Parasitemia: The presence of parasites (especially malarial parasites) in the blood. (Dorland, 27th ed)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.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.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.Chagas Disease: Infection with the protozoan parasite TRYPANOSOMA CRUZI, a form of TRYPANOSOMIASIS endemic in Central and South America. It is named after the Brazilian physician Carlos Chagas, who discovered the parasite. Infection by the parasite (positive serologic result only) is distinguished from the clinical manifestations that develop years later, such as destruction of PARASYMPATHETIC GANGLIA; CHAGAS CARDIOMYOPATHY; and dysfunction of the ESOPHAGUS or COLON.Plasmodium chabaudi: A protozoan parasite of rodents transmitted by the mosquito Anopheles stephensi.Trypanosoma cruzi: The agent of South American trypanosomiasis or CHAGAS DISEASE. Its vertebrate hosts are man and various domestic and wild animals. Insects of several species are vectors.Trypanosomiasis: Infection with protozoa of the genus TRYPANOSOMA.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)Babesiosis: A group of tick-borne diseases of mammals including ZOONOSES in humans. They are caused by protozoa of the genus BABESIA, which parasitize erythrocytes, producing hemolysis. In the U.S., the organism's natural host is mice and transmission is by the deer tick IXODES SCAPULARIS.Plasmodium berghei: A protozoan parasite of rodents transmitted by the mosquito Anopheles dureni.Plasmodium: A genus of protozoa that comprise the malaria parasites of mammals. Four species infect humans (although occasional infections with primate malarias may occur). These are PLASMODIUM FALCIPARUM; PLASMODIUM MALARIAE; PLASMODIUM OVALE, and PLASMODIUM VIVAX. Species causing infection in vertebrates other than man include: PLASMODIUM BERGHEI; PLASMODIUM CHABAUDI; P. vinckei, and PLASMODIUM YOELII in rodents; P. brasilianum, PLASMODIUM CYNOMOLGI; and PLASMODIUM KNOWLESI in monkeys; and PLASMODIUM GALLINACEUM in chickens.Malaria, Vivax: Malaria caused by PLASMODIUM VIVAX. This form of malaria is less severe than MALARIA, FALCIPARUM, but there is a higher probability for relapses to occur. Febrile paroxysms often occur every other day.Pregnancy Complications, Parasitic: The co-occurrence of pregnancy and parasitic diseases. The parasitic infection may precede or follow FERTILIZATION.Antibodies, Protozoan: Immunoglobulins produced in a response to PROTOZOAN ANTIGENS.Plasmodium yoelii: A species of PLASMODIUM causing malaria in rodents.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.Babesia: A genus of tick-borne protozoan parasites that infests the red blood cells of mammals, including humans. There are many recognized species, and the distribution is world-wide.Babesia microti: A species of protozoa infecting humans via the intermediate tick vector IXODES scapularis. The other hosts are the mouse PEROMYSCUS leucopus and meadow vole MICROTUS pennsylvanicus, which are fed on by the tick. Other primates can be experimentally infected with Babesia microti.Trypanosomiasis, African: A disease endemic among people and animals in Central Africa. It is caused by various species of trypanosomes, particularly T. gambiense and T. rhodesiense. Its second host is the TSETSE FLY. Involvement of the central nervous system produces "African sleeping sickness." Nagana is a rapidly fatal trypanosomiasis of horses and other animals.Trypanosoma congolense: A species of Trypanosome hemoflagellates that is carried by tsetse flies and causes severe anemia in cattle. These parasites are also found in horses, sheep, goats, and camels.Malaria, Cerebral: A condition characterized by somnolence or coma in the presence of an acute infection with PLASMODIUM FALCIPARUM (and rarely other Plasmodium species). Initial clinical manifestations include HEADACHES; SEIZURES; and alterations of mentation followed by a rapid progression to COMA. Pathologic features include cerebral capillaries filled with parasitized erythrocytes and multiple small foci of cortical and subcortical necrosis. (From Adams et al., Principles of Neurology, 6th ed, p136)Antigens, Protozoan: Any part or derivative of any protozoan that elicits immunity; malaria (Plasmodium) and trypanosome antigens are presently the most frequently encountered.Anemia: A reduction in the number of circulating ERYTHROCYTES or in the quantity of HEMOGLOBIN.Artemisinins: A group of SESQUITERPENES and their analogs that contain a peroxide group (PEROXIDES) within an oxepin ring (OXEPINS).Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.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.Aotus trivirgatus: A species in the family AOTIDAE, inhabiting the forested regions of Central and South America (from Panama to the Amazon). Vocalizations occur primarily at night when they are active, thus they are also known as Northern night monkeys.