Parasitic Pathogens
Cysticercosis (________infection of tissues) is more difficult to treat than taeniasis (intestinal _______infection).... talking about ____________
larva; adult; tapeworms
Helminths: Routes of Transmission: injected by blood-sucking insect
larval stages develop to infectivity in insect intermediate host
Helminths: Routes of Transmission: active skin penetration
larval stages invade through the skin
Protozoa Infections: Blood
malaria (Plasmodium)*; trypanosomes
Plasmodium causes
malaria*** IMP (malaria occurs in blood & CNS)
protozoa: male vs female
male: produces the small gamete (microgamete); female produces large gamete (macrogamete)
asexual reproduction
merozoite--schizont--merozoites (so the haploid merozoite becomes a schizont (where you have a bunch of nuclei replicated and then 1 cytoplasmic segmentation leading to a bunch of new haploid merozoites)
Occurrence of Protozoa infections
most are pathogenic in the very young and the immunocompromised
Arthropods Eat You from outside
mostly insects and arachnids; ectoparasites; disease VECTORS. 1) biological vector: a host in the life cycle of the parasite, ex. anopheles mosquito carrying Plasmodium species. 2) mechanical vector: ex. house flies carrying Salmonella.
Schizogony
multiple mitosis of nuclei followed by cytoplasmic segmentation: 1 to many
Protozoa: general characteristics
non-photosynthetic, unicellular, motile eukaryotes
tapeworm intermediate host (so tapeworms do need an intermediate host)
pig/cow
4 major types of sporozoa
plasmodium, toxoplasma, cryptosporidium, babesia
parasites are more common in children due to
poor hygiene habits
Amoebae (rhizopods)
pseudopods to move
Reproduction of Helminths: Nematodes (round worms)
separate sexes, female larger than male
hookworms can enter thru the
skin
helminth: trematode: blood fluke: intermediate host
snail
Helminths suppress immunity
some worms (ex. schistosomes) acquire host molecules as camouflage. others release copious soluble antigens as smog to divert immune responses (Ab will chase the soluble antigens). Helminth immunosuppressive therapy is being pursued for autoimmune & allergic diseases from asthma, Crohn's disease, multiple sclerosis, to atherosclerosis.
infective stage of malaria is when
the sporozoites are injected into the human by mosquito; diagnostic stage when immature tropozoite and mature tropozoite and schizont and gametocytes in human blood
Toxoplasma causes
toxoplasmosis (mainly in fetus & AIDS); pregnant women should avoid cats or can get toxoplasma (toxoplasma occurs in CNS)
you find trichomonas in the
urogenital tract
Sexual reproduction
via conjugation (get together really close, build channel, exchange micronuclei/genetic info/HOMOSEXUAL whereas bacterial conjugation was heterosexual; happens b/w 2 adults) or gametogenesis (form gametes that unite; haploid-->dipoid; union of 2 gametes)
blood fluke: 2 hosts (a type of Trematode which is a type of Helminth)
wants us to know concepts of miracidia that enter the snails and cercariae that enter the human
sexual reproduction
gametocytes (male and female haploid gametocytes)--oocyst (diploid)--sporozoites (haploid; when you rupture the oocyst & release a bunch of sporozoites)
Helminths: Cestode: Tapeworm: Cysticerci
google definition: The larval form of certain Taenia species, typically found in muscles of mammalian intermediate hosts that serve as a prey of various predators; it consists of a fluid-filled bladder in which the invaginated cestode scolex develops. (so the pig/cow has this when the oncospheres hatch and circulate to their muscles)
merozoites***
haploid; in the human for malaria; (a sporozoan tropozoite produced by schizogony that's capable of initiating a new sexual or asexual cycle of development-- so sporozoan= intracellular parasite w/ no motility organelle & tropozoite= growing stage for sporozoan parasites and then schizogony is asexual reproduction where you get a lot of mitosis of nuclei and then 1 cytoplasmic segmentation so you go from 1 to many--looks like they kinda just burst out at the end)
