Example Infective
stage
Route(s)
of infection
Intermediate
host
Paratenic
host
Family:
Trichostrongylidae
L3 Oral No No
Family:
Ancylostomatidae
- the "hookworms"
L3 Oral,
Skin
No Yes, in
some species
Families:
Metastrongylidae
Protostrongylidae
- the "lungworms"
L3 Oral Yes No
The ascarids
Fam: Ascaridae
Ascaris
Parascaris
Toxocara




(Egg+L2)

(Egg+L2)
(Egg+L2)
hatched L2
L3



Oral

Oral

Oral

Oral
Oral



No

No

No

No
No



Yes

No

No

Yes
No
Family:
Oxyuridae
(Egg+L3) Oral No No
Family:
Onchocercidae
L3 Skin Yes No