chp 5 & 25 helminths

Major Group of Parasitic Helminths part 2

Roundworms - Phylum Nematoda (nematodes) - round, a complete digestive tract, a protective surface cuticle, spines and hooks on mouth; excretory and nervous systems poorly developed

Blood Flukes: Schistosomes (Cycle D)

Schistosomiasis - prominent parasitic disease •Schistosoma mansoni, S. japonicum, S. haematobium •Adult flukes live in humans who release eggs into water; early larva (miracidium) develops in freshwater snail into a 2nd larva (cercaria) •Larva penetrates human skin and matures into the liver; adults migrate to intestine or bladder and shed eggs (chronic organ enlargement) chronic infection from water, ongoing 90% cases in Africa male and female stay together once mate

tapeworm (Cestode) parts

scolex : suckers on worms (heads with hooks) grips the intestines proglottid : fertile eggs (ribbon like bodies composed of sacs) each proglottid is independent unit adapted to absorbing food, making/releasing eggs

Dracunculus medinensis and Dracontiasis part 2

screens in water filter out cyclops tie worm to end of stick (process to get out) infection may occur If stick or worm breaks

Arthropod Vectors: Lice Insects

small, soft; attach to head and body hair feeding inconspicuously on blood and tissue fluid Release feces that contaminate wound; epidemic typhus, relapsing fever

trichenalla spiralis

trichina worm life cycle requirement - pigs/mammals spread to humans by - consumption of meat containing larvae affects - skin dermatitis muscle/nervous (encephalitis) gastrointestinal distress

Trichinella spiralis and Trichinellosis part 1

1)Larvae encysted in animal muscle are the infective stage. 2)When ingested, cysts hatch and mature in the intestinal lining. 3)Adults reproduce and form new larvae. These burrow through the intestine and enter the circulation. 4)Larvae eventually form cysts in skeletal muscle that can remain for years. Circle shows a biopsy of human skeletal muscle infected with the coiled larvae of Trichinella spiralis.

Trichinella spiralis and Trichinellosis part 2

40% routine autopsies in 1950's had these worms in muscle tissue - chronic pain from eating undercooked pork not a concern once pigs were no longer fed trash issue in Alaska

Trematodes life cycle

5 larval stages ciliated miricidium sporocyst and redials - reproductive cercaria- motile stage, fork tail that burrows loses tail to become metacercaria

Ascaris lumbricoides life cycle part 1

Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks

Ascaris lumbricoides life cycle part 4

Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

Helminth Classification and Identification

Classify according to •shape, •size, •organ development, •presence of hooks, suckers, or other special structures, •mode of reproduction, •hosts, and •appearance of eggs and larvae Identify by microscopic detection of worm, larvae, or eggs

Taenia solium with cysticercosis life cycle part 3

Cysts evaginate and attach to the small intestine by their scolex Adult tapeworms develop, (up to 2 to 7 m in length and produce less than 1000 proglottids, each with approximately 50,000 eggs) and reside in the small intestine for years

Schistosoma life cycle part 1

Eggs are eliminated with feces or urine Under optimal conditions the eggs hatch and release miracidia which swim and penetrate specific snail intermediate hosts The stages in the snail include 2 generations of sporocysts

Major Group of Parasitic Helminths part 1

Flatworms - Phylum Platyhelminthes - flat, no definite body cavity; digestive tract a blind pouch; simple excretory and nervous systems •Cestodes (tapeworms) •Trematodes or flukes, are flattened, nonsegmentedworms, often leaf shaped, with sucking mouthparts

Schistosoma life cycle part 3

For instance, S. japonicum is more frequently found in the superior mesenteric veins draining the small intestine S. mansoni occurs more often in the superior mesenteric veins draining the large intestine However, both species can occupy either location, and they are capable of moving between sites, so it is not possible to state unequivocally that one species only occurs in one location. S. haematobium most often occurs in the venous plexus of bladder but it can also be found in the rectal venules.

