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Common poultry diseases

Kenny Nutting MRCVS - 14/05/2020

Common poultry diseases

Red Mites

Red Mite (Dermanyssus gallinae) are ectoparasites that feed on the blood of poultry at night. Their numbers increase rapidly during the warmer summer months. These mites have a knack for hiding in the smallest of crevices and can survive for long periods without feeding. It is advised that owners keep a tight vigilance on their poultry houses. Due to the nocturnal nature of red mites they cannot be seen by day. One traditional way to look for them is to go out by night with a torch. However if you enjoy your sleep, then attaching a drinking straw to the perches and blow out the arachnid contents in the morning. Owners should regularly clean out and check in all the corners and cracks to avoid a build-up of these parasites without noticing.

Low numbers of mites can cause irritation and causing the bird restlessness, however large numbers of mites can cause symptoms such as anaemia (Pale comb and wattles), lethargy, reduced egg production, owner complaints of itching and presence of grey/white/red mites around the birds vent area.

Treatment of red mites can be tackled in two ways: firstly by treating the environment by removing all the litter, then washing the shed with a detergent to remove dirt and grease(washing up liquid will suffice), next let the shed dry before applying a suitable disinfectant- Poultry Shield is a cheap, safe and highly recommended red mite disinfectant. After cleaning out mite numbers can be kept down by applying mite powder (Diamataceous earth) to the nest boxes and dust baths to abrade the waxy cuticle of the mites allowing them to dehydrate and die. Secondly  Ivermectin 1% spot on can be used at 1ml/500g of bodyweight,  however this is off label use and an appropriate egg withdrawal period should be set by the prescribing veterinary surgeon- this should be at least 14 days. The eggs from such birds should not ever be sold for human consumption.

Remember treating red mites is a war and not a single battle.



Lice are a very common ectoparasite of back yard poultry there are many different species one of the most common is Menophan gallinae this is a chewing lice which feeds mainly on dead tissue. These lice are flat, golden in colour and found around the base of feathers mainly around the vent region or under the wings. These lice lay clusters of tiny white eggs round the base of feather shafts and in high numbers can cause a lot of irritation affecting behaviour, restlessness and productivity.

Treatment includes Ivermectin 1% spot on, again this is not licensed, or products such as mite powder (Diatomaceous earth) can also be applied to the birds and coop.

Egg peritonitis

Egg peritonitis is a common problem often faced by the vet in practice. It is a disease of many causes often of which cannot be identified. When the oviduct becomes damaged due to viruses such as infectious bronchitis or stressful events causing trauma, causes the oviduct to not be able to “catch” the egg from the ovary, this intern causes internal or so called “blind layers”.

Over time the number of eggs laid internally build up, bacteria gain entry and eggs provide the perfect medium for an incredibly painful infection, if the number of eggs in the abdomen is high enough their can also be impairment of breathing due to pressure against the birds air sacs.

There are four possible treatment options. Firstly the birds could be spayed, this tends to be expensive and rarely done in practice, with a very poor success rate as birds are often presented to vets moribund!, have a hormonal implant of Suprelorin (Virbac) which prevents ovulation and thus no eggs are laid, the implants generally only last 3-4 months and require a replacement, they are expensive and are again not often used. Another option is to provide antimicrobial support, this will help fight the infection for a while and may give the owner time to understand the disease and the ultimate outcome. The final option is euthanasia, these birds are likely to be in a lot of pain and the primary cause unlikely to be treated and it is often the kindest thing to suggest to the owner.

Crop MycosisFigure 1

Crop Mycosis or Sour crop as it’s commonly known is a yeast infection of the diverticulum of the oesophagus known as the crop. This infection may lead to thickening of the crop and dilation of the crop. Disruption of bacteria often caused secondary to antibiotic use and poor quality/mouldy feed allows the commencal Candida albicans to multiply.

Clinical signs include reduced feed intake, poor growth, dull and depressed often with large fluid filled crops and foul smelling odours is emitted around the mouth.

Diagnosis is based upon clinical signs and relevant history. Additional tests such as crop histopathology or microscopic examination of crop smears (mixed with KOH 10% and heated) will diagnose if Fungi is the cause however are rarely done due to time and financial constraints.

Candidiasis can successfully be treated with Beryl’s friendly bacteria (probiotics) for 7 days. This creates a barrier of good bacteria and helps to reduce the fungal overgrowth. If however the fungal overgrowth is severe Nystatin can be used orally.


Back yard poultry can be exposed to two groups of worms they are those found in the gastrointestinal tract (most common) and those found in the trachea. The 4 species of gastrointestinal worms are: Ascaridia, Capillaria, Heterakis and tapeworms.

Ascaridia (Roundworm) are the largest nematodes of birds. The adults live mainly in the small intestine, in high enough numbers symptoms such as ill-thrift, enteritis or intestinal impaction.

Capillaria (Hairworm) is the smallest nematode and can be highly pathogenic these worms can be found throughout the intestinal tract depending on their species but are hard to find with a naked eye. They have a prepatent period of 21-25 days.

Figure 2Heterakis gallinae (Caecal worm) they are predominately found in the caecal sacs and have a prepatent period of 4 weeks. Whilst this worm is relatively harmless it can carry the protozoal parasite Histomonas melagridis which can cause ‘blackhead’ denoted by large ‘hobnail’ liver lesions.

Cestodes in birds tend to be of low pathogenicity and are therefore not considered a problem in most back yard flock situations.

Signs can vary greatly between species or gastrointestinal worms, level of worm burden and individual bird basis. Common symptoms can include Diarrhoea, weight loss, poor growth or depression.

Syngamus trachea (Gape worm) can be found attached to the tracheal mucosal lining and cause the birds to choke and form a characteristic upright posture with their neck extended and mouth open. This worm is uncommon in most back yard flocks unless pheasants are inhabitants of the main flock.

Treatment involves worming with Flubendazole (Flubenvet 1%) for seven consecutive days which has zero egg withdrawal periods and for this reason is most often used.  Worming should ideally be based on proof of worm existence within the clients flock. Worming protocols can either include worming every 2-4 months or getting a worm egg count (WEC) of the flock every 2-4 months and only worm when there is a high enough burden or where Capillaria worm eggs are found.

Prevention can include: good pasture management, regular pasture rotation, adequate stocking densities and Disinfection of coops.

This article was kindly provided by The Chicken VetThe Chicken Vet offer excellent attendance and online CPD on poultry diseases for vets in practice.  The Chicken Vet have teamed up with The Webinar Vet to offer a series of webinars on poultry diseases for vets in small animal practice.  Even if you missed earlier webinars you can still catch up with recordings online.  CLICK HERE for more details.


This article was first published on in 2013.

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