Nematodes and Parasite Identification: Key Morphology and Life Cycle Facts

True or False: all nematodes are parasites.

False - many nematodes are free-living.

Ascaris suum is commonly called the _____ worm.

Pig worm.

Shape of Tetrameres?

Spherical.

Shape of Trichuris?

Whiplike.

Outermost nematode layer derived from hypodermis?

Cuticle.

Cervical alae location?

Flattened extensions at anterior end.

Caudal alae location?

Flattened extensions at posterior end of males.

Other name for caudal alae?

Copulatory bursa.

Function of bursa rays + which sex has them?

Hold female during mating; only males.

Chitinous spicule = nematode __________.

Penis.

Function of somatic muscle layer?

Locomotion (movement).

Function of muscles in pseudocoelom?

Movement related to feeding & reproduction.

Two most important internal organ systems of nematodes?

Reproductive and digestive.

Female nematodes have a __________; males have a __________.

Rectum; cloaca.

Cloaca is common outlet for...?

Feces, urine, reproductive products.

Nematodes are dioecious - meaning?

Separate sexes (male & female).

True or False: Female nematodes are generally larger than males.

True.

Tube connecting testes to cloaca?

Vas deferens.

Tube connecting ovaries to uterus?

Oviduct.

Nematode exception to high egg output?

Whipworms (Trichuris spp.) - few eggs every 3 days.

Ascarid egg description + example.

Single-cell stage, oviparous; Toxocara canis.

Trichostrongyle egg description + example.

Morula (multicellular), oviparous; Ancylostoma caninum.

Spirurid egg description + example.

First-stage larva inside shell, ovoviviparous; Spirocerca lupi.

Trichurid egg description + example.

Single-cell stage, oviparous; Trichuris vulpis.

Oviparous

eggs that contain single cell or multi-cell (morula) stage inside the shell 

Ovoviviparous

eggs that contain the first stage larva inside the shell 

Larviparous

female retains the egg in the uterus, then gives birth to live larvae 

What is molting in nematodes?

Shedding of cuticle to progress larval stages.

Most infective larval stage?

stage 3

Direct life cyle

does not go through intermediate host, meaning that they’ll develop in the soil to the third stage then infect the host from the foot or skin then migrate to their infection cite 

Direct life cyle example

hookworm

Indirect life cycle

goes through the intermediate host, meaning that the develop in like a mosquito get up to the third stage in the exention of the mosquito (the mouth) then infect the host while the mosquito is feeding 

Indirect life cycle example

heartworm

Step 1 in parasite ID under microscope?

Identify sample (blood, fecal, skin scraping, tissue).

Fecal sample structures you may see?

Egg, larva, proglottid, oocyst.

Example of Schistosoma stage.

Egg.

Example of Strongyloides stercoralis stage.

Larva.

Example of Dipylidium caninum stage.

Proglottid.

Example of Eimeria stage.

Oocyst.

Host species for parasite ID?

Canine, feline, ruminant, swine, equine.

Morphology terms to recognize in parasite structures?

Single-cell, morulated, larvated, operculum, egg packets, plugs, hexacanth, micropyle, polar cap.

Flatworm groups?

Flukes, tapeworms.

Roundworm groups?

Whipworms, threadworms, thorny-headed worms.