parasitology exam 2 review

Cestode general morphology

Flat and ribbon like, hermaphroditic, almost all reproductive material, generally have a scolex, neck, strobila (body), and proglottids

Scolex

Orientation of the worm - Biological holdfast, not for support or a physical anchor, not for feeding.

Proglottids

Worm segments that are sexually immature, sexually mature, or gravid depending on age

Neck

undifferentiated stem cells that give rise to the proglottids

Chain of proglottids, but can also sometimes be the neck is

Strobilia

Tapeworms are highly specialized and lack a

Digestive tract

Food is digested by the host and tapeworms absorb nutrients

directly across their tegument using – pinocytosis, diffusion, facilitated diffusion, and active transport.

Dwarf tapeworm actual name

Hymenolepsis nana

Infective stage of hymenolepsis nana

Cystercercoid

Hymenolepsis nana morphology

• • •

Hymenolepsis nana - Dwarf tapeworm

– 1-3 inches long

Scolex – 4 suckers and hooks on rostellum

Eggs free in host gut as proglottids usually disintegrate in the gut and eggs pass in feces

Dwarf tapeworm intermediate host

Tenebrio beetle

Diagnosis of Hymenolepsis nana and treatment/prevention

Eggs in stool, Praziquantel, personal hygiene and mass chemotherapy

Taenia saginata (beef tapeworm) characteristics

Very long parasite – 5 to 10 meters, but up to 25 meters

Scolex – 4 suckers, no hooks Proglottids – IMPORTANT

Longer than wide More than 15 uterine

branches

Found whole in stool –

mobile in stool

Can migrate out of anus

not armed (no rostellum)

Taenia spp. infective stage

cyctercerci in muscle

Which tapeworm causes so little pathology it’s been sold as a weight loss supplement?

Taenia saginata

Diagnosis, treatment and prevention of Taenia saginata

Diagnosis

Proglottids in stool, praziquantel, inspect and properly cook beef and no sewage in grazing area

Pork tapeworm is called

Taenia solium

Taenia solium – Pork tapeworm Characteristics

Long worm – 8 to 10 meters

Scolex – Suckers and hooks

Proglottids – Less than 13 uterine branches

Has armed rostellum

pathology of Taenia solium

Adults in small intestines. Danger from ingestion of embryonated eggs which enters circulation- travels to any organ in body

Cystercercus cellulosae

Ingestion of embryonated eggs of Taenia solium

Jacksonian epilepsy

When Taenia solium larvae enter brain- No encystment – can grow into grapelike clusters. Causes Jacksonian epilepsy. Surgery is needed with death common

Diagnosis, treatment and prevention of pork worms

Proglottids in feces for adult worm

X-Ray, CT scans, MRI for Cysticercus cellulosae, Praziquantel and possibly surgery to clear cyst

Proper disposal of feces Cook or freeze pork Inspect pork

Fish tapeworm Is known as

Diphyllobothrium latum

Diphyllobothrium Latin (fish tapeworm) infective stage

Plerocercoid stage

Diphyllobothrium latum traits

Has plerocercoid larvae

one worm per person - large

Scolex - Bothrium – leaf-like suckers or sucking grooves

Pathology of Diphyllobothrium latum

Mild attachment damage

Some allergic reaction to metabolites

Worm has great affinity for Vitamin B 12 – Pernicious anemia is common in

those infected

Diagnosis , treatment, and prevention of Diphyllobothrium latum

Eggs in stool, Praziquantel, cook fish and prevent sewage from contaminating water

Taenia pisformis

Rabbit tapeworm, can form cysterci similar to Taenia solium

Diphyllidum cainum

Double bored dog and cat tapeworm

Hydatid cysts

Second stage larvae form of Echinococcus spp.

Alveolar hydatid disease

Echinococcus multilocularis

Acetabula

Refers to the parasite having cup shaped suckers oral and ventral Characterized by complicated life cycles with multiple stages in multiple host

General Life Cycle Of trematodes

Egg, Miricidium, 1st Generation Sporocyst (Mother Sporocyst), 2nd Generation Sporocyst (Daughter Sporocyst), Redia , Cercaria, Metacercaria, Adult Worm

Miracidium Stage of trematodes

larval stage that hatches from egg and is infective for intermediate host (mollusk). Cilia for swimming.

Usually live 24 hours

1st Generation Sporocyst or Mother Sporocyst in trematodes

Asexual stage found in snail host that gives rise to multiple 2nd Generation Sporocyst or Redia Depending on species.

2nd Generation (Daughter) Sporocyst or Redia

Mother sporocyst give rise to 2nd Generation Sporocyst or Redia depending on species. Both are part of the Asexual reproduction cycle producing cercaria.

