symbiont organism that spends part of life cycle with another commensalism one benefits, no harm mutualism both symbionts are metabolically dependent upon each other parasitism one... symbiont organism that spends part of life cycle with another commensalism one benefits, no harm mutualism both symbionts are metabolically dependent upon each other parasitism one lives at the expense of the other parasite takes nourishment and needs through contact with another species host supports parasite medical parasitology in or on humans types of parasites ectoparasite outer surface of host lice, ticks, mites causes infestation endoparasite inside body of host causes infection obligate parasite requires host to survive and reproduce cant complete life cycle without host and dies facultative parasite doesnt absolutely depend on hosts can live as is erratic / aberrant parasite wanders to organs in which it is not usually found intermittent / temporary parasite only visits host for feeding spurious / coprozoic parasite doesnt cause harm as it only passes through the alimentary tract hyperparasite parasite that parasitizes other parasites pseudoparasite not really a parasite types of hosts definitive host harbors parasite in the adult or sexual stage intermediate host harbors larval or asexual stage of parasite can be many or none paratenic host vehicle to obligatory host not necessary for the life cycle reservoir host can harbor disease but asymptomatic natural host naturally infected with parasite accidental host not infected with parasite under normal circumstances types of life cycles monoxenous life cycle cycle in a single host species heterocenous life cycle require multiple host species direct life cycle does not require intermediate host indirect life cycle requires intermediate host effects of parasites on hosts direct effects mechanical injury pressure deleterious effect of toxic substances tissue damaging enzymes deprivation of nutrients, fluids, and metabolites competition of nutrients indirect effects excessive proliferation of certain tissues mode of transmission peroral ingestion of contaminated food and or water through nasal passage skin penetration transmitted by insect vectors vertical transmission or transplacental sexual intercourse air-borne transmission definition of terms infective stage stage where parasite is able to initiate infection diagnostic stage stage that exits definitive host clinical incubation period time between infection and evidence of symptoms biologic incubation period time between infection and acquisition of parasite autoinfection infected individual becomes his direct source of infection superinfection / hyperinfection infected again female adult worms can be oviparous or larviparous parthenogenesis egg can develop into embryo without fertilization by sperm immune response against parasites eosinophils bind to igEs on surface and cause antibody-dependent cell toxicity macrophage eats parasite and presents antigen to helper T cell that produces interleukin to activate b cells and make antibodies interleukin 4 naive t cells to t helper 2 cells increased gut motility and peristalsis interleukin 13 goblet hyperplasia mucus hypersecretion interleukin 5 increases production of eosinophils how parasites evade immune responses surface turnover shedding of surface antigens host mimicry covers themselves in host proteins antigenic variation change antigenic compositions resistance to intestinal enzymes cuticle covering of worms immune suppression suppressor factors that inhibit phagocytic movement intracellular sequestration pasa sa cells treatment deworming use of antihelminthic drugs cure rate previously positive to egg negative on samples egg reduction rate percentage fall in the egg counts on samples selective treatment individual level deworming targeted treatment group level deworming universal treatment population level preventive chemotherapy systematic large scale intervention of the govt classification of parasites protozoans can have locomotory apparatus nemahelminths nematodes or roundworms platyhelminths or flatworms cestoda are segmented tapeworms trematoda are unsegmented flukes arthropods Read more