Necator americanus life cycle part 1

Hookworm that burrows in skin! Eggs are passed in the stool and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective

Taenia solium with cysticercosis life cycle part 2

Once eggs are ingested, oncospheres hatch in the intestine 3, 8 invade the intestinal wall, and migrate to striated muscles, as well as the brain, liver, and other tissues, where they develop into cysticerci. In humans, cysts can cause serious sequellae if they localize in the brain, resulting in neurocysticercosis. The parasite life cycle is completed, resulting in human tapeworm infection, when humans ingest undercooked pork containing cysticerci

Lung Flukes (Cycle D)

Paragonimus westermani - •cycles between carnivorous animals, snails, and crustaceans; humans infected by eating undercooked crustaceans; intestinal worms migrate to lungs

Taenia solium with cysticercosis life cycle part 1

Pigs and humans become infected by ingesting eggs or gravid proglottids 2/7 . Humans are infected either by ingestion of food contaminated with feces, or by autoinfection. In the latter case, a human infected with adult T. solium can ingest eggs produced by that tapeworm, through fecal contamination.

Taenia solium

Pork tapeworm, fecal/oral •Infects humans through ingesting cysticerci (encysted larvae) or eggs •In cysticercosis, eggs hatch in intestine, releasing tapeworm larva that migrate to all tissues and encyst •Most damaging if they lodge in the heart, eye, or brain •May cause seizures, psychiatric disturbances leading cause of epilepsy in world in US and Mexico very severe & hard to treat

Cestode (Tapeworm) Infestations

Principal causes of of human taeniasis: •Taenia saginata - beef tapeworm Taenia solium - pork tapeworm

Schistosoma life cycle part 4

The females (size 7 to 20 mm; males slightly smaller) deposit eggs in the small venules of the portal and perivesical systems. The eggs are moved progressively toward the lumen of the intestine (S. mansoniand S. japonicum) and of the bladder and ureters (S. haematobium), and are eliminated with feces or urine, respectively

Ascaris lumbricoides life cycle part 3

The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed Upon reaching the small intestine, they develop into adult worms

Necator americanus life cycle part 3

The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years. CDC.gov

Necator americanus life cycle part 2

These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed

Arthropod Vectors: Arachnids

Ticks - cling on vegetation and attach to host on contact; larvae, nymph, and adults get blood meal by piercing skin of host •Hard or ixodid ticks - small compact, rigid bodies; transmit bacterial (Lyme Disease - Borrelia burgdorferi), rickettsial (Rocky Mountain Spotted Fever - Rickettsia ricketsii), viral diseases •Soft or argasid ticks - flexible outer bodies; transmit relapsing fever

Liver Flukes (Cycle D) part 1

Trematodes of zoonotic origin •Opisthorchis (Clonorchis) sinensis Cycles between mammals and snails and fish Humans are infected by eating inadequately cooked fish containing cercariae Larvae crawl into bile duct, mature, and shed eggs into feces; snail are infected

Schistosoma life cycle part 2

and the production of cercariae Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host and shed their forked tail, becoming schistosomulae (metacercaria) The schistosomulae migrate through several tissues and stages to their residence in the veins Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species

Ascaris lumbricoides

ascariasis life cycle requires - humans spread to humans by - fecal pollution of soil with eggs affects : gastrointestinal (intestinal organs)

Arthropod Vectors: Mosquito Insects

require an aquatic habitat Females take blood meal transmitting disease: malaria - Plasmodium, filariasis, Dengue Yellow fever

Schistosoma japonicum

blood fluke life cycle requirement - humans & snails spread to humans by - ingestion of fresh water containing larval stage

parasitology (study of eukaryotic parasites)

cause 20% of infectious diseases less prevalent in industrialized countries (US & Europe) common among HIV people and immunocompromised •Correlation between parasites and limited autoimmune disorders such as Multiple Sclerosis, Rheumatoid Arthritis, Crohn's Disease, IBS •Parasites do not usually kill their host but are responsible for chronic mild to debilitating disease

schistosoma spp.

