The mosquito Anopheles (Cellia) oreios sp. n., formerly species 6 of the Australasian Anopheles farauti complex, and a critical review of its biology and relation to disease

Species 6 of the Australasian Anopheles farauti sibling species complex (Diptera: Culicidae) is described and formally named Anopheles oreios Bangs & Harbach, sp. n. Adult, pupal and fourth-instar larval specimens collected in the Baliem Valley, Papua Province, Indonesia, are characterized and compared with those of Anopheles farauti, Anopheles hinesorum, Anopheles irenicus and Anopheles torresiensis (formerly informally denoted as species 1, 2, 7 and 3, respectively). The variable wings of adult females, the male genitalia, the pupa and the fourth-instar larva of An. oreios are illustrated and DNA sequence data are included for regions coding for sections of the mitochondrial COI and COII genes. The biology of An. oreios and its relation to malaria transmission are discussed in detail and contrasted with the biology and disease relations of some members of the An. farauti and Anopheles punctulatus sibling species complexes.

Field evaluations of disposable sticky lures for surveillance of Aedes aegypti (Stegomyia aegypti) and Culex quinquefasciatus in Jakarta

From December 1997 to April 1998, disposable sticky lures (1608 lure days) were trialled in homes in north Jakarta, Indonesia as surveillance tools for Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae) and Culex quinquefasciatus (Diptera: Culicidae), referenced to indoor resting adult collections (92 × 10 min). The lures collected 89.4% of the total of 1339 Ae. aegypti and 92.1% of the total of 1272 Cx. quinquefasciatus collected by all methods. Because there were no significant differences with respect to numbers collected in bedrooms, living rooms and kitchens, bedrooms were selected for subsequent trials for reasons of convenience. The main trials involved a replicated complete block design with L-lysine and sodium carbonate. Lures without attractant or with four different dilutions of L-lysine collected 3.4-8.5 times more Ae. aegypti and 4.2-8.1 times more Cx. quinquefasciatus than were collected by mouth aspirator. Lures with or without dilutions of sodium carbonate collected 2.7-5.0 times more Ae. aegypti and 1.8-4.2 times more Cx. quinquefasciatus than aspirator collections. The precision associated with catches of sticky lures was better than that for aspirator collections. Although olfactants generally improved the numbers of mosquitoes collected, the differences in catch between lures with and without attractants were usually non-significant. Any deficit in catch may be offset by increasing the surveillance period to ≥30 days to detect all four dengue serotypes from infected mosquitoes.

Onset of clinical immunity toPlasmodium falciparumamong Javanese migrants to Indonesian Papua

Onset of clinical immunity to Plasmodium falciparum occurred among Javanese migrants to Indonesian Papua. Surveillance of the 243 migrants investigated began on the day of their arrival in Indonesian Papua and continued for 33 months. Asexual parasitaemia without fever constituted objective evidence of clinical immunity. Compared with first infection, the odds ratio (OR) for not having fever at the fourth infection within 24 months was 3.2 [95% confidence interval (CI)=1.03-10.2; P=0.02]. The corresponding OR with fewer infections within 24 months was not distinguishable from 1.0. The level of the fourth parasitaemia within 24 months (N=58) was classified as 'high' or 'low' in relation to the median count at first infection (840 parasites/microl; N=187). Fourth parasitaemias that were low-but not those that were high (OR=1.8; CI=0.6-5.4; P=0.35)-were associated with dramatic protection from fever (OR=31; CI=3.5-1348; P=0.0001). Among the adult subjects, the risk of fever with low parasitaemia was significantly higher at the first infection than at the fourth (OR=12.6; CI=1.7-530; P=0.005), indicating the development of clinical immunity. A similar but less marked pattern appeared among the children investigated (OR=6.5; CI=0.8-285; P=0.06).

Mitochondrial diversity of Musca domestica housefly populations in the Asian and western Pacific biogeographical regions

Houseflies (Musca domestica L., Diptera: Muscidae) are cosmopolitan, colonizing, and eusynanthropic. Their distribution in the Malaysian archipelago provides an opportunity to study successive waves of colonization and extinction during the Pleistocene and Recent epochs. We scored single-strand conformation polymorphisms (SSCPs) at 16S2 and COII mitochondrial loci in 47 housefly samples from the Australian, Austro-Malayan, Indo-Malayan, Manchurian and Indo-Chinese subregions of Wallace's zoogeographical classification. We discuss the results in light of the Pleistocene vs. post-Pleistocene dispersal and faunal exchange in the Asia-Pacific area. Fourteen haplotypes were detected, of which 10 were confined to a single subregion. No haplotype was ubiquitous and only one was found in four subregions. Population diversity, HS, was greatest in the Indo-Malayan (0.36) and heterogeneous among subregions. The mean subregional diversity was 0.21 +/- 0.03, representing the probability that two randomly chosen flies, from any subregion, had different haplotypes. The hierarchical partition of diversity indicated restricted maternal gene flow among subregions (GRT = 0.60, Nm approximately 0.32). These results suggest long-standing genetic isolation of houseflies in the Malaysian archipelago and support the hypothesis that they dispersed widely during the Pleistocene. Haplotypes common among mainland populations but shared with island groups in low frequencies (<1%) indicate surprisingly little recent gene flow.

Malaria in a cohort of Javanese migrants to Indonesian Papua

The epidemiology of infection by Plasmodium falciparum and P. vivax was investigated among Javanese migrants to an endemic region of Papua, Indonesia. A cohort of 243 migrants from Java was followed for malaria in a new settlement village in the endemic Armopa area of north-eastern Papua, beginning on the day each migrant arrived in the village. The subjects were monitored during home visits (three/week) and by the twice-monthly production of bloodsmears that were checked for malarial parasites. At the end of 33 months, 159 (65%) of the subjects remained under follow-up. The prevalence of parasitaemia in the village declined from 16% among those already living there when the study began in August 1996, to 5% when the study finished in June 1999. Over this period, 596 infections by P. falciparum and 723 by P. vivax occurred in the cohort, 22 and 27 of the subjects each experiencing at least six infections by P. falciparum and P. vivax, respectively. The incidence of malarial infection was higher during the first and second years post-migration (3.2 and 2.7 infections/person-year) than during the third (1.2 infections/person-year). Although the geometric mean parasite counts for P. falciparum increased over time (1209, 1478, and 1830 parasites/microl in the first, second and third years, respectively), the corresponding values for P. vivax (497, 535 and 490 parasites/microl) showed no such trend. Only one of the nine subjects who developed severe malaria (requiring intravenous quinine therapy) was a child, giving an odds ratio for a case of severe malaria being in an adult of 6.1 (P=0.08).

