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Birds: Health, Disease and Physiology
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Reviews
of Bird books, including books on health and behaviour
First aid and emergency care for the avian casualty
Helping sick and injured domestic and wild birds
source: Glen Cousquer
In Practice vol 27 no 4, April 2005
starts p190, 12 pages long
Vets often get phone calls about injured birds, and need to provide clear advice and calm the caller, because distress upsets the bird. Some birds can injure the public, and need collection by specialists. Others can be caught with a cloth or net, and put in a dark box with ventilation at the base, so overhead shadows don't overstimulate the bird. First aid may be needed for respiratory distress or bleeding. Vets need to record the location where wild birds are found, so they can later be released there. Some birds, like herons, can stab, others, like falcons, can bite. Birds can be held in a folded towel and hooded if necessary. Domestic birds often suffer from infections, malnutrition and egg binding. Sick birds need their condition stabilised before clinical examination, for example breathing difficulties with oxygen cages and dehydration with fluid therapy. Wild bird casualties tend to be dehydrated, and fluid is essential before solid food. Vets may need to immobilise limbs, and give antibiotic therapy, though intramuscular injections can damage muscles. Birds in shock, such as oiled birds, need darkness, quiet and warmth. Warm water is necessary for crop washing in birds that have been poisoned, and the proventriculus and ventriculus may have to be flushed, if lead shot has to be removed. Oiled birds may need astringents and adsorbents, such as preparations including activated charcoal, to prevent the absorption of poisons from the intestine. Glucose or other nutrients are recommended when birds are not given food.
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Shell shock
Egg colour changes in chickens
source: New Scientist vol 207 no 2770, 24 July 2010 p65
Chickens produce white eggs, though some breeds add a brown coating just before they lay. Shells form over some 20 hours in the hen's uterus, with brown pigment secreted in the last three or four hours. The eggshell is porous, with a waterproof cuticle that can be affected by ageing, infection, or stress in the hen. Stress leads to a release of adrenaline, which halts shell formation. This can affect the cuticle, and so pigmentation. Lack of a cuticle can also mean unprotected pigmentation, so colour can rub off. Pigmentation that does not rub off shows a properly formed cuticle, which helps prevent bacteria invading eggs, and eggs with cuticles are safer for humans to eat.
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Calcium overload
Dangers of giving chickens too much calcium
source: Darold Stenson
Country Smallholding December 2003 p13
Calcium is important for bones, teeth, and growth, and helps with muscle
contraction and blood clotting. Laying hens need calcium supplements, but
too much calcium can cause problems, and even kill chickens, through kidney
failure. The process is slow, and birds may not become ill for some years.
Affected birds may lay fewer eggs, then become less active, and may also limp
Too much calcium in the feed is one cause. Breeder feeds have higher calcium
levels than maintenance feeds, and should only be fed during the breeding
and laying season, not all year round.. Causes also include feeding crushed
oyster shell all year, instead of stone grit, to help with digestion. Chickens
should have access to grit all the time, and only be given oyster shell a
month or so prior to starting to lay, with the oyster shell withdrawn at the
end of the laying season. Breeder feeds, with their higher calcium levels,
are designed to boost egg production, and reducing calcium levels may affect
production, so chicken keepers may also need to think about whether their
birds should have more natural lives, with lower calcium levels, and laying
fewer eggs.
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Faster, cheaper, sicker
Health problems arising from over-selective breeding of chickens
source: Joyce D'Silva
New Scientist no 2421, November 15 2003 p19
The consumption of chicken broilers worlwide has risen to 49 billion from
under 8 billion in the 40 years to 2003, while the time taken to grow chickens
to some 2 kilos has dropped to 41 days from almost three months in the three
decades to 2003.
Problems can arise in particular from very selective breeding used to produce
fast-growing chickens. Compassion in World Farming aims to end this problem
through seeking a judicial review of British government policy on selective
breeding.
