NEMATODES
Introduction
• The medically important nematodes can be divided into two categories
according to their primary location in the body, namely, intestinal and tissue
nematodes.
• The intestinal nematodes include Enterobius (pinworm), Trichuris (whipworm),
Ascaris (giant roundworm), Necator and Ancylostoma (the two hookworms),
Strongyloides (small roundworm), and Trichinella.
• Enterobius, Trichuris, and Ascaris are transmitted by ingestion of eggs; the others
are transmitted as larvae
Introduction
• General characteristics:
Also known as Intestinal Roundworms,
elongated, cylindrical worms
Not segmented
Equipped with digestive, reproductive, excretory and nervous system
Male are smaller than female
Life cycle consists of three morphological forms: ova, larvae (juvenile
worms), and adult
 Organism specific






ENTEROBIUS
Disease: Enterobius vermicularis causes pinworm infection Enterobiasis
LIFE CYCLE:
• The life cycle is confined to hu m ans
• The infection is acqu ired by ingesting the worm eggs
Common name – Pin worm, seatworm, society worm
• The adu lt m ale and fem ale worm s live in the colon, where m ating oc c u rs
Infective stage – embryonated egg
Final host – man
MOT – ingestion and inhalation
Habitat
–large
intestine
(caecum)
• Rei nf ecti on can occu r i f they are c arri ed to the mou th b y f i ng ers af ter sc ratc hi ng the i tc hi ng ski n
EGG OF E. VERMICULARIs
•It is colorless.
•Oval
in
shape
and
flattened on one side.
•Contains a larva
usually
•Left: Adhesive tape preparation showing eggs of
E. vermicularis recovered from anal skin.
•Right: E. vermicularis egg in feces
1. Albendazole – drug of choice.
2. Mebendazole
3. Pyrantel Pamoate
Familial disease. It is very
contagious, can easily spread
among family members or
institutions.
It can cause autoinfection and
retro-infection – it goes to skin
and back to rectum
ENTEROBIUS
Disease: Enterobius vermicularis causes pinworm infection Enterobiasis
PATHOGENESIS &
CLINICAL FINDINGS
• Pe rianal pru ritu s is the m os t prom ine nt
sym ptom
• Pru ritu s is thou ght to be an allergic
re ac tion to the presenc e of eithe r the adu lt
fem ale or the eggs
• Scratching predisposes to secondary
bac terial infec tion and insom niA
LABORATORY DIAGNOSIS
• The e ggs are re c ove re d from pe rianal
s kin by u s ing the S c otc h tape te c hniqu e
and can be observed m ic ros c opic ally
• U nlike those of other intes tinal
ne m atode s , the s e e ggs are not fou nd
in the s tools
• T h e sm all, w h i t i sh adu lt w orm s can b e
fou n d i n th e stools or n e ar th e an u s of
di ap e re d ch i ldre n
ENTEROBIUS
Disease: Enterobius vermicularis causes pinworm infection Enterobiasis
LABORATORY DIAGNOSIS
Graham’s scotch adhesive tape swab
(Perianal cellulose tape swab) – provides the
highest percentage of positive results.
• T h e sm all, w h i t i sh adu lt w orm s can b e
fou n d i n th e stools or n e ar th e an u s of
di ap e re d ch i ldre n
Pinworm prevention and control
measures
practicing proper personal hygiene applying ointment or salve to the infected
perianal area to prevent egg dispersal; avoiding scratching the infected area;
thorough cleaning of potentially infected environmental surfaces, including
linens; and treating all household members.