Primary infection by Plasmodium falciparum or P. vivax in a cohort of Javanese migrants to Indonesian Papua

The clinical and parasitological characteristics of the first naturally acquired malarial infection have rarely been documented in humans. When 243 migrants from non-endemic Java were followed from the day of their arrival in Indonesian Papua, 217 (89%) were found to become infected with Plasmodium falciparum and/or P. vivax before they were lost to follow-up. The incidence of malarial infection in the children investigated (who were aged 6-10 years) was indistinguishable from that in the adults (aged >20 years), with 1.10 and 1.14 P. falciparum infections/person-year (relative risk=0.97; 95% confidence interval=0.72-1.29) and 1.47 and 1.49 P. vivax infections/person-year (relative risk=0.99; 95% confidence interval=0.72-1.29), respectively. During their first infections, the children had higher P. falciparum parasitaemias than the adults (with geometric means of 1318 and 759 parasites/microl, respectively; P=0.04) but similar P. vivax parasitaemias (with geometric means of 355 and 331 parasites/microl, respectively; P=0.76). At first infection, 56% of the subjects were febrile and 90% complained of symptoms. There were no differences between children and adults with respect to these two parameters, either for P. falciparum or P. vivax. These findings indicate that, with promptly diagnosed and treated uncomplicated malaria, migrant children and adults in north-eastern Indonesian Papua have an equal risk of malarial infection and of disease following their first infections with P. falciparum and P. vivax.

Chloroquine or sulfadoxine-pyrimethamine for the treatment of uncomplicated, Plasmodium falciparum malaria during an epidemic in Central Java, Indonesia

A recent malaria epidemic in the Menoreh Hills of Central Java has increased concern about the re-emergence of endemic malaria on Java, which threatens the island's 120 million residents. A 28-day, in-vivo test of the efficacy of treatment of malaria with antimalarial drugs was conducted among 167 villagers in the Menoreh Hills. The treatments investigated, chloroquine (CQ) and sulfadoxine-pyrimethamine (SP), constitute, respectively, the first- and second-line treatments for uncomplicated malaria in Indonesia. The prevalence of malaria among 1389 residents screened prior to enrollment was 33%. Treatment outcomes were assessed by microscopical diagnoses, PCR-based confirmation of the diagnoses, measurement of the whole-blood concentrations of CQ and desethylchloroquine (DCQ), and identification of the Plasmodium falciparum genotypes. The 28-day cumulative incidences of therapeutic failure for CQ and SP were, respectively, 47% (N = 36) and 22% (N = 50) in the treatment of P. falciparum, and 18% (N = 77) and 67% (N = 6) in the treatment of P. vivax. Chloroquine was thus an ineffective therapy for P. falciparum malaria, and the presence of CQ-resistant P. vivax and SP-resistant P. falciparum will further compromise efforts to control resurgent malaria on Java.

Extensive multiple test centre evaluation of the VecTest malaria antigen panel assay

To determine which species and populations of Anopheles transmit malaria in any given situation, immunological assays for malaria sporozoite antigen can replace traditional microscopical examination of freshly dissected Anopheles. We developed a wicking assay for use with mosquitoes that identifies the presence or absence of specific peptide epitopes of circumsporozoite (CS) protein of Plasmodium falciparum and two strains of Plasmodium vivax (variants 210 and 247). The resulting assay (VecTest Malaria) is a rapid, one-step procedure using a 'dipstick' test strip capable of detecting and distinguishing between P. falciparum and P. vivax infections in mosquitoes. The objective of the present study was to test the efficacy, sensitivity, stability and field-user acceptability of this wicking dipstick assay. In collaboration with 16 test centres world-wide, we evaluated more than 40 000 units of this assay, comparing it to the standard CS ELISA. The 'VecTest Malaria' was found to show 92% sensitivity and 98.1% specificity, with 97.8% accuracy overall. In accelerated storage tests, the dipsticks remained stable for > 15 weeks in dry conditions up to 45 degrees C and in humid conditions up to 37 degrees C. Evidently, this quick and easy dipstick test performs at an acceptable level of reliability and offers practical advantages for field workers needing to make rapid surveys of malaria vectors.

The drug sensitivity and transmission dynamics of human malaria on Nias Island, North Sumatra, Indonesia

Nias Island, off the north-western coast of Sumatra, Indonesia, was one of the first locations in which chloroquine-resistant Plasmodium vivax malaria was reported. This resistance is of particular concern because its ancient megalithic culture and the outstanding surfing conditions make the island a popular tourist destination. International travel to and from the island could rapidly spread chloroquine-resistant strains of P. vivax across the planet. The threat posed by such strains, locally and internationally, has led to the routine and periodic re-assessment of the efficacy of antimalarial drugs and transmission potential on the island. Active case detection identified malaria in 124 (17%) of 710 local residents whereas passive case detection, at the central health clinic, confirmed malaria in 77 (44%) of 173 cases of presumed 'clinical malaria'. Informed consenting volunteers who had malarial parasitaemias were treated, according to the Indonesian Ministry of Health's recommendations, with sulfadoxine-pyrimethamine (SP) on day 0 (for P. falciparum) or with chloroquine (CQ) on days 0, 1 and 2 (for P. vivax). Each volunteer was then monitored for clinical and parasite response until day 28. Recurrent parasitaemia by day 28 treatment was seen in 29 (83%) of the 35 P. falciparum cases given SP (14, 11 and four cases showing RI, RII and RIII resistance, respectively). Recurrent parasitaemia was also observed, between day 11 and day 21, in six (21%) of the 28 P. vivax cases given CQ. Although the results of quantitative analysis confirmed only low prevalences of CQ-resistant P. vivax malaria, the prevalence of SP resistance among the P. falciparum cases was among the highest seen in Indonesia. When the parasites present in the volunteers with P. falciparum infections were genotyped, mutations associated with pyrimethamine resistance were found at high frequency in the dhfr gene but there was no evidence of selection for sulfadoxine resistance in the dhps gene. Night-biting mosquitoes were surveyed by human landing collections and tested for sporozoite infection. Among the five species of human-biting anophelines collected, Anopheles sundaicus was dominant (68%) and the only species found to be infective--two (1.2%) of 167 females being found carrying P. vivax sporozoites. The risk of malarial infection for humans on Nias was considered high because of the abundance of asymptomatic carriers, the reduced effectiveness of the available antimalarial drugs, and the biting and infection 'rates' of the local An. sundaicus.

Randomized, parallel placebo-controlled trial of primaquine for malaria prophylaxis in Papua, Indonesia

Malaria causes illness or death in unprotected travelers. Primaquine prevents malaria by attacking liver-stage parasites, a property distinguishing it from most chemoprophylactics and obviating 4-week postexposure dosing. A daily adult regimen of 30 mg primaquine prevented malaria caused by Plasmodium falciparum and P. vivax for 20 weeks in 95 of 97 glucose-6-phosphate dehydrogenase (G6PD)-normal Javanese transmigrants in Papua, Indonesia. In comparison, 37 of 149 subjects taking placebo in a parallel trial became parasitemic. The protective efficacy of primaquine against malaria was 93% (95% confidence interval [CI] 71%-98%); against P. falciparum it was 88% (95% CI 48%-97%), and >92% for P. vivax (95% CI >37%-99%). Primaquine was as well tolerated as placebo. Mild methemoglobinemia (mean of 3.4%) returned to normal within 2 weeks. Blood chemistry and hematological parameters revealed no evidence of toxicity. Good safety, tolerance, and efficacy, along with key advantages in dosing requirements, make primaquine an excellent drug for preventing malaria in nonpregnant, G6PD-normal travelers.

