Genus Echinococcus

 Genus Echinococcus Belong to family Taeniidae Contains 3 species for which humans are host to the larval stage (hydatids) o E. granulosus o E. multilocularis o E. vogeli Share the same Life cycle, Diagnosis, Treatment and Prevention & Control Epidemiology: o primarily involves parasitized members of the canine family o most important specie producing human disease o infection of this parasite is very rare in the Phil  Hydatids or hydatid cysts o larval stage / Infective stage o are large, roughly spherical, fluid filled hollow bladders o cyst wall consists of: outer laminate hyaline wall, supporting the whole cyst  Inner germinal layer studded with developing brood capsules the protoscolices are formed within the brood capsules, which may rupture to give off free protoscolices in the fluid filled cyst Thousands of protoscolices can fill the hydatid Hydatid cyst usually grow slowly but steadily (1-5 cm per year) producing protoscolices and daughter cysts that fill the cyst interior, they are usually well tolerated until their size becomes a problem or they rupture Cyst rupture or leakage can result in allergic reactions and metastasis 

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 Hydatid sand

From the inside surface of the fluid filled cyst grow hundred of protoscolices which bud off and fall to the bottom of the cysts, forming hydatid sand o a granular material, consisting of free  protoscolices, daughter cysts, and amorphous materials which is found in older cysts o sometimes aspirated for diagnostic purposes  3 forms hydatid cyst : o Unilocular hydatid cyst o

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Unilocular hydatid disease ( E. granulosus) Multilocular/alveolar hydatid cyst

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Multilocular/alveolar hydatid disease (E. multilocularis) Polycystic hydatid cyst

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Polycystic hydatid disease (E. vogeli)  Echinococcus granulosus Syn: Dog tapeworm, Hydatid worm Disease: Unilocular Echinococcosis, Unilocular Hydatid Disease  Intermediate host: sheep, goat, ,ox  Definite host: dog Humans: accidental intermediate host  Hydatid disease in man is caused principally by infection with the larval stage Geog. Dist: o Worldwide o Chiefly Russia, Siberia, Bavaria, Tyrol o heavy infection occurs in sheep raising areas of the world, South America, Iceland, Tasmania, Africa, Asia  Adult measures 0.25cm – o.9cm (ave 0.6cm) o Only 3 proglottods: 1 immature, 1 mature and 1 gravid proglottids Scolex 

globular shape with 4 prominent cup-shaped suckers o rostellum - armed with 2 circular rows of 28-50 large and small hooklets Mature proglottids -more elongated, and contains fully developed reproductive organs w/c consist of pyriform testes, 45-65 in number, and located anterior to cirrous sac -Bilobed ovary at the posterior portion o Club –shaped uterus o

 Gravid proglottids • longer than wide; Biggest segment of the strobila • Uterus at median, gives rise to 1215 lateral uterine pouches filled with eggs  Egg • spherical shaped, with radially striated embryophore • Cannot be distinguished from those of Taenia spp. • This genus compensate their very minute size by producing thousands of eggs  MOT: o Accidental ingestion of tapeworm eggs excreted in the feces of infected dogs o Intimate association with dogs o Contaminated fingers and food o 2° seeding from ruptured cyst  Pathogenesis: o disease will vary in their seriousness depending on where in the body the hydatid develops, and how large it grows Sometimes the infection is asymptomatic, the only evidence of infection being the presence of calcified cysts on autopsy after death due to an unrelated cause: o the major pathology is due to the size of the cyst, giving rise to pressure related injury by expanding o of hydatid cyst

cysts can grow to be the size of a softball or basketball, and may contain several smaller "balloons" inside the main cyst 

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Pressure effects can cause local tissue damage and obstruction -Leakage of hydatid fluid synsitizes the patient and elicit eosinophilia -a complication may arise if the cyst is ruptured, possibly due to blows to the body, muscular strain, or during operation -the hydatid cyst fluid is highly allergenic and cyst rupture may -result in severe allergic manifestations, anaphylactic shock and rapid death o deadliest tapeworm parasitizing humans 