TRICHURIS
Disease: Trichuris trichiura causes whipworm infection trichuriasis
Common name: whipworm
INFECTIVE STAGE: EMBRYONATED EGG
FINAL HOST: MAN
MODE OF TRANSMISSION: INGESTION
HABITAT: LARGE INTESTINE
EGG OF T.TRICHIURA
• It is yellow-brown
Hyaline polar plug at each end; football
• Has a characteristic barrel shape with a
colorless protruding mucoid plug at each
end
• Contains a central granular mass which is
the unsegmented ovum
1. Mebendazole – drug choice
2. Albendazole – alternative drug
TRICHURIS
LIFE CYCLE:
become infective in 15 to 30 days
TRICHURIS
Disease: Trichuris trichiura causes whipworm infection trichuriasis
PATHOGENESIS &
CLINICAL FINDINGS
• A l tho u gh a du l t Tri c h u ri s w o rms b u rro w th e i r h a i rl i k e a nte ri o r
e nds i nto the i nte sti n a l mu c o sa , th e y d o n o t c a u se si gni fi c a nt
a ne mi a , u nl i k e the ho o k w o rms
• Tric hu ris m ay c au se diarrhea, bu t m os t
infec tions are asym ptom atic
•Trichu ris m ay also cau se rectal prolapse
in c hildren with heavy infec tion
LABORATORY DIAGNOSIS
•Diagnosis is bas ed on finding the
typic al e ggs , i. e . , barre l -s hape d
(lem on -shaped) with a plu g at eac h end,
in the s tool
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
•H u ma n s a re i n f e cte d b y i n g e s ti n g worm e g g s i n f ood or wa te r con tami n ated wi th h u man f eces
•Th e e ggs h atch i n th e s mall i n te s ti n e , & th e lar v ae mi gr ate th r ough th e gut wall i n to th e blood s tr e am & th e n
to th e lun gs
• A. lumbr icoid es is known as the " gi ant r ound wor m." Thous and s of eggs ar e laid d aily, ar e
passed in The f eces, & d i f f er enti ate i nto embr yonated eggs i n war m, moist soil
Common name – Giant intestinal worm/round worm
Infective stage – embryonated egg
Final host – man
MOT – ingestion/fecal-oral route
Habitat – small intestine
Ascaris suum - pigs
EGGS OF A. LUMBRICOIDES
FERTILIZED EGG
•Yellow-brown, oval or round
•Shell is often covered by an uneven albuminous
coat
•Contains a central granular mass which is the
unsegmented fertilized ovum.
Decorticated egg:
•This term is used to describe an egg that has no
albuminous coat. A decorticated egg has a
smooth shell and appears pale yellow or
colorless.
INFERTILE EGG
•It is darker in colour and has a thinner wall
•and more granular albuminous covering.
•More elongated than af ertilized egg
•Contains a central mass of large granules.
• Usually fertilized eggs are found in feces but
occasionally infertile eggs are produced by unfertilized
female worms.
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
PATHOGENESIS & CLINICAL FINDINGS
LABORATORY DIAGNOSIS
• The ma j o r da ma ge o c c u rs d u ri n g l a rva l mi g ra ti o n ra the r tha n fro m the
p re se nc e o f the a d u l t w o rm i n the i nte sti ne
• Th e p r i n c ip al si te s o f ti ssu e r e a c ti on a r e th e l u n g s , w h e r e
i n f la mma tion wi th a n e o si nop hilic e x u da te o c c u r s i n r e sp onse t o
l a r v a l a n ti gens
• Diagnos is is u s u ally m ade
m ic ros c opic ally by de te c ting e ggs in
the s tools
• Beca us e the adults derive their nourishm e nt from ingested food, a heavy
worm burde n may contrib ut e to malnut rit io n , espec i a l ly in childre n in
develo pi ng countri es
• Occa s ion ally, t h e pa t ie nt s e e s a d u lt w or ms in t h e
s t ool s .
