NEMATODES(ROUND WORMS)

1. Intestinal nematodes
2. Tissue Nematodes
Ascaris
lumbricoides
Life cycle of A.
lumbricoides
Infertile egg of A.
lumbricoides

It is darker in
colour and has
a thinner wall
and more
granular
albuminous
covering.
● More
elongated than
a fertilized egg,
measuring
about 9045m.
● Contains a
FERTILIZED EGG
FERTILIZED
EGG
● Yellow-brown,
oval or round,
measuring
50–70m long
by 30–50m
wide.
● Shell is o en
covered by an
uneven
albuminous
coat
Fertilised ova of Ascaris
lumbricoides
Decorticated fertilised ova of Ascaris
lumbricoides
Decorticate
d egg has
no
albuminous
coat, has a
smooth
shell and
appears
pale yellow
or
colourless.
Forms of Ascaris
lumbricoides ova.
ADULT ASCARIS
LUMBRICOIDES
Freshly expelled
Ascaris worms are
pinkish in colour
with an appearance
similar to
earthworms. They
measure 12–35 cm
in length and taper
at both ends.
The tail of the male
is curved and has
small rod-like
projections
(spicules). There is
a small mouth
surrounded by
Adult worm (Ascaris
lumbricoides)
Trichuris trichura/ whipworm
Adult worm of Trichuris
trichiura
Ova of Trichuris
trichiura
Enterobius
vermicularis/
Pinworm
Adult worm (Enterobius
vermicularis)
Scotch tape
technique
Egg of E. vermicularis
● It is colourless.
● Oval in shape and usually
flattened on one
side. It measures about 5530m.
● Contains a larva.
Hookworms
Adult male and female
hookworm
Posterior
end of
Adult
hookworm
NB:
Copulatory
ducts-
pointed blue
Posterior
female end
Anterior end : Le Ancylostoma
duodenale with teeth
 Eggs of
Hookworm spp.

Hookworm eggs. Le : Segmented.

It is colourless with a thin shell which appears
microscopically as a black line around the ovum.
● Oval in shape, measuring about 6540m.
● Contains an ovum which appears segmented (usually 4–8
cell stage).
Right: Embryonated. Found in specimen more than 12
hours
Strongyloides
stercolaris
Larvae and ova of Strongyloides
stercolaris
Larvae of Strongyloides
stercoralis
Harada Mori Filter Paper Strip Culture
The test detects light infection with
hookworm, S. stercoralis,
Trichostrongylus spp., as well as to
facilitate species identification of
helminths.
The Harada-Mori culture method
uses strips of filter
paper on which feces is smeared in
 Cont
….
The paper strips are kept in conical
centrifuge tubes with water at the
bottom, in which the strips dip. The
tubes are kept at room temperature in
the dark for 7–10 days, during which
time the larvae develop and fall into
the water at the bottom, from which
Harada Mori method
of stool culture is
carried out to
demonstrate third
stage filariform larvae
which helps in
distinguishing
hookworm larvae and
Strongyloides larvae
forms
Trichinella spirallis
Larvae of Trichinella
spiralis
Larvae of Trichinella
spiralis
Drancuculus
medinensis/
Fish tapeworm
Life cycle of D.
medinensis
Dracunculus
medinensis
Dracunculus
medinensis
Filarial worms
 Lymphatic filariasis
i. Wuchereria bancro i
ii. Brugia malayi
iii. Brugia timori
Vectors
Anopheles, Mansonia and
Culex quinquefasciatus
Wuchereria
bancro i
Lab
diagnosis

Tail of W.
bancro i.
No nuclei in
tip
NOW ICT
Filariasis test.
Positive test: Two pink lines
T (Test) and C (Control) in
viewing window.
Negative test: Single pink
line C (Control) in viewing
window.
Lower limb
elephantiasis
HYDROCELE
 Anopheles mosquito

