hgfvtft

1. Chapter 5
Nematodes (Roundworms)
- Helminthology

2. 02/24/2025 Chapter 5 2
General Characteristics
Non segmented cylindrical (Roundworms) & pointed at both
ends
Shiny cuticle => smooth, with spine or ridged
=> used for Protection and evasion (IR)
Movement = undulating motion
=> contraction & relaxation of the longitudinal muscles
Have Pseudocoel (body cavity)
Male < Female - size

3. 02/24/2025 Chapter 5 3
 Mouth: surrounded by lips or papillae => teeth/cutting plates
Sexes are separate (dioecious) => female’s organ is double
The male has a testis with copulatory organs = spicules
Copulatory bursa => hold female during copulation
Females => viviparous (larvae), oviparous (eggs) or ovo-
viviparous (egg containing larvae)

4. 02/24/2025 Chapter 5 4
Cont’d
Nematodes (in Human) => live in intestine, blood or tissue
Have a direct life cycle
Tissue nematodes => transmitted by insect vectors
Intestinal nematodes => transmitted by fecal-oral route & soil
Have a complete DS with both oral & anal openings
=> esophagus or pharynx sucks food into intestine

5. 02/24/2025 Chapter 5 5
Life stages are => egg, larvae (Juvenile) & adult
Has 4 larval (Juvenile) stages
=> each stage is separated by a molt (M) of the cuticle
The first larva stage = Rhabditiform
Infective larva stage = Filariform larvae

6. 02/24/2025 Chapter 5 6

7. 02/24/2025 Chapter 5 7
A. Trichinella spiralis
GeogD: worldwide => 3 sub-species:
 T. S. nelsoni = Africa & southern Europe
Habitat: Adults: in small intestine mucosa of Pigs, Rat, Man, Dog
 Larvae: encysted in muscle
 Egg: No eggs (adult is Viviparous)
Morphology: Adults: thread-like, white and viviparous
 Larva: black in color & coiled tail

8. 02/24/2025 Chapter 5 8
Conti…T. spiralis
Life cycle: The same animal (man)=>definitive + intermediate host
 Infection => by eating flesh of animal’s (infective larvae)
ÞLarvae released (acid-pepsin digestion) larvae molt (4)
adult worm (small intestine) male dies (a/r mating) &
females gives larvae (viviparous)
ÞLarvae (penetrate intestinal wall & body circulation)
striated muscles (form cyst)
 Reservoir host is swine

9. 02/24/2025 Chapter 5 9
Conti…T. spiralis
Pathology: Trichinellosis (trichinosis)
Nausea, vomiting, abdominal pain, diarrhea, headache, fever,
blurred vision, & eosinophilia
Migration of newborn juveniles damage blood vessels cause
edema in the face and hands, also cause pneumonia, deafness,
brain or eye damage, and death resulting from myocarditis
(inflammation of heart muscle)

10. 02/24/2025 Chapter 5 10
Conti… T. spiralis
Lab Diagnosis:
 Finding the larvae in striated muscle
 Muscle Biopsy
 Testing serum for Trichinella antibodies.
Treatment: Thiabendazole and Mebendazole
Prevention and Control:
 Avoid eating of raw or undercooked pork
 Inspecting meat for infective larvae
 Treatment

11. 02/24/2025 Chapter 5 11
B. Trichuris trichiura (The Whip-worm)
 Thin whip-like anterior (attach) & a thick fleshy posterior part
GeogD: Cosmopolitan (warm area), fairly common in Ethiopia
Habitat: Adult (oviparous): in large intestine
 Eggs: In the feces
Morphology: Adults: whip-like shape,
 Male: has coiled tail; Female: oviparous and has straight tail
 Egg: barrel-shaped and yellow brown

12. 02/24/2025 Chapter 5 12
Conti… T. trichiura
Transmission is by => ingesting eggs containing infective larvae
=> contaminated hands, food or drink, or
=> swallowing soil that contains embryonated eggs
Life Cycle: Egg (ingested) Larva (hatch) small intestine villa
(penetrate) large intestine(migrate) Adult immature Egg (a/r
mating) soil with stool (embryonated egg) Larvae (Warm soil)
Egg contain infective larvae

