ORIGINAL PAPER Martine Wallon á GreÂgoire Cozon á Rene Ecochard Patricia Lewin á FrancËois Peyron Serological rebound in congenital toxoplasmosis: long-term follow-up of 133 children Received: 5 April 2001 / Accepted: 9 May 2001 / Published online: 26 July 2001 Ó Springer-Verlag 2001 Abstract Although serological rebound is common in infants with congenital toxoplasmosis, clinical recom- mendations for management, in particular the need for additional treatment, vary. The goals of our retrospec- tive cohort study in 133 consecutive children with con- genital toxoplasmosis were to estimate the incidence and duration of the rebounds, identify predictive factors, assess the long-term risk of eye lesions and the need for treatment. We ®rst estimated the incidence and duration of rebounds and identi®ed predictive factors using an univariate analysis and a Cox model modi®ed to include time-dependent variables. Two cohort studies were then conducted to compare the incidence density of second- ary eye lesions in children who had a rebound versus no rebound, and among children who had a rebound after initial therapy, in those who received an additional course of treatment and in those who did not. Of the 133 children, 93 70%) had at least one rebound during a mean follow-up of 95 months. Of those with one rebound diagnosed after initial treatment, 33 received an additional 3-month course of pyrimethamine/ sulphadoxine and 48 were not treated. Intracranial calci®cation at birth was associated with an increased relative risk RR) of rebound RR=2.601; P=0.03), and treatment with pyrimethamine/sulphadoxine between 2 and 12 months of age with a decreased risk RR=0.3; P=0.0845), whereas age of pregnancy at maternal infection, type of treatment during pregnancy and sex were not found to be predictive factors. There was no dierence in incidence densities of secondary eye lesions in children without rebound 7/3,367 child- months) compared to those with at least one rebound 22/9,609 child-months) RR=1.10; 95% CI: 0.47±2.58), and, among the 81 children who had one rebound diagnosed after initial treatment, in those who received an additional course of treatment and in those who did not RR=0.72; 95% CI: 0.30±1.72). Conclusion: sero- logical rebound is common in children with congenital toxoplasmosis but, due to the risk and constraints, an additional course of treatment and more ophthalmo- logical surveillance than currently practiced do not seem warranted. Keywords Congenital toxoplasmosis á IgG á Serological rebound á Therapy á Toxoplasma gondii Abbreviations CI con®dence interval á RR relative risk Introduction Congenital toxoplasmosis results from transplacental infection of Toxoplasma gondii from an infected mother to the fetus and can lead to severe lesions. Its course is unpredictable, regardless of whether the condition is diagnosed in utero, at birth, or later in childhood with the onset of clinical signs. Treatment and clinical mon- itoring are required to reduce the severity of existing lesions and prevent the late development of new clinical manifestations, the most common of which are ocular lesions [11]. In congenitally-infected children, a sudden rise in antibodies, termed serological rebound, is a well- known phenomenon and may occur irrespective of the clinical status of the infected child and the type of treatment regimen prescribed. Although several studies of serological rebound have been reported, comparison of ®ndings is dicult due to wide variations in the Eur J Pediatr 2001) 160: 534±540 DOI 10.1007/s004310100805 M. Wallon &) á F. Peyron Service de Parasitologie, HoÃpital de la Croix-Rousse, 103 grande rue de la Croix-Rousse, 69004 Lyon, France E-mail:wallon@wanadoo.fr Tel.:+33-4-72071872 Fax:+33-4-72071873 G. Cozon Laboratoire d'Immunologie, HoÃpital de la Croix-Rousse, Lyon, France R. Ecochard DeÂpartement d'Information MeÂdicale des Hospices Civils de Lyon, Lyon, France P. Lewin Laboratoire Pasteur Cerba, Cergy Pontoise, France