Genetic diversity, clonality and sexuality in Toxoplasma gondii *

The epidemiology of malaria in 2 riverine localities in Rondĵnia, Brazilian western Amazĵnia, was assessed by a 1-year study at Portuchuelo, and a cross-sectional survey at riverine communities at Rio Machado (= Ji-Parana). Plasmodium spp. infections were diagnosed by light microscopy and by polymerase chain reaction (PCR) amplification of ribosomal DNA. PCR was 6-7 times more efficient than microscopy for detecting plasmodial infections. Both Plasmodium vivax and Plasmodium falciparum infections occurred as asymptomatic and symptomatic forms of the disease. The relation between symptomatic and asymptomatic clinical forms was roughly similar for both species of Plasmodium. Symptomless patients were monitored for 2 months. The prevalence of symptomless infections was 4-5 times higher than the symptomatic ones--respectively, 20% and 4.6% for Portuchuelo and 49.5% and 10% for Ji-Parana. Symptomatic malaria occurred mostly in patients in younger age groups. In contrast, there was a significant association of symptomless malaria with older age groups (medians of 26.5 and 21 years, respectively, for Portuchuelo and Ji-Parana), whereas the age medians for symptomatic malaria were 14 and 8 years, respectively, in the 2 regions. Symptomatic malaria also was more prevalent in groups living for shorter times in Amazĵnia (13 and 4 years, respectively, for Portuchuelo and Ji-ParanA) as compared with symptomless malaria, which was more prevalent in groups living for longer periods in the region (medians of 25.5 and 18 years, respectively, for Portuchuelo and Ji-Parana). The high prevalence of symptomless malaria may pose new problems for the currently adopted strategy for the control of malaria in the Amazonian region, which is essentially based on the treatment of symptomatic patients.

High prevalence of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in native Amazonian populations.

Antimalarial drugs are key tools for the control and elimination of malaria. Recent decreases in the global malaria burden are likely due, in part, to the deployment of artemisinin-based combination therapies. Therefore, the emergence and potential spread of artemisinin-resistant parasites in southeast Asia and changes in sensitivities to artemisinin partner drugs have raised concerns. In recognition of this urgent threat, the International Centers of Excellence for Malaria Research (ICEMRs) are closely monitoring antimalarial drug efficacy and studying the mechanisms underlying drug resistance. At multiple sentinel sites of the global ICEMR network, research activities include clinical studies to track the efficacies of antimalarial drugs, ex vivo/in vitro assays to measure drug susceptibilities of parasite isolates, and characterization of resistance-mediating parasite polymorphisms. Taken together, these efforts offer an increasingly comprehensive assessment of the efficacies of antimalarial therapies, and enable us to predict the emergence of drug resistance and to guide local antimalarial drug policies. Here we briefly review worldwide antimalarial drug resistance concerns, summarize research activities of the ICEMRs related to drug resistance, and assess the global impacts of the ICEMR programs.

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Antimalarial Drug Resistance: Literature Review and Activities and Findings of the ICEMR Network

Spread and evolution of Plasmodium falciparum drug resistance

Multidrug resistance is a major obstacle to the control of Plasmodium falciparum malaria, and its origins and modes of dissemination are imperfectly understood. In this study, haplotyping and microsatellite analysis of malaria from 5 regions of the South American Amazon support the conclusion that the parasite mutations conferring mid- and high-level resistance to the antifolate combination sulfadoxine-pyrimethamine have a common origin. Parasites harboring these mutations are also found to share drug-resistance alleles that confer a unique chloroquine resistance phenotype and to be similar at loci not linked to drug resistance, although not genetically identical. Since the 1980s, multidrug-resistant P. falciparum has spread in a north-northwest manner across the continent, from an origin likely in the lower Amazon. This study highlights the importance of continent-wide malaria-control policies and suggests that the containment of resistance to the next generation of therapies may be feasible.