13. 02/24/2025 Chapter 5 13
Conti… T. trichiura
Pathology: asymptomatic but in children wz heavy worm (200-
1000) => chronic diarrhea, intestinal ulceration with dysentery,
iron deficiency anemia, weight loss and rectum prolapse
=>Rectal prolapse: loss of muscle tone on rectum wall (worm)
 Lab Diagnosis: eggs in the feces
=> adult worms in rectal mucosa in prolapsed rectum

14. 02/24/2025 Chapter 5 14
Conti… T. trichiura
Treatment: Mebendazole and Albendazole
Prevention and Control
 Sanitary disposal of feces & avoid use of feces as a fertilizer
 Personal hygiene (washing hands a/r defecation & b/r eating)
 Treatment & health education

15. 02/24/2025 Chapter 5 15
C. Strongyloides stercoralis (The dwarf thread worm)
GeogD: worldwide (Facultative in host & soil)
Habitat: Adults female: in the small intestine mucosa,
=> Male mostly is not parasite
Rhabditiform larvae: in feces (active motile) & external env’ts
Filariform larvae: soil and water (infective stage)

16. 02/24/2025 Chapter 5 16
Conti… S. stercoralis
Morphology: Adult Female (parasitic): straight posterior end (Ovo-
viviparous)
Life cycle: Infection is by filariform larva penetrating the skin.
 Larvae enter blood vessels => heart-lung (develop)
 At trachea the larvae swallowed & mature (intestinal tract)
 Female lay eggs in small intestine (develop) => rhabditiform
→ Form Filariform => internal autoinfection ↑se adult No
= Hyper-infection

17. 02/24/2025 Chapter 5 17
Conti… S. stercoralis
→ Or passed out with feces and follow free living way of life
=> or it develops in to the infective stage (filariform larvae) &
penetrate the skin of same host = external autoinfection
Pathology: Strongyloidiasis (Cochin China diarrhea) & 3 phases
1. Cutaneous phase (skin penetration): itching & erythema
2. Pulmonary phase (migration of larvae in the lungs)
=> cough, wheezing and fever.
3. Intestinal phase (adult invasion) => abdominal pain, ulceration,
inflammation, malabsorption & mucus diarrhea, constipation,
nausea, vomiting and anemia

18. 02/24/2025 Chapter 5 18
Conti… S. stercoralis
Lab Diagnosis: larvae & eggs (sometimes) in feces
=> eggs are few in number
Treatment: Mebendazole & Albendazole
Prevention and Control
1. Sanitary disposal of feces & avoid use of feces as a fertilizer
2. Wearing protective footwear
3. Treatment & Health education.

19. 02/24/2025 Chapter 5 19
D. HOOKWORMS
Þ2 sp. Ancylostoma duodenale (Old World) &
Necator americanus (New World hookworm).
 No intermediate host & man is the only definitive host
 Both found in Ethiopia but N. americanus (most common)
 Both species are similar with some differences

20. 02/24/2025 Chapter 5 20
Conti… HOOKWORMS
GeogD: => N. americanus: Far East, South Asia, pacific Islands,
Tropical Africa, Central & South America
=> A. duodenale: China, Japan, Europe, North Africa, southern
Europe, Middle East
Habitat: Adult: small intestine of man
 Eggs: In the feces; not infective to man
 Infective larvae: free in soil and water

21. 02/24/2025 Chapter 5 21
Conti… HOOKWORMS
Morphology: A. duodenale: Adult - longer,
thicker, white and Large mouth cavity
(Buccal capsule); Two pairs of teeth, two
plates & two sub-ventral lancets.
 Female lays 20,000eggs/day
 N. americanus: Adult-short, thinner, longer
Buccal capsule, 2 cutting plates & 2 sub-
dorsal lancets.

