Hookworm Infections and Anemia Quiz

Soil-Transmitted Helminths (STH 2)

• Hookworms are a type of STH
• Two important species are Ancylostoma duodenale and Necator americanus
• These hookworms infect 576-740 million people globally
• Anemia occurs in approximately 10% of infected individuals
• Hookworms can persist for years, hindering physical and intellectual development in children and impacting community economic development
• Hookworm infections are prevalent in tropical and subtropical regions, particularly in rural communities with poor sanitation, like moist soil and lack of latrines
• Agricultural laborers are at higher risk of infection
• Epidemiologic factors include improper waste disposal and the practice of walking barefoot

Hookworm Distribution

• Hookworms are widespread throughout tropical and subtropical areas
• Prevalence in some communities is as high as 90%
• Rural areas with moist soil and inadequate latrines are breeding grounds for hookworm
• Agricultural laborers face a higher infection risk

Demographic Prevalence

• Hookworm infection is often linked to poverty, poor housing, and inadequate sanitation
• Limited access to essential medications also contributes to higher infection rates in these populations
• As countries develop, these conditions improve, and hookworm infection rates decrease

Route of Infection

• Hookworm infection occurs via skin penetration by larvae in soil contaminated with human feces.
• Adults, particularly agricultural workers, exhibit comparable or higher susceptibility to exposure compared to children

Hookworm Characteristics

• Adult hookworms measure 10-15mm in length
• These worms possess buccal capsules, which are crucial for attachment to the intestinal mucosa
• Ancylostoma duodenale possesses two pairs of teeth, whereas Necator americanus has cutting plates.

Hookworm Ova Characteristics

• The ova of both species are morphologically similar in appearance
• They are characterized by thin, clear, smooth, colorless shells, encapsulating the embryo

Hookworm Prevalence Map

• The prevalence map visually displays the global distribution of hookworms, indicating regions with varying infection rates.

Hookworm Larval Development

• The first stage larva (rhabditiform) is short and non-infective. The third stage larva (filariform) is longer and infective.
• The filariform larva penetrates the skin to initiate infection
• Filariform larvae are not able to exist independently; they require a host to complete their life cycle
• Larvae undergo a cycle of development in soil, and through exposure, they gain entry into the body
• The resulting migration of those larvae proceeds to travel to the lung, trachea, and throat in order to be swallowed, which then results in their eventual arrival and anchorage to the small intestine, where they attach to the intestinal mucosa and consume blood

Hookworm Pathogenesis

• Mild infections are generally asymptomatic
• Moderate to severe infections can cause a range of symptoms
• These include skin lesions (cutaneous larva migrans), nausea, fatigue, vomiting, abdominal pain, anorexia, diarrhea, and iron deficiency anemia

Hookworm Larvae

• Third-stage larvae are 500-700 µm long and adept at penetrating skin, primarily on the feet.
• Transmission takes place 5 minutes or more after skin contact with contaminated soil
• Larvae puncture and feed on mucosal capillaries in the jejunum, and a condition called ground itch at the site of penetration is prevalent in Ancylostoma compared to Necator

Hookworm Signs and Symptoms

• Early symptoms are proportional to the intensity of exposure
• Necator infection manifests as a local irritation (ground itch) at the skin invasion site.
• Skin rash (intensely pruritic, erythematous, or vesicular) can appear on the feet and hands
• Symptoms should be differentiated with other similar skin conditions, including those caused by dog and/or cat hookworm (Ancylostoma braziliense)

Loeffler's Syndrome

• Hookworm larvae burrow into venules, embolize, and break into alveoli, leading to a mild, asymptomatic alveolitis
• Eosinophilia accompanies this condition (PIE syndrome, also associated with Ascaris and Strongyloides).
• Common symptoms include fever, malaise, cough, wheezing, and dyspnea.

