Parasitology Flashcards
Parasite kingdoms
Protozoa- unicellular
Metazoa- multicellular
Local transmission
When a traveler picks up an infection in an endemic area, and then returns to a non-endemic area, but is still able to spread the infection because the vector responsible is there.
What defines the geographic range of a parasite?
The presence/absence of a vector.
Protozoa
Microscopic, unicellular
Free living or parasitic
Multiply in humans
Helminths
Worms
Large, multicellular
Almost all are parasitic
Intermediate host
Where parasite develops
Only multiplies asexually here
Definitive host
Matures the parasite
Multiples sexually
Normally humans
Intermediate host of Paragoniumus westermani
snails and crustaceans
Intermediate host of Fasciola spp.
snails and plants
Intermediate host of Tania solium
pigs
Intermediate host of Trypanosoma cruzi
Triatomine bug
Prepotent period
Where the parasite has infected a host but is undergoing developmental changes and has not yet caused any damage for sxs to be observed
Pathogenic mechanisms of parasitic infections
1- Toxic products
2- Mechanical tissue damage
3- Immunopathology- HS rxns, AI rxns, metaplastic changes
Severity linked to repeated exposures
Stain used for Babesia spp.
Giemsa stain
Nocturnal periodicity
Periodic migration of microfilariae between peripheral blood and lung capillaries
Influences sampling time
Ultrasound useful for detecting:
Echinococcosis
Cysticercosis
Onchocerciasis
Lymphatic filariasis
Gives information about:
Abscess/cyst/space-occupying lesion
#, size and location
4 major groups of protozoa
1- Sarcodina (amoeba)
2- Mastigophora (flagellates)
3- Ciliophora (ciliates)
4- Sporozoa (non-motile adult stage)
Examples of relevant GI Sporozoa
Cryptoisospora belli
Cyclospora cayetanium
Both are apicomplexa (coccidian protozoa)
Examples of GI Mastigophora
Giardia intestinalis
Examples of GI Sarcodina
Entamoeba histolytica
Example of GI Ciliophora
Balantidium coli
It’s the ONLY human pathogenic ciliate.
Example of sporozoa
Plasmodium
Physiology and Repro of protozoa
get nutrients from pino- or phagocytosis
Respiration: facultative anaerobic
Survival form: cyst. If not cyst then must have person-person transmission or a vector.
Reproduction: binary fission
Some exceptions (plasmodium)Trohphozoite
Motile feeding stage
Normally found in the tissues
Larger than cyst.
Cyst
Non-motile, resistant
Multinucleated, smaller
T. vaginalis has NO cyst form
Metazoa
Have life functions in tissue and organ systems (unlike protozoa which are in a cell)
Nemathelminthes (roundworms)
Platyhelminthes (flatworms)
Ascariasis
Mostly asx
Lungs (larvae): asthma or pneumonia-like cough, SOB and wheezing
Intestines (adult worms): diarrhea or bloody stools. N/V abd. pain.
Severe infections: malnutrition and wt. loss
Most common cause of DALYs
Soil-transmitted helminths. Hookworms are #1 of those
Lymphatic filariasis
Cause hydrocele in men
Lymphedema in women
Common in Africa, Asia, Americas, Pacific. Most are in SEA
Physiology and Repro of Metazoa
Nutrients from active ingestion of tissue and fluid from hot, or passive absorption.
No multiplication/replication of adult form in humans. Produce large # of eggs per day
Infective forms of nematodes
Egg
Filariform larvae
3rd stage larvae
Infective forms of Trematodes
Cercaria
Metacercaria
Infective forms of cestodes
Cysticercus
Proglottid
Embryonate egg
Cystericeroid
Polyparasitism/Co-infection
Infection of multiple parasites at one time. Increases morbidity of other infectious diseases (TB and HIV)
Roundworms
aka Nematodes
Most common transmission: ingestion of eggs or larvae
Adult stages in GIT, blood, lymph or subcut tissues.
Adults or larvae can cause disease
Flatworms
aka platyhelminths
Includes Trematodes and cestodes
Trematodes
aka flukes Flattened 2 anterior suckers Hermaphroditic Diagenetic- sex and asex development
Life cycle of trematode
Eggs are excreted into feces Hatch in water--> form miracidia Enter intermediate host Develop sporocysts Enter definitive host Hatch into cercariae
Miracidia
ciliated, first-stage larva of a trematode, emerges from the egg
Penetrates the intermediate host
Cercariae
free-swimming trematode
In definitive host
Cestodes
aka tapeworms
Flattened, but not flukes.
More mature and developed the further away from the head.
The mature parts contain the eggs that are released into the environment and cause infection.
No digestive system. Absorb nutrients across their surface
Life cycle of cestodes
aka tapeworms
Adult form found in intestine of mammalian carnivores (definitive host).
Some spp. have same intermediate and definitive host.
Eggs are ingested–> develop into larvae –> enter circulation and encyst –> intermed. host consumed by definitive –> encysted form released into intestine, develops into adult.
Control strategies for trypanosomiasis
Insecticide treated nets
