Pyrimethamine: One of the FOLIC ACID ANTAGONISTS that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis.Sulfadoxine: A long acting sulfonamide that is used, usually in combination with other drugs, for respiratory, urinary tract, and malarial infections.Sulfadiazine: One of the short-acting SULFONAMIDES used in combination with PYRIMETHAMINE to treat toxoplasmosis in patients with acquired immunodeficiency syndrome and in newborns with congenital infections.Antimalarials: Agents used in the treatment of malaria. They are usually classified on the basis of their action against plasmodia at different stages in their life cycle in the human. (From AMA, Drug Evaluations Annual, 1992, p1585)Sulfanilamides: Compounds based on 4-aminobenzenesulfonamide. The '-anil-' part of the name refers to aniline.Dapsone: A sulfone active against a wide range of bacteria but mainly employed for its actions against MYCOBACTERIUM LEPRAE. Its mechanism of action is probably similar to that of the SULFONAMIDES which involves inhibition of folic acid synthesis in susceptible organisms. It is also used with PYRIMETHAMINE in the treatment of malaria. (From Martindale, The Extra Pharmacopoeia, 30th ed, p157-8)Tetrahydrofolate Dehydrogenase: An enzyme of the oxidoreductase class that catalyzes the reaction 7,8-dihyrofolate and NADPH to yield 5,6,7,8-tetrahydrofolate and NADPH+, producing reduced folate for amino acid metabolism, purine ring synthesis, and the formation of deoxythymidine monophosphate. Methotrexate and other folic acid antagonists used as chemotherapeutic drugs act by inhibiting this enzyme. (Dorland, 27th ed) EC 126.96.36.199.Folic Acid Antagonists: Inhibitors of the enzyme, dihydrofolate reductase (TETRAHYDROFOLATE DEHYDROGENASE), which converts dihydrofolate (FH2) to tetrahydrofolate (FH4). They are frequently used in cancer chemotherapy. (From AMA, Drug Evaluations Annual, 1994, p2033)Proguanil: A biguanide compound which metabolizes in the body to form cycloguanil, an anti-malaria agent.Drug Combinations: Single preparations containing two or more active agents, for the purpose of their concurrent administration as a fixed dose mixture.Drug Resistance: Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.Plasmodium falciparum: A species of protozoa that is the causal agent of falciparum malaria (MALARIA, FALCIPARUM). It is most prevalent in the tropics and subtropics.Chloroquine: The prototypical antimalarial agent with a mechanism that is not well understood. It has also been used to treat rheumatoid arthritis, systemic lupus erythematosus, and in the systemic therapy of amebic liver abscesses.Dihydropteroate Synthase: An enzyme that catalyzes the formation of dihydropteroate from p-aminobenzoic acid and dihydropteridine-hydroxymethyl-pyrophosphate. EC 188.8.131.52.Malaria, Falciparum: Malaria caused by PLASMODIUM FALCIPARUM. This is the severest form of malaria and is associated with the highest levels of parasites in the blood. This disease is characterized by irregularly recurring febrile paroxysms that in extreme cases occur with acute cerebral, renal, or gastrointestinal manifestations.Parasitic Sensitivity Tests: Tests that demonstrate the relative effectiveness of chemotherapeutic agents against specific parasites.Toxoplasmosis, Cerebral: Infections of the BRAIN caused by the protozoan TOXOPLASMA gondii that primarily arise in individuals with IMMUNOLOGIC DEFICIENCY SYNDROMES (see also AIDS-RELATED OPPORTUNISTIC INFECTIONS). The infection may involve the brain diffusely or form discrete abscesses. Clinical manifestations include SEIZURES, altered mentation, headache, focal neurologic deficits, and INTRACRANIAL HYPERTENSION. (From Joynt, Clinical Neurology, 1998, Ch27, pp41-3)Sulfalene: Long-acting plasma-bound sulfonamide used for respiratory and urinary tract infections and also for malaria.Atovaquone: A hydroxynaphthoquinone that has antimicrobial activity and is being used in antimalarial protocols.Antiprotozoal Agents: Substances that are destructive to protozoans.Toxoplasma: A genus of protozoa parasitic to birds and mammals. T. gondii is one of the most common infectious pathogenic animal parasites of man.Malaria: A protozoan disease caused in humans by four species of the PLASMODIUM genus: PLASMODIUM FALCIPARUM; PLASMODIUM VIVAX; PLASMODIUM OVALE; and PLASMODIUM MALARIAE; and transmitted by the bite of an infected female mosquito of the genus ANOPHELES. Malaria is endemic in parts of