22. 02/24/2025 Chapter 5 22
Conti… HOOKWORMS
Egg: oval in shape
Rhabiditi-form Larvae: long bucal cavity, Pointed tail
Filari-form: short bucal cavity, sharply pointed tail
Mode of Transmission: only one host = man (definitive)
 Infection in 2 ways: (1) penetration of the skin &
(2) ingesting filari-form larvae

23. 02/24/2025 Chapter 5 23
Conti… HOOKWORMS
Life cycle:
 Larvae penetrate skin & enter blood vessels (heart-lung migration)
=> At trachea=>larvae swallowed, develop & mate (small intestine)
 The worm attach to the small intestine wall
=> suck mucus & blood from the host
 Female worms lay eggs which are passed in the feces
 Egg (External Env’t) develops & hatches to rhabditiform larvae
then filariform larvae

24. 02/24/2025 Chapter 5 24
Conti… HOOKWORMS
Pathology: hookworm infection
=> Severe itching (@ skin penetration) = "Ground itch", mild
pneumonia with cough, sore throat, bloody sputum, headache,
weakness, bloody diarrhea and iron deficiency anemia.
 Adult hookworm ingests > 0.03ml blood/day
=> chronic blood loss
 Heavy Infections: severe protein deficiency, with dry skin and
hair, edema, & mental dullness, heart failure & death

25. 02/24/2025 Chapter 5 25
Conti… HOOKWORMS
 3 factors for Severity of disease: Number of worms,
Species of hookworm, &
host Nutritional condition
N. americanus: < 25 worms = no symptoms
 >1000 worms causes severe symptoms, very grave damage &
Fatal
Ancylostoma spp: fewer worms (100) => greater disease
=> b/se it sucks more blood than N. americanus

26. 02/24/2025 Chapter 5 26
Conti… HOOKWORMS
Lab Diagnosis: ova (egg) in feces
Treatment: Mebendazole with balanced diet & oral iron
supplementation
Prevention and control:-
1. Sanitary disposal of feces & avoid use of feces as fertilizer
2. Using foot ware for adequate protective
3. Treatment and health education.

27. 02/24/2025 Chapter 5 27
E. Entrobius vermicularis (Pin Worm)
GeogD: Cosmopolitan (children > adult)
Habitat: Adult: small intestine & gravid female in large intestine
 Eggs: In feces or deposited on perianal skin
 Embryonated eggs are infective to human
Morphology: Adults: yellow white;
 Female: thin pointed tail and Male: Coiled tailed
 Egg: oval & shell is double, smooth & thin

28. 02/24/2025 Chapter 5 28
Conti… E. vermicularis
Life Cycle: infection is by ingestion of embryonated egg
(with contaminated hand, food or drink)
 Infective eggs hatch  larvae  adult worms (large intestine)
 The female worms migrate to the rectum (After mating)
 The gravid females pass out of the anus and lay eggs on the peri-
anal skin (night)
=> Females die soon a/r oviposition, & males die soon a/r copulation

29. 02/24/2025 Chapter 5 29
Conti… E. vermicularis
Human can acquire infection;
1) Ingestion of eggs from anus to mouth = Finger (children)
2) handling of night clothes or bedding
3) inhalation of air-borne eggs and
4) Retro-infection: unclean perianal folds, attached eggs hatch
and juveniles may wander into the anus

30. 02/24/2025 Chapter 5 30
Conti… E. vermicularis
Pathology: two aspects: => worms within the intestine &
=> egg deposition around the anus
 The worm => intestinal ulcer, inflammation & bacterial infection
 The worms migration => allergic reactions around the anus & during
night it causes nocturnal itching (perianal pruritus) & Enuresis
 The worms may obstruct the appendix causing Appendicitis
 Gravid female worms can migrate from the anus into the female
genital tract that leads to vaginal infections

31. 02/24/2025 Chapter 5 31
Conti… E. vermicularis
Lab Diagnosis: The egg is usually more easily found
1. Finding eggs from perianal skin (folds of skin round anus) using
cellulose adhesive tape (Perianal swab) called
Scotch-tape swab method
2. eggs &/or adult in feces

32. 02/24/2025 Chapter 5 32
Conti… E. vermicularis
Treatment: Mebendazole or Albendazole
Prevention and Control:
Treating all members of a family
Washing of the anal skin each morning soon after waking.
Washing of night clothes

33. 02/24/2025 Chapter 5 33
F. Ascaris lumbricoides (Round worm)
GeogD: Cosmopolitans (common in Ethiopia)
Habitat: Adult: In the small intestine
 Egg: In the feces
Morphology: Adult: pinkish color
 Male: short & curved tail
 Female: long & straight tail
 Eggs: The egg can be Unfertilized, Embryonated, Decorticated or
Fertilized egg

34. 02/24/2025 Chapter 5 34
Conti… A. lumbricoides
Life cycle: Embryonated egg (infective) => contains rhabditiform
=>Ingestion of the infective egg (hand, food or drink)
 Ingested Egg hatch  larvae (small intestine) & penetrate blood
vessels of the wall
 Then follow a heart to lung migration and
 At the trachea, the larvae (swallowed into small intestine) then
mature into adult and mate (female lays 200, 000 eggs/day)
 Eggs passed in the feces  infective egg (in shaded soil)
 The larva does not hatch until the egg is swallowed.

