Lecture 41: Vector-Transmitted Diseases and Pathogens

Flashcards covering vector-borne and zoonotic diseases including Rabies, Malaria, Lyme disease, Typhoid Fever, and Cholera based on lecture notes.

How is a vector-borne disease transmitted to a human?

By the bite of an arthropod 'vector' such as an insect or tick.

What is the genome type of the Rabies virus?

$(-)ssRNA$ genome

Why is Rabies classified as a zoonotic disease rather than vector-borne?

It is usually transmitted to a person by the bite (saliva) of an infected animal rather than an arthropod.

How long should a pet suspected of contact with a rabid animal be quarantined?

10 days

What are the specific viral inclusions found in the cytoplasm during post-mortem diagnosis of Rabies?

Negri bodies

How many deaths are caused by Malaria (Plasmodium) globally each year?

More than 600,000 deaths, mostly children under 5 years of age.

What is the primary mosquito vector for Malaria?

Anopheles

What is the infectious agent and morphology of Lyme disease?

Borrelia burgdorferi, which is a spirochete (Gram-negative but no LSP) up to $30\,\mu m$ long with corkscrew motility.

In the Northeast US, which tick and life stage is primarily responsible for Borrelia transmission?

The blacklegged tick (Ixodes), with most cases arising from nymph bites.

What are the primary reservoirs for B. burgdorferi in the Northeast US?

White-footed field mice and other small warm-blooded animals.

What is the typical speed of Borrelia in tissue?

Approximately $4\,\mu m/s$

What antibiotics are commonly used to treat Lyme disease?

Doxycycline or amoxycillin

What is the infectious agent of Typhoid Fever?

Salmonella enterica serotype typhi

What percentage of the population in Ithaca was affected during the 1903 Typhoid outbreak?

10% of the population (1350 cases), including 29 Cornell students who died.

What unique virulence factor of S. enterica ser. typhi encodes a capsule to inhibit complement?

Salmonella pathogenicity island 7, which produces the Polysaccharide Vi-capsule antigen.

In severe cases of Cholera, how much fluid can a patient lose per day?

Up to $20\,L$

Which Vibrio cholerae strains were responsible for the 5th and 6th pandemics?

O1 classical strain

Which Vibrio cholerae strain is responsible for the ongoing 7th pandemic?

O1 El Tor strain

What is the specific AB exotoxin encoded by the ctxAB gene in Vibrio cholerae?

Cholera toxin (CT)

What lysogenic filamentous bacteriophage carries the ctxAB gene required for Vibrio cholerae to cause epidemics?

CTXφ prophage