Reproduction in Hookworms

• Approximately 5-10 weeks after skin penetration, adult female hookworms begin egg production.
• Necator has a lifespan of 5 years; Ancylostoma has a lifespan of 1 year.
• Diarrhoea, vague abdominal pain, colic, and/or nausea may occur as worms mature in the jejunum.
• Severe iron-deficiency anemia may manifest with symptoms such as headache, palpitations, dyspnea, and edema
• Each Necator worm consumes ~0.03mL of blood per day; Ancylostoma worms ingest ~0.2mL of blood per day

Anemia

• Host anemia occurrence is proportional to dietary iron reserves and hookworm burden
• Anemia can result from as few as 40 worms, particularly in regions with low iron consumption.
• Anemia can negatively affect intellectual and physical development in children and cardiovascular health in adults.
• Infection is most damaging to women of childbearing age and laborers

Diagnosis and Treatment (Hookworms)

• Diagnosis involves identifying ova or larvae in feces using stool culture techniques
• Specifically, a Harada Mori or similar method might be used
• Treatment options include Albendazole and Mebendazole.
• Prevention involves proper sanitation strategies like shoe-wearing, or using gloves when working outdoors.

Hookworm Family (Cutaneous Larva Migrans - CLM)

• Some animal hookworm larvae can cause serpentine skin lesions called cutaneous larva migrans or creeping eruptions
• CLM is a skin disease, caused by certain hookworm nematodes
• CLM is characterized as "wandering larvae in the skin"
• Common hookworm species include Ancylostoma braziliense, Ancylostoma ceylanicum, and Ancylostoma caninum, which parasitize dogs and cats.
• The condition appears as a creeping eruption, resembling "ground itch", or "sandworms" due to the larvae's preference for sandy soil

Presentation and Treatment of CLM

• Hookworm infection causes red and intensely itchy eruptions.
• Itching can become painful and lead to secondary bacterial infections
• Treatment is necessary when the infection's symptoms develop and progress to the itching stage
• Treatment methods often involve drugs like Albendazole or Ivermectin orally, or using topical Thiabendazole, topical freezing agents (such as ethyl chloride or liquid nitrogen)
• Common ways to avoid hookworm infections include wearing gloves or shoes when working outdoors

Strongyloides stercoralis

• Strongyloides stercoralis is a common enteric parasite with worldwide significance
• Infections are often asymptomatic, or present with mild intestinal symptoms.
• In immunocompromised individuals (Strongyloides stercoralis) infections can be severe, with a high mortality rate (60-85%).

Strongyloides stercoralis Life Cycle

• Strongyloides larvae exist in two forms: free-living rhabditiform larvae that survive in soil and filariform larvae (infective stage).
• Infection occurs when exposed skin contacts contaminated soil. Larvae penetrate, migrating to the lungs, trachea, and pharynx, thereafter being swallowed and reaching the small intestine
• Larvae mature into adult females in the small intestine and reproduce asexually, or parthenogenetically.
• Each adult female can live up to 5 years and continue reproduction
• Eggs are transformed into rhabditiform larvae within the intestine, and some are excreted in feces.
• Rhabditiform larvae can develop into filariform larvae in the intestines, potentially entering the perianal skin and leading to autoinfection

Strongyloides stercoralis Epidemiology

• Strongyloides stercoralis is endemic in tropical and subtropical regions
• Sub-Saharan Africa, South and Southeast Asia, Central America, and parts of Eastern Europe are affected.
• Worldwide prevalence is estimated at 2-20% in endemic areas
• These are particularly susceptible to infection during childhood, due to the likelihood of skin contact with contaminated soil when playing outdoors

Strongyloides stercoralis Pathogenesis

• Skin penetration may cause allergic reactions, rash, or itchy eruptive lesions.
• Strongyloides infection in people can cause diarrhea and abdominal pain, vomiting and weight loss during lung migration
• Autoinfection, leading to hyperinfection syndrome (often serious and deadly), especially in immunocompromised individuals.
• Larvae may be found in multiple organs, including lungs, liver, and heart

Strongyloides stercoralis Diagnosis and Treatment

• Identification of rhabditiform or filariform larvae in human feces is crucial for diagnosis
• Stool culture methods (Harada Mori or Sand technique) are often employed
• Treatment includes Thiabendazole, along with preventive measures similar to those for hookworm infections

Test your knowledge on the relationship between hookworm infections and anemia. This quiz covers symptoms, treatment, and demographic factors influencing these infections. Explore the economic and health impacts of hookworms on vulnerable populations.