Pyrimethamine-sulfadoxine treatment of uncomplicated Plasmodium falciparum malaria in Lao PDR.

A 28-day in vivo treatment trial to evaluate the efficacy of pyrimethamine/sulfadoxine (Fansidar, PS) was conducted in 21 Lao patients with uncomplicated Plasmodium falciparum malaria. Sixteen patients (76%) were completely cured with PS without any reappearance of asexual stage parasitemia during the follow-up examination. On the other hand, 5 patients (24%) failed to respond to this trial medication, resulting in recrudescence of asexual stage P. falciparum malaria. PS resistance resulted in higher prevalence of post-treatment gametocytemia, 25% gametocyte carriers among PS sensitive cases versus 75% of the resistant cases. These findings suggest that although the level of PS resistance is still valid for treatment of malaria in the study area of Lao PDR, post-treatment induction of gametocytemia among resistant cases may result an increase in transmission rate of PS resistant falciparum malaria.

A molecular epidemiologic study of point mutations for pyrimethamine-sulfadoxine resistance of Plasmodium falciparum isolates from Lao PDR.

To understand the current condition of pyrimethamine-sulfadoxine (PS) resistant falciparum malaria in Lao PDR, the frequency of point mutations in dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) genes of Plasmodium falciparum were examined in 50 blood samples collected from the patients with P. falciparum infection in Southern Lao PDR. Point mutations in 5 codons of the DHFR gene, which is known to be related to pyrimethamine resistance, were detected in 15 out of the 50 samples (30%). Among the 15 samples, 10 samples showed a double mutation of codons 59 and 108 (Cys59Arg with Ser108Asn). In the remaining 5 samples, an additional mutation was observed in codon 51 (Asn51 lle), providing a triple mutation of codons 51, 59 and 108. On the other hand, point mutations in the 4 codons of DHPS gene related to sulfadoxine resistance were observed only in 2 samples (4.0%), namely in codon 437 (Ala437Gly). Only one sample showed mutations in both DHFR and DHPS genes. From the results, it should be considered that the frequency of PS resistant malaria is still low in Lao PDR. Continuous monitoring for the PS resistant malaria, however, is necessary because of the increasing use of PS in this country.

Field application and evaluation of a rapid immunochromatographic test for detection of Plasmodium falciparum infection among the inhabitants of Lao PDR.

Field application and evaluation of a rapid immunochromatographic test (ICT) for detection of Plasmodium falciparum infection were performed in 13 villages in a southern province of Lao PDR in 1999. More than 2,000 inhabitants, accounting for 61.8% of the total estimated population, were examined. Malaria infection was confirmed in all villages surveyed by ICT and microscopic diagnosis. The positive rates of P. falciparum malaria by microscopy ranged from 9.7% to 59.2% (mean 27.2%), whereas by ICT they were from 11.6% to 64.5% (mean 29.8%). The positive rates by ICT were generally higher in 8 out of 13 villages. However, a significant difference between the positive rates by microscopy and ICT was not observed in all villages. Plasmodium falciparum infection was actually confirmed by microscopy in 84.1% of specimens that tested positive by ICT. The results by ICT were consistent with those of the microscopic diagnosis, the discrepancy of the results was less than 10% (141/2,066). The ICT was falsely-positive in 4.7% and falsely-negative in 2.1% of the test cases. These results showed the efficacy of ICT not only in the diagnosis of the respective cases, but also in the mass-examination in the field.

Entomological surveys of malaria in Khammouane Province, Lao PDR, in 1999 and 2000.

Anopheline mosquitos and their relation to malaria transmission were studied 3 times: in July and August, 1999; in December, 1999; and in August and September, 2000. The studies took place in the malaria endemic villages of Khammouane Province, southeast of Lao PDR. A total of 28 species were collected using human and animal bait. Human bait attracted predominantly Anopheles dirus and An. minimus, which were identified as vectors by the detection of sporozoites by dissection, PCR, and enzyme-linked immunosorbent assays for Plasmodium falciparum and P. vivax. The vectorial capacity of An. dirus was 0.009-0.428, while that of An. minimus was 0.048-0.186. The inoculation rate of An. dirus was 0.052-0.137 (Boualapha; August, 2000). An. nivipes and its sister species, An. philippinensis, were principally zoophilic, although a considerable number of the females were also attracted to human bait in the villages of the paddy field areas. An. philippinensis infected with oocysts of P. vivax was detected in a specimen collected by animal bait. These two species were considered as vectors in Khammouane Province. Four species, An. notanandai, An. sawadwongporni, An. willmori, and An. hodgkini, had not been recored before in Lao PDR. Information is provided on host preference and the nocturnal biting activities of common species and the incidence of malaria in the study areas.

Knowledge and behavior relating to malaria in malaria endemic villages of Khammouane Province, Lao PDR.

In order to provide basic data for evaluation of malaria control measures, a study on the knowledge and behavior of people regarding prevention of malaria was carried out in 8 malaria endemic villages in Khammouane Province of Lao PDR from 1999 to 2000. The total valid questionnaire respondents were 932, with a mean age of 32.3 +/- 14.9. 43.7% of the respondents were illiterate. About 44% of the respondents suffered from malaria in the past. About 55% of the illiterate group slept in mosquito nets, compared to 75.4% for the educated group. About 29% of the illiterate respondents had knowledge of malaria transmission by mosquito bites, compared to 48.8% for the educated groups. Out of 167 non-impregnated mosquito nets examined in two villages, 13 were in bad condition having holes or leaks and 39 female mosquitos including Anopheles spp were collected in these nets by early morning catches. Knowledge of malaria and behavior in relation to the prevention of malaria were significantly related to educational level. Health education as well as general education must be taken into account for communities in malaria endemic areas to become more involved in malaria control strategies.