Asia, Africa, Central and South America, Oceania, and certain Caribbean islands. It is characterized by extreme exhaustion associated with paroxysms of high FEVER; SWEATING; shaking CHILLS; and ANEMIA. Malaria in ANIMALS is caused by other species of plasmodia.Triazines: Heterocyclic rings containing three nitrogen atoms, commonly in 1,2,4 or 1,3,5 or 2,4,6 formats. Some are used as HERBICIDES.Gangliosidoses, GM2: A group of recessively inherited diseases characterized by the intralysosomal accumulation of G(M2) GANGLIOSIDE in the neuronal cells. Subtypes include mutations of enzymes in the BETA-N-ACETYLHEXOSAMINIDASES system or G(M2) ACTIVATOR PROTEIN leading to disruption of normal degradation of GANGLIOSIDES, a subclass of ACIDIC GLYCOSPHINGOLIPIDS.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Mefloquine: A phospholipid-interacting antimalarial drug (ANTIMALARIALS). It is very effective against PLASMODIUM FALCIPARUM with very few side effects.Artemisinins: A group of SESQUITERPENES and their analogs that contain a peroxide group (PEROXIDES) within an oxepin ring (OXEPINS).Congo: A republic in central Africa lying between GABON and DEMOCRATIC REPUBLIC OF THE CONGO and south of Cameroon. Its capital is Brazzaville.SesquiterpenesToxoplasmosis, Animal: Acquired infection of non-human animals by organisms of the genus TOXOPLASMA.Drug Therapy, Combination: Therapy with two or more separate preparations given for a combined effect.Sulfamerazine: A sulfanilamide that is used as an antibacterial agent.Naphthoquinones: Naphthalene rings which contain two ketone moieties in any position. They can be substituted in any position except at the ketone groups.Toxoplasmosis: The acquired form of infection by Toxoplasma gondii in animals and man.Coccidiostats: Agents useful in the treatment or prevention of COCCIDIOSIS in man or animals.Cameroon: A republic in central Africa lying east of CHAD and the CENTRAL AFRICAN REPUBLIC and west of NIGERIA. The capital is Yaounde.Chorioretinitis: Inflammation of the choroid in which the sensory retina becomes edematous and opaque. The inflammatory cells and exudate may burst through the sensory retina to cloud the vitreous body.Genes, Protozoan: The functional hereditary units of protozoa.Inhibitory Concentration 50: The concentration of a compound needed to reduce population growth of organisms, including eukaryotic cells, by 50% in vitro. Though often expressed to denote in vitro antibacterial activity, it is also used as a benchmark for cytotoxicity to eukaryotic cells in culture.Trimethoprim: A pyrimidine inhibitor of dihydrofolate reductase, it is an antibacterial related to PYRIMETHAMINE. It is potentiated by SULFONAMIDES and the TRIMETHOPRIM, SULFAMETHOXAZOLE DRUG COMBINATION is the form most often used. It is sometimes used alone as an antimalarial. TRIMETHOPRIM RESISTANCE has been reported.Toxoplasmosis, Congenital: Prenatal protozoal infection with TOXOPLASMA gondii which is associated with injury to the developing fetal nervous system. The severity of this condition is related to the stage of pregnancy during which the infection occurs; first trimester infections are associated with a greater degree of neurologic dysfunction. Clinical features include HYDROCEPHALUS; MICROCEPHALY; deafness; cerebral calcifications; SEIZURES; and psychomotor retardation. Signs of a systemic infection may also be present at birth, including fever, rash, and hepatosplenomegaly. (From Adams et al., Principles of Neurology, 6th ed, p735)Pregnancy Complications, Parasitic: The co-occurrence of pregnancy and parasitic diseases. The parasitic infection may precede or follow FERTILIZATION.Amodiaquine: A 4-aminoquinoline compound with anti-inflammatory properties.Plasmodium vivax: A protozoan parasite that causes vivax malaria (MALARIA, VIVAX). This species is found almost everywhere malaria is endemic and is the only one that has a range extending into the temperate regions.Trimetrexate: A nonclassical folic acid inhibitor through its inhibition of the enzyme dihydrofolate reductase. It is being tested for efficacy as an antineoplastic agent and as an antiparasitic agent against PNEUMOCYSTIS PNEUMONIA in AIDS patients. Myelosuppression is its dose-limiting toxic effect.Quinine: An alkaloid derived from the bark of the cinchona tree. It is used as an antimalarial drug, and is the active ingredient in extracts of the cinchona that have been used for that purpose since before 1633. Quinine