By Dr   BSc, BVSc, MRCVS, MACVSc (Avian health)

As veterinarians, one of the most common presenting problems in birds is respiratory infection. Birds on presentation display a variety of symptoms, including sneezing, red watery eyes, discharge from the eyes and nostrils, and swollen sinuses. Many veterinarians may prefer to refer such patients to avian vets. However, below is set out a quick summary of the way this problem could be approached.

In chickens, respiratory infections can be divided into two groups, those caused by bacteria and similar agents and those caused by viruses. The viral diseases are Infectious Laryngotracheitis, Infectious Bronchitis, Newcastle Disease and Avian Influenza. These all have high morbidity and/or mortality rates. The diseases in the other group are Infectious Coryza (Haemophilus Infection), Fowl Cholera (Pasteurella Infection) and Chronic Respiratory Disease or CRD (which is due to a combination of Chlamydia, Mycoplasma and E. coli). By far, the most common is CRD and in fact this probably accounts for more than 80% of all pet chickens presented with respiratory signs. So how is this disease managed? Remember (as with many bird diseases) that there is a stress component so that, for control, not all of the answer will be the use of medication. CRD can be managed with a 3-point plan:

Revise housing, management and nutrition with the owner to identify any faults here.
Perform a crop flush and faecal smear to check for concurrent disease, in particular parasitism. Flagellate infections in the throat are common, as are worm and coccidial infections. These will need to be treated if a good response to antibiotic treatment is hoped for. Flagellate infections can be treated using Flagyl (metronidazole) 200 mg, ¼ tablet / 2 kg once daily for individual birds, or Turbosole (ronidazole), 1 teaspoon / 2 litres of water if large numbers of birds require medication making individual treatment impracticable. For Coccidia, use Baycox (toltrazuril), 3 ml to 1 litre for 48 hours, or 0.2 ml / kg once daily for 2 days to individual birds. To treat Ascarids and Capillaria worms, Moxidectin 2 mg / ml, 5 ml to 1 litre for 24 hours, or 0.5 ml / kg once works well.

Treat with doxycycline. Do not use other tetracyclines as they maintain too short blood levels (eg oxytetracycline and chlortetracycline, about 4 hours) for effective treatment and their absorption is significantly interfered with by a variety of mineral salts and other substances that are routinely ingested by free-range pet birds. Doxycycline maintains circulating blood levels for approximately 20 hours after medication and its action is affected to a lesser extent by mineral salts. Doxycycline is available as Vibravet tablets 50 mg, 1 tablet / 2 kg daily to treat individual birds, or, to treat larger numbers of birds, as a water-soluble powder, Doxyvet (doxycycline 12%), 1 teaspoon / 2 litres mixed fresh daily. Continue until all birds are well.

Pigeons and parrots
As with chickens, more than 80% of respiratory infections are associated with either Chlamydia or Mycoplasma. Most birds carry these organisms in their system all the time and are passively infected by their parents in the nest. In otherwise well birds, these organisms rarely cause disease but rather the ongoing low level of exposure to the organism enables the development of a strong natural immunity that is sufficiently high to provide protection from disease in most birds by 6 months of age and in almost all birds by 12 months of age. As with chickens, to ensure a good response to treatment, it is important that any flaws in environment or management are identified and corrected and that any concurrent disease is treated. The antibiotic of choice once again is doxycycline.

Birds are treated until they are well, with treatment courses of 5 - 20 days being common. In theory, if birds are treated for 45 days with doxycycline, it is possible to clear Chlamydia from their systems. However, it is probably not in the birds’ interest to consider these long treatment courses. Birds need ongoing low-grade exposure to the organism to maintain immunity. If the Chlamydia was cleared, the bird’s level of immunity would quickly wane, leaving it vulnerable to disease if it ever re-encountered Chlamydia. Given the ubiquitous nature of the organism, if it ever came in contact with another bird or bird dropping, then this is likely. Sometimes birds are pulse treated. Here birds are given shorter follow-up courses of medication (often 3 - 4 days every 2 - 3 weeks) after their initial longer course of medication. This protocol keeps the organism under control while the birds establish their natural immunity. Often after several treatments medication can be withdrawn with the birds remaining well. Small numbers or individual birds may be treated with oral doxycycline tablets, eg Vibravet. In some pet birds, repeated handling for medication causes significant stress and the risk of injury and here water-based medication is an efficient easy owner-friendly way of providing treatment. Where larger numbers of birds are involved, water-soluble medication is the only practicable treatment. In these instances, a water-soluble powder such as Doxyvet may be used.