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MANAGING AND TREATING COMMON DISEASES OF
BACKYARD POULTRY
Author : Stephen Lister
Categories : Vets
Date : July 8, 2013
STEPHEN LISTER continues his advice for veterinarians who may have clients expecting
treatment for poultry, by looking at the most common disorders
THIS is a second part of an article about the management and treatment of disease in
backyard poultry.
As discussed in the previous article (VT43.22), interest in keeping poultry continues to increase
and with this growth comes the expectation from owners that the same veterinarians who are the
custodians of the health and welfare of their other pets will also be able to offer them the necessary
advice and treatment for their birds.
The previous article gave the background to backyard poultry keeping, disease diagnosis,
vaccination and medication. This second article will consider some of the more common disease
situations that may present to the practitioner.
As in all clinical situations, a thorough examination of sick poultry should be system based,
concentrating on differentiating issues affecting the reproductive system, the respiratory tract, the
intestinal tract and skeletal system.
Reproductive problems
Some birds simply “run out of steam” and the oviduct/ ovary may close down and egg production
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cease for no pathological reason. Other birds, especially at the start of the natural laying season as
day length increases in the spring, may exhibit one of the most common conditions of laying
hens – egg peritonitis. This may result from a “ripe” ovum (or multiple ova) breaking off from the
ovary and coming to lie in the abdomen, having failed to enter the oviduct. Another cause may be
ascending bacterial infection of the oviduct.
The end result can be a fulminating peritonitis and toxic septicaemia. Acutely affected birds may
present with a tense or swollen abdomen. In more chronic cases, birds may cease lay, go off their
feed and lose weight. If caught early then systemic antibiotic treatment by injection or orally may
bring about a clinical cure, but the prognosis is usually poor.
Some specific viral infections – for example, infectious bronchitis (IB) – may cause pathological
changes in the ovary and oviduct leading to malformed or soft-shelled eggs or simply reduced egg
production. The effects may be transient or prolonged.
A similar picture may be precipitated by an inadequate or poorly balanced diet or may be
secondary to a heavy parasite burden.
Respiratory problems
Damage to the respiratory tract can occur through disease challenge or environmental insult.
Environmental effects can relate to poor ventilation, high levels of dust and ammonia. This may
result in low-grade conjunctivitis or severe keratitis in severe cases. Treatment should be aimed at
removing the noxious irritation by improved hygiene and ventilation. Topical application of antibiotic
eye ointments to reduce bacterial contamination and lubricate eyelids may be of benefit.
Dry, dust-free, good-quality wood shavings make the best bedding material. Even then, this should
be regularly changed or topped up. Mouldy bedding increases the risk of exposure to fungal
spores, predominantly Aspergillus fumigatus,leading to chronic air sac damage and the
development of fungal nodules in lungs or air sacs, causing chronic respiratory distress or loss of
condition and eventual death.
Infectious bronchitis is a common viral infection caused by an avian coronavirus. Clinical
manifestations of infection can be seen as conjunctivitis, nasal discharge, swollen sinuses or mouth
breathing. The IB virus is very contagious and easily spreads between an infected group in only
two to three days, but is often self-limiting. Infection may be complicated if there is a concurrent or
underlying Mycoplasma or other bacterial challenge resulting in mortality often described by the allencompassing syndrome of chronic respiratory disease (CRD). IB vaccines are available against a
variety of IB variant strains. Uncomplicated infections will not require treatment, but if contributory
Mycoplasma or other bacterial involvement is suspected, then appropriate antibiotic therapy may
be required, for example, with amoxicillin, chlortetracycline or, in severe cases, with enrofloxacin.
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There are two significant Mycoplasmas affecting chickens – Mycoplasma gallisepticum and
Mycoplasma synoviae. Both can cause respiratory disease, resulting in coughing, nasal discharge,
swollen infraorbital sinuses and conjunctivitis. The end result can be loss of vigour, mortality and, if
there is severe damage to air sacs, chronic gasping and loss of body condition. Following initial
infection of the flock, birds may recover with appropriate treatment, but the Mycoplasma may
remain latent and re-emerge, causing a further episode of clinical disease when other diseases or
stress factors precipitate problems. This may include mixing of new birds, the onset of egg laying or
adverse weather conditions.
Specific drinking water treatment options for Mycoplasma infections in acutely sick birds include
tylosin, tilmicosin, tiamulin, Aivlosin, enrofloxacin, Linco-Spectin and tetracyclines. Treatment tends
to reduce clinical disease without totally eliminating infection and further treatments may be
necessary if disease flares up as a result of stresses discussed above.