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.Plasmodium malariae: A protozoan parasite that occurs primarily in subtropical and temperate areas. It is the causal agent of quartan malaria. As the parasite grows it exhibits little ameboid activity.Malaria Vaccines: Vaccines made from antigens arising from any of the four strains of Plasmodium which cause malaria in humans, or from P. berghei which causes malaria in rodents.Trypanosoma: A genus of flagellate protozoans found in the blood and lymph of vertebrates and invertebrates, both hosts being required to complete the life cycle.Pyrimethamine: One of the FOLIC ACID ANTAGONISTS that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis.Papua New Guinea: A country consisting of the eastern half of the island of New Guinea and adjacent islands, including New Britain, New Ireland, the Admiralty Islands, and New Hanover in the Bismarck Archipelago; Bougainville and Buka in the northern Solomon Islands; the D'Entrecasteaux and Trobriand Islands; Woodlark (Murua) Island; and the Louisiade Archipelago. It became independent on September 16, 1975. Formerly, the southern part was the Australian Territory of Papua, and the northern part was the UN Trust Territory of New Guinea, administered by Australia. They were administratively merged in 1949 and named Papua and New Guinea, and renamed Papua New Guinea in 1971.Sulfadoxine: A long acting sulfonamide that is used, usually in combination with other drugs, for respiratory, urinary tract, and malarial infections.Protozoan Proteins: Proteins found in any species of protozoan.Malawi: A republic in southern Africa east of ZAMBIA and MOZAMBIQUE. Its capital is Lilongwe. It was formerly called Nyasaland.Plasmodium cynomolgi: A protozoan parasite that occurs naturally in the macaque. It is similar to PLASMODIUM VIVAX and produces a type of malaria similar to vivax malaria (MALARIA, VIVAX). This species has been found to give rise to both natural and experimental human infections.Aotidae: A family of the New World monkeys inhabiting the forests of South and Central America. There is a single genus and several species occurring in this family, including AOTUS TRIVIRGATUS (Northern night monkeys).Trypanosoma lewisi: A trypanosome found in the blood of adult rats and transmitted by the rat flea. It is generally non-pathogenic in adult rats but can cause lethal infection in suckling rats.Merozoite Surface Protein 1: A surface protein found on Plasmodium species which induces a T-cell response. The antigen is polymorphic, sharing amino acid sequence homology among PLASMODIUM FALCIPARUM; PLASMODIUM CHABAUDI; PLASMODIUM VIVAX; and PLASMODIUM YOELII.DNA, Protozoan: Deoxyribonucleic acid that makes up the genetic material of protozoa.Drug Combinations: Single preparations containing two or more active agents, for the purpose of their concurrent administration as a fixed dose mixture.Trypanocidal Agents: Agents destructive to the protozoal organisms belonging to the suborder TRYPANOSOMATINA.Gabon: A republic in west equatorial Africa, south of CAMEROON and west of the CONGO. Its capital is Libreville.Trypanosomiasis, Bovine: Infection in cattle caused by various species of trypanosomes.Fluorenes: A family of diphenylenemethane derivatives.Trypanosoma vivax: An active blood parasite that is present in practically all domestic animals in Africa, the West Indies, and parts of Central and South America. In Africa, the insect vector is the tsetse fly. In other countries, infection is by mechanical means indicating that the parasites have been introduced to these countries and have been able to maintain themselves in spite of the lack of a suitable intermediate host. It is a cause of nagana, the severity of which depends on the species affected.Gravidity: The number of pregnancies, complete or incomplete, experienced by a female. It is different from PARITY, which is the number of offspring borne. (From Stedman, 26th ed)Parasite Load: Measure of the number of the PARASITES present in a host organism.Mefloquine: A phospholipid-interacting antimalarial drug (ANTIMALARIALS). It is very effective against PLASMODIUM FALCIPARUM with very few side effects.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.Chagas Cardiomyopathy: A disease of the CARDIAC MUSCLE developed subsequent to the initial protozoan infection by TRYPANOSOMA CRUZI. After infection, less than 10% develop acute illness such as MYOCARDITIS (mostly in children). The disease then enters a latent phase without clinical symptoms until about 20 years later. Myocardial symptoms of advanced CHAGAS DISEASE include conduction defects (HEART BLOCK) and CARDIOMEGALY.Atovaquone: A hydroxynaphthoquinone that has antimicrobial activity and is being used in antimalarial protocols.Diminazene: An effective trypanocidal agent.Indonesia: A republic stretching from the Indian Ocean east to New Guinea, comprising six main islands: Java, Sumatra, Bali, Kalimantan (the Indonesian portion of the island of Borneo), Sulawesi (formerly known as the Celebes) and Irian Jaya (the western part of New Guinea). Its capital is Djakarta. The ethnic groups living there are largely Chinese, Arab, Eurasian, Indian, and Pakistani; 85% of the peoples are of the Islamic faith.Mice, Inbred BALB CProguanil: A biguanide compound which metabolizes in the body to form cycloguanil, an anti-malaria agent.Neurosyphilis: Infections of the central nervous system caused by TREPONEMA PALLIDUM which present with a variety of clinical syndromes. The initial phase of infection usually causes a mild or asymptomatic meningeal reaction. The meningovascular form may present acutely as BRAIN INFARCTION. The infection may also remain subclinical for several years. Late syndromes include general paresis; TABES DORSALIS; meningeal syphilis; syphilitic OPTIC ATROPHY; and spinal syphilis. General paresis is characterized by progressive DEMENTIA; DYSARTHRIA; TREMOR; MYOCLONUS; SEIZURES; and Argyll-Robertson pupils. (Adams et al., Principles of Neurology, 6th ed, pp722-8)Parasitology: The study of parasites and PARASITIC DISEASES.