Module 5 - Parasitology Flashcards
Parasitism
Symbiotic relationship in which one animal, the host, is to some degree injured through the activites of the other animal, the parasite
Obligate parasites
parasites that cannot survive outside of the host
Faculative parasites
parasites that may exist in a free-living state or within a host
Populations predisposed to getting parasites
- individuals in underdeveloped areas and countries
- Refugees
- Immigrants who are immunocompromised
- Individuals living in close quarters
- Children who attend day care centers
Modes of transmission of parasites
- Ingestion of contaminated food or drink (primarily water)
- Hand to mouth transfer
- Entry via drilling through the skin
- unprotected sexual relations
- Transplacental
- Eye contact with infected swimming water
Classification of Human parasites
Endoparasites and Ectoparasites
Protozoans
type of endoparasites
amebae, flagellates, ciliates, sporozoa, coccidia, and microsporidians
Helminths
Type of endoparasites
Platyhelminthes and Nematoda
Platyhelminthes
type of endoparasite and helminth
cestodes, and trematodes
(flatworms)
Nematoda
Type of endoparasite and helminth
roundworms
Arthropod
type of ectoparasite
insects, spiders, mites, ticks
Roundworm
(Heliminth-Nematoda)
- free-living
- mouth = 3 lips or buccal capsule and cutting plates
- sexes - larger female
- interintestinal and extraintestinal (tissue/blood)
Tapeworm
(Cestode - Platyheminthes - Helminths)
- scolex with suckers for attachment
- proglottids for body segments
- Hermaphroditic
- intermediate host needed for larval stage
Scolex
Anatomy used for attachment
- found at anterior end
- can have suckers or hooks
Proglottids
segments of the body
Definitive Host
harbors the adult or sexual stage of the parasite or the sexual phase of the life cycle
Intermediate Host
habors the larval or asexual stage of the parasite or the asexual phase of the life cycle
Accidental host
can serve as a host but is not a usual host in that parasite’s life cycle
Fluke
(trematode - Platyheminthes - Helminths)
- Leaf-shaped or elongated, slender bodies
- Possess hook or suckers for attachment
- Found in the intestinal tract, liver, blood vessels, and lungs
- Most are hermaphroditic
- Complex life cycles that require one or two intermediate hosts
Amebae
(protozoan)
trophozoite and cyst stages
- When cysts are swallowed and pass to the lower intestine, they excyst and begin to multiply as feeding trophozoites
Trophozoite
The motile feeding stage that reproduces by binary fission
- causes symptoms
Cyst
An infective, environmentally resistant stage
- similar to spores
Specimens for parasite ID
Stool, blood, tissue and other body fluids (CSF, skin snips, liver biopsy, sputum)
Laboratory Methods for diagnosing parasitic disease
Macroscopic (gross exam), Microscopic (direct wet mounts, concentrated, permanently stained), cellophane tape, Immunoassays, direct flurescent antibody
Direct smear
type of diagnostic technique for helminths
Trichrome stain
type of diagnostic technique for protozoans
Modified Kinyoun acid-fast stain
type of diagnostic technique for cryptosporidium
How does intermittent shedding impact Laboratory tests
Shedding in waves means that if specimen is collected only once from a person a possiblity is left for the parasite to get missed (not shedding at the moment)
- mutiple stools should be collected over the course of 10 days
why must liquid stools be examined within 30 minutes of passage?
Motile trophs do not last long outside of a host
- bodies can breakdown and cause a false negative result
Difficulties involved with using antiparasitic Agents
- eukaryotic organisms
- chronic infection
- complex life cycles/ differential stages
- developing countries - high immunocompromised pop, high poverty, poor sanitation
Targets for antiparasitic agents
- energy metabolism
- cell wall synthesis
- protein synthesis
- membrane function
- Nucleic acid synthesis
- cofactor synthesis
Compare antihelminth agents to antiprotozoan
Antihelminth agents target nonproliferating adult organisms, whereas the antiprotozoan agents target younger, more rapidly proliferating cells
Praziquantel - mechanism of action
serves as a calcium antagonist and causes tetanic muscular contractions; drug causes disruption of the parasitic surface and tegument, allowing antibodies to attack parasitic antigens not normally exposed on the surface (synergistic with host immune system)
Treatment options other than drugs for parasites
Change in diet, Vitamin supplements, Fluid replacement, Blood transfusion, Bed rest