The gene pool of chickens is narrowing. Three companies account for 98%
of meat chickens and their descendents world wide. Too-rapid growth can
lead to skeletal problems, and as many as 20% of birds may suffer from consequent
lameness. Lame chickens choose to eat feed with painkillers, and this helps
them to move more normally, according to researchers from the University
of Bristol, England. Liver and heart problems are also associated with too-rapid
growth. The diets of fast-growing chickens are restricted, when they are
not slaughtered at an early age, but instead kept to their breeding age
of 20 weeks, since mortality rates are high if these chickens are allowed
normal rations. This dietary restriction leaves the chickens chronically
hungry. This contravenes a 1998 European Union directive that states that
animals should not be farmed of they cannot be kept without health or welfare
problems linked to the animals' genotypes.
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Beak trimming
Trimming the beaks of poultry can harm their health
source: Victoria Roberts
Country Smallholding November 2002
starts p18, 2 pages long
Trimming the beaks of poultry can cause pain to the birds and prevent their
picking up food, so the birds may not grow properly. It was once used as a
way to stop poultry damaging one another so that they could be kept in a more
confined space. More space per chicken is now seen as a better solution. Free-range
poultry keepers tend not to trim beaks. A poultry keeper buying from a supplier
should tell them that they do not want chickens with their beaks trimmed.
Trimming beaks is mutilation. The beak may have to be re-trimmed if not properly
trimmed at first. Calcium supplements do not help birds with trimmed beaks,
and could affect egg production.
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Birds eye
Small eye pupil in chicken
source: Victoria Roberts
Country Smallholding November 2002
p18
Chickens may suffer from eye disease which results in the pupil of an eye
becoming very small. This could be the result of a viral infection. The pupil
sometimes recovers, though not always, and affected birds appear to retain
some vision. Chickens may be otherwise healthy, but could become targets for
bullies in the flock. There is a possibility that the condition could be inherited,
so it is best not to use affected hens as breeders.
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Incidence and antibiotic resistance of pathogenic Escherichia
coli among poultry in Belgium
Avian E.coli and antibiotic resistance common among Belgian
poultry
source: F. Vandemaele et al
Veterinary Record vol 151 no 12, September 21 2002
starts p355, 2 pages long
Escherichia coli is also called avian pathogenic E.coli (APEC) when it affects
poultry. Infections tend to start in the trachea, spreading to the lungs and
then the internal organs. The oviduct may become infected, which affects egg-laying,
and the infection can be fatal. The meat of broilers may also show fibrous
lesions.
A survey of birds studied at East-Flanders regional laboratory, Belgium,
has found that 17.7% of broilers were affected. A sample of dead or diseased
egg-layers found a higher rate, of 38.6%. This high rate was because of the
type of sample, and the incidence of 17.7% is more accurate. APEC infection
was found in 153 of 503 Belgian poultry farms surveyed in 2000.
APEC is most commonly treated with antibiotics, but this survey found high
resistance, with most APEC strains resistant to two or more of five antibiotics.
Resistance to tetracylines was found in 66% of 98 randomly selected strains
of APEC in 2000, and resistance to ampicillin/amoxycillin was found in 59%.
Half the strains were resistant to trimethoprim plus sulphonamide, and 36%
to flumequine. Resistance to enrofloxacin was least common, and was found
in only 13% of the strains. Only 5.1%s showed resistance to the five antibiotics,
but 27.55% were resistant to four antibiotics, while 17.35% were sensitive
to all five, a low figure.
Alternative measures, such as vaccination, should be used, given this high
resistance to antibiotics, and the public health concerns involved.
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Soft shells
Causes of hens laying eggs with soft egg shells
Source: Victoria Roberts
Country Smallholding October 2002 p23
Hens may lay eggs with soft shells because they have oviduct infections affecting
the shell gland. Terramycin powder may help, and it can be administered in
the hen's water. Young hens may also be affected by Infectious Bronchitis,
which may mean that their eggs never have shells. Hens may start to eat their
own eggs, and once they do this, it is not easy to get them to stop. Triggering
broodiness may help, for example by excluding light from the nest box and
placing eggs in it.