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.Sporozoites: The product of meiotic division of zygotes in parasitic protozoa comprising haploid cells. These infective cells invade the host and undergo asexual reproduction producing MEROZOITES (or other forms) and ultimately gametocytes.Hemoglobins: The oxygen-carrying proteins of ERYTHROCYTES. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements.Fever: An abnormal elevation of body temperature, usually as a result of a pathologic process.Eurycoma: A plant genus of the family SIMAROUBACEAE. Members contain quassinoids. There is Malaysian folk use of these plants for male virility.Parasitic Sensitivity Tests: Tests that demonstrate the relative effectiveness of chemotherapeutic agents against specific parasites.Mice, Inbred C57BLNitroimidazolesErythrocyte Count: The number of RED BLOOD CELLS per unit volume in a sample of venous BLOOD.Plasmodium ovale: A species of protozoan parasite causing MALARIA. It is the rarest of the four species of PLASMODIUM infecting humans, but is common in West African countries and neighboring areas.Protozoan Vaccines: Suspensions of attenuated or killed protozoa administered for the prevention or treatment of infectious protozoan disease.Endemic Diseases: The constant presence of diseases or infectious agents within a given geographic area or population group. It may also refer to the usual prevalence of a given disease with such area or group. It includes holoendemic and hyperendemic diseases. A holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). A hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. (Last, A Dictionary of Epidemiology, 3d ed, p53, 78, 80)Microscopy: The use of instrumentation and techniques for visualizing material and details that cannot be seen by the unaided eye. It is usually done by enlarging images, transmitted by light or electron beams, with optical or magnetic lenses that magnify the entire image field. With scanning microscopy, images are generated by collecting output from the specimen in a point-by-point fashion, on a magnified scale, as it is scanned by a narrow beam of light or electrons, a laser, a conductive probe, or a topographical probe.Anopheles: A genus of mosquitoes (CULICIDAE) that are known vectors of MALARIA.Spleen: An encapsulated lymphatic organ through which venous blood filters.Placenta Diseases: Pathological processes or abnormal functions of the PLACENTA.Eucoccidiida: An order of parasitic protozoa found in blood cells and epithelial cells of vertebrates and invertebrates. Life cycles involve both sexual and asexual phases.Sickle Cell Trait: The condition of being heterozygous for hemoglobin S.Trypanosoma brucei brucei: A hemoflagellate subspecies of parasitic protozoa that causes nagana in domestic and game animals in Africa. It apparently does not infect humans. It is transmitted by bites of tsetse flies (Glossina).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.SesquiterpenesInsect Bites and Stings: Bites and stings inflicted by insects.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Hematocrit: The volume of packed RED BLOOD CELLS in a blood specimen. The volume is measured by centrifugation in a tube with graduated markings, or with automated blood cell counters. It is an indicator of erythrocyte status in disease. For example, ANEMIA shows a low value; POLYCYTHEMIA, a high value.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.Splenectomy: Surgical procedure involving either partial or entire removal of the spleen.Ghana: A republic in western Africa, south of BURKINA FASO and west of TOGO. Its capital is Accra.Interferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Benin: A republic in western Africa, south of NIGER and between TOGO and NIGERIA. Its capital is Porto-Novo. It was formerly called Dahomey. In the 17th century it was a kingdom in the southern area of Africa. Coastal footholds were established by the French who deposed the ruler by 1892. It was made a French colony in 1894 and gained independence in 1960. Benin comes from the name of the indigenous inhabitants, the Bini, now more closely linked with southern Nigeria (Benin City, a town there). Bini may be related to the Arabic bani, sons. (From Webster's New Geographical Dictionary, 1988, p136, 310 & Room, Brewer's Dictionary of Names, 1992, p60)Theileria: A genus of tick-borne protozoa parasitic in the lymphocytes, erythrocytes, and endothelial cells of mammals. Its organisms multiply asexually and then invade erythrocytes, where they undergo no further reproduction until ingested by a transmitting tick.Host-Parasite Interactions: The relationship between an invertebrate and another organism (the host), one of which lives at the expense of the other. Traditionally excluded from definition of parasites are pathogenic BACTERIA; FUNGI; VIRUSES; and PLANTS; though they may live parasitically.Plasmodium knowlesi: A protozoan parasite from Southeast Asia that causes monkey malaria. It is naturally acquired by man in Malaysia and can also be transmitted experimentally to humans.Blood: The body fluid that circulates in the vascular system (BLOOD VESSELS). Whole blood includes PLASMA and BLOOD CELLS.