3. Necator americanus
(New World Hookworm)
1. The adult parasites are small cylindrical worms, 0.5 - 1.5mm
long.
2. Males are usually 7mm-9mm long, while females are about
9mm-11mm long
3. The posterior end male worm is equipped with a
characteristic copulatory bursa.
4. The females have a vulva situated near the center of the
body- slightly anterior.
5. Have capsules equipped with cutting plates on the ventral
margins, and within the capsule small dorsal teeth.
6. The eggs are bluntly rounded, thin shelled (60 by 40 µm)
4. • Life span- ( 3-5 years)
• Can produce anywhere between 5000 to 10,000
eggs per day.
• Sexual maturity is reached at the final molt. –
Mating occurs in the intestine of the host.
• look for and inject sperm.
• The male coils around a female with his curved
area over the female genital pore.(Gubernaculum)
• Males use spicules to hold open the genital
opening on the female to allow transfer of sperm
5.
6. Scanning electron micrograph of the mouth capsule
of Necator americanus, another species of human
hookworm. Presence of two cutting "teeth“.
8. Ancylostoma duodenale
• grayish white or pinkish with the head slightly bent.
• a definitive hook shape at the anterior end.
• well developed mouths with two pairs of teeth.
• has two ventral plates at the anterior margin of the buccal capsule.
• males measure 1cm by 0.5 mm, the females are often longer and stouter.
• Special features- males have presence of a prominent posterior
copulatory bursa.
9. • Males (8 mm to 11 mm ) long with a copulatory bursa at the
posterior end and needlelike spicules which are not fused and
have simple tips
• Females are 10 mm to 13 mm long with the vulva located at the
posterior end.
• Lay 10,000 to 30,000 eggs per day.
• Life span is one year.
10. Scanning electron micrograph of the mouth
capsule of Ancylostoma duodenale. Presence of
four "teeth," two on each side.
12. The Morphological Differences between Two species
of Hookworms
Characteristics A. duodenale N. americanus
Size larger smaller
Shape single curve, looks like C double curves, looks like S
Mouth 2 pairs of ventral teeth 1pair of ventral cutting
plates
Copulatory Bursa circle in shape oval in shape
caudal spine present no
Copulatory spicule 1pair with separate endings 1pair of which unite to form
a terminal hooklet
vulva position post-equatorial pre-equatorial
17. 1) Eggs of Necator americanus or Ancylostoma duodenale passed from
infected host via feces.
2) The eggs must reach warm and moist soil. Then, the eggs hatched into
rhabditiform larvae in 48 hours. The larvae developes into second stage
of rhabditiform larvae.
3) The rhabditiform larvae molts into filariform larvae which is infective
form by the 5th – 8th day.
4) The filariform larvae penetrate the skin tissue to gain entry to the host.
In host, the larvae migrates via lymphatic or circulatory vessel. Then the
larvae carried through heart to the lungs. Then they penetrate into the
pulmonary alveoli, cough from the bronchial tree to the pharynx and
swallowed to the esophagus.
5) The larvae reach the small intestine, they reside and matures into adult
form. The adults copulate while they attach at the mucosa.
1) Then the eggs passed from the host via feces.
19. PATHOGENESIS
Hookworm infection caused by nematode parasite:
• Necator americanus
• Ancylostoma duodenale
Pathogenesis:
a) larvae form
- Rhabditiform ( non infective stage)
- Filariform ( infective stage)
b) presence of buccal capsules (mouth)
- N.americanus ( consists of cutting plates)
- A. duodenale ( consists of teeth)
21. PATHOGENESIS
The filariform (parasite) attach to the mucosa
layer using the sharp teeth / cutting plates
the nematodes suck the mucosal tissue
digestion of the mucosa
underlying blood vessels are exposed
the blood vessels burst and blood released
from the lesions
23. Clinical manifestation
• The list of signs and symptoms mentioned in various sources
for Hookworm includes the 24 symptoms listed below:
• Symptoms from entry of the worms into the body:
– Itchy foot
– Ground itch
– Pimply rash at worm entry site
– Foot pimply rash
• Lung symptoms - when the larvae of the worms are temporarily in the lungs from
where they later move to the intestines
– Wheezing
– Coughing
• Gastrointestinal symptoms - when the worms infest the bowel or intestines:
– Diarrhea
– Vague abdominal pain
– Intestinal cramps
– Abdominal colic
– Nausea
24. Clinical manifestation
• Gastrointestinal bleeding
– Blood in stool
– Black stools
– For details see also symptoms of gastrointestinal bleeding
• Anemia - from gastrointestinal bleeding and from worms sucking
blood; see symptoms of anemia including:
– Pallor
– Fatigue
– Malaise
26. DIAGNOSIS
Tests that can help diagnose the infection include:
• Complete blood count (CBC)
• Stool ova and parasites exam
27. DIAGNOSIS
• Diagnosis depends on finding characteristic worm eggs on
microscopic examination of the stools.
