Historically, hookworm infection has disproportionately affected the poorest among the least-developed nations, largely as a consequence of inadequate access to clean water, sanitation, and health education.
- Human hookworm disease is a common helminth infection that is predominantly caused by the nematode parasites Necator americanus and Ancylostoma duodenale; organisms that play a lesser role include Ancylostoma ceylonicum, Ancylostoma braziliense, and Ancylostoma caninum.
- Hookworm infection is acquired through skin exposure to larvae in soil contaminated by human feces.
- Soil becomes infectious about 9 days after contamination and remains so for weeks, depending on conditions.
The life cycle of hookworms begins with the passing of hookworm eggs in human feces and their deposition into the soil.
- Each day in the intestine, a mature female A duodenale worm produces about 10,000-30,000 eggs, and a mature female N americanus worm produces 5000-10,000 eggs.
- After deposition onto soil and under appropriate conditions, each egg develops into an infective larva.
- These larvae are developmentally arrested and nonfeeding; if they are unable to infect a new host, they die when their metabolic reserves are exhausted, usually in about 6 weeks.
- Larval growth is most proliferative in favorable soil that is sandy and moist, with an optimal temperature of 20-30°C; under these conditions, the larvae hatch in 1 or 2 days to become rhabditiform larvae, also known as L1.
- The rhabditiform larvae feed on the feces and undergo 2 successive molts; after 5-10 days, they become infective filariform larvae or L3.
- These L3 go through developmental arrest and can survive in damp soil for as long as 2 years; however, they quickly become desiccated if exposed to direct sunlight, drying, or salt water. L3 live in the top 2.5 cm of soil and move vertically toward moisture and oxygen.
- The larvae migrate through the dermis, entering the bloodstream and moving to the lungs within 10 days; once in the lungs, they break into alveoli, causing a mild and usually asymptomatic alveolitis with eosinophilia.
- In 3-5 weeks, the adults become sexually mature, and the female worms begin to produce eggs that appear in the feces of the host.
Statistics and Incidences
Worldwide, hookworms infect an estimated 472 million people.
- Hookworm infection and disease are now most likely to be found in immigrants, refugees, and adoptees from tropical countries.
- Cutaneous larva migrans is endemic in the southeastern states and Puerto Rico; the canine hookworm A caninum has reportedly caused eosinophilic enteritis in Australia and the United States.
- Human infection with A duodenale or N americanus is estimated to affect approximately 472 million people worldwide.
- Infection is most prevalent in tropical and subtropical zones, roughly between the latitudes of 45°N and 30°S; in some communities, prevalence may be as high as 90%.
- In 2010, it was estimated that 117 million individuals in sub-Saharan Africa were infected with hookworms, as well as 64 million in East Asia, 140 million in South Asia, 77 million in Southeast Asia, 30 million in Latin America and the Caribbean, 10 million in Oceania, and 4.6 million in the Middle East and North Africa.
- In endemic areas, the highest prevalences are reported among school-aged children and adolescents, possibly because of age-related changes in exposure and the acquisition of immunity.
- Studies from China and Brazil indicate a consistently increasing prevalence, from 15% at age 10 years to 60% at age 70 years and older; egg counts in stool also increase in a similar pattern.
- Males and females are equally susceptible to hookworm infection.
Hookworms may persist for many years in the host and impair the physical and intellectual development of children and the economic development of communities.
- Necator americanus. N americanus is the globally predominant human hookworm and is the only member of its genus known to infect human; it is a small, cylindrical, off-white worm; adult males measure 7-9 mm, and adult females measure 9-11 mm.
- Poor sanitation. Poor hygiene habits and sanitation contribute to the development of hookworm infestations as they thrive in dirty, unkempt surroundings.
- Limited access to clean water. Ingestion of water infested with eggs of hookworms leads to the development of hookworm in humans.
The early and late signs of hookworm infection are:
- Ground or dew itch. An erythematous, pruritic, papulovesicular rash develops at the site of initial infection on the palms or soles and may persist for 1-2 weeks after initial infection; intense scratching may lead to a secondary bacterial infection, which is quite common.
- Pulmonary symptoms. When the worms break through from the venous circulation into the pulmonary air spaces, cough, fever, and a reactive bronchoconstriction may be observed, with wheezing heard on auscultation.
- GI symptoms. Migration of the worms into the gastrointestinal (GI) tract may cause GI discomfort secondary to irritation; as the worms mature in the jejunum, patients may experience diarrhea, vague abdominal pain, colic, flatulence, nausea, or anorexia.
