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Chapter 6 : Protozoa from Other Body Sites
Trichomoniasis is the primary nonviral sexually transmitted disease worldwide. Infection with Trichomonas vaginalis has major health consequences for women, including complications in pregnancy, association with cervical cancer, and predisposition to human immunodeficiency virus (HIV) infection. About 20% of women with vaginal trichomoniasis have dysuria, a symptom that may occur before any additional symptoms appear. Toxoplasmosis can be categorized into four groups: (i) disease acquired in immunocompetent patients, (ii) disease acquired or reactivated in immunosuppressed or immunodeficient patients, (iii) congenital disease, and (iv) ocular disease. In genotyping studies, it appears that the type of Toxoplasma gondii strain does not predominantly influence the pathogenesis of toxoplasmosis in immunocompromised patients. Thus, regardless of the strain genotype, there remains the need for specific prophylaxis in these patients infected by T. gondii. Congenital infections result from the transfer of parasites from the mother to the fetus when she acquires a primary infection during pregnancy. The characteristic symptoms of hydrocephalus, cerebral calcifications, and chorioretinitis resulting in mental retardation, epilepsy, and impaired vision represent the most severe form of the disease. Therapy for pregnant patients who acquire the infection and for newborns with Toxoplasma antibody is somewhat controversial. However, prophylactic therapy is often recommended for the newborn until it can be demonstrated that IgM antibody is not present. Since primary infection with T. gondii leads to specific and definitive protection against reinfection, the feasibility of developing a vaccine is now being investigated.
Life cycle of Trichomonas vaginalis.
Trichomonas vaginalis trophozoite. (Illustration by Sharon Belkin.)
InPouch TV diagnostic system for culturing Trichomonas vaginalis. (A) The swab containing a specimen from the patient is being inserted into the liquid medium within the plastic pouch; (B) the top of the plastic pouch is folded over and sealed with the tabs; (C) the pouch is inserted into the plastic holder; (D) the pouch (in the holder) is placed onto the microscope stage for examination (organism motility). (Photographs courtesy of BIOMED Diagnostics.) See also chapter 32.
Trichomonas vaginalis, direct antigen detection strip used for rapid testing (OSOM Trichomonas Rapid Test). (Courtesy of Genzyme Diagnostics, Cambridge, Mass.)
Life cycle of Toxoplasma gondii. The active forms (trophozoites) are also referred to as tachyzoites, while the resting stages within the cysts are called bradyzoites (very slowgrowing trophozoites).
Toxoplasma gondii in the intestine of a cat. (A) Bradyzoites (×1,000); (B) gametocytes (×1,000); (C) oocyst containing two sporocysts with sporozoites (×1,600). (Courtesy of J. K. Frenkel, University of Kansas School of Medicine, Kansas City.)
Forms of Toxoplasma gondii found in humans. (A) Trophozoites (tachyzoites) seen within a cell; (B) cyst containing the bradyzoites (illustration by Sharon Belkin; based on illustration from H. H. Najarian, Textbook of Medical Parasitology, The Williams & Wilkins Co., Baltimore, Md., 1967); (C) tachyzoites recovered from mouse peritoneal fluid.
Forms of Toxoplasma gondii found in humans. (Upper) Tachyzoites seen within bone marrow. (Lower) Bradyzoites seen in human tissue.
Chart for the diagnosis and treatment of neonatal toxoplasmosis. (Adapted from reference 14 .)
Toxoplasmosis: risk management in pregnancy.
Chart for the analysis of conventional antibody tests for Toxoplasma gondii by the IgM technique. Interpretation depends on the type of test used. In the IgM-indirect immunofluorescence assay test, a titer of 1:64 would support a diagnosis of infection acquired 1 to 3 months earlier. In the double-sandwich IgM-ELISA (IgM capture), titers of 1:256 and higher should be expected in the first 4 months of infection. (Adapted from references 10 , 14 , and 43 .)
Characteristics of Trichomonas vaginalis
Virulence factors associated with Trichomonas vaginalis pathogenesis a
Summary of commercially available kits for immunodetection of Trichomonas vaginalis
People at risk for severe toxoplasmosis
Clinical use of immunodiagnostic tests a
General comments on the performance and interpretation of serologic results for the diagnosis of toxoplasmosis a
Guide to interpretation of serologic tests for the diagnosis of toxoplasmosis a
Prevention of infection with Toxoplasma gondii