Hookworm Infection and Pathogenesis Quiz

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Questions and Answers

What is the initial site of infection for filariform larvae of hookworms?

Mouth

Lungs

Intestinal mucosa

Skin (correct)

What happens to the filariform larvae after they penetrate the skin?

They become fully independent

They migrate to the lungs (correct)

They reproduce in the skin

They die immediately

Which symptom is commonly associated with a heavy hookworm infection?

High fever

Localized rash

Diarrhea (correct)

Severe pruritus

What characterizes the filariform larvae in terms of their physical attributes?

Long and slender Signup and view all the answers

What distinguishes the ground itch caused by Necator from that caused by Ancylostoma species?

Ground itch is not observed in Necator Signup and view all the answers

What is a common symptom of Loeffler’s syndrome related to hookworm infection?

Coughing and wheezing Signup and view all the answers

Which stage of hookworm larvae is known to be infective?

Filariform larva Signup and view all the answers

Which of the following is NOT a characteristic of hookworm pathogenesis?

Production of eggs in the larva Signup and view all the answers

What is the primary cause of anemia in patients infected with hookworms?

Proportionality of worm burden and iron reserves. Signup and view all the answers

Which species of hookworm is known to ingest the most blood per day?

Ancylostoma Signup and view all the answers

What symptom is not typically associated with the maturation of hookworms in the jejunum?

Headaches Signup and view all the answers

What technique is used for stool culture to identify larval species of hookworms?

Harada Mori technique Signup and view all the answers

Which of the following groups is most susceptible to symptomatic anemia due to hookworm infection?

Pregnant women and laborers Signup and view all the answers

Cutaneous larva migrans is primarily caused by which of the following?

Ancylostoma braziliense Signup and view all the answers

What characteristic is associated with the presentation of cutaneous larva migrans?

Creeping eruptions under the skin Signup and view all the answers

Which of the following is NOT a method of prevention for hookworm infection?

Consuming a high-fiber diet. Signup and view all the answers

What condition can result from an accelerated autoinfectious cycle in immunocompromised hosts?

Hyperinfection Signup and view all the answers

What is a primary factor contributing to the high prevalence of hookworm infection in certain communities?

Improper disposal of human feces Signup and view all the answers

Which age group is most frequently affected by initial Strongyloides infection?

Children Signup and view all the answers

What is the estimated worldwide prevalence range of Strongyloides infection in endemic areas?

2-20% Signup and view all the answers

Which of the following statements about hookworm infection is true?

Hookworms can cause both anemia and impair development over many years. Signup and view all the answers

What is the mortality rate for patients requiring hospitalization due to Strongyloides infection?

16.7% Signup and view all the answers

How do necator americanus and ancylostoma duodenale attach to the intestinal mucosa?

Through teeth in a buccal capsule Signup and view all the answers

What type of skin lesion is characteristically associated with Strongyloides infection?

Ground itch Signup and view all the answers

What is the characteristic feature of the first stage larva of hookworms?

It is short and non-infective. Signup and view all the answers

Which statement is true regarding the filariform larvae of Strongyloides?

They penetrate the skin to initiate infection. Signup and view all the answers

In which demographic setting is hookworm disease most likely to flourish?

Subtropical regions with poor sanitation conditions Signup and view all the answers

What is the pathognomonic rash that manifests due to Strongyloides infection?

Larva currens Signup and view all the answers

What is the approximate number of people infected by hookworms globally?

Around 576-740 million Signup and view all the answers

Which of the following factors is NOT associated with an increased risk of hookworm infection?

High access to healthcare Signup and view all the answers

What happens to rhabditiform larvae during the indirect life cycle of Strongyloides?

They develop into free-living adult worms. Signup and view all the answers

The larvae responsible for hookworm infection are found in what type of environment?

Moist, shaded soil Signup and view all the answers

What is the primary method of treatment for an infection caused by Strongyloides stercoralis?

Ivermectin or Albendazole Signup and view all the answers

How do Strongyloides stercoralis larvae primarily exit the human body?

As rhabditiform larvae Signup and view all the answers

What is the potential consequence of scratching the site of infestation by Strongyloides stercoralis?

Development of a bacterial infection Signup and view all the answers

What is the primary mode of transmission for Strongyloides stercoralis?

Contact with contaminated soil Signup and view all the answers

What distinguishes the life cycle of Strongyloides stercoralis from other helminths?

The female is parthenogenic and releases larvae instead of eggs. Signup and view all the answers

Which statement is true regarding the mortality rate of Strongyloides stercoralis infections?

It can be high, especially in immunocompromised individuals. Signup and view all the answers

Once larvae penetrate the skin of a human host, where do they typically migrate first?

To the pulmonary circulation Signup and view all the answers

Under which condition are larvae more likely to undergo autoinfection within the human host?

Constipation and decreased bowel motility Signup and view all the answers

Study Notes

Soil Transmitted Helminths (STH 2)

Hookworms are Ancylostoma duodenale and Necator americanus
These hookworms infect 576-740 million people globally
Approximately 10% of infected individuals develop anemia
Hookworms can persist in the host for years, impacting physical and intellectual development in children and economic development in communities.