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Pancreatic atrophy in a peregrine falcon (Falco peregrinus)
Case of young peregrine falcon with pancreatic atrophy
source: J.H. Samour and J.L. Naldo
Veterinary Record vol 151 no 4, July 27 2002
starts p124, 2 pages long
The pancreas is involved in the production of insulin, levels of which are
lower in birds than in mammals. Pancreatic atrophy has been reported in a
budgie and a macaw. This case involves a female peregrine falcon some eight-months-old,
studied in the Falcon Medical Research Hospital in Saudi Arabia. The bird
was initially in good condition, though trematode ova were found in her faeces,
and the falcon was treated for this.
Nine days afterwards the falcon was checked again, and was found to have
dropped in weight to 828 grams from 928 grams, though she was reported as
eating normally. Mild air sacculitis and lung congstion were noted, and she
was admitted to the hospital with a tentative diagnosis of air sacculitis
and mild pneumonia. Her faeces were large and solid, and no endoparasites
were found, while her white blood cell count was moderate high, and heterophilia
was noted. Her weight dropped to 680 grams after a week, though she was eating
well. High serum amylase was noted, suggesting pancreatic disorder. She still
lost weight, though she was eating large amounts, and she developed coprophagia
on the tenth day following her admission, eating her faces immediately after
passing them. She died on the 14th day after entering the hospital.
A post-mortem found her pancreas to be dark grey-purple, small and mottled,
and other findings were consistent with reactive pancreatitis and pancreatic
atrophy. Clear diagnosis was not possible when the falcon was admitted. It
is rare that clincial diagnosis can be achieved with living birds with pancreatic
disorders, though serum amylase levels may be a helpful indicator. There is
a need for more information on serum amylase ranges in normal birds. The peregrine
in question had levels of 2508U/litre, which is very high, ie higher than
the upper limit previously noted at the hospital. The peregrine was probably
already too ill for therapy to have had any effect, though a tentative diagnosis
was made that she was suffering from a pancreatic disorder.
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Chicken droppings
Worm parasites can affect hens
source: Victoria Roberts
Country Smallholding August 2002 p19
Hens can suffer from parasites in the caecum, which is a section of the gut
where fermentation of plant food takes place, as part of digestion. The caeca
are emptied with every tenth or so dropping, and this type of dropping tends
to be paler and may be foamy. The colour and consistency of droppings are
also affected by the hens' food. Sometimes hens can suffer from worms in their
caeca, which turn droppings foamy, and the flock will then need a worm treatment,
such as Flubenvet.
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Incubating Pekin bantam eggs
Low temperatures in an incubator can lead to chicks with
deformed legs
source: Victoria Roberts
Country Smallholding August 2002 p19
Newly hatched chicks may suffer from deformed legs if eggs are incubated
at temperatures that are too low. This may happen when hens leave eggs for
too long, and if incubator temperatures are not correct. The incubator temperature
should be 37.7 deg C or 100 deg F, taken using a thermometer on the top of
the egg. Temperatures at the egg may be too cool if 37.7 deg C is only achieved
in the top parts of incubators rather than lower down where eggs are located.
Incubators should also be thoroughly cleaned with Virkon after use, since
bacteria breed fast in incubators. Too high humidity levels should be avoided,
since this can slow hatching.
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Newcastle disease outbreaks in Italy during 2000
Inquiry into Newcastle disease epidemic in Italy
Source: I. Capua et al
Veterinary Record May 4 2002
starts p565, 4 pages long
There was an epidemic of Newcastle disease in central and northern Italy,
following a serious epidemic of avian ‘flu, in 1999 and 2000. Newcastle
disease is caused by a virus, avian paramyxovirus serotype 1, and is extremely
contagious, as well as serious, with a death rate of over 50% for chickens.