• The eggs are oval or elliptical, colorless, measuring 60 µm by
40 µm
• As the eggs of both Ancylostoma and Necator are
indistinguishable, to identify the genus, they must be cultured in
the lab to allow larvae to hatch out.
28. DIAGNOSIS
• Development of DNA-based tools for
diagnosis of infection
specific identification of hookworm
analysis of genetic variability within hookworm
populations
• PCR assays
hookworm eggs are often indistinguishable from other
parasitic eggs
PCR assays serve as a molecular approach for accurate
diagnosis of hookworm in the feces.
30. Let’s sing along!!
Hookworm
Involve certain treatments
The medications, such as albendazole
Pyrantel pamoate, revapol, vermicol
Vermidil, vermin, vermox
And there is ,
For emergency care,
It involves the phase, of larval migration
Wheezing and cough, Are managed with
inhaled beta agonists
And when there is established infection
We use effective antihelminthic
And as for the early infection
We may use the thiabendazole
But some hookworm infections
Are asymptomatic
That requires little treatment
And also nutrition
These are all for the treatment
That we need to know
As long as you remember
All the medicines
31. Treatment
Parasite-killing medications are usually prescribed such as:
• Albendazole
• Mebendazole
• Pyrantel pamoate
• Vermox
• Revapol
• Vermicol
• Vermidil
• Vermin
Symptoms and complications of anemia are treated as they
arise. The doctor will likely recommend increasing the
amount of protein in diet.
32. Treatment
Other medications involved are:
– Antihelmintics
This difference permits effective treatment using directed
pharmacologic agents in relatively small doses.
– Albendazole
Decreases ATP production in worm, causing energy depletion,
immobilization and finally death.
– Pyrantel pamoate
Causes worm paralysis by a depolarizing neuromuscular blockade.
33. Treatment for emergency care
• Larval migration phase
• Early infection
• Established infection
35. The most important control measures consist of reducing the
contamination of the soil by:
Education and improved sanitation.
Controlled disposal of human feces.
Treatment of infected persons.
Health education with improved sanitary latrines and use of
footwears.
Avoid pollution of soil with human excreta.
Don’t use raw house sewage for fertilizing the edible plants and
vegetables.
Maintain good nutrition and iron intake without being anemic
37. A 62-year-old Vietnamese man presented with a sore throat and bloody
sputum in September 1997. He had arrived in the United States in 1994 with a
history of bright red blood passed rectally. In early 1995, examination by
barium enema and flexible sigmoidoscopy was unremarkable. His medical
history included six years in a re-education camp in northern Vietnam, where
he had lived in near-starvation conditions. In May 1996, his blood count was
significant for an absolute eosinophil level of 559 per mm3 (0.6 3 109 per L). Dry
cough was noted in June 1997.
Physical examination revealed a well-developed, well-nourished patient with
minimal pharyngeal erythema. The chest radiograph showed a parenchymal
opacity at the base of the right lung. The blood count was unremarkable except
for an eosinophil level of 1,870 per mm3 (1.9 3 109 per L). Three stool samples
were negative for occult blood, but all showed hookworm eggs. The patient
was treated with 10 days of oral penicillin, multivitamins and a single 400-mg
dose of albendazole.
CASE STUDY
38. Epidemiology
Hookworm infection is acquired when larvae from the soil penetrate the skin and
enter the circulation. The spread of this nematode infection is aided by poor
sanitary practices in which infected persons defecate in areas where others walk
without shoes.
Clinical Presentation
Patients may develop dermatitis when filariform hookworm larvae penetrate the
skin. Pulmonary symptoms and signs, such as cough, wheezing and pulmonary
infiltrates, may occur when the larvae pass through the lungs after entering the
circulation. In addition, patients may complain of gastrointestinal discomfort when
the larvae are coughed up, swallowed and then reach adult form in the small
intestine, where the worms attach and suck blood.
EPIDEMIOLOGY AND CLINICAL
PRESENTATION
39. Diagnosis
The diagnosis of hookworm infection is based on the presence of ova in stool.
Laboratory findings may also include iron-deficiency anemia and eosinophilia.
Treatment
Albendazole is a synthetic nitroimidazole with broad-spectrum antinematodal
activity plus anticestodal activity and some antiprotozoal activity.
A single dose of albendazole is effective treatment for most forms of intestinal
helminthiasis. However, the drug is officially labeled in the United States only for
the treatment of neurocysticercosis and Echinococcus infection. Mebendazole
(Vermox), another drug used to treat hookworm, must be given for three days.
Patients with iron-deficiency anemia related to hookworm infection also require
iron supplementation. Albendazole and mebendazole should not be used in
pregnant women.
DIAGNOSIS AND TREATMENT
