Which parasites most commonly cause anemia and what are the recommended treatments?
Executive summary
Parasitic infections that most commonly cause anemia are intestinal helminths—particularly hookworms (Necator americanus, Ancylostoma duodenale), whipworm (Trichuris trichiura), and schistosomes (Schistosoma spp.)—with important contributions from Plasmodium (malaria) and, in some settings, heavy infections by Ascaris, Entamoeba, Giardia and other intestinal protozoa; the dominant mechanism is chronic blood loss or iron sequestration leading to iron‑deficiency or inflammation‑mediated anemia [1] [2] [3]. Recommended interventions combine targeted antiparasitic drugs (albendazole/mebendazole/praziquantel for worms and schistosomiasis), antimalarial therapy where applicable, and correction of iron deficiency with supplementation or replacement—strategies whose relative priority depends on local epidemiology and infection intensity [4] [5] [3].
1. Which parasites are the usual suspects: a short roll call
Classic textbooks and reviews identify hookworm species (Necator americanus, Ancylostoma duodenale), Trichuris trichiura and schistosomes as the main parasites causing direct blood loss and iron‑deficiency anemia, while malaria (Plasmodium spp.) and other intestinal parasites (Ascaris lumbricoides, Giardia, Entamoeba histolytica, Hymenolepis nana) also contribute to anemia through diverse mechanisms in different populations [1] [6] [7] [8].
2. How they cause anemia: blood‑sucking, inflammation and malabsorption
Hookworms and Trichuris cause chronic gastrointestinal blood loss—radioisotope studies show heavy hookworm burdens can produce substantial daily blood loss and iron loss per worm—while T. trichiura in heavy infections can bleed enough to produce measurable daily losses; schistosomiasis can promote hypersplenism and red‑cell destruction, and malaria produces hemolysis and inflammation that lowers hemoglobin—all culminating in iron‑deficiency or anemia of inflammation depending on context [1] [6] [3] [9].
3. What the data show: variable contributions by place and age
Epidemiologic studies underline that which parasite matters most depends on geography, age and infection intensity—for example, school and community surveys link hookworm and Ascaris with anemia in Nigerian children [10], while studies in Kenya found malaria, schistosomiasis and helminths variably associated with lower hemoglobin depending on local intensities; meta‑analyses and WHO estimates emphasize that parasite‑related iron loss is a major driver of anemia in low‑income settings but not the sole cause [2] [3] [7].
4. Recommended treatments: antiparasitic drugs plus iron repletion
For soil‑transmitted helminths, broad anthelmintics such as albendazole and mebendazole are standard and effective; clinical reports and program guidance also cite pyrantel as an option and recommend single‑dose or short‑course deworming in endemic settings, often paired with iron supplementation to restore hemoglobin [4] [5]. Schistosomiasis is treated primarily with praziquantel, which achieves cure rates often between about two‑thirds and nine‑tenths after a single dose in many studies [4]. Severe hookworm‑related iron‑deficiency anemia has been successfully reversed with albendazole plus iron therapy in case reports and clinical practice [5].
5. Complementary measures, programmatic nuance and caveats
Public‑health responses emphasize integrated approaches—mass deworming of schoolchildren where indicated, malaria control, nutritional support and improved sanitation—because deworming or antiparasitic treatment alone may not correct anemia when iron deficiency, high fertility, coinfections, or chronic inflammation are also present [3] [2]. Studies repeatedly warn that the attributable fraction of anemia to any single parasite varies widely by setting and that surveillance should guide whether anthelmintic campaigns, praziquantel distribution, malaria therapy, iron supplementation or combinations are prioritized [2] [7].
6. Outliers and rare causes to keep in mind
Clinicians and reports note rare or surprising parasite‑related anemia causes—case reports link ectoparasites such as bedbugs to refractory iron deficiency that resolved after infestation control [11], and African trypanosomes produce a distinct inflammatory anemia—reminders that diagnostic evaluation must remain broad when anemia is unexplained [9] [11].