Chlamydiosis, Psittacosisof poultry

Introduction

An infection of turkeys, ducks, psittacines, pigeons, man, rarely chickens, caused by Chlamydia psittaci, a bacterium of highly variable pathogenicity. It is a 'Scheduled Disease' rarely diagnosed in UK, but occurring probably worldwide. Morbidity is 50-80%, mortality 5-40%.

It is transmitted by contact, faecal dust and wild bird carriers, especially pigeons and robins. Egg transmission does not occur.

Elementary bodies are highly resistant and can survive in dried faeces for many months.

Iodophores and formaldehyde are effective disinfecting agents, phenolics are less so. Intercurrent salmonellosis and, perhaps, other infections may be predisposing factors.

Signs

• Respiratory signs.
• Greenish-yellow diarrhoea.
• Depression.
• Weakness.
• Inappetance.
• Weight loss.
• Nasal discharge.
• Conjunctivitis.
• Occasional transient ataxia in pigeons.
• Production drops in naive laying flocks

Post-mortem lesions

• Vascular congestion.
• Wasting.
• Fibrinous pericarditis.
• Airsacculitis.
• Perihepatitis.
• Spleen enlarged and congested, may rupture in pigeons.
• Necrotic foci in liver.
• Fibrinous pneumonia.
• Congested lungs and air sacs in the turkey.

Diagnosis

History, signs, lesions. Intracytoplasmic inclusions are helpful but confirmation requires demonstration of causal organisms (Giemsa stain, IFA).

Serology: complement fixation, Elisa and gel diffusion.

Differentiate from Duck viral hepatitis, Duck septicaemia.

Treatment

Tetracycline (200-800 ppm in feed for 3-4 weeks) and/or quinolone medication and supervised slaughter.

Prevention

Biosecurity, exclusion of wild birds.

Live and inactivated vaccines are protective although the former result in carriers and the latter require several applications.