|
Clinical
presentation of Yersinia pestis infection in humans, cats
and dogs |
Three major forms of disease occur in both cats and humans.
Bubonic plague:
- Following a 2-8 day incubation period, patients develop high
fever (105 F+), anorexia, lethargy, headache, malaise, and warm,
swollen, extremely painful lymph nodes ("buboes") that
undergo hemorrhagic necrosis.
- 75% of cases in cats involve the submandibular LNs, consistent
with ingestion as a route of entry.
- In humans, buboes occur most commonly in the groin.
- Meningitis can occur as a sequela in humans.
Septicemic plague:
- This occurs when the organism spreads hematogenously to virtually
every organ in the body. Yersinia pestis can survive and
replicate within mononuclear leukocytes. The bacteria replicating
in these cells acquire capsules that inhibit phagocytosis and
killing by PMNs. (In addition, recent studies [Orth et al.,
2000] suggest that Y. pestis organisms release a cysteine
protease-like compound [YopJ] into macrophages that blocks signal
transduction and the ability of the macrophage to synthesize
tumor necrosis factor. As such, macrophages are unable to recruit
help from B and T cells to eliminate the organisms.)
- Pre-existing buboes may or may not be present in cases of
septicemic plague.
- Shock, DIC and death can occur within 2 days of systemic
spread.
Pneumonic plague:
- Infection in the lungs may follow inhalation of the organism
or systemic spread.
- This is considered the most fatal form of plague. It is
100% fatal in people if left untreated. This is the route of
concern for the use of Y. pestis as a bioterrorist agent
(CDC List A).
- A retrospective review of 119 clinical cases of plague in
cats revealed that 53% of the cases presented as bubonic, 37%
were septicemic and 10% were pneumonic. The overall case fatality
rate in cats was 33%.
In dogs, Y. pestis infection is generally much less
severe, often being subclinical or causing only mild fever and
lymphadenopathy (and possibly cough).
