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Micro Winter Exam 2 > L14: Rickettsial Infections > Flashcards

L14: Rickettsial Infections Flashcards

1
Q

What are the basic characteristics of Rickettsial infections?

A

Rickettsial infections are caused by obligate intracellular bacteria that typically infect endothelial cells.

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2
Q

Name three genera of bacteria associated with Rickettsial infections.

A

Rickettsia, Ehrlichia, Anaplasma

These genera include species responsible for various zoonotic diseases.

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3
Q

What types of organisms serve as reservoirs for Rickettsial bacteria?

A

Mammals, arthropods

Blood-feeding arthropods often serve as both hosts and vectors for these infections.

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4
Q

How do Rickettsial bacteria typically enter host cells?

A

Induce phagocytosis

This allows them to escape the phagosome and grow within the cytoplasm or nucleus.

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5
Q

True or False: Humans are typically the primary hosts for Rickettsial bacteria.

A

False

Humans are usually accidental hosts for these bacteria.

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6
Q

What are some common arthropod vectors for Rickettsial infections?

A

American dog tick, house mouse mite, human body louse, cat flea

Different Rickettsial species may have different vector associations.

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7
Q

What is the major pathophysiological effect of Rickettsial infections?

A

Increased microvascular permeability

This leads to various complications like edema and multi-organ dysfunction.

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8
Q

List some clinical manifestations of Rickettsial diseases.

A

Fever, severe headache, rash, myalgia, nausea, vomiting

Rash typically appears 2-5 days after the onset of fever.

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9
Q

Fill in the blank: Rickettsialpox is caused by _______.

A

R. akari

Rickettsialpox is characterized by a mild, biphasic disease.

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10
Q

What is the incubation period for Rocky Mountain spotted fever (RMSF)?

A

3–12 days

Early treatment is crucial to reduce severity and mortality.

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11
Q

What are the mammalian reservoirs for R. rickettsii?

A

Wild rodents and other small mammals

These reservoirs play a key role in the transmission of RMSF.

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12
Q

What is the mortality rate for RMSF without treatment?

A

20–80%

With treatment, the mortality rate drops significantly.

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13
Q

What is a key diagnostic feature of Rickettsialpox?

A

Red papule at bite site that becomes vesicular

This leads to eschar formation as the microbe spreads.

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14
Q

What are the consequences of Rickettsial vasculitis?

A

Rash, encephalitis, nephritis, myocarditis

These complications arise from damage to endothelial cells.

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15
Q

What is the main vector for epidemic typhus?

A

Human body louse

Epidemic typhus outbreaks often occur in crowded conditions.

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16
Q

True or False: Rickettsial infections are only found in rural areas.

A

False

Infections can occur in urban areas as well, particularly with R. akari.

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17
Q

What is the primary method of prevention for Rickettsial diseases?

A

Control of arthropod vectors

Reducing exposure to ticks and lice is essential in prevention strategies.

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18
Q

What areas are most affected by outbreaks of epidemic typhus?

A

Areas of crowding and poor hygiene (e.g., refugee camps, prisons)

Epidemics often occur in environments where sanitation is compromised.

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19
Q

What is the primary mammalian reservoir for R. prowazekii?

A

Humans

Humans are the main hosts for the bacteria responsible for epidemic typhus.

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20
Q

What is the typical mode of transmission for R. prowazekii?

A

Infectious louse feces are scratched/rubbed into injured skin (e.g., louse bites)

This highlights the importance of lice in the spread of the disease.

21
Q

What is the incubation period for epidemic typhus?

A

10–14 days

22
Q

List the common signs and symptoms of epidemic typhus.

A
  • Sudden onset of fever
  • Severe headache
  • Tachypnea
  • Myalgia
  • Other signs/symptoms may occur
23
Q

What is the mortality rate of epidemic typhus without treatment?

A

10–60%

The mortality rate significantly decreases with appropriate treatment.

