaranteed Results
(b) Avian influenza or bird flu
It is potentially a fatal disease
affecting several bird species and humans. Its symptoms range from mild upper
respiratory disease to an acute, generalised, fatal condition. The virus may
remain infective in droppings and water for at least a month. For further
information on bird flu consult Agnote K53, Bird Flu: What Bird Keepers Should
Know and Do.
(c) Infectious bursal disease (IBD)
The virus of IBD is present in
Australia but the strain is of low virulence. The hyper-virulent strain has
been found in Europe, the USA, Japan and South-East Asia. This strain is very
infectious and causes up to 60% mortality in young laying birds. Affected birds
peck at their own vent and later exhibit white, watery diarrhoea, depression,
trembling and prostration. Less severe outbreaks may show few symptoms apart
from low production. The virus may remain infective for over a month in
buildings, water, feed and droppings. Entry of exotic diseases Migratory birds
may be a threat as carriers of Newcastle disease and avian influenza from Asian
countries. Live birds or bird products smuggled into the country may carry
exotic diseases and threaten the poultry industry. However, Australian
regulations are stringent and, so far, effective. Although these diseases may
be controlled by vaccination to a certain extent, this will not be attempted if
they appear in Australia. They will be eradicated by the slaughter and
quarantine of infected and in-contact flocks.
TREATMENT OF BIRDS
If a number of birds are sick or
dead, it is wise to seek veterinary advice before undertaking treatment. When
treatment of a disease with drugs is needed, the manufacturer's instructions
should be carefully followed. If the drug is to be mixed with drinking water or
feed, make sure that the birds have no water or feed for a few hours prior to
treatment to ensure that all birds drink or eat enough to get an adequate dose.
WITHHOLDING PERIOD
All drugs, including antibiotics
and chemicals which are used for the treatment of birds and their yards and
sheds, have the potential to form residues in eggs and/or in meat of treated
birds. The residues may persist for some time in the birds and necessitate a
withholding period before their meat or eggs are free of residue and safe for
human consumption. Withholding periods vary. Directions on the container will
indicate the necessary withholding period after treatment. Birds should not be
killed for consumption during this period and any eggs laid during the period
should be discarded. A withholding period also applies to medicinal feed
additives.
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