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Quinolinium CompoundsUganda: A republic in eastern Africa, south of SUDAN and west of KENYA. Its capital is Kampala.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.Ethanolamines: AMINO ALCOHOLS containing the ETHANOLAMINE; (-NH2CH2CHOH) group and its derivatives.Arthropod Vectors: Arthropods, other than insects and arachnids, which transmit infective organisms from one host to another or from an inanimate reservoir to an animate host.Splenomegaly: Enlargement of the spleen.Placenta: A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (CHORIONIC VILLI) derived from TROPHOBLASTS and a maternal portion (DECIDUA) derived from the uterine ENDOMETRIUM. The placenta produces an array of steroid, protein and peptide hormones (PLACENTAL HORMONES).Hemoglobin C: A commonly occurring abnormal hemoglobin in which lysine replaces a glutamic acid residue at the sixth position of the beta chains. It results in reduced plasticity of erythrocytes.Nigeria: A republic in western Africa, south of NIGER between BENIN and CAMEROON. Its capital is Abuja.Antiprotozoal Agents: Substances that are destructive to protozoans.Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.BenzoxazolesBoliviaImmunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Burkina Faso: A republic in western Africa, south and east of MALI and west of NIGER. Its capital is Ouagadougou. It was formerly called Upper Volta until 1984.Xenodiagnosis: A method for diagnosing a disease in one organism by inoculating the putative causative organism in a second animal of a different species. It has been used for the detection of parasites (Trypanosoma cruzi and Trichinella spiralis) when peripheral blood smears are negative. (Segen, Current Med Talk, 1995)Myanmar: A republic of southeast Asia, northwest of Thailand, long familiar as Burma. Its capital is Yangon, formerly Rangoon. Inhabited by people of Mongolian stock and probably of Tibetan origin, by the 3d century A.D. it was settled by Hindus. The modern Burmese state was founded in the 18th century but was in conflict with the British during the 19th century. Made a crown colony of Great Britain in 1937, it was granted independence in 1947. In 1989 it became Myanmar. The name comes from myanma, meaning the strong, as applied to the Burmese people themselves. (From Webster's New Geographical Dictionary, 1988, p192 & Room, Brewer's Dictionary of Names, 1992, p367)Theileriasis: Infection of cattle, sheep, or goats with protozoa of the genus THEILERIA. This infection results in an acute or chronic febrile condition.ColombiaTime Factors: Elements of limited time intervals, contributing to particular results or situations.Thailand: Formerly known as Siam, this is a Southeast Asian nation at the center of the Indochina peninsula. Bangkok is the capital city.Amodiaquine: A 4-aminoquinoline compound with anti-inflammatory properties.Infant, Newborn: An infant during the first month after birth.Saimiri: A genus of the family CEBIDAE consisting of four species: S. boliviensis, S. orstedii (red-backed squirrel monkey), S. sciureus (common squirrel monkey), and S. ustus. They inhabit tropical rain forests in Central and South America. S. sciureus is used extensively in research studies.Disease Susceptibility: A constitution or condition of the body which makes the tissues react in special ways to certain extrinsic stimuli and thus tends to make the individual more than usually susceptible to certain diseases.Merozoites: Uninuclear cells or a stage in the life cycle of sporozoan protozoa. Merozoites, released from ruptured multinucleate SCHIZONTS, enter the blood stream and infect the ERYTHROCYTES.Life Cycle Stages: The continuous sequence of changes undergone by living organisms during the post-embryonic developmental process, such as metamorphosis in insects and amphibians. This includes the developmental stages of apicomplexans such as the malarial parasite, PLASMODIUM FALCIPARUM.Antiparasitic Agents: Drugs used to treat or prevent parasitic infections.Immunization, Passive: Transfer of immunity from immunized to non-immune host by administration of serum antibodies, or transplantation of lymphocytes (ADOPTIVE TRANSFER).Infant, Low Birth Weight: An infant having a birth weight of 2500 gm. (5.5 lb.) or less but INFANT, VERY LOW BIRTH WEIGHT is available for infants having a birth weight of 1500 grams (3.3 lb.) or less.Horse Diseases: Diseases of domestic and wild horses of the species Equus caballus.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Infectious Disease Transmission, Vertical: The transmission of infectious disease or pathogens from one generation to another. It includes transmission in utero or intrapartum by exposure to blood and secretions, and postpartum exposure via breastfeeding.Malaria, Avian: Any of a group of infections of fowl caused by protozoa of the genera PLASMODIUM, Leucocytozoon, and Haemoproteus. The life cycles of these parasites and the disease produced bears strong resemblance to those observed in human malaria.Recurrence: The return of a sign, symptom, or disease after a remission.Drug Therapy, Combination: Therapy with two or more separate preparations given for a combined effect.

