Introduction
Intestinal parasites are a global health problem. They affect humans, domestic animals, and wildlife, causing disease, poor productivity, and in some cases, life-threatening illness. The intestinal parasites of greatest concern include Ascaris, Giardia, Hookworms, Toxocara, and Echinococcus species.
These parasites spread through contaminated food, water, and soil, and their effects reach across human health, veterinary medicine, and wildlife conservation.
But how do intestinal parasites spread, and what can be done to prevent their harmful impacts?
Why Intestinal Parasites Matter
Parasitic infections can cause both mild and severe illness. In humans, symptoms range from diarrhea and abdominal pain to malnutrition, anemia, and even organ damage [1]. In children, chronic infections can impair growth and cognitive development.
Domestic animals also suffer reduced health and productivity, while wildlife can act as reservoirs of infection. Because many intestinal parasites are zoonotic, they pose risks across species.
Key Parasites and Their Transmission
Several parasites have particularly significant impacts:
- Ascaris lumbricoides (Roundworm): Affects humans and pigs. Eggs passed in feces contaminate soil, where they become infectious and people ingest them in food or water [1].
- Giardia duodenalis (Giardia): A protozoan parasite found in humans, pets, and wildlife. Infection occurs after drinking contaminated water. It is a leading cause of diarrheal illness worldwide [2].
- Ancylostoma spp. (Hookworms): Infect humans and dogs. Infective larvae penetrate skin or enter through ingestion, causing anemia and weakness.
- Toxocara spp. (Roundworms of dogs and cats): Humans ingest eggs from contaminated soil or food. Larvae migrate to organs, sometimes causing serious damage to the eyes, lungs, or brain.
- Echinococcus spp. (Tapeworms): Dogs and wild canids carry adult worms. Humans become accidental hosts after ingesting eggs, leading to cystic disease in vital organs [3].
These parasites highlight how closely human, animal, and environmental health are connected.
Diagnosis and Treatment
Detecting intestinal parasites depends on the species:
- Stool tests: Identify eggs, cysts, or larvae.
- Blood tests: Detect antibodies for tissue-invasive parasites such as Echinococcus.
- Molecular methods: PCR is increasingly used for precise detection of parasites like Giardia.
- Imaging: Ultrasound or CT scans detect cysts caused by Echinococcus.
Treatment varies by parasite. Albendazole, mebendazole, and ivermectin treat helminths, while metronidazole is used for protozoa like Giardia [4]. In severe cases, supportive care such as hydration and iron supplements may be necessary.
Epidemiology and Global Burden
Intestinal parasites are most common in tropical and subtropical regions with poor sanitation. Soil-transmitted helminths alone affect over a billion people worldwide. Pets often harbor Toxocara and hookworms, while wildlife reservoirs such as beavers (Giardia) and foxes (Echinococcus) complicate control efforts.
Climate, poverty, and inadequate health services allow these infections to persist, creating a cycle of illness and reduced productivity.
Prevention and Control
Effective prevention requires a multi-layered approach:
- Improved sanitation: Safe drinking water and proper sewage systems reduce spread.
- Regular deworming: Treating both humans and animals lowers parasite load.
- Health education: Communities benefit from awareness of hygiene and safe food handling.
- Environmental management: Controlling dog populations and limiting livestock exposure to infected dogs helps prevent Echinococcus.
Emerging research includes vaccines for parasites such as Toxocara and Echinococcus, offering new hope for long-term control.
A One Health Perspective
Intestinal parasites exemplify why a One Health approach is essential. Human, animal, and environmental health are deeply interconnected. Poor sanitation, untreated pets, and wildlife reservoirs all contribute to infections. Tackling these parasites requires cooperation between doctors, veterinarians, and conservationists [3].
By addressing all sides of the problem, societies can reduce the burden of parasites and protect both people and animals.
Conclusion
Intestinal parasites remain a major public health challenge. They cause illness in humans, reduce animal health, and persist in wildlife. However, they are preventable. By improving sanitation, promoting regular deworming, strengthening food and water safety, and adopting a One Health perspective, the burden of intestinal parasites can be reduced.
Protecting against these parasites is not just about treating infections—it is about creating healthier communities, safer environments, and stronger connections between human and animal health.
References
- Hotez, P.J., Brindley, P.J., Bethony, J.M., King, C.H., Pearce, E.J. and Jacobson, J. (2008) ‘Helminth infections: the great neglected tropical diseases’, Journal of Clinical Investigation, 118(4), pp. 1311–1321. doi:10.1172/JCI34261
- Centers for Disease Control and Prevention (CDC) (2024) About Giardia Infection. Giardia. Available at: https://www.cdc.gov/giardia/about/index.html (Accessed: 31 August 2025).
- Eckert, J. and Deplazes, P. (2004) ‘Biological, epidemiological, and clinical aspects of echinococcosis’, Clinical Microbiology Reviews, 17(1), pp. 107–135. doi:10.1128/CMR.17.1.107-135.2004.
- Centers for Disease Control and Prevention (CDC) (2025) Soil-transmitted helminths – Clinical care. Available at: https://www.cdc.gov/sth/hcp/clinical-care/index.html (Accessed: 31 August 2025).