Trichomoniasis
has to be directly transmitted from person to person because it has no cyst stage to survive in the environment
general characteristics of parasitic worms
well developed reproductive system; an adult Ascaris* female can produce 200,000 eggs per day, but none would hatch in the same host (egg must infect a new host*). Most worms don't finish a replication cycle inside 1 human host. They can't multiply in the same host (macroparasites)
Kingdom Protista
Unicellular eukaryotes; classified based on means of motility; 4 categories based on movement (stay tuned fam)
Protozoa Infections: intestine
Cryptosporidium, Entamoeba, giardia, cyclospora, microsporidia
Cysticercosis (googled)
Cysticercosis is an infection caused by the larvae of the parasite Taenia solium or Taenia saginata (so pig/cow gets this when it eats human poop w/ these larvae in it)
Transmission of Protozoa: Sexual
**Trichomonas trophozoite (do not form cysts; do not survive outside of the body)
Transmission of Protozoa: fecal-oral
**cysts of Entamoeba, Giardia, Toxoplasma (need cyst to survive the acid in the stomach)
most helminths cannot finish life cycle in
1 host
how helminths cause disease
1) intestinal infections are most common: adults of nematodes (roundworm) & cestodes (tapeworm). 2) tissue infections (harder to treat than intestinal infections): larva of nematodes and cestodes; many adult trematodes (flukes)
2 stages in life cycle of protozoa
1) trophozoite: feeding & dividing stage (active/reproducing) 2) Cyst: dormant but infectious stage (it's how they survive outside the host in a dry environment)
insect has
6 legs, 2 wings
arachnid has
8 legs, no wings
helminth: trematode: blood fluke: cercariae
A free-swimming stage in the development of a fluke or trematode. Cercariae develop within sporocysts or rediae that parasitize snails or bivalve mollusks. They emerge from the mollusk and either enter their final host directly (in the case of the blood fluke) or encyst in an intermediate host that is ingested by the final host. In the latter case, the encysted tailless form is known as a metacercaria. (this is in the case of the liver fluke--NEXT!)
Pathogenic Protozoa: Ciliates
Balantidium coli* is the only known human pathogen, causing diarrhea. others are free living, such as paramecium
Parasitic amoeba
E. histolytica; naegleria
Tapeworm cycle-don't memorize
Eggs or gravid proglottids in the feces (from human) gets passed into the environment--> cattle & pigs become infected by ingesting vegetation contaminated by eggs or gravid proglottids. --> oncospheres hatch & penetrate intestinal wall, and circulate to musculature --> oncospheres develop into cysticerci** in muscle (so larvae exists in muscles of the pig/cow & will stay there even ifyou kill it) --> then human gets infected by ingesting raw or undercooked infected meat --> scolex (head of the cestode) attaches to the instestine --> become adults in the small intestine (human=definitive host)
helminth: trematode: liver fluke--REQUIRES 2 INTERMEDIATE HOSTS (big pic from google)
Embryonated eggs are discharged in the biliary ducts and in the stool . Eggs are ingested by a suitable snail intermediate host . Each egg releases a miracidia , which go through several developmental stages (sporocysts , rediae , and cercariae . The cercariae are released from the snail and after a short period of free-swimming time in water, they come in contact and penetrate the flesh of freshwater fish, where they encyst as metacercariae Infection of humans occurs by ingestion of undercooked, salted, pickled, or smoked freshwater fish . After ingestion, the metacercariae excyst in the duodenum and ascend the biliary tract through the ampulla of Vater Maturation takes approximately 1 month. The adult flukes (measuring 10 to 25 mm by 3 to 5 mm) reside in small and medium sized biliary ducts. In addition to humans, carnivorous animals can serve as reservoir hosts.