• Mo st i nfe c ti o ns a re a sy mp to ma ti c
• A sc a r i s p n e u m o nia wi th f e v e r , c o u gh , & e o si n o p hi l ia c a n o c c u r w i t h
a h e a v y lar v al b ur de n
• Abdom i n al pai n an d ev en obs t r uct i on can r es ul t f r om t h e pr es en ce oF
adul t wor m s i n t h e i n t es t i n E
1. Albendazole – drug of choice.
2. Mebendazole
3. Pyrantel Pamoate
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
LABORATORY DIAGNOSIS
A. Stool exam
PATHOGENESIS
&
CLINICAL
FINDINGS
1. Direct fecal smear – less sensitive
• The ma j o r da ma ge o c c u rs d u ri n g l a rva l mi g ra ti o n ra the r tha n fro m the
p re se–
nc qualitative
e o f the a d u l t w o rmdiagnosis
i n the i nte sti ne
2. Kato-thick
Th e p r i n c ip al si–
te squantitative
o f ti ssu e r e a c ti on adiagnosis
r e th e l u n g s , w h e r e
3.•Kato-katz
i n f la mma tion wi th a n e o si nop hilic e x u da te o c c u r s i n r e sp onse t o
l a r v a l a n ti gens
Beca us e the adults derive techniques
their nourishm e nt from ingested food, a heavy
B.• Concentration
worm burde n may contrib ut e to malnut rit io n , espec i a l ly in childre n in
• Occa s ion ally, t h e pa t ie nt s e e s a d u lt w or ms in t h e
pi ng countri
es
1.develo
FECT
– Fomalin
ether/ethyl Concentration Technique
s t ool s .
Mo st i nfe c ti o ns a re Iodine
a sy mp to ma tiFormaldehyde
c
2. MIFCT – •Merthiolate
Concentration Technique
3.• A scBrine
a r i s p n efloatation
u m o nia wi th f e v e r , c o u gh , & e o si n o p hi l ia c a n o c c u r w i t h
a h e a v y lar v al b ur de n
1. Albendazole – drug of choice.
4. Zinc Sulfate floatation technique
2. Mebendazole
3. Pyrantel Pamoate
C. X-ray (extraintestinal ascariasis to lungs) D. CBC (demonstrate
eosinophilia)
• Abdom i n al pai n an d ev en obs t r uct i on can r es ul t f r om t h e pr es en ce oF
adul t wor m s i n t h e i n t es t i n E
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
LABORATORY
DIAGNOSIS
PATHOGENESIS & CLINICAL FINDINGS
• The ma j o r da ma ge o c c u rs d u ri n g l a rva l mi g ra ti o n ra the r tha n fro m the
p re se nc e o f the a d u l t w o rm i n the i nte sti ne
• Th e p r i n c ip al si te s o f ti ssu e r e a c ti on a r e th e l u n g s , w h e r e
i n f la mma tion wi th a n e o si nop hilic e x u da te o c c u r s i n r e sp onse t o
l a r v a l a n ti gens
• Beca us e the adults derive their nourishm e nt from ingested food, a heavy
worm burde n may contrib ut e to malnut rit io n , espec i a l ly in childre n in
develo pi ng countri es
• Occa s ion ally, t h e pa t ie nt s e e s a d u lt w or ms in t h e
s t ool s .
• Mo st i nfe c ti o ns a re a sy mp to ma ti c
• A sc a r i s p n e u m o nia wi th f e v e r , c o u gh , & e o si n o p hi l ia c a n o c c u r w i t h
a h e a v y lar v al b ur de n
• Abdom i n al pai n an d ev en obs t r uct i on can r es ul t f r om t h e pr es en ce oF
adul t wor m s i n t h e i n t es t i n E
1. Albendazole – drug of choice.
2. Mebendazole
3. Pyrantel Pamoate
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
LABORATORY DIAGNOSIS
A. Stool exam
PATHOGENESIS
&
CLINICAL
FINDINGS
1. Direct fecal smear – less sensitive
• The ma j o r da ma ge o c c u rs d u ri n g l a rva l mi g ra ti o n ra the r tha n fro m the
p re se–
nc qualitative
e o f the a d u l t w o rmdiagnosis
i n the i nte sti ne
2. Kato-thick
Th e p r i n c ip al si–
te squantitative
o f ti ssu e r e a c ti on adiagnosis
r e th e l u n g s , w h e r e
3.•Kato-katz
i n f la mma tion wi th a n e o si nop hilic e x u da te o c c u r s i n r e sp onse t o
l a r v a l a n ti gens
Beca us e the adults derive techniques
their nourishm e nt from ingested food, a heavy
B.• Concentration
worm burde n may contrib ut e to malnut rit io n , espec i a l ly in childre n in
• Occa s ion ally, t h e pa t ie nt s e e s a d u lt w or ms in t h e
pi ng countri
es
1.develo
FECT
– Fomalin
ether/ethyl Concentration Technique
s t ool s .
