by Olivia Saray and Joshua Lee
Chlamydophila psittaci is a species of bacteria that was first isolated from humans in Switzerland in 1879 and at this time named Pseudotyphus. The name Chlamydophila psittaci was adopted in 1890 by french scientist Morange, who isolated the same bacterium in parrots after deciphering it as a causative agent of psittacosis. C. psittaci caught the limelight in the early 1930’s when an epidemic broke out within domestic parrots and parakeets decreasing their popularity as household pets.
C. psittaci in addition to being a bacteria is also known as a zoonosis, causing infection primarily in animals but can also be contracted by humans; as a result inspection of exotic birds during importation is crucial to prevent future epidemics.
C. psittaci can be transmitted across species from bird to bird, bird to human, bird to reptiles, and bird to mammals. The bacterium is present in the tissues, feces, nasal and ocular discharge as well as plumage of infected birds. Contraction of the bacteria can occur through inhalation of particles from secretions of infected birds. It may also be transferred via physical contact of the bird’s beak with another animal or exposure due to injury, such as a bite from an infected bird. The most common method of transmission, however, is through the air.
C. psittaci presents less of a threat upon immediate release due to the fact that the organism remains viable while independent of a host. It exists as an elementary body outside of the host, meaning it can survive, but not infect, until it enters a new organism. Infected secretions eventually dry into a dusty substance, which contaminates the air. Inhalation of these particles could allow the bacterium to enter a potentially viable host and cause infection.
Once the bacterium presents itself in a new avian host, it will infect the mucosal epithelial cells of the bird and the macrophages of the respiratory tract. Macrophages, meaning “big eater”, are cells of the innate immune system that engulf pathogens. The bacterium will spread to infect other organs via the blood and result in localized infections such as pneumonitis, pericarditis, enteritis and sinusitis. If untreated the infection will eventually lead to septicemia and death of the bird.
Infection of a bird by C. psittaci will present observable symptoms in the host such as rough plumage, fever (resulting in puffiness of the bird’s feathers to keep warm), tremors, weight loss, yellow-green/greyish watery droppings, coughing and conjunctivitis.
Due to the adaptive nature of this bacterium, humans can also contract the disease and display symptoms following a 5 – 14 day incubation period. The severity of symptoms can vary from slight feelings of illness to systemic illness accompanied by severe pneumonia. More specific symptoms include fever, chills, headache, and myalgia. Humans usually contract this disease through inhalation of contaminated air or coming into direct contact with a bird, which is infected with the disease. Although the disease can be contracted through birds, transmission from human to human is rare. With modern medicine, deaths are limited to less than 1% of all reported cases, and are easily treated with antibiotics such as tetracycline.
Cases of psittacosis have been reported in at least 159 different avian species. The most common victim being parrots, but transmissions have also been widely documented from free-ranging birds including doves, pigeons, and shore birds, among others.
Though there have been several outbreaks of psittacosis, the highest rate among household parrots was in 1983 with an astonishing rate of 24% of birds admitted to veterinary clinics testing positive for the disease. This percentage was probably much higher seeing as it is likely that many cases go unreported. Psittacosis is most common among small to medium sized parrots, where 17.8% of cockatiels, 27.3% lovebirds and conures, and 17.24% of African Greys and Amazon Parrots tested positive for the disease in the 1983 outbreak.
Today, these numbers remain relatively