VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

PATHOGENESIS

• Chlamydial organisms may be shed in faeces of carrier animals. Chlamydial elementary bodies are shed in the semen.
• Young one gets infection mainly through milk of the dam.
• Animals and humans are infected by the inhalation of infectious dust and droplets.
• In case of enzootic abortion and enteritis in ewes, the infection may take place by ingestion.
• The severity of the disesase depends on
  • Strain and virulence of the agent
    • Ovine and bovine type 1 isolates are more frequently associated with abortion, genital infections and enteritis.
    • Type II isolates are associated with conjunctivitis, pneumonia, encephalomyelitis and polyarthritis.
  • Age, sex, physiological state and species of host.
  • Route of infection and degree of exposure to Chlamydiae
  • Environment and management practices.
• The Chlamydiae have a predilection for epithelial cells of the mucous membrane.
• After inhalation of infectious dust and droplets, pneumonia may develop.
• In enzootic abortion of ewes the organism localize in cells of the placenta, abortion will occur in the last 2-3 weeks of pregnancy and this is associated with a diffuse, necrotic placentitis.
• In BUSS disease, inflammation of vascular endothelium and nervous signs are predominant.
• In avian psittacosis, as a result of certain stress conditions, the organism multiply in the spleen and kidney of normal appearing birds and are shed in the faeces in large numbers.
• The faeces dry, producing a dust that is infectious to susceptible avian and human. In birds, respiratory, intestinal and systemic signs are seen.