Malaria prophylaxis using azithromycin: a double-blind, placebo-controlled trial in Irian Jaya, Indonesia. (1/1555)

New drugs are needed for preventing drug-resistant Plasmodium falciparum malaria. The prophylactic efficacy of azithromycin against P. falciparum in malaria-immune Kenyans was 83%. We conducted a double-blind, placebo-controlled trial to determine the prophylactic efficacy of azithromycin against multidrug-resistant P. falciparum malaria and chloroquine-resistant Plasmodium vivax malaria in Indonesian adults with limited immunity. After radical cure therapy, 300 randomized subjects received azithromycin (148 subjects, 750-mg loading dose followed by 250 mg/d), placebo (77), or doxycycline (75, 100 mg/d). The end point was slide-proven parasitemia. There were 58 P. falciparum and 29 P. vivax prophylaxis failures over 20 weeks. Using incidence rates, the protective efficacy of azithromycin relative to placebo was 71.6% (95% confidence interval [CI], 50.3-83.8) against P. falciparum malaria and 98.9% (95% CI, 93.1-99.9) against P. vivax malaria. Corresponding figures for doxycycline were 96.3% (95% CI, 85.4-99.6) and 98% (95% CI, 88.0-99.9), respectively. Daily azithromycin offered excellent protection against P. vivax malaria but modest protection against P. falciparum malaria.  (+info)