General lifecycle for trematodes infective in metatarsal stage

Miricidium - 1st generation sporocyst- 2nd generation sporocyst - redia - cercaria - metacercaria - adult worm

Cercaria

Free swimming trematode stage that is infective for the vertebrate host. There are two general types:

Cercaria that encyst to form metacercaria which is ingested by the definitive vertebrate host. Cercaria encyst on plants and animals.

Most cercaria tails

Forked tail to infect vertebrae host directly, no metacercarial stage

Trematodes Infective in the Metacercarial Stage

Characteristics

Flukes

Digenetic

• Hermaphroditic

• Operculated eggs

• Cercaria are straight tailed

• Encysted metacercaria is the infective stage

Do cestodes have a metacercarial stage?

No

Operculated eggs

Have a “pop” up lid

Fasciolopsis buski common name

Giant intestinal fluke

Pathology and clinical manifestations of giant intestinal fluke

Traumatic damage Irritation

Ulceration

Hemorrhage

Intestinal obstruction of small intestine Penetration of gut

Toxic metabolites

Diarrhea

Green yellow stool Undigested food

Fascioloplasis buski treatment and prevention

Treat sewage, kill snails, boil water plants, age night soil, treated with praziquantel

Common sheep liver fluke known as

Fasciola hepatica and Fasciola gigantica

Why does Fasciola hepatica have a high pathology

After ingestion, metacercariae penetrate the intestine, traverse the peritoneal cavity, and penetrate the liver capsule. They burrow through the liver parenchyma for 1 to 3 months, while maturing, and finally enter the bile ducts to complete the life cycle lesions are created as they coarse through the liver .

Diagnosis of Fasciola hepatica

Eggs in stool, duodenal aspirate, bile duct aspirate , sonogram of liver/bile duct/gallbladder, easiest is through CT or MRI scan of liver

Treatment of Fasciola hepatica

Triclabendazole is the drug of choice – Must watch inflammation caused by dead worms in liver

Parasite removal at endoscopic retrograde cholangiopancreatography is effective in the biliary stage.

Prevention of Fasciola hepatica

Water-grown vegetables should be washed with 6% vinegar or potassium permanganate for 5-10 minutes, Cook water grown vegetables thoroughly, avoid sewage contamination, use of molluscicides , treatment of animals

Liver fluke that’s contracted by eating improperly cooked fish

Clonorchis senensis

Geographic distribution of Clonorchis senensis

Japan, Korea, Vietnam, China , Taiwan

Lung fluke name

Paragonomus westermani

Paragonomus westermani diagnosis, treatment, and prevention

Eggs in sputum or eggs in feces (swallowed), X-ray or other imaging of lungs

Praziquantel

Treat sewage, age night soil, do not eat raw or undercooked crustaceans, prohibit spitting to keep eggs from entering water

Paragonomus kellicotti is carried by

Small crustaceans such as crayfish

Diagnosis of Paragonomus spp.

Eggs in sputum and/or feces, x ray and other imaging of lungs, prevented with treating night soil , sewage, no eating raw or undercooked crustaceans , praziquantel is drug of choice

Trematodes Infective in the Cercarial Stage Called

Schistosomes

Schistosomes Characteristics

Separate sexes

Eggs with spines or cutting tool Most pathology caused by eggs, no operculation

as they migrate through tissues

Schistosoma mansoni adults in life cycle

adults generally in the inferior mesenteric veins that drain the large intestines

Schistosoma japonicum Adults location

adults generally in the superior mesenteric veins that drain the small intestines

Schistosoma hematobium adults location

adults generally in the vesical, rectal, and pelvic veins that drain the lower large intestine (rectal area) and bladder

Reservoir host of S. mansoni and S. japonicum

Dog, cat, mice, pig

S. hematobium reservoir host

None

Common name for Schistosomes

Blood flukes, bc they reside in the blood vessels

Arteriovenous shunt As result of long term damage to blood vessels from Schistosomiasis

long term to damaged vessels of the large intestines results in esophageal varices and hemorrhoids. Bleeding from esophageal varices are a major cause of death – exsanguination.

Diagnosis, treatment and prevention of Schistosomes infection

Eggs in stool, intestinal biopsy, praziquantel, kill snails w molluscacides and biological control, and no feces in water

Schistsoma hematobium - Urinary schistosomiasis Pathology and Clinical Manifestations

Bladder associated vessels inhabited by worms

Bladder hyperplasia – thickening --- fibrosis --- cancer Inflammation -- Sloughing of bladder tissue --Urethra blockage –

cystitis – kidney failure

Bladder loses elasticity -- calcification

Schistosoma infective stage

Cercaria stage

Trematodes intermediate host

Snails

Trematodes infective at metatarsal stage:

Fasciolopsis buski

Fasciola hepatica/gigantica

Clonorchis senensis

Paragonomus kellicotti/ westermani