Possibility of false-positive detection for sporozoites in mosquitos (Diptera: Culicidae) by nested polymerase chain reaction using Plasmodium yoelii genomic DNA.

Anopheles stephensi Liston and An. saperoi Bohart and Ingram infected with the rodent malaria parasite Plasmodium yoelii nigeriense. They were examined 12 and 19 days after blood feeding for sporozoites in head with anterior thorax (HT) and oocysts in abdomen with posterior thorax (AB) by light microscopy and by the nested polymerase chain reaction (nested PCR-based on the amplification of the sequences of the small subunit ribosomal RNA gene). The detection rate of parasite DNA by nested PCR in HT samples 12 days after blood feeding was similar to that by microscopic method. However, in HT samples 19 days after blood feeding, the rate by the PCR method was higher than that by the microscopic method. The incidence of sporozoites in salivary glands of infected mosquitos for 12 days after blood sucking was examined by the PCR method. Parasite DNA in HT of Aedes albopictus Skuse (a non vector for the rodent malaria) as well as An. stephensi and An. saperoi was detected for up to 4 days after feeding on mouse with the rodent malaria parasites. The results indicate that when the PCR method is used for detection of sporozoites of human malaria in mosquitos collected in the field, there are possibilities of including false-positive data for mosquitos that have just or recently fed on human blood infected with malaria (erythrocytic form).

Community control studies on Strongyloides infection in a model island of Okinawa, Japan.

The community control program for Strongyloides infection was conducted by fecal examination and subsequent treatment of the population on a model island (Kume Island) in Okinawa, Japan, for 5 years from 1993 to 1997. More than 1,200 persons, accounting for 17% to 20% of the persons subjected, received fecal examinations each year. The positive rate in 1993 was found to be 9.7% (133/1,374). The positive rate decreased to 6.5% (95/1,468) in 1994, then 4.8% (60/1,245) in 1995, 2.2% (27/1,225) in 1996 and 2.7% (33/1,217) in 1997 through treatment with albendazole or ivermectin on the positive persons detected each year. Among the positive persons detected after operation of the control program, more than 70% were newly detected persons who did not receive an examination in the previous year or were falsely-negative in the previous examination. The low enforcement of procuring fecal examinations, as well as low sensitivity of fecal examination, might have had an effect on the relatively gradual decrease in the prevalence rate, in spite of the high efficacy of the treatment. The results indicate that continuation of the control program for several years is needed to effectively reduce the prevalence of the parasitic infection in the community.

Comparative studies on the efficacy of three anthelminthics on treatment of human strongyloidiasis in Okinawa, Japan.

A study was undertaken to compare the efficacy of three drugs in the treatment of uncomplicated strongyloidiasis in Okinawa, Japan. Two hundred and eleven patients with confirmed Strongyloides stercoralis infection were given either ivermectin, 6 mg in a single dose, albendazole, 400 mg/day for 3 days or pyrvinium pamoate, 5 mg/kg/day for 3 days. For each treatment, the same regimen was repeated once 2 weeks later. Efficacy was evaluated at 2 weeks, 6 months and 12 months after the second course of treatment. Each follow-up examination included a parasitological examination of z stool specimens, using the agar-plate culture method. Coprological cure was obtained in 65 of the 67 patients treated with ivermectin (97.0%), in 65 of the 84 patients treated with albendazole (77.4%) and only in 14 of the 60 patients who were given pyrvinium pamoate (23.3%). The cure rates were lower in males and in the patients with concurrent HTLV-1 infection. An epidemiological feature of Strongyloides infection in recent Okinawa might allow workers to evaluate the exact efficacy of the treatment for an extended period, over a year, without the possibility of reinfection from the environment.

An epidemiological study on Opisthorchis viverrini infection in Lao villages.

The prevalence of liver fluke, Opisthorchis viverrini, infection in rural and urban communities was studied in Khammouane Province in Lao PDR. The infection was the commonest among the villagers examined, showing the positive rates of 52.9% and 55.0% in two rural communities and 60.7% in an urban community, respectively. The infection rate reached up to 20% or more within 4 years after birth and increased with age to a plateau in the age group over 20 years. The highest prevalence rate was over 80% in the age group of 35-54 years. The age-related patterns of infection in males and females were almost the same, although there were some sex-related differences by village and by age group. Infection with Opisthorchis viverrini appears to be a serious public health problem strongly associated with the frequent eating habit of raw fish in low land Laos.

Plasmodium ovale infections detected by PCR assay in Lao PDR.

