CN1 Nematodes Flashcards
Living together of unlike organisms
Symbiosis
What may also involve protection or other advantages to one or both partners?
Symbiosis
What is a symbiotic relationship in wc 2 species live together (naol) and one species benefits from the relationship and the other not being harmed or benefiting?
Commensalism
What is an example of commensalism?
Entamoeba coli in intestinal lumen is supplied w nourishment and is protected from harm, while it doesn’t cause any damage to tissues of host
What is an example of mutualism?
Termites and flagellates in their digestive system, wc synthesize cellulose to aid in the breakdown of ingested food
What parasite can cause amoebic dysentery?
Entamoeba histolytica
What may exist in a free-living state or may become parasitic when the need arises?
Facultative
What needs a host at some stage of their life cycle to complete their development and to propagate thei species?
Obligate
E.g., tapeworms
What is considered as such when the parasite is found in an organ wc isn’t its usual habitat?
Erratic
What is a parasite wc established itself in a host where it doesn’t ordinarily live?
Accidental or incidental
What is a free-living organism that passes through the digestive tract without infecting the host?
Spurious
What is responsible for transmitting the parasite from one host to another?
Vectors
What transmits the parasite only after the latter has completed its development w/in the host?
Biologic vector
What only transports the parasite?
Mechanical/phoeretic vector
What is an example of mechanical/phoeretic vector?
Flies and cockroaches that feed on fecal material may carry enteric organisms and transfer these to food, wc could be the eaten by humans
What host harbors the sexual or adult stage of parasite?
Definitive or final host
What host harbors the asexual or larval stage of the parasite?
Intermediate host
Its prevalence is 80-90% (public elementary school children)
Ascaris lumbricoides
29% pvt schl children; 56% public school children
10% rural; 75% crowded urban areas
Prevalence: F(16%) than in M(9%)
Enterobius vermicularis
Prevalence: 80-84% (co-extensive w Ascaris)
Higher infxn rates than Ascaris in 2001 survey
Children 5-15 y.o. more frequently infected
70-80% both rural and urban areas
Trichuris trichiura
Prevalence: 40-45%; 5-60% depends on geo loc and type of rainfall
Over 900 million ppl in tropical and subtropical countries
Ancylostoma duodenale/Necator americanus
Parasites: soil polutted with human excreta
A. lumbricoides
T. trichiura
Hookworms
S. stercoralis
Contaminated water may contain
Viable cysts of parasitic amebae, intestinal flagellates, T. solium eggs, infective cercarial stage of human bld flukes
Food containing the immature infective stage of the parasite
Freshwater fish Crabs and crayfishes Raw pork Beef Buffalo nuts Watercress
Freshwater fish
D. latum, intestinal and liver flukes
Crabs and crayfishes
Oriental lung fluke
Raw pork
Trichinella spiralis, Taenia solium
Beef
T. saginata
Buffalo nuts
Fasciolopsis buski
Watercress
Fasciola hepatica
Blood sucking insect
Malarial parasites Leishmania Trypanosomes Filariae Viruses Rickettsia Bacteria Spirochetes
Direct source with the hydatid cyst of Echinococcus granulosus and visceral larva migrans dt Toxocara canis
Doggie
Parasite: herbivores
Trichostrongylus spp.
Parasite: cats
Toxoplasma spp.
Parasite: rats
Hymenolepis nana
Another person, his clothing, bedding, or immediate environment that he has contaminated, food handlers
Entamoeba histolytica
Enterobius vermicularis
Hymenolepis nana
What can cause autoinfection?
E. verm
H. nana
S. stercoralis
C. philippinensis
In taeniasis, human is considered as?
Definitive or final host
Intermediate host of Taenia spp and Schistosoma spp.
Taenia spp. - Pigs or cattle
Schistosoma spp. - Snails
One in wc the parasite doesn’t dev further to later stages
Paratenic host
The parasite remains alive and is able to infect another susceptible host
Paratenic host
What is an example of paratenic host?
Metacercariae of Paragonimus in raw wild boar meat can pass thru the intestinal wall of humans and complete its development
Wild boar is the paratenic host
What allows the parasite’s life cycle to continue and become additional sources of human infection?
Reservoir host
Pigs - B. coli
Field rats - P. westermani
Cats - B. malayi
In Falciparum malaria, possession of what confers some protection?
Sickle cell trait
What increases the susceptibility of an individual to Plasmodium vivax infections?
Presence of Duffy blood factor
What is not suitable for the development of intestinal protozoans?
Diet rich in protein
What favors the appearance of symptoms of amoebiasis and complications of the dse of high carb diet - favors the development of some tapeworms?
Low protein diet
What may be v impt in modifying the severity of dse in endemic areas?