Amoebiases (amebic dysentery)
Entamoeba histolytica* w/ trophozoite and cyst stages (Google.. amoebiases= parasitic infection of the colon w/ this amoeba)
Protozoa Infections: liver
Entamoeba, Leishmania
Helminths: Tissue infection by adult nematodes (roundworms): lymph infection (elephantitis where lymph vessels are block-big legs); mosquito-borne
Filaria
Protozoa Infections: skin
Leishmania
helminth: trematode: liver fluke: he wants us to just know concepts of miracidia, cercaria, and metacercaria
Miracidia: The ciliated free-swimming larva of a digenetic fluke. On emerging from an ovum, it penetrates a snail of a particular species and metamorphoses into a sporocyst (asexual reprod. then goes to rediae then cercariae) Cercariae: A free-swimming stage in the development of a fluke or trematode. Cercariae develop within sporocysts or rediae that parasitize snails or bivalve mollusks. They emerge from the mollusk and either enter their final host directly (blood fluke, not liver) or encyst in an intermediate host that is ingested by the final host.(liver flukes do this) In the latter case, the encysted tailless form is known as a metacercaria. Metacercaria: : a tailless encysted late larva of a digenetic trematode that is usually the form which is infective for the definitive host
Transmission of Protozoa: Insects
Mosquito (Plasmodium*), sand fly (Leishmania), Reduviid bug & Tsetse fly (Trypanosoma)
malaria: protozoa that can do sexual & asexual reproduction
Mosquito takes a blood meal from human & injects sporozoites that go to human liver cell/infect it & form a schizont that then ruptures. (Exo-erythrocytic cycle) The haploid merozoites can then enter the human blood stages: erythryocytic cycle is when an immature trophozoite (ring stage) matures into trophozoite, forms schizont, and ruptures to make merozoites (cycle can keep going to make more). Other cycle from human blood is when immature trophozoite becomes gametocytes (make the 2 gametes by mitosis) that can then be given back to mosquito if human bit again. Now in the mosquito stages which is the sporogonic cycle. Mosquito sucks in both gametocytes- then microgamete (male) enters macrogamete (female) to form oocyst --> meiosis --> oocyst ruptures and releases sporozoites in the mosquito.
Amebic meningoencephalitis caused by
Naegleria (brain-eating amoeba) and Acanthamoeba
Helminths: round worms are in what phylum
Phylum Nematoda
Parasitic sporozoa:
Plasmodium, Toxoplasma, Cryptosporidium, Babesia, etc
Helminths: flat worms are in Phylum
Platyhelmintha
mite
Sarcoptes scabiei: causes scabies; microscopic. infected until treated-stays on skin
Malaria overview
So basically asexual reproduction in the human blood stages (human = intermediate host) and sexual reproduction in the mosquito stages (mosquito = definitive host)
Tapeworms: adult in human intestine and larvae in animal muscles (tapeworm= a cestode= a type of helminth)
Students do not have to memorize the contents of the figure, except for the fact that animals eat the eggs to develop cysticercosis while humans eat cysticerci in animal meat and develop taeniasis (adult in the intestine). A scolex is the head of a cestode.
Helminths: cestode: tapeworm: taenisis
Taeniasis in humans is a parasitic infection caused by the tapeworm species Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Taenia asiatica (Asian tapeworm). Humans can become infected with these tapeworms by eating raw or undercooked beef (T. saginata) or pork (T. solium and T. asiatica). People with taeniasis may not know they have a tapeworm infection because symptoms are usually mild or nonexistent. (so once the human eats the undercooked meat, the scolex (head) of tapeworm attaches to intestine and turns into adult/gives the human Taenia)
helminth: trematode: blood fluke: miracidia
The ciliated free-swimming larva of a digenetic fluke. On emerging from an ovum, it penetrates a snail of a particular species and metamorphoses into a sporocyst (so basically eggs hatch releasing miracidia which penetrate snail tissue then have asexual reproduction/sporocysts in the snail which turn into cercariae (released by snail into water and free swimming) which penetrate skin of person
malaria: protozoa that can do sexual & asexual reproduction
The malaria parasite life cycle involves two hosts. During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host . Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites . (Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.) After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony ). Merozoites infect red blood cells . The ring stage trophozoites mature into schizonts, which rupture releasing merozoites . Some parasites differentiate into sexual erythrocytic stages (gametocytes) . Blood stage parasites are responsible for the clinical manifestations of the disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal . The parasites' multiplication in the mosquito is known as the sporogonic cycle . While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes . The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts . The oocysts grow, rupture, and release sporozoites, which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle.
