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).

The relationship between anthropometric indicators of nutritional status and malaria infection among youths in Khammouane Province, Lao PDR.

We assessed anthropometric indicators of the nutritional status among children and adolescents in Khammouane Province in the Lao PDR and examined the relation between malnutrition and malaria infection. The survey was conducted from July to August 1999 using a sample of 309 youths aged 2 to 18 years. Malnutrition was categorized as stunting (below -2 Z scores height-for-age) and wasting (below -2 Z scores weight-for-height). The prevalence of stunting and wasting were 45.1% and 9.2%, respectively, which were classified by WHO as "very high" prevalence. Compared with the results of previous national surveys in Lao PDR, similar prevalence was shown. The prevalence of wasting in youths with P. falciparum infection was 17%, significantly higher than those of not infected (4%). On the other hand, P. vivax infection was not associated with any indicators of malnutrition. In conclusion, this study showed that the nutritional status in youths was poor and P. falciparum infection was associated with acute malnutrition.

Breeding habitats of Aedes aegypti (L) and Aedes. albopictus (Skuse) in villages of Barru, South Sulawesi, Indonesia.

The breeding habitats of the dengue vector, Aedes aegypti and Aedes albopictus, were studied using larval collection method inside and outside houses in 6 villages of Barru, South Sulawesi, Indonesia from July 1994 to August 1995. Aedes aegypti was the dominant species, being abundant indoors especially in the coastal areas. Aedes albopictus was breeding primarily in outdoor containers in the hill and mountain areas. Earthen jar was the most common breeding habitat of Aedes aegypti in all villages surveyed. Drum can was the most common outdoor breeding habitat of Aedes albopictus in the hill and mountain areas. The high Breteau indices of Aedes aegypti and Aedes albopictus suggests that these species may play an important role in the transmission of dengue hemorrhagic fever in Barru where epidemics of the fever occur occasionally.

Historical review of mosquito control as a component of malaria eradication program in the Ryukyu Archipelago.

In the Ryukyu Archipelago, where malaria used to be endemic, eradication of the disease was achieved by the year 1962, as a consequential effect of a planned malaria eradication program in the area. This achievement was facilitated by concerted efforts in controlling vector mosquitos and treatment of all detected and presumptive cases of malaria infections. Anopheles minimus Theobald and An. sinensis Wiedemann were common in all areas endemic for malaria. Knowledge of the biology and bionomics of the mosquitos in malaria endemic areas formed the basis for formulating strategies for the control of vectors and subsequent surveillance activities. Insecticide residual spray, larvivorous fishes and environmental management were the basic strategies for vector control. The whole program was augmented by an active community participation in all eradication activities.

Age structure of Anopheles subpictus (Diptera:Culicidae) collected by a light trap in Halmahela, Indonesia.

Age structure of Anopheles subpictus Grassi was studied at a Halmahela village, Indonesia. Ovary development of females reared with 2% sugar solution after emergence ceased at Stage I and their ovary size remained small (mean length x width = 0.68 x 0.18 mm). Females with such small ovaries occupied 21.2% of unfed Stage I females in cattle-bait samples. The remaining unfed Stage I or II females had cleary larger ovaries (mean 1.17 x 0.39 mm). Unfed Stage I or II females collected by the outdoor light trap all had large ovaries (mean 1.42 x 0.34 mm) irrespective of stages and parity. The parous rate of unfed stage I or II females collected by the light trap (86.6%) was significantly higher than that of cattle-bait samples (69.6%). Feasibility of using outdoor light trapping in malaria entomology was discussed.

Prevalence of intestinal helminthic infections in Kao District, north Halmahera, Indonesia.

A parasitological survey was conducted on the inhabitants of six villages of Kao District, Halmahera Island, North Maluku, Indonesia, in July 1993. A total of 422 fecal samples were examined by using Kato-Katz thick smear, modified Harada-Mori culture and formalin ether concentration techniques. Seven nematode species, ie Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis, Enterobius vermicularis and unidentified rhabditoids of free-living nature, were detected. Trematode and cestode infection was not proven. Necator americanus was the predominant species of hookworm. Soil-transmitted nematode infections were highly prevalent. Among the young inhabitants aged less than 15, positive rates of Ascaris, Trichuris and hookworm infections were 32.7, 52.7 and 68.6%, respectively. Among the people aged 15 or more, the positive rate for hookworm (85.9%) was much higher than that for Ascaris and Trichuris (13.5 and 40.5%, respectively). Egg count revealed that more than 90% of inhabitants with Trichuris or hookworm had light infections. The latrines in the surveyed area seemed to have only limited effects on the improvement of the parasitological status because the prevalence of Trichuris infections was much higher in a village where most houses were provided with latrines. These conflicting conditions were considered to have been caused by many factors including the inadequate structure of the latrines.

Intestinal parasitic infections in Campalagian district, south Sulawesi, Indonesia.

Intestinal parasitic infections were surveyed in the inhabitants of 3 coastal and 2 inland villages of Campalagian District, South Sulawesi, Indonesia, in July 1992. A total of 398 fecal samples were examined by using Kato-Katz thick smear, Harada-Mori culture and agar-plate culture techniques. Protozoan cysts were examined by formalin ether concentration technique on 380 fecal samples. Soil-transmitted helminth infections were highly prevalent with the overall positive rates as follows: Ascaris lumbricoides 25.3%, Trichuris trichiura 59.3%, hookworm 68.3% and Strongyloides stercoralis 2.3%. Eight species of protozoan were detected with the overall prevalence as follows: Entamoeba histolytica 10.9%, E. hartmanni 16.3%, E. coli 31.9%, Endolimax nana 12.5%, Iodamoeba buetschlii 5.4%, Giardia lamblia 4.6%, Chilomastix mesnili 0.8% and Blastocystis hominis 18.0%. In the inland villages, prevalence of hookworm infection was higher than Ascaris and Trichuris infections, while in the coastal villages Trichuris infection was predominant. Egg count revealed that the infection level was light in most of the hookworm and Trichuris carriers. Prevalence of lavatories among houses appeared to be inversely proportional to the prevalence of hookworm infection. Meanwhile, the incomplete structure of the lavatories might result in contamination of environment with Ascaris and Trichuris eggs. Harada-Mori culture was the most efficient method in the detection of hookworm infection compared to other techniques. Both Necator americanus and Ancylostoma duodenale were found in all villages, but the former was the predominant species. An adult pinworm was detected by agar-plate culture of feces. Two types of pinworm males, corresponding to Enterobius vermicularis and E. gregorii, were observed.

Intestinal parasitic infections in Likupang, North Sulawesi, Indonesia.

A parasitological survey was conducted on the inhabitants of 6 villages of Likupang, Minahasa Peninsula, North Sulawesi, Indonesia, in August 1991. A total of 419 fecal samples were examined by using direct smear, flotation, formalin ether concentration, Harada-Mori culture and agar-plate culture techniques. Five nematode and 7 protozoan parasites were detected, while trematode and cestode infection was not observed. Soil-transmitted nematode infections were predominant. Among the younger inhabitants aged less than 15, positive rates of Ascaris, Trichuris and hookworm infections were almost same, namely 45.7, 45.3 and 47.7%, respectively. Among the elder people aged 15 or more, positive rate of hookworm infection (89.4%) was much higher than Ascaris and Trichuris infections (19.3 and 26.1%, respectively). Village to village differences in parasite prevalence, probably due to socio-economic and sanitary-environmental differences were observed. Both Necator americanus and Ancylostoma duodenale were detected. The agar-plate culture was proved to be an efficient method for detection of hookworm as well as Strongyloides stercoralis.