WORM INFECTION

1. Worm infection

2. Contents
• History
• Parasites
• Helminths
• Sources of infection
• Modes of infection
• Hookworm
• Tapeworm
• Bibliography

3. History
Archaeological evidence
It is assumed that early human ancestors generally
had parasites. Generally, the discovery of parasites in
ancient humans relied on the study of feces and
other fossilized material. There are claims
of evidence of hookworm eggs from around 5000BC
in Brazil. Tapeworm eggs have also been found
present in Egyptian mummies dating from around
2000BC, 1250BC, and 1000BC along with a well
preserved and calcified female worm inside them.

4. Written Evidence
The first written records of parasites date from
3000 to 400BC in Egyptian papyrus records. They
identify parasites such as round worms, guinea
worms , and some tapeworms of unknown varieties.
In ancient Greece,
Hippocrates and Aristotle documented several
parasites in their collection of works Corpus
Hippocraticum. The tapeworms were mentioned in a
play by Aristophanes as "hailstones“.

5. Parasites
Parasites are organisms that infect other living
beings. They establish themselves in or on the living
body of the host, being physically and physiologically
dependent for at least part of their life span i.e. they
obtain shelter and nourishment from the host. This
may or may not lead to disease in the host. Parasites
that live in complete harmony with the host, without
causing any damage are called commensals, those
which cause disease are termed as pathogens.

6. Parasites
Endoparasites Ectoparasites
Eg. Helminths,
nematodes
Eg. Lice, Ticks,
Mites

7. Helminths
Helminths are bilaterally symmetrical metazoa
belonging to the phyllum Scolecida.
The term helminth is derived from a Greek word
helmins that refers to worms

8. Helminths have an outer protective
covering [resistant to intestinal digestion]
known as cuticle or integument armed with
spines or hooks. The mouth may be provided
with teeth or cutting plates.
They do not possess organs of locomotion,
so locomotion is by muscular contraction &
relaxation.
They may be monoecious or dioecious .

9. Sources of infection
Soil
• Ingestion of Embryonated eggs
• Penetration of infective larvae into skin
Water
• Ingestion of infective form of parasite
• Ingestion of intermediate host
• Penetration into skin
• Entry through vulnerable sites

10. Food
• Contamination with human or animal
feces
• Meat containing infective larvae
Infective vectors
• Biological : mosquito, ticks,
• Mechanical : house flies
Animals
Cow, pig, fish, dog, etc

11. Other persons
• Carriers
• Patients
Self/ Autoinfection
• Finger to mouth
• Internal reinfection

12. Modes of infection
Oral Skin
Vector Direct

13. Hookworm
Anchylostoma duodenale
Necator americanus
Human
species
Hookworms have been known from very ancient
times. They have been mentioned in the Ebers papyrus
(1600 B.C.).

14. Morphology
Characteristic
• Shape
• Colour
• Structure
A. duodenale
• Stout,Cylindrical
• Pale pink /
greyish white
• Body is bent
with dorsal
aspect concave
and ventral
aspect convex,
anterior end is
constricted and
bent dorsally
N. americanus
• Smaller
• Anterior end is
bent opposite to
the general
curvature of the
body

15. Characteristic
• Male
A. duodenale
• 8-11 mm in
length, 0.4 mm
thick
• Posterior end is
expanded into
copulatory
bursa
• 2 long retractile
copulatory
spicules project
from the bursa
N. americanus
• 7-9 mm in
length, 0.3 mm
thick
• Copulatory
bursa is long
and wide
• The copulatory
spicules are
fused at the
ends to form
barbed tip

17. Characteristic
• Female
• Eggs
A. duodenale
• 10-13mm long,
0.6mm thick
• Hind is conoid,
subterminal
anus ventrally
• Vulva opens at
junction of
middle and
posterior thirds
• Oval or
elliptical,
colourless with
thin transparent
hyaline sheath
N. americanus
• 9-11mm long,
0.4mm thick
• Vulva opens in
front of the
middle
• Identical

