Patterns of Transmission and Sources of Infection in Outbreaks of Human Toxoplasmosis

Fernanda Pinto-Ferreira; Eloiza Teles Caldart; Aline Kuhn Sbruzzi Pasquali; Regina Mitsuka-Breganó; Roberta Lemos Freire; Italmar Teodorico Navarro


Emerging Infectious Diseases. 2019;25(12):2177-2182. 

In This Article

Abstract and Introduction


We report on apparent temporal progression of probable sources of infection and transmission routes for global human toxoplasmosis outbreaks as described in published articles. We searched the Scientific Electronic Library Online, Web of Science, PubMed, and Scopus databases for articles on Toxoplasma, toxoplasmosis, and outbreaks. We found that transmission routes for Toxoplasma gondii varied by decade. In the 1960s and 1990s, toxoplasmosis outbreaks mainly occurred through ingestion of cysts in meat and meat derivatives; in the 1980s, through milk contaminated with tachyzoites; in 2000, due to the presence of oocysts in water, sand, and soil; and in 2010, due to oocysts in raw fruits and vegetables. Our study suggests a possible change in the epidemiology of reported toxoplasmosis outbreaks. Because of this change, we suggest that greater attention be paid to the disinfection of vegetables, as well as to the quality of water used for drinking and irrigation.


Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii of the phylum Apicomplexa, an obligate intracellular parasite with a worldwide distribution that infects mammals and birds.[1] Warm-blooded animals serve as intermediate hosts for T. gondii, but felids are its only definitive host and shed oocysts that result in environmental contamination.[2]

Because of high exposure to T. gondii around the world, humans have a high serologic prevalence, which varies between 10.0% and 97.4% in the adult population. However, cases of clinical disease are less frequent.[3] Environmental conditions, cultural and eating habits, and fauna are factors in the variability and prevalence of toxoplasmosis in different geographic areas.[4] Transmission mainly occurs through the ingestion of water, vegetables, or soil contaminated with oocysts (sporozoites) or raw or undercooked meat containing viable tissue cysts (bradyzoites), characterizing this disease as a foodborne zoonosis.[3]

Better understanding of the patterns of occurrence of human toxoplasmosis outbreaks could lead to more effective and targeted prevention and control measures. We report a possible temporal progression of the probable sources of infection and transmission routes described in articles on human toxoplasmosis outbreaks throughout the world from the 1960s through March 2018.