Infectious Diseases & Parasitology & Travel Medicine
Hookworm infection and hookworm disease
Hookworm disease and ancylostomiasis are two soil-transmitted helminthiases (soil-transmitted parasitic infections) caused respectively by Necator americanus and Hookworm (Old World), two hematophagous nematodes of the hookworm family whose adults inhabit the duodenum and proximal jejunum of the human host and feed on blood by attaching to the intestinal mucosa with their buccal capsule. With an estimated global prevalence of 500 to 800 million infected individuals—almost all of whom are in the tropical and subtropical regions of sub-Saharan Africa, Southeast Asia, South Asia, Central America, and South America, where hygiene conditions and contact with soil contaminated by human feces are favorable for transmission—hookworm infections represent one of the most widespread parasitic infections in the world and one of the main causes of iron deficiency anemia and malnutrition in school-aged children and pregnant women in low-resource countries. In Quebec and Canada, both *Necatoriasis* and *Ancylostomiasis* are almost exclusively imported parasitic diseases, diagnosed in travelers returning from endemic regions, immigrants and refugees from tropical areas, and aid workers. Transmission occurs through active penetration of infective larvae (filariform larvae L3) through intact skin upon contact with soil contaminated by human feces—walking barefoot on warm, humid tropical soil and lying on a beach or dirt floor being the most frequent modes of exposure. The parasitic load determines the clinical severity: mild to moderate infections are often asymptomatic or mildly symptomatic, while massive infections can lead to severe iron deficiency anemia, hypoproteinemia, and growth retardation in children. Cutaneous larva migrans, a spectacular clinical syndrome of erythematous and pruritic tracts progressing under the skin, is caused by Ancylostoma braziliense (hookworm of cats and dogs) which does not complete its cycle in humans.
Parasitic cycle and transmission mechanisms
- Environmental phase (soil): Hookworm eggs are eliminated in human feces (3,000–10,000 eggs/worm/day) + in warm (optimal 23–30°C) + moist + shaded soil → embryonation in 24–48 hours → hatching → rhabditiform larvae L1 → two molts → infective filariform larvae L3 in 5 to 7 days + L3 larvae survive in soil up to 3 to 4 weeks and actively migrate to the surface.
- Skin penetration and larval migration: L3 larvae actively penetrate intact skin upon contact with soil + preferred sites: interdigital spaces of feet + soles of feet + ankles + migration into lymphatic and venous circulation → lungs → pulmonary capillaries (pulmonary phase: cough + transient eosinophilia) → ascent to the trachea → swallowing → small intestine where they attach to the mucosa
- Intestinal phase and hematophagy: duodenojejunal mucosal fixation with the oral capsule equipped with cutting platesNecator) or teeth (Ancylostoma) → active aspiration of blood by regularly changing the anchor site → each adult worm ingests 0.03 mL (Necator) at 0.2 mL (Ancylostoma) blood loss per day → iron and hemoglobin loss proportional to parasite load → onset of egg laying 6 to 8 weeks after infection
- Ingestion transmissionHookworm (Old World) only) : unlike Necator americanus, A. duodenale can also be transmitted by ingestion of L3 larvae in contaminated food or water → direct enteric cycle without obligatory pulmonary passage + transplacental and maternal milk transmission documented for A. duodenale
- Cutaneous larva migransAncylostoma braziliense) : Hookworm larvae of domestic carnivores (cats + dogs) penetrate human skin but cannot complete their cycle (no visceral penetration in the unnatural host) → migrate in the superficial dermis at 1–5 cm per day → characteristic serpiginous erythematous and pruritic track → spontaneous resolution in a few weeks without treatment but albendazole or ivermectin accelerate healing
Clinical Presentation by Stage and Parasitic Load
| Stage and clinical presentation | Manifestations and characteristics | Duration and evolution |
|---|---|---|
| Dermatitis of invasion (ground itch) | Intense itching + redness + papules + vesicles at the site of skin penetration (interdigital spaces + soles of feet) within the first hours to days following contact with contaminated soil + often overlooked due to rapid spontaneous resolution + can be mistaken for contact dermatitis or insect bites | 1 to 2 weeks + spontaneous resolution + no specific treatment needed at this stage unless antihistamines for intense itching |
| Pulmonary phase (Löffler's syndrome) | Dry cough + wheezing + mild shortness of breath + moderate fever + elevated blood eosinophil count (may exceed 30–40% of total white blood cells) → as the larvae pass through the pulmonary capillaries + chest X-ray: transient bilateral labile infiltrates (Löffler’s syndrome) | 1-2 weeks + spontaneous resolution as larvae migrate to the intestine + maximum eosinophilia at 4-6 weeks + diagnosis rarely made at this stage |
