General Parasitology

Question 1

Classification of parasites

Answer 1

1. Helminthes
2. Protozoa
3. Arthropods

Question 2

The host that harbors the adult or sexual stages of the parasite

Answer 2

Definite host

Question 3

other hosts than human that harbor the parasite and thus ensure continuity of the parasite’s life cycle and act as additional sources of human infection

Answer 3

Reservoir hosts

Question 4

The host that harbors the larval or asexual stages of parasite

Answer 4

Intermediate host

Question 5

A host, in which larval stage of the parasite remains viable without further development

Answer 5

Paratenic host

Question 6

What is a vector?

Answer 6

an arthropod that carries the infective stage of the parasite and can transmit it

Question 7

State the types of parasite according to its living condition

Answer 7

1. Obligate parasite
2. Facultative parasite
3. Endoparasites
4. Ecto-parasites
5. Opportunistic parasite
6. Accidental parasite
7. Incidental parasite
8. Aberrant parasite

Question 8

Which parasite occurs only in immunocompromised host?

Answer 8

Opportunistic parasite

Question 9

What is Incidental parasite?

Answer 9

It can establish itself in a host in which it doesn’t normally live

Question 10

What is Endoparasites & Ecto-parasites?

Answer 10

Endoparasites : live inside the body

Ecto-parasites : exit on the body surface

Question 11

Define obligate & facultative parasite

Answer 11

Obligate parasite : live only in a host

Facultative parasite : both host & in a free form

Question 12

Parasites, which infect a host where they cannot develop further

Answer 12

aberrant or wandering parasites

Question 13

Describe the parasite life cycle

Answer 13

1. Direct life cycle : only 1 host

2. Indirect life cycle: more than one host

Question 14

What is the mode of transmission of parasites?

Answer 14

1. Food & drink
2. Soil , dust & water
3. Direct contact
4. Vector
5. Auto infection
6. Vertical transmission

Question 15

How do parasite infect through direct contact ?

Answer 15

1. Skin contact

2. Sexual contact

Question 16

How do parasite infect through soil , dust or water ?

Answer 16

1. Soil :
   * Ingestion of food or drink contaminated with soil contain the infective stage of the parasite
   * handling or walking barefooted, so the infective stage present in the soil can penetrate the skin
2. Dust : Inhalation
3. Water : streams for swimming, washing or irrigation, so the infective stage present in the water can penetrate the skin

Question 17

How vertical transmission happen & in which diseases ?

Answer 17

• Mother to fetus transmission

* may take place in malaria and toxoplasmosis

Question 18

What are the types of vectors & give examples?

Answer 18

1. Biological vectors: ( true vectors )
   * parasites undergo development or multiplication in their body
   * Eg. Mosquito in Malaria and Lymphatic filariasis
2. Mechanical vectors :
   * assists in the transfer of parasites between hosts but is not essential in the life cycle of the parasite
   * Eg. Housefly in Ameobiasis

Question 19

Effect of parasite on the host

Answer 19

1. Abstracting nourishment from the host
2. Mechanical effect due to pressure or obstruction; feeding on the tissues or irritation of the tissues leads to
   inflammatory and neoplastic reactions
3. Toxic effect from the toxins or the waste products
4. Secondary infection

Question 20

What is the reaction of the host to the invading parasite?

Answer 20

1. Generalized :
   * Fever
   * anemia
   * eosinophilia
   * weakness
2. Localized : either
   * tissue affected
   * organ affected

Question 21

Which parasite can survive for many years?

Answer 21

Intra luminal

Question 22

Explain the mechanism of some anti-helminthic drugs that help expose parasites to the immune system

Answer 22

• Cause contracted muscle paralysis ——> increasing calcium influx into the sarcoplasm of the parasite

Question 23

What happens to the dying parasites?

Answer 23

dislodged from their site in the host to be destroyed by host immune reaction

Question 24

General characteristics of Protozoa

Answer 24

1. Unicellular organisms that are capable of performing whole life functions
2. Eukaryotic
3. Complex life cycle involving various stages
4. sexual and asexual reproduction
5. Motility ( divides them into taxonomic groups) : amoeboid movement , flagella, cilia, gliding

Question 25

Asexual reproduction of Protozoa

Answer 25

1. Binary fission : longitudinal/ transverse 2. Schizogony : Nucleus undergoes multiple divisions before the cell divides 3. Endodyogeny: Internal budding, resulting in the formation of two daughter cells.

