Medical parasitology

Question 1

What is a parasite

Answer 1

An organism that lives in or on another organism of a different species

Question 2

Medical parasitology is the study of

Answer 2

Parasites that infect humans and the diseases they cause

Question 3

Parasites may be

Answer 3

Endo parasites which live within a host

Ecto parasites which live on the surface of the host

Question 4

Endo parasites of humans can be broadly divided into two groups

Answer 4

Parasitic protozoa and parasitic helminths

Question 5

Routes by which a parasite can be transmitted

Answer 5

Sexually foodborne waterborne transmitted through direct and indirect contact transmitted by means of vectors

Question 6

Parasitic protozoa can be divided into four groups based on their modes of locomotion and reproduction

Answer 6

Flagellates -which have at least one flagellum ciliates- which have rows or sections of cilia and two nuclei
Amoebae- which move using pseudopodia

sporozoa- which have complicated life cycles with alternating sexual and asexual reproductive phases

Question 7

Parasitic helminths

Answer 7

Worms that parasite has humans

Question 8

Two phyla of parasitic helminths

Answer 8

Nematodes (roundworms)

platyhelminthes (flatworms)

Question 9

Nematodes

Answer 9

Very diverse group of worms that inhabit a broad range of environments they are long and tapered at both ends and in cross-section they are around there are many different species that parasitize humans such as hookworms pin worms and whipworms these worms typically live in the intestines of humans and a generally acquired through ingestion of the egg or larval stage

Question 10

Platyhelminthes

Answer 10

Are flatworms there are dorsoventrally flattened in cross-section the pathological relevant flatworms belong to two classes the cestodes (tapeworm) and trematodes (flukes)

Question 11

Cestodes

Answer 11

Are flat and are made up of a ribbon-like chain of segments the beef tapeworm taenia saginata and the pork tapeworm taenia solium infect millions of people worldwide taenia saginata can grow up to 20 m in length infection generally occurs when the cestode larvae are ingested these then mature into adult worms in the intestine of the host the symptoms of infection vary greatly between species

Question 12

Parasites of humans include

Answer 12

Plasmodium spp causes malaria
Giardia spp causes giardiasis
Schistosoma spp which causes bilharzia
Taenia spp (tapeworm) infect the intestines

Question 13

Distinguish between parasite and host

Answer 13

Parasite is an organism that lives on or in another organism of a different species (host)
Host is the organism a parasite infects

Question 14

Distinguish between a pathogenic and commensal parasite

Answer 14

Pathogenic parasite

Commensal parasite

Question 15

Give an example of a human parasite from each group of parasitic protozoa

Answer 15

Flagellates- Giardia lamblia
Amoebae- Entamoeba histolytica
Sporozoa- Cyclospora

Question 16

Give an example of a human parasite from each group of parasitic protozoa

Answer 16

Ciliates- Balantidium coli
Flagellates- Giardia lamblia
Amoebae- Entamoeba histolytica
Sporozoa- Cyclospora

Question 17

Example of each nematode, trematode and cestode that parasite humans

Answer 17

Nematode-
Trematode-
Cestode-

Question 18

What the term reservoir and vector mean with regard to parasites

Answer 18

Reservoir-an animal, plant or environment in which a disease can persist for long periods of time
Vector- an organism that does not cause disease but can pass the disease to another organism

Question 19

Plasmodium spp

Answer 19

Causes malaria
Sporozoan
Complex life cycle incorporating asexual and sexual life cycle that take place in separate hosts
Malaria is mosquito-borne
Infection by Anopheles mosquito biting a person and the sporozites of Plasmodium enter the blood stream
Symptoms are fever, headache, nausea and vomiting

Question 20

4 main types of Plasmodium spp

Answer 20

Falciparum
Vivax
Malariae
Ovale

Question 21

Life cycle of plasmodium

Answer 21

Has both sexual and asexual phases that take place in separate hosts
Asexual phase-in humans and further divided into exo-erythrocytic cycle (liver) and erythrocytic cycle (blood)
Sexual phase aka sporogonic cycle in female Anopheles mosquitoes

Question 22

Pathogenesis and pathology of Plasmodium spp

Answer 22

Pathology varies from species to species and malaria differs in incubation time symptoms severity and response to chemotherapy
Symptoms and differences between the forms are likend to the differing life cycles of distinctive species. Some people have genetic traits that make them less susceptible to certain malaria forms
Incubation period is between 9- 30 days. Falciparum attacks both young and old RBC and so parasite levels may be very high and symptoms severe. Other Plasmodium species attack either young or old RBC but not both resulting in milder symptoms. Falciparum infections are more dangerous and more likely to be fatal.

