The epidemiological transition in Papua New Guinea: new evidence from verbal autopsy studies.

BACKGROUND: Recent economic growth in Papua New Guinea (PNG) would suggest that the country may be experiencing an epidemiological transition, characterized by a reduction in infectious diseases and a growing burden from non-communicable diseases (NCDs). However, data on cause-specific mortality in PNG are very sparse, and the extent of the transition within the country is poorly understood. METHODS: Mortality surveillance was established in four small populations across PNG: West Hiri in Central Province, Asaro Valley in Eastern Highlands Province, Hides in Hela Province and Karkar Island in Madang Province. Verbal autopsies (VAs) were conducted on all deaths identified, and causes of death were assigned by SmartVA and classified into five broad disease categories: endemic NCDs; emerging NCDs; endemic infections; emerging infections; and injuries. Results from previous PNG VA studies, using different VA methods and spanning the years 1970 to 2001, are also presented here. RESULTS: A total of 868 deaths among adolescents and adults were identified and assigned a cause of death. NCDs made up the majority of all deaths (40.4%), with the endemic NCD of chronic respiratory disease responsible for the largest proportion of deaths (10.5%), followed by the emerging NCD of diabetes (6.2%). Emerging infectious diseases outnumbered endemic infectious diseases (11.9% versus 9.5%). The distribution of causes of death differed across the four sites, with emerging NCDs and emerging infections highest at the site that is most socioeconomically developed, West Hiri. Comparing the 1970-2001 VA series with the present study suggests a large decrease in endemic infections. CONCLUSIONS: Our results indicate immediate priorities for health service planning and for strengthening of vital registration systems, to more usefully serve the needs of health priority setting.

Epidemiology of malaria in the Papua New Guinean highlands.

OBJECTIVES: To conduct an in-depth investigation of the epidemiology of malaria in the Papua New Guinea (PNG) highlands and provide a basis for evidence-based planning and monitoring of intensified malaria control activities. METHODS: Between December 2000 and July 2005, 153 household-based, rapid malaria population surveys were conducted in 112 villages throughout the central PNG highlands. The presence of malaria infections was determined by light microscopy and risk factors assessed using a structured questionnaire.The combined dataset from all individually published surveys was reanalysed. RESULTS: The prevalence of malaria infections in the different surveys ranged from 0.0% to 41.8%(median 4.3%) in non-epidemic surveys and 6.6% to 63.2% (median 21.2%, P < 0.001) during epidemics. Plasmodium falciparum was the predominant infection below 1400 m and during epidemics, Plasmodium vivax at altitudes >1600 m. Outside epidemics, prevalence decreased significantly with altitude, was reduced in people using bed nets [odds ratio (OR) = 0.8, P < 0.001] but increased in those sleeping in garden houses (OR = 1.34, P < 0.001) and travelling to highly endemic lowlands (OR = 1.80, P < 0.001). Below 1400 m, malaria was a significant source of febrile illness. At higher altitudes, malaria was only a significant source of febrile illness during epidemic outbreaks, but asymptomatic malaria infections were common in non-epidemic times. CONCLUSIONS: Malaria is once again endemic throughout the PNG highlands in areas below 1400­1500 m of altitude with a significant risk of seasonal malaria outbreaks in most area between 1400­1650 m. Ongoing control efforts are likely to result in a substantial reduction in malaria transmission and may even result in local elimination of malaria in higher lying areas.

The epidemiology of malaria in the Papua New Guinea highlands: 7. Southern Highlands Province.

