3. Part ⅠGeneral Information about
Nematode
Nematode belong to
Phylum Nemathelminthes
Class Nematoda
Most nematodes are free living in fresh water, sea
water and soil.
A few are parasitic in humans, animals and plants.
4. A. adult
elongate,cylindrical,bilaterally symmetrical and
tapered at both end.
dioecious, male female. At the curved,posterior﹤
end of male is a copulatory organ.
Ⅰ.MORPHOLOGY
roundwormpinworm
5. pseudocoelom
nematode consists of an outer tube(the body wall) enveloping
an inner tube(the digestive tract). between the tubes is the fluid-
filled pseudocoelom, in which the reproductive system and
other structures are found.
no peritoneal lining ,
containing transport of
solution, electrolytes,
proteins, fats
function: protecting
the internal organs,
helping the movement
and excretion of the
worm
Body
wall
Digestive
tract
pseudocoelom
7. The arrangement of the somatic muscles is of
value in the systematic grouping of nematodes
Polymyarian HolomyarianMeromyarian
roundworm Hookworm whipworm
11. 4.excretory system4.excretory system
Two lateral excretory ducts running inside theTwo lateral excretory ducts running inside the
lateral cordslateral cords
5.Nervous system5.Nervous system
A nerve ring encircling the esophagus,from whichA nerve ring encircling the esophagus,from which
trunks radiated anteriorly and posteriorly.trunks radiated anteriorly and posteriorly.
Lateral
excretory
duct
12. B.Egg
Three layers:Three layers:
1. outer layer : embryo membrane1. outer layer : embryo membrane
2. Middle layer: chitinous layer2. Middle layer: chitinous layer
3. Inner layer: lipid layer/ascaroside3. Inner layer: lipid layer/ascaroside
Protein
membrane
chitinous layer
embryo membrane
lipid layer
Inside the egg, there is an embryo that may range from a
few blastomeres to a completely formed larva
13. Stages in life cycle of nematodes includeStages in life cycle of nematodes include ::
eggegg larvaelarvae adultsadults
Under favorable conditions larvae undergoUnder favorable conditions larvae undergo
fourfour moltsmolts
Two types of nematodesTwo types of nematodes
soil-transmittedsoil-transmitted nematodes:nematodes: Ascaris,Ascaris,
pinworm, whipwormpinworm, whipworm,, hookwormhookworm
bio-sourcebio-source nematodes:nematodes: Filaria,Filaria,
Trichinella spiralisTrichinella spiralis (intermediate host)(intermediate host)
Ⅱ.LIFE CYCLE
14. Infections is transmitted by:
1) Ingestion of eggs (Ascaris lumbricoides )
2) Penetration of larvae through surfaces
(Hookworm)
3) Insect bite (Filaria)
4) Ingestion of encysted larvae (Trichnella
spiralis)
15. The effect depends on the species, wormThe effect depends on the species, worm
burden,development stage, parasiticburden,development stage, parasitic
site,physiological condition andsite,physiological condition and
immunological response of hostsimmunological response of hosts
Species vary in their ability to produceSpecies vary in their ability to produce
mechanicalmechanical oror toxic damagetoxic damage and in theirand in their
selective affinity for vital organselective affinity for vital organ
III. Pathogenesis and symptomatology
22. Introduction
﹡﹡““round worm of manround worm of man””
﹡﹡It is the largest of the intestinalIt is the largest of the intestinal
nematodesnematodes
﹡﹡It is the most common worm found inIt is the most common worm found in
humanhuman
﹡﹡adult worm parasitize in the intestinaladult worm parasitize in the intestinal
tract of human ,and causetract of human ,and cause AscariasisAscariasis..
23. A.Adult:A.Adult:
shape:shape: cylindrical, fusiform body,similar tocylindrical, fusiform body,similar to
earthworm.earthworm.
Color:Color: pink(alive) and white(dead).pink(alive) and white(dead).
