Source attribution of human toxoplasmosis

Abstract

Chapter 1General introduction PART I: MULTI-HOST TRANSMISSION Chapter 2 Mathematical modelling of Toxoplasma gondii transmission: A systematic review PART II: EPIDEMIOLOGICAL INSIGHTS Chapter 3 Risk factors related to Toxoplasma gondii seroprevalence in indoor-housed Dutch dairy goats Chapter 4 Seroprevalence of Toxoplasma gondii in pregnant women and livestock in the mainland of China: a systematic review and hierarchical meta-analysis PART III: QUANTITATIVE MICROBIAL RISK ASSESSMENTS Chapter 5 The effect of salting on T. gondii viability evaluated and implemented in quantitative risk assessment of meat-borne Toxoplasma gondii infection Chapter 6 Quantitative risk assessment of meat-borne Toxoplasma gondii infection in the mainland of China Chapter 7 Digging into Toxoplasma gondii infections via soil: a quantitative microbial risk assessment approach Chapter 8 General discussion ADDENDUM Summary (in English and Dutch) List of publications Acknowledgements About the author Chapter General introduction GENERAL INTRODUCTION • 13TOXOPLASMOSIS T. gondii infection has a worldwide distribution, and it is generally assumed that one third of the world's human population is infected. The prevalence of infection varies widely between countries and often within a given country . In immunocompetent individuals, most infections are asymptomatic, because the immune system usually keeps the parasites from causing illness. Occasionally, some people may experience flu-like symptoms (e.g., fever, muscle aches, etc.) and swollen lymph nodes for a few weeks or months (Halonen and Weiss, 2013). It was recognised that postnatally acquired T. gondii infection in immune-competent people can cause chorioretinitis (ocular toxoplasmosis) (Gilbert and Stanford, 2000). However, severe consequences are more common in two main risk groups: pregnant women and immuno-compromised individuals .Generally, if women acquire T. gondii infection before pregnancy, the unborn child will be protected, because the mother has developed immunity. However, if primary infection occurs during or just before pregnancy, congenital infection may take place in about 30% of cases . The probability of vertical transmission increases with gestational age, but the consequences for the offspring are more severe in early stages of pregnancy (e.g., major abnormalities in the brain and eye tissues or abortion) (Thiebaut et al., 2007). Infected children who are healthy at birth may develop chorioretinitis later in life.