As the last part of a program to survey the extent of malaria transmission in the Papua New Guinea highlands, a series of rapid malaria surveys were conducted in 2003-2004 and 2005 in different parts of Southern Highlands Province. Malaria was found to be highly endemic in Lake Kutubu (prevalence rate (PR): 17-33%), moderate to highly endemic in Erave (PR: 10-31%) and moderately endemic in low-lying parts (< 1500 m) of Poroma and Kagua (PR: 12-17%), but was rare or absent elsewhere. A reported malaria epidemic prior to the 2004 surveys could be confirmed for the Poroma (PR: 26%) but not for the lower Kagua area. In Kutubu/Erave Plasmodium falciparum was the most common cause of infection (42%), followed by P. vivax (39%) and P. malariae (16%). In other areas most infections were due to P. vivax (63%). Most infections were of low density (72% < 500/ microl) and not associated with febrile illness. Overall, malaria was only a significant source of febrile illness when prevalence rates rose above 10%, or in epidemics. However, concurrent parasitaemia led to a significant reduction in haemoglobin (Hb) level (1.2 g/dl, CI95: [1.1-1.4.], p < 0.001) and population mean Hb levels were strongly correlated with overall prevalence of malarial infections (r = -0.79, p < 0.001). Based on the survey results, areas of different malaria epidemiology are delineated and options for control in each area are discussed.

Population hemoglobin mean and anemia prevalence in Papua New Guinea: new metrics for defining malaria endemicity?

BACKGROUND: The hypothesis is that hemoglobin-based metrics are useful tools for estimating malaria endemicity and for monitoring malaria control strategies. The aim of this study is to compare population hemoglobin mean and anemia prevalence to established indicators of malaria endemicity, including parasite rates, rates of enlarged spleens in children, and records of (presumptive) malaria diagnosis among populations living with different levels of malaria transmission. METHODOLOGY/PRINCIPAL FINDINGS: Convenience sample, multisite cross-sectional household surveys conducted in Papua New Guinea. Correlations (r(2)) between population Hb mean and anemia prevalence and altitude, parasite rate, and spleen rate were investigated in children ages 2 to 10 years, and in the general population; 21,664 individuals from 156 different communities were surveyed. Altitude ranged from 5 to 2120 meters. In young children, correlations between altitude and parasite rate, population Hb mean, anemia prevalence, and spleen rate were high (r(2): -0.77, 0.73, -0.81, and -0.68; p<0.001). In the general population, correlations between altitude and population Hb mean and anemia prevalence were 0.83 and 0.85, respectively. Among young children, parasite rate correlated highly with anemia prevalence, population Hb mean, and spleen rate (r(2): 0.81, -0.81, and 0.86; p<0.001). Population Hb mean (corrected for direct altitude effects) increased with altitude, from 10.5 g/dl at <500 m to 12.8 g/dl at >1500 m (p<0.001). CONCLUSIONS/SIGNIFICANCE: In PNG, where Plasmodium vivax accounts for an important part of all malaria infections, population hemoglobin mean and anemia prevalence correlate well with altitude, parasite, and spleen rates. Hb measurement is simple and affordable, and may be a useful new tool, alone or in association with other metrics, for estimating malaria endemicity and monitoring effectiveness of malaria control programs. Further prospective studies in areas with different malaria epidemiology and different factors contributing to the burden of anemia are warranted to investigate the usefulness of Hb metrics in monitoring malaria transmission intensity.

Plasmodium falciparum resistance to anti-malarial drugs in Papua New Guinea: evaluation of a community-based approach for the molecular monitoring of resistance.

