impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 45-50, 2008
Clinical and Diagnostic Management of Toxoplasmosis in the
Immunocompromised Patient
C. Contini
Section of Infectious Diseases, Department of Clinical and Experimental Medicine, University of Ferrara, via Fossato di
Mortara 23, 44100 Ferrara, Italy
Abstract. With the advent of the highly active antiretroviral therapy (HAART), the natural course of HIV infection
has markedly changed and opportunistic infections including toxoplasmosis have declined and modified
in presentation, outcome and incidence. However, TE is a major cause of morbidity and mortality especially
in resource-poor settings but also a common neurological complication in some countries despite the
availability of HAART and effective prophylaxis. In most cases toxoplasmosis occurs in brain and toxoplasmic
encephalitis (TE) is the most common presentation of toxoplasmosis in immunocompromised patients
with or without AIDS. The need of a definitive diagnosis is substantial because other brain diseases could
share similar findings. Rapid and specific diagnosis is thus crucial as early treatment may improve the clinical
outcome. Classical serological diagnosis is often inconclusive as immunodeficient individuals fail to produce
significant titres of specific antibodies. Polymerase chain reaction (PCR) has a high diagnostic value
in the acute disease, but like many ‘in-house’ PCR assays, suffers from lack of standardization and variable
performance according to the laboratory. Molecular diagnosis of toxoplasmosis can be improved by performing
real-time PCR protocols. This article summarises the clinical manifestations, diagnostic procedures
and management strategies for this condition.
Key words: toxoplasmosis, immunocompromised patients, AIDS, transplantation
Introduction and background
Toxoplasma gondii infects up to 80% of some
European populations and 20% of people in the United
States (Hall S et al., 2001). Normally, infection is generally
benign as immune system keeps the parasite in
check and parasitaemia is self-limited resulting in an
asymptomatic clinical form in most cases. In developing
foetus and in immunocompromised individuals
especially those with deficient cellular immunity, it can
cause significant morbidity and mortality.
The first reports of T. gondii in immunocompromised
patients involved persons with leukaemia and myeloma
and cerebral toxoplasmosis was recognized early as a
particular problem. With the advancements made in
transplantation of different organs, especially of the
heart and bone marrow (BMT), allogeneic haematopoietic
stem cell transplants patients (HSCT) and, less
often, after kidney transplants, toxoplasmosis in these
subjects has become a well-recognized and serious clinical
problem (Slavin MA et al., 1994, Martino R et al.,
2005). The frequency of parasitic infections as complications
of organ transplantation is unknown; however,
these are much less prevalent than bacterial and viral
infections. Only 5% of human pathogenic parasites
Correspondence: Prof. Carlo Contini
MD Section of Infectious Diseases, Department of Clinical and
Experimental Medicine, University of Ferrara, via Fossato di
Mortara, 23, 44100 Ferrara, Italy.
Tel: +39 532 455490; Fax: +39 532 455495
e-mail: cnc@unife.it
have been reported to cause significant illness in heart
transplant recipients (Montoya JG et al., 2001).
With the advent of human immunodeficiency virus
(HIV) pandemic, toxoplasmic encephalitis (TE) has
become one of the most common cerebral opportunistic
infection complicating the course of AIDS, often fatal,
if untreated (Luft JB et al., 1993; Richards F et al., 1995
) and the most frequent cause of focal intracerebral
lesions in this group. TE is also the most common presentation
of toxoplasmosis in immunocompromised
patients other than AIDS (Israelski DM et al., 1993).
Although the epidemiology of the central nervous system
(CNS) opportunistic diseases has changed after the
introduction of the highly active antiretroviral therapy
(HAART), TE is still a common neurological complication
in AIDS patients from Brazil, despite the availability
of HAART and effective prophylaxis (Vidal JE et al.,
2005).
The peak incidence of TE is highest among patients
between 25 and 35 years old, whereas the incidence is
directly proportional to the prevalence of latent
Toxoplasma infection which increases with age
(Holliman RE et al., 1990). Differences in genotypes of
T. gondii specific strain, races and ethnicities and the
mode of transmission seem also to account in influencing
the occurrence of TE (Sarciron ME et al., 2000;
Khan A et al., 2005).
Cellular immunity is one of the main mechanisms of
defence in the control of toxoplasmosis. The variety of
immune system defects found in individuals with
AIDS, such as CD4 + T lymphocyte deficiency, reduced
activity of cytotoxic T and NK cells, and the low production
of immunoregulatory lymphokines such as