Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 121 (Suppl. 1) 2026
Perspective
Unseen, untreated: chronic Giardia lamblia infections and the gaps in health systems
1Ministério da Saúde, Secretaria de Vigilância em Saúde e Ambiente, Departamento de Doenças Transmissíveis, Brasília, DF, Brasil
2Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Doenças Parasitárias, Rio de Janeiro, RJ, Brasil
3Universidade do Estado do Rio de Janeiro, Faculdade de Ciências Médicas, Departamento de Medicina Interna, Rio de Janeiro, RJ, Brasil
4Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório Interdisciplinar de Pesquisas Médicas, Rio de Janeiro, RJ, Brasil
5Universidade do Estado do Rio de Janeiro, Faculdade de Ciências Médicas, Departamento de Microbiologia, Imunologia e Parasitologia, Rio de Janeiro, RJ, Brasil
DOI: 10.1590/0074-02760250251
ABSTRACT
Giardiasis is a chronic disease that impairs intestinal absorption and, independently of diarrhoea, contributes to growth and developmental delays, making it an important risk factor for protein-energy malnutrition in children. Its high prevalence is associated with poor sanitation and multiple faecal-oral transmission routes, including person-to-person spread, contamination of water and food, and zoonotic cycles. Giardia lamblia closely interacts with the intestinal epithelium, triggering inflammatory and immune responses. Despite its impact, giardiasis is underdiagnosed, and there is an urgent need for microscopy-independent diagnostic tools suitable for large-scale use. Treatment options include metronidazole or single-dose regimens such as secnidazole and tinidazole, which are more effective but not yet implemented at the community level. Because exposure is continuous, reinfections are frequent, making sustained control particularly challenging. Control efforts could be strengthened through primary health care by expanding access to diagnosis and providing large-scale single-dose treatments, especially in vulnerable communities with poor sanitation. Giardiasis therefore remains an invisible and untreated disease, despite affecting millions and impairing childhood development.
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+ Corresponding author: filipe.anibal.carvalho.costa@gmail.com| 
https://orcid.org/0000-0001-8083-2840
Received 12 September 2025
Accepted 22 January 2026
HOW TO CITE
Calegar DA, Carvalho-Costa FA, Da-Cruz AM, Fantinatti M. Unseen, untreated: chronic Giardia lamblia infections and the gaps in health systems. Mem Inst Oswaldo Cruz. 2026; 121 (Suppl. 1): e250251.
HANDLING EDITOR
Adeilton Alves Brandão | https://orcid.org/0000-0001-5877-607X