Length:Length: female: 20-30cm; male:15-31cmfemale: 20-30cm; male:15-31cm
Special structure:Special structure:
On the tip of the head there areOn the tip of the head there are three lipsthree lips,,
arranged as a Chinese word “arranged as a Chinese word “ 品 ”品 ” ..
Cross veins and lateral lines are paired on theCross veins and lateral lines are paired on the
surface of the bodysurface of the body
The typical curled tail with a pair sickle likeThe typical curled tail with a pair sickle like
copulatorycopulatory spinesspines..
Ⅰ.MORPHOLOGY
27. There are three kinds of the eggs:There are three kinds of the eggs: fertilizedfertilized
eggs, unfertilized eggseggs, unfertilized eggs andand decorticateddecorticated
eggs.eggs.
We usually describe an egg inWe usually describe an egg in 5 aspects5 aspects::
size, color, shape, eggshell and contentsize, color, shape, eggshell and content
B.Egg
28. Fertilized egg:
size: 45-75 × 35-50 μm.
Shape:elliptic.
color:brown.
shell:thick and protein
membrane
outside of the shell
content: one embryo cell.
31. Freshly Passed Ascaris Eggs From
faeces
The eggs mayThe eggs may
appear from lightappear from light
to dark brown into dark brown in
color.color.
32. Embryonated Eggs of Ascaris
Egg contains a larva, which will be
infective if ingested.
34. unFertilized egg:
Measure: 88-94 × 39-44 μ m.
Shape:longer and slender than
fertilized egg.
color:brown.
shell:thin protein membrane
without ascaroside.
content: a mass of refractile
granules
38. Both fertilized and unfertilized eggs sometimesBoth fertilized and unfertilized eggs sometimes
may lack their outer protein coats and are colorless.may lack their outer protein coats and are colorless.
Decorticated egg
39. • Human to human
adult worm
egg
larva (four times molts)
adult worm
Ⅱ.LIFE CYCLE
40. Development of ovaDevelopment of ova
temperature, moisture, oxygentemperature, moisture, oxygen
fertilized eggs Infective eggs
25-30℃
2-4w
Enclosed larva has undergone
its first molt
Survive viable in the soil for two years or longer
41. Life cycle
Adult worms live in the lumen of small intestine,
feeding on the intestinal contents, where the
fertilized female lays eggs.
After the ingestion of infective eggs in contaminated food or
drink or from contaminated fingers, host digestive juices
acts on the egg shell and liberate the larva into the small
intestine
These larvae penetrate the intestinal mucosa
and enter circulatory system ,
They are carried by circulation to the
liver, right heart and finally to the
lungs
where they penetrate the capillaries into the alveoli in
which they molt twice and stay for 10-14days
then they are carried up the bronchioles, bronchi, and trachea to the epiglottis. When
swallowed, the larvae pass down into the small intestine where they develop into adults.
44. summary
1. Site of inhabitation:1. Site of inhabitation:
2. Infetive stage:2. Infetive stage:
3. Route of infection:3. Route of infection:
small intestine
infective eggs
by mouth
4. No intermediate and reservoir hosts
5. Life span of the adult: about 1 year
6.Female can produce up to 200,000eggs/day
45. The variedThe varied
pathologypathology
of Ascarisof Ascaris
infectioninfection
The reaction of the invading
larvae
The irritation of the intestine
by the mechanical and toxic
action of adult
The complication arising from
its extra-intestinal migrations
III. Pathogenesis and symptomatology
46. Pathogenesis and SymptomsPathogenesis and Symptoms
1. Migrating larvae1. Migrating larvae
The pathological
reaction to the
invading larvae
depends upon
The number of invading larvae
The histological nature of the
organ involved. Liver, lung
47. The pathogenesis in
human consist of
Eosinophilic infiltration
Granuloma formation
around and in the path of
migrating larvae
Inflammation along the portal
tract with infiltration of
eosinophils in the acute phase
Later fibrosis of the periportal and interlobular space occurs
48. Pathogenesis and SymptomsPathogenesis and Symptoms
The pathologic process
in the lung is known as
Ascaris pneumonitisAscaris pneumonitis
The symptoms of ascaris pneumonitis
Dyspnea ; bronchial asthma
A dry or productive cough
Moderate fever; transient eosinophilia
49.