BACKGROUND: Molecular monitoring of parasite resistance has become an important complementary tool in establishing rational anti-malarial drug policies. Community surveys provide a representative sample of the parasite population and can be carried out more rapidly than accrual of samples from clinical cases, but it is not known whether the frequencies of genetic resistance markers in clinical cases differ from those in the overall population, or whether such community surveys can provide good predictions of treatment failure rates. METHODS: Between 2003 and 2005, in vivo drug efficacy of amodiaquine or chloroquine plus sulphadoxine-pyrimethamine was determined at three sites in Papua New Guinea. The genetic drug resistance profile (i.e., 33 single nucleotide polymorphisms in Plasmodium falciparum crt, mdr1, dhfr, dhps, and ATPase6) was concurrently assessed in 639 community samples collected in the catchment areas of the respective health facilities by using a DNA microarray-based method. Mutant allele and haplotype frequencies were determined and their relationship with treatment failure rates at each site in each year was investigated. RESULTS: PCR-corrected in vivo treatment failure rates were between 12% and 28% and varied by site and year with variable longitudinal trends. In the community samples, the frequencies of mutations in pfcrt and pfmdr1 were high and did not show significant changes over time. Mutant allele frequencies in pfdhfr were moderate and those in pfdhps were low. No mutations were detected in pfATPase6. There was much more variation between sites than temporal, within-site, variation in allele and haplotype frequencies. This variation did not correlate well with treatment failure rates. Allele and haplotype frequencies were very similar in clinical and community samples from the same site. CONCLUSIONS: The relationship between parasite genetics and in vivo treatment failure rate is not straightforward. The frequencies of genetic anti-malarial resistance markers appear to be very similar in community and clinical samples, but cannot be used to make precise predictions of clinical outcome. Thus, indicators based on molecular data have to be considered with caution and interpreted in the local context, especially with regard to prior drug usage and level of pre-existing immunity. Testing community samples for molecular drug resistance markers is a complementary tool that should help decision-making for the best treatment options and appropriate potential alternatives.

High sensitivity detection of Plasmodium species reveals positive correlations between infections of different species, shifts in age distribution and reduced local variation in Papua New Guinea.

BACKGROUND: When diagnosed by standard light microscopy (LM), malaria prevalence can vary significantly between sites, even at local scale, and mixed species infections are consistently less common than expect in areas co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae. The development of a high-throughput molecular species diagnostic assay now enables routine PCR-based surveillance of malaria infections in large field and intervention studies, and improves resolution of species distribution within and between communities. METHODS: This study reports differences in the prevalence of infections with all four human malarial species and of mixed infections as diagnosed by LM and post-PCR ligase detection reaction-fluorescent microsphere (LDR-FMA) assay in 15 villages in the central Sepik area of Papua New Guinea. RESULTS: Significantly higher rates of infection by P. falciparum, P. vivax, P. malariae and Plasmodium ovale were observed in LDR-FMA compared to LM diagnosis (p < 0.001). Increases were particularly pronounced for P. malariae (3.9% vs 13.4%) and P. ovale (0.0% vs 4.8%). In contrast to LM diagnosis, which suggested a significant deficit of mixed species infections, a significant excess of mixed infections over expectation was detected by LDR-FMA (p < 0.001). Age of peak prevalence shifted to older age groups in LDR-FMA diagnosed infections for P. falciparum (LM: 7-9 yrs 47.5%, LDR-FMA: 10-19 yrs 74.2%) and P. vivax (LM: 4-6 yrs 24.2%, LDR-FMA: 7-9 yrs 50.9%) but not P. malariae infections (10-19 yrs, LM: 7.7% LDR-FMA: 21.6%). Significant geographical variation in prevalence was found for all species (except for LM-diagnosed P. falciparum), with the extent of this variation greater in LDR-FMA than LM diagnosed infections (overall, 84.4% vs. 37.6%). Insecticide-treated bednet (ITN) coverage was also the dominant factor linked to geographical differences in Plasmodium species infection prevalence explaining between 60.6% - 74.5% of this variation for LDR-FMA and 81.8% - 90.0% for LM (except P. falciparum), respectively. CONCLUSION: The present study demonstrates that application of molecular diagnosis reveals patterns of malaria risk that are significantly different from those obtained by standard LM. Results provide insight relevant to design of malaria control and eradication strategies.

Evaluation of Plasmodium vivax genotyping markers for molecular monitoring in clinical trials.