Vector of
⚫ Malaria
⚫ Bancroftian and brugian filariasis
⚫ Arboviruses
Identification features
⚫ Brown
⚫ One edge of wing spotted
alternating white and brown colours
 Aedes mosquito
Vector of
⚫ Bancroftian filarisis
⚫ Yellow fever
⚫ Arboviruses(Yellow fever),
Riftvalley fever,Chikungunya)
Identification
⚫ Black
⚫ Adults are ornate with
patterned legs,thorax and
abdomen
⚫ Wings not spotted
SUBCUTANEOUS
FILARIASIS
Loa Loa/African eye worm
Intermediate host:
Chrysops fly
Tail of L.loa. Nuclei extend to
tip of tail
Onchocerca
Volvulus
Intermediate hosts: Day-biting
female black flies of the genus
Simulium (black flies).
Onchocerca volvulus microfilariae

The microfi lariae

are unsheathed
and non-periodic.
They measure
about 300 by 0.8
μm.
Tail: No nuclei in
the end of the tail
which is long and
pointed.
Eggs are mostly
laid in
flowing water
Hanging
groin
Hanging
groin
LEOPARDS’
SKIN
Mansonella spp
i. M. perstans
ii. M.ozzardi
iii. M.Streptocerca
M. Perstans
Intermediate host/ vector; Culicoides

NB: Hump back,

beaded antennae
Microfilariae of Mansonella
perstans

Unsheathed, nuclei extend to the

end of the tail
 CESTODES

COMMON NAME (TAPEWORMS)

Taenia ssp
Taenia spp life cycle
Laboratory
diagnosis
Scolex of Taenia saginata:
No hooklets
and Taenia solium: 2 rows
of hooklets
ADULT
TAENIA SPP.
ADULT TAENIA
WORM.
PROGLOTTIDS OF
Ploglotid of T. saginata NB: >13
uterine branches
PROGLOTID OF TAENIA Solium NB: <12
uterine branches.
Diphylobothriu
m latum
Life cycle of D.
latum
Adult D. latum
D.LATUM EGG ( NB.
THE
OPERCULUM)
● It is yellow-brown
and oval in
shape,
measuring about
7045m.
● Has an operculum
(lid) which
is usually
difficult to see.
● Contains a mass of
granulated
yolk cells surrounding
an
undeveloped ovum.
Hymenolepis
nana/ Dwarf tape
worm
Life cycle of
H. nana
Adult Worm
H. nana is the smallest
intestinal cestode that infects
man. It is 5–45 mm in
length and less than 1 mm
thick. The
scolex has 4 suckers and a
retractile rostellum with a
single row of hooklets
Egg of H.nana It is
colourless, oval or
round, measuring
30–45m in diameter.
● Hooklets are present
in the embryo. Careful
focusing is necessary
to see the three pairs
of hooklets.
● At each end of the
egg, thread-like
structures
called polar filaments
are usually
visible.
Hymenolypis
diminuta/
Rat tapeworm
H. diminuta is a tapeworm
normally parasitic in
rodents, with fleas and insects
serving as
Intermediate hosts. Very occasionally
humans
become accidentally infected by
swallowing
an intermediate host.Life cycle of
H.
diminuta is similar to that of H.
nana
Egg of H. diminuta
● It is yellow-brown, round to oval,
Echinococcus
granulosus/
dog tapeworm
LIFE CYCLE of E.
granulosus
Laboratory diagnosis
Laboratory investigations include:
-Testing serum for antibodies produced in
response to infection and where available,
testing for cystic fluid antigens.
-Examining cyst fluid for brood capsules,
protoscoleces and hooks following the
surgical removal of a cyst or fine needle
aspiration under ultrasound guidance.
Adult worm of E.
granulosus
Adult E. granulosus
The neck is short than the
rest of the worm (3 mm ×
6 mm).
The strobila is composed
of only 3 proglottids, the
anterior immature, the
middle mature, and the
posterior
gravid segment.
The terminal proglottid is
longer and wider than the
rest of the worm and
contains a branched uterus
filled with eggs.
Eggs
Indistinguishable from
Adult worm (Echinoccocus
granulosus)
Larval Form of E. granulosus
The larval form is found within the hydatid
cyst developing
inside various organs of the intermediate
host.
It represents the structure of the scolex of
adult worm
and remains invaginated within a
vesicular body.
A er entering the definitive host, the
EVAGINATED PROTOSCOLEX (NB.
THE HOOKLETS)
INVAGINATED
PROTOSCOLECES
Hydatid cyst
HYDATID
CYST.
Hydatid cysts of the
liver