Introduction

The acquired immunodeficiency syndrome (AIDS), first described in adult male homosexuals in the USA in 1981, is one manifestation of infection with the human immunodeficiency virus (HIV). HIV infection produces a wide range of clinical manifestations from asymptomatic infection to marked immunodeficiency. The four recognized routes of virus transmission are sexual contact with an HIV-infected individual; receipt of HIV-infected blood or blood products; parenteral exposure to HIV-contaminated equipment, and vertical transmission from an HIV-infected pregnant woman. The HIV pandemic has had a formidable impact on global maternal and child health and survival, with important public health consequences. As of December 2000, the World Health Organization (WHO) estimated that there are over 16 million women and 1.4 million children with HIV/AIDS worldwide. In the USA, over 400,000 cases of AIDS had been reported by June 2000. HIV-1 infection has become one of the leading causes of morbidity and mortality in children worldwide. In the USA, HIV infection was the seventh leading cause of death in children 1–4 years of age in 1996. The most common AIDS-defining conditions in children are listed in Table 18.1.

Descriptions of cases of AIDS in children began in 1982; almost 9000 cases of AIDS in individuals under 13 years of age had been reported in the USA by June 2000. Children under 13 years of age account for 1.2% of the total AIDS cases reported in the USA.

Introduction

Maternal infections, contracted during pregnancy, may be without fetal consequence or they may have serious adverse effects on the fetus. These adverse effects may include fetal death, stillbirth, intrauterine growth retardation, or congenital infection. Congenitally infected neonates may be symptomatic or asymptomatic at birth. Those who are symptomatic at birth generally have significant long-term sequelae. Those who are asymptomatic at birth may never manifest evidence of damage or they may develop clinically evident sequelae later in life. The overwhelming morbidity attributable to congenital infections is borne by this latter group.

The following chapter will discuss the neurologic consequences of congenital infections. The specific infectious agents that will be discussed are often referred to as the TORCH agents; T represents the parasite Toxoplasma gondii; O represents other agents such as varicella-zoster virus (VZV), human immunodeficiency virus (HIV), and Treponema pallidum (syphilis); R represents rubella virus; C represents cytomegalovirus (CMV); and H represents herpes simplex virus (HSV). With the exception of HSV, the major clinical impact of these agents results from exposure in utero. Morbidity and mortality attributable to neonatal HSV infection usually result from infection contracted at delivery.

Toxoplasmosis

The etiologic agent of toxoplasmosis, Toxoplasma gondii, was first demonstrated in the brain of a newborn infant with encephalomyelitis in 1939. The incidence of congenital toxoplasmosis in the USA is estimated to range from 1:1000 to 1:10,000 live births. Among immunocompetent women, transmission to the fetus is limited almost solely to those who contract primary infection during gestation.