Helminth Eggs

The morphology and location of helminth eggs are a valuable aid to the diagnosis of specific helminth diseases.

1) Platyhelminthes - Digeneans

Digenean Flukes - These eggs are rounded, with thin shells, an operculum, which opens as the larvae (a miracidium) hatches. An important exception to this is the eggs of the schistosomes.

Fasciola hepatica	Paragonimus westermani	Opisthorchis

The Schistosomes - These eggs are thin walled and contain a miracidium larvae, as with other digeneans, but in this case do not have an operculum, (the egg splitting open laterally), and are usually equipped with a spine or other similar ornament.

S.mansoni - Eggs have lateral spines.	S.japonicum - Eggs have very reduced terminal spines.	S. haematobium Eggs have terminal spines.	S.intercalatum- Eggs have terminal spines.

2) Eucestodes

Pseudophyllideans - These are similar in appearance to the eggs of digeneans such as Fasciola, with thin egg shells and an operculum. However, they do not contain a miracidium, but in this case a coracidium larvae.

Diphylobothrium latum

Cyclophyllideans - These eggs have characteristically thick egg shell walls, and contain an oncosphere larvae, equipped with three pairs of hooks.

Hymenolepis diminuta

3) Nematodes

Nematode eggs generally conform to the same pattern, with thin egg shells containing either an unembryonated mass of cells, or an L1 (or sometimes L2) larvae. There are however a few exceptions to this.

Hookworm Egg - Typical nematode egg	Trichuris trichuria - These have opercular plugs at either end of the egg shell.	Ascaris lumbricoides - These eggs have relatively thick egg shell walls