The preceding avian ‘flu epidemic lead to the loss of more than 13 million
poultry from infection and culling. This meant that eggs were imported from
outside Italy, and chickens were kept in greater stocking densities where
the ‘flu epidemic had not hit, since supply had dropped elsewhere. Vaccination
programmes to protect against Newcastle disease were reduced or abandoned
because the population was not homogenous, and there were also fears of the
impact of reactions to vaccines where the birds were overcrowded.
These conditions favoured the emergence of Newcastle disease, and 254 outbreaks
were dealt with from May 5 2000 to December 31 2000. Backyard flocks accounted
for 219 of the outbreaks, 17 occurred at dealers, with a further 17 at intensively
reared establishments, and one ostrich farm was hit.
The symptoms included listlessness, depression, tremors and wing paralysis,
with birds dying between 24 and 48 hours after showing symptoms.
The infection was traced to a broiler hatchery, which had imported eggs from
elsewhere in Europe, and the disease then spread to dealers, and from dealers
to farms. The most susceptible birds were guinea fowl and chickens, with ostriches,
pheasants and turkeys also affected, but less susceptible. The disease may
have entered the hatchery through faeces on egg shells. It is not clear where
it came from, but it may have been undetected in countries using a vaccination
programme, since it is more likely to be detected where the population is
immunologically naïve, where the clinical disease is more likely to appear.
There is a need for more monitoring to detect the disease in Europe. There
were also problems during the Italian epidemic due to the large numbers of
backyard flocks involved. Imposing a protection and surveillance zones for
many small flocks involved a great deal of effort. There is a case for less
stringent controls, since outbreaks tend to be self-limiting when they occur
in naïve backyard flocks. There are problems in defining ‘backyard
flocks’ and this could be done by looking at where the birds are slaughtered
and consumed, and whether consumption is local, or whether the birds go into
the industrial circuit.
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Eggs and chilli
Dealing with egg-eating in hens
source: Victoria Roberts
Country Smallholding May 2002 p23
Hens may start eating eggs after laying a soft shelled egg. Eating a soft-shelled
egg can teach them that eggs are good to eat. It’s better to prevent
egg-eating, as it’s not easy to stop it once the hen has begun. Hens
should have grit so that the egg shells are strong, and the nest box should
be kept dark, with the entrance curtained using a vertically cut bin bag or
other methods. Objects that look like eggs, such as golf balls, can also be
used to confuse birds, and give signals for young birds to find laying places.
Adding chilli to a hen’s food does not work, since hens do not find chilli
to be hot.
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Mis-shaped toes
Bent toes in chickens
source: Victoria Roberts
Country Smallholding April 2002 p20
Bent toes in chickens are often inherited, though they may have other causes.
Inappropriate temperatures in incubators can also lead to curling toes, as
can vitamin deficiencies. Chicks born with club-shaped feet have to be culled,
due to their inability to walk. However, toes that are only slightly bent
do not seem to have adverse effects on chickens’ production, though they
may be more vulnerable to arthritis.
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Off-colour hen
Significance of purple combs in chickens
source: Victoria Roberts
Country Smallholding April 2002 p21
Chickens with purple combs have circulatory problems, especially heart disease.
There is usually no treatment, though sometimes a broad-spectrum antibiotic
can help, if the condition is due to a bacterial infection. This condition
tends to affect older birds and chickens from large breeds, which may go purple
when they are washed in preparation for a show. Chickens with purple combs
tend to become sluggish, due to oxygen deprivation, and they may have green
droppings, since the bile content rises.
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Paralysed Hamburg
Symptoms of Marek’s disease, and its prevention
source: Victoria Roberts
Country Smallholding April 2202
starts p20, 2 pages long
Some ‘well bred’ large breeds of chickens are vulnerable to Marek’s
disease, which is a viral disease that stops legs from functioning, though
they still have feeling. One or both legs may be affected. There is no cure,
so the chickens have to be culled. Stress can trigger attacks, and attacks
often come when chickens are about to come into lay.