35. 02/24/2025 Chapter 5 35
Conti… A. lumbricoides
Pathology: migration of Ascaris larva => inflammatory &
hypersensitive reactions => coughing and bronchial asthma
 Adult worms (intestine) => pain, nausea, diarrhea & vomiting
 Infected children => gastrointestinal mal-function, Vitamin A
deficient, low serum albumin & also impair of physical and
intellectual development
=> The adults expelled through
the anus, mouth or nose

36. 02/24/2025 Chapter 5 36
Conti… A. lumbricoides
Lab Diagnosis:
 Finding the eggs in feces
 Identifying adult worms expelled through the anus, nose or mouth
Treatment: Mebendazole (Vermox) or Albendazole
Prevention and Control:
1.Prevent soil contamination with feces & avoid using as a fertilizer
2.Washing hands b/r eating & not eating uncooked vegetables
3.Treatment & health education.

37. 02/24/2025 Chapter 5 37
G. Dracunculus medinensis (Guinea or Medina worm)
GeogD: India, Yemen & sub-Sahara (lowlands of Ethiopia)
=> It will be eradicate in the near feature.
Habitat: Adults: Female in the subcutaneous and muscular
connective tissues; especially water contact parts E.g. ankle.
 Male: in the retroperitoneal connective tissues & dies a/r mate
 First stage larvae: In the ulcers
 Infective filariform larvae: In the Cyclops

38. 02/24/2025 Chapter 5 38
Conti… D. medinensis
Morphology: Adults: thread like & White with smooth surface
 Male: coiled posterior end & Female: Viviparous
 Larva: rounded anterior end & pointed tail
Life cycle: Man, dogs & cats (definitive) & Cyclops (intermediate)
=> Infection: swallowing of larvae infected Cyclops with water
 Larvae: freed & penetrate duodenal wall & migrate to connective
tissues
 In connective tissues larvae develop to adult & mate

39. 02/24/2025 Chapter 5 39
Conti…life cycle of D. medinensis
 A/r mate, female worm migrates to connective tissues (lower
limbs) => the ankle, foot, arms & shoulders (in contact wz water)
 Female worm form blister (ulcer) & buries its anterior end
 When the blister (ulcer) is bathed in the water first stage larvae
released
 The larvae are unable to swim but are actively motile, coiling &
uncoiling tail
 The larvae ingested by Cyclops & develop in to infective larvae in
its body cavity

40. 02/24/2025 Chapter 5 40
Conti… D. medinensis
Pathogenesis: asymptomatic
=> until female worm reaches to surface of the skin
 Female guinea worm releases toxic histamine (migration)
=> allergies
 Worm under the skin form blister
=> burning pain (relieved by applying water)
 The blister bursts & the larvae released during water contact

41. 02/24/2025 Chapter 5 41
Conti… D. medinensis
Lab Diagnosis: always after blister has ruptured
=>Finding the gravid worm in the blister & collect the larvae
The adult worm removed by rolling on small stick & slowly pulling
daily
=> Considered as treatment
=>Be careful not to pull
apart (recoil back)
Surgical removal of
the worm (local anesthesia)

42. 02/24/2025 Chapter 5 42
Conti… D. medinensis
For laboratory confirmation of the larvae,
1. Place few drops of water on the ulcer => larvae move out
2. After a few minutes collect the water in a pipette
3. prepare a wet mount, then examine motile larvae
Prevention and Control:
1.Prevent water contamination with the larvae and avoid drinking
infected water
2.Destroy the Cyclops by using chemicals, e.g. chlorine
3.Treatement & health education not to in to water
=> Or cover the blister with a water proof dressing