Parasitology Flashcards
What is a parasite?
A organism that lives on or in a host organism and gets its food from or at the expense of its host
What are three main classes of parasites that can cause disease in humans?
Protozoa
Helminths
Ectoparasites
What is Protozoa?
Microscopic single-celled organisms that can be free living or parasitic in nature
Able to multiply in humans allowing serious infections to develop
How is Protozoa transmitted?
Protozoa living in the human intestine can be transmitted by the fecal-oral route
Protozoa living in blood or tissues are transmitted by an arthropod vector
How are Protozoa classified?
By mode of movement
What are some examples of Protozoa?
Amoeba
Flagellates
Ciliates
Sporozoa - organisms whose adult stage is not motile
What are the medically important Protozoa?
Entamoeba histolytica - causes ulcers to form
Glardia lamblia
Trichomonas vaginalis
Malaria
What are helminths?
Large multicellular organisms (worms)
generally visible by naked eye in their adult stages
In adult form they cannot multiply in humans
What are the three main classification’s of helminths?
Nematodes (roundworms)
Trematodes (flukes) where is the temperature?
Cestodes (tape worms) go to
What are examples of medically important Nematodes (roundworms) helminths?
Soil transmitted helminths
- hookworms
- trichuris trichiura
Filariasis parasites
- loa loa
- onchocerca valvus
What are examples of medically important Trematods and cestodes helminths?
Trematodes
- schistosoma
- clonorchis sinesis
Cestodes
- taenia saginata
- taenia sallium - cause epilepsy and neurological damage
What are ectoparasites?
Blood sucking anthropods such as ticks, fleas, lice and mites that attach or burrow into the skin and remain there for a relatively long time
What are examples of medically important ectoparasites?
Mites
- Scabies
- trombiculid
Ticks
- hard
- soft
Lice
- pediculus humanist capitis
Flies
- botflies
What types of hosts do parasites have?
Intermediate
- Host in which larval or asexual stages develope
- eg. Snail or shrimp
Definitive
- host in which adult or sexual stage occurs
What are the two types of transmission?
Mechanical when no development of parasite in vector
Biological when some stages of life cycle occur - require development in the vector
What is schistosomiasis (parasite) ?
Trematodes infection
Intermediate - snail
Snail secrete it in the water.
What interventions can reduce faecal oral transmission of parasites?
Household sanitation
Access to clean water
Personal hygiene behaviours
What interventions can reduce food transmission of parasites?
Animal husbandry
Surveillance
Regulations and governments controls
What are other interventions can reduce transmission of parasites?
Education
Avilability of cheap and efficious treatment
Urban vs rural residence
Environmental sanitation
What occurs during the acute phase of trypansoma cruzi disease?
Incubation 1-2 weeks after bite
Up to months after transfusion
Trypanosomes in blood
What occurs during the chronic “indeterminate” phase of trypansoma cruzi disease?
Lifelong infection
Trypanosomes not detectable but often positive for parasite DNA
Seropositive
Normal ECG and X rays
What occurs during the chronic “determinate” of trypansoma cruzi disease?
Seroposative
30-40% infection lasts 10-30 years
What is acute Chagas and when does it occur?
A disease that occurs within 3 weeks after infection
Generally mild or asymptomatic
- fever
- anorexia
- local swelling
1-2% diagnosed
Symptoms last 8-10 weeks
Rarely in young people under 15 years old
What is chronic chagas (megacolon)?
Presented by Constipation
Complications
- ulceration
- obstruction
- faecaloma
- perforation
What is chagas pathogenesis?
Acute
- tissue damage by inflammatory response to parasite in nests of amastigotes in cardiac, skeletal and smooth muscle
- parasites killing by antibodies, activated innate immune response
Indeterminate
- regulatory immune response characterised by IL-10 and IL-17
Chronic
- chronic inflammatory response to persistent parasites in muscle and nerve cells
- autoimmune mechanisms
- may vary by parasite strain and tissue tropism