gammadelta T cells contribute to control of chronic parasitemia in Plasmodium chabaudi infections in mice. (2/1555)

During a primary infection of mice with Plasmodium chabaudi, gammadelta T cells are stimulated and their expansion coincides with recovery from the acute phase of infection in normal mice or with chronic infections in B cell-deficient mice (mu-MT). To determine whether the large gammadelta T cell pool observed in female B cell-deficient mice is responsible for controlling the chronic infection, studies were done using double-knockout mice deficient in both B and gammadelta cells (mu-MT x delta-/-TCR) and in gammadelta T cell-depleted mu-MT mice. In both types of gammadelta T cell-deficient mice, the early parasitemia following the peak of infection was exacerbated, and the chronic parasitemia was maintained at significantly higher levels in the absence of gammadelta T cells. The majority of gammadelta T cells in C57BL/6 and mu-MT mice responding to infection belonged predominantly to a single family of gammadelta T cells with TCR composed of Vgamma2Vdelta4 chains and which produced IFN-gamma rather than IL-4.  (+info)

Host haematological factors influencing the transmission of Plasmodium falciparum gametocytes to Anopheles gambiae s.s. mosquitoes. (3/1555)

We investigated the relationship between selected host haematological and parasitological parameters and the density and infectivity of Plasmodium falciparum gametocytes. 143 individuals (age range 1-62 years) attending an outpatient clinic in Farafenni, The Gambia, who had peripheral blood gametocytaemia were recruited (mean gametocyte density 123.7/microl, range 5-17,000/microl). Of the parameters measured, packed cell volume (PCV), reticulocyte count (RetC) and lymphocyte count (LyC) were significantly associated with gametocyte density (r = - 0.17, P < 0.05; r = 0.21, P < 0.01; r = 0.18, P < 0.05, respectively). Data from membrane feeding experiments in which 15 or more mosquitoes were dissected showed that 60.7% (53/87) of gametocyte carriers infected one or more mosquitoes. Gametocyte density was strongly correlated with transmission success (TS) (r = 0.3, P < 0.005) and, in successful infections, with both mosquito prevalence (MP) (r = 0.36, P < 0.005) and mean oocyst burden (MOB) (r = 0.65, P < 0.0001). None of the other factors measured were significantly associated with any of these indices in bivariate analysis. Regression modelling showed that both gametocyte density and PCV were positively associated with gametocyte carrier infectivity to mosquitoes (LRchi2 = 100.7 and 47.2, respectively) and, in successful infections, with MOB (beta = 0.16, t = 4.9, P < 0.001; beta = 0.02, t = 2.3, P < 0.05, respectively). The positive association with PCV suggests that blood meal quality influences infection probably as a nutritional requirement, however, as this effect was most apparent at high gametocyte densities, its epidemiological significance is questionable. Though the haematological parameters associated with gametocyte density are a direct consequence of asexual infection, they may also represent an adaptive mechanism for optimization of sexual stage development.  (+info)

Gamma interferon production is critical for protective immunity to infection with blood-stage Plasmodium berghei XAT but neither NO production nor NK cell activation is critical. (4/1555)

We have examined the roles of gamma interferon (IFN-gamma), nitric oxide (NO), and natural killer (NK) cells in the host resistance to infection with the blood-stage malarial parasite Plasmodium berghei XAT, an irradiation-induced attenuated variant of the lethal strain P. berghei NK65. Although the infection with P. berghei XAT enhanced NK cell lytic activity of splenocytes, depletion of NK1.1(+) cells caused by the treatment of mice with anti-NK1.1 antibody affected neither parasitemia nor IFN-gamma production by their splenocytes. The P. berghei XAT infection induced a large amount of NO production by splenocytes during the first peak of parasitemia, while P. berghei NK65 infection induced a small amount. Unexpectedly, however, mice deficient in inducible nitric oxide synthase (iNOS-/-) cleared P. berghei XAT after two peaks of parasitemia were observed, as occurred for wild-type control mice. Although the infected iNOS-/- mouse splenocytes did not produce a detectable level of NO, they produced an amount of IFN-gamma comparable to that produced by wild-type control mouse splenocytes, and treatment of these mice with neutralizing anti-IFN-gamma antibody led to the progression of parasitemia and fatal outcome. CD4(-/-) mice infected with P. berghei XAT could not clear the parasite, and all these mice died with apparently reduced IFN-gamma production. Furthermore, treatment with carrageenan increased the susceptibility of mice to P. berghei XAT infection. These results suggest that neither NO production nor NK cell activation is critical for the resistance to P. berghei XAT infection and that IFN-gamma plays an important role in the elimination of malarial parasites, possibly by the enhancement of phagocytic activity of macrophages.  (+info)

Interference of natural mouse hepatitis virus infection with cytokine production and susceptibility to Trypanosoma cruzi. (5/1555)

