impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 37-43, 2008
Congenital Toxoplasmosis: The State of the Art
W. Buffolano
Aggregate Professor in Clinical Paediatrics, Heading The Regional Register and The Special Unit for Perinatal Infection,
Federico II University, Naples Medical School- Italy
Abstract. A century after the first description the best preventative strategy against CT is still matter of
debate. Over Europe, where prenatal and newborn screening are overspread, effectiveness/ cost ratio
remains undemonstrated.
Key words: congenital toxoplasmosis, prevention strategies, health promotion, risl factors, screening,
treatment
The Toxoplasmosis in Humans
Infection with the protozoan parasite Toxoplasma
gondii occurs worldwide. Cats and other felids are the
only definitive hosts in which sexual reproduction
occurs to produce infective oocysts. Warm- blooded
animals, including humans, are intermediate hosts that
harbour tissue cysts in their bodies. Active infection is
usually acquired by oral route and presumably results
in lifelong parasite colonisation and specific antibodies
production. Consequently, serological IgG testing
offers the opportunity to measure specific individual
protection and public health impact of toxoplasmosis
(cross-sectional study). In general, seroprevalence displays
highest in the southern America and Europe, in
central America and sub-Saharian Africa, lowest in the
far East. In the last decades a negative trend in infection
rate has been demonstrated in many European
countries and U.S.A. and attributed to improvement in
general lifestyle hygiene and in food chain storage and
transport, thus potentially biasing health impact evaluation
(Forsgren M et al., 1991).
As, with few exceptions, acute phase of toxoplasmosis
in otherwise healthy humans occurs in a self- limited
subclinical or mild form it can only be detected by serological
screening for T. gondii antibodies. The most
common clinical picture consists of isolated cervical or
occipital lymphadenopathy staying for 4 to 6 weeks.
Chorioretinitis leading to permanent visual loss in nearly
25% of patients can complicate congenital and postnatally
acquired disease as a result of acute infection or
reactivation, with differences in prevalence according
to different settings (Jones JL et al., 2006; McLeod RM
et al., 2006). In immunocompromised host complications
such as myocarditis, polymiositis, hepatitis, or
encephalitis may arise. Primary toxoplasmosis on gestation
can be transmitted through the placenta to overall
30% of the foetus with serious permanent, even fatal
consequences, such as death in utero, hydrocephalus,
microcephalus, chorioretinitis, and intracranial calcifi-
Correspondence: Wilma Buffolano
Tel +39 081 7462914, Fax +39 081 7463004;
e-mail: wilma.buffolano@unina.it
cations. Non specific symptoms mimicking congenital
toxoplasmosis (CT) with other pathogens, such as
hepato-splenomegaly, purpura, jaundice and intra-uterine
growth retardation, have been described (McAuley
J et al., 1994). Furthermore, over Europe preterm
birth, low birth weight and small for gestational age
were not confirmed significantly different in infected
babies compared with uninfected, and severe generalised
onset was found uncommon in a screening care
setting (Freeman K et al., 2005; Gras L et al., 2005).
Which Prevention Strategy
Starting eighties there has been pressure for specific
policy against CT (Mc Cabe R et al., 1988), and different
strategies have been adopted. The first approach,
namely prenatal screening (i.e. monthly or 3 monthly
testing of pregnant women without detectable antibodies
at their first prenatal testing), was launched in
Austria and France in the 1970s, and in Italy in the
nineties. The second approach, namely newborn
screening, was included in the New England Neonatal
Screening Program, since 1988 and conducted for a
limited period of time in Denmark, Sweden, Poland
and Brazil. On demand, prenatal testing is over-spread
in EU countries and was advocated in Finland and
Norway. Effectiveness/cost ratio of prenatal screening
is considered acceptable in medium-high prevalence
setting (≥40% seroprevalence in childbearing age
women), while in low prevalence setting newborn
screening could be considered (Ades AE et al., 2005).
Prenatal screening is aimed to decrease incidence and
onset severity of CT by early identification and treatment
of infected pregnant women. Early identification
of unprotected mother may allows for health education
on how to avoid primary infection with T. gondii on gestation.
The main drugs used for treatment of toxoplasmosis
(spiramycine, pyrimethamine-sulphonamide combination)
either on gestation, either congenital, and
either symptomatic in otherwise healthy or immunocompromised
patients were included in medical practice
decades ago. None of these can eradicate T. gondii
tissue cysts; as a consequence, many immunocompromised
or congenitally infected patients still remain at
risk of repeated ocular disease reactivation.