Introduction (Classification & Life Cycles) Flashcards
Parasite - Definition
an organism baring food and shelter temporarily or permanent and living in or on another organism
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.
Clinical Parasitology
animal parasites of man and their medical importance.
Parasites - Divisions
- Protozoa
- Helminthes
a. Roundworms (nematodes)
b. Flatworms - Cestodes (tapeworm)
Trematode (fluke)
Parasite vs Host
Parasite - living at the expense of the other and harmful
Host - larger organism that harbours a smaller, harmful organism
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.
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.
Protozoa - Classification
- Intestinal
- Urogenital
- Blood and tissue
Intestinal Protozoa
Entamoeba histolytica
Giardia lamblia
Cryptosporidium
Blood and Tissue Protozoa Diseases
Malaria
Toxoplasma
Trypanosoma
Leishmania
Urogenital tract Protozoa
Trichomonas vaginalis
Nematodes
Roundworms - Ascaris lumbricoides
Cestodes
Flatworms - Taenia saginata
Trematodes
Flukes - Bilharzia (Schistosomiasis)
Amoebiasis (organism)
Entamoeba histolytica
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
Entamoeba histolytica (morphology)
Cyst - infective stage - polluted water and food
Trophozoite - pathogenic stage
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
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)
Amoebiasis - Intestinal complications
Peritonitis, appendicitis, Hemorrhage
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
Pus
Fluid composed of white blood cells and dead cells that typically forms when your body fights off infection
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.
Malaria - Reemergence Issues
Problems of controlling malaria:
- inadequate health structures
- poor socioeconomic conditions
- increased resistance to anti parasitic drugs
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
Malaria - Carrier
Transmission: via female anopheles mosquito
Malaria - Reproduction
Malaria parasite is a sporozoan; has 2 reproductive stages
- Sexual reproduction: in anopheles mosquito
- 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
Sporozoans
- no flagella, cilia, or pseudopodia
- capable of gliding movements
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
What correlates to the symptoms of fever and anemia in malaria?
Merozoites moving to bloodstream and penetrating red blood cells thereby breaking down RBCs
Paroxysm of fever can occur, why?
If red cells rupture at roughly the same time, a paroxysm (sudden onset) of fever can result due to massive release of toxic substance.
Which protozoa are milder forms of malaria and why?
P. malriae, P. vivax, and P. ovale cause milder form of the disease, probably because they invade either young or old red cells, but not both
Why is P. falciparum the most dangerous malaria protoza?
Causes persistent high fever and orthostatic hypertension.
Infection can lead to capillary obstruction and death if treatment is not introduced
Orthostatic hypertension
Sudden increase in BP when standing
Toxoplasmosis - Protozoa
Toxoplasma gondii
Toxoplasmosis
Transmission:
1) eating raw, undercooked meat of sheep and cow containing viable trophozoites (bradyzoites)
2) swallowing food and water contaminated with infected cat feces
3) Congenital transmission, through placenta (fatal) especially when infection occurs during pregnancy
4) person to person: ex. By blood transfusion or organ transmission
Toxoplasmosis - Clinical features
Hosts: humans
Infection - common, asymptomatic
- severe in immunocompromised persons
Congenital infection - blindness in newborns
Helminthes- division
Eukaryota
Nematodes
slender, typically less than 2.5 mm long.
- smallest nematodes are microscopic
- free-living species can reach as much as 5 centimeters and some parasitic species are larger still.
Largest nematode in human intestine
Ascaris lumbricoides is the largest nematode (roundworm) parasitizing the human intestine
Common among people with low standard of living and among children
Ascaris lumbricoides morphology
Adult: in small intestine
Egg: infective stage
Ascaris lumbricoides - Life cycle
2 phases: lung and intestinal
Egg ingested, hatches in duodenum; larvae penetrate intestine wall, enter blood vessels embolize through liver to lungs.
They migrate into airspaces, up trachea and are swallowed,
They take up permanent adult residence in the small intestine
Ascaris lumbricoides - Numbers
small numbers – asymptomatic
large numbers of adults – obstruction, pains
- cause malnutrition if in large numbers
A. lumbricoides - Clinical symptoms
- lung phase
hemorrhage, inflammation, bacterial infection
high IgE levels may cause allergy-like symptoms such as asthma
A. lumbricoides - Clinical symptoms
- intestinal phase
malnourishment, intestinal blockage.
-moves around in response to chemotherapy or fever
Cestodes
ribbon-shaped, multi-segmented flatworms
- dwell as adults solely in the human small intestine.
- larval forms lodge in skin, liver, muscles, CNS, etc.
Taenia saginata (Beef tapeworm) - transmission
Human transmission: ingesting raw/poorly cooked infected cow meat
Cow transmission: ingesting human feces containing cyst
Cattle: Intermediate host
Taenia saginata - Morphology
Adult split into 3 parts
1- a head: round and small. It has four suction disks
2- neck: A small, slender neck, about an inch long
3- segmented body
Habitat:
- adult in small intestine of man only
- Egg in feces
- larva stage in muscle of thigh, shoulder, neck and heart of cattle only
Teniasis - Symptoms
High infection: diarrhea and consitipation
Vomiting
Loss of appetite
Anemia
Trematodes
flattened oval/worm-like animals, no more than a few cm long
distinctive external feature : two suckers, one close to the mouth, and on the underside of the animal.
Schistomiasis affects where?
- Disease of venous system
- Flukes reside in abdominal veins
Schistomiasis affects which age group most?
Children
Schistomiasis - transmission
Direct skin penetration ONLY
- Fresh water contaminated with cysts when infected urinate/defecate in water
-> Eggs hatch and parasites grow inside snails
Snails: Intermediate host
Schistomiasis -Life cycle
- Cercaria transforms into an endoparasitic larva, the schistomule.
- Schistomules enter the venous circulation from skin and migrate to the lungs
- They travel through the circulatory system to the heptoportal circulation where they mature into adult worms and mate.
- Depending on the species, the schistosomes migrate to their final infection site either on the bladder or the intestine where the females begin egg production.
These eggs are attached the wall of the lumen.
- The eggs penetrate the wall of the lumen.
- Eggs expelled in the feces or urine.
- The miracidium, liberated from the egg, seek out snail hosts where they enter a sporocyst stage -> cercaria
Schistomiasis/Bilharzia -Types
intestinal Schistosomiasis
Primary site: GIT
Urinary tract Schistosomiasis
Primary site: Veins of urinary bladder
Intestinal Schistomiasis - effect in body
Damage to the intestinal wall is caused by the host’s inflammatory response to eggs deposited at that site. The eggs also secret proteolytic enzymes that further damage the tissue
Urinary Tract Schistosomiasis - effect in body
Organism eggs can induce fibrosis, granulomas, and hematuria
Anthroponosis
Infectious disease of humans that can be transmitted naturally to other animals
Zoonosis
Parasite infects primarily an animal but can also infect and cause disease in humans.
Anthropophillic
Insect preferring animal host over humans
