Helminths- Intestinal

Nematodes or Roundworms Appearance/Anatomy:

Unsegmented (worms)= uniform in appearance -bilateral symmetry -fully functioning digestive tract (tube like terminates in anus) -thin, long, cylindrical, mm to meter in length -lack defined head, tapering anterior and posterior of body -NO body segments or suckers -few parthenogenic, most reproduce sexually with males -female: vagina, vulva, tube-like uteri, oviducts, and ovaries

ROUNDWORM- Nematode Enterobius vermicularis: PINWORM Distribution

Worldwide -frequent in school or preschool children -crowded conditions -more common in temperate than tropical countries -most common helminthic infection USA -direct life cycle, spread by fecal oral route

HOOKWORM- Nematode Strongyloides stercoralis Distribution:

Worldwide -tropical and subtropical -temperate (South of US) -rural areas, institutional settings, lower socioeconomic groups

ROUNDWORM- Nematode Ascaris lumbricoides: Distribution

Worldwide distribution -most common human helminthic infection -highest tropical & subtropical (temp + humidity) -areas with inadequate sanitation -rural areas of the SE-USA

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus Worldwide + Common + Found + Cycles

Worldwide- moist, warm climate -2nd most common human helminthic infection -both N. americanus and A. duodenale found in Africa, Asia, and Americas -N. americans predominates in Americas and Australia, while only A. duodenale is found in Middle East, North Africa, and southern Europe -Life cycles are identical

TAPEWORM- Cestode Diphyllobothrium latum Distribution:

"Giant Fish Tapeworm" -Distribution: fresh water -Northern Hemisphere (Europe, North America, Asia) -South America (Uruguay and Chile)

HOOKWORM- Nematode Strongyloides stercoralis Symptoms (Asymptomatic, Symptomatic, High burden):

-75% asymptomatic (low burden) -25% symptomatic: diarrhea, alternating with constipation, abdominal pain -Children: anorexia, chronic diarrhea, protein malabsorption, abdominal distension -Itching at site of filariform larvae penetration, "ground itch" most commonly on feet -Necrotizing bowel (high burden) -Pulmonary: Loeffler's syndrome during pulmonary migration of filariform larvae

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus Differentiation + Rarely

-CAN NOT differentiate species by ova examination -Adult worms rarely found in stool samples

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus ***Diagnostic and Infectious Stage:

-Diagnostic stage: Eggs in feces -Infectious stage: flariform larva penetrates skin

ROUNDWORM- Nematode Trichuris trichiura ***Diagnostic and Infectious Stage:

-Diagnostic stage: unembryonated eggs passed in feces -Infectious stage: Embryonated eggs are ingested

HOOKWORM- Nematode Strongyloides stercoralis Diagnostic stage + Infectious stage:

-Diagnostic: Rhabditiform larvae in intestine are excreted in stool -Infectious: Infective filariform larvae penetrate the intact skin initiating infection

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus Symptoms:

Iron deficiency anemia: blood loss at site of intestinal attachment of adult worms, especially if heavy burden -can be accompanied by cardiac complications GI and nutritional/metabolic symptoms "Ground itch" at site of filariform larvae penetration -cutaneous larva migrans -especially if NON- Human hookworm species (Canine hookworm) Respiratory symptoms observed during pulmonary migration of larvae Loeffler's syndrome- eosinophilic pneumonitis

Cestodes or Tapeworm Anatomy: BE FAMILIAR WITH TERMS OF ORGANISM

Lacks digestive tract, no mouth -nutrients absorbed through worm's cuticle (outer "skin") Proglottids, originate from neck region are immature, mature or gravid (full of eggs) -midventral genital and uterine pores, bilobed ovaries, strain specific egg morphology -some can produce 1 million eggs/day

HOOKWORM- Nematode Strongyloides stercoralis Adult Worm:

Adult worm- DIAGNOSTIC- LARVAE IN STOOL Rhabditiform larva -short buccal cavity -prominent, oval genital primordium, 1/3 distance from the tail Larvae can be in very low numbers- require repeated sample submission on successive days

HOOKWORM- Nematode Strongyloides stercoralis Symptoms (Dermatologic + Disseminated)

Dermatologic: urticarial rashes on buttocks + waist or chronic dermatitis at site of entry Disseminated -migration in skin, uticarial eruption- "larva currens" -abdomen, thighs -abdominal pain, distension shock, pulmonary and neurologic, septicemia, and potentially fatal -blood eosinophilia during acute + chronic stages

Adult Helminthic Replication Dioecious:

Male reproductive organs are in one individuals, and female reproductive organs are in another -reproduction occurs only when two adults of the opposite sex are present in the same host

Nematodes or Roundworms Inhabitant:

Inhabitant all habitats -deep sea to mountain tops

ROUNDWORM- Nematode Enterobius vermicularis: PINWORM ***Diagnostic and Infectious Stage:

-Infectious stage: Embryonated eggs ingested by human -Diagnostic stage: eggs on perianal folds, larvae inside the eggs mature within 4 to 6 hours

ROUNDWORM- Nematode Trichuris trichiura: WHIPWORM Symptom:

-Secrete a pore forming protein that play role in anemia and diarrhea, adult worms do not feed directly on blood or other host tissues -Frequently asymptomatic (low burden)

ROUNDWORM- Nematode Trichuris trichiura: WHIPWORM Worldwide

-Worldwide -3rd most common round worm of humans -increased numbers in areas with tropical weather and poor sanitation practices, and among children

ROUNDWORM- Nematode Ascaris lumbricoides: Migratory Phase of Infection (Lung)

-cough (produce worms), dyspnea, hemoptysis -Loeffler's syndrome: eosinophilic pneumonitis, resembles, asthma

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus What is filariform larvae?