Helminths: Tissue infection by adult nematodes (roundworms): natural host is dog; causes eye infection, etc.
Toxocara canis
Helminths: Tissue infection by adult nematodes (roundworms): muscle infection; natural hosts are pigs, etc.
Trichinella spiralis
Protozoa Infections: urinogenital tract
Trichomonas (vagina)
Pathogenic Protozoa: Flagelletes: Trichomoniasis*
Trichomonas vaginalis causes trichomoniasis*; no cyst stage (so must transfer from 1 host to another directly/can't survive outside host); most common pathogenic protozoa flagelleta; also infects males but no symptoms for them; if female has- you treat the husband & wife
Pathogenic flagellates
Trichomonas, Giardia, Trypanosoma, leishmania, etc
microparasite
a parasite that can multiply in 1 host
macroparasite
a parasite that can't multiply in 1 host
Helminths: Routes of Transmission: fecal-oral route
accidental ingestion of eggs or larvae originating from feces of infected host
Helminths: Routes of Transmission: via intermediate host
accidental ingestion of larvae in tissue of another host ex. pig
for protozoa:
adult means sexual reproduction (with fertilization & meiosis)
plasmodium
always inside RBCs (sporozoa causing malaria)
Protozoa Infections: CNS
amebae, malaria, Toxoplasma, trypanosomes
for protozoa: larva means ________________ reproduction
asexual (b/c larva is the intermediate host)
most protozoa replicate ______________________ in humans
asexually
Babesia causes
babesiosis (Google: Babesia infect & destroy RBCs so babesiosis can cause hemolytic anemia)
hermaphrodite
both male and female in the same body; point of a hermaphrodite is if NO partner-->can still fertilize/reproduce. If partner, then they will still exchange I think
in humans, ameba
bury into the intestinal mucosa and feed on RBCs (in humans)
mosquito
can see w/ naked eye. wont stay on skin for long bc dangerous to them
biological vector
carries inside; parasite has to multiply in the vector
mechanical vector
carries outside of the insect
Pathogenic Protozoa: Hemoflagellates: Trypanosoma brucei*
causes African trypanosomiasis (sleeping sickness) (google: given by tsetse fly bites: starts w/ fever, headache, joint pain, itching..later confusion, poor coordination, behavior changes)
Pathogenic Protozoa: Hemoflagellates: Trypanosoma cruzi*
causes American trypanosomiasis (Chagas disease) (google: can be mild w just swelling/fever or can be long lasting. if untreated, can cause congestive heart failure)
Pathogenic Protozoa: Flagelletes: Giardia lamblia*
causes diarrhea*; cysts survive for months in water*
Pathogenic Protozoa: Hemoflagellates: Leishmania
causes kala-azar (Leishmania spread by sandfly bites; google: affects spleen/liver/bone marrow)
protozoa: evading host immunity
cell membrane is target of immune cells & Abs. Repeated variation of surface antigens (done by Trypanosomes). Polymorphism of surface antigens (plasmodium). Consumption of complements (amoebae- done to avoid humoral immunity)
Ciliates have
cilia to move
Helminths: Platyhelmintha: 2 classes
class Trematoda (flukes); class cestode (tapeworms)
the insect is the ___________________ host
definitive
for most helminths, human serves as the _____________________ and occasionally as the intermediate host (in the case of ____________________ )
definitive host; Taenia solium (tapeworms)--this is just saying that even though human is definitive host by having the adult form in intestines and pooping it out, sometimes humans may accidentally eat food/water w/ the eggs... so then the cysticerci can lodge in human tissues such as the eyes, brain (causes neurocysticercosis), and muscle and the cysticerci are the larva form