24
Q

What is Brill-Zinsser disease?

A

Recurrent form of typhus that can develop decades after initial infection; symptoms less severe and rarely fatal

25
Q

What is the main mammalian reservoir for murine (endemic or flea-borne) typhus?

A
  • Rats
  • Mice
  • Cats
  • Opossums
26
Q

What is the primary vector for murine typhus?

A

Fleas

27
Q

What is the incubation period for murine typhus?

A

7–16 days

28
Q

What are the common signs and symptoms of murine typhus?

A
  • Fever
  • Headache
  • Myalgia
  • Rash occurs in ~50% of cases
29
Q

What is the mortality rate of murine typhus?

A

<1%

30
Q

What is the first-line treatment for rickettsioses?

A

Doxycycline

31
Q

What are the properties of the Anaplasmataceae family?

A
  • Gram-negative
  • Pleomorphic coccobacilli
  • Peptidoglycan reduced/absent
  • Infect cells of hematopoietic origin
32
Q

Which tick species are involved in the transmission of Anaplasmataceae?

A
  • Lone star tick
  • Blacklegged tick
33
Q

What is the main mammalian reservoir for Ehrlichia chaffeensis?

A

White-tailed deer

34
Q

What are the signs and symptoms of human monocytic ehrlichiosis (HME)?

A
  • Fever
  • Headache
  • Myalgia
  • Rash observed in ~30% of adults and ~70% of children
35
Q

What is the mortality rate for human monocytic ehrlichiosis (HME)?

A

~1–2.5%

36
Q

What is the incubation period for human granulocytic anaplasmosis (HGA)?

A

5–14 days

37
Q

What are the common complications of human granulocytic anaplasmosis (HGA)?

A
  • Acute respiratory distress syndrome
  • Renal failure
  • Toxic shock-like syndrome
  • Myocarditis
38
Q

What is the confirmatory diagnosis method for ehrlichioses and anaplasmosis?

A
  • PCR of whole blood during 1st week of illness
  • Serology (detectable titers after 1st week of infection)

These methods help confirm the presence of the pathogens.

39
Q

What should be avoided to prevent rickettsioses?

A

Avoidance of arthropod vectors

40
Q

True or False: Vaccine for epidemic typhus is still produced and available in the USA.

A

False

41
Q

What is the time frame for serology detection in ehrlichioses and anaplasmosis?

A

Detectable titers after 1st week of infection

The IFA test is used for serological testing.

42
Q

What is the drug of choice (DOC) for treating ehrlichioses and anaplasmosis?

A

Doxycycline

Rifampin is used if doxycycline is contraindicated.

43
Q

Should treatment for ehrlichioses and anaplasmosis be delayed for lab results?

A

No, treatment should not be delayed

Do not wait for lab results or if initial results (e.g., PCR) are negative.

44
Q

What are the key prevention strategies for ehrlichioses and anaplasmosis?

A

Avoidance of ticks, prompt removal of attached ticks, control of reservoirs/vectors

There are no vaccines available.

45
Q

What symptoms did the 26-year-old Pennsylvania man experience?

A

High fever (104 °F), severe headache, muscle and joint pain, chills, sweats, photophobia

The man did not seek medical attention and recovered after 2 weeks.

46
Q

Where did the 26-year-old Pennsylvania man live during his illness?

A

He lived in a cabin

He had seen and heard animals inside the wall next to his bunk.

47
Q

What animal did the 26-year-old Pennsylvania man encounter in his cabin?

A

Southern flying squirrel

He handled its nesting material and was infested by fleas before his illness.

48
Q

True or False: Vaccines are available for the prevention of ehrlichioses and anaplasmosis.

A

False

No vaccines are currently available.

49
Q

Fill in the blank: The treatment for ehrlichioses and anaplasmosis should not be delayed and should not wait for _______.

A

lab results

Micro Winter Exam 2 (12 decks)

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