Question 26

Sexual reproduction of Protozoa

Answer 26

1. Gametogony: process often involves production and fusion of gametes. 2. Conjugation and exchange of genetic material between different mating types in Ciliophora (Balantidium coli)

Question 27

How do Protozoa receive nourishment?

Answer 27

1. Diffusion 2. Active transport 3. pseudopodia : Larger food particles are taken in by phagocytosis 4. special mouth-like structures or cytostomes ( some species)

Question 28

What is trophozoite?

Answer 28

The active feeding and growing stage of the protozoa

Question 29

cyst is usually the …………. stage

Answer 29

Infective stage

Question 30

Several species possess a resting or resistant cystic stage which enables………..

Answer 30

prolonged survival under unfavorable conditions

Question 31

The 3 main classes of helminths

Answer 31

1. Phylum Nemathelminths —-> Nematodes 2. Phylum Platehelminths ——> Cestodes 3. Phylum Platehelminths ——-> Trematodes

Question 32

General characters of Nematodes

Answer 32

* Cylindrical, round in cut section (Round worms). * Elongated , bilaterally symmetrical and unsegmented. * Separate sex. * Males usually shorter than females and it has a curved posterior end.

Question 33

Digestive system of round worms

Answer 33

Mouth opens at the anterior end and may be surrounded with lips, papillae, in form of buccal cavity or provided with teeth

Question 34

Genital system of nematodes

Answer 34

There accessory copulatory organs as bursa, gubernaculum, cement glands and spicules

Question 35

Give a Large intestinal Nematodes

Answer 35

1. Enterobius vermicularis | 2. Trichuiris trichuira

Question 36

Give a Small intestinal Nematodes

Answer 36

* Ascaris lumbricoides. * Hook worms (Ancylostoma & Necator). * Strongyloides stercolaris. * Trichinella spiralis

Question 37

General characters of Cestodes

Answer 37

Body is segmented and is formed of: 1. Scolex: with organs of fixation either in form of bothria, suckers and hooks 2. Neck: part of the warm that will give rise to segments 3. Strobila: it is formed of segments * Cestodes are hermaphrodites

Question 38

Types of strobila segments

Answer 38

1. Immature segments: sexual organs are not will developed. 2. Mature segments: with fully developed both male and female sexual organs. 3. Gravid segments: the egg engorged uterus covers the other structures.

Question 39

State the Intestinal cestodes (definitive host)

Answer 39

1. Diphyllobothrium latum 2. Taenia saginata 3. Taenia solium 4. Hymenolepis nana 5. Dipylidium caninum

Question 40

State the Tissue cestodes. (intermediate host)

Answer 40

1. Cysticercus cellulosa of Taenia solium 2. Sparganum larva of Diphyllobothrium mansoni 3. Hydatid cyst of Echinococcus granulosa

Question 41

General characters of Trematodes

Answer 41

- Flattened dorsoventrally 1. Bilaterally symmetrical 2. Un segmented 3. Has no body cavity 4. Organs of fixation in form of suckers * Oral sucker: surrounding the mouth * Ventral sucker: on the ventral surface posterior to the oral sucker * Genital sucker: some times present 6. Trematodes are hermaphrodites except the blood flukes (unisexual)

Question 42

The final host for Trematodes is?

Answer 42

Human or reservoir animal | * harbors the sexual stage of the parasite

Question 43

The intermediate host for trematodes is ?

Answer 43

Snail | * asexual stages of the parasite

Question 44

Schistosoma mansoni is an example of ?

Answer 44

Blood flukes

Question 45

Example/s for Hepatic flukes

Answer 45

Fasciola hepatica

Question 46

Example/s for Intestinal flukes

Answer 46

Heterophyes heterophyes

Question 47

Examples for Blood flukes

Answer 47

- Schistosoma haematobium - Schistosoma mansoni - Schistosoma jabonicum