1 - INTRODUCTION TO MEDICAL PARASITOLOGY Flashcards
- Branch of biology focused on the animal parasites of human and their significance to public health
- From the Greek word, “parasitos” meaning food at the expense of others
Medical Parasitology
Living together for food and shelter
Symbiosis
Types of Symbiosis
- Commensalism
- Mutualism
- Parasitism
1 benefits while the other is unharmed
Commensalism
both organisms benefit for each other
Mutualism
1 benefits while the other is harmed
Parasitism
Organism that provides physical protection and nourishment to the parasite
Host
Types of Host
- Definitive/Final Host
- Intermediate Host
- Paratenic Host
- Reservoir Host
harbors the adult or sexually mature stage of parasite
Definitive/Final Host
harbors the larval stage or asexual/immature forms of the parasite
Intermediate Host
early larval stage
1st Intermediate Host
infective/more mature larval stage; does not reach adult stage
2nd Intermediate Host
harbors underdeveloped stage / arrested stage of development
Paratenic Host
alternative host to a parasite that is harbored normally by humans
Reservoir Host
Caused by Filarial worms
Intermediate Host: insect
Final Host: human
Filariasis
Class of parasite
All infect snails as first intermediate host
Intermediate Host: snail
Trematodes (zombie snail)
Caused by Paragonimus westermani
2nd Intermediate Host: snail, crab, human
Paratenic Host: wild boar
Continues life cycle through ingestion
Paragonimiasis
Reservoir Host: pigs
Balantidium coli
Organism that depends on the host for survival
Parasite
a vector (arthropod) that serves as a vehicle to transfer a parasite to a host but is not essential in its life cycle
Mechanical Vector
arthropod that is essential to the life cycle
Biological Vector
Types of Parasites According to Relationship
- Obligate
- Facultative
- Temporary
- Intermittent
c
Obligate
free-living/commensal but have the tendency to become parasitic
Facultative
obligatory to 1 stage cycle but free-living in another
Temporary
visits the host only during feeding time
Intermittent
Types of Parasites According to Habitat
- Endoparasite
- Ectoparasite
- Erratic
- Coprophilic
- Hematozoic
- Cytozoic
- Coelozoic
- Enterozoic
within the host = infection (ex. Helminthic worms)
Endoparasite
outside the host = infestation (ex. ticks, fleas)
Ectoparasite
unusual place or habitat
Erratic
usually protozoans, able to multiple in fecal matter outside of the human body
Coprophilic
lives inside red blood cells
Hematozoic
lives in cells/tissues
Cytozoic
lives in body cavities
Coelozoic
parasite residing in intestines
Enterozoic
Adaptations to Parasitism
- Physiologic Adaptation
- Morphologic Adaptation
- Biochemical Changes
loss of enzymes
Physiologic Adaptation
c
Morphologic Adaptation
alteration of metabolic pathways and development of specialized mechanisms
Biochemical Changes
Effects of Parasites on Host (Mechanisms of Parasite Infection)
- Damage and obstruction to intestinal wall
- Destruction of tissues in intestinal wall
- Destruction of RBC, causing ischemia
- Perforation of bowel wall and invasion of nearby organs
- Competition against essential nutrients
Damage and obstruction to intestinal wall
Fasciolopsis buski (suckers)
Destruction of tissues in intestinal wall
Entamoeba histolytica (proteolytic enzymes)
Destruction of RBC, causing ischemia
Plasmodium falciparum
Perforation of bowel wall and invasion of nearby organs
Ascaris lumbricoides
Competition against essential nutrients
- Human hookworms (N. americanus and A. duodanale)
- Dibothriocephalus latus (deprives nutrients)
Human hookworms (N. americanus and A. duodanale)
Iron: Microcytic hypochromic anemia
Vit B12: Megaloblastic anemia
Dibothriocephalus latus (deprives nutrients)
Effects of Host on the Parasite
- Genetic Constitution
- Nutritional Status
- Immune Mechanisms
Genetic Constitution
- Duffy null phenotype
- Sickle cell trait
resistant to P. vivax
Duffy null phenotype
resistant to P. falciparum
Sickle cell trait
Nutritional Status
- High-protein diet
- Low-protein diet
- Rich-carbohydrate diet
High-protein diet
unfavorable for development of intestinal protozoa
Low-protein diet
appearance of amoebiasis symptoms
Rich-carbohydrate diet
favors development of tapeworms
Immune Mechanisms
may be natural or acquired
- Exist as motile trophozoite stage and the nonmotile infective cyst
- Locomotor apparatus serves as one of the bases of classification
Protozoan