| Intestinal phase - mild infection (<100 worms) | Often asymptomatic or mild epigastric pain + intermittent nausea + moderate diarrhea + mild eosinophilia + may mimic gastroduodenal ulcer or irritable bowel syndrome | Chronicle + adult beetles survive 3 to 5 yearsN. americanus) for 6–8 years oldA. duodenalewithout reinfection + self-limitation impossible without treatment |
| Intestinal phase - moderate infection (100–1,000 worms) | Epigastric abdominal pain + diarrhea + nausea + moderate iron deficiency anemia (Hb 8–11 g/dL) + fatigue + pallor + decreased cognitive and physical performance + in children: growth retardation + learning difficulties | Progressive over months to years without treatment + reversible with antiparasitic treatment + iron supplementation |
| Intestinal phase—severe infection (> 1,000 worms) | Severe iron deficiency anemia (Hb < 7 g/dL) + hypoproteinemia (intestinal albumin loss) + lower limb edema (protein deficiency) + high-output heart failure (severe anemia) + severe growth retardation in children + possible mortality in vulnerable populations (pregnant women + infants + malnourished) | Medical emergency + anemia correction (transfusion if Hb < 7 g/dL) + antiparasitic treatment + intensive protein and iron supplementation |
ℹ️
In Quebec and other Canadian provinces, hookworm infection and necatoriasis should be systematically screened for in all immigrants, refugees, or adopted individuals from endemic tropical or subtropical regions, even in the absence of digestive symptoms—mild to moderate infections are often asymptomatic but lead to progressive iron depletion that can manifest months to years after settling in Canada. A stool parasitological examination with a concentration technique is essential for the initial health assessment of these patients.
Biological diagnosis
- Stool parasitology examination (SPE) with concentration technique: reference method + identification of characteristic hookworm eggs in stool (ellipsoid, thin-shelled eggs + containing 4 to 8 blastomeres at oviposition) + Kato-Katz technique (quantitative slide smear method + allows estimation of parasitic load in eggs per gram of feces) + concentration techniques (Ritchie + flotation) improve sensitivity + three samples on different days recommended to maximize sensitivity because egg excretion is intermittent + minimum delay of 6 to 8 weeks after infection before eggs appear in stool (pre-patent period)
- NFS with differential eosinophilia (often 10–30% of polymorphonuclear cells) + hypochromic microcytic anemia (iron-deficiency anemia due to chronic blood loss) + the severity of the anemia correlates with the parasite burden + possible reactive thrombocytosis
- Martial arts record: Low ferritin + low serum iron + low transferrin saturation coefficient + high TIBC (total iron-binding capacity) → typical profile of iron deficiency due to chronic blood loss + to be corrected in parallel with antiparasitic treatment
- Serology: not available in routine clinical practice + serological tests for detection are not very specific (cross-reactions between nematodes) + not indicated in current practice
- Fecal examination during the prepatent phase (before egg appearance): larval culture (Harada-Mori technique) can sometimes identify early-stage larvae + rarely available outside specialized parasitology centers + in this context — eosinophilia + stay in an endemic area + suggestive clinical presentation → empirical treatment justifiable
- Coproculture and specific identification distinction between Necator americanus and Hookworm (Old World) by egg morphology being difficult in routine testing + identification by feces PCR possible in certain specialized university laboratories + distinction rarely necessary in clinical practice because treatment is identical for both species
Anti-parasitic treatment and anemia correction
| Drug | Dosage | Efficiency and comments |
|---|---|---|
| Albendazole (Albenza®) — first choice | Adult and child > 2 years: 400 mg single oral dose + may be repeated on day 15 if parasitic load is high or infection with A. duodenale (slightly less sensitive at single dose) + take with a meal rich in fat to improve absorption | Response rate of 72–95% for % N. americanus and 95–99 % for A. duodenale single dose + WHO first-line drug + well-tolerated + rare adverse effects: nausea + mild and transient abdominal pain + contraindicated in the first trimester of pregnancy (teratogenic) — to be used after the first trimester if benefits outweigh risks (severe infections in pregnancy threaten mother and fetus) |
| Mebendazole (Vermox®) — alternative | 100 mg twice a day × 3 days by mouth OR 500 mg single dose. Less effective as a single dose than albendazole for hookworms. To be taken with a meal. | The single-dose cure rate is lower than that of albendazole (45–78% % for N. americanus) → 3-day regimen is preferable + similar efficacy to albendazole over 3 days + poorly absorbed orally (mainly local intestinal action) → few systemic effects + safe during pregnancy (reassuring data beyond the 1st trimester) |
