Endoparasites General

Types of endoparasites

Nematodes

Cestodes

Trematodes

Acanthocephalans

Protozoa

Types of nematodes

Roundworms

Whipworms

Hookworms

General morphology of nematodes

Unsegmented

Circular in cross section

Different types of shapes - spherical, whip-like (whipworms), terminal enlargements (strongylus vulgaris)

Characteristics of nematodes

Dioecious - two sexes

Has GI tract - with mouth variations

Has reproductive tract - big and extensive

Ascarid egg (nematode)

Strongyle (trichnstronglye) egg (nematode)

Spiruroid egg (nematode)

Trichuroid egg

Direct life cycle of nematodes

No intermediate host - they stay on one host for its whole life

Indirect life cycle of nematode

Has intermediate hosts - changes host

Simple cycle of a nematode

Egg → single cell to morula → tadpole → L1 (stage 1 larvae) → egg hatches → L2 → molts → L3 (INFECTIVE) → L4 → L5 (immature adult) → migrate to site predilection → mature adult (REPRODUCING EGGS)

Types of nematode eggs

Ascarid

Strongyle

Trichuroid

Spiruroid

Two types of cestodes

Cotyloda (pseudotapeworms)

Eucestodia (true tapeworm)

Cestodes aka

Tapeworms

Morphology of cestodes

Segmented*

• Neck

• Strobilia/body - proglottids → hermaphroditic, they self/cross fertilize

Dorsoventrally flattened like a ribbon

Internal structures of cestodes

Internal structures - NO GI tract (they absorb nutrients from intestine)

Reproductive tract - each proglottid has its own reproductive tract, mature are reproducing

Cestodes egg types

Pyriform apparatus

Dipylidium

Taenia

Pseudophyllidean

Pyriform apparatus egg (cestodes)

Dipylidium egg (cestodes)

Taenia egg (cestodes)

Pseudophyllidean egg (cestodes)

Cotyloda (pseudotapeworm) life cycle

1. Eggs passed individually*

2. Egg is in external environment and hatches in water → coracidium

3. Coracidum ingested by 1st intermediate host (copepod crustacean) → Procercoid

4. Procecercoid ingested by 2nd intermediate host (fish) → Plerocercoid (INFECTIVE)

5. 2nd intermediate host ingested by definitive host → tapeworm emerges, attaches to intestine

1st intermediate host of cotyloda

Copepod crustacean

2nd intermediate host of cotyloda

Fish

Eucestode (true tapeworm) life cycle

1. Proglottids passed intact (thousand of eggs)

2. Eggs ingested by intermediate host

3. Develops - metacestode → different forms of

4. Intermediate host ingested by definitive - attaches to intestine

Intermediate host of eucestode

Invertebrate or vertebrate animals - basically anything that ingests it

Trematodes aka

Flukes

Morphology of trematodes

Unsegmented*

Flattened

Shape variations - leaf-like (fasciola hepatica), worm-like (schistomes)

Types of trematodes

Monogenetic - single host

Digenetic* - 2-4 obligate hosts

Characteristics of trematodes

Hermaphroditic - both sexes, except blood flukes

Internal structures - GI tract → has mouth structures, esophagus, blind ceca (NO anus) - so they regurgitate food

No body cavity

Has ventral sucker on acetabulum for attachment

Digenetic trematode life cycle

Eggs passed → external environment or water → hatches into miracidium (motile and can move)

Miracidium penetrates intermediate host → Cercariae

Cercariae has 3 options

• Penetrate skin of def host → migrate to predilection site → matures to adult

• Attach to vegetation → encyst → eaten by defin host → Migrate to predilection site, mature to adult

• Penetrate 2nd intermediate host ingested → encysts into metacercaria → 2nd intermediate host is eaten by def host → migrates to predilection site and matures to adults

Predilection sites of trematodes (aka where they stay after they become adults)

GI - rumen, reticulum, intestines, liver, bile duct

Respiratory - lungs

Blood vessels - schistosomes

Trematodes egg

Operculated

Type of digenetic trematode life cycle

Indirect

1st intermediate host of digenetic trematode

Mollusk (snail)

1st intermediate host of digenetic trematode

Mollusk (snail)

Morphology of acanthocephalans

Elongated

Cylindrical

Retractable proboscis (nose) - spine covered, caudally directed attachment

Internal structures of acanthocephalans

No GI tract - they need to absorb nutrients

Dioecious

Life cycle of acanthocephalans

Eggs passed in feces (has acanthor)

Intermediate host ingests arthropods → egg hatches into a larvae → develops into acanthella, then cystacanth

Definitive host ingests intermediate host → attaches to intestine, matures to an adult

Intermediate host of acanthocephalans

Arthropods - dung beetle

Types of protozoa

Mastigophora - flagellates

Sarcodina - amoeba

Cliophora - ciliates

Apicomplexa

Types of parasitic flagellates protozoans (mastigophora)

Leishmania spp.

Trypanosoma spp.

Trichomonas spp.

Histomonas spp.

Giardia spp.

What is a trophozoite

Active feeding form of protozoa that can be motile

Can develop into a cyst

What kind of environment do flagellates need

Liquid environment like blood, lymphatic fluid, CSF

What kind of environment do amoeba need

Require solid surfaces

What are the parasitic amoeba we can see

Entamoeba histiolytica

Acanthomoeba spp.

Entamoeba coli

Naegleria fowleri

What kind of envoinrment do ciliates need

Liquid environment

Out of all the protozoans, which is the highly pathogenic one as a parasite

ciliates - ciliophora

What are the pathogenic ciliates

Balantidium coli

Ichthyophthirus multifiliis

What are the types of pathogenic apicomplexans

Haemosporidia - in the blood

Piroplasms - in the cells in the blood

Coccidia

What are types of haemosporidia

Plasmodium vivax

Haemoproteus columbae

Leucocytozoon spp.

What are types of piroplasms

Babesia spp.*

Theileria spp.*

Cytauxzoon felis.

Mastigophora or flagellates are

Protozoans

What are the types of coccidia

Eimeria spp.

Cystoisospora spp.

Cryptosporidium spp.

Toxoplasma gondii

Sarcocystitits spp.

Encephalitozoon spp.

Hepatozoon spp.

Sarcodina or amoeba are

Protozoans

Ciliophora or ciliates are

Protozoans

Roundworms are

Nematodes

Hookworms are

Nematodes

Whipworms are

Nematodes

Tapeworms are

Cestodes

Flukes are

Trematodes

Development of cotyloda (pseudotapeworm) eggs

Eggs hatch → coracidium → ingested by 1st int. host → procercoid → ingested by 2nd int. host → plerocercoid (INFECTIVE) → 2nd int. host ingested by def. host → tapeworm emerges and attaches to intestine

Development of eucestode egg

Egg → metacestode → cysticercoid → cysticercus → coenurus → hydatid cyst → tetrathyrdium (i think) → intermediate host ingested by def host → tapeworm emerges

Digenetic trematode egg development

Egg passed in water → hatches into miracidium → penetrates int. host and sporocysts into cercariae → can take 3 options to reach def host → if it penetrates 2nd int. host → becomes metacercaria → migrates to predilection site and matures to adult

3 routes for trematode cercaria to go

1. Penetrate skin → migrates to predilection site → mature to adult

2. Attach to vegetation → encysts → eaten by def. host → migrates to predilection site and matures

3. Penetrates 2nd int. host → encysts → hatches into metacercaria → 2nd int. host eaten by def host and migrates to predilection site and matures to adult