Origin and Dissemination of Plasmodium falciparum Drug-Resistance Mutations in South America

Serological examination for Toxoplasma gondii in human blood samples and in blood samples from ten different species of animals obtained in Manaus, State of Amazonas-Brazil, are compared with results obtained from similar examinations of blood from humans living in other areas of the Amazon basin. The domestic cat (Felis catus) showed the highest levels of antibody for Toxoplasma gondii, whereas the domestic chicken (Gallus domesticus) and duck (Cairina sp) the lowest. The other animals showed similar intermediate levels of antibody to this protozoa. The authors discuss the results and several aspects of the involvement in epidemiology of toxoplasmosis and call attention to some transmission mechanisms not yet elucidated.

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Prevalência da infecção pelo Toxoplasma gondii em animais domésticos, silvestres e grupamentos humanos da Amazônia

The prevalence of chloroquine-resistant falciparum malaria was determined for humans living at 28 different sites in the Brazilian Amazon. Blood samples obtained from each patient were defibrinated, placed in vials containing 0.5% glucose and or chloroquine and incubated for 24 hours at 39-40 degrees C without agitation. In vitro sensitivity of the parasite to four different concentrations of chloroquine was determined for each sample. After 24 hours of incubation, trophozoites of Plasmodium falciparum developed to schizonts in all control cultures (no chloroquine) as well as in 80.6, 48.4, 11.8 and 7.5% of the cultures containing 0.5, 1.0, 2.0, and 3.0 nmol chloroquine/ml blood, respectively. Chloroquine-resistant P. falciparum was found in blood samples from all 28 locations, indicating that such resistance is widely spread in the Brazilian Amazon.

Prevalence of chloroquine-resistant falciparum malaria in the Brazilian Amazon.

In April of 1977 an outbreak of falciparum malaria occurred among the Mayongong Indians, located at Uauaris in the Territory of Roraima, Brazil. Blood specimens from 157 Indians were examined for Plasmodium; 62 were found to be infected. In three cases the infection was not cured with chloroquine but responded favorably to the drug combination of sulfadoxine and pyrimethamine (Fansidar®).

Drug-Resistant Falciparum Malaria among the Mayongong Indians in the Brazilian Amazon

Overall rates of malaria for Amazonas have be dropping since 1973. An exception to this trend are the newly opened roads, BR-174 (Manaus/Boa Vista) and BR-319 (Manaus/Porto Velho). BR-174 has been an endemic focus of drug resistant falciparum malaria and the vector Anopheles darlingi exhibit behavior resistance to DDT. Since 1974 when the Hospital de Molestias Tropicais de Manaus first opened, nearly all hospitalized cases of malaria have been treated at this facility. Malaria cases (out patients) as well as hospitalized cases were studied to determine the nature of malaria. Data is presented by species of Plasmodium, month, year and by age and sex. Data is also presented from the military Hospital. Individuals from BR-174 constitued over 65% of all malaria cases seen by the hospital. This study is important because of its implications for future development of the Amazon.

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Aspectos epidemiológicos da malária no Amazonas

Resumo Os autores fazem um estudo social, sanitario e parasitologico da cidade de Nova Olinda do Norte, Amazonas - Brasil, dando enfase aos tipos de habitacoes, destino dos dejetos, tipos de sanitarios, fonte de agua para o consumo e tratamento da mesma, assim como a prevalencia dos helmintos e protozoarios. Discutem os resultados comparando-os com resultados encontrados em outras cidades da Amazonia.

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José João Ferraroni

Papers

Prevalência da infecção pelo Toxoplasma gondii em animais domésticos, silvestres e grupamentos humanos da Amazônia

Prevalence of chloroquine-resistant falciparum malaria in the Brazilian Amazon.

Drug-Resistant Falciparum Malaria among the Mayongong Indians in the Brazilian Amazon

Aspectos epidemiológicos da malária no Amazonas

Diagnóstico sócio-parasito-sanitário da cidade de Nova Olinda do Norte - Amazonas