Effects of nutritional and physiological status on behavioral avoidance of Anopheles minimus (Diptera: Culicidae) to DDT, deltamethrin and lambdacyhalothrin

The monitoring of behavioral responses of mosquitoes to insecticides are critical to the understanding of how chemicals function in the control of disease transmission. The excito-repellency avoidance responses of laboratory-reared Anopheles minimus females exposed to diagnostic concentrations of DDT (2 g/m2), deltamethrin (0.0625 g/m2), and lambdacyhalothrin (0.0369 g/m2) were observed using an excito-repellency escape chamber. Insecticide contact (measuring irritancy) and non-contact (measuring repellency) behavioral assays were conducted on non-blood-fed (unfed), sugar-fed, early blood-fed (recently engorged) and late blood-fed mosquitoes. Rates of escape from the contact and non-contact chambers, regardless of chemical compounds, were most dramatic in unfed mosquitoes compared to other nutritional states (P < 0.05). In general, across all 3 chemicals, slower escape response was observed in sugar-fed and early blood-fed specimens, whereas late blood-fed showed an intermediate response. Relative suppression of escape flight response in comparison to matched non-insecticide treated controls and the unfed condition is likely the result of normal reduced flight activity among recent blood and sugar-engorged mosquitoes. We conclude that nutritional states and physiological conditions of mosquitoes as a result of blood feeding can dramatically influence excito-repellency test results. Therefore, for interpretive purposes, studies on chemical irritancy and repellency must account and control for the inherent variability of avoidance responses to insecticides influenced by nutritional and physiological conditions of the mosquitoes at the time of test.

Detection of dengue viral RNA in Aedes aegypti (Diptera: Culicidae) exposed to sticky lures using reverse-transcriptase polymerase chain reaction

Active surveillance for dengue (DEN) virus infected mosquitoes can be an effective way to predict the risk of dengue infection in a given area. However, doing so may pose logistical problems if mosquitoes must be kept alive or frozen fresh to detect DEN virus. In an attempt to simplify mosquito processing, we evaluated the usefulness of a sticky lure and a seminested reverse-transcriptase polymerase chain reaction assay (RT-PCR) for detecting DEN virus RNA under laboratory conditions using experimentally infected Aedes aegypti (L.) mosquitoes. In the first experiment, 40 male mosquitoes were inoculated with 0.13 microl of a 10(4) pfu/ml DEN-2 stock solution. After a 7-d incubation period, the mosquitoes were applied to the sticky lure and kept at room temperatures of 23-30 degrees C. Following 7, 10, 14, and 28 d application, 10 mosquitoes each were removed from the lure, pooled, and assayed for virus. DEN virus nucleic acid was clearly detectable in all pools up to 28 d after death. A second study evaluated sensitivity and specificity using one, two, and five DEN-infected mosquitoes removed after 7,10, 14, 21, and 30 d application and tested by RT-PCR. All four DEN serotypes were individually inoculated in mosquitoes and evaluated using the same procedures as experiment 1. The four serotypes were detectable in as few as one mosquito 30 d after applications to the lure with no evidence of cross-reactivity. The combination of sticky lures and RT-PCR show promise for mosquito and dengue virus surveillance and warrant further evaluation.

Epidemic dengue transmission in southern Sumatra, Indonesia

An outbreak of dengue fever (DF), dengue haemorrhagic fever (DHF), and dengue shock syndrome (DSS) in the city of Palembang, south Sumatra, Indonesia was investigated to (i) validate epidemic occurrence, (ii) confirm dengue virus aetiology and associated serotype(s), (iii) provide a demonstrable measure of community impact, and (iv) identify causative relationship (if any) with climatic El Niño Southern Oscillation (ENSO) influences. Trend analysis based on a 6-year retrospective review of hospital records demonstrates a 3-fold increase in clinical cases for the outbreak period (January-April 1998), relative to historical records. In the 2 hospitals surveyed, the monthly mean number of outbreak-related dengue cases over 4 months was 833 (range 650-995 cases/month); the mean monthly value for the previous 72 months was 107 (range 14-779 cases/month). An apparent trend in epidemic transmission was observed, evolving from a 5-year cyclic phenomenon to an annual occurrence, often indistinguishable from one year to the next. The proportional distribution of clinical outbreak cases into DF, DHF and DSS diagnostic categories was 24%, 66%, and 10%, respectively. The population aged 10-19 years accounted for the largest (35%) proportion of hospitalized DHF cases, followed by children aged 5-9 years (25%) and children aged 4 years (16%). Serum samples obtained during acute illness from 221 hospitalized patients were examined using serology, RT-PCR, and virus isolation in cell culture: 59% of samples had laboratory evidence of a dengue infection. All 4 dengue virus serotypes (DEN 1-4) were identified in epidemic circulation, with DEN 3 predominating (43%). DEN 1 was the principal serotype associated with less severe dengue illness, suggesting that virulence may be, in part, a function of infecting serotype. The climatic influence of ENSO on rainfall and temperature in the months leading up to and during the outbreak was dramatic, and is likely to contribute to favourable outbreak conditions.

Plasmodium vivax polymorphs and Plasmodium falciparum circumsporozoite proteins in Anopheles (Diptera: Culicidae) from Belize, Central America

Eight species of Anopheles mosquitoes from indoor/outdoor human landing collections in Belize, Central America, were examined for human Plasmodium circumsporozoite protein (CSP) using an enzyme-linked immunosorbent assay (ELISA). A total of 14 of 9,104 females tested were positive from general surveys throughout Belize and three of 11,966 were positive from a longitudinal study in Caledonia, northern Belize. ELISA results, using pooled head-thorax preparations and species-specific monoclonal antibodies directed against the circumsporozoite proteins of Plasmodium falciparum and two Plasmodium vivax polymorphs (210 and VK247), found four species reactive: Anopheles vestitipennis (3 pools), Anopheles darlingi (2 pools), Anopheles albimanus (10 pools), and Anopheles gabaldoni (2 pools). The minimum field infection rates (MFIR) for combined Plasmodium species from the general survey were 0.282% for An. vestitipennis, 0.271% for An. darlingi, 0.126% for An. albimanus, and 0.395% for An. gabaldoni. MFIRs for combined Plasmodium species from the longitudinal study in the village of Caledonia were 0.018% for both An. vestitipennis and An. albimanus and 1.66% for An. gabaldoni. Positive CSP pools were collected from the Cayo, Corozal, Orange Walk, Stann Creek, and Toledo political districts. No CSP positive pools were detected from collections in the Belize District. The study provides valuable information on the spatial distribution and species type of Plasmodium positive mosquitoes. This information, in combination with other vector data, suggest that An. vestitipennis and An. darlingi are commonly involved in malaria transmission. Additionally, these species appear to be much more efficient vectors than An. albimanus in Belize.

Rediscovery of Anopheles (Cellia) clowi (Diptera: Culicidae), a rarely recorded member of the Anopheles punctulatus group

Anopheline specimens collected in Papua New Guinea were morphologically identified as the rarely recorded Anopheles clowi Rozeboom & Knight. Amplification of the rDNA ITS2 region of this material revealed a fragment of 750 bp confirming its placement in the Anopheles punctulatus group. This group contains 12 species and includes the major malaria vectors in the islands of the southwest Pacific. Digestion of the ITS2 with the restriction enzyme MspI produced restriction fragment-length polymorphism with bands at 380, 300, and 150 bp, a pattern shared by no other members of this group. Phylogenetic analysis involving the sequencing of a 2 kb region of the rDNA 18S gene indicated that An. clowi was monophyletic and basal to the rest of the group and showed considerable independent evolution from the other members. This is the first record of An. clowi in Papua New Guinea and only the third collection of this species since its discovery in 1945.