Mouse hepatitis virus (MHV) infection can have a pronounced impact on several investigation areas. Reports on natural MHV outbreaks are rare and most studies have been conducted by deliberately infecting mice with MHV laboratory strains that cause moderate to severe disturbances to the immune system. We have investigated the effects of a natural acute outbreak of MHV in our otherwise specific-pathogen-free (SPF) inbred mouse colonies, and of enzootic chronic MHV infection on cytokine production and resistance to the intracellular pathogen Trypanosoma cruzi. We found that BALB/c and/or C57BL/6 SPF mice that had been injected with T. cruzi blood trypomastigotes from recently MHV-contaminated (MHV+) mice developed significantly higher parasite blood counts, accelerated death, and showed higher IL-10 production by spleen cells than their counterparts whose T. cruzi inoculum was derived from MHV-negative (MHV-) donors. Interferon-gamma (IFN-gamma) production by MHV+ and MHV- mice was not significantly different. In contrast, T. cruzi infection of chronically MHV-infected mice did not result in major changes in the course of infection when compared with that observed in mice from MHV- colonies, although a trend to higher parasitaemia levels was observed in BALB/c MHV+ mice. Nevertheless, both BALB/c and C57BL/6 T. cruzi-infected MHV+ mice had diminished IFN-gamma production to parasite-antigen stimulation in comparison with similarly infected MHV- mice. Interleukin-10 (IL-10) production levels by spleen cells did not differ between chronic MHV+ and MHV- mice, but IFN-gamma neutralization by monoclonal antibody treatment of anti-CD3-stimulated spleen cell cultures showed higher levels of IL-10 synthesis in MHV+ BALB/c mice.  (+info)

Modulation of experimental blood stage malaria through blockade of the B7/CD28 T-cell costimulatory pathway. (6/1555)

Recent studies have implicated cytokines associated with CD4+ T lymphocytes of both T helper (Th)1 and Th2 subsets in resistance to experimental blood stage malaria. As the B7/CD28 costimulatory pathway has been shown to influence the differentiation of Th cell subsets, we investigated the contribution of the B7 molecules CD80 and CD86 to Th1/Th2 cytokine and immunoglobulin isotype profiles and to the development of a protective immune response to malaria in NIH mice infected with Plasmodium chabaudi. Effective blockade of CD86/CD28 interaction was demonstrated by elimination of interleukin (IL)-4 and up-regulation of interferon (IFN)-gamma responses by P. chabaudi-specific T cells and by reduction of P. chabaudi-specific immunoglobulin G1 (IgG1). The shift towards a Th1 cytokine pattern corresponded with efficient control of acute parasitaemia but an inability to resolve chronic infection. Moreover, combined CD80/CD86 blockade by using anti-CD80 and anti-CD86 monoclonal antibodies raised IFN-gamma production over that seen with CD86 blockade alone, with augmentation of this Th1-associated cytokine reducing levels of peak primary parasitaemia. These results demonstrate that IL-4 production by T cells in P. chabaudi-infected NIH mice is dependent upon CD86/CD28 interaction and that IL-4 and IFN-gamma contribute significantly, at different times of infection, to host resistance to blood stage malaria. In addition, combined CD80/CD86 blockade resulted in preferential expansion of IFN-gamma-producing T cells during P. chabaudi infection, suggesting that costimulatory pathways other than B7/CD28 may contribute to T-cell activation during continuous antigen stimulation. This study indicates a role for B7/CD28 costimulation in modulating the CD4+ T-cell response during malaria, and further suggests involvement of this pathway in other infectious and autoimmune diseases in which the Th cell immune response is also skewed.  (+info)

Induction of the trypanosome lymphocyte-triggering factor (TLTF) and neutralizing antibodies to the TLTF in experimental african trypanosomiasis. (7/1555)

We have demonstrated that African trypanosomes secrete a novel trypanokine, the trypanosome-derived lymphocyte-triggering factor (TLTF), which activates CD8+ cells to produce interferon-gamma (IFN-gamma) that in turn stimulates parasite growth. The gene for TLTF was recently cloned, and recombinant TLTF (rTLTF) showed bioactivity that was similar to native TLTF. In this work, we employed two anti-TLTF monoclonal antibodies (mAbs) to detect levels of TLTF during Trypanosoma brucei brucei (T. b. brucei ) infections in mice. Furthermore, rTLTF was utilized to assess levels of anti-TLTF antibodies. Mice with intact genes (wild type), and knockout mice with disrupted IFN-gamma (IFN-gamma-/-) or IFN-gammaR (IFN-gammaR-/-) genes were studied. The knockout mice were used in order to illustrate the role of IFN-gamma in the production of antibodies to TLTF. While wild-type mice showed high parasitaemia accompanied by high TLTF levels and low anti-TLTF antibodies at day 3 postinfection (p.i.), low TLTF was measured together with increased anti-TLTF antibodies at day 21 p.i. IFN-gamma-/- mice exhibited very low parasitaemia, TLTF and anti-TLTF antibody levels. In contrast, IFN-gammaR-/- mice revealed very high parasitaemia, increased TLTF levels, but decreased anti-TLTF antibodies. In a biological assay for TLTF, Fab' fragments of anti-TLTF antibodies dose dependently inhibited the TLTF-induced IFN-gamma production by splenocytes, suggesting a regulatory importance of these antibodies. Our data demonstrate a role of IFN-gamma in the generation of neutralizing antibodies to TLTF. Furthermore, the induction of TLTF and its antibodies may constitute a new approach for future diagnosis of African trypanosomiasis.  (+info)