-infective third stage larva of nematodes with penetrating larvae or with larvae that migrate through the body to reach intestine

ROUNDWORM- Nematode Ascaris lumbricoides: Symptoms

-low adult worm burden= asymptomatic -high burden (abdominal pain, obstruction) -HPA + Lung -Malnutrition and "failure to thrive" due to food absorption by worm

Cestodes or Tapeworms Hosts:

-mammals are definitive host with copepods or fish as intermediate hosts

ROUNDWORM- Nematode Enterobius vermicularis: PINWORM Symptoms

-most asymptomatic -intense itching perianal area, most commonly children -if abdominal pain or other gastrointestinal symptoms need to examine further for other GI pathogens

Helminths are (Multi + Possess + Living + Detection + Number + Resulting)

-multicellular eukaryotic animals -possess digestive, circulatory, nervous, excretory, and reproductive systems -free living in soil and water, whereas others are parasites of humans and other animals -diagnosed detection of eggs or larvae (immature forms) -eggs may have striations (lines), a spine, or an operculum (a hatch by which the larva leaves) -do not usually increase in number in host -disease resulting from mechanical damage, eating of host tissues, or competing for nutrients

Nematodes or Roundworms Larvae + Stages

-some larvae hatch in soil and actively penetrate skin of new hosts -once in body, travel a roundabout route to intestine -most are dioecious and develop through larval stages -adult, sexually mature stages are found only in definitive hosts with copulation of male and female worms leading fertilized egg production

ROUNDWORM- Nematode Trichuris trichiura: WHIPWORM Clinical disease mainly in

Children -bloody diarrhea, chronic colitis -Tenesmus: straining to deficate (long term leads to prolapse) -Heavy burden= chronic malnutrition, anemia, gastrointestinal problems, possible growth retardation/failure to thrive

Trematodes or Flukes (Worms + Fluke Meaning + Gut)

Flat worm with hooks (oral sucker), dorsoventrally flattened, all eggs are operculated Fluke= old English "floc" flatfish or flounder Gut or tissue flukes associated with foodborne infection -gut= intestinal fluke -liver/gall bladder= liver fluke -most commonly monoecious (hermaphroditic)

Trematodes or Flukes Anatomy + Distribution

Flat, leaf shaped worms -no anus and so is said to have an incomplete digestive tract -ventral sucker enables attachment to host tissues, from which position it can obtain nutrients Geographic distribution is limited by specific species of snails they require as intermediate hosts

ROUNDWORM- Nematode Ascaris lumbricoides: HPA

Hepatobiliary Ascariasis (HPA) -adult worm blocks biliary tract, hepatic abscess, appendicitis, blockage, secondary infections, death -common in children with large worm burden -adult worms wander, result of inadequate/incomplete drug treatment

Cestodes or Tapeworm Most + Pathogens BE FAMILIAR WITH TERMS OF ORGANISM

Most infected animals not humans Human pathogens: ribbon like, flat, body of segments/proglottid, contains both male and female reproductive systems, sucking groove, scolex allows for worm attachment to intestinal tissue

Adult Helminthic Replication Monoecious or hermaphroditic:

One worm has both male and female reproductive organs and may self fertilize -two hermaphrodites may copulate and simultaneously fertilize each other

ROUNDWORM- Nematode Trichuris trichiura Ova + Adult worm:

Ova -barrel shaped, thick shelled, polar "plugs" at each end -unembryonated when passed in stool Adult worm -males coiled posterior -females straight posterior -both have long, whip like anterior -adults reside in large intestine, cecum, and appendix of host

HOOKWORM- Nematode Ancylostoma duodenale + Necator americanus Ova + Adult worm:

Ova -oval, thin shelled, smooth, nonpigmented, and transparent Adult worm -upper intestine attached to mucosa by biting: "hooks" -differentiate species by mouth opening: A. duodenale- 2 pairs of teeth N. americanus- pair of cutting plates

ROUNDWORM- Ascaris lumbricoides Ova + Adult worm

Ova Fertilized - cleavage of internal yolk -yellow/brown, oval/spherical, thick, hyaline shell Unfertilized -difficult to recognize in stool: vegetable cell Adult -male worms smaller, curved tail, smooth without striations

ROUNDWORM- Nematode Enterobius vermicularis: PINWORM Ova + Adult worm:

Ova-collect early morning: tape prep -thin, smooth, transparent shell -oval and asymmetrical, flattened side -contains developed larva Adult worm -thin, flexible outer covering, fin-like expansion at anterior end, long pointed tail

Nematodes or Roundworms Tracts + Found + Strategies

Possess complete digestive tracts and have protective outer layer (cuticle) Found in almost all vertebrates including humans Multiple reproductive strategies: -shed eggs into the lumen of the intestine, eliminated with feces -eggs consumed by the host in contaminated food/drinking water

Trematodes or Flukes Acquired from:

Schistosoma acquired from contaminated fresh water exposure (snail intermediate host) pass through skin into blood= blood flukes -Dioecious, separate male and female

What is the only parasite that can undergo autoinfection?

Strongyloides stercoralis