Status of malaria in Thailand

Despite decades of control success and a competent network of country-wide health infrastructure, malaria remains an important health threat in rural Thailand. All 4 known human malaria parasites have been reported present, with Plasmodium falciparum and Plasmodium vivax predominant. The expansion and intensity of multi-drug resistant Plasmodium falciparum is the most serious development to occur the last several decades. Members of 3 anopheline species complexes, Anopheles dirus, Anopheles minimus, and Anopheles manculatus, are considered to be primary malaria vectors in the country. Representatives within all 3 taxa are difficult or impossible to separate morphologically from one another, and insufficient information exists about population genetics between sibling species and vector status. Vector control in Thailand has been the primary means of malaria control, mainly by the use of routine residual insecticide spray inside houses. The use of DDT in vector control has resulted in measurable successes to interrupt malaria transmission in many parts of the country. Since 1949, DDT has been the predominant compound used: however, its public health use has continued to decline as a result of perceived operational difficulties, political issues and environmental concerns. The increased use of pyrethroids to impregnate bednets and for intradomiciliary spraying are generally more accepted by rural populations and are rapidly replacing the use of DDT. Organized malaria control activities have reduced malaria morbidity from 286/1,000 population in 1947 to 1.5/1,000 population by 1996. Despite encouraging trends in dramatically reducing malaria, the rates of disease may be re-emerging in the country as evidence from an increased annual parasite index from 1.78/1,000 in 1997 to 2.21 in 1998. The possible reasons for the apparent increase in incidence are discussed in terms of the technical, operational and social obstacles in malaria control in Thailand.

El Niño and associated outbreaks of severe malaria in highland populations in Irian Jaya, Indonesia: a review and epidemiological perspective

Perennial malaria is a major public health problem for most coastal, lowland and foothill populations in Irian Jaya (western New Guinea), the largest and easternmost province of Indonesia. Malaria at higher elevations above 1,500 m is considered intermittent and highly unstable, providing a constant threat of epidemics. Beginning in late August 1997, a significant increase of unexplained deaths was reported from the central highland district of Jayawijaya. The alarming number of fatalities rapidly escalated into September, dropping off precipitously by late October. More than 550 deaths due to "drought-related" disease had been officially reported from the district during this 10-week period. The outbreaks occurred in extremely remote areas of steep mountainous terrain inhabited by primitive shifting agriculturist populations. Microscopical evidence and site survey data implicated malaria as the principal cause of the excess morbidity and mortality at elevations between approximately 1,000 and 2,200 m. The dramatic increase in malaria and associated deaths was indirectly related to the prolonged and severe drought created by the prevailing 1997-98 El Niño Southern Oscillation (ENSO) affecting the Australasian region. Clinical cases of malaria were described as severe, due, in large part to the low level of naturally acquired immunity (NAI) in these highland populations and the predominance of Plasmodium falciparum infection. Disease may have been further exacerbated by the population's compromised nutritional status because of severe shortages of staple foods affected by the drought. Based on a retrospective investigation, an 'a posteriori' epidemiological explanation of the probable, interrelated causes of the epidemic is presented. Beginning in late July 1997, drought conditions resulted in numerous, transient pools of standing water along zones of steep gradient streams normally associated with fast-flowing water. This permitted sufficient and rapid increases in vector populations (Anopheles punctulatus complex) that either could sustain recently introduced or intensified local low-level malaria transmission. Moreover, water and food shortages contributed to increased demographic movement and exposure to high risk malaria endemic lowlands, thus increasing the prevalence of human infections and infectious reservoirs in those populations returning to the highlands. The eventual rapid drying and elimination of the vector larval habitats along stream beds, combined with mass antimalarial drug distribution are believed, in part, to be responsible for the rapid decline of severe malaria and related deaths. Area delimited and isolated focal outbreaks of malaria are recognized as occasional, periodic events in these highlands. This epidemic produced great concern because of the broad regionalized extent of the problem, the culmination of many independent outbreaks occurring during the same period that overwhelmed the local health care and control capabilities. We predict communicable disease outbreaks, including malaria, may likely increase in periodicity in the Irian Jaya highlands as socioeconomic development and population movements increase. This investigation further underscores the importance of malaria and its impact on presumed NAI deficient highland populations. Furthermore, the association of ENSO-related climatic anomalies and heightened infectious disease transmission is illustrative of how rapidly changing local weather events can dramatically alter disease patterns. These circumstantial findings, albeit important, point to the urgent need for more definitive understanding of highland malaria dynamics, the development of a sustainable longitudinal surveillance system, and appropriate outbreak response capabilities for the highlands of Irian Jaya.

Use of a funnel trap for collecting immature Aedes aegypti and copepods from deep wells in Yogyakarta, Indonesia

During the course of a "dry" season dengue vector survey, indoor and outdoor household wells were sampled for the possible presence of immature mosquitoes and copepods. With a simple floating funnel trap, Aedes aegypti immature stages were captured in over 33% of the sampled wells (n = 93) during a 24-h trapping period per well. Average number of larvae (all instars) per positive well was 8.8 (range 1-63). Positive wells varied in depth from 2.7 to 14.7 m (8.8-48.2 ft), with a mean of 7.9 +/-SE 0.5 m in well rim to water surface. Only 4 wells (4.3%) contained Culex quinquefasciatus larvae. Only 1 of 31 infested wells contained both species. Aedes albopictus was not detected in any of the wells. Cyclopoid copepods were captured in 15% of the wells. No significant difference was found between positive and negative wells with regard to the physical characteristics (inside diameter, distance to water level) or the depth and volume of water held at the time of sampling. A significant association was found between wells positive for larvae and numbers of other positive containers in the vicinity of the wells. In general, wells containing copepods had fewer larvae present in the trap, possibly indicating some level of natural population regulation of Ae. aegypti occurring in the well; however, this association was not significant. Preliminary results indicate that wells in Yogyakarta serve as important permanent habitats for Ae. aegypti, especially during the dry season.

Rare quadruple malaria infection in Irian Jaya Indonesia

We report an exceptional finding from a blood slide collected in a remote area in the western half of New Guinea Island (Irian Jaya Province, Indonesia). One adolescent patient was found patently coinfected with all 4 known human malaria species, Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale. Diagnostic erythrocytic stages of all 4 species were clearly seen in the peripheral blood. A nested polymerase chain reaction, using species-specific primer pairs to detect DNA, helped substantiate this finding. Previous reports from Africa, Thailand, and New Guinea have detected all 4 species in a population but not simultaneously in an individual with a patent, microscopically detectable infection. We believe this quadruple infection represents the first reported natural case of all 4 human malaria parasites observed concurrently in the peripheral blood from a single Giemsa-stained slide.