| Pyrantel pamoate — alternative to benzimidazoles when they are unavailable | 11 mg/kg (max 1 g) in a single oral dose or 11 mg/kg × 3 days for severe infections | Less effective than albendazole and mebendazole against hookworms + different mechanism (neuromuscular paralysis of the worm) + safe during pregnancy + adverse effects: nausea + abdominal pain + headaches (rare) |
| Ivermectin — Cutaneous larva migrans | 200 µg/kg in a single oral dose (or in two doses on day 1 and day 2) + treatment of choice for cutaneous larva migransBrazilian) with albendazole 400 mg/day x 3 days | Very effective for cutaneous larva migrans + heals in 3-7 days + little to no effect on adult intestinal hookworms + contraindicated in pregnant women and infants < 15 kg |
| Iron supplementation | Ferrous sulfate 150-200 mg of elemental iron per day orally in 2 to 3 doses for 3 to 6 months, to be taken away from meals, in combination with vitamin C to improve absorption. Iron supplementation should accompany antiparasitic treatment and continue until ferritin levels normalize. | The correction of iron deficiency anemia is as important as parasitic eradication. Without iron supplementation, anemia may persist despite the elimination of worms. If anemia is severe (Hb < 7 g/dL) with cardiac or respiratory signs, administer a packed red blood cell transfusion before antiparasitic treatment. |
Prevention and the Quebec Context
- Individual prevention for travelers: wear closed-toe shoes at all times in endemic areas (sand + dirt + grass) + avoid lying directly on wet ground or sand in tropical and subtropical areas + beach umbrellas or towels provide insufficient protection if the ground is contaminated + strict food hygiene (drinking water + cooked food) to prevent oral transmission of'A. duodenale
- Systematic deworming upon arrival in Canada: Canadian refugee health guidelines (Interim Federal Health Program — IFHP) and Canadian Paediatric Society (CPS) recommendations suggest presumptive empiric treatment with albendazole in refugees and immigrants from endemic areas, irrespective of stool parasitology results, due to the low sensitivity of single stool sample testing and the significant health impact of untreated geohelminths.
- Health Assessment of Immigrants and Refugees in Quebec: Stool parasitology examination × 3 consecutive days + CBC + ferritin + serologies (HIV + hepatitis B and C + syphilis + tuberculosis depending on profile) as part of the systematically recommended initial health assessment + the Public Health Regional Directorates (DRSP) of Quebec have specific protocols for the reception and initial health assessment of refugees
- Parasitological cure monitoring Parasitological stool examination for follow-up at 4 weeks after treatment + if still positive, second course of albendazole (single dose) + CBC and ferritin check at 3 months to verify correction of iron deficiency anemia
Situations requiring prompt medical evaluation
A traveler or immigrant returning from a tropical area who presents with severe fatigue + progressive pallor + palpitations or exertional dyspnea (signs of severe anemia) + marked eosinophilia (greater than 15–20% of leukocytes) on blood tests must be evaluated promptly—severe iron-deficiency anemia of parasitic origin may require urgent treatment. Similarly, any child or pregnant woman returning from an endemic region with a hemoglobin level below 7–8 g/dL must be treated as an emergency to determine the need for a transfusion and simultaneously initiate antiparasitic treatment.
A pruritic linear and serpiginous rash appearing after a tropical stay, progressing a few centimeters per day under the skin, is characteristic of cutaneous larva migrans and should lead to prompt medical consultation for starting treatment (ivermectin or albendazole) - not an absolute emergency, but to avoid weeks of pruritic suffering.
For the parasitological assessment of a traveler returning from the tropics, the evaluation of unexplained eosinophilia or iron-deficiency anemia, and the initiation of antiparasitic treatment, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's specialist nurse practitioners (SNPs) provide health check-ups for travelers returning from the tropics and for newly arrived immigrants in Quebec. This includes prescribing stool parasite examinations, complete blood counts (CBCs), and iron level tests, initiating antiparasitic treatment with albendazole, correcting associated iron deficiency anemia, and post-treatment parasite follow-up. Consultations are available at several service locations in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and does not replace the advice of a doctor or a specialist in infectious and tropical diseases. Any traveler or immigrant presenting with unexplained eosinophilia, iron-deficiency anemia, or digestive symptoms after a stay in a tropical area should undergo a complete parasitological examination under medical supervision.
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