Toxoid - Trachoma

toxoid

(tok′soyd″) [tox(in) + -oid] A toxin chemically modified to retain its antigenicity but no longer poisonous. SYN: anatoxin.

 alum-precipitated t. Toxoid of diphtheria or tetanus precipitated with alum.

 diphtheria t. Diphtheria toxin altered so that it cannot cause disease but is still able to stimulate the production of antibodies for active immunization. It is used in diphtheria-pertussis-tetanus vaccine (DTaP).

 tetanus t. Tetanus toxin modified so that its toxicity is greatly reduced but retaining its capacity to promote active immunity. SEE: toxin.

toxolecithin

(tŏks″ō-lĕs′ĭ-thĭn) [″ + lekithos, egg yolk] A compound of lecithin with a toxin such as certain snake venoms.

toxopeptone

(tŏks″ō-pĕp′tōn) [″ + pepton, digesting] A protein derivative produced by action of a toxin on peptones.

Toxoplasma

(tŏks″ō-plăs′mă) A genus of protozoa in the sporozoa group.

 T. gondii The causative agent of toxoplasmosis.

toxoplasmin

(tŏk″sō-plăs′mĭn) An antigen obtained from mouse peritoneal fluid infected with Toxoplasma gondii.

toxoplasmosis

(tok-sŏ-plaz″-mō′sĭs) [Toxoplasma + -osis] Infection with the protozoan Toxoplasma gondii. It usually is a recurrence of a mild infection in people with normal immune systems; approx. 30% of the U.S. population have antibodies indicating they have been infected. AIDS patients or those who are receiving immunosuppressive therapy after an organ transplant are esp. susceptible: for them reactivation of dormant organisms may be fatal. Approx. 25% of women infected for the first time during pregnancy pass the infection to the developing fetus.

ETIOLOGY/TRANSMISSION: T. gondii is carried by many birds and mammals and is commonly transmitted to humans by inadequate handwashing after handling cat feces or by eating incompletely cooked pork or lamb. Once inside the intestines, the organism may spread via the blood to other organs. It is destroyed by T lymphocytes.

In infected fetuses, toxoplasmosis damages the heart, brain, and lungs. It also causes eye infection (chorioretinitis), which may produce blindness. In AIDS patients, toxoplasmosis is the most common cause of encephalitis; systemic disease also may occur. In immunosuppressed patients, the infection causes reactivation of latent infection in the transplanted organ.

DIAGNOSIS: Toxoplasmosis is diagnosed by clinical presentation, brain biopsy, brain scans, and response to treatment.

SYMPTOMS: In healthy people, primary infection may be indicated only by mild lymphadenopathy. AIDS patients with neurological involvement usually show confusion, weakness, focal neurological deficits, seizures, and decreased levels of consciousness; fever may be present.

TREATMENT: A combination of pyrimethamine, sulfadiazine, and leucovorin (folinic acid) is administered until 2 weeks after symptoms disappear; the latter helps prevent bone marrow ...