Mo st i nfe c ti o ns a re Iodine
a sy mp to ma tiFormaldehyde
c
2. MIFCT – •Merthiolate
Concentration Technique
3.• A scBrine
a r i s p n efloatation
u m o nia wi th f e v e r , c o u gh , & e o si n o p hi l ia c a n o c c u r w i t h
a h e a v y lar v al b ur de n
1. Albendazole – drug of choice.
4. Zinc Sulfate floatation technique
• Abdom i n al pai n an d ev en obs t r uct i on can r es ul t f r om t h e pr es en ce oF
adul t wor m s i n t h e i n t es t i n E
2. Mebendazole
3. Pyrantel Pamoate
ASCARIS
Disease: Ascaris lumbricoides causes ascariasis
LABORATORY
DIAGNOSIS
PATHOGENESIS & CLINICAL FINDINGS
C. X-ray (extraintestinal ascariasis to lungs) D. CBC (demonstrate eosinophilia)
• The ma j o r da ma ge o c c u rs d u ri n g l a rva l mi g ra ti o n ra the r tha n fro m the
p re se nc e o f the a d u l t w o rm i n the i nte sti ne
• Th e p r i n c ip al si te s o f ti ssu e r e a c ti on a r e th e l u n g s , w h e r e
i n f la mma tion wi th a n e o si nop hilic e x u da te o c c u r s i n r e sp onse t o
l a r v a l a n ti gens
• Beca us e the adults derive their nourishm e nt from ingested food, a heavy
worm burde n may contrib ut e to malnut rit io n , espec i a l ly in childre n in
develo pi ng countri es
• Mo st i nfe c ti o ns a re a sy mp to ma ti c
• A sc a r i s p n e u m o nia wi th f e v e r , c o u gh , & e o si n o p hi l ia c a n o c c u r w i t h
a h e a v y lar v al b ur de n
• Abdom i n al pai n an d ev en obs t r uct i on can r es ul t f r om t h e pr es en ce oF
adul t wor m s i n t h e i n t es t i n E
• Occa s ion ally, t h e pa t ie nt s e e s a d u lt w or ms in t h e
s t ool s .
ANCYLOSTOMA & NECATOR
Disease: Ancylostoma duodenale (Old World hookworm) & Necator americanus (New World
hookworm) cause hookworm infection
Necator Americanus – Human hookworm, New world hookworm
Ancyclostoma braziliense -Cat hookworm
Ancyclostoma caninum– Dog hookworm
Ancyclostoma duodenale– Human hookworm, Old world hookworm
Habitat: small intestine
Diagnostic stage: ova
Infective stage: L3 larva
EGG OF HOOKWORM(N.AMERICANUS OR
A.DUODENALE)
• Note: If the specimen is more than 12 hours old,
a larva may be seen inside the egg
• If the feces is more than 24 hours old, the larva
may hatch and must then be differentiated
from a Strongyloides larva
• LEFT: SEGMENTED. •
• Right: Embryonated
•
A
N
C
Y
L
O
S
T
O
M
A
&
N
E
C
A
T
O
R
L
I
F
E
c
y
c
l
e
ANCYLOSTOMA & NECATOR
Disease: Ancylostoma duodenale (Old World hookworm) & Necator americanus (New World
hookworm) cause hookworm infection
PATHOGENESIS & CLINICAL FINDINGS
• The major damag eis du e to the loss of b looda t the s ite of
attachmen t in the small intestine. Up to 0.1 to 0.3 mL per worm
can b e lost per day
1.Creeping eruptions or Cutaneous Larval Migration (CLM) - extraintestinal larval migration or due to skin
penetration
1.DUE TO ADULT: epigastric pain, diarrhea, malnutrition, severe anemia-microcytic, hypochromic type, IDA
•"
1.DUE TO LARVA: WAKANA Disease - pneumonitis coolic itch, dew itch, ground itch.
