Helminths — Introduction

What are helminths?

Helminths are Parasitic Worms!

• Invertebrates — many are parasites of veterinary and public-health importance

What are Macroparasites

— they ”generally” do not multiply inside the animal, so the burden reflects what it picked up

What kind of worm is Elongated

(roundworms)

What kind of worm is flat and segmented

(tapeworms)

What kind of work is leaf like

(flukes)

Which kind of worm is elongated with a thorny head

(Acanthocephalans)

We mentioned that macroparistes don’t multiply but what do they do instead

its more so how many larve they get ingested or how many eggs they ingest

Can you give me the basic lifestyle of a helminth

All develop through egg → larval (juvenile) stages → adult

What are the phylums of helminths

• nematoda

• platyhelminthes

• acanthocephala

What is an example of a Nematoda

round worms

What is an example of platyhelminthes

flatworms

What is an example of acanthocephala

thorny headed worms

What is the order for a nematoda

• ascaridida

• strongylida

• spiruirda

• rhabditida

• trichinellida

What are the families of a nematoda

• ascarididae

• toxocaridae

• anisakidae

• strongylidae

• trichostrongylidae

• metastrongylidae

• trichinellidae

Which worm is the most abundant animal on earth

nematodes

Most of the helminths that matter in practice are

nematodes

What does Pseudocoelomate mean

the body cavity holds fluid under pressure, and that turgor is the worm's skeleton

Describe the body of the neatodes

Body covered by a tough non-cellular cuticle, shed at each of four molts

Do nematodes have a digestive system?

yes, Complete digestive system — an anterior mouth and a posterior anus

Nerve function is essential to a nematode's survival — why is that

and it is the target of many anthelmintics you will prescribe.

Most nematodes shed

shed eggs, but some shed L1 in the feces, and a few shed in urine

For most GI nematodes, L3 is the infective or effective

infective stage, for a very few L1 is infective

Where does L3 → L4 → L5 occur

happens inside the definitive host

Maturing larvae may migrate through

organs before the adults settle in their preferred site — which is why the damage is often nowhere near where the worm ends up

What does Hypobiosis mean

many nematodes can arrest development in the mucosa and wait for appropriate condition/environment to resume development. It is an adaptation, not a failure.

When will hypobiosis

many nematodes can arrest development in the mucosa and wait for appropriate condition/environment to resume development. It is an adaptation, not a failure.

In Hypobiosis can we get a false negaive yes or no?

for the most start we might get false negatives or not, we might not get any fecal egg count, but the animal has parasites in the hyperbiotic states and we might still se the disease any exposure and we might not it depends

Why is it a challenge when we try to medicate nematodes in hypopbiosis

• challenging to use the drugs because they may not be effective, especially when larvae is in hyperbiotic state

Describe the general nematodes shape and size

Round, unsegmented, tapered at both ends. Typical range: 2 mm to 40 cm.

We already mentioned a description about whip worms but what else do they look like

whip-like shape, and have thick backside

What are some anterior end/mouth parts of an adult nematodes

§ Buccal cavity

§ Teeth, hooks, cutting plates

§ Lips

Hookworms – Ancylostoma can you describe the mouth parts

Buccal Cavity + hooks

What are the parts of the mouth of a hook work - uncinaria

Cutting plates

Ascarids Toxocara describe the mouth

3 fleshy lips

Hook worms and stoma have what kind of mouth

they have hooks

What are the parts of the posterior and tail parts of the adult nematodes

§ Bursa

§ Spicules

§ Tail length/shape

if the tail end has a bursa is it a male or female strongyle

Male Strongyles

If the tail end does not have a bursa is it a male or femal ascarides

Male Ascarids

If it has a simple pointed tail is it a female or male nematodes

most female nematodes

Nematodes release their offspring in three ways what are they

• oviparous

• ovoviviparous

• viviparous

What is a viviparous:

live larvae, released straight into feces, blood or tissue.

What is a ovoviviparous:

release eggs containing fully formed live larvae (larvated eggs)

What is oviparous:

release eggs with a single-cell embryo (most of them)

Can you describe the ascarid egg

§ round, thick rough shell, one cell inside. Tough, survives in soil for years.

Can you describe Strongyle egg

§ Thin, smooth egg shell. Oval with ball of cells inside

Can you describe Trichurid / capillarid type

barrel-shaped with a plug at each pole.

Can you describe strongyles in the egg or larvae form

• larvae with pointed tail

• most lungworms

• kinked tail

Can you describe the Spirurid egg/ larvated!

slightly flattened to one side and some auxillary they have larvae already inside and some do not

The order/group is srongylida what are some examples

• hook works

• trichostrongyles

• strongyles

• most lungworms

The order is Strongylida how do we recognize it

• Well-developed buccal capsule

• often with teeth;

• Male with a copulatory bursa

What is a lifecyel for Strongylida

Mostly direct. Strongyle-type egg — thin, oval, morulate, and near-identical across the whole group

The order is a Rhabditida what is an example

Threadworms

How do we recgonize Rhabditida

Esophagus with a bulb — “rhabditiform”

What is the life cycle of Rhabditida

Facultative — alternates parasitic and free- living generations. Transmammary transmission

The order is Ascaridida give me an example

The large roundworms of dogs, cats, pigs and horses

How do we recognize Ascaridida

Large, stout worms with three prominent lips

What is the life cycle of a ascaridida

• Mostly direct, may use paratenic hosts.