Plasmodium ovate infection was demonstrated in 5 out of 143 inhabitants in a village in Lao PDR by blood microscopy and PCR assay. Although the specimen confirmed to be positive for P. ovale by microscopical examination was only one, the target sequences in the 18S rRNA genes of malaria parasite detected in all of the five cases were consisted with those of P. ovale by the PCR assay. This is the first report concerning the presence of so many cases with P. ovale infection in Lao PDR.

An epidemiological survey on intestinal parasite infection in Khammouane Province, Lao PDR, with special reference to Strongyloides infection.

To estimate the current prevalence of intestinal helminth infection in Lao PDR, a parasitological survey was conducted in three villages in Khammouane Province in December 1996, with special reference to Strongyloides infection. A total of 669 fecal samples were collected in the villages and examined by agar-plate culture method and Kato-Katz thick smear method. Intestinal helminths were demonstrated in 82% of the samples as follows: Ascaris lumbricoides (30.5%), Trichuris trichiura (23.7%), hookworm (28.8%), Strongyloides stercoralis (19.0%), Enterobius vermicuralis (3.4%), Opisthorchis viverrini (56.7%) and Taenia sp (3.0%). The infection rates of S. stercoralis were 27.5% and 18.4% in two rural villages, but only 9.4% in an urban village. The highest prevalence rate of Strongyloides infection was obtained in the age group from 20 to 29 years old, although the infection rate already reached 10% in the age group under 10 years old. The prevalence was consistently higher in male subject than females in almost all age groups.

Current status of malaria infection in a southeastern province of Lao PDR.

In Khammouane, a southeastern province in Lao PDR, active case detection (ACD) surveys for malaria infection on the villagers in three villages were conducted four times from December, 1995 to August, 1996. The malaria infection was demonstrated in 5.3-10.5% of the villagers throughout the year in 2 villages located in mountainous forest, but the infection was rarely observed in the other village located in the plain along the Mekong River, in which only 4 malaria cases were detected in August, 1996. Although the positive rate of malaria parasites among the villagers was not so significantly different in the rainy season compared with the dry season, the intensity of infections (ie parasitemia) was significantly higher in the rainy season. More than 90% of the positive villagers were children under 15 years old. Most infections were due to Plasmodium falciparum.

Collection of anopheline mosquitos in three villages endemic for malaria in Khammouane, Lao PDR.

Anopheline mosquito collections were made during the months of May and June (dry season) and August (rainy season), 1996 at villages, Nakham, Namdik and Hinboon Neua in Khammouane Province. Larval collections were also made in 3 slow running streams around Nakham villages in May 1996. Altogether, 3,549 adult females consisting 19 Anopheles species were collected by 3 nights of human and 6 animal bait traps and 3 resting collections. Among them, Anopheles vagus (19.75%), An. philippinensis (15.02%), An. nivipes (11.55%), An. pallidus (11.27%), An. peditaeniatus (8.34%), An. kochi (8.00%) and An. barbirostris (7.27%) were predominant species. The immatures of An. barbirostris, An. minimus, An. maculatus sensu lato, and An. culicifacies were found in the streams of Nakham. It is noteworthy that An. minimus, An. dirus and An. maculatus sensu lato, which are well known malaria vectors in Thailand, were recorded for the first time in this area.

Prevalence of intestinal parasitic infection among children in two villages in Lao PDR.

The prevalence of intestinal parasitic infection among 128 children under 15 years old in two villages in Khammouane Province, southeastern Lao PDR, was investigated. Overall prevalence of helminth infection was 77.3%; the prevalence was 64.8% in children under 6 years, 88.5% in those aged 6-10 years and 81.8% in the age group above 11 years. The prevalent helminths found in the subjects were Ascaris lumbricoides (48.4%), Trichuris trichiura (43.8%), hookworm (37.5%) and Opisthorchis viverrini (37.5%). Intestinal protozoan infection was demonstrated in 14.1%; Giardia lamblia was the most prevalent (8.6%) protozoan species.

Tamanho de primeira maturaçäo sexual do Schizodon knerii e do Leporinus piau (Teleostei, Anostomidae) na represa de Três Marias, MG / First sexual maturation of Schizodon knerii and of Leporinus piau (Teleostei, Anostomidae) from Três Marias reservoir, MG - Brazil

Determinaram-se os tamanhos de primeira maturaçäo sexual (L50) para S. knerii, piau-branco e para L. piau, piau-gordura. Diferenciaram-se peixes juvenis de peixes adultos por critérios microscópicos. O comprimento padräo correspondente à primeira maturaçäo sexual (L50) foi estimado em: S. knerii 14,5 cm para fêmeas e 2,3 cm para machos; L. piau 10,2 cm para fêmeas e 9,6 cm para machos. Todos os peixes estavam aptos a reproduzirem-se (L100) a partir de: S. knerii 17,5cm para fêmeas e 14,7cm para machos; L. piau 12,0cm para fêmeas e 10,8cm para machos. O coeficiente de correlaçäo (r) entre frequência de adultos e classes de comprimento padräo foi superior a 0,97 em cada caso indicando eficiência do método