Control of infection requires maintenance of a closed flock as much as possible, avoiding markets
or buying birds at shows. Mycoplasma vaccines are available but would only be required for
backyard flocks for particularly valuable breeding stock or where significant problems had been
seen previously.
Intestinal problems
Intestinal issues may be caused by a mix of infectious, managemental, nutritional and
environmental factors. Sour crop or crop binding may occur due to birds gorging on feed or may
reflect blockage further down the alimentary tract (for example a gizzard impaction).
Mildly affected birds may be treated by gently massaging the crop to remove the contents, which
are frequently foul smelling due to fermentation. More severely affected cases may require minor
surgery. Gizzard and duodenal impactions usually result from the ingestion of long lush grass or
tough fibrous material. There is no easy treatment for such impactions as these are frequently only
diagnosed following a failure of the crop to empty or chronic weight loss. Avoiding access to long
lush grass or the provision of ad-lib hen grit, especially in the spring, may prevent the condition.
Coccidiosis is an important disease of poultry kept in extensive and intensive systems worldwide,
causing enteric disease, poor growth and, potentially, mortality. The severity of the disease in
specific flocks is related to the weight of challenge and the species of Eimeria involved. The life
cycle of all species affecting chickens and turkeys is direct, with the ingestion of infective
sporulated oocysts, invasion of the intestinal mucosa, asexual and sexual development and
multiplication causing pathological damage. Treatment of infection is with an effective coccidiocide
such as toltrazuril or amprolium. Prevention and control of infection involves high standards of
hygiene, especially the prompt and regular removal of droppings and contaminated bedding, and
good drinker management to prevent areas of damp bedding within accommodation.
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A commercial vaccine is available. By arrangement with the Poultry Club of Great Britain, its
members can purchase small 100 or 200 dose packs on veterinary prescription.
Nematode worm infestations are common in backyard poultry predominantly intestinal, but
occasionally gapeworms affecting the respiratory tract. Worm types commonly seen include the
following.
• Roundworms (Ascaridia species). These are the largest and most common. They are white, up to
5cm long, and may be visible in droppings in heavy infections.
• Hairworms (Capillaria speces). These are much smaller, hair-like and are barely visible with the
naked eye, but can cause significant damage to the intestinal tract even in only moderate
infestations.
• Caecal worms (Heterakis gallinarum). These worms spend most of their time in the caeca,
frequently causing no obvious harm, but are known to carry the protozoal parasite, Histomonas
meleagridis, the cause of blackhead.
• Gizzard worm (Amidostomum anseri). These worms can cause significant ulceration of the
gizzard at the proventriculus/ gizzard margin especially in ducks and geese and can lead to severe
loss of weight, anaemia and weakness, especially in young goslings.
• Tracheal worms (Syngamus trachea). These worms live in and irritate the lining of the trachea,
leading to a specific form of respiratory distress, described graphically as gapes – giving rise to the
common name of gapeworms.
Diagnosis of worm infestations may be suggested by rapid loss of weight (birds “going light”), but
in very heavy infestations birds can become weak and anaemic. Roundworms are occasionally
seen in droppings, but worm egg counts on pooled droppings are the most helpful diagnostic tool.
Heavy burdens of adult or larval stages may be visible in the intestines at postmortem or as
demonstration of typical nematode worms on intestinal scrapings.
Flubendazole is the only licensed wormer in the UK, (Flubenvet, Elanco Animal Health). It is
available for incorporation in bulk feed by feed compounders, or for backyard flocks in a small 60g
pot for mixing with feed at home. In addition, a water medication is available, Solubenol (Elanco
Animal Health), which can be given via the drinking water.
External parasites
Several mites and lice can affect poultry. Some biting lice can cause minor irritation and others can
colonise feather shafts affecting feather waterproofing and development. Mites (burrowing and nonburrowing varieties) can cause significant problems in heavy infestations.
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More specifically, the poultry red mite (Dermanyssus gallinae) is a common blood-sucking mite.
The adult mites can live for a year or more in dark cracks and crevices in an empty building without
needing to take a blood meal. They tend to feed on birds at night and are voracious blood-suckers
capable of causing clinical anaemia in heavy infestations. Control is by careful administration of
suitable insecticides properly applied into all cracks and crevices. Owners may need to take
specialist advice, as some products are not suitable for spraying in the presence of birds or eggs.
The northern fowl mite spends most of its time living on the birds, frequently living around the base
of the tail where heavy infestation can lead to loss of condition and unthriftiness. Treatment is by
topical application of a suitable insecticide although none are specifically licensed for direct
application to birds.