Occurrence of Leishmania infantum parasitemia in asymptomatic blood donors living in an area of endemicity in southern France. (8/1555)

Visceral leishmaniosis (VL) due to Leishmania infantum (L. chagasi) is a lethal disease if untreated, but asymptomatic L. infantum infections have been reported previously. A better understanding of parasite transmission, dissemination, and survival in the human host is needed. The purpose of this study was to assess whether L. infantum circulated in peripheral blood of subjects with no history of VL. Sera from 565 blood donors were screened by Western blotting to detect Leishmania-specific antibodies and identify individuals with probable past exposure to Leishmania. Seropositivity was found in 76 donors whose buffy coats were examined by PCR and direct culture. The parasite minicircle kinetoplast DNA was amplified from blood samples of nine donors. Promastigotes were detected by culture in blood samples from nine donors. Only two donors were PCR and culture positive. These results indicate that L. infantum circulates intermittently and at low density in the blood of healthy seropositive individuals, who thus appear to be asymptomatic carriers. Implications for the safety of blood transfusion are discussed.  (+info)

  • The methods to be used for quantifying parasitemia depends on the parasitic species and its life cycle. (wikipedia.org)
  • Systematic measurement of parasitemia is important in many phases of the assessment of disease, such as in diagnosis and in the follow-up of therapy, particularly in the chronic phase, when cure depends on ascertaining a parasitemia of zero. (wikipedia.org)
  • The use of molecular biology techniques, such as PCR has been used increasingly as a tool to measure parasitemia, especially in patients in the chronic phase of disease. (wikipedia.org)
  • 0.001) observed in patients with SM and CM. This effect was independent of covariates (ethnicity, age, parasitaemia, sex). (lshtm.ac.uk)
  • With exceptional erythrocyte planning and great techs Also, the recognition limit is normally low (0.001% parasitemia) and approximately 1 hr is necessary for the recognition of an adequate variety of infected erythrocytes , . (recyclers-info.com)
  • 0.001), flexión del tronco en silla (p=0.018) y juntar las manos tras la espalda (p=0.014). (scielo.org)
  • There's a strong link between parasitaemia (the percentage of red blood cells that are infected), mortality and disease severity, and the faster you achieve complete clearance of infected cells, the better the prognosis for the patient. (medisieve.com)
  • Artemisinin as a single dose (oral in adults and as a suppository in children) in combination with mefloquine was effective in rapidly lowering parasitaemia and in preventing recrudescence in hospital in-patients and in out-patients attending a rural health clinic. (ox.ac.uk)
  • MSP alone as a single dose also rapidly reduced parasitaemia (but not as quickly as the artemisinin-mefloquine combination in out-patient children) and prevented recrudescence. (ox.ac.uk)
  • Milne discovered that most regular diagnostic laboratories attained low recognition awareness (typical generally, 0.01% parasitemia) on study of the results from Uk laboratories submitted towards the Malaria Guide Laboratory . (recyclers-info.com)
  • Dr Frodsham added: "Early results suggest we could reduce parasitaemia in a child by more than 90% in just two hours. (medisieve.com)
  • DISCUSSION: This study adds to the available evidence on the wide-scale presence of submicroscopic parasitaemia by quantifying submicroscopic parasite densities and concurrent gametocyte densities. (lshtm.ac.uk)
  • This dataverse contains the code and relevant datasets used to calculate parasitemia from images gathered as a part of a portable microscopy research study. (tdl.org)
  • Recently, we connected this aggressive phenotype to the presence of Leishmania RNA virus (LRV) in strains of L. guyanensis, showing that LRV is responsible for elevated parasitaemia, destructive hyper-inflammation and an overall exacerbation of the disease. (pubfacts.com)
  • In murine types of infections, it's been proven that Compact disc8+ T lymphocytes play essential jobs in the control of the parasitemia , . (healthyfutureforkids.com)