Ancylostomiasis: causes, symptoms, diagnosis, and treatment

Ancylostomiasis, also known as hookworm disease, is a disease caused by hookworms parasitizing the human small intestine, and mainly manifested by anemia, malnutrition, and gastrointestinal dysfunction.


Causes

Hookworms that parasitize humans are mainly Ancylostoma duodenale and Necator americanus, occasionally Ancylostoma ceylanicum and Ancylostoma caninum. Although the infective larvae of Ancylostoma braziliense can invade the human body, they generally cannot develop into adults.

Epidemiology

Source of infection

The source of infection is patients with hookworm disease or infected by hookworms.

Route of transmission

The main route is skin contacts, and the interdigital skin is the most common site of invasion. Infections may result from oral exposures if there are ingestions of raw contaminated vegetables.


Signs and Symptoms

Cutaneous larva migrans

Pruritus, edema, erythema may occur within 20 - 60 minutes on the site invaded by hookworms, progressing into papules, especially on the interdigital skin, soles, and dorsal hands. The skin lesions develop into vesicles within 1 - 2 days, generally subside spontaneously in 1 week. If scratched, secondary bacterial infection may occur and recovery may be delayed.

Pneumonia

When the hookworm larvae migrate through the lungs, punctate hemorrhage and inflammation in the lungs may occur. Cough, expectoration, blood-tinged sputum, fever, or asthma usually occur 3 - 5 days after infection, and there is eosinophilia, resembling simple pulmonary eosinophilia, also known as Löffler syndrome. In severe cases, chest pain, severe dry cough, and asthma-like attacks may occur. Chest X-ray shows increased pulmonary vascular markings or prominent hilar shadow, occasionally infiltrating lesions. The severity of symptoms is related to the count of the hookworm larvae, and symptoms subside spontaneously several to dozens of days after infection.

Gastrointestinal symptoms

There are bulimia, fatigue, and tiredness initially. If the intestinal wall is damaged by the hookworms, there may be chronic inflammation, manifested by nausea, vomiting, abdominal pain, diarrhea, and occult blood in the stool. Occasionally, adult hookwoarms parasitize the rectum, causing blood in the stool. Discomfort in the upper abdomen, relieved after pressing or after meals, is often erroneously diagnosed as ulcer. Allotriophagy may be present in some patients. Severe anemia may result in hypochlorhydria, indigestion, and papillary atrophy of the tongue.

Video 1 hookworms and hookworm disease

Anemia

Hookworms adhered to the intestinal wall, long-term blood sucking, and continuous bleeding from the bites result in hematozemia, malnutrition, and intestinal dysfunction, leading to iron deficiency anemia. In patients with hemoglobin > 90g/L, there are mild paleness, fatigue, tiredness, hypohidrosis, and brittle hair, as well as palpitation, dyspnea, dizziness, and giddiness during work. In patients with hemoglobin of 50 - 90g/L, there are obvious pale skin, mucous membranes, and nails; edema of lower limbs, and adiaphoresis; as well as palpitation, dyspnea, rapid pulse, mild heart enlargement, and systolic murmurs during motions. In patients with hemoglobin<50g/L, there are severe anemia, facial edema and paleness; palpitation and dyspnea even during a rest; sometimes accompanied by discomfort or pain in the precordial area, tinnitus, giddiness, pitting edema, obvious enlargement of the heart, fast heart rate, systolic and diastolic murmurs, pulmonary rales, and liver enlargement and tenderness. Although some patients have severe anemia, their symptoms are not obvious due to the slow development and good compensation. However, once there are infection, pregnancy, or childbirth, the symptoms are significant.

Hookworm disease in infants

The age of onset is mostly 10 - 12 months, as early as 3 days after birth, and some infants discharge immediately blackish green stools after birth. The most prominent clinical symptoms are acute bloody diarrhea, black stools, and paleness, followed by lassitude, anorexia, vomiting, diarrhea, and fever. There is a poor prognosis, with a fatality rate of 3.6% - 6.0%, up to 12%.


Diagnosis

If there are clinical presentations and hookworm eggs or larvae detected from the stools, the disease can be diagnosed.


Treatment

The treatment regimen is albendazole 400mg orally once a day or ivermectin 200mcg/kg, orally once a day for 3 - 7 days.

For severe infections, supportive treatment for iron deficiency anemia should be performed.