Notes
Bacterial Febrile Illnesses & Rashes
Sections
Gram-Negative Rods & Spirochetes - Febrile Illnesses & Rashes
Zoonotic illnesses, and most are transmitted via arthropod vectors.
Details and less common species can be found in separate tutorials.
Rash, Fever, & Headache
- Intracellular rods responsible for a range of illnesses.
- Primarily target the lining of small vessels.
Pathologies:
Rocky Mountain Spotted Fever
Bacteria are transmitted by hard ticks.
Infection produces a rash that begins on the hands and feet, then spreads to the trunk.
Ocular involvement, such as conjunctivitis, is common.
Without treatment, widespread vascular damage can lead to organ failure and death.
Rickettsialpox
Bacteria that cause rickettsialpox are transmitted by mites.
Infection is characterized by an eschar, which is an area of redness with a blackish scab, at the site of the mite bite, and a vesiculopapular rash. The rash somewhat resembles the rash of chicken pox, which is why this illness is called "rickettsialpox".
Infection is usually mild and self-limiting.
Epidemic typhus
Bacteria are transmitted via the human body louse.
Infection produces a pinkish macular rash that begin on the trunk and spreads to the extremities, and that the palms and soles are spared.
Notice that this rash pattern is exactly the opposite that of Rocky Mountain Spotted Fever, which begins on the hands and feet and spreads to the trunk.
Widespread vascular damage can lead to death.
Brill-Zinsser disease occurs when latent infection re-emerges; it is typically less severe than the initial infection, and rash may be absent.
Endemic typhus, aka, Murine typhus
Bacteria are transmitted by fleas that parasitize small mammals, including cats.
Infection is similar to epidemic typhus, though usually milder.
Spirochete transmitted by hard ticks.
Causes Lyme Disease in the United States.
Other species of Borrelia are responsible for Lyme Disease outside the United States.
Lyme disease is a multi-system inflammatory disease.
Early stages are often, but not always, characterized by localized erythema migrans – which often looks like a "bulls' eye".
Some patients also experience flu-like symptoms such as fever and headache.
Later, infection can produce multiple, but usually smaller, areas of erythema migrans.
Bacteria can spread to multiple organ systems, notably, the nervous system, heart, and musculoskeletal structures.
Fever, & Headache
Coxiella burnetti
Intracellular rods.
Not transmitted via arthropod vectors
Bacterial endospores are inhaled from animal hides or wastes.
Not everyone who inhales the endospores will get sick.
Q fever, which presents with mild to severe flu-like symptoms.
Pneumonia can occur in severe cases.
Hepatitis; Q fever hepatitis has a characteristic histopathology with fibrin ring granulomas that may or may not have fat vacuoles inside.
Chronic Q fever may develop later; endocarditis is a common complication.
Borrelia recurrentis and other Borrelia species
Species of Borrelia that cause relapsing fever are transmitted via body lice and soft ticks.
As its name suggests, relapsing fever is characterized by recurrent episodes of fever and septicemia, which are the result of bacterial proliferation.
Borrelia membrane proteins undergo antigenic variation, which promotes cycling between bacteremia and clearance.
We illustrate this cycle, as follows:
– In response to bacteremia, host antibodies form and begin to clear the bacteria from the blood.
– Bacteremia recedes, and the host enters the afebrile stage.
– However, the bacteria rapidly undergo antigenic variation.
– The new variants evade host antibodies and proliferate in the host.
– Thus, the host enters a new febrile episode.
Symptoms of relapsing fever can range from mild to severe, and, in large part, depends on the causative species.
In addition to fever and headache, indicate that mild cases tend to produce muscle and joint pain, abdominal tenderness, and vomiting. Patients may also have jaundice and low platelet counts.
Severe cases can affect major organ systems and hepatic or cardiac failure or cerebral hemorrhaging.