HELMINTHESHELMINTHES

Flat worms and Round wormsFlat worms and Round worms

HELMINTHOLOGYHELMINTHOLOGYPhylum Platyhelminthes = Flat wormsPhylum Platyhelminthes = Flat worms

Class Trematoda = FlukesClass Trematoda = FlukesClass Cestoda = Tape wormsClass Cestoda = Tape worms

Phylum Ashelminthes = Round wormsPhylum Ashelminthes = Round wormsClass Nematoda Class Nematoda

Genus AscarisGenus AscarisGenus TrichinellaGenus TrichinellaGenus Necator, AncylostomaGenus Necator, AncylostomaGenus EnterobiusGenus EnterobiusGenus DranunculusGenus DranunculusGenus WucereriaGenus Wucereria

HELMINTHOLOGYHELMINTHOLOGYPhylum Platyhelminthes = Flat wormsPhylum Platyhelminthes = Flat worms

Class Trematoda = FlukesClass Trematoda = Flukes

Some flukes are single sex, some Some flukes are single sex, some are are hermaphroditic possessing both hermaphroditic possessing both ovaries ovaries and testes.and testes.

Hermaphroditic Flukes

FIGURE 13-39FIGURE 13-39    Clonorchis sinensisClonorchis sinensis egg in a fecal specimen (X1000, D’Antoni’s iodine stain). egg in a fecal specimen (X1000, D’Antoni’s iodine stain). The eggs are thick shelled and between 27 and 35 µm long. There is a distinctive operculum (O) (positioned The eggs are thick shelled and between 27 and 35 µm long. There is a distinctive operculum (O) (positioned

to give the appearance of shoulders) and often a knob at the aboperular end (not visible in this specimen).to give the appearance of shoulders) and often a knob at the aboperular end (not visible in this specimen).

O

FIGURE 13-45FIGURE 13-45    Schistosoma mansoniSchistosoma mansoni egg in a fecal specimen (X1000, D’Antoni’s iodine stain). egg in a fecal specimen (X1000, D’Antoni’s iodine stain). Schistosoma mansoniSchistosoma mansoni eggs are large (114 to 175 µm long by 45 to 70 µm wide) and contain a larva called eggs are large (114 to 175 µm long by 45 to 70 µm wide) and contain a larva called

a miracidium. They are thin-shelled, lack an operculum, and have a distinctive lateral spine (arrow).a miracidium. They are thin-shelled, lack an operculum, and have a distinctive lateral spine (arrow).

FIGURE 13-46FIGURE 13-46    Schistosoma mansoniSchistosoma mansoni egg in a fecal specimen (X1000). The lateral spine egg in a fecal specimen (X1000). The lateral spine may be oriented in such a way as to be difficult to see. In this specimen, the spine (arrow) may be oriented in such a way as to be difficult to see. In this specimen, the spine (arrow)

is above the egg and the egg may be misidentified as is above the egg and the egg may be misidentified as S. haematobiumS. haematobium..

FLAT WORMSFLAT WORMSPhylum Platyhelminthes = Flat wormsPhylum Platyhelminthes = Flat worms

Class Cestoda = Tape wormsClass Cestoda = Tape wormsScolex contained in eggScolex contained in egg

holdfast structure with holdfast structure with hooks hooks and suckersand suckers

Proglottids major body of Proglottids major body of tapewormtapeworm

contains both ovaries and contains both ovaries and testes = hermaphroditictestes = hermaphroditic

Eggs can penetrate intestine of host and Eggs can penetrate intestine of host and form hydatid cysts in tissuesform hydatid cysts in tissues

FIGURE 13-57FIGURE 13-57    Taenia solium scolexTaenia solium scolex (X64). (X64). The The Taenia solium scolexTaenia solium scolex has two rings of hooks and four suckers. has two rings of hooks and four suckers.