- Symptoms of anemia. Signs of iron-deficiency anemia are often insensitive.; patients may exhibit pallor, chlorosis (greenish-yellow skin discoloration), hypothermia, spooning nails, tachycardia, or signs of high-output cardiac failure.
- Cutaneous larva migrans. Cutaneous larva migrans manifests as pathognomonic, raised serpiginous tracts (creeping eruptions) with surrounding erythema that may last as long as 1 month if untreated; lesions are most commonly seen on lower extremities but may be limited to the trunk or upper extremities, depending on the site at which the infective larvae entered the body.
Assessment and Diagnostic Findings
Diagnosis of hookworm infection is made through the following:
- Blood studies. Anemia is confirmed by CBC and peripheral blood smear results that demonstrate signs typical of iron-deficiency anemia; microscopy reveals hypochromic, microcytic red blood cells (RBCs); eosinophilia is surprisingly persistent and may be due to attachment of the adult worms to the intestinal mucosa.
- Stool examination. The diagnosis is confirmed with direct microscopic analysis of fecal samples to verify the presence of hookworm eggs; the specimen is fixed in formalin and prepared as a wet mount.
Most cases of classic hookworm disease can be managed on an outpatient basis with anthelmintic and iron therapy, complemented by an appropriate diet.
- Iron therapy. Patients with anemia and malnutrition may require both iron supplements and nutritional support (including folate supplementation).
- Antihelmintics. For patients with cutaneous larva migrans who have minimal symptoms, specific anthelmintic treatment may be unnecessary.
- Blood transfusions. Blood transfusion is indicated in rare cases of acute severe gastrointestinal (GI) hemorrhage; in patients with chronic anemia, blood transfusions (ie, packed red blood cells [RBCs]) should be administered slowly and are usually followed by a diuretic to prevent rapid fluid overload.
Antihelmintics are the drug of choice for hookworm infections.
- Antihelmintics. Anthelmintic drugs effective against hookworms include benzimidazoles (eg, albendazole, mebendazole) and pyrantel pamoate; the Centers for Disease Control and Prevention (CDC) continues to recommend a 400-mg single dose of albendazole on its Website (July 26, 2018), but notes that albendazole is still not FDA approved for the treatment of hookworm infection.
Nursing care for a child with hookworms include the following:
Assessment of the child include:
- History. The majority of individuals who develop hookworm infection are from known endemic areas; they frequently have a history of wearing open footwear or walking barefoot in such areas.
- Physical exam. Skin and pulmonary findings are minimal; physical findings in the early (larval migration) stage of the disease differ from those in the late (established GI infection) stage.
Based on the assessment data, the major nursing diagnoses are:
- Acute pain related to mucosal irritation.
- Ineffective tissue perfusion related to blood loss.
- Impaired skin integrity related to persistent scratching of the affected area.
- Deficient knowledge related to the disease process and treatment.
Nursing Care Planning and Goals
The major nursing care planning goals for patients with hookworm are:
- The child will have diminished pain.
- The child’s perfusion will return to normal.
- The child will have reduced itching and scratching.
- The child and caregivers will acquire enough knowledge about the disease process and its treatment.
Nursing interventions for a child with hookworm include the following:
- Reduce or diminish pain. Provide rest periods to promote relief, sleep, and relaxation; acknowledge reports of pain immediately; get rid of additional sources of discomfort, and determine the appropriate pain relief method.
- Improve tissue perfusion. Submit patient to diagnostic tests as indicated; administer blood transfusion as indicated.
- Protect skin integrity. Monitor site of impaired tissue integrity at least once daily for color changes, redness, swelling, warmth, pain, or other signs of infection; provide skin care as needed; keep a sterile dressing technique during wound care; clip the patient’s nails as necessary; and teach patient and significant others about proper handwashing, wound cleansing, dressing changes, and application of topical medications.
- Enforce knowledge about the disease and its treatment. Determine priority of learning needs within the overall care plan; render physical comfort for the patient; grant a calm and peaceful environment without interruption; include the patient in creating the teaching plan; help the patient in integrating information into daily life; and provide clear, thorough, and understandable explanations and demonstrations.
Goals are met as evidenced by:
- The child’s pain was diminished.
- The child’s perfusion is returned to normal.
- The child has reduced itching and scratching.
- The child and caregivers have acquired enough knowledge about the disease process and its treatment.
Documentation in a child with hookworm include the following:
- Individual findings, including factors affecting, interactions, nature of social exchanges, specifics of individual behavior.
- Cultural and religious beliefs, and expectations.
- Plan of care.
- Teaching plan.
- Responses to interventions, teaching, and actions performed.
- Attainment or progress toward the desired outcome.