causes blood infection (cardiovascular) cough (respiratory) intestinal schistosomiasis (gastrointestinal) urinary schistosomiasis (urogenital)

Ascaris lumbricoides life cycle part 2

depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed the larvae hatch invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs

Enterobius vermicularis & Pinworm Infection part 2

fecal oral route can be inhaled most common helminth infection in US

Cercarial Dermatitis - "Swimmer's Itch" - Schistosoma sp.

found in colder lakes (shallow water) eggs are passed in feces eggs hatch and release miracidia parasite develops in a molluscan intermediate host cercariae penetrates skin of birds and migrate to blood vessels humans are exposed to the dermatitis producing cercariae

Arthropod Vectors: Flea Insects

highly motile, flattened bodies; feed on warm-blooded animals Carry zoonotic diseases: plague - Yersinia pestis, murine typhus

Taenia saginata life cycle

human ingests encysted larva cysticercus in beef muscle (undercooked pork) as intermediate host scolex attaches to intestines and grows with proglottid gravid full of eggs pig ingests the egg easier to control/treat by cooking meat not as severe

Ascaris lumbricoides and Ascariasis part 1

large intestinal roundworm •Most cases in the U.S. occur in the southeastern states •Indigenous to humans •Ascaris spends its larval and adult stages in humans; release embryonic eggs in feces, and are spread to other humans; food, drink, or contaminated objects •Ingested eggs hatch into larvae and burrow through the intestine into circulation and travel to the lungs and pharynx and are swallowed •Adult worms complete cycle in intestines and reproduce - 200,000 eggs/day

parasitic helminths

multicellular eukaryotic heterotrophic animals that have organs for - reproduction, movement, protection have mouthparts for attachment to & for digestion of host tissues well developed sex organs to produce eggs/sperm for adults (produce many offspring) separate sexes or hermaphrodatic (both sexes in one) fertile eggs go thru larval period in or out of host

Necator americanus

new world hookworm life cycle requirement - humans spread to humans by - fecal pollution of soil with eggs affects - skin (dermatitis) gastrointestinal distress respiratory - pneumonitis

Clonorchis sinensis

occurs when people eat undercooked freshwater fish (trout) present in salt fish, ceviche form of fish, pickled fish, dry fish eggs do not die off in cooking

Enteriobius vermicularis

pinworm life cycle requirement - humans spread to humans by - close contact & fomites affects - anal itching (skin) gastrointestinal diarrhea

taenia solium

pork tapeworm (cestode) life cycle requirement - humans & swines spread to humans by - ingestion of undercooked/raw pork affects - cysticercosis (nervous/muscle/cardiovascular) gastrointestinal distress

Trematodes part 2

primitive parasites phylum Platyhelminthes fecal oral oral/ventral sucker to help them stick to surfaces snails are used as intermediate host (also fish)

Trichinella spiralis and Trichinellosis part 3

•Acquired from eating undercooked pork or bear meat •Larvae migrate from intestine to blood vessels, muscle, heart, and brain, where it forms cysts •First symptoms - flulike, diarrhea •Second symptoms - muscle and joint pain, shortness of breath, pronounced eosinophilia •No cure after larva have encysted

parasite characteristics

•Adulthood and mating occur in the definitive or primaryhost •Larval develop occurs in the intermediate or secondaryhost

Taenia saginata part 2

•Animals are infected by grazing on land contaminated with human feces •Infection occurs from eating raw beef in which the larval form has encysted •In humans, larva attaches to the small intestine and becomes an adult •Causes few symptoms; vague abdominal pain and nausea; proglottids in stool

Distribution and Importance of Parasitic Worms

•Approximately 50 species parasitize humans •Distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics •Acquired through ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors •Afflict billions of humans

Taenia saginata part 1

•Beef tapeworm •Very large, up to 2,000 proglottids •Humans are the definitive host Taenia solium tapeworm scolex has 4 suckers and 2 rows of hooklets. the remainder of the tape, called the strobila, has a total length of 5 meters.