 Diagnosis: o Stool exam – charac. Ova & gravid segments o X-ray, CT scan, Ultrasound – demonstate hydatid cyst o serological – Indirect HAI, ELISA, CF o Liver puncture o Blood smear – eosinophilia  Therapeutic Modalities: o Surgery: leaking cysts, infected cysts, multiple daughter cysts o Chemotherapy: Albendazole inoperable, in-aspiratable  Praziquantel – active protoscolicidal agent o Ivermectin – injected directly into cysts was found to kill protoscolices in experimental animals o Observation: extreme age, much calcification, well padded small cysts o Percutaneous aspiration & drainage of hydatid cyst of the liver & lungs  Prevention & Control: o Avoid fondling of infected dogs o Strict personal hygiene o Avoid eating contaminated foods

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Dogs should be dewormed periodically with Praziquantel every 6 wks

growth through the infected organ replacing that organ tissues -minor morphologic difference between hydatid cyst and alveolar cyst

Echinococcus multilocularis Syn: Dog tapeworm, Hydatid worm Disease: Multilocular Echinococcosis  Multilocular / alveolar hydatid disease recognized as distinct specie from E. granulosus definitive hosts: primarily foxes and to a lesser extent dogs, cats, coyotes and wolves intermediate host: rodents, mice  Man is an accidental host by the ingestion of eggs more adaptations for colder climates  Adults o very similar to E. granulosus, with a maximum length of approximately 4mm, and consisting of 4-5 proglottids  Larvae o the 'cyst' grows invasively by external budding, to proliferate in any direction, forming a diffuse

E. multilocularis limiting membran e

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germinal epitheliu m

Grows externally, to proliferate in any direction and act like a neoplasm with local infiltration or even to metastasize

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Alveolar or Multilocula r cyst

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Multilocular / Alveolar Hydatid Disease  Adults o As with E. granulolsus the adult tapeworm is usually o non-pathogenic to its canine hosts  Larvae o MOT

eating foods contaminated with feces of the hosts  hunters can be infected while handling foxes & wolves o common site of development: liver next lung and other organ -Growth in the vena cava or portal vein may lead to metastases, usually to the lungs or brain and other body organs -Prognosis is poor and depends on extend of organ involvement  the multilocular cyst is highly pathogenic due to its fast growth rate and invasive nature, in extreme cases completely replacing liver tissue thus simulating E. granulosus hepatocellular carcinoma with local pressure effects and allergy Thick & laminated

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Echinococcus vogeli Syn: Dog tapeworm, Hydatid worm Grows to the Disease: Polycystic Echinococcosis, internal cavity Polycystic hydatid disease of the cyst -found in Central and Northern South America definitive hosts: bush dogs Intermediate host: large rodents (pacas and spiny rats)  Larvae - Similar to that of E. granulosus  Adults - Similar to E. granulosus, but rather smaller; non-pathogenic -The germinal membrane of the hydatids proliferates both inward, in the original cyst, Unilocular forming septa that divide it in many sections cyst and outwards to form new multi-chambered more

cysts – resulting in multiple vesicles (polycystic hydatid cyst)  The vesicles forming a polycystic hydatid are relatively large and fluid filled  In humans, hydatids are found in the liver, but also the lungs, pleura, pericardium, heart, intercostal muscles & diaphragm, stomach, omentum and mesenteries

 Genus Hymenolepis Belong to family Hymenolepidae 2 species: Hymenolepis nana Geog. Dist: o cosmopolitan with highest infection in tropics o common in warm than cold region o endemic in Central Europe, India, Latin America and some Asian countries Hymenolepis diminuta Geog. Dist: o cosmopolitan endemic in Japan, China, Africa,Argentina, Russia, Latin America, & USA Hymenolepis nana Syn: Dwarf tapeworm Disease: Hymenolepiasis, Dwarf Tapeworm Infection Definitive host: house mouse, human intermediate host: grain beetles  infection is more common in children than in adults  It requires only one host but can also cycle through two hosts o has the unusual characteristic of being able to complete its lifecycle without the aid of the intermediate host o this makes H. nana the only tapeworm in which an adult will grow after the definitive host ingests the eggs  Adult o measures 25-40mm length x 1 mm width o Smallest cestode infecting humans

