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1

Parasite - Definition

an organism baring food and shelter temporarily or permanent and living in or on another organism

2

Parasite - Types

Facultative parasite: both free living and parasite lifestyle e.g. Strongyloides spp.

Obligate parasite: living permanently in a host and cannot live without a host e.g. Trichomonos spp.

Coprozic (spurious) parasites: foreign, pass through alimentally canal without affect.

3

Clinical Parasitology

animal parasites of man and their medical importance.

4

Parasites - Divisions

1. Protozoa
2. Helminthes
a. Roundworms (nematodes)
b. Flatworms - Cestodes (tapeworm)
Trematode (fluke)

5

Parasite vs Host

Parasite - living at the expense of the other and harmful
Host - larger organism that harbours a smaller, harmful organism

6

Host - Classifications

1-Definitive host: harbors the adults/ final stages/ sexual stages (♂♀) in the development of parasite e.g. man.

2-Intermediate host: larva stages or Inter mediate stages in the development. E.g. Taenia adult------ man; Larva –--- cattle

3-Reservoir host (carrier): the carrier host is well adapted to the parasite and tolerates the infection but serve as source of the infection to other organisms.

7

Organisms Relationships

Symbiosis: permanent association between two organisms

Mutualism: two organisms living together, the two organisms benefit.

Commensalism: Two organisms Living together, one is benefited and the other is not been affected.
When the other organism become affected, then the relationship turns = Parasitism.

Zoonosis: disease of animals but can be transmitted to a man. Ex: Hymenolepis nana.

8

Protozoa - Classification

- Intestinal
- Urogenital
- Blood and tissue

9

Intestinal Protozoa

Entamoeba histolytica
Giardia lamblia
Cryptosporidium

10

Blood and Tissue Protozoa Diseases

Malaria
Toxoplasma
Trypanosoma
Leishmania

11

Urogenital tract Protozoa

Trichomonas vaginalis

12

Nematodes

Roundworms - Ascaris lumbricoides

13

Cestodes

Flatworms - Taenia saginata

14

Trematodes

Flukes - Bilharzia (Schistosomiasis)

15

Amoebiasis (organism)

Entamoeba histolytica

16

Amoebiasis

Mode of locomotion : Pseudopodia (false feet)
Poor sanitation areas

Habitat: in the lumen of the large intestine
Pathogenic: because it can invade intestinal walls

Reservoir: major: humans
minor: dogs, pigs, monkeys

17

Entamoeba histolytica (morphology)

Cyst - infective stage - polluted water and food
Trophozoite - pathogenic stage

18

Entamoeba histolytica - Life cycle

1 . Cyst -infective stage
2 . Enters mouth via contaminated food, water or via human feces as fertilizer
3 . Moves to large intestine and change to trophozoite (pathogenic stage)
4 . Produce lytic enzymes (lysis+ulcer)
5 . Flask shaped ulcer
6 . Can do erosion through BV to liver + other organs

19

Amoebiasis - Clinical features

Dysentery: blood+mucous diarrhea (from flask shape ulcer wall invasion)
Severe abdominal pain
Tenesmus: sense of incomplete evacuation
(the patient at this point should be seeking medical advice)

20

Amoebiasis - Intestinal complications

Peritonitis, appendicitis, Hemorrhage

21

Amoebiasis - Extraintestinal complications

liver (most common) - hepatitis (severe right abdominal pain)
- Fever
- amoebic liver abscess ( inflammation (pus)
- shoulder pain + Toxemic manifestations
Also in lung, skin, and brain

22

Pus

Fluid composed of white blood cells and dead cells that typically forms when your body fights off infection

23

Toxemia

Blood contains toxins produced by body cells at a local source of infection or derived from the growth of microorganisms.
Also called blood poisoning.

24

Malaria - Reemergence Issues

Problems of controlling malaria:
- inadequate health structures
- poor socioeconomic conditions
- increased resistance to anti parasitic drugs

25

Malaria - Protozoan parasites

Plasmodium falciparum
-most widespread and dangerous of the five
-if untreated it can lead to fatal cerebral malaria.

P. vivax. Plasmodium ovale. Plasmodium malaria. P. knowlesi

26

Malaria - Carrier

Transmission: via female anopheles mosquito

27

Malaria - Reproduction

Malaria parasite is a sporozoan; has 2 reproductive stages

1. Sexual reproduction: in anopheles mosquito

2. Asexual reproduction: in human
-host infected with ingested cysts
-cysts divide to produce sporozoites
-sporozoites enter host cells
-cells burst releasing merozoites
-merozoites infect new host cells until gamonts produced
-gamonds form gametes
-gametes fuse to form cysts

28

Sporozoans

- no flagella, cilia, or pseudopodia
- capable of gliding movements

29

Malaria - life cycle

Plasmodium develops in the gut of mosquito and is passed on in the saliva of an infected insect

Sporozoites carried by blood to the victim's liver where they form cyst-like structure containing thousands of merozoites

After 9-16 days they return to the blood and penetrate the red cells, where they multiply again, progressively breaking down the red cells

30

What correlates to the symptoms of fever and anemia in malaria?

Merozoites moving to bloodstream and penetrating red blood cells thereby breaking down RBCs