An ecological survey of dengue vector mosquitos in central Lao PDR.

An ecological survey of dengue vector mosquitos was carried out in June 2000 in central Lao PDR. Two areas in Khammouane Province, Nongbok and Thakhek, were selected for the survey. Of the 7 mosquito species identified, Aedes aegypti was dominant in both study areas. The container index for Ae. aegypti in Nongbok was 51.8% and was significantly higher than that of Thakhek (40.2%); moreover, significant differences between the study areas were found with records to containers and to the conditions surrounding the houses. The key containers in Nongbok were water jars, whereas drums or small or discarded containers had the highest occurrence rate of Ae. aegypti in Thakhek. Mesocyclops aspericornis was found in large water jars and cement water tanks; no Aedes larvae were found at these sites. Strategy to control dengue vectors in the study areas was discussed.

Studies on prevalence of strongyloides infection in Holambra and Maceio, Brazil, by the agar plate faecal culture method

Foi feito levantamento sobre a prevalencia da infeccao por Strongyloides stercoralis em tres areas do Brasil, atraves do desenvolvimento de metodo de cultura de fezes (cultura em placa de agar). A infeccao por Strongyloides foi confirmada em 11,3 por cento de 432 pacientes examinados. A eficacia do diagnostico pela cultura em placa de agar foi de 93,9 por cento comparado com apenas 28,5 por cento e 26,5 por cento pelo metodo de Harada-Mori de cultura em papel de filtro e metodo de concentracao de fezes, quando amostras de fezes foram examinadas simultaneamente por estes tres metodos. Entre as 49 amostras positivas, aproximadamente 60 por cento foram confirmadas como positivas somente pela cultura em placa de agar. Estes resultados indicam que a cultura em placa de agar e um novo metodo sensivel para o diagnostico correto da infeccao cronica pelo Strongyloides

Prevalence of intestinal parasitic infection in five farms in Holambra, Sao Paulo, Brazil

Uma pesquisa coproparasitologica foi realizada em 222 habitantes de cinco fazendas de Holambra, localizada a 30 Km ao norte de Campinas, SP, Brasil, em outubro de 1992. Aproximadamente 70 por cento dos habitantes apresentaram pelo menos um tipo de parasitose intestinal. O indice de positividade das 6 especies de helmintos e de 7 protozoarios na populacao foi o seguinte: Ascaris lumbricoides (5,4 por cento ); Trichuris trichiura (8,6 por cento ); Necator americanus (19,8 por cento ); Strongyloides stercoralis (10,4 por cento ); Enterobius vermiculares (1,4 por cento ); Hymenolepis nana (0,9 por cento ); Entamoeba histolytica (3,2 por cento ); E. hartmanni (2,7 por cento); E. coli (9,9 por cento ); Endolimax nana (14,0 por cento ); Iodamoeba butschlii (2,3 por cento ); Giardia lamblia (10,4 por cento ); Blastocytis hominis (37,4 por cento ). O indice de positividade para infeccao por helmintos foi aparentemente maior na populacao mais jovem (menores de 16 anos) do que no grupo de populacao com idades acima de 16 anos, ao contrario do indice de infeccao pelos protozoarios que foi mais elevado na populacao adulta. Utilizando um novo e sensivel metodo atraves de cultura em agar, encontrou-se um indice de infeccao de 10,4 por cento para strongyloides sp.

Serodiagnosis of strongyloidiasis: the application and significance

O diagnostico parasitologico baseado no exame de fezes e muitas vezes dificil, principalmente nos casos de infeccoes cronicas ou leves pelo S. stercoralis. Mesmo utilizando o mais novo e sensivel metodo (cultura em placas de agar) e essencial examinar repetidamente as amostras fecais, para um diagnostico correto. E importante ressaltar tambem que o resultado negativo nao indica de modo inequivoco a ausencia da infeccao. Por outro lado, varios sorologicos recentementes desenvolvidos para estrongiloidiase tem provado a sua eficacia quando usados para complementar exames parasitologicos. Para demonstrar infeccao por Strongyloides desenvolvemos dois tipos de testes sorologicos - ELISA e GPAT - e, com base em nossos recentes estudos, apresentamos uma opiniao sobre sua possivel aplicacao para screening em massa, estudos epidemiologicos e avaliacao pos-tratamento de estrongiloidiases.

Gelatin particle indirect agglutination test for serodiagnosis of schistosomiasis: comparative study with enzyme-linked immunosorbent assay

Um novo teste sorologico, o teste de aglutinacao com particulas de gelatina (TAPG), foi utilizado para o diagnostico sorologico de esquistossomose mansonica. Esta tecnica mostra que a sensibilidade (90,6 por cento) e especificidade (97,8 por cento) chegam proximas do teste de enzima imunoensaio. O TAPG pode ser facil e rapidamente realizado sem equipamentos especializados usando particulas liofilizadas sensibilizadas com o antigeno. O teste mostrou ser tambem util em condicoes de campo para triagem em massa da infeccao pelo Schistosoma mansoni.