Infected chickens are infectious for life, and the virus can persist in the
dust of poultry houses for 12 months. Vaccination is one way of tackling the
problem, though it has to be continued with each new chicken bought, and new
generations of chickens, once a vaccination programme has started. Culling
is another solution.
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Unwelcome carrion
Dead crow found in Canada had West Nile virus
source: New Scientist September 1 2001 p5
A dead crow found in Windsor, southern Canada, was carrying West Nile virus.
The health ministry in Ontario plans to analyse dead birds and mosquitoes,
which can carry the virus. Quebec, next door to Ontario, is considering fumigation
as a way to eradicate mosquitoes.
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Red kite comeback may help restock Europe
Red kite numbers increase in Britain, but kites face
threat from rat poisons
source: Brian Unwin
Independent January 1 2002 p3
Numbers of red kites are increasing in the UK, while they are falling in
other European countries, including Spain. Many kites used to restock Britain
had come from Spain, and Britain may end up providing kites for locations
in mainland Europe.
Red kites are under threat from brodisacoum and bromadioline, used as rat
poisons. They were also attacked by gamekeepers from the late 18th century,
only surviving in central Wales, until they were reintroduced in Scotland
and England from 1989. There are 431 pairs of kites in the UK in 2002, compared
with 69 pairs in 1989.
Gigrin Farm in Powys, Wales, attracts large numbers of tourists to watch
its kite gathering. The farmer feeds kites with meat, and over 150 kites go
to feed there.
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Poisoners threaten Scotland’s red kites
Scottish red kites hit by poisoning
source: Paul Kelbie
Independent January 28 2002 p9
Around a third of Scotland’s red kite population has died as a result
of poisoning. Illegal poisoning of kites was worse in 2001 than it has been
since 1989, when red kite reintroductions started in Scotland. Gamekeepers
see red kites as pests, and have been seeking to have a legal right to kill
them, since they see kites as a threat to pheasants and grouse. There was
a two-fold rise in poisoning in 2001 compared with 2000, and 36% of the kite
population of the Black Isle, a pioneering location for reintroductions, died
in that year. The Black Isle red kite nests produced 223 chicks in the ten
years from 1989, and just 40 breeding pairs remain in Scotland.
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Birds
Disease reports on British poultry and other birds
source: Veterinary Record January 19 2002
starts p63, 2 pages long
Reports of disease outbreaks in British poultry include heavy mortality from
the northern fowl mite in a backyard flock, and problems arising from a farmer
giving the wrong food to turkeys before Christmas 2001. The birds were being
fed non-medicated feed, and the farmer ran out of this, giving the birds feed
with lasalocid sodium instead. Some four to five days following this change
of feed, some birds fell ill, with 18 deaths from a flock of 34 birds. Ionophore
toxicity was diagnosed. Meanwhile, Salmonella pullorum has been found in a
free range hen in Wales. This type of salmonella is no longer found in commercial
flocks, but does sometimes appear in hobby flocks, and is probably still found
in wild birds.
Meanwhile, an unvaccinated flock of tumbler pigeons from Newcastle was found
to be infected by paramyxovirus type 1, and a peacock was found to be suffering
from Capillaria, or hairworm, infestation. Capillaria can cause problems such
as emaciation, especially in backyard flocks.
Other reports of diseases in birds are mentioned in this article.
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Spicy chicken
Capsaicin reduces Salmonella enteritidis infections in
chickens
source: New Scientist August 25 2001 p5
Research at Virginia Tech University, Blacksburg, has found that chickens
given food containing capsaicin, found in chilli peppers, were less likely
to carry Salmonella enteritidis internally in their organs. The birds were
exposed to the bacteria, and the number of infected birds was halved if they
had been given capsaicin. Chickens do not appear to be able to taste chilli
peppers as hot, and the meat from chilli-fed chickens does not appear to taste
of chilli either.