is also a mild antipyretic and analgesic and has been used in common cold preparations for that purpose. It was used commonly and as a bitter and flavoring agent, and is still useful for the treatment of babesiosis. Quinine is also useful in some muscular disorders, especially nocturnal leg cramps and myotonia congenita, because of its direct effects on muscle membrane and sodium channels. The mechanisms of its antimalarial effects are not well understood.Gabon: A republic in west equatorial Africa, south of CAMEROON and west of the CONGO. Its capital is Libreville.Encephalitis: Inflammation of the BRAIN due to infection, autoimmune processes, toxins, and other conditions. Viral infections (see ENCEPHALITIS, VIRAL) are a relatively frequent cause of this condition.Toxoplasmosis, Ocular: Infection caused by the protozoan parasite TOXOPLASMA in which there is extensive connective tissue proliferation, the retina surrounding the lesions remains normal, and the ocular media remain clear. Chorioretinitis may be associated with all forms of toxoplasmosis, but is usually a late sequel of congenital toxoplasmosis. The severe ocular lesions in infants may lead to blindness.Primaquine: An aminoquinoline that is given by mouth to produce a radical cure and prevent relapse of vivax and ovale malarias following treatment with a blood schizontocide. It has also been used to prevent transmission of falciparum malaria by those returning to areas where there is a potential for re-introduction of malaria. Adverse effects include anemias and GI disturbances. (From Martindale, The Extra Pharmacopeia, 30th ed, p404)Sulfinpyrazone: A uricosuric drug that is used to reduce the serum urate levels in gout therapy. It lacks anti-inflammatory, analgesic, and diuretic properties.Protozoan Proteins: Proteins found in any species of protozoan.Point Mutation: A mutation caused by the substitution of one nucleotide for another. This results in the DNA molecule having a change in a single base pair.Somalia: Somalia is located on the east coast of Africa on and north of the Equator and, with Ethiopia, Eritrea, Djibouti, and Kenya, is often referred to as the Horn of Africa. It comprises Italy's former Trust Territory of Somalia and the former British Protectorate of Somaliland. The capital is Mogadishu.Parasitemia: The presence of parasites (especially malarial parasites) in the blood. (Dorland, 27th ed)Thymidylate Synthase: An enzyme of the transferase class that catalyzes the reaction 5,10-methylenetetrahydrofolate and dUMP to dihydrofolate and dTMP in the synthesis of thymidine triphosphate. (From Dorland, 27th ed) EC 184.108.40.206.Tanzania: A republic in eastern Africa, south of UGANDA and north of MOZAMBIQUE. Its capital is Dar es Salaam. It was formed in 1964 by a merger of the countries of TANGANYIKA and ZANZIBAR.Pneumonia, Pneumocystis: A pulmonary disease in humans occurring in immunodeficient or malnourished patients or infants, characterized by DYSPNEA, tachypnea, and HYPOXEMIA. Pneumocystis pneumonia is a frequently seen opportunistic infection in AIDS. It is caused by the fungus PNEUMOCYSTIS JIROVECII. The disease is also found in other MAMMALS where it is caused by related species of Pneumocystis.Comoros: A group of Indian Ocean Islands, the islands of Great Comoro, Anjouan, Mayotte, and Moheli, lying between northeast Mozambique and northwest Madagascar. The capital is Moroni. In 1914 they became a colony attached to Madagascar administratively and were made a French overseas territory in 1947. Except for Mayotte which remained French, Comoros became an independent republic in 1975. Comoros represents the Arabic qamar, moon, said by some scholars to be linked with the mystical Mountains of the Moon said to be somewhere in equatorial Africa. (From Webster's New Geographical Dictionary, 1988, p283 & Room, Brewer's Dictionary of Names, 1992, p122)Madagascar: One of the Indian Ocean Islands off the southeast coast of Africa. Its capital is Antananarivo. It was formerly called the Malagasy Republic. Discovered by the Portuguese in 1500, its history has been tied predominantly to the French, becoming a French protectorate in 1882, a French colony in 1896, and a territory within the French union in 1946. The Malagasy Republic was established in the French Community in 1958 but it achieved independence in 1960. Its name was changed to Madagascar in 1975. (From Webster's New Geographical Dictionary, 