Hookworm: Infection - Dr. Mramba Nyindo

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Tropical Parasitology: Protozoans, Worms, Vectors and Human Diseases

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Duke University

Tropical Parasitology: Protozoans, Worms, Vectors and Human Diseases

180 notes

This course provides students an understanding of important human parasitic diseases, including their life cycles, vectors of transmission, distribution and epidemiology, pathophysiology and clinical manifestations, treatment, and prevention and control. Tropical Parasitology is taught by faculty from an area highly impacted by tropical parasites- the Kilimanjaro Christian Medical University College in Moshi, Tanzania. The faculty include Drs. Frank Mosha and Mramba Nyindo (and two lecturers, Drs. Johnson Matowo and Jovin Kitau). Dr. John Bartlett, Professor of Medicine, Global Health and Nursing at Duke University, joins his faculty colleagues in this effort.

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Nematodes

The Nematodes cluster focuses on filariasis, ascariasis, hookworm, and strongyloidiasis. Nematode infestations may impact up to 185 million people in recent estimates of the global burden of disease. This cluster has a total of 90 minutes of video and 8 pages of reading spread out over four lessons. You will have unlimited opportunities to take an untimed quiz after you’ve mastered the material in each lesson, and you have four quizzes to complete for this cluster. This cluster kicks off by examining lymphatic filariasis and the fundamental need for compassion as a core value in global health practice.

Hookworm: Infection - Dr. Mramba Nyindo9:16

Hookworm: Pathophysiology - Dr. John Bartlett4:25

Hookworm: Interview with Dr. Venance Maro 1:44

Hookworm: Interview with Dr. William Howlett **also addresses Ascaris10:23

Rencontrer les enseignants

John A. Bartlett, M.D.
Professor of Medicine, Global Health and Nursing at Duke University Medical Center
Duke Global Health Institute
Franklin Mosha, Ph.D.
Professor of Parasitology and Medical Entomology
Mramba Nyindo, Ph.D.
Associate Professor, Kilimanjaro Christian Medical University College (KCMU Co.)

Welcome to this discussion on hookworm infection.

My name is Mramba Nyindo.

I prepared this presentation with Jovin Kitao,

we are at the University College in Tanzania.

Probably it's nice to say a few words about hookworm infection,

which is similar to ascariasis.

This is a disease of poverty and it must be recognized in that way.

Hookworm infections occur in rural areas in the tropics and subtropical areas.

Rural areas What causes hookworm infections?

Nematodes known as Necator americanus and Ancylostoma duodenale.

Where the climate is warm, where the soil is sandy

hookworm infection is regularly transmitted to humans.

The main consequence of hookworm infection in

humans is blood loss accompanied by protein losing

enteropathy is a question of anemia, very big anemia.

That's a hookworm infection consequence.

Infection with Necator americanus is more common than infection with

the Ancylostoma duodenale.

Necator americanus is the main hookworm disease in many parts of the world,

including sub-Saharan Africa, Southern China,

Southern India and Southeast Asia and Central South America.

Very wide distribution of hookworm infection in the world.

Ancylostoma duodenale produces more blood loss than Necator americanus.

More anemia comes about with the infection of the Ancylostoma duodenale.

Take note that Ancylostoma duodenale

can undergo arrested development in the host and when this happens,

there is seasonality of hookworm infection that can occur.

This is common in India and west of Bengal.

Ancylostoma caninum and Ancylostoma braziliense

are two dog hookworms that cause cutaneous larva migrants in humans.

Which means infection of humans with these two parasites is not completed.

Ancylostoma caninum causes.

Another condition in humans, we refer to it as human eosinophilic enteritis.

Which is an emerging human enteritis.

That must be enteritis that must be recognized.

Also take note that cutaneous larva migrants in Ancylostoma caninum or

Ancylostoma braziliense occurs at a re-exposure to

the L3 larva, not at primary infection.

How do hookworms enter the host?

Hookworms produce peptides that act as anticoagulants.

These peptides block the activity of factor

Xa and factor VIIa/TF.

What do they do?

They inhibit blood coagulation, thereby making it possible for

the hookworm to have blood readily available for its use at all times.

Let's describe the organism and egg.

The males are 7 to 9 mm, and females measure 9 to 11 mm in length.

These attach themselves firmly to the mucosa of the intestine by two ways.

By cutting plates, for Necator americanus.

And by teeth in ancylostoma duodenale.

We rarely find adult hookworms in stool so

stool examination is not very useful for detection of eggs of hookworms.

Why?

Because these parasites remain, as I said,

firmly attached to the intestinal mucosa by teeth or plates.

The gravid female worm in the intestine lays something like 500 to

10,000 eggs per day.

It's not a small number.

These eggs may be anything from 60 micrometers long by 40 micrometers wide.

How do they look like?

They are oval, have broadly rounded ends.

There is a distinct space between the embryo and

the clear eggshell, and this is diagnostic.

These eggs develop well in sandy loam soil where the climate is warm.

There is good moisture and shade, the soil must be sandy.

Hookworm eggs get released into environment with feces.

The L1 rhabditiform larva emerges and it feeds on organic debris and bacteria.

It will molt to L2 larva, this will molt into L3 larva which is filariform larva.

Take note that the effective parasite

stages L3 filariform larva.

These filariform larva can remain alive in the soil for

eight days, or probably more.

How does it get attached to human skin?

When there's vibration?

Somebody moving around and making vibration?

By touch, heat, people working the fields, touching the soil?

There's heat generated.

Water currents, human breath, thud of feet of a walking person.

These contribute to identification of

hookworm L3 filariform larva of a person's skin.

These filariform larva will penetrate the skin very actively.

This penetration is aided by secretions of proteolytic enzymes which

degrade collagen type one, type three, type four, and type five.

Fibronectin is also digested l`aminin and

elastin are also degraded.

Therefore, this parasite makes it way easily into the body.

Upon penetration of the human skin this parasite will enter the capillaries.

And the lymphatics it will reach the pulmonary vasculature, it will migrate to

the lungs, it will ascend the trachea, epiglottis and then it will get swallowed.

It must go back to the intestine.

It arrives at the small intestine and develops into the adult worm,

take note that Ancylostoma duodenale is transmitted

by both the skin penetration and oral ingestion.

L3 larva enters the small intestine and to develop L4 larva stage.

This will reach adulthood.

Adult worms will attach themselves firmly to the mucosa of the intestine,

this is a repetition.

Here, it will start feeding on the host blood.

It will take about two months for

hook worms to complete their developmental cycle.

This comes to the end of this presentation on hook worm.

A disease of poverty.

Thank you very much for participating.

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