Respiratory Disease in Poultry ‐ Quick Consult Guide

Diagnosis:

Apart from Aspergillus (which is terminal) and Gape worms which are rare in poultry most respiratory diseases present similarly. A specific diagnosis is not really helpful and will not really alter the treatment. Where a specific diagnosis is useful is if the owner wants to vaccinate future birds against diseases on their holding.

Post mortem ‐ PMs are rarely useful for giving a specific diagnosis except for gape worm where red worms are found in the trachea (see photo above). Lesions may include:

• Conjunctivitis
• Sinusitis (can vary from a mild mucoid exudate through to inspisated pus)
• Tracheitis
• Airsacculitis (cloudy air sacs, neovascularisation and pus/mucus)
• Egg peritonitis (due to muco‐cilliary escalator damage allowing inhaled pathogens into the air sacs which cross over into the confluent abdomen/thorax
• Septicaemic signs (fevered carcase, inflamed liver, spleen and kidneys)
• White urate deposits in the kidneys and ureters

Serology is often the best method for a retrospective diagnosis of IB, ART, Mg, Ms and Mm. It is worth waiting at least two weeks after clinical signs before submitting blood for serology as the birds will need time to seroconvert (Send in blood in plain tubes). It is often worth taking paired blood samples for serology to look for rising titres. Note if vaccines have been given this needs to be taken into account before interpreting serology results.

Chicken vet offers serology for the diagnosis of respiratory disease along with full veterinary interpretation. Contact us for more details.

To diagnose ILT it is best to use histopathology of the trachea to look for eosinophillic intra‐ nuclear inclusion bodies which are almost pathogonomic for this condition. Serology can prove unreliable.

Aspergillus can be cultured from suspicious lesions on a suitable fungal medium.

As time goes on PCR testing is becoming much more popular for diagnosis  respiratory disease however for backyard flocks this maybe to expensive, contact for more details.

If you suspect NDV or AI please contact DEFRA.

Treatment options:

• Irrespective of the underlying pathogens the treatment for respiratory disease is mostly the same.
• A mild respiratory disease case where the bird is snicking(sneezing) but is otherwise fine will likely recover without the need for antibiotics. Mintamix is a plant extract based decongestant which will help birds breathe.
• If the bird is unwell, the clinical signs severe or the signs are not resolving then antimicrobials may be indicated. Even if the cause is viral you will want to protect against secondary bacterial infection.
• There are a number of antimicrobials available but it is important to use those which have activity against Mycoplasma and secondary pathogens if you are unsure about the diagnosis.
• For the majority of conditions many vets will use Fluoroquinolone (Enrofloxacin) which  is  a  broad  spectrum  powerful  antimicrobial  (which will kill Mycoplasma) however I am concerned about overuse leading to resistance and its harmful effects on the intestinal flora.
• Doxycycline and Tetracyclines are broad spectrum antimicrobials which have activity against Mycoplasma and secondary pathogens such as E. coli. Generally either antimicrobial is given for five days at 20mg/Kg in drinking water. It is worth noting that there is considerable resistance to Tetracyclines.
• Macrolides such as Tylosin (Tylan) are commonly prescribed as they are effective against Mycoplasma but they have a narrow spectrum of activity against other secondary pathogens. Tylan can be given up to 200mg/Kg for five days.
• Tiamulin (Denagard) is licensed against Mycoplasma but like Tylosin has poor activity against secondary pathogens. A typical course of Denagard is 2ml/Litre of drinking water for five days.
• Aminoglycosides such as Lincospectin can be used effectively (for up to seven days  at 50mg/Kg) as they have activity against both Mycoplasma and E. coli.
• Gape worm can be treated with Flubenvet 1% in feed for seven consecutive days at 3g/Kg
• There is no successful treatment for Aspergillus
• When treating respiratory disease it is often advised to treat the entire group of birds as many of them will likely have subclinical disease.
• Many antimicrobials destroy the gut flora and it is recommended about a week after the end of treatment to give a probiotic such as Beryl’s to repopulate the intestine with ‘friendly bacteria’.

Prevention:

Prevention of respiratory disease like other diseases is based upon biosecurity.  Always obtain birds from a reliable source (local markets and eBay are bad sources). Ideally quarantine new birds for three weeks before introducing them to an existing flock. If your client has high value birds then testing them before admitting them to the flock may be a good idea.

• Trying to keep wild birds and vermin away by keeping feed stored in metallic containers and not placing feed on the ground or in the sight of wild birds.
• Minimising stress will reduce the chances of respiratory disease taking hold and should help reduce the chances of recrudescence in latent carriers. This means avoiding stresses such as poor diet, over stocking, extremes of temperature, draughts and poor ventilation. Note poor ventilation can lead up to high ammonia levels which can damage the cilia leaving the respiratory tract more vulnerable to infection.
• Vaccination is possible for respiratory disease but it is not straight forward.

Key points to remember