• Pneumonia with eosinophilia can be seen during larval
migration through the lungs
ANCYLOSTOMA & NECATOR
Disease: Ancylostoma duodenale (Old World hookworm) & Necator americanus (New World
hookworm) cause hookworm infection
LABORATORY DIAGNOSIS
1. Stool exam - DFS
2. Culture technique: Harada Mori Technique
• D i a g n os i s i s m a d e m i c r o s c o p ic ally
by o bs e r v i n g t h e e g g s i n t h e s t o o ls
• Occult blood in the stools is frequent
• Eosinophi li a i s t y pi c al
Mebendazole, Albendazole
STRONGYLOIDES
Disease: Strongyloides stercoralis causes strongyloidiasis
• S . s tercorali s h as two di s ti n ct li f e cycles , on e wi th i n th e h u man body & th e oth er f ree - li vi n g i n th e s oi l
Strongyloides stercoralis Common name: thread worm
FH: man
Habitat: small intestine
Diagnostic stage: Rhabditiform (L1)
larva Infective stage: L3
Source of infection: STH
FEMALES ARE CAPABLE OF PARTHENOGENESIS
Favorable conditions: Free-living
Unfavorable conditions: Parasitic
STRONGYLOIDES (LIFE CYCLE)
STRONGYLOIDES
Disease: Strongyloides stercoralis causes strongyloidiasis
PATHOGENESIS & CLINICAL FINDINGS
• M o s t p at i e nt s ar e as y m p tom atic, e s p e cially t ho s e
w i t h a l o w w o r m bu r d e n
• Ad u l t f e m al e w o r m s i n t he w al l o f t he s m al l i nt e s tine
can cau s e i nfl amm ation, r e s u lting i n wat e r y d i ar r hea
• In aut oinfect ion, t he penet r at ing l ar v ae may caus e s ufficient
damage t o t he int es t inal mucos a t hat s eps is caus ed by ent er ic
bact er ia can occur
• Larvae in the lungs can produce apneumonitis similar to that
caused by Ascaris
• Pruritus can occur at the site of larval penetration of
the skin, as with hook worm
1. Cochin China Diarrhea or Vietnam
Diarrhea
2. Honey comb ulcer
3. Skin allergy due to larval penetration 4.
Larval migration --> pneumonia
LARVA OF
S.STERCORALIS
• Larva of S.
stercoralis as seen
with 10x objective
S.STERCORALIS vs.
hOOkwOrm
S.STERCORALIS vs.
hOOkwOrm
STRONGYLOIDES
Disease: Strongyloides stercoralis causes strongyloidiasis
A.
B.
C.
D.
Stool Exam >Direct Fecal Smear
>Kato-thick
>Kato-katz
Concentration techniques
LABORATORY DIAGNOSIS
• D i a g n o s i s d e p e n d s o n f i n d i n g la r v a e ,
r a th e r th a n e g g s , i n th e s to o l
• As with many nematode infections in
which larvae migrate through tissue,
eosinoph il ia can be striking
Mebendazole, Albendazole, Thiabendazole
Trichinella
capillaria
capillaria
NEMATODES
Wuchereria bancrofti
Brugia malayi
Brugia timori
Loa loa
Mansonella spp.
Onchocerca volvulus
Dirofilaria spp.
VECTORS
Mosquitos(Anopheles, Culex,
Aedes)
Mosquitos(Anopheles, Culex,
Aedes)
Mosquitos(Anopheles, Culex,
Aedes)
Chrysops or Mango fly
Culicoides gnats of bitting midges
Black fly of buffalo gnat
Blackflies