Protozoan and Helminth Parasites Flashcards
An intermediate host can be defined as which of the following?
-Where the parasite reaches sexual maturity
-A host that is required for parasite development but where no sexual development takes place
-A host that can be infected but does not play a role in the lifecycle -No development takes place, but the parasite remains alive and infective to another host
- Host thats required for parasite development but no sexual development takes place
An intermediate host can be defined as a host that is required for parasite development but where no sexual development takes place.
A definitive host can be defined as which of the following?
-Where the parasite reaches sexual maturity
-A host that is required for parasite development but where no sexual development takes place
-A host that can be infected but does not play a role in the lifecycle
-No development takes place, but the parasite remains alive and infective to another host
Where parasite reaches sexual maturity
Helminth parasites can be best defined as…?
-Single celled organisms that lack a nucleus
-Single celled organisms that have a nucleus
-Multicellular organisms that can range from millimetres to tens of meters in length
Helminth parasites can be best defined as multicellular organisms that can range from millimetres to tens of meters in length.
Which of the following are examples of nematode parasites?
-Ascaris lumbricoides
-Onchocerca volvulus
-Taenia solium
-Trichinella
-Trichuris trichiura
-Schistosoma
-Wuchereria bancroft
Ascaris lumbricoides
Onchocerca volvulus
Trichinella
Trichuris trichiura
Wuchereria bancrofti
Whats the difference between an obligate and facultative parasite?
Obligate have to spend part of their life in a parasitic relationship, facultative are free living but can become parasitic in the right host
Define all of the hosts: definitive, intermediate, incidental, paratenic
definitive: where parasites become sexually mature
intermediate: needed for parasite development, but no sexual maturity takes place
incidental: can be infected but doesnt have role in parasitic lifecycle
paratenic: no development takes place, but able to pass to another host
Eg Plasmodium parasites that are the causative agents of malaria, sexual reproduction occurs in the gut of the mosquito vector, so the mosquito would be considered the definitive host and the vertebrate host would be considered the intermediate host.
Why are helminth infections hard to combat? Why are they so good at evading/supressing immune system?
- very large (makes it hard to kill/dislodge)
- long lived (3-10 years)
- takes decades to develop immune memory
- can manipulate host immune system
Helminths cause long term chronic infections
Typically dont replicate in the host, lay eggs in feces or urine –> means that sanatation and hygeine can be used to combat infection bc wld reduce # of eggs
What are the three groups of helminths?
- nematodes (roundworms) - Trichuris trichiura
- cestodes (tapeworms) - Taenia solium
- trematodes (flukes) - Schistosoma mansoni
Whats an example of a protozoan parasite?
Plasmodium (Malaria)
Giardia
Toxoplasma
How are protozoan parasites transmitted in comparison to helminths?
Protozoan can be transmitted via arthopods (vector borne disease) or sexually
Helminths can be transmitted via intermediate host (ie schistosomes) or ingestion, or skin penetration
Trypanosoma cruzi (Chagas disease)- vectored by Triatomine bugs
Plasmodium (malaria)- vectored by Anopheles mosquitoes
Trypanosoma brucei (sleeping sickness) - vectored by Tseste flies
What kind of helminth is Trichuris trichuria? How does it infect hosts?
- A nematode, called the whipworm.
- Eggs spread through feces, and ingested from contaminated soil
- The head is embedded in the epithelium, and the tail is free in the lumen which makes egg secretion easier
nematodes aka roundworms
Trichuris typically embeds itself in the gut mucosa, and creates synctial epithelial tunnels
What kind of helminth is Taenia solium? How does it infect hosts?
- A cestode (tapeworm)
- uses pigs as an intermediate host, humans infected if consume raw pork
- Larvae will penetrate gut wall and encyst in muscles or CNS
What kind of helminths are Schistosoma spp? How do they infect hosts?
S. mansoni, S.haematobium and S. japonicum
- Trematodes (flukes)
- Eggs excreted through human feces, hatch, infect snails, snails release cercariae into water, humans in water get infected
- Found in intestines or venus plexus, can also be found in liver
What kind of parasite are Plasmodium spp? What are the two most prevalent types? How do they infect hosts?
Plasmodium spp causes malaria
- Apicomplexan parasites
- P. falciparum and P. vivax