FIGURE 13-55FIGURE 13-55    Taenia spp.Taenia spp. egg in feces (X1000). Taeniid eggs are distinctive looking enough egg in feces (X1000). Taeniid eggs are distinctive looking enough to identify to genus, but not distinctive enough to speciate. Eggs are spherical and approximately 40 µm to identify to genus, but not distinctive enough to speciate. Eggs are spherical and approximately 40 µm

in diameter with a striated shell. The oncosphere contains six hooks.in diameter with a striated shell. The oncosphere contains six hooks.

ROUND WORMSROUND WORMS

Phylum Ashelminthes = Round wormsPhylum Ashelminthes = Round wormsClass Nematoda Class Nematoda

Genus Ascaris – most commonGenus Ascaris – most commonGenus Trichinella Biblical wormGenus Trichinella Biblical wormGenus Necator, Ancylostoma - Genus Necator, Ancylostoma -

hookwormshookwormsGenus Enterobius – pinworm 2Genus Enterobius – pinworm 2ndnd most most

common common Genus Dranunculus - GuinaeGenus Dranunculus - GuinaeGenus Wuchereria - Elephantiasis Genus Wuchereria - Elephantiasis

Mosquito Mosquito borneborne

HookwormsHookworms

► Ancylostoma duodenali and Necator americanus Ancylostoma duodenali and Necator americanus Old world and new world hookworms differ only Old world and new world hookworms differ only in their geographic location.in their geographic location.

Human phase of this worm begins with a Human phase of this worm begins with a filaform larvae penetrating the skin, enters filaform larvae penetrating the skin, enters circulation, carried to the lungs, coughed up and circulation, carried to the lungs, coughed up and swallowed, develops to adulthood in small swallowed, develops to adulthood in small intestine. Adult worms lay between 10,000 and intestine. Adult worms lay between 10,000 and 20,000 eggs per day. Daily blood loss 20,000 eggs per day. Daily blood loss 0.2ml/adult/day. Microcytic hypochromic 0.2ml/adult/day. Microcytic hypochromic anemia develops.anemia develops.

FIGURE 13-64FIGURE 13-64  Heads of adult hookworms.   Heads of adult hookworms. (a)(a) Ancylostoma duodenaleAncylostoma duodenale head (X64) showing the pairs of chitinous teeth (arrow). head (X64) showing the pairs of chitinous teeth (arrow).

(b)(b) Necator americanusNecator americanus head (X160) showing the cutting plates (arrow). head (X160) showing the cutting plates (arrow).

a b

FIGURE 13-63FIGURE 13-63  Hookworm egg in feces (X1000, D’Antoni’s iodine stain). Hookworm eggs   Hookworm egg in feces (X1000, D’Antoni’s iodine stain). Hookworm eggs are 55 to 75 µm long and 36 to 40 µm wide. They have a thin shell and contain a developing embryo are 55 to 75 µm long and 36 to 40 µm wide. They have a thin shell and contain a developing embryo

(seen here at about the 16 cell stage) that is separated from the shell when seen in fecal samples.(seen here at about the 16 cell stage) that is separated from the shell when seen in fecal samples.

Biblical wormBiblical worm

►Trichinella spiralis etiological agent of Trichinella spiralis etiological agent of trichinosis. Infectious larva is present trichinosis. Infectious larva is present in the striated muscle of carnivorous in the striated muscle of carnivorous and omnivorous mammals. Swine and omnivorous mammals. Swine most common organism to transmit to most common organism to transmit to humans. Encysted larvae live for many humans. Encysted larvae live for many years. Polar bears and walruses are years. Polar bears and walruses are accounting for new human infestations accounting for new human infestations in our Alaskan artic regions.in our Alaskan artic regions.

FIGURE 13-68FIGURE 13-68    Trichinella spiralisTrichinella spiralis larva in skeletal muscle (W.M., X260). larva in skeletal muscle (W.M., X260). The spiral juvenile and its nurse cell are visible in this preparation.The spiral juvenile and its nurse cell are visible in this preparation.

FIGURE 13-69FIGURE 13-69    Trichinella spiralisTrichinella spiralis larvae in skeletal muscle (sec., X260). Each larva has entered larvae in skeletal muscle (sec., X260). Each larva has entered a different skeletal muscle cell and converted it into a nurse cell that sustains it with nourishment.a different skeletal muscle cell and converted it into a nurse cell that sustains it with nourishment.