18. Characteristic
• Buccal capsule
A. duodenale
• Has two pairs
of hook like
teeth ventrally
N. americanus
• Has two pairs
of semilunar
cutting plates
instead of teeth

19. Life cycle
• Stage 1 : passage of eggs from infected host
• Stage 2 : development of egg in soil
• Stage 3 : entrance into a new host
• Stage 4 : migration
• Stage 5 : localization and laying of eggs

21. Clinical manifestations
Skin:
• Local erythema
• Creeping eruption- reddish patch along the path
traversed
• Intense pruritis / ground itch (scratching which leads
to secondary bacterial infection)

22. Lung:
• Cough
• Wheezing
• Low grade temperature
• Eosinophilia
• Wakana disease (A disease, in which a persistent
asthmatic cough develops as the main symptom
complicated with vomiting or nausea)

23. Gastrointestinal:
• Epigastric pain
• Nausea
• Vomiting
• Diarrhoea
• Anorexia
• Haemorrhage
Blood:
• Anaemia due to combined deficiency of iron, folic
acid (vit B9 ), cobalamin (vit B12)

25. Diagnosis
Direct evidence
• Demonstration of eggs in stool
• Demonstration of eggs in duodenal aspirate
• Demonstration of adult worm in stool
• Culture of stool for larvae
Indirect evidence
• Anaemia
• Occult blood in stool
• Eosinophilia in early stage of disease

26. Tapeworm
The term cestode is derived from a Greek word
‘Kestos’ referring to ribbon.

27. Morphology
• The adult worm consists three parts- the head, neck, trunk.
• The head or the scolex carries grooved or cup like suckers,
which are the organs of attachment to the intestinal mucosa
of the definitive host.
• The neck, immediately behind the head is the region of
growth where the segments of the body are being
continuously generated.
• The trunk or the strobila is composed of a chain of
proglottidesor segments.
• The proglottides near the neck are young, immature,
behind them are the mature segments and at the hind are
gravid segments filled with eggs.

29. Major species affecting man
Tenia solium - pork tapeworm
Tenia saginata - beef tapeworm
Diphyllobothrium latum - fresh water fish tapeworm
Echinococcus granulosus - dog tapeworm

31. Life cycle of cestodes
Adults in the intestine shed gravid
segments containing numerous eggs into
faeces
Eggs contaminate the soil, are ingested
by an intermediate host and hatch into
oncospheres or larvae
Invade through the intestinal mucosa and
disseminate to various viscera
Haematogenous spread

32. Larvae develop into cysts that contain one
or more rounded bodies termed scolices
which are the heads of the future adult
worms
Tissues containing cysts are eaten by
carnivores including man
Scolex attaches to the gut mucosa by
means of suckers or hooks and grows into
worm as a chain of segments or
proglottides
Self or cross fertilization
Distal gravid segments are shed

33. Infections
• Taeniases : T.solium T. saginata
• Diphyllobothriasis : D. latum
• Cysticercosis : T. solium
• Hydatid disease : E.granulosus

34. Disease
• Taeniases
• Diphyllobothria
sis
Cause
• Eating under
cookedor raw
cyst containing
meat from
domestic pigs
• Eating infected
fresh water fish
Symptom
• Mild dyspepsia,
fullness of
abdomen,
weight loss,
psychological
upset
• Anaemia,
worms
consumption of
vit B12 in
competition
with the host

35. Disease
• Cystisercosis
• Hydatid disease
Cause
• Ingesting eggs
from the
environment
• Regurgitating a
gravid segment
of the host’s
own tapeworm
• Eating eggs
from dogs coats
or faeces
Symptoms
• Calcified
nodules (x-
ray),focal
neurological
signs, epilepsy,
optical defects,
hydrocephalus
• Hepatomegaly,
pleural
effusion,
haemoptysis,
abdominal
swelling, spinal
cord
compression

36. Diagnosis
• Segments of eggs in feces
• Biopsy of subcutaneous lump
• Serological examinations
• Radiology
• Microscopic examination of sputum