Hookworm Distribution

Hookworms are widespread in tropical and subtropical regions
Prevalence can reach as high as 90% in specific communities
Rural areas with moist, shaded soil and inadequate sanitation are associated with higher hookworm prevalence
Agricultural laborers are at elevated risk of hookworm infection due to exposure

Demographic Prevalence

Hookworm infection is closely linked with poverty
Inadequate sanitation and poor housing conditions are contributing factors
Limited access to essential medications plays a role in the prevalence
Prevalence decreases as countries develop and conditions related to sanitation improve

Route of Infection

Hookworm infection occurs through skin exposure to larvae present in soil contaminated with human feces.
Adults and agricultural workers are at equal or higher risk than children

Hookworm Characteristics

Two key species: Necator americanus and Ancylostoma duodenale
Adult hookworms measure 10-15 mm in length
Both species have buccal capsules (primitive mouths)
A. duodenale has two pairs of teeth, while N. americanus possesses cutting plates. These adaptations facilitate attachment to the intestinal mucosa.
The ova of both species share morphological similarities. Ova have a thin, clear, smooth, colorless shell with the embryo inside

Hookworm Prevalence Map

A global map displays hookworm prevalence rates, with darker shades correlating to higher rates.

Hookworm Life Cycle

First-stage larvae (rhabditiform) are short and non-infective
Third-stage larvae (filariform) are longer and infective.
Filariform larvae penetrate the skin, enter the bloodstream, and migrate to the lungs
The larvae travel up the trachea and are swallowed
They reach the small intestine and mature into adult hookworms.
Adult females produce eggs, which are passed in the feces.

Pathogenesis

Mild infection is typically asymptomatic
Severe infection can lead to nausea, fatigue, vomiting, abdominal pain, anorexia, diarrhea, and iron-deficiency anemia.
Skin penetration may lead to a skin lesion called cutaneous larva migrans.

Filariform Larvae

Third-stage larvae are 500-700 µm long
Rapid penetration of the skin (most frequently the feet) occurs after 5+ minutes of skin contact with soil containing viable larvae.
They feed by puncturing and feeding on capillaries in the jejunum.
A localized ground itch may accompany penetration.
Penetration is more common with Ancylostoma compared to Necator

Signs and Symptoms - Pruritus

Early symptoms vary with exposure intensity
Necator causes local irritation (ground itch) at the skin invasion site
Skin reaction might be intensely pruritic, erythematous, or vesicular, and often on the feet or hands.
Differentiate from creeping eruptions due to cat or dog hookworms (Ancylostoma braziliense)

Loeffler's Syndrome

Larvae burrow into lung venules and embolize into alveoli
It is a mild, usually asymptomatic, alveolitis associated with eosinophilia.
Hookworms are one of the causes of pulmonary infiltrates and eosinophilia (PIE) syndrome, along with nematodes like Ascaris and Strongyloides species.
Common symptoms include fever, malaise, cough, wheezing, and dyspnea.
Coughing helps larvae reach the mouth and are then swallowed to the intestine

Hookworm Lifespan

Necator has a 5-year lifespan
Ancylostoma has a 1-year lifespan
As worms mature in the jejunum, patients can experience diarrhea, vague abdominal pain, colic, and/or nausea

Intestinal Symptoms and Anemia

Maturing worms in the jejunum can cause diarrhea, general abdominal pain, colic, and nausea.
Severe iron-deficiency anemia may lead to related factors like headache, palpitations, shortness of breath, and edema.
Each Necator worm ingests 0.03 mL of blood daily, whilst each Ancylostoma worm ingests 0.2 mL per day

Anemia

Host anemia is proportional to diet, iron reserves, and worm burden.
Threshold worm load for producing anemia varies geographically, ranging down to 40 worms in areas with low iron intake.
Severe anemia leads to impaired intellectual and physical development in children.
It can also result in cardiovascular complications in adults.
Young women, especially pregnant women and agricultural laborers are more prone to symptomatic anemia.

Diagnosis & Treatment

Diagnosis involves finding ova or larvae in feces. Use stool culture (Harada-Mori technique) helps distinguish larval varieties (e.g. hookworm and Strongyloides)
Treatment options include albendazole and mebendazole.
Preventative measures include wearing shoes or gloves when working outdoors in areas with contamination.

Cutaneous Larva Migrans

Animal hookworm larvae cause creeping eruptions (cutaneous larva migrans), characterized by serpentine skin lesions
Cutaneous larva migrans (CLM) is a skin disorder in humans caused by various hookworm larvae.
CLM is literally "wandering larvae in the skin"
Common causative species include Ancylostoma braziliense, Ancylostoma ceylanicum, and Ancylostoma caninum. (dog and cat hookworms)
The infection manifests as a pruritic red skin eruption typically seen on the feet or hands.

Strongyloides stercoralis

It is a common enteric helminthic parasite globally that often manifests as asymptomatic or mild gastrointestinal symptoms
In immunocompromised individuals infection can be severe, with mortality rates near 60-85%.

Strongyloides stercoralis Life Cycle

Larvae exist in two forms: filariform (infective) and rhabditiform (free-living)
Infection results from skin contact with contaminated soil
The larvae penetrate the skin and migrate to the lungs
The larvae travel up the respiratory tract and are swallowed
They mature to adult females in the small intestine
Adult females are parthenogenic (self-fertilizing) to produce eggs
The eggs typically develop into rhabditiform larvae and are excreted in the feces
Larvae may develop into filariform larvae leading to autoinfection

Skin Lesions

Skin penetration by infective larvae can cause ground itch, characterized by a pruritic papulovesicular eruption typically on feet or any area exposed to contaminated soil.
A characteristic lesion of Strongyloides infection is the larva currens, a serpiginous urticarial rash creeping across the skin.
Allergic response or pruritic wheals/linear urticaria may be associated with migrating larvae.

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Description

Test your knowledge on hookworm infections with this quiz. Explore the life cycle, symptoms, and pathogenesis associated with hookworm larvae. Assess your understanding of how these parasites affect human health and the mechanisms behind their effects.