In vivo responses to antimalarials by Plasmodium falciparum and Plasmodium vivax from isolated Gag Island off northwest Irian Jaya, Indonesia

There is renewed interest in the rich nickel and cobalt deposits of Pulau Gag, an isolated but malarious island off the northwest coast of Irian Jaya. In preparation for an expanded workforce, an environmental assessment of malaria risk was made, focusing upon malaria prevalence in the small indigenous population, and the in vivo sensitivity of Plasmodium falciparum and P. vivax to chloroquine (CQ) and sulfadoxine/pyrimethamine (S/P), the respective first- and second-line drugs for uncomplicated malaria in Indonesia. During April-June 1997, mildly symptomatic or asymptomatic malaria infections were found in 24% of 456 native residents. Infections by P. falciparum accounted for 60% of the cases. Respective day 28 cure rates for CQ (10 mg base/kg on days 0 and 1; 5 mg/kg on day 2) in children and adults were 14% and 55% (P < 0.005). Type RII and RIII resistance characterized only 5% of the CQ failures. Re-treatment of 36 P. falciparum CQ treatment failures with S/P (25 mg/kg and 1.25 mg/kg, respectively) demonstrated rapid clearance and complete sensitivity during the 28-day follow-up period. More than 97% of the P. vivax malaria cases treated with CQ cleared parasitemia within 48 hr. Three cases of P. vivax malaria recurred between days 21 and 28, but against low drug levels in the blood. The low frequency of RII and RIII P. falciparum resistance to CQ, the complete sensitivity of this species to S/P, and the absence of CQ resistance by P. vivax are in contrast to in vivo and in vitro test results from sites on mainland Irian Jaya.

Chloroquine-resistant Plasmodium vivax in transmigration settlements of West Kalimantan, Indonesia

Malariometric surveys were conducted during July 1996 in native Dayak villages and predominantly Javanese transmigration settlements in Ketapang district of West Kalimantan, Indonesia. Malaria prevalence ranged from 0.9% to 2.7% in Dayak villages and from 1% to 20% in the transmigration settlements. Plasmodium falciparum accounted for 67% of the cases among Dayaks but P. vivax was dominant among transmigrants, accounting for more than 72% of the infections. Chloroquine sensitivity/resistance was assessed by 28-day in vivo testing of uncomplicated malaria infections and measurement of chloroquine blood levels in cases where parasitemias reappeared within the 28-day test period. Resistance was based on the appearance of asexual parasites against chloroquine plus desethylchloroquine levels exceeding the minimally effective whole blood concentrations proposed for sensitive parasite strains (P. vivax, 100 ng/ml; P. falciparum, 200 ng/ml). All parasitemias cleared initially within four days of beginning supervised chloroquine therapy (25 mg base/kg over a 48-hr period), but asexual parasites reappeared within 28 days in 27 of 52 P. vivax and three of 12 P. falciparum cases. Chloroquine blood levels at the time of recurrent parasitemias revealed resistance in 12 of the 27 P. vivax cases and in one of the three P. falciparum cases. Genotypes of nine of the 12 recurrent P. vivax isolates matched with their primary isolates and ruled out reinfection. These findings establish the presence of chloroquine-resistant P. vivax on the island of Borneo. The pattern of malaria and the high frequency of chloroquine resistance by P. vivax at the West Kalimantan location may relate to demographic, ecologic, agricultural, and socioeconomic changes associated with transmigration.

Pesticide avoidance behavior in Anopheles albimanus, a malaria vector in the Americas

The behavioral responses of 4 populations of Anopheles albimanus females to DDT, permethrin, and deltamethrin were characterized in excito-repellency tests. One test population (ST) from El Salvador has been maintained as a colony for 20 years. A second population (ES) from Guatemala was colonized in 1992. Third and fourth populations consisted of field-caught specimens from Toledo District (TO) of southern Belize in 1994 and Corozal District (CO) of northern Belize, respectively. Females of ES, TO, and CO populations rapidly escaped from direct contact with treated surfaces for each of the 3 insecticides. Similarities in escape responses of insecticide-resistant (ES) versus insecticide-susceptible populations (TO, CO) suggest that there is no relationship between physiological and behavioral responses of An. albimanus populations to DDT, permethrin, and deltamethrin. Females from all but the ST colony escaped in greater numbers from chambers without direct contact with treated surfaces than from control chambers (P < 0.05). Few females from the ST colony escaped from test chambers, regardless of which insecticide was used or whether contact was allowed, indicating that the ST colony has lost its capability to respond to insecticides. Repellent responses were significant; but they were not pronounced in 30-min exposures, and they were very pronounced in 4-h exposures. We conclude that irritant and repellent responses of malaria vectors to insecticides are important components of malaria control operations.

Assessment of age-dependent immunity to malaria in transmigrants

Sixty-six Javanese transmigrants moving from Java, an area of very low malaria transmission, to Irian Jaya, an area of high malaria transmission, were monitored to evaluate the effects of exposure to malaria transmission and age on resistance to infection and the induction of humoral immunity. The risk of acquiring Plasmodium falciparum parasitemia was not statistically greater in children (5-15 years of age) than in adults (> 15 years of age) during the first 14 months of exposure. However, during the cross-sectional survey at 14 months of exposure. children did have significantly higher P. falciparum asexual blood-stage parasite densities. Serum antibody titers to R32LR, a peptide containing sequences from the P. falciparum circumsporozoite repeat region, and MSP19, a proteolytic fragment of merozoite surface protein-1 (MSP-1) from P. falciparum, were measured by enzyme-linked immunosorbent assay. Exposure for both six and 14 months produced statistically significant increased antibody titers to both R32LR and MSP-1; no age-dependent difference in antibody titers was observed. In this population, exposure to malaria transmission induced antibodies to antigens associated with immunity to malaria. In addition, we noted an age-dependent difference in the parasitemia density of P. falciparum.

Halofantrine and primaquine for radical cure of malaria in Irian Jaya, Indonesia

The combination of halofantrine and primaquine therapies was calculated as a regimen for achieving radical curve of falciparum or vivax malaria in Irian Jaya, Indonesia, and compared with combined chloroquine and primaquine therapies. The patients who volunteered for the study [adult, male, Indonesian immigrants with no previous exposure to endemic malaria, normal glucose-6-phosphate dehydrogenase (G6PD) activity, uncomplicated malaria illness, no prior use of antimalarials, and parasitaemias of 0.001%-1.1%] were randomized to receive either halofantrine (24 mg base/kg bodyweight, in three equal doses over 12 h) or chloroquine (25 mg base/kg bodyweight over 48 h, in doses of 10, 10 and 5 mg base/kg at 24-h intervals). Each patient also received concurrent daily primaquine (0.5 mg base/kg bodyweight) for 14 days followed by the same dose on alternate days to day 28. A recurrent parasitaemia during the 28 days of follow-up constituted drug failure. Of the 40 cases of falciparum malaria and 26 cases of vivax malaria treated with halofantrine-primaquine, none had a recurrent parasitaemia (100% efficacy). In contrast, 20 of 30 patients with falciparum malaria and three of 27 with vivax malaria had recurrent parasitaemias after chloroquine-primaquine, giving efficacies of 33% and 89%, respectively. Halofantrine-primaquine was significantly more effective than chloroquine-primaquine against falciparum malaria (P < 0.001) but was similarly efficacious against vivax malaria (P = 0.23). On average, fever associated with falciparum or vivax malaria cleared 17 h faster with halofantrine-primaquine (P < 0.01) although there were no significant differences (P > 0.4) in parasite-clearance times between the two regimens. The halofantrine-primaquine regimen was also associated with a more rapid and significant decline in malaria-related physical complaints.

