A little-known parasite, Toxoplasma gondii, may be silently infecting around one in three people worldwide, yet scientists warn that its health risks remain widely underestimated. Although the infection it causes, toxoplasmosis, is often mild or symptom-free, it can seriously damage the eyes in some individuals and even lead to permanent vision loss.
Ocular toxoplasmosis is now recognized as the most common infectious cause of inflammation inside the eye worldwide. In a new viewpoint paper, researchers argue that toxoplasmosis meets the World Health Organization’s criteria for classification as a neglected tropical disease (NTD). They believe that official recognition could increase research funding, strengthen prevention efforts, and encourage the development of coordinated international action plans.
Why toxoplasmosis is so widespread
People most commonly become infected by eating raw or undercooked meat containing Toxoplasma gondii tissue cysts or by accidentally ingesting microscopic parasite eggs shed in cat feces. Contaminated soil, unwashed fruits and vegetables, and unsafe drinking water can also serve as important sources of infection in many parts of the world.
Pregnant women represent one of the highest-risk groups because a first-time infection during pregnancy can be transmitted through the placenta to the developing fetus. Congenital toxoplasmosis may result in miscarriage, developmental delays, severe brain abnormalities, hearing impairment, and permanent eye damage that can affect vision throughout life.
A hidden burden in low-income regions
The authors note that toxoplasmosis is particularly common in tropical and subtropical regions, especially where poverty, poor sanitation, and limited access to healthcare increase exposure to the parasite. Some of the highest infection rates have been reported in parts of South America, where more aggressive parasite strains have also been linked to more severe disease.
Globally, an estimated 190,000 infants are born each year with congenital toxoplasmosis. Many require lifelong medical monitoring and treatment, while others experience permanent visual impairment or neurological complications that place a considerable burden on families, healthcare systems, and society.
Why researchers believe it is a neglected tropical disease
According to the World Health Organization, neglected tropical diseases primarily affect disadvantaged populations, occur mainly in tropical or subtropical regions, are preventable or controllable, and receive insufficient research attention and public health investment. The researchers argue that toxoplasmosis fulfills each of these criteria.
Despite its widespread impact, funding for toxoplasmosis research remains far below that of many comparable infectious diseases. There is currently no licensed vaccine for humans, treatment options remain limited, and no standardized global management guidelines exist. The authors argue that these gaps reflect decades of underinvestment despite the disease’s significant health consequences.
How the global burden could be reduced
Researchers emphasize that toxoplasmosis is largely preventable because its routes of transmission are well understood. Thoroughly cooking meat, improving food safety standards, strengthening meat inspection systems, and reducing contamination during food production could substantially lower infection rates.
Improved access to clean drinking water, sanitation, and prenatal healthcare would also help reduce infections, particularly in lower-income countries. Public health campaigns can educate people about simple preventive measures such as washing hands after gardening or handling raw meat, thoroughly washing fruits and vegetables, and safely managing cat litter and animal waste.
A roadmap for global action
The viewpoint paper proposes a roadmap modeled after existing WHO strategies for other neglected tropical diseases. The authors recommend expanding screening programs for congenital toxoplasmosis, improving diagnosis and treatment of ocular disease, investing in better medicines, and increasing access to rehabilitation services for people with vision loss.
They also call for improved training for healthcare professionals, including ophthalmologists, obstetricians, pediatricians, infectious disease specialists, and veterinarians, to strengthen early detection and disease management. Official WHO recognition, they argue, would encourage countries to incorporate toxoplasmosis prevention into maternal healthcare, food safety policies, veterinary surveillance, and primary healthcare services.
Ultimately, the researchers describe toxoplasmosis as a major but largely overlooked global health problem. They argue that coordinated international action, increased investment, and formal recognition as a neglected tropical disease could substantially reduce the burden of preventable blindness, congenital disease, and long-term disability associated with this common parasitic infection.