Rickettsial Infections: Typhus and Spotted Fever

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Questions and Answers

How do Rickettsiae differ from viruses in terms of their genetic material?

Rickettsiae contain both RNA and DNA, while viruses contain either RNA or DNA but not both. (correct)
Rickettsiae contain only DNA, while viruses contain only RNA.
Rickettsiae contain only RNA, while viruses contain only DNA.
Viruses contain both RNA and DNA, while Rickettsiae contain either RNA or DNA but not both.

Which characteristic distinguishes Rickettsiae from viruses, allowing them to be visualized using a standard light microscope?

Their method of replication through binary fission.
Their ability to pass through bacterial filters.
Their susceptibility to antibacterial agents.
Their larger size compared to viruses. (correct)

What is the significance of outer membrane proteins (OMPs) in Rickettsial infections?

They are essential for the structural integrity of lipopolysaccharides (LPS).
They are highly immunogenic and used in vaccines against Rickettsia. (correct)
They are group-specific antigens used in the Weil-Felix reaction.
They are weakly immunogenic and rarely used in vaccine development.

How does transmission of epidemic typhus primarily occur?

Through rubbing or scratching skin where lice have defecated or crushed lice. (C) Signup and view all the answers

Which of the following is a typical symptom of epidemic typhus?

Rashes that begin on the upper trunk and generalize to the face and soles. (A) Signup and view all the answers

What conditions increase the risk of epidemic typhus outbreaks?

Refugee camps and prisons where hygiene is poor. (D) Signup and view all the answers

What is Brill-Zinsser disease, and what causes it?

A reactivation of epidemic typhus (Rickettsia prowazekii) due to waning immunity. (A) Signup and view all the answers

How does the mode of transmission for endemic typhus differ from that of epidemic typhus?

Endemic typhus is more commonly transmitted through inhalation, whereas epidemic typhus occurs through scratching louse feces into the skin. (C) Signup and view all the answers

What role do rats play in the transmission cycle of endemic typhus?

They act as reservoirs, harboring Rickettsia typhi, which is then transmitted to humans by fleas. (C) Signup and view all the answers

What is a characteristic symptom of Rocky Mountain Spotted Fever (RMSF) that differentiates it from other Rickettsial diseases?

Rashes characteristically appear on the wrists and ankles. (D) Signup and view all the answers

In which regions is Rocky Mountain Spotted Fever (RMSF) commonly found?

In the USA, Central, and South America. (D) Signup and view all the answers

What is a key identifying mark of Rickettsialpox?

An eschar (black, painless crust) surrounded by lesions. (C) Signup and view all the answers

What does a positive OX19 result in the Weil-Felix test suggest?

Rocky Mountain Spotted Fever (RMSF) or Indian Tick Typhus (D) Signup and view all the answers

Why might a false negative result occur in the Weil-Felix test?

Due to the presence of excess antibodies preventing reaction. (B) Signup and view all the answers

What is the vector for Scrub typhus?

Leptotrombidium mites (B) Signup and view all the answers

What clinical triad is characteristic of Scrub typhus?

Eschar, lymphadenopathy, and maculopapular rash. (D) Signup and view all the answers

What is the 'Tsutsugamushi Triangle,' and what does it define?

The global distribution of Scrub typhus, marking Australia, Russia, and Pakistan as infection points. (C) Signup and view all the answers

Q fever is often associated with exposure to which animals?

Cattle, sheep, and goats. (B) Signup and view all the answers

What is the typical treatment for chronic Q fever?

Hydroxychloroquine (B) Signup and view all the answers

Flashcards

Rickettsiae

Non-motile, Gram-negative bacteria that require cell lines or egg inoculation for growth.

Rickettsiae vs. Viruses

Rickettsiae are generally larger , contain both RNA and DNA, multiply through binary fission, are susceptible to antibacterial agents and are visible under a light microscope