 Scolex o rhomboidal-shaped with 4 cupshaped suckers o rostellum armed with 1 circle of 20 to 30 hooks  Immature proglottids o wider than long and trapezoidalshaped  Mature proglottids o wider than long o 1 set of male & 1 set of female reproductive organs o 3 ovoidal testes arranged in straight line with a bilobed ovary in between o penis - the elongate body near the pore o a compact vitelline gland and a large uterus opening to a lateral genital pore (as does the cirrus) on the side of the segment  Gravid proglottids o wider than long o saclike uterus completely filled with 80-180 eggs o Also contains cirrous pouch, seminal receptacle  Egg o thin and smooth outer shell o Broadly ovoidal, hyaline & colorless, 30-47μm o Usually liberated from the gravid segments before they become detached o contain oncospere within a rigid membrane with 2 polar thickenings , from which 4-8 long and thin filaments (polar filaments) spread out between the two memb. o These filaments are visible in the space between the embryo and the outer shell  Infective stage: cysticercoid larva o A small larva that develop from the hexacanth larva of Hymenolepis characterized by possession of a single invaginated scolex but

without the bladder characteristic cycticercus life cycle: Adult worm develop following ingestion of the egg by definitive hosts ↓ eggs hatch in the duodenum, releasing oncospheres and lie in the lymph channels of the villi ↓ oncospheres develops into a cysticercoid, which attaches to ↓ the small intestine and matures into an adult ↓ gravid proglottids then release and pass out through feces along with eggs ↓ A. MOT: an oral-anal cycle in which eggs are passed from one human to another or recycle externally in a single host or eggs can hatch and infect original host and start cycle over ↓ B. MOT: internal autoinfection, whereby eggs hatch within the gut and initiate a 2nd generation infection without ever exiting the host Hymenolepiasis / Dwarf Tapeworm Infection -Pathogenesis: o Light infections are usually asymptomatic o When large number of worms are present: -Clin. Manifestations: abdominal pain, diarrhea, headache, dizziness, anorexia, and various nonspecific symptoms

Drug of choice: Praziquantel 25mg/k single oral dose alternative: Niclosamide daily for 5 days  Prevention & Control: o Proper personal hygiene o Protect food from being contaminated with mice, grain beetles o

Hymenolepis diminuta Syn: Rat tapeworm Disease: Hymenolepiasis, Rat tapeworm infection  Larger than H. nana  primary zoonotic Definitive host: rats -Completion of the life cycle require an arthropod intermediate hosts: flour beetle, flour moths  human is an incidental host, occasionally infected thru accidental ingestion of infected intermediate host that carry the parasite in their body cavities Infective stage: cysticercoid larva Morphology:  Adult o H. diminuta is slightly larger, measures 20-50 cm long x 4mm wide  Scolex o small, club-shaped with 4 cupshaped suckers and small rudimentary apical unarmed rostellum  Mature proglottids o same with H. nana  Gravid proglottids o sacculate-like uterus filled with eggs o Same with H. nana  Egg o o

 Diagnosis: o Stool exam – characteristic egg  Treatment:

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Round or slightly oval, yellow-brown color the shell is relatively thick, 60-80μ in diameter fine concentric striations in the outer shell

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space between the membranes is smooth or faintly granular, inside is the oncosphere enclosed in 2 membrane with 2 polar thickening but no polar filaments

Life cycle: The adult tapeworm is found in the host’s small intestine ↓ Eggs are passed in the host’s feces ↓ Eggs are eaten by intermediate host (flour beetle, flour moth) ↓ Oncosphere hatch and penetrate the intestinal wall of intermediate host ↓ larva develops into ‘cysticercoid larva’ in the body cavity ↓ of insects ingested by rodents or accidentally by humans Hymenolepiasis / Rat tapeworm infection Pathogenesis: o most asymptomatic but occasional patients may have mild GI complaints: nausea, anorexia, diarrhea and abdominal discomfort o no autoinfection o Eosinophilia, anemia may also be present  Diagnosis: Stool exam – characteristic egg  Treatment: drug of choice:  Niclosamide  Praziquantel – equally effective  Prevention & Control: o Proper rodent control measures o Destruction of intermediate hosts o Proper disposal of stools of infected person