Chlamydial Zoonoses

Chlamydial zoonoses refer to infectious diseases caused by chlamydial species that can be transmitted from animals to humans. One of the most notable zoonotic chlamydial pathogens is Chlamydia psittaci, which is responsible for psittacosis, also known as ornithosis or parrot fever. This disease is primarily associated with exposure to infected birds.

Chlamydial infections in animals, such as those caused by Chlamydia abortus and Chlamydia pneumoniae, are known to cross host barriers, leading to zoonotic diseases in humans. These infections can lead to various health issues, including respiratory diseases, conjunctivitis, and reproductive losses in animals, which in turn have implications for human health when transmitted across species.

Psittacosis / Ornithosis​

• Psittacosis is derived from the Greek word psittacus, which means parrot. Te disease is associated with parrots. Ornithosis means it is associated with birds.
• The disease is simply referred to as psittacosis in humans regardless of the source. People get it by direct contact with sick birds.
• The causative organism is Chlamydia psittaci.

Manifestation of ornithosis/ psittacosis in birds​

The responsible chlamydia is a common flora in birds hence there only needs to be a change in the physiological conditions of the bird for the organism to attack.

Stressed birds will develop the disease. Stress can arise from different sources including transportation or noise. Affected birds will exhibit the following symptoms:

• Diarrhoea
• Dullness
• Hurdling together
• Ruffled feathers

During the active stage of the disease, the microorganism is highly concentrated in the faeces, which becomes the major source of contamination.

Manifestation of ornithosis/ psittacosis in humans​

• People get the disease through contact with sick birds during the active stage of the disease.
• Human to human transmission occurs, though not very common. The chlamydia can be air-borne.

Symptoms of ornithosis in humans​

Incubation usually takes between 1 – 2 weeks after exposure. The symptoms then commence as a typical pneumonia. Observable symptoms include:

1. High fever
2. Dry cough
3. Chest pains
4. Dyspnoea
5. Severe headaches
6. Hepatitis due to the effect on the liver
7. When the chlamydia travels to the brain, it causes mental confusion that progresses into a coma
8. Myocarditis (inflammation of the heart) leading to heart failure

Diagnosis of ornithosis​

• Conduct routine checks in animals. Isolate sick birds for confirmation.
• In humans, perform lab tests at the hospital.

Treatment of ornithosis​

• In birds, do prophylactic treatment (give them oxytetracycline)
• People should get prescription form the hospital. Usually, oxytetracycline is given.

Control measures for ornithosis​

1. In birds, conduct regular testing and treatment.
2. Avoid predisposing factors (e.g. stressing the birds) as much as possible. Do prophylaxis before exposing the birds to stressful situations.
3. Avoid faecal contamination of birds’ feed and water.
4. In humans, ensure careful handling of birds whether they are sick or just normal.