Nematodes (Exam 4)

Exam 3 of Parasitology is the Nematodeds. Blue text is testable material, black text is general info or potential extra credit

This is an example of a ______, commonly known as roundworms

Nematode

AKA “roundworms”

Nematode: morphologic characteristics

Long cylindrical organisms covered by a cuticle

Have a large body cavity (pseudocoelom)

Nematodes are ______ (two sexes)

Non-hermaphroditic

Males smaller than females

Females have a vulva that may be located near the oral end, tail end, or in the middle

Male nematodes have ____ for grasping females

copulatory bursa (bursates) and copulatory spicules

Nematode: Typical Life cycle

egg → one cell → morula → vermiform embryo → 1st stage larva → 1st molt → 2nd stage larva → 2nd molt → 3rd stage larva → 3rd molt → 4th stage larva → 4th molt → 5th stage (adult)

Name this class of nematodes (includes the majority of parasitic nematodes)

Nematoda > Secernentea

What larval stage is the infective stage in the Secernentea class of nematodes?

3rd-stage larva

Name this order of Nematodes otherwise known as Bursates

Nematoda > Secernentea > Strongylida (bursates)

Strongylida: Typical morphologic features

Males typically have a pronounced copulatory bursa (hence the name bursates)

Large buccal capsules for strongyloids and ancylostomatoids

Describe the Spicules of Male Strongyloids and Ancylostomatoids

Spicules are long and thin

Describe the Spicules of Trichostrongyloidea

Spicules are short and stout

Describe morphological characteristics of Strongylida eggs

typical strongyle-type eggs → smooth, elliptical egg with a morulated embryo

Where do 1st, 2nd and 3rd stage Strongylida larva live?

1st and 2nd stage larvae live in feces

3rd stage larvae migrates out of feces to then be ingested by host

Name this family of nematodes (scientific and common names)

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms)

Where do Trichostrongylida live and in what hosts?

Common in grazing ruminants, also in swine, horses, cats, and birds

Typically in abomasum and small intestine (exceptions exist)

Where do Dictyocaulus spp. live in host?

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Dictyocaulus

Exception to typical Trichostrongylida where live in abomasum and small intestine, Dictyocaulus live in the lungs

How is a Trichostrongylida infection diagnosed?

Diagnosis: Strongyle-type eggs on fecal flotation

How is a Dictyocaulus infection diagnosed (differs from other typical Trichostrongylida)?

Baermann technique

Name this Threadworm

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Trichostrongylus

Small worms, very reduced buccal cavity

Short, twisted, pointed spicules

The diarrhea in this sheep is caused by what nematode infection?

Trichostrongylus

Typically asymptomatic, but high numbers can cause diarrhea in sheep, goats, and cattle → Feces on fleece can attract blowflies, leading to myiasis

How does host acquire Trichostrongylus infection? Diagnosis?

Infective third-stage larvae survive winter on pasture, ingested in spring

Diagnosis: Strongyle-type eggs in feces

Trichostrongylus axei: where live and in what host?

Stomach or abomasum of horses and ruminants

Pictured is the tail of what Threadworm?

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Ostertagia, Teladorsagia

annulated tail tip

Threadworms Ostertagia and Teladorsagia are related species, but differ in their hosts. What is each one’s host?

Teladorsagia in sheep and goats, Ostertagia in cattle

Teladorsagia/Ostertagia: morphological cahracteristics

Small brownish worms with short buccal cavity, annulated tail tip in females

Short, three-pronged spicules

Where do Ostertagia/Teladorsagia adults live in their respective hosts?

In the abomasum (Ostertagia in cattle, Teladorsagia in sheep)

How are Ostertagia/Teladorsagia infections acquired?

Third-stage larvae survive winter on pasture, ingested in spring

This “Moroccan leather” appearance of abomasal mucosa on necropsy is due to what nematode infection?

Ostertagia (ostertagiasis)

Type 1 Ostertagiasis

Ostertagia infection in cattle

Also called Summer Ostertagiasis

Young pastured cattle acquire the infection in the spring

Clinical signs: diarrhea, anemia, hypoproteinemia, emaciation

Typically in young calves

Type 2 Ostertagiasis

Ostertagia infection in cattle

Also called Winter Ostertagiasis

Acquired larvae encyst in mucosa and emerge in late winter

Clinical signs: diarrhea, anemia, hypoproteinemia, emaciation

Typically in young calves

Identify this threadworm: the defining morphological characteristic?

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Haemonchus

White uterus spirals around blood-filled gut in females → Barber-pole appearance

Where do Haemonchus adults live?

Live as adults in abomasum of ruminants

Haemonchus: Disease

Disease: Anemia, weakness, shortness of breath, submandibular edema (bottle jaw), can be fatal

This test is useful for diagnosing what?

FAMACHA chart used to assess mucous membrane pallor

Aids diagnosis of anemia due to Haemonchus infections

Name this test and what is diagnoses

Peanut agglutination test

Haemonchus eggs

Haemonchus: treatment

Treatment: benzimidazoles (fenbendazole, albendazole), macrocyclic lactones (ivermectin, moxidectin), levamisole, morantel tartrate

Resistance to many drugs reported

Pictured is a Nematode egg that is much larger than other strongyle-type eggs. Identify the species

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Nematodirus

Diagnosis: Eggs much larger than other strongyle-type eggs

Nematodirus battus: infective stage development?

Nematodirus battus larvae develop to infective third stage in egg, then hatch after a period of winter freezing

When do Nematodirus battus infections typically occur?

Single wave of infection and disease each spring

Second wave can occur in the fall

Nematodirus: Disease

Typically asymptomatic

Nematodirus battus can cause severe diarrhea and death

Identify these threadworms

Nematoda > Secernentea > Strongylida (bursates) > Trichostrongylida (threadworms) > Dictyocaulus

Long, white worms with small buccal cavity

Short, granular spicules, reduced bursa

Where do Dictyocaulus adults live and in what hosts?

Live as adults in the respiratory tract of ruminants and horses, first-stage larvae passed in eggs often hatch before passing into feces

Name the host for Dictyocaulus viviparus

Cattle

Name the host for Dictyocaulus filaria

Sheep

Name the host for Dictyocaulus arnfieldi

Equids

Dictyocaulus: Disease

Disease: Chronic bronchitis, bronchial tree occlusion, atelectasis

(Pictured is a calf lung infected)

Dictyocaulus: Diagnosis

Diagnosis: First stage larvae in feces detected via Baermann method

Eggs occasionally found on fecal flotation, but usually hatch rapidly

Dictyocaulus: Treatment

Treatment: Macrocyclic lactones (ivermectin, doramectin, moxidectin, eprinomectin), benzimidazoles (fenbendazole, albendazole, oxfendazole), levamisole

Vaccine available

Premunition

The phenomenon where the host is more resistant to a parasite after an initial acute infection has become chronic

A stable adult population of nematodes inhibits further infection or maturation of additional larvae

Spring Rise

Increased number of eggs are passed in feces right before spring

Periparturient rise

Increased number of eggs are passed in feces right before giving birth

Refugia

A population of nematodes that remain unexposed to treatment, decreasing selection pressure on the nematode population as a whole

Resistance to ivermectin, benzimidazoles, and levamisole/morantel reported in many nematode species

Identify the suborder of Bursates (Strongylida) that show this characteristic of large buccal cavities

Nematoda > Secernentea > Strongylida (bursates) > Strongyloidea