Hipofisaçäo do peixe Prochilodus affinis da bacia do Rio Säo Francisco / Hypophysation of the fish Prochilodus affinis from the Rio Sao Francisco basin, Brazil

P. affinis é um peixa da bacia do Rio Säo Francisco de importância na pesca comercial. Ele é iliófago, de piracema e pode atingir cerca de 6 kg de peso corporal (PC). Os dados aqui apresentados referem-se à hipofisaçäo de 154 fêmeas e 225 machos na Estaçäo de Hidrobiologia e Piscicultura de Três Marias, CODEVASF, Três Marias, MG, Brasil. Utilizou-se extrato bruto de hipófise de carpa (EBHC) em duas doses para as fêmeas (0,8 mais ou menos 0,2 mg de EBHC/kg de PC e 5,7 mais ou menos 0,4 mg de EBHC/kg de PC), com intervalo de 16,5 mais ou menos 2,3 h entre doses, e uma dose para os machos (2,8 mais ou menos 0,4 mg de EBHC/kg de PC). Cerca de 76 por cento das fêmeas tratadas liberaram ovos viáveis a 219 mais ou menos 12 horas-grau, à temperatura da água de 23,9 mais ou menos 0,8§C. Os ovos eram livres, demersais e de cor cinza. Eles mediram 1,4 mais ou menos 0,1 mm de diâmetro e aumentaram cerca 9,8 vezes seu volume após a hidrataçäo. A razäo entre peso da ova: peso corporal = 22,1 mais ou menos 4,1 por cento, o número de ovos/g de ova = 1222 mais ou menos 119 e a taxa de fertilizaçäo (estimada por ocasiäo do fechamento do blastóporo) = 71 mais ou menos 16 por cento. A fertilidade inicial relativa (número de ovos extruídos/kg PC) = 269,9 x 103 mais ou menos 53,7 x 10 ao cubo e a fertilidade final relativa (número de ovos viáveis por ocasiäo do fechamento do blastóporo/kg PC) = 201,3 x 10 elevado ao cubo mais ou menos 52,9 x 10 elevado ao cubo. As relaçöes entre PC e fertilidades inicial (FI) e final (FF) foram expressas, respectivamente, por: FI = 33.085 + 227.231 PC e FF = 25.852 + 169.987 PC. Quando estes valores de FI, FF e PC foram acumulados (a), as equaçöes foram: Fla = 162.066 + 269.042 PCa e FFa = 95.567 + 204.173 PCa

Hipofisaçäo do peixe anostomídeo piau-branco Schizodon knerii da bacia do Rio Säo Francisco / Hypophysation of the anostomid fish white-piau Schizodon knerii from the Rio Sao Francisco basin

Schizodon knerii é um peixe importante na pesca profissional na represa de Três Marias onde ele pode atingir cerca de 1,2kg de peso corporal (PC). Quatorze fêmeas e 14 machos foram hipofisados com extrato bruto de hipófise de carpa (EBHC). As fêmeas receberam 2 doses de EBHC (1a. dose = 0,7 mais ou menos 0,2mg de EBHC/kg de PC; segunda dose = 5,6 mais ou menos 0,5mg de EBHC/kg de PC; intervalo entre doses = 18,6 mais ou menos 0,5h) e os machos receberam dose única de EBHC (2,6 mais ou menos 0,2 mg de EBHC/kg de PC). Nove fêmeas produziram ovos viáveis sob massagem abdominal 210 mais ou menos 7,9 horas-grau após a 2a. dose, estando a temperatura da água a 23,9 mais ou menos 1§C. Os ovos eram opacos, cinza ou marrom-claro e adesivos. Eles mediram 1,1 mais ou menos 0,1 mm antes de se hidratarem e 1,3 mais ou menos 0,1 mm após hidrataçäo. A razäo peso da ova: peso corporal (porcentagem) = 8,5 mais ou menos 1,4, o número de ovos/g de ova = 2448 mais ou menos 59 e a taxa de fertilizaçäo (estimada por ocasiäo do fechamento do blastóporo, em porcentagem) = 69 mais ou menos 9,4. Fertilidade inicial (i.e., o número de ovos extruídos x 10 elevado ao cubo) = 118,9 mais ou menos 33,5 enquanto que fertilidade final (i.e., o número de ovos viáveis por ocasiäo do fechamento do blastóporo x 10 elevado ao cubo) = 82,8 mais ou menos 28,6. As relaçöes entre PC e fertilidade inicial (FI) e final (FF) foram expressas, respectivamente, por: FI = -72010 + 340 PC (r ao quadrado = .88; n=9) e FF = -71442 + 274 PC (r ao quadrado = .79; n=9)