Intestinal parasites of humans in a highland community of Irian Jaya, Indonesia

An indigenous, highland community in the Oksibil Valley of Irian Jaya, Indonesia, was examined on two occasions to determine the prevalence of intestinal parasites. Overall, 478 subjects from three villages in the study area, about 10% of the available population, were sampled. Using a standard, wet-mount technique, 15 different species of parasites were found. Hookworm was predominant in all age groups, with prevalences of 51%-86%, followed by Ascaris lumbricoides (46%-57%) and Trichuris trichiura (15%-25%). Strongyloides stercoralis was only seen infrequently (< 1%). In general, intestinal protozoa were uncommon. Entamoeba histolytica (14%-20%) and Entamoeba coli (12%-17%) were the most frequent. Sex- and age-specific differences were not dramatic but prevalences and species diversity both increased with age up to 6-15 years, then decreased slightly into adulthood. Rarely were faecal samples free of detectable parasites and some adult subjects had as many as six species. The results are discussed with respect to previous studies in the highlands of New Guinea and the local transmission of soil- and water-borne parasites.

Malaria transmission by Anopheles punctulatus in the highlands of Irian Jaya, Indonesia

A 21-month (1991-1992) assessment of malaria and the relative contribution of Anopheles punctulatus and An. koliensis to its transmission was conducted in Oksibil, a highland community in Irian Jaya, Indonesia. Nearly all (98%) of the 2577 Anopheles from indoor or outdoor human-landing collections were An. punctulatus. Nineteen (0.75%) of the 2518 An. punctulatus tested were positive when tested for malaria circumsporozoite protein (CSP) by ELISA: nine (45% of positives) for Plasmodium vivax-210, six (30%) for Plasmodium falciparum, three (15%) for P. vivax-247 and two (10%) for P. malariae. One mosquito was positive for both P. vivax 210 and P. falciparum. All 59 An. koliensis tested were negative. All mosquitoes positive for CSP were from indoor collections, 89% from the main houses and the remaining 11% from the traditional dwellings (bokams). These findings are discussed with respect to highland malaria epidemiology and transmission in the Oksibil Valley.

Susceptibility of various mosquitoes of California to subperiodic Brugia malayi

Laboratory experiments were conducted to determine the susceptibility of six species of mosquitoes, representing three genera, to subperiodic Brugia malayi. The black-eye, Liverpool strain of Aedes aegypti was the susceptible control. Mosquitoes were fed on microfilaremic jirds (Meriones unguiculatus). All mosquitoes, except wild caught Culex erythrothorax, were laboratory-reared and allowed to feed when 8 to 10 days old. Anopheles freeborni, Anopheles hermsi, and Culiseta inornata proved refractory. Both Anopheles species allowed invasion of flight muscle and development to the late first stage, after which larval growth ceased and melanization occurred. Culiseta inornata prevented any larval development. Culex tarsalis and Cx. erythrothorax proved highly susceptible to B. malayi infection. In all, 95.6% and 88.7% of the Cx. tarsalis harbored third-stage larvae after infective feedings of 15.7 and 81.8 mf/microliters of blood, respectively, while only 11.5% were found susceptible when microfilaremia was low (1.1 mf/microliters). Culex erythrothorax demonstrated a susceptibility rate of 82.3% with 17.0 mf/microliters. Both Culex species appear to be excellent experimental hosts for subperiodic B. malayi. This is the first conclusive evidence that mosquitoes of the genus Culex can naturally support the complete development of a stain of subperiodic B. malayi.

Primaquine for prophylaxis against malaria among nonimmune transmigrants in Irian Jaya, Indonesia

A comparison of primaquine versus chloroquine for prophylaxis among nonimmune transmigrants from Java and Bali in the hyperendemic Arso region of Irian Jaya, Indonesia was conducted. Forty-five subjects received 0.5 mg of primaquine base/kg of body weight every other day, and 54 people in the same village received weekly 5 mg of chloroquine base/kg for 16-19 weeks beginning in December 1992. Plasmodium falciparum accounted for 18 of 30 infections with chloroquine, and four of five infections among subjects receiving primaquine. Plasmodium vivax was found in 12 people taking chloroquine but in just one person taking primaquine. The risk of malaria among people taking chloroquine relative to that among subjects taking primaquine was 3.96 (P = 0.014) for P. falciparum and 10.56 (P = 0.012) for P. vivax. Primaquine was better tolerated than chloroquine. The minimal protective efficacy for primaquine prophylaxis was 74% against P. falciparum and 90% against P. vivax among nonimmune children and adults living in Irian Jaya. These findings require confirmation with randomized, double-blinded, and placebo-controlled trials.

Colonization of Anopheles barbirostris from Central Java, Indonesia

The colonization of Anopheles barbirostris from Central Java is described. Locally acquired materials and ambient laboratory temperature, humidity, and daylight proved acceptable for continuous rearing. A simple, inexpensive larval diet based on a 10:4 powdered mixture of beef and rice hulls proved advantageous.

Malaria vaccine study site in Irian Jaya, Indonesia: Plasmodium falciparum incidence measurements and epidemiologic considerations in sample size estimation

Malaria epidemiologic and entomologic studies were performed during both the high transmission and low transmission seasons to characterize the Plasmodium falciparum malaria transmission at a proposed malaria vaccine trial site in Irian Jaya, Indonesia. The study population consisted of two subsets: native Irianese men with lifelong exposure to malaria and transmigrants who arrived from a nonmalarious area 2.5 years before the start of the study. All subjects received a radical cure for malaria and were then monitored weekly by blood film. Both P. falciparum malaria attack rates and incidence densities were calculated; transmigrants had a significantly higher rate (P = 0.003) than the Irianese during the low transmission season study (20-weeks long) but not during the high transmission season study (12-weeks long). Lack of exposure-induced immunity left the transmigrants at a minimum 17-25% greater relative risk of becoming parasitemic compared with the Irianese during the low transmission season study. During the high transmission season study, 50% of the transmigrants were P. falciparum positive by week 6 and 50% of the Irianese by week 9. During the low transmission season, 50% of the transmigrants were positive by week 10 and 43% of the Irianese were positive by week 17. Entomologic studies showed that Anopheles koliensis was the predominant vector (> 98% of anopheline catch). Entomologic inoculation rates for P. falciparum were 0.018 and 0.39 infective bites/person/night for the low and high transmission seasons, respectively. New P. vivax cases represented between 16% and 42% of all initial malaria cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for anti-Plasmodium falciparum antibodies that cross-react with human T-lymphotropic virus type I proteins in a population in Irian Jaya, Indonesia

This study was performed to demonstrate the presence of anti-Plasmodium falciparum antibodies in a population living in Irian Jaya, Indonesia that cross-react with human T-lymphotropic virus type I (HTLV-I) proteins. Serum samples from 63 volunteers living in Oksibil, a secluded highland valley in Irian Jaya, were tested for anti-P. falciparum antibodies by an immunofluorescence assay and for anti-HTLV-I antibodies by an enzyme immunoassay (EIA). All samples were positive for anti-P. falciparum antibodies at titers of > or = 1:256. Twenty-four samples were reactive by EIA for HTLV-I, and of these, 23 were tested by western blotting (immunoblotting). Five of the 23 samples were classified as western blot positive and 18 were classified as western blot indeterminate. In competitive blocking assays with malaria proteins, western blot immunoreactivity to all HTLV-I Gag proteins was either reduced or eliminated. Significant reductions in the HTLV-I EIA optical density values of the Oksibil sera occurred when the sera were competitively blocked with the malaria antigens. The optical density values of HTLV-I-positive control sera showed no significant change. Competitive blocking with HTLV-I antigens produced reductions in the optical density values of both the Oksibil sera and the HTLV-I-positive control sera. These data suggest that in this population, anti-P. falciparum antibodies are cross-reactive with HTLV-I proteins in the western blot and EIA tests.