BACKGROUND: Many antimalarial interventions are accompanied by molecular monitoring of parasite infections, and a number of molecular typing techniques based on different polymorphic marker genes are used. Here, we describe a genotyping technique that provides a fast and precise approach to study Plasmodium vivax infection dynamics during circumstances in which individual clones must be followed over time. The method was tested with samples from an in vivo drug efficacy study. METHODS: The sizes of polymerase chain reaction fragments were evaluated by capillary electrophoresis to determine the extent of size polymorphism for 9 potential genetic markers (5 genes of merozoite surface proteins [msp] and 4 microsatellites) in 93-108 P. vivax-positive blood samples from 3 villages in Papua New Guinea. RESULTS: The microsatellites MS16 and Pv3.27 showed the greatest diversity in the study area, with 66 and 31 different alleles, respectively, followed by 2 fragments of msp1 and 2 other microsatellites. msp3alpha, msp4, and msp5 revealed limited polymorphism. CONCLUSIONS: Even for the most diverse markers, the highest allelic frequencies reached 6% (MS16) or 13% (Pv3.27). To reduce the theoretical probability of superinfection with parasites that have the same haplotype as that detected at baseline, we propose to combine at least 2 markers for genotyping individual P. vivax infections.

Molecular markers of in vivo Plasmodium vivax resistance to amodiaquine plus sulfadoxine-pyrimethamine: mutations in pvdhfr and pvmdr1.

BACKGROUND: Molecular markers for sulfadoxine-pyrimethamine (SP) resistance in Plasmodium vivax have been reported. However, data on the molecular correlates involved in the development of resistance to 4-aminoquinolines and their association with the in vivo treatment response are scarce. METHODS: We assessed pvdhfr (F57L/I, S58R, T61M, S117T/N, and I173F/L) and pvmdr1 (Y976F and F1076L) mutations in 94 patients who received amodiaquine (AQ) plus SP in Papua New Guinea (PNG). We then investigated the association between parasite genotype and treatment response. RESULTS: The treatment failure (TF) rate reached 13%. Polymorphisms in pvdhfr F57L, S58R, T61M, and S117T/N and in pvmdr1 Y976F were detected in 60%, 67%, 20%, 40%, and 39% of the samples, respectively. The single mutant pvdhfr 57 showed the strongest association with TF (odds ratio [OR], 9.04; P= .01). The combined presence of the quadruple mutant pvdhfr 57L+58R+61M+117T and pvmdr1 mutation 976F was the best predictor of TF (OR, 8.56; P= .01). The difference in TF rates between sites was reflected in the genetic drug-resistance profile of the respective parasites. CONCLUSIONS: The present study identified a new molecular marker in pvmdr1 that is associated with the in vivo response to AQ+SP. We suggest suitable marker sets with which to monitor P. vivax resistance against AQ+SP in countries where these drugs are used.

The usefulness of twenty-four molecular markers in predicting treatment outcome with combination therapy of amodiaquine plus sulphadoxine-pyrimethamine against falciparum malaria in Papua New Guinea.

BACKGROUND: In Papua New Guinea (PNG), combination therapy with amodiaquine (AQ) or chloroquine (CQ) plus sulphadoxine-pyrimethamine (SP) was introduced as first-line treatment against uncomplicated malaria in 2000. METHODS: We assessed in vivo treatment failure rates with AQ+SP in two different areas in PNG and twenty-four molecular drug resistance markers of Plasmodium falciparum were characterized in pre-treatment samples. The aim of the study was to investigate the association between infecting genotype and treatment response in order to identify useful predictors of treatment failure with AQ+SP. RESULTS: In 2004, Day-28 treatment failure rates for AQ+SP were 29% in the Karimui and 19% in the South Wosera area, respectively. The strongest independent predictors for treatment failure with AQ+SP were pfmdr1 N86Y (OR = 7.87, p < 0.01) and pfdhps A437G (OR = 3.44, p < 0.01). Mutations found in CQ/AQ related markers pfcrt K76T, A220S, N326D, and I356L did not help to increase the predictive value, the most likely reason being that these mutations reached almost fixed levels. Though mutations in SP related markers pfdhfr S108N and C59R were not associated with treatment failure, they increased the predictive value of pfdhps A437G. The difference in treatment failure rate in the two sites was reflected in the corresponding genetic profile of the parasite populations, with significant differences seen in the allele frequencies of mutant pfmdr1 N86Y, pfmdr1 Y184F, pfcrt A220S, and pfdhps A437G. CONCLUSION: The study provides evidence for high levels of resistance to the combination regimen of AQ+SP in PNG and indicates which of the many molecular markers analysed are useful for the monitoring of parasite resistance to combinations with AQ+SP.

