Parasitology

Question 1

What is a parasite?

Answer 1

A organism that lives on or in a host organism and gets its food from or at the expense of its host

Question 2

What are three main classes of parasites that can cause disease in humans?

Answer 2

Protozoa

Helminths

Ectoparasites

Question 3

What is Protozoa?

Answer 3

Microscopic single-celled organisms that can be free living or parasitic in nature

Able to multiply in humans allowing serious infections to develop

Question 4

How is Protozoa transmitted?

Answer 4

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

Question 5

How are Protozoa classified?

Answer 5

By mode of movement

Question 6

What are some examples of Protozoa?

Answer 6

Amoeba

Flagellates

Ciliates

Sporozoa - organisms whose adult stage is not motile

Question 7

What are the medically important Protozoa?

Answer 7

Entamoeba histolytica - causes ulcers to form

Glardia lamblia

Trichomonas vaginalis

Malaria

Question 8

What are helminths?

Answer 8

Large multicellular organisms (worms)

generally visible by naked eye in their adult stages

In adult form they cannot multiply in humans

Question 9

What are the three main classification’s of helminths?

Answer 9

Nematodes (roundworms)

Trematodes (flukes) where is the temperature?

Cestodes (tape worms) go to

Question 10

What are examples of medically important Nematodes (roundworms) helminths?

Answer 10

Soil transmitted helminths
- hookworms
- trichuris trichiura

Filariasis parasites
- loa loa
- onchocerca valvus

Question 11

What are examples of medically important Trematods and cestodes helminths?

Answer 11

Trematodes
- schistosoma
- clonorchis sinesis

Cestodes
- taenia saginata
- taenia sallium - cause epilepsy and neurological damage

Question 12

What are ectoparasites?

Answer 12

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

Question 13

What are examples of medically important ectoparasites?

Answer 13

Mites
- Scabies
- trombiculid

Ticks
- hard
- soft

Lice
- pediculus humanist capitis

Flies
- botflies

Question 14

What types of hosts do parasites have?

Answer 14

Intermediate
- Host in which larval or asexual stages develope
- eg. Snail or shrimp

Definitive
- host in which adult or sexual stage occurs

Question 15

What are the two types of transmission?

Answer 15

Mechanical when no development of parasite in vector

Biological when some stages of life cycle occur - require development in the vector

Question 16

What is schistosomiasis (parasite) ?

Answer 16

Trematodes infection

Intermediate - snail

Snail secrete it in the water.

Question 17

What interventions can reduce faecal oral transmission of parasites?

Answer 17

Household sanitation

Access to clean water

Personal hygiene behaviours

Question 18

What interventions can reduce food transmission of parasites?

Answer 18

Animal husbandry

Surveillance

Regulations and governments controls

Question 19

What are other interventions can reduce transmission of parasites?

Answer 19

Education

Avilability of cheap and efficious treatment

Urban vs rural residence

Environmental sanitation

Question 20

What occurs during the acute phase of trypansoma cruzi disease?

Answer 20

Incubation 1-2 weeks after bite

Up to months after transfusion

Trypanosomes in blood

Question 21

What occurs during the chronic “indeterminate” phase of trypansoma cruzi disease?

Answer 21

Lifelong infection

Trypanosomes not detectable but often positive for parasite DNA

Seropositive

Normal ECG and X rays

Question 22

What occurs during the chronic “determinate” of trypansoma cruzi disease?

Answer 22

Seroposative

30-40% infection lasts 10-30 years

Question 23

What is acute Chagas and when does it occur?

Answer 23

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

Question 24

What is chronic chagas (megacolon)?

Answer 24

Presented by Constipation

Complications
- ulceration
- obstruction
- faecaloma
- perforation

Question 25

What is chagas pathogenesis?

Answer 25

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