Aspectos reprodutivos da piranha, Pygocentrus piraya (Teleostei, Characiformes), espécie nativa da bacia do Rio Säo Francisco / Reproductive aspects of piranha Pygocentrus piraya (Teleostei, Characiformes), a native species from the Rio Sao Francisco basin, Brazil

Analisaram-se histologicamente gônadas de 305 exemplares de Pygocentrus piraya, capturados no reservatório de Três Marias, MG, no período de julho/85 a junho/86. Determinaram-se os estádios de desenvolvimento dos ovócitos e das gônadas. De desova parcelada, aparentemente essa espécie de piranha reproduz-se no próprio reservatório, durante os meses de janeiro a abril, quando o nível de água está em elevaçäo. Existem indicaçöes que os machos acham-se aptos a reproduzirem-se durante todo o ano. Näo foram observados machos esgotados

Aspectos da biologia reprodutiva da corvina Pachyurus squamipinnis Agassiz, 1829 (Teleostei, Sciaenidae) na Represa de Três Marias, MG / Reproductive biological aspects of the corvina Pachyurus squamipinnis Agassiz, 1829 (Teleostei, Sciaenidae) in the Tres Marias reservoir, MG, Brazil

Gônadas de 599 exemplares de P. squamipinnis, capturados na represa de Três Marias no período de julho/85 a junho/86, foram analisadas por métodos histológicos. A maioria dos peixes encontravam-se em repouso. Machos em maturaçäo foram observados durante todo o ano. Somente nove fêmeas em maturaçäo avançada foram registradas e fêmeas desovadas näo foram capturadas. Entretanto, há indicaçöes de que a espécie completa seu ciclo reprodutivo na represa. O tamanho de primeira maturaçäo sexual (L50) de fêmeas foi estimado em 21,4cm de comprimento padräo (CP). Todas as fêmeas estäo aptas a reproduzirem-se (L100) a partir de 26,5cm CP

Ciclo reprodutivo do tucunaré Cichla ocellaris (Schneider, 1801) na represa de Três Marias, MG / Reproductive cycle of tucunare Cichla ocellaris (Schneider, 1801) in the Tres Marias reservoir, MG, Brazil

Pela análise microscópica de gônadas constatou-se que a desova de C. ocellaris é do tipo parcelada e que peixe em estádio de maturaçäo ocorrem durante todo o ano. Registrou-se maior frequência de fêmeas desovadas no mêes de janeiro, quando a precipitaçäo pluviométrica na regiäo de Três Marias é alta e o nível de água da represa começa a subir

Angiostrongylus cantonensis infection in Ampullarius canaliculatus (Lamarck) in Kyushu, Japan.

Ampullarius canaliculatus is a large fresh-water snail of which the original habitat is said to be Argentina. Recently, the snail which grew wild has propagated in various parts of Japan, and is causing damage to aquatic plants by feeding on them. The present study was performed to find out whether the snail can be a suitable intermediate host for Angiostrongylus cantonensis. Natural infection with A. cantonensis was confirmed in the snails collected from 5 different places in 4 hamlets in Okinawa and in those from Ishigaki Island. All snails experimentally infected with first-stage larvae of the parasite showed second-stage and third-stage larvae developing at the time of examination later on. Thus, A. canaliculatus is a suitable intermediate host for A. cantonensis, and, if eaten raw, it can be a potential source of human infection with eosinophilic meningoencephalitis in the endemic areas.

Studies on eosinophilic meningitis and meningoencephalitis caused by Angiostrongylus cantonensis in Japan.

Twenty cases of eosinophilic meningitis or meningoencephalitis suspected of being angiostrongyliasis were recognized in Japan, including 16 cases in Okinawa Prefecture. Among the cases, there was only one proven case in Okinawa. The disease evenly occurred throughout all seasons. Both sexes were equally affected, but 17 cases (more than 80%) occurred among adults. Intentional ingestion of various mollusks and fresh livers of toads for therapeutic reasons were interestingly responsible for 7 cases. The immunological diagnosis was successfully carried out on 9 cases. It was discussed that the cultural and ethnic backgrounds with different ways of life and eating habits determine the prevalence of the disease, and clinical and epidemiological features of the disease among different ethnic groups and geographic areas.