Human Parasites Flashcards
Define: Parasite.
An organism which lives upon or within another living organism at whose expense it obtains some advantage.
What organisms are studied in the field of parasitology?
- Protozoa (unicellular eukaryotes)
- Metazoa (multicellular eukaryotes)
- Helminths (worms)
- Arthropods (insects)
Define: Complex life cycles.
Parasites that develope in one or more additional host species.
Define: Definitive host.
A species in which the parasite undergoes sexual replication
Define: Intermediate host.
A species in which the asexual replication occurs.
Name three types of helminths.
- Roundworms/Nematodes
- Flatworms/Trematodes/Flukes
- Tapeworms/Cestodes
Name five types of protozoan parasites.
- Amebas
- Flagellates
- Ciliates
- Sporozoa
- Microsporidia
What three species of Schistosomiasis are widely distributed?
- Schistosoma mansoni (Primarily in Africa, South America and the MIddle East)
- S. japonicum (Primarily in China, the Philippines and Indonesia)
- S. haematobium (primarily in Africa and the Middle East)
What two species have more restricted geographic distributions?
- Schistoma intercalatum (West Africa)
2. Schistoma mekongi (Southeast Asia)
What do miracidia infect?
Snails. After they hatch in water.
What do miracidia develop into once they have infected snails?
Sporocysts
What is released from snails and are considered free-swimming?
Cercariae
What are able to penetrate the skin of humans?
Cercariae
What happens to Cercariae when they enter humans?
They loose their tails and become schistosomulae.
Where do schistosomulae mature?
Portal blood of human host then they migrate to the mesenteric veins or venous plexus of the bladder.
In which location do mature schistosomulae do it (reproduce)?
The mesenteric veins or venous plexus of the bladder.
What are the symptoms of a schistosomiasis infection?
- Swimmers itch (2-3 days after infection)
- Katayama Fever (4-6 weeks after skin invasion)[ACUTE]
- Lymphadenopathy and hepatosplnomegaly [ACUTE]
- Chronic- granulamatous and fibrotic changes in the liver or in the bladder
What are the symptoms of light infections?
Asymptomatic
What are the symptoms of heavy infections?
Diarrhea, abdominal pain, or ascites
What do molluscicides treat?
Schistosomulae infections.
What are the four species of protozoa in the genus Plasmodium that cause malaria in humans?
- P. vivax
- P. ovale
- P. malariae
- P. falciparum
Which species of plasmodium causes the most deaths?
P. falciparum
Where is P. vivax distributed?
Distributed from tropical to temperate zones
Where is P. falciparum distributed?
tropics and subtropics
Does the asexual or sexual phase take place in humans?
Asexual
How does malaria infect humans?
Infected mosquitos bite humans exposes sporozoites to humans
What organ do sporozoites infect?
The liver
After primary replication in the liver what is released into the blood?
Merozoites
Once in the erythrocytes what do merozoites do?
Asexual replication
Which erythrocytes are vulnerable to P. falciparum?
Erythrocytes of all ages
Which erythrocytes are vulnerable to P. ovale and P. vivax?
Young erythrocytes
Which erythrocytes are vulnerable to P. malariae?
Old erythrocytes.
What two processes lead to anemia in malaria?
Lysis of RBC and phagocytosis by the stimulated reticuloendothelial system
What are some of the symptoms of malaria?
jaundice, hypotension, and tachycardia with fever and hepatosplenomegaly. Severe cases cause cerbral malaria and multi-organ failure. Immune complex can cause glomerulonephritis.
What three diseases protect against malaria?
- Sickle cell anemia
- Thalassemias
- Glucose-6-phosphate dehydrogenase deficiency