Acquired immunity
What are the mechanisms by which parasites cause injury to the host?
(1) Interference with the vital processes of the host through enz sys
(2) Invasion and destruction of host tissue
(3) Deprivation of the hosts from essential nutrients and substances
What allows the parasites to metabolize nutrients obtained from the host and store these for energy?
Secretory and excretory products
What parasite secretes cysteine proteinases wc digest cellular materials and degrade epithelial basement?
Trophozoites of E. histolytica
What invades RBCs, and after multiplication, the host’s rbc rupture resulting in the release of merozoites?
Plasmodium
What is the cumulative deposition of eggs in the liver that stimulates an immune response resulting in granuloma formation and then fibrosis wc leads to portal HPN and massive hemorrhage in the venules?
Schistosoma japonicum
They have cutting plates wc cab attach to the intestinal mucosa and destroy the villi
Hookworms
Form tangled masses that can lead to intestinal obstruction and may invade other organs like appendix and bile ducts
Ascaris
What can cause massive intestinal bleeding wc results in chronic bld loss and IDA?
Heavy hookworm infxn
What parasite competes w its host for available supply of vit B12 that leads to Megaloblastic Anemia?
D. latum
What makes the helminthic parasites resistant to cytotoxic effects of both neutrophils and macrophages?
Their cuticle and integument
What can destroy non-human trypanosomes except Trypanosoma brucei wc has evolved resistance thru expression of serum resistance-associated protein?
Trypanolytic factors s/a apolipoprotein L-1 (APOL1)
What enables a non-human trypanosome (T. evansi) to infect human, and addition of recombinant APOL1 restored tryoanolytic activity?
A frameshift mutation in the APOL1 gene
What are parasites that enter the bld stream or tissue that often able to survive and replicate bcs they’re resistant to the host innate immune response?
Protozoa and helminthic parasites
What reduce the immune fxn of macrophages that lower their capacity of phagocytosis?
Also cause the defective processing of antigen
(Immune suppression)
Plasmodium spp.
What can produce large amounts of surface glycoproteins?
Immune suppression
Trypanomastigotes
Trypanosoma gambiense; this will affect the processing of the proteins dt antongenic competition and impair the B and T lymphocyte activity causing them to:
(Immune suppression)
Decrease lymphokines and immunoglobulin production
What parasite produces suppressor factor that can inhibit movement of monocytes to the site of invasion?
(Immune suppression)
Entamoeba histolytica
Down-regulation of lymphocytes
Immune suppression
Fasciola spp.
Polyclonal hypergammaglobulinemia where Ab lack specificity against these parasites
(Immune suppression)
W. bancrofti
B. malayi
Plasmodium spp.
Immune response is directed against the deeper layers of the cuticle but the immune response is diverted to the rapidly changing surface of its integument
(Immune suppression)
Necator americanus
Immune complexes produced in cysticercus cellulosae infxn supress inflammatory response thru inhibition of complement activity
(Immune suppression)
Plasmodium spp.
T. cruzi
Schistosoma spp.
Antigenic variation
Trypanosoma gambiense and Giardia lamblia
Plasmodium falciparum
Parasites changes the antigenic profile off its surface coat –> variant surface glycoproteins (SVG)
(Antigenic variation)
Trypanosoma gambiense and Giardia lamblia
They exhibit antigenic diversity
Antigenic variation
P. falciparum
Mechanism is thru repeat variation of the encoded polypeptides wc contain tandem sequences of amino acids as observed in:
• MSA - Merozoites surface ag
• RESA - Ring infected rbc surface ag
(Antigenic variation)
P. falciparum
These repeat sequences are Ag-ic epitopes, wc stimulate Ab prod.
With variation, Ab fail to recognize the Ag
(Antigenic variation)
P. falciparum
These can acquire antigenic mol from the host (host mimicry)
Larval stage of Echinococcus granulosus (hydatid cyst)
Tegument of Schistosoma spp. adult
Ab produced against the parasite fail to recognize nonself from self Ag
Host mimicry
This saves the parasite from splenic filtration and the action of Ab
Intracellular sequestration
Proliferate inside macrophages to escape the host immune response
(Intracellular sequestration)
T. cruzi
Leishmania spp.
T. gondii - also in other nucleated cells
Sequestered from the circulation into the deep vasculature
P. falciparum (late intracellular stages)
Mediated by the presence of knobs on infected rbc that enable them to be attached to the endothelial cells of tiny capillaries
P. falciparum (late intracellular stages)
Its muscle arrangement is polymarian (numerous cells project well into the body cavity)
A. lumbricoides
Its color is whitish or pinkish
And has a length of:
10-30cm (male)
22-35cm (female)
A. lumbricoides
Parts: terminal mouth, 3 lips, sensory papillae