Pin worms or Seat wormsPin worms or Seat worms

►Enterobius vermicularis most common Enterobius vermicularis most common helminthic infestation in America, 500 helminthic infestation in America, 500 million cases annually globally second million cases annually globally second globally to Ascaris infestations.globally to Ascaris infestations.

Eggs are ingested mainly fecal-Eggs are ingested mainly fecal-oral.Egg laden dust can be inhaled. oral.Egg laden dust can be inhaled. Autoinfection occurs frequently. Autoinfection occurs frequently. “Scotch Tape Test” from perianal folds “Scotch Tape Test” from perianal folds of diagnostic value.of diagnostic value.

FIGURE 13-62FIGURE 13-62    Enterobius vermicularisEnterobius vermicularis egg (X1000, D’Antoni’s iodine stain). egg (X1000, D’Antoni’s iodine stain). The eggs of The eggs of Enterobius vermicularisEnterobius vermicularis are 50 to 60 µm long and 20 to 40 µm wide are 50 to 60 µm long and 20 to 40 µm wide

with one side flattened (arrow). They are usually embryonated in typical preparations.with one side flattened (arrow). They are usually embryonated in typical preparations.

Ascaris LumbricoidesAscaris Lumbricoides

► Large worms 25cm – 45cm in length. Most Large worms 25cm – 45cm in length. Most common helminth with over a billion infested a common helminth with over a billion infested a year. Prevalent in areas where sanitation is year. Prevalent in areas where sanitation is poor and human waste is used as fertilizer.poor and human waste is used as fertilizer.

► Ingested egg releases a larva that penetrates Ingested egg releases a larva that penetrates the duodenal wall and carried to the liver and the duodenal wall and carried to the liver and the heart, enters the pulmonary system, enters the heart, enters the pulmonary system, enters the alveoli where they molt and mature. They the alveoli where they molt and mature. They are coughed up, swallowed and returned to the are coughed up, swallowed and returned to the small intestine. Adults can be passed out into small intestine. Adults can be passed out into the feces.the feces.

Pathogenesis ofPathogenesis ofAscaris suum Ascaris suum (Larvae)(Larvae)

►Damage associated with larval Damage associated with larval migrationmigration

LiverLiver within 24 hr PIwithin 24 hr PI hemorrhage, inflammation, necrosis hemorrhage, inflammation, necrosis ““milk spots” - fibrosismilk spots” - fibrosis resolves after treatmentresolves after treatment

Pathogenesis ofPathogenesis ofAscaris suum Ascaris suum (Adults)(Adults)

► Interfere with digestion and absorptionInterfere with digestion and absorption poor feed conversion, stuntingpoor feed conversion, stunting

►Obstruction or rupture of intestineObstruction or rupture of intestine►Migrate up bile ductMigrate up bile duct

obstructive jaundiceobstructive jaundice

FIGURE 13-59FIGURE 13-59  Fertile   Fertile Ascaris lumbricoidesAscaris lumbricoides egg in feces (X1000, D’Antoni’s iodine stain). egg in feces (X1000, D’Antoni’s iodine stain). Fertile Fertile Ascaris lumbricoidesAscaris lumbricoides eggs are 55 to 75 µm long and 35 to 50 µm wide and are embryontated. eggs are 55 to 75 µm long and 35 to 50 µm wide and are embryontated.

Their surface is covered by small bumps called mammillations.Their surface is covered by small bumps called mammillations.

FIGURE 13-71FIGURE 13-71    Wuchereria bancrofti Wuchereria bancrofti microfilaria in a blood sample (X960). microfilaria in a blood sample (X960). The microfilariae of The microfilariae of Wuchereria bancroftiWuchereria bancrofti can be distinguished from others in the blood can be distinguished from others in the blood by the sheath (S) and the single column of nuclei (N) not extending to the tip of the tail.by the sheath (S) and the single column of nuclei (N) not extending to the tip of the tail.

N

S