The question of whether koalas can transmit chlamydia to humans is a common concern, given the widespread nature of the disease among their wild populations. While chlamydia poses a significant health challenge for koalas, the risk of transmission to humans is very low. Understanding the specifics of this bacterial infection in koalas and its distinction from human chlamydia can help clarify the situation.
Chlamydia’s Impact on Koalas
Chlamydia is a widespread and serious bacterial infection affecting koalas across Australia. The primary culprits are Chlamydia pecorum and, to a lesser extent, Chlamydia pneumoniae, with C. pecorum being the more prevalent strain. In some koala populations, the infection rate can be as high as 100%, leading to severe health consequences.
The disease manifests in several painful ways for koalas. Infected individuals often develop severe conjunctivitis, an inflammation of the eyes that can lead to permanent blindness, making it difficult for them to find food or escape threats. Urinary tract infections are also common, causing bladder inflammation and incontinence, a condition colloquially known as “wet bottom.”
Chlamydia can also infect the reproductive tracts of both male and female koalas, frequently resulting in infertility. This reproductive impact, combined with other symptoms, makes chlamydiosis a major conservation concern, contributing significantly to the decline of koala populations. The infection spreads among koalas primarily through sexual contact, but young joeys can also contract it from their mothers, either during birth or by consuming “pap,” a specialized faecal matter.
Human Transmission Risk
Despite the high prevalence of chlamydia in koalas, direct transmission of koala-specific strains to humans is very rare. Scientific evidence indicates no confirmed transmission of Chlamydia pecorum or Chlamydia pneumoniae from koalas to humans. While theoretically possible, such occurrences are isolated and unusual, typically involving direct contact with infected bodily fluids in research or care settings.
Casual contact with koalas, such as observing them in a sanctuary or wildlife park, poses negligible risk of chlamydia transmission. The strains of chlamydia affecting koalas are distinct from the bacterium that commonly causes sexually transmitted infections in humans. Therefore, the risk of contracting chlamydia from simply touching or holding a koala is considered negligible.
Distinguishing Koala and Human Chlamydia
The chlamydia strains that infect koalas are primarily Chlamydia pecorum and, less frequently, Chlamydia pneumoniae. These are different bacterial species within the Chlamydia genus compared to the one responsible for the majority of human sexually transmitted infections, Chlamydia trachomatis.
Each Chlamydia species has adapted to specific hosts and typically causes different types of diseases. While Chlamydia pneumoniae can cause respiratory infections in humans, the strains found in animals, including koalas, appear to be genetically distinct from human-adapted strains. There is no confirmed evidence that C. pecorum, the main koala pathogen, is a common cause of disease in humans.
Responsible Koala Encounters
Interacting with koalas in supervised settings can be a memorable experience. While the risk of disease transmission is low, general hygiene practices should be followed.
If touching is permitted during a supervised koala encounter, wash hands thoroughly both before and after contact. Avoid touching wild koalas, as they are not accustomed to human interaction and may react defensively. Avoiding any contact with visibly sick or injured koalas, or their bodily fluids, is a sensible precaution.