Ecological distribution of mosquito larvae of the Anopheles punctulatus group on Niolam (Lihir) Island, Papua New Guinea

We surveyed the larval habitats of member,, of the Anopheles punctulatus group of mosquitoes on Niolam (Lihir) Island. Papua New Guinea. Identification of this group was undertaken by polymerase chain reaction-restriction fragment length polymorphism analysis of the amplified internal transcribed spacer unit 2 of rDNA. because morphologic separation of member species is unreliable. The most widespread malaria vector species and their most common larval habitats identified to aid source-reduction programs for malaria control. The most ubiquitous species was An. punctulatus, followed by An. farauti no. 2. then An. farauti s.s. Anopheles punctulatus has increased relative to An.farauti s.l. since the start of development projects on Lihir Island. The most common larval habitats were shallow temporary pools with clay substrate and with plants or floatage. These habitats. mostly encountered alongside poorly drained roads, may be increased by development projects.

Determinants of hepato- and spleno-megaly in Hunan, China: cross-sectional survey data from areas endemic for schistosomiasis

In order to understand the determinants of schistosome-related hepato- and spleno-megaly better, 14 002 subjects aged 3-60 years (59% male; mean age =32 years) were randomly selected from 43 villages, all in Hunan province, China, where schistosomiasis caused by Schistosoma japonicum is endemic. The abdomen of each subject was examined along the mid-sternal (MSL) and mid-clavicular lines, for evidence of current hepato- and/or spleno-megaly, and a questionnaire was used to collect information on the medical history of each individual. Current infections with S. japonicum were detected by stool examination. Almost all (99.8%) of the subjects were ethnically Han by descent and most (77%) were engaged in farming. Although schistosomiasis appeared common (42% of the subjects claiming to have had the disease), only 45% of the subjects said they had received anti-schistosomiasis drugs. Overall, 1982 (14%) of the subjects had S. japonicum infections (as revealed by miracidium-hatching tests and/or Katon Katz smears) when examined and 22% had palpable hepatomegaly (i.e. enlargement of at least 3 cm along the MSL), although only 2.5% had any form of detectable splenomegaly (i.e. a Hackett's grade of at least 1). Multiple logistic regression revealed that male subjects, fishermen, farmers, subjects aged greater than or equal to 25 years, subjects with a history of schistosomiasis, and subjects who had had bloody stools in the previous 2 weeks were all at relatively high risk of hepato- and/or spleno-megaly. In areas moderately endemic for Schistosoma japonicum, occupational exposure and disease history appear to be good predictors of current disease status among older residents. These results reconfirm those reported earlier in the same region.

Habitat use, diet and body size of Heard Island weevils

Habitat use, diet and body-size variation are examined in weevils from Heard Island. with specific attention being given to the Ectemnorhinus viridis species complex. E. viridis shows marked altitudinal variation in body size and vestiture, but there are no consistent associations between body size and diet. nor are there consistent among-individual differences in conventional taxonomic characters. Thus, the status of E. viridis as a single, variable species is maintained. This species occurs from sea level to 600 rn and it feeds on vascular plants and bryophytes. Canonopsis sericeus also feeds on bryophytes and vascular plants and occurs over a narrower altitudinal range. Palirhoeus eatoni is restricted to the surpralittoral zone where it feeds on marine algae and lichens. Bothrometopus brei,is and B. gracilipes both feed on cryptogams, with the former species occurring from sea level to 450 m. and the latter from 50 to 550 m above sea level. In all species, males are smaller than females and there is a size cline such that populations from higher elevations are smaller than those at lower altitudes. This cline is the reverse of that found on the Prince Edward Islands which, unlike Heard Island, lie to the north of the Antarctic Polar Frontal Zone. This difference in body-size clines between weevils on the two island groups is ascribed to the shorter growing season on the colder Heard Island. The information presented here supports previous ideas regarding the evolution of the Ectemnorhinus-group of weevils on the South Indian Ocean Province Islands, although it suggests that subsequent tests of these hypotheses would profit from the inclusion of molecular systematic work.

Cost of malaria control in China: Henan's consolidation programme from community and government perspectives

Objective To assist with strategic planning for the eradication,of malaria in Henan Province, China, which reached the consolidation phase of malaria control in 1992, when only 318 malaria cases were reported, Methods We conducted a prospective two-year study of the costs for Henan's malaria control programme. We used a cost model that could also be applied to other malaria programmes in-mainland China, and analysed the cost of the three components of Henan's malaria programme. suspected malaria case management,, vector surveillance,,and population blood surveys. Primary cost data were collected from the government, and data on suspected malaria patient's were collected in two malaria counties (population 2 093 100). We enlisted the help of 260 village doctors. in six-townships or former communities (population 247 762), and studied all 12 315 reported cases of suspected malaria in catchment areas in 1994 and 1995. Findings The average-annual government investment in malaria control was estimated to be US$ 111 516 (case-management 59%; active blood surveys 25%;vector surveillance 12%; and contingencies and special projects 4%). The average cost (direct and indirect) for-patients seeking-treatment for suspected malaria was US$ 3.48, equivalent,to 10 days' income for rural residents. Each suspected malaria case cost the government an, average of US$ 0.78. Conclusion Further cuts in government funding will increase future costs, when epidemic malaria returns; investment in malaria control should therefore continue at least at current levels,of US$ 0.03 per person a risk.

Stream-bank shade and larval distribution of the Philippine malaria vector Anopheles flavirostris

The principal malaria vector in the Philippines, Anopheles flavirostris (Ludlow) (Diptera: Culicidae), is regarded as 'shade-loving' for its breeding sites, i.e. larval habitats. This long-standing belief, based on circumstantial observations rather than ecological analysis, has guided larval control methods such as 'stream-clearing' or the removal of riparian vegetation, to reduce the local abundance of An. flavirostris . We measured the distribution and abundance of An. flavirostris larvae in relation to canopy vegetation cover along a stream in Quezon Province, the Philippines. Estimates of canopy openness and light measurements were obtained by an approximation method that used simplified assumptions about the sun, and by hemispherical photographs analysed using the program hemiphot(C) . The location of larvae, shade and other landscape features was incorporated into a geographical information system (GIS) analysis. Early larval instars of An. flavirostris were found to be clustered and more often present in shadier sites, whereas abundance was higher in sunnier sites. For later instars, distribution was more evenly dispersed and only weakly related to shade. The best predictor of late-instar larvae was the density of early instars. Distribution and abundance of larvae were related over time (24 days). This pattern indicates favoured areas for oviposition and adult emergence, and may be predictable. Canopy measurements by the approximation method correlated better with larval abundance than hemispherical photography, being economical and practical for field use. Whereas shade or shade-related factors apparently have effects on larval distribution of An. flavirostris , they do not explain it completely. Until more is known about the bionomics of this vector and the efficacy and environmental effects of stream-clearing, we recommend caution in the use of this larval control method.