Hookworms part 1

•Characteristic curved ends and hooked mouths •Necator americanus and Ancylostoma duodenale •Humans shed eggs in feces, which hatch into filariform larvae and burrow into the skin of bare feet

Tissue Nematodes

•Complete their life cycle in human blood, lymphatics, or skin •Filarial worms; elongate, filamentous bodies, spread by biting arthropods •Cause filariasis, a chronic, deforming disease •The species responsible for most filariases are •Wuchereria bancrofti - elephantiasis (not really reduced) •Onchocerca volvulus - river blindness (greatly reduced) •Loa loa - eye worm (has been reduced)

Dracunculus medinensis and Dracontiasis part 1

•Dracontiasis, caused by the guinea worm, affects residents of India, the Middle East, and Central Africa. •The parasite is carried by Cyclops, a microscopic arthropod commonly found in still water •After ingesting water from a contaminated water source, the larvae are freed from their Cyclops host and penetrate intosubcutaneous tissues of the intestine, where they form highly irritating lesions •After efforts from WHO and Carter Foundation, cases have dropped from 3.5 million in 1986 to 24 cases in 2015 and will soon be eliminated from the earth

Enterobius vermicularis & Pinworm Infection part 1

•Enterobiasis most common worm disease of children in temperate zones •Eggs are picked up from surroundings and swallowed •After hatching in the small intestine, they develop into adults •Anal itching occurs when mature females emerge from intestine to release eggs •Self-inoculation is common •Tape test (put a piece of tape on anus at night, to see worm stuck with eggs)

Liver Flukes (Cycle D) part 2

•Fasciola hepatica Cycles between herbivores, snails, and aquatic plants Humans are infected by eating raw aquatic plants; fluke lodges in liver

Trematodes part 1

•Flatworms with ovoid leaflike bodies (parasites) •Have digestive, excretory, neuromuscular, and reproductive systems •Lack circulatory and respiratory systems •Animals such as snails or fish are usually the intermediate hosts and humans are the definitive hosts primitive, phylum Platyhelminthes, fecal oral

Hookworms part 2

•Larvae travel from blood to lungs, proceed up bronchi and throat and are swallowed •Worms mature and reproduce in small intestine and complete the cycle •May cause pneumonia, nausea, vomiting, cramps, and bloody diarrhea Blood loss is significant - anemia

nematode roundworm infestations part 1

•Most abundant animal groups •The vast majority are free- living soil and freshwater worms, but around 200 are parasitic (50 species affect humans) •Elongated, cylindrical worms with protective cuticles, circular muscles, a complete digestive tract, and separate sexes

nematode roundworm infestations part 2

•The human parasites divided into: •Intestinal nematodes: develop to some degree in the intestine Ascaris, Strongyloides, and hookworms (Necator)

Strongyloides stercoralis and Strongyloidiasis

•Threadworm •Tiny roundworms completes life cycle in humans or moist soil •Larvae penetrate skin and migrate to lungs, are swallowed, and complete development in the intestine •Can reinfect the same host without leaving the body •Heavy worm loads can cause pneumonitis and eosinophilia, bloody diarrhea, liver enlargement, bowel obstruction, and malabsorption

Onchocerca volvulus and River Blindness

•Transmitted by biting black flies •Larvae develop into adults in subcutaneous tissues •Adult females migrate via the blood to the eyes, provoking inflammatory reactions •Coinfection with Wolbachia bacteria causes river blindness Treatment: tetracycline andivermectin

Wucherereia bancrofti and Bancroftian Filariasis

•Tropical infection spread by mosquitoes •Vector deposits larvae which move into lymphatics and develop into adults •Chronic infection causes blockage of lymphatic circulation and elephantiasis (symptom, hard to treat unless early on) massive swelling in the extremities

Ascaris lumbricoides and Ascariasis part 2

•Worms retain motility, do not attach •Severe inflammatory reactions mark the migratory route •Allergic reactions can occur •Heavy worm loads can retard physical and mental development 25% infected a lot of contamination fecal oral route (BAD hand washing)