• Larval migration through liver and lung.

• Thick, rough, pitted egg

The order is Oxyurida what is an example

Pinworms

How do we reconigze Oxyurida

Long tapering tail; bulb on the esophagus

What is the life cycle of oxyurida

Direct; large intestine only, and highly host- specific. Eggs laid on the perineum

The order is Spirurida what are examples of them

Heartworm and the other filariae, eyeworms, stomach worms

How do we recognize spiruirda

A varied group; includes the blood and tissue worms

WHat is the life cycle of a spiruirida

Always indirect — an arthropod intermediate host, often paratenic hosts too. Thick-walled larvated egg

What are examples of Adenophorea

Whipworms, the trichina worm, hair worms and the kdiney worm

How do we recognize Adenophorea

Stichosome esophagus — a single column of gland cells

What is the life cycle of an adenophorea

Gut, kidney, nose, muscle. Bipolar-plugged eggs — except the trichina worm, which lays none at all

Do cestodes have a GI system

§ No gut at all, everything is absorbed across the tegument

What are the three body parts of a cestodes

§ scolex (holds on — suckers ± hooks)

§ neck (the growth zone)

§ strobila (chain of proglottids)

Most proglottids contain both

male and female reproductive organs (hermaphrodite); fertilization may occur within or

between proglottids.

Gravid proglottids seen in

feces

• this is towards the end of the body

What is the drug of cestodes

• Praziquantel is the drug of choice.

• It disrupts calcium homeostasis and damages the tegument.

Cestodes — general life cycle have how many cycles that are indirect

2 or 3 hosts

Which stage in the life cycle of Cestodes where is it more pathogenic stage

The larval form (metacestode) in the intermediate hosts are the most pathogenic stage, not the adult.

Definitive-host feces can expose

people and livestock to infective eggs in selected zoonotic cycles.

Do vet care about Cyclophyllidean tapeworms

Most tapeworms of veterinary importance

How many hosts do Cyclophyllidean tapeworms affect

Generally, one intermediate host – on land

What are examples of Cyclophyllidean tapeworms

The taeniids, and the flea tapeworm of dogs and cats

Where do Cyclophyllidean tapeworms attach to

Organ of attachment: Suckers – often with hooks!

Cyclophyllidean tapeworms produce eggs

Eggs: Not operculate

Do vets care about Pseudophyllidean tapeworms

Only a few genera of veterinary importance

How many hosts do Pseudophyllidean tapeworms

Mostly two intermediate hosts – both aquatic!

What are examples of Pseudophyllidean tapeworms

The fish tapeworm, and its relative in dogs, cats and wild carnivores

Where do Pseudophyllidean tapeworms attach to

Organ of attachment: Bothria — slit-like grooves, no hooks!

Do Pseudophyllidean tapeworms have eggs

Eggs: Operculate

Describe Trematodes — the flukes!

Flatworms, but a single leaf-shaped body — no chain of segments, no strobila

Do trematodes have a gut?

Yes, They have a gut — a mouth and two blind-endingbranches. Unlike tapeworms, flukes actually eat

Do trmatodes have suckers?

Two suckers hold them on — one around the mouth, one on the belly surface

What kind of meds would we use for trematodes

Same tegument as tapeworms — absorptive, and the reason praziquantel works on both

How do trematode reproduce

§ Most are hermaphrodite — one worm can reproduce alone. Blood flukes are the exception, with separate sexes

What is the first step of the general life cycle of trematodes

Always more than one host — and the first one is always a snail. No snail, no fluke

What is the order for a trematodes life cycle

egg → miracidium → snail amplifcation → cercaria

what leaves the snail

cercaria

How does the cercaria (from the trematodes multiply)

The parasite multiplies asexually inside the snail — one egg can become hundreds of cercariae. Nothing else we study does this

The cercaria encysts as a

metacercaria — on grass, in a fish, in an ant, in a crustacean

What is the last step of the trematodes

The final host gets infected by eating it — except blood flukes, where the cercaria burrows

through skin

Are adults easy to diagnnose of trematodes

Adults are easy to identify – flat, soft, leaf-shaped, a few mm to a few cm. Distinct from roundworms and tapeworms

Whats is another way we diagnose tramtodes

• Eggs are also characteristic: big, golden-brown with a lid on one end (operculum) – much larger than nematode and cestode eggs [Exception blood fluke]

• Often poorly recovered by routine flotation.

Which exception of Tramtodes can float

Alaria – floats!

Are Acanthocephalans common

§ A distinct phylum of specialized parasites, less commonly encountered in routine domestic-animal practice.

Describe the Acanthocephalans

A retractable, spiny attachment organ — the proboscis, the thorny head. The proboscis may deeply penetrate the intestinal wall; inflammation, ulceration, obstruction, and, in severe cases, perforation/peritonitis can occur.