Walsh & Hoyt: Toxoplasmosis: Clinical Manifestations

The symptoms and signs of patients with toxoplasmosis depend on three factors: whether the condition is congenital or acquired; whether the condition occurs in an immunocompetent or an immunodeficient patient; and whether the condition is limited to the eye or is systemic. Thus, most authors recognize four groups of patients: (a) immunocompetent patients with acquired infection; (b) immunodeficient patients with acquired or reactivated infection; (c) patients with congenital infection; and (d) patients with ocular toxoplasmosis

Walsh & Hoyt: Toxoplasmosis: Treatment and Prognosis

The lack of controlled clinical trials and the variable course of toxoplasmosis in both immunocompetent and immunodeficient persons have resulted in uncertainty and controversy regarding specific indications for treatment, appropriate drugs, and even the duration of treatment of this disease. Although the role of treatment is clearer in CNS toxoplasmosis and in ocular toxoplasmosis in immunosuppressed patients, there is no clear evidence of the role of treatment in ocular toxoplasmosis in immunocompetent patients

Walsh & Hoyt: Toxoplasmosis

Toxoplasma is an obligate intracellular organism that is a member of the class of protozoa called Sporozoa. It thus is a member of the same class as Babesia and Plasmodium species (discussed earlier). There is only one species-Toxoplasma gondii-and all strains appear antigenically similar. The name Toxoplasma gondii is derived from the crescent shape of the trophozoite form of the organism (from the Greek word toxon, meaning ‘‘bow'') and from the North American rodent ‘‘gondi,'' the animal in which it was first described (13,14,624)

Walsh & Hoyt: Microsporidia

The phylum Microsporidia consists of about 150 genera and more than 1200 species. Organisms belonging to this phylum are called microsporidia. Microsporidia are obligate intracellular, spore-forming protozoa. They are ubiquitous in nature, but they were not recognized as human pathogens until the late 1980s

Walsh & Hoyt: Toxoplasmosis: Epidemiology

Infection by Toxoplasma gondii is called toxoplasmosis. This condition is a worldwide zoonosis. The organism infects herbivorous, omnivorous, and carnivorous animals, including all orders of mammals. Serologic surveys indicate that 22.5% of healthy adults in the United States have been infected with Toxoplasma. In some parts of Brazil, seroprevalence approaches 100%

Walsh & Hoyt: Pathology

The neuropathologic changes of babesiosis are poorly documented and come from observations primarily made in animals. Capillaries in the brain, retina, and ciliary body show swollen endothelial cells and are filled with erythrocytes parasitized by the organisms

Walsh & Hoyt: Plasmodium Species (Malaria)

The genus Plasmodium contains several species of obligate intracellular parasites within the class of protozoa called Sporozoa, a class that also contains two other genera of protozoa that are pathogenic for humans: Babesia and Toxoplasma. Although a large number of Plasmodium species naturally infect a variety of animals, including monkeys, rodents, birds, and reptiles, only four species infect humans: P. falciparum, P. vivax, P. malariae, and P. ovale. Each species has certain morphologic characteristics by which the parasite can be identified, and each has biologic and pathogenic features of clinical importance

Walsh & Hoyt: Diagnosis

Malaria usually is suspected when the typical symptoms and signs occur in the appropriate epidemiologic setting. Laboratory studies consistent with the diagnosis include a normochromic normocytic hemolytic anemia, leukopenia, and thrombocytopenia. There is no peripheral eosinophilia. The urine of affected patients frequently contains small amounts of protein, probably related to the effects of fever. Electrolyte balance may be disturbed by several factors, including dehydration, vomiting, tissue hypoxia, tachypnea, renal failure, and homeostatic responses to decreased effective plasma volume. The serum may contain increased concentrations of transaminases and bilirubin, consistent with abnormal liver function

Walsh & Hoyt: Clinical Manifestations

The clinical manifestations of babesiosis differ markedly between European and North American cases. Cases reported in Europe generally occur in splenectomized patients and present as a fulminant, febrile, hemolytic, and often fatal disease that initially may be mistaken for malaria. In contrast, most infections with Babesia species in the United States occur in otherwise healthy persons and produce either subclinical infection or a mild illness characterized by fever, hemolysis, and hemoglobinuria. Severe cases in the United States usually occur either in asplenic patients or in patients who are immunocompromised by age, drugs, or disease such as AIDS, but even severe cases are rarely fatal, as they are in Europe. In patients with Lyme disease and simultaneous babesiosis that is not fatal, the illness tends to be both more prolonged and more severe than with babesiosis alone. Most patients who develop babesiosis are adults, but children may also be infected