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

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

Life cycle of dwarf tapeworm (Hymenolepsis nana)

Cycle

Direct Cycle – Ingestion of eggs or mouse pills

Indirect Cycle – Ingest larvae via ingestion of insects (Tenebrio beetle)

Internal Autoinfection – Eggs laid and hatch in intestine

Dwarf tapeworm intermediate host

Tenebrio beetle

Diagnosis of Hymenolepsis nana and treatment/prevention

Eggs in stool, Praziquantel, personal hygiene and mass chemotherapy

Taenia Tapeworms – differences in pathology

Taenia saginata – Beef tapeworm – little pathology

Taenia solium – Pork tapeworm – high degree of potential pathology

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)

Cysticercus bovis

Anatomical differences between humans and bovine Mean humans cannot get Cysticercus bovis

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 latum Physical traits

Long worm – 5 to 10 meters

As with all of these large tapeworms there is one worm per person As with all of these large tapeworms this worm is very long lived 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

Trematodes (trematos) literally means

pierced with holes – refers to suckers on the worm

Morphology and General Characteristics of trematodes

All exotic to U.S.

Hermaphroditic and separate sexes depending on species Flatworms

Digenetic

Refers to the parasite having a sexual reproductive cycle in a vertebrate host that alternates with an asexual reproductive cycle in an invertebrate mollusk host

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. Appears as an elongated sack containing offspring that leave vis a birth pore.

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.

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

Digenetic

• Hermaphroditic

• Operculated eggs

• Cercaria are straight tailed

• Encysted metacercaria is the infective stage

Do custodies have a metacercarial stage?

No

Operculated eggs

Have a “pop” up lid

Fasciolopsis buski

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

Fasciola hepatica and Fasciola gigantica

Why does Fasciola hepatica have a high pathology

MAftaernbiefinegsitnagetsitoedn, msetacercariae 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

Paragonomus westermani

Paragonomus kellicotti. carried by

Small crustaceans such as crayfish and fish

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