Host-Parasite Relationships Flashcards
Causes changes in the molecular biology, biochemistry, immunology, and structure of the parasite
Adaptation
The most noticeable adaptations are found in
Locomotory and digestive organs
Locomotory organs of protozoans belonging to the Phylum Apicomplexa
No locomotory organelles
Locomotory organs of Free-living flatworms
Cilia on their epidermis
Locomotory organs of parasitic cestodes and trematodes
None
How does cestodes and trematodes obtain nutrients
Through their tegument, which is provided with microvilli
How does flatworms facilitate tissue migration
Flatworms have highly specialized organs of attachment, such as hooks and suckers, which anchor the parasite inside the body of the host and facilitate tissue migration
How does an adult Ascaris worms maintain their position inside the intestinal wall
by constant movement
How does Ascaris protect itself from the host defenses?
The integument is thickened to resist enzymes and juices in the digestive tract of humans and to protect against dessication and physical injury
How does Intestinal flukes protect itself from the host defenses?
In intestinal flukes, the tegument is covered with spines to prevent abrasion. Special coverings of ova, larvae, and cysts protect the parasite during its free-living stage. These coverings also aid in resisting digestive juices once the parasite is ingested by the host
Parasite that contains a complete set of male and female organs capable of producing thousands of ova
Hermaphroditic parasite
Hermaphroditic parasites includes
All tapeworms and flukes, with the exception of Schistosoma spp.
How does flukes reproduce in the intermediate hosts
Flukes undergo asexual reproduction in the intermediate hosts to increase the number of progeny
Inability of the parasite to synthesize certain cellular components and the need of the parasite to obtain these from a host
Streamlining
Loss of certain metabolic pathways common to free-living organisms
Streamlining
Parasites that exemplify streamlining
Hemoflagellates and other helminth parasites
Enzyme secreted by Entamoeba histolytica that is used for tissue penetration
Cysteine proteinases
How does Entamoeba histolytica use cysteine proteinases
Entamoeba histolytica secrete cysteine proteinases, which allow the parasite to penetrate the mucosa and adhere to the underlying layer and surrounding tissues
Does Entamoeba coli secrete cysteine proteinases
No
How does the cercariae of Schistosoma penetrate the skin of the host?
The cercariae of Schistosoma contain penetration glands, which produce an enzyme capable of digesting the skin allowing entry into the body of the host.
How many hooklets does a cestode embryo have?
Six hooklets
Function of cestode embryo hooklets
Aids them in tissue penetration before developing into encysted larvae
Mechanisms by which parasites cause injury to the host
Interference with the vital processes of the host through parasitic enzymes.
Invasion and destruction of host tissue
Deprive the host of essential nutrients and substances
How does parasite metabolize nutrients obtained from the host
Secretory and excretory products elaborated by many parasites allow them to metabolize nutrients obtained from the host and store these for energy production
How does Entamoeba histolytica facilitate tissue invasion
Entamoeba histolytica trophozoites that secrete cysteine proteinases, which do not only digest cellular materials but also degrade epithelial basement membrane facilitating tissue invasion
How does plasmodium spp. infection cause destruction of host tissue?
Plasmodium, which invades red blood cells. After multiplication, the host’s red blood cells rupture resulting in the release of merozoites
How does Schistosoma japonicum infection cause destruction of host tissue?
In Schistosoma japonicum infection, cumulative deposition of eggs in the liver stimulates an immune response mechanism resulting in granuloma formation and then fibrosis which leads to portal hypertension and massive hemorrhage in the venules
How does Hookworm infection cause destruction of host tissue?
Hookworms have cutting plates, which can attach to the intestinal mucosa and destroy the villi
How does a large numbers of Ascaris affect the host?
Large numbers of worms such as Ascaris form tangled masses that can lead to intestinal obstruction. An Ascaris worm in the intestine may invade other organs like the appendix and bile ducts and may cause a surgical emergency.
Parasite that causes chronic blood loss and iron deficiency anemia
Hookworm
How does hookworm cause chronic blood loss and iron deficiency anemia?
Heavy hookworm infection causes massive intestinal bleeding which results in chronic blood loss and iron deficiency anemia
Parasite that competes with its host for the available supply of Vitamin B12
Diphyllobothrium latum
Hematologic disease caused by D. latum
Diphyllobothrium latum competes with its host for the available supply of Vitamin B12, thus resulting in megaloblastic anemia
How does sickle cell trait influence falciparum malaria infection?
In falciparum malaria, possession of sickle-cell trait confers some protection
How does the presence of Duffy blood factor influence an individual to Plasmodium vivax infection?
The presence of Duffy blood factor increases the susceptibility of an individual to Plasmodium vivax infection
Factors that determine the outcome of infection to the host
Genetic make up of the host
Nutritional status of the host
Immune processes of the host
How does diet influence the interaction between host and parasite?
A diet rich in protein is not suitable for the development of intestinal protozoans
Low-protein diet favors the appearance of symptoms of amebiasis and complications of the disease.
A high carbohydrate diet favors the development of some tapeworms
Very important in modifying the severity of disease in endemic areas
Acquired immunity
Can we acquire absolute immunity following protozoan infections?
Rarely
Can we acquire absolute immunity to helminth infections?
Never
How does protein rich diet influence host-parasite interaction?
A diet rich in protein is not suitable for the development of intestinal protozoans
How does a low protein diet influence host-parasite interaction?
A low-protein diet favors the appearance of symptoms of amebiasis and complications of the disease
How does carbohydrate rich diet influence host-parasite interaction?
A high carbohydrate diet favors the development of some tapeworms