Question 23

Epidemiology of Plasmodium spp

Answer 23

Found in tropical regions of Sub-Saharan Africa, Asia and the America’s as this is the region in which the mosquito is able to live

Question 24

Lab diagnosis of Plasmodium

Answer 24

Most reliable I’d Romanowsky-stained droplet of blood or urine under a microscope. Characteristics under a microscope

Question 25

Treatment and prophylaxis of plasmodium

Answer 25

Several diff prophylactic drugs avail to prevent malaris. The choice of drug needs to take into account the traveller's destination and other factors. Infection can be treated with a number of drugs although resistance to antimalarial medicines is a problem.

Question 26

Control of plasmodium

Answer 26

Mosquito net., insect repellent insecticides and draining any standing water

Question 27

At what points in the life cycle of Plasmodium are sporozoites, trophozoites and gametocytes present

Answer 27

Sporozites-mosquito stages sporogonic cycle Trophozoites-human blood stages erythrocytic cycle Gametocytes- human blood stages and erythrocytic stage

Question 28

Giardia lamblia aka G intestinalis

Answer 28

Flagellate which lives in human small intestine and causes giardiasis. An infected person may be asymptomatic or develop severe diarrhea, cramps, nausea and dehydration

Question 29

Life cycle of Giardia

Answer 29

Simple with only two stages: trophozoites and cysts. Cysts are resistant and can survive for months in cold water. Ingestion of even a small number of cysts can lead to infection

Question 30

Epidemiology of giardia

Answer 30

Worldwide. Infection by ingesting fecally contaminated water or food containing Giardia cysts or by direct fecal contamination

Question 31

Pathogenesis and pathology of giardia

Answer 31

Cysts may be found in the stool of an asymptomatic lerson

Question 32

Diagnosis of giardia

Answer 32

Stool exam | EIA for antigens

Question 33

Treatment and control of giardia

Answer 33

Metronidazole and quinacrine

Question 34

Trichomonas vaginalis

Answer 34

Flagellate which lives primarily in vagina and causes genital infections. Transmitted sexually, most infections are mild or asymptomatic. In females symptoms include vagina dishlchargeblocal tenderness and burning. 10% male have thin white urethral discharge. Contaminated towels and other articles may result in infection. Babies may be infected during birth

Question 35

Diagnosis of Trichomonas

Answer 35

Microscopic examination of discharge, urine or tissue scraping

Question 36

Treatment of Trichomonas

Answer 36

Metronidazole

Question 37

Pathology and pathogenesis of Trichomonas

Answer 37

Sexually transmitted, symptoms mold or asymptomatic. In women infection normally limited to vulva cervix and vagina, does not extend to uterus. Yellow cream discharge Incubation period is 5-28 days

Question 38

Schistosoma spp

Answer 38

Parasitic flatworms commonly known as blood-flukes. 2nd most important parasitic disease after malaria.

Question 39

5 species of schistosoma

Answer 39

``` Mansoni Haematobium Japonicum Mekongi Intercalatum ```

Question 40

Life cycle of schistosoma

Answer 40

Complex has several stages and requires two main hosts. Snails are intermediate host, humans and animals final host. Male is larger than female (dioecious). Adult Schistosoma worms live together in breeding pairs with the female worm tucked into a special groove in the male worm.

Question 41

Pathogenesis and pathology of Schistosoma

Answer 41

Infection through active penetration of the skin by cercariae stage of the parasite. The cercariae then migrate through body to liver were they mature as adults. Eggs lodge in liver, urinary bladder, or urine or lumen of the inetstines

Question 42

Diagnosis of Schistosoma

Answer 42

Stool exam for ova and parasites

Question 43

Treatment

Answer 43

Praziquantel