Allelic variants of the Plasmodium falciparum merozoite surface antigen 2 (MSA-2) in a geographically restricted area of Irian Jaya

Blood samples were collected from 12 residents of 4 villages in the Oksibil area of Irian Jaya. Eleven patients were positive for Plasmodium falciparum infection as evidenced by successful amplification of the MSA-2 gene by the polymerase chain reaction. Two patients showed evidence of infection by 2 strains of Plasmodium falciparum. All MSA-2 genes were completely sequenced and all could be assigned to one of the two major allelic families of MSA-2, however all MSA-2 gene sequences differed from previously described alleles. Five new allelic forms were identified, one of which was present in 8 of the 11 patients. Within small natural populations of P. falciparum, it appears that variation in MSA-2 approximates that seen world-wide. All samples were also analysed by hybridisation of amplified DNA to family specific probes and all samples hybridised to known probes. Our results demonstrate that there is a degree of microheterogeneity of MSA-2 that is undetectable by hybridisation studies alone.

Age-specific prevalence of Plasmodium falciparum among six populations with limited histories of exposure to endemic malaria

The age-specific prevalence of Plasmodium falciparum parasitemia among residents of six villages in northeastern Irian Jaya, Indonesia, has been measured for a period of five years. All study subjects were transmigrants from Java living in Irian Jaya for three weeks to 72 months, depending upon the village and point of measurement. Fifteen separate estimates of prevalence were obtained from 4,554 Giemsa-stained thick blood films from 91 to 701 people (mean sample size = 304) among the six villages. The prevalence of parasitemia among people who had lived in Irian Jaya for less than one year did not decrease as a function of age, except in one village at eight months. In contrast, after 16 months to two years or more of residence, the prevalence of parasitemia decreased markedly with increasing age beyond 6-10 or 11-15 years. Social, behavioral, or entomologic characteristics of these populations did not explain the decreasing prevalence of parasitemia with age. An age-dependent naturally acquired protective immunity appeared to develop in all of these villages after 1-2 years of exposure to hyperendemic malaria.

Insecticide susceptibility status of Anopheles koliensis (Diptera: Culicidae) in northeastern Irian Jaya, Indonesia

Anopheles koliensis, an important malaria vector in the interior region of Irian Jaya, Indonesia, was evaluated for susceptibility to three different insecticide compounds using the standard World Health Organization diagnostic test kit and pretreated impregnated papers. A series of tests were conducted in Arso PIR I, a transmigrant settlement 60 km south of Jayapura, from January 1988 to May 1989. All compounds were tested at the recommended diagnostic dosage and exposure time. An. koliensis were susceptible to 1.0% fenitrothion at two hour exposure (N = 358) and 5.0% malathion at one hour exposure (N = 371) after the 24-hour holding period. Significant resistance to DDT was observed in both the An. koliensis and Culex quinquefasciatus populations. Approximately 30% of the An. koliensis population (N = 468) was resistant to 4% DDT at both one and two hour exposures. These findings indicate that routine use of DDT in Arso PIR I for indoor residual house spraying may be of limited effectiveness, in part, because of physiological resistance. However, use of an alternative insecticide will be more expensive and might prove equally ineffective because of the exophilic behavior of the species. This is the first confirmed report from repeated observations of DDT resistance in An. koliensis from Indonesia.

Prevalence of serum antibodies to human T lymphotropic virus-1 in an isolated tribe in the highlands of Irian Jaya, Indonesia

There have been several recent reports on the high prevalence of serum antibodies to human T lymphotropic virus-1 (HTLV-1) in isolated populations residing in the coastal areas and highlands of Papua New Guinea. In the absence of significant cases of clinical disease, it has been surmised that this reactivity might be the consequence of serologic recognition of yet undefined human retroviruses or parasite antigens. These observations prompted an investigation of the prevalence of anti-HTLV-1 antibodies among members of the Ngalum tribe that dwells in a secluded highland valley in the eastern Jayawijaya Mountains of Irian Jaya, Indonesian New Guinea. Of 165 tribespeople, 85 (52%) were positive for IgG antibodies to HTLV-1 in an indirect enzyme-linked immunosorbent assay. Eighty-two were more than 10 years of age. On the Western blot, all positive sera reacted strongly with the p19 core antigen, but recognition of the envelope antigens, gp46 and gp21, was conspicuously absent. Thirty-four of the 85 villagers with these indeterminant blots had active Plasmodium falciparum infections, but antibody absorption studies with HTLV-1 and P. falciparum erythrocytic stage antigens failed to confirm suspected serologic cross-reactivities. Thirty-three others had acute malaria and/or high titers of anti-malaria antibodies but were seronegative for HTLV-1. We suspect that indeterminant Western blots for HTLV-1 reflect antibody responses to related latent retroviruses that are activated as a consequence of immunosuppression following malaria infection and chloroquine therapy.

Vivax malaria resistant to treatment and prophylaxis with chloroquine

Chloroquine has been the treatment of choice for vivax malaria for more than 40 years. Lately, several case-reports have suggested the emergence of resistance to chloroquine in Plasmodium vivax in Papua New Guinea and Indonesia. We undertook prospective treatment and prophylaxis trials of chloroquine in children and adults with vivax malaria living in Irian Jaya (Indonesia New Guinea). 46 villagers with P vivax parasitaemia were treated with chloroquine by mouth (25 mg base/kg body weight divided over 3 days) and followed up for 14 days. Parasitaemia cleared initially but recurred within 14 days in 10 (22%) subjects. All recurrences were in children younger than 11 years, 7 of whom were younger than 4 years; the failure rate among children under 4 was 70%. 7 of the patients with recurrences were given a second course of chloroquine. In all, the infections initially cleared but recurrent parasitaemia developed in 5 (71%) within 14 days. Whole-blood chloroquine concentrations were consistently above those previously shown to cure P vivax blood infections (90 micrograms/L whole blood). Subjects whose initial infections cleared and who had no parasitaemia on day 14 received weekly prophylaxis with chloroquine. Despite the presence of expected blood chloroquine concentrations, P vivax parasitaemia developed in 9 of 17 subjects receiving prophylaxis during 8 weeks of follow-up (median time to parasitaemia 5.3 weeks). Chloroquine can no longer be relied upon for effective treatment or chemoprophylaxis of P vivax blood infections acquired in this part of New Guinea.

