Human Parasitology: Hookworm Infections

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Questions and Answers

What initiates the infection process of hookworms in humans?

Ingestion of contaminated food

Exposure to contaminated water

Penetration of skin by filariform larvae (correct)

Airborne transmission of larvae

What is a significant consequence of heavy hookworm infection?

Increased appetite

Skin rash resolution

Iron deficiency anemia (correct)

Rapid weight gain

Where do the adult hookworms mature after penetrating the skin?

In the small intestine (correct)

In the liver

In the colon

In the lungs

What symptom is more common with Ancylostoma species than with Necator hookworms?

Ground itch Signup and view all the answers

What is the primary mechanism by which filariform larvae cause pulmonary infiltrates?

Embolization from venules Signup and view all the answers

Which of the following is true about the filariform larvae of hookworms?

They are not infective until they penetrate skin. Signup and view all the answers

What is a common early symptom of hookworm infection?

Pruritus at the site of penetration Signup and view all the answers

What is the size range of third-stage filariform larvae?

500-700 µm Signup and view all the answers

How long does Necator typically live in the host?

5 years Signup and view all the answers

What is a common symptom associated with iron-deficiency anemia from hookworm infection?

Nausea Signup and view all the answers

Which of the following is a method for diagnosing hookworm infection?

Stool culture using the Harada Mori technique Signup and view all the answers

What is the primary treatment for hookworm infections?

Albendazole and Mebendazole Signup and view all the answers

What describes cutaneous larva migrans?

A skin condition caused by hookworm larvae Signup and view all the answers

Which demographic is most susceptible to symptomatic anemia related to hookworm infections?

Young women, particularly those who are pregnant Signup and view all the answers

Which of the following species is NOT associated with causing cutaneous larva migrans?

Necator americanus Signup and view all the answers

How much blood does each Ancylostoma worm consume daily?

0.2 mL Signup and view all the answers

What condition can result from scratching due to itching caused by Strongyloides stercoralis?

Secondary bacterial infection Signup and view all the answers

What treatment is considered effective for Strongyloides stercoralis infection?

Albendazole or Ivermectin Signup and view all the answers

In immunocompromised individuals, what is the mortality rate associated with Strongyloides stercoralis infection?

60-85% Signup and view all the answers

What form of larvae does Strongyloides stercoralis secrete in feces?

Rhabditiform larvae Signup and view all the answers

How can infection with Strongyloides stercoralis occur?

Exposure of skin to contaminated soil Signup and view all the answers

After larvae penetrates the skin, where do they migrate first?

Pulmonary circulation Signup and view all the answers

What is a characteristic of the adult female Strongyloides stercoralis?

Undergoes parthenogenic reproduction Signup and view all the answers

Under certain conditions, where can Strongyloides larvae molt into infective filariform larvae?

Within the intestinal lumen Signup and view all the answers

What is the primary route of infection for hookworms?

Skin penetration by larvae in contaminated soil Signup and view all the answers

Which population is at higher risk for hookworm infection?

Agricultural laborers Signup and view all the answers

What is a significant consequence of hookworm infection?

Anemia in approximately 10% of those infected Signup and view all the answers

What differentiates the buccal capsules of Ancylostoma duodenale from those of Necator americanus?

A. duodenale has teeth whereas N. americanus has cutting plates. Signup and view all the answers

In what geographical areas is hookworm infection most prevalent?

Tropical and subtropical areas Signup and view all the answers

What characteristic of hookworm larvae makes them infective?

They are longer and able to penetrate skin. Signup and view all the answers

What has been observed in countries as they develop with regard to hookworm infestations?

Infections decrease with improvements in sanitation. Signup and view all the answers

Which of the following best describes the ova of hookworms?

They have a thin, clear, smooth, colorless shell enclosing the embryo. 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

Which of the following regions is NOT considered endemic for Strongyloides infection?

Northern Europe Signup and view all the answers

What symptom is commonly associated with skin penetration by Strongyloides infective larvae?

Ground itch Signup and view all the answers

How does the filariform larva enter the body to cause infection?

Penetration of the skin Signup and view all the answers

Which of the following best describes the rash known as larva currens?

A serpiginous urticarial rash Signup and view all the answers

What is a significant risk factor for the initial occurrence of Strongyloides infection?

Playing outdoors in contaminated soil Signup and view all the answers

What does the term hyperinfection refer to in the context of Strongyloides?

An accelerated autoinfectious cycle Signup and view all the answers

What percentage of the population might be infected with Strongyloides in endemic areas?

2-20% Signup and view all the answers

Study Notes

Soil Transmitted Helminths (STH 2)

STH are parasitic worms transmitted through soil contaminated with human feces.
Two main species of hookworms are Ancylostoma duodenale and Necator americanus.
Hookworms infect an estimated 576-740 million people, causing anemia in about 10% of infected individuals.
Infection can persist for many years, impairing physical and intellectual development of children, and impacting economic communities.
Hookworms are widely distributed in tropical and subtropical regions, with prevalence in some communities reaching 90%.
Rural communities, often with poor sanitation and moist soil, see high hookworm prevalence.
Agricultural workers are traditionally at high risk of hookworm infection due to exposure.