Scaly leg mite (Cnemidocoptes gallinae) is a burrowing mite of poultry, affecting mainly the shanks
of the legs, leading to thickening and deformity of the scales of the lower leg. Severe infestations
can cause very deep lesions, with cracking of the skin allowing secondary bacterial infection. A
diagnosis can be confirmed on skin scrapings. Systemic treatment with avermectins by injection or
spot-on application can be effective, although this is an offlabel use under the cascade and care
must be taken of treating animals for supplying eggs for human consumption.
Skeletal problems
The most common cause of individual lameness in backyard poultry is probably bumblefoot.
This is a chronic foot infection usually associated with Staphylococcus infection. It may be caused
by poor conditions underfoot, previous wounds, or poor provision and/or quality of perches. The
foot is swollen and may or may not be hot to the touch. Injection with antibiotics together with hot
poulticing may remove infection, but prolonged follow-up oral antibiotic therapy may be indicated.
More chronic lesions may require radical surgery, but where there is significant associated
osteomyelitis, euthanasia is advisable.
In young, growing birds, lameness may be associated with poor bone mineralisation and rickets.
This condition is acutely painful and birds will be acutely lame. The bones of the limbs and beak will
be pliable. Treatment with watersoluble vitamin D3 and correcting any mineral imbalance in the diet
usually produces a dramatic recovery.
A common textbook disease of lameness in poultry is Marek’s disease. The condition was
previously named fowl paralysis due to the polyneuritis caused in peripheral nerves. Marek’s
disease is caused by a herpes virus infection. Very early infection of young birds may go unnoticed,
with the virus finding its way to nerves or other tissue where it lies dormant, to be reactivated by
later stresses, such as moving or mixing groups or the onset of lay.
Tumours can develop in several organs, with clinical signs depending on where the tumours
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develop. Classically, tumorous infiltration of the brachial and sciatic nerve plexus leads to wing
drooping or leg paralysis respectively. Control is by a combination of good hygiene and early
vaccination. Vaccination is by injection at one day old. Vaccines available for use in small scale
poultry keeping are freeze dried and come in 1,000-dose vials that need to be reconstituted with
specific diluent. Some small domestic poultry keepers can develop effective strategies to batch
vaccinate a week’s hatch. This obviously needs careful planning and attention to detail. Expert
advice is available from the vaccine manufacturers.
As the virus is very persistent and shed in feather dander, effective cleansing and disinfection of
hatching environment with effective virucidal disinfectant is of paramount importance in enabling
vaccines time to develop immunity.
Conclusions
Backyard poultry keeping is increasing in popularity and owners have an understandable
expectation their veterinary surgeon will have the skills to diagnose, treat and advise on a range of
the most common conditions likely to affect these birds.
The veterinary profession has a duty of care in this area and vets are well placed to offer this
advice and treatment to ensure the health and welfare of this growing population of companion
animals. Time spent on knowledge transfer within the veterinary profession will ensure this type of
approach can be offered by a wider number of practices to their pet-owning client base.
• The advice and support of Janice Houghton-Wallace in the preparation of this article is gratefully
acknowledged.
Further reading
Houghton-Wallace J and Lister S (2012). Backyard Poultry 1. Husbandry and general
management, In Practice 34: 136-145.
Lister S and Houghton-Wallace J (2012). Backyard Poultry 2. Veterinary care and disease
control, In Practice 34: 214-225.
Pattison M, McMullin P, Bradbury J M and Alexander D J (eds) (2008). Poultry Diseases
(6th edn). Elsevier. ISBN 978-0-7020-2862-5.
Roberts V (2009). Diseases of Free Range Poultry(3rd edn). Whittet Books. ISBN 978
1 873580 78 3.
Houghton-Wallace J (2007). Not Just For Christmas – a complete guide to raising turkeys.
The Good Life Press (www.thegoodlifepress.co.uk). ISBN 978 1 904 871 18 7.
British Veterinary Poultry Association www.bvpa.org.uk
The Poultry Club of Great Britain www.poultryclub.org or email [email protected]
The Poultry Site at www.thepoul trysite.com or email info@thepoul trysite.com
Veterinary Medicines Directorate (VMD) www.vmd.defra.gov.uk
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Responsible Use of Medicines in Agriculture www.ruma.org.uk
Heavy ascarid roundworm burden in the small intestine of a hen at postmortem.
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Chickens can graze pens quite heavily.
Above : Rhode Island Reds in a welllittered hut.
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Left : Conjunctivitis and upper respiratory tract involvement can suggest viral or
Mycoplasma involvement.
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Red mite infestation. Note very pale carcase and mites engorged with blood.
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