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Chickens stand down
Chickens do not appear vulnerable to West Nile virus
source: New Scientist June 2 2001 p17
Chickens appear to be unlikely to be infected by West Nile virus, a disease
carried by mosquitoes, which don’t seem to like chickens. Canadian health
authorities had put chickens on the US-Canadian border, in an attempt to detect
infection coming from the US, but the chickens have been withdrawn from border
patrol after the discovery that they don’t seem vulnerable to the disease.
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Observations on the significance of diagnostic findings
in egg-binding of Psittaciformes
Egg binding in the parrot family
source: M-E. Krautwald-Junghanns, V.M. Kostka and H. Hofbauer
Veterinary Record (1998) 143
starts p498, 5 pages long
A survey of 2,192 Psittaciformes has found 60 birds, (2.74% of the sample)
cases of egg binding. The parrot family is not easy to sex, so the sample
included males, estimated at around half the total. Egg binding is especially
common in cockatiels, at 15.75% or 20 birds of 127, and budgerigars, at 5.37%,
or 19 birds of 354, in this sample. It is rare in some parrot species, eg
the Amazona species at 0.18% (one bird of 555), and Psittacus species (including
African Grey parrots), at 0.22% (one bird of 464). Rates for the Ara species
(including blue and yellow macaws) were 4.7% (seven birds of 149), and for
Cacatua species (including sulphur crested cockatoos) were 2% (3 birds of
149).
Egg binding can be linked to malnutrition. Vitamin D, vitamin E, selenium
and calcium supplies are important for successful breeding. Stress may be
a contributory factor, eg long daylight hours, low humidity, an unsuitable
temperature range, and social stress, from a new bird partner, or from humans,
may also contribute. Egg binding may also be directly caused by weak or absent
tonus of cloacal musculature or the oviduct, large eggs, eggs with soft or
no shells, or rough surfaces, and adhesions affecting the oviduct and eggshell.
Affected birds are more likely to be caged than in an aviary, but being paired
or single appears to make no difference. Birds are more likely to suffer from
egg binding if they have never bred before. Four of the sample had previously
bred, though 32 of the others had previously laid eggs, and 24 were laying
for the first time. Seasonal factors do not appear to be important. Reproductive
tract disease was evident in 36 cases.
Symptoms included a swollen abdomen in all cases, with 36 of the birds having
problems with defecation. Other symptoms can include being unable to fly,
and standing in a wide-legged way.
A diagnosis was possible in 70% of cases just by looking at the bird, taking
the bird’s history, and palpating its abdomen. Radiography helped in
diagnosing birds with eggs deep inside the bird, but eggs with thin or no
shells could not be reliably diagnosed either by palpation or radiography.
Radiography was also little help in diagnosing eggs with laminated shells.
Ultrasonic examination helped in diagnosing eggs with defective and thin shells,
but roughness of egg shells was not easily observable using ultrasound.
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Saving Polly
Cures for avian cancer being developed in Australia
source: Julia Hinde
New Scientist December 25 1999 p11
Australian scientists are developing cures for avian cancer, which affects up to 30% of older budgerigars. Pet birds like budgies, cockatiels and parrots are usually treated by surgery, and may have to be put down. Lucio Filippich from Queensland University, Brisbane, is carrying out a trial using cisplatin, using sulphur-crested cockatoos as subjects. He is working with Queensland University colleagues, and the Commonwealth Scientific and Industrial Research Organisation, Australia. An avian cancer clinic may be set up in 2000 at the university's teaching hospital for small animals.
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I spy with my duck's eye
Ducks sleep with half their brains awake
source: Alison Motluck
New Scientist February 6 1999 p8
Ducks can sleep with half their brains awake, according to research on mallard ducks, carried out by Indiana State University researchers. Niels Rattenborg and his team argue that birds maintain alertness in half their brains as a precautionary measure. They found that birds were more likely to sleep with one eye open if they were located on the edge of sleeping groups. These birds could detect video images of predators in less than a second. The birds were videotaped, and also given electroencephalograph tests, which showed that one brain hemisphere was in slow-wave sleep, and the other hemisphere, opposite the eye that was open, was alert. This research was reported in 'Nature', vol 397, p397.
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