Hookworm Distribution

Hookworm transmission is linked with inadequate sanitation, poor housing, lack of access to medical care, and generally poor socioeconomic conditions.
Infection frequency often drops as countries improve economically.
Prevalence greatly influences hookworm presence.

Hookworm Route of Infection

Hookworm infection occurs through skin penetration by larvae found in soil contaminated with human feces.
Adults, specifically agricultural workers, face a comparable or greater risk of exposure than children.
The infection route is important to hookworm epidemiology.

Hookworms

Two significant species are Necator americanus and Ancylostoma duodenale.
Adult hookworms are 10-15mm in size.
Hookworms possess buccal capsules that aid in their attachment to the intestinal mucosa.
Ancylostoma duodenale possesses two pairs of teeth; Necator americanus has cutting plates, enabling firm intestinal mucosal attachment.

Hookworm Eggs

The eggs of Ancylostoma duodenale and Necator americanus are similar in morphology.
The eggs have a thin, clear, smooth, and colorless shell that encapsulates the embryo.

Hookworm Life Cycle

The first-stage larva (rhabditiform larva) is short and non-infective in the soil.
The third-stage larva (filariform larva) is longer and more infectious.
The larvae penetrate the skin to initiate the infection.

Hookworm Larval Development

Migrating larvae enter the alveoli, are carried to the bronchi and trachea, and are swallowed.
The larvae then attach to the small intestine and feed on blood.
The infection occurs through skin penetration with the larvae, then migration through the circulatory system, and onto the lungs.
Rhabditiform larvae develop into filariform larvae in the soil.
Hookworm Life Cycle

Hookworm Pathogenesis

Mild infections usually do not cause symptoms.
Heavy infections can cause nausea, fatigue, vomiting, abdominal pain, anorexia, diarrhea, and iron deficiency anemia.
Larval migration through skin, potentially resulting in cutaneous larva migrans (CLM).
Severe anemia affects intellectual and physical development in children and cardiovascular performance in adults.

Hookworm Diagnosis and Treatment

Diagnosis involves identifying eggs or larvae in feces.
Stool cultures use the Harada-Mori technique.
Therapy includes albendazole, mebendazole, and others.
Prevention measures include wearing shoes, gloves when working outdoors, and proper sanitation practices.

Cutaneous Larva Migrans (CLM)

Animal hookworm larvae, like Ancylostoma braziliense, Ancylostoma ceylanicum, and Ancylostoma caninum, can cause serpentine skin lesions known as CLM or creeping eruptions.
CLM is a skin condition caused by hookworm larvae, and the larvae are often found in sandy soil.
Characteristic skin lesions include itching, erythema, or blisters.

Strongyloides stercoralis

Strongyloides stercoralis is a common enteric helminth of global importance.
Typically, infection is asymptomatic or causes mild gastrointestinal symptoms.
Immunocompromised individuals often experience significantly severe infections, with a high mortality rate (60-85%).
Strongyloides stercoralis larvae exist in two forms: filariform (infective) and rhabditiform (free living).
Infection occurs when exposed skin contacts contaminated soil, causing the larvae to penetrate the skin, and migrate to the lungs. Upon migration to the lungs, the larvae migrate directly to the intestinal system and mature into adult females and reproduce parthenogenetically.
Larvae are often found in feces approximately one month after skin penetration.
Under certain conditions, like constipation and decreases in bowel motility, larvae can return to the small intestine in a process called autoinfection.

Strongyloides stercoralis Life Cycle

The cycle repeats and can potentially result in recurrent or continuous infection.
Feces typically contain rhabditiform larvae, and not eggs
Strongyloides stercoralis Life Cycle

Strongyloides stercoralis Pathogenesis

Skin penetration may cause allergic reactions or eruptions like larva currens
Symptoms of infection may include diarrhea, abdominal pain, vomiting, weight loss, and pulmonary symptoms, such as a cough and shortness of breath.
Autoinfection can lead to hyperinfection syndrome, particularly in immunocompromised individuals (e.g., HIV/AIDS).
Larvae can be found in multiple organs like in the lungs, liver, and the heart.

Strongyloides stercoralis Diagnosis and Treatment

Diagnosis often requires identifying rhabditiform or filariform larvae in human feces, which can be achieved via stool culture or "Harada Mori" method or "Sand culture".
Treatment typically involves thiabendazole.
Prevention measures include proper sanitation practices and avoiding walking barefoot in areas with contaminated soil.

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Test your knowledge on hookworm infections in humans with this quiz. Questions cover initiation of infection, symptoms, treatment, and diagnosis associated with hookworms. Perfect for students of human parasitology or those interested in infectious diseases.