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Modes of
transmission of Yersinia pestis |
Transmission via fleas:
- The primary reservoir for Y. pestis is rodents (230
species, but especially rats globally, and prairie dogs and squirrels
in the U.S.). Transmission among rodents and other wild animals
occurs via flea bites. Many infections in humans and domestic
animals (accidental hosts in terms of the life cycle of the organism)
are ALSO contracted through the bite of an infected flea.
- Yersinia pestis express a phospholipase enzyme that
allows the bacteria to avoid killing and survive in the midgut
of fleas. Subsequently, the blood meal in the flea's foregut
clots, providing a focus for replication of the organism, and
the ensuing blockage of the foregut causes regurgitation of the
organisms the next time the flea tries to feed.
Transmission by ingestion of an infected animals:
- Ingestion of infected rodents is a common method of transmission
to domestic cats, and can also be a route of infection for humans.
Transmission through contact with body fluids from infected
animals:
- Humans can contract Y. pestis directly through contact
with blood, pus or aerosols from infected animals.
- For this reason, veterinarians and wildlife personnel are
at risk for zoonotic transmission.
- Cats are the domestic animal of most concern for zoonotic
spread to veterinarians. Since 1977, 23 human cases of plague
(including 5 fatal cases) have been linked to direct exposure
to Y. pestis-infected cats. Six of the cases were in DVMs
or their staff.