50.
51. 2. Adult worms2. Adult worms
The varied symptoms of adult ascaris infection
depend upon the location and to a lesser extent
upon the number of the worms
Intaking nutrimentsIntaking nutriments and negatively affect theand negatively affect the
absorption, poor nutritional statusabsorption, poor nutritional status
AllergyAllergy
ComplicationComplication
52. Intestinal ascariasisIntestinal ascariasis
Adult worm usually cause no acute symptoms
ChildrenChildren
Intermittent colicky
Loss of appetite
Abdominal distension
Malnutrition
Impairment of growth, stunted growth
53. AllergyAllergy
Exposure to ascaris allergen may cause
hypersensitivity reactions in lungs,skin and
intestinal mucosa
Itch
Urticaria
Angioneurotic edema
Skin
change
54. ComplicationsComplications
When disturbed
by fever (usually
a temperature
over 38.9℃ or
other abnormal
conditions)
The worms migrate outward in
both direction
The worms congregate in a
closely mass that may tend to
obstruct the bowel causing
mechanical ileus
The migrating worm have a
proclivity for probing and force
themselves into any cavity
55. MigratingadultwormsMigratingadultworms
Most commonly they simple expelled or crawl
from the mouth
They enter the nasal meatus via the nasopharynx
and exit through a naris
They may penetrate to the middle ear and through
the tympanic membrane to the external auditory
meatus
They enter and block the biliary or pancreatic
duct, resulting acute biliary or acute pancreatitisacute pancreatitis
They may loged in the appendix and cause
obstructive appendicitisobstructive appendicitis
They may reach other site such kidney via
fistula formed after intestinal perforationintestinal perforation
56.
57. Biliary ascariasisBiliary ascariasis
The most common complicationThe most common complication
Symptoms:Symptoms:
Right upper abdominal pain,a sudden onset, a very strongRight upper abdominal pain,a sudden onset, a very strong
intensity,nausea, vomiting and extremal nervous.intensity,nausea, vomiting and extremal nervous.
58. Mechanical ileus
The usual site of obstruct:
Ileocecal region
Symptoms:
Start suddenly with
vomiting and colicky,
recurring abdominal pain.
Intestinal perforation
59. finding the egg in the fecesfinding the egg in the feces
(1) Direct fecal film: It is simple and effective. The
eggs are easily found due to a large number of the
female oviposition, So this method is the first
choice.
(2) Recovery of adult worms
therapeutic test and clinical manifestationtherapeutic test and clinical manifestation
Ⅳ Laboratory Diagnosis
60. World wide distribution, very common inWorld wide distribution, very common in
China, especially in the countryside.China, especially in the countryside.
Factors favoring the spread of the transmission:Factors favoring the spread of the transmission:
1.1. Simple life cycle.Simple life cycle.
2. Enormous egg production2. Enormous egg production
3.3.Eggs are highly resistant to ordinary disinfectantsEggs are highly resistant to ordinary disinfectants
4. Social customs and living habits.4. Social customs and living habits.
5. Disposal of feces is unsuitable.5. Disposal of feces is unsuitable.
ⅤEpidemiology
62. Ascariasis is most prevalent in the area with
warmer climates, moister and poor sanitation
63. Treatment of infected patients:Treatment of infected patients:
Mebendazole,Mebendazole, AlbendazoleAlbendazole andand
LevamizoleLevamizole are effective.are effective.
Sanitary disposal of feces.Sanitary disposal of feces.
Hygienic habits such as cleaning of handsHygienic habits such as cleaning of hands
before meals.before meals.
Health education.Health education.
Ⅵ Prevention & Treatment