1988, p714)Trimethoprim-Sulfamethoxazole Combination: This drug combination has proved to be an effective therapeutic agent with broad-spectrum antibacterial activity against both gram-positive and gram-negative organisms. It is effective in the treatment of many infections, including PNEUMOCYSTIS PNEUMONIA in AIDS.Senegal: A republic in western Africa, southwest of MAURITANIA and east of MALI. Its capital is Dakar.Kenya: A republic in eastern Africa, south of ETHIOPIA, west of SOMALIA with TANZANIA to its south, and coastline on the Indian Ocean. Its capital is Nairobi.Central African Republic: A republic in central Africa south of CHAD and SUDAN, north of DEMOCRATIC REPUBLIC OF THE CONGO, and east of CAMEROON. The capital is Bangui.Anti-Infective Agents: Substances that prevent infectious agents or organisms from spreading or kill infectious agents in order to prevent the spread of infection.QuinolinesAngola: A republic in southern Africa, southwest of DEMOCRATIC REPUBLIC OF THE CONGO and west of ZAMBIA. Its capital is Luanda.Pneumocystis Infections: Infections with species in the genus PNEUMOCYSTIS, a fungus causing interstitial plasma cell pneumonia (PNEUMONIA, PNEUMOCYSTIS) and other infections in humans and other MAMMALS. Immunocompromised patients, especially those with AIDS, are particularly susceptible to these infections. Extrapulmonary sites are rare but seen occasionally.Mali: A country in western Africa, east of MAURITANIA and south of ALGERIA. Its capital is Bamako. From 1904-1920 it was known as Upper Senegal-Niger; prior to 1958, as French Sudan; 1958-1960 as the Sudanese Republic and 1959-1960 it joined Senegal in the Mali Federation. It became an independent republic in 1960.Pneumocystis: A genus of ascomycetous FUNGI, family Pneumocystidaceae, order Pneumocystidales. It includes various host-specific species causing PNEUMOCYSTIS PNEUMONIA in humans and other MAMMALS.Hexosaminidase A: A mammalian beta-hexosaminidase isoform that is a heteromeric protein comprized of both hexosaminidase alpha and hexosaminidase beta subunits. Deficiency of hexosaminidase A due to mutations in the gene encoding the hexosaminidase alpha subunit is a case of TAY-SACHS DISEASE. Deficiency of hexosaminidase A and HEXOSAMINIDASE B due to mutations in the gene encoding the hexosaminidase beta subunit is a case of SANDHOFF DISEASE.AIDS-Related Opportunistic Infections: Opportunistic infections found in patients who test positive for human immunodeficiency virus (HIV). The most common include PNEUMOCYSTIS PNEUMONIA, Kaposi's sarcoma, cryptosporidiosis, herpes simplex, toxoplasmosis, cryptococcosis, and infections with Mycobacterium avium complex, Microsporidium, and Cytomegalovirus.Gambia: A republic in western Africa, constituting an enclave within SENEGAL extending on both sides of the Gambia River. Its capital is Banjul, formerly Bathurst.Plasmodium berghei: A protozoan parasite of rodents transmitted by the mosquito Anopheles dureni.Drug Interactions: The action of a drug that may affect the activity, metabolism, or toxicity of another drug.Scintillation Counting: Detection and counting of scintillations produced in a fluorescent material by ionizing radiation.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Sudan: A country in northeastern Africa. The capital is Khartoum.Nigeria: A republic in western Africa, south of NIGER between BENIN and CAMEROON. Its capital is Abuja.Clindamycin: An antibacterial agent that is a semisynthetic analog of LINCOMYCIN.Ghana: A republic in western Africa, south of BURKINA FASO and west of TOGO. Its capital is Accra.Sulfamethoxazole: A bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. Its broad spectrum of activity has been limited by the development of resistance. (From Martindale, The Extra Pharmacopoeia, 30th ed, p208)Malawi: A republic in southern Africa east of ZAMBIA and MOZAMBIQUE. Its capital is Lilongwe. It was formerly called Nyasaland.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Drug Resistance, Microbial: The ability of microorganisms, especially bacteria, to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Drug Evaluation: Any process by which toxicity, metabolism, absorption, elimination, preferred route of administration, safe dosage range, etc., for a drug or group of drugs is determined through clinical assessment in humans or veterinary animals.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Fluorenes: A family of diphenylenemethane derivatives.