On-site diagnosis of Plasmodium falciparum, P. vivax, and P. malariae by using the Quantitative Buffy Coat system

The Quantitative Buffy Coat (QBC) system was used for the detection and identification of malaria parasites in blood specimens from 570 residents of Oksibil, an isolated highland valley in the eastern Jayawijaya Mountains of Irian Jaya (Indonesian New Guinea). The availability of a battery-powered centrifuge and a fiberoptic Paralens enabled us to complete and interpret the assay in this remote environment. Of 322 QBC tubes examined for 2-4 min each, results of 295 (92%) concurred with findings on the matched Giemsa-stained thick smear (GTS). The 27 discrepant results included 13 QBC+/GTS- that, upon reexamination, were found to be GTS+. When using the corrected GTS results as the standard, the sensitivity and specificity of the QBC were 94% and 96%, respectively. Because electricity was available only 3 hr per day, it was decided to decrease the examination for an additional 248 QBC to a maximum of 90 sec per tube. This shortened inspection time resulted in a reduction of sensitivity to 53% but specificity was preserved at 89%. Forty-two of 45 conflicting results, QBC-/GTS+ from cases of light Plasmodium falciparum infections with < 1 trophozoite or gametocyte per field, were resolved by reexamination of the QBC in the laboratory. Tubes held at 4 C could be reexamined, without noticeable loss of fluorescence, for at least 6 wk after collection. Despite some difficulty in the identification of Plasmodium species, it was concluded that the QBC is an easy, sensitive method for the rapid diagnosis of malaria in the field and that it provides the inexperienced microscopist with an additional means for on-site identification of individuals needing treatment.

Heightened transmission of stable malaria in an isolated population in the highlands of Irian Jaya, Indonesia

Malaria at an elevation of 1,500 meters is uncommon and is usually unstable when it occurs. To confirm reports of a recent increase in transmission of stable malaria in the Oksibil Valley, which is at an elevation of 1,250-1,500 meters in the Jayawijaya Mountains of Irian Jaya, Indonesia, five malariometric surveys were conducted in four villages between May 1990 and July 1991. A total of 3,380 blood smears, representative of 1,949 persons, was examined. Prevalence rates over the survey period were consistent in each of the four villages, averaging 10% for infants, 50% for children 1-4 years of age, 35% for those 5-9 years old, 28% for those 10-14 years old, and 16% for adults (greater than 15 years old). The spleen rate for the those less than five years old was 96%, with an average enlarged spleen score of 2.32. Plasmodium falciparum accounted for 55% of the infections in the valley, but P. vivax was the predominant species in those less than 10 years old. In the village of Kutdol at an elevation of 1,500 meters, P. malariae was identified in 43% of the positive smears. Four cases were diagnosed as P. ovale. Infection with P. falciparum without obvious clinical symptoms was common in both adults and children. Entomologic and epidemiologic data suggested that the recent upsurge in transmission coincided with the replacement of traditional village huts with the more modern social housing. This replacement required the extensive construction of drainage ditches, which inadvertently also served as additional vector breeding sites. We suspect that this manipulation of the environment, in an effort to improve the quality of life, created conditions conductive for heightened transmission of stable malaria.

Age-dependent acquired protection against Plasmodium falciparum in people having two years exposure to hyperendemic malaria

An epidemiologic study of susceptibility to frequent and high-grade parasitemia by Plasmodium falciparum revealed that age-dependent acquired protection developed within a two-year period of exposure to hyperendemic infection pressure. The study was conducted in a single village in northeastern Irian Jaya, Indonesia, where half the residents were native to the province and the other half were transmigrants from areas of Java, where there is little or no malaria transmission. Five separate measures of susceptibility to the asexual parasitemia of falciparum malaria were derived from results of four months of biweekly surveillance of 240 volunteers. Increasing protection as a function of age among the Javanese was a consistent pattern among the five estimates of susceptibility. These age-dependent functions of protection were quantitatively parallel to those among life-long residents of Irian Jaya. When humoral immune responsiveness to ring-infected erythrocyte surface antigen (RESA) was measured by ELISA, a similar pattern emerged; the relative level of antibody to RESA increased as parallel functions of age among the two subpopulations. Acquired protective immunity against P. falciparum was not the cumulative product of many years of heavy exposure to antigen. Instead, the full benefit of protection appeared to develop quickly. The degree of protection was governed by recent exposure and age, independent of history of chronic heavy exposure.

Resistance to antimalarials by Plasmodium falciparum in Arso PIR, Irian Jaya, Indonesia

Between 1987 and 1990, susceptibility of Plasmodium falciparum to chloroquine and to Fansidar was measured in vivo in 151 volunteers using the standard 7-day test. All volunteers lived in Arso PIR, Irian Jaya. A 25 mg/kg dose of chloroquine base was administered over a three-day period to 92 volunteers positive for P. falciparum rings (greater than 10 rings/200 white blood cells). Fifty volunteers (54%) showed results consistent with resistance. Twenty-nine were classified RII, and 21 RIII. In November 1989, a single curative dose of Fansidar was administered to 59 volunteers divided among three groups with 18 months, four years, and life-long exposure to endemic malaria. The proportion of volunteers in each group still positive for P. falciparum on day 7 of followup was 54%, 0%, and 14%, respectively. Thus, immune status profoundly effected clinically response to Fansidar. Standard in vitro microtests were also performed on parasites from 11 volunteers against chloroquine, amodiaquine, quinine, pyrimethamine/sulfadoxine, and and mefloquine. Nine of ten isolates showed in vitro growth consistent with resistance to chloroquine. Tests with other drugs showed few isolates with results considered indicative of susceptibility. Arso PIR has a severe drug resistance problem.

Resistance to chloroquine by Plasmodium vivax in Irian Jaya, Indonesia

Evidence of emerging resistance to chloroquine by Plasmodium vivax is described from Irian Jaya (Indonesian New Guinea). Sixteen of 24 residents in the village of Arso PIR II taking supervised weekly chloroquine prophylaxis (5 mg base/kg) had asexual parasitemia with P. vivax at least once during eight weeks of surveillance. An American working in the same village developed symptomatic P. vivax parasitemia despite chloroquine prophylaxis. Five days after therapy with 600 mg chloroquine base, the asexual parasitemia in the American increased 40-fold, but cleared after treatment with 1,500 mg chloroquine base. Serum samples were not available from many of the cases, but six local residents and the American had serum levels of chloroquine in excess of the ordinarily suppressive 15 ng/ml at the time of their asexual parasitemias (16-70 ng/ml). The weekly 300 mg base tablet of chloroquine, which has been the standard for prophylaxis against malaria for more than 40 years, was not effective against P. vivax in Arso PIR, Irian Jaya.

Cultivation of sexually mature Brugia malayi in vitro

Sexually mature male and female Brugia malayi were developed from third stage larvae after 60 days in the in vitro culture system described by Franke and others in 1987 (Am J Trop Med Hyg 37: 370-375). Between 75 and 100 days in culture, many worms produced living microfilariae. Each gravid female produced 200-1,500 microfilariae/day.