Cryptosporidium causes
diarrhea (a main symptom of AIDS); cryptosporidium occurs in intestine
CAT scan of brain reveals a scolex. person prob got disease by
drinking water contaminated w/ fecal matter. (this is when the human can also be intermediate host in Taenia solium--> could cause neurocisticercosis if the cysticerci gets into the brain)*****
quick summary liver fluke (don't mem)
embryonated eggs passed in feces (from infected human)--> eggs ingested by snail --> miracidia --> asexual repro. --> sporocytes --> rediae --> cercariae --> free-swimming cercariae encyst in the skin or flesh of fresh water fish --> metacercariae in flesh or skin of fresh water fish are ingested by human host --> excyst in duodenum --> adults in bilary duct --> passed in feces back to beginning
Asexual reproduction
fission (1 divide into 2) or schizogony (1 parasite grows up & starts dividing its nuclei (NOT the cytoplasm)- end w/ huge cell w/ many nuclei- divide to become many protozoa... so nuclear division w/o cytokinesis until the very end)
Flagellates have
flagella to move
helminth: trematode: blood fluke: summary of cycle (don't have to memorize)
have eggs in feces & urine (came from human infected by blood fluke but cycle starting over) that get into the water--> eggs hatch releasing miracidia--> miracidia penetrate snail tissue--> sporocysts in snail (successive generations thru asexual reproduction)--> cercariae released by snail into water and free-swimming--> penetrates skin of human--> cercariae lose tails during penetration and become schistosomulae-->circulation-->migrate to portal blood in liver and mature into adults--> paired adult worms migrate to mesenteric venules of bowel/rectum to lay eggs that circulates to liver and shed in stools and goes to venous plexus of bladder to come out in urine
Reproduction of Helminths: trematodes (flukes)
hermaphrodites or separate sexes constantly in conjugation
Reproduction of Helminths: Cestodes (tapeworms)
hermaphrodites, both sexes per segment; each segment has testes & ovaries since hermaphrodites
cestodes and some trematodes are
hermaphroditic
definitive host
host where adult lives (does sexual repro.)
intermediate host
host where larva lives (does asexual repro.)
Trypanosoma
huge and outside RBCs
helminth: trematode: blood fluke: definitive host
human
tapeworm definitive host
human
liver fluke definitive & 2 intermediate hosts
human is definitive host ; snails and fish are intermediate hosts
Sporozoa are
immotile intracellular parasites that reproduces asexually by shizogony and sexually by gametogenesis
trophozoite
in the human for malaria; a growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host.
sporozoites
in the mosquito for malaria; a motile spore-like stage in the life cycle of some parasitic sporozoans (e.g., the malaria organism) that is typically the infective agent introduced into a host.
cysticeri are cestode larva in tissues of _________ hosts
intermediate
so the human is the ________________________ host
intermediate
Most nematodes need no _________________ host (nematode=type of helminth)
intermediate; eggs develop in the ENVIRONMENT, become infective, then hatch in the GI tract. so just need the 1 host. (eggs passed out in feces but need incubation in the environment for about 2 weeks b/c too hot in human for egg to become infectious but can in cooler environment)
most adult nematodes and cestodes live in
intestines
sporozoa
intracellular parasite, no motility organelle
Sporozoa
intracellular parasites, no motility organelle, also called Apicomplexa (IMMOTILE & ALWAYS INTRACELLULAR PARASITES)
Helminths: Classification
invertebrates in Kingdom anamalia
