NAVLE Infectious

Avian Psittacosis, Ornithosis, and Chlamydiosis Study Guide

Psittacosis, ornithosis, and chlamydiosis are all names for avian chlamydial infection caused by Chlamydia psittaci. This obligate intracellular bacterium represents a significant zoonotic disease and is a critical topic for the NAVLE examination.

Overview and Clinical Importance

Psittacosis, ornithosis, and chlamydiosis are all names for avian chlamydial infection caused by Chlamydia psittaci. This obligate intracellular bacterium represents a significant zoonotic disease and is a critical topic for the NAVLE examination. The disease affects over 460 bird species from 30 orders and is particularly important in psittacine birds, poultry, and pet birds.

The terminology varies by host species: psittacosis affects parrot-type birds (psittacines), ornithosis affects non-psittacine birds, and avian chlamydiosis is the general term for all chlamydial infections in birds.

Form Characteristics
Elementary Body (EB) Extracellular infectious form; metabolically inactive; environmentally resistant; 0.2-0.4 micrometers
Reticulate Body (RB) Intracellular replicative form; metabolically active; non-infectious; 0.6-1.5 micrometers

Etiology and Pathophysiology

Causative Agent

Chlamydia psittaci is an obligate intracellular, gram-negative bacterium belonging to the family Chlamydiaceae. The organism exhibits a unique biphasic developmental cycle consisting of two distinct forms:

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