Intro

Question 1

describe the difference between a definitive, intermediate, and paratenic/transport host

Answer 1

definitive: host in which parasite reaches sexual maturity and sexual reproduction occurs!!

intermediate: parasite develops but does not reach sexual maturity; this host is often a required part of the life cycle and the int host is often the prey in a predator/prey relationship; arthropods are also common int hosts

paratenic/transport: simple mechanical carry of the INFECTIOUS form of the parasite, WITHOUT growth/development of the organism

Question 2

NOT an LO: describe aberrant (dead-end) hosts and reservoir hosts

Answer 2

aberrant: parasite infects and may cause disease, but further transmission does not occur

reservoir host: parasite infects host without host experiencing any negative effects, but can still transmit it to other susceptible species

Question 3

how can you tell whether a parasite is a helminth, a protozoan, or an arthropod?

Answer 3

helminths: multicellular where each cell performs a specific function

protozoa: unicellular (eukaryotic) where the single cell performs all the functions, MUCH smaller than worms with specialized structures and organelles, and complex life cycles with many different stages and often multiple hosts, frequently found INSIDE host cells

arthropods: segmented body, paired segmented appendages, bilateral symmetry, chitinous exoskeleton

Question 4

describe trematodes general structure (shape, sexes, anterior end, alimentary canal, and body cavity)

Answer 4

shape: flat, bilaterally symmetrical, leaf-like, segmented

sexes: monoecious (hermaphrodites) except for blood flukes

anterior end: 2 suckers for specialized holdfast organs, but no hooks

alimentary canal: present but incomplete (blind)

body cavity: absent

Question 5

describe nematodes (shape, sexes, anterior end, alimentary canal, and body cavity)

Answer 5

shape: elongated, cylindrical, unsegmented, tapered at the end

sexes: diecious; separate male and female!!

anterior end: no suckers or hooks

alimentary canal: present and complete

body cavity: present

Question 6

describe cestodes general structure (shape, sexes, anterior end, alimentary canal, and body cavity)

Answer 6

shape: dorsoventrally flat, bilaterally symmetric, tape-like, segmented

sexes: monoecious; basically a string of repro organs; (many proglottids form the strobila string) HERMAPHRODITES where each segment has both ovaries and testis

anterior end: suckers and hooks (scolex acts as an anchor)

alimentary canal: absent

body cavity: absent

Question 7

explain the nematode/roundworm life cycle (2)

Answer 7

1. eggs are ingested by definitive host
2. larvae develop inside DH until they reproduce and pass eggs into feces/external environment to be ingested again

Question 8

explain the cestode/tapeworm life cycle (3 facts)

Answer 8

1. all tapeworms use at least 2 hosts (usually in a predator/prey relationship)
2. the adults in the definitive host are relatively harmless and usually live in the GI tract
3. the larval stages in the intermediate host are associated with the greatest pathology, where the immature forms usually live in tissues and fuck shit up

Question 9

explain the trematode/flatworm life cycle (2 facts)

Answer 9

1. all species require AT LEAST 2 hosts, but many require 3-4
2. the first intermediate host is always a snail/slug species

classic example is liver fluke

Question 10

compare and contrast ectoparasites

Answer 10

insecta: air-breathing arthropods with 3 distinct body regions (head, thorax, abdomen), one pair of antennae, 3 pairs of legs, and 1-2 pairs of wings as an adult

arachnida: cephalothorax and abdomen are combined into one body region, no antennae, 4 pairs of legs, and no wings as adults

Question 11

compare and contrast biological versus mechanical transmission in arthropods

Answer 11

biological vector: a living obligate host in which the pathogen reproduces or develops in the arthropod before transmission; is required!!!

mechanical vector: an object (animate or inanimate) pathogen does not reproduce or develop in vector

Question 12

recognize the different effects of parasites on different hosts (e.g.,
pathologic lesions in accidental host vs definite host)

Question 13

describe a direct life cycle

Answer 13

parasite does NOT require an intermediate host; the infective stage (egg, cyst, or larva) is in the environment

Question 14

describe an indirect life cycle

Answer 14

parasite requires an intermediate host

Question 15

describe host specificity

Answer 15

this is the degree of host-parasite compatibility

high host specificity: parasite can infect only one or very few host species

low host specificity: parasite can infect several host species (is more often the parasites with indirect life cycles because multiple hosts, both intermediate and paratenic, maybe even aberrant)

Question 15

describe a facultative indirect life cycle

Answer 15

parasite MAY use a paratenic host, but that paratenic host is not necessary/required for the life cycle

Question 16

describe prepatent versus patent

Answer 16

prepatent period: developmental/maturation time needed between time of infection to the production of offspring; determines the timing of treatment for control measures and testing

patent: an infection in which sexually mature parasites are generating offspring

Question 17

compare and contrast infection versus infectious versus infective versus disease

Answer 17

all different!!

infection: presence of an agent that has the potential to cause disease

infectious: infected host capable of transmitting infection to another host (contagious in virology)

infective: the parasitic stage capable of invading the next host

disease: the occurrence of dysfunction/pathology

Question 18

what are the 4 forms of pathogenesis?

Answer 18

1. trauma: via direct destruction of host cells or tissues, indirect destruction of host cells or tissues, or organ occlusion
2. nutrient robbing
3. excretion of toxins or other pathogens
4. interactions with host immune/inflammatory responses

Question 19

describe the effect of intracellular versus extracellular parasites on inflammatory processes in the host

Answer 19

intracellular parasites tend to not try to avoid activating inflammatory responses in the host, as they are relatively protected inside the host’s cells, but extracellular parasites tend to try to avoid inflammatory responses or even decrease inflammation because they are exposed and at risk of injury due to inflammation as they are outside the cells of the host