Epidemiology of Infectious Diseases Flashcards
Parasitism
A type of symbiotic association between 2 species where one benefits (the parasite) ny exploiting the resources of the other (the host)
Endoparasites
Complete some or all of life cycle within host tissues or cells
What are two subtypes of endoparasites?
Microparasites (pathogens) and macroparasites
Three major taxas of microscopic endoparasites
Viruses, bacteria, and protozoa
(minor ones: fungi and prions)
Macroparasites are different from microparasites because they complete ____ of their life cycle within the host.
Part
(usually release infective stages from the host)
Ectoparaties
Live on surface of host
ex. Ticks, mites, fleas, mosquitoes, leeches, etc.
Direct transmission
Physical or close contact between hosts which allows disease agent to transfer from an infected host to an uninfected one
Indirect transmission
Transfer of a disease agent from an infected host to an uninfected one facilitated by an intermediate host or a vector
Ecological categories of infectious disease
Zoonotic
Multi-host
Human-specific
Zoonotic diseases are defined as…
Diseases transmitted from animals to humans only
ex. Lyme disease, Hanta virus
Multi-host diseases are defined as…
Diseases that transmit between both animals and humans
ex. Influenza virus
Human-specific diseases are categorized as…
Diseases transmitted from human to human
ex. Measles, HIV – but most have zoonotic/multi-host origins
Schistosomiasis, also called the ____ ____ ____ ____, is caused by aquatic trematodes that use ____ as intermediate hosts.
Plague of the Pharaohs; snails
Why was schistosomiasis prevalent in Eygpt?
The Egyptian civilization had great success with irrigation and controlled flooding of the Nile, but it also created conditions favorable for Schistosomiasis – Lots of water year-round ensured land productivity, but also led to greater possibility to parasite exposure.
The impoundment of water causes ____ ____ ____, which leads to ____ ____, and attracts ____, the intermediate host of schistosomiasis.
Accumulation of nutrients; Algal bloom; Snails
The Plague was caused by the ____ that was transmitted by ____ that were carried by ____, the anthropophilic ____ ____.
Bacteria; Fleas; Rodents; reservoir hosts
Bubonic Plague
Infests lymph system, causing lymph nodes to undergo hemorrhagic inflammation
Septicemic Plague
Causes disseminated intravascular coagulation within the bloodstream, preventing subsequent clotting as clotting factors and platelets are used up
Pneumonic Plague
Infests lungs, typically following bubonic/septicemic syndrome
*Human specific
Justinian plague (541-542 AD and a second wave in 588) killed over ____ ____, which contributed to the fall of the classical world and beginning of the ____ ____.
100 million; Dark Ages
Black Death (1347 - 1351) Killed ____ ____ (~1/4 world population) and is considered the most severe pandemic in human history
1500 million
Third Pandemic in Asia (1855 - 1900) likely had two different forms of transmission (____ and ____)
Bubonic; pneumonic
Medical advances motivated by smallpox epidemics
- Inoculation: Intentional infection with a minor strain of smallpox virus, which conferred protection against the more virulent or major strain (could still kill ppl)
- Vaccination: Used a vaccine derived from the vaccinia virus in the 19th century
Characteristics of Type I Epidemic
- Occur in large populations
- Regular peaks
- Never disappears
*Example: Flu