Low efficacy of amodiaquine or chloroquine plus sulfadoxine-pyrimethamine against Plasmodium falciparum and P. vivax malaria in Papua New Guinea.

Because of increasing resistance to 4-aminoquinolines in Papua New Guinea, combination therapy of amodiaquine (AQ) or chloroquine (CQ) plus sulfadoxine-pyrimethamine (SP) was introduced as first-line treatment against uncomplicated malaria in 2000. The purpose of this study was to monitor in vivo efficacy of the current standard combination therapy against Plasmodium falciparum and P. vivax malaria. Studies were conducted between 2003 and 2005 in the Simbu, East Sepik, and Madang Provinces in Papua New Guinea according to the revised protocol of the World Health Organization (WHO) for assessment of antimalarial drug efficacy. Children between six months and seven years of age with clinically overt and parasitologically confirmed P. falciparum or P. vivax malaria were treated according to the new policy guidelines (i.e., AQ plus SP given to patients weighing < 14 kg and CQ plus SP given to patients weighing < 14 kg). Children were monitored up to day 28 and classified according to clinical and parasitological outcome as adequate clinical and parasitological response (ACPR), early treatment failure (ETF), late clinical failure (LCF), or late parasitological failure (LPF). For P. falciparum malaria, polymerase chain reaction (PCR)-corrected treatment failure rates up to day 28 ranged between 10.3% and 28.8% for AQ plus SP and between 5.6% and 28.6% for CQ plus SP, depending on the region and the year of assessment. Overall treatment failure rate with AQ or CQ plus SP for P. vivax malaria was 12%. Our results suggest that the current first-line treatment in Papua New Guinea is not sufficiently effective. According to the new WHO guidelines for the treatment of malaria, a rate of parasitological resistance greater than 10% in the two dominant malaria species in the country justifies a change in treatment policy.

The epidemiology of malaria in the Papua New Guinea highlands: 6. Simbai and Bundi, Madang Province.

Although predominantly a lowland province, Madang also includes highland areas such as Simbai and Bundi along the northern highland fringe. While the malaria situation in the coastal lowlands has been studied in great detail, the current malaria situation in the highland fringe communities has not been studied in depth since the 1960s. A series of recent malariological surveys found that the malaria situation has changed little over the last 40 years in both Simbai and Bundi. In the Simbai area there is little malaria transmission in villages above 1400 m, with a prevalence rate (PR) of 2.5-4.2%. Below 1400 m, however, there is moderate to high transmission (PR 8.6-24.7%) with surprisingly little difference in prevalence rates between survey villages, despite large differences in altitude. Prevalence rates of malaria infection were low in all Bundi villages (2.5-8.5%) with most infections occurring in adolescents and adults, which indicates limited acquisition of effective immunity to malaria and the possibility that many infections are acquired when travelling to the highly malarious lowlands area. Based on spleen rates the lower Simbai area would be regarded as mesoendemic, and the upper Simbai and Bundi areas as hypoendemic. Only in the lower Simbai area is malaria a major cause of febrile illness. However, in all areas village mean haemoglobin (Hb) levels were highly correlated with the prevalence of malaria infections, while concurrent parasitaemia reduced individual Hb levels by 1.3 g/dl (CI95 [1.0-1.5], p < 0.001) and significantly increased the risk for moderate-to-severe anaemia (Hb < 8 g/dl) (adjusted odds ratio 5.6, CI95 [3.6-8.6], p < 0.001). Based on the survey results, areas of different malaria epidemiology are delineated and options for control in each area are discussed.

The epidemiology of malaria in the Papua New Guinea highlands: 5. Aseki, Menyamya and Wau-Bulolo, Morobe Province.

Although not strictly a highlands province, Morobe encompasses large highlands areas, the most important being Aseki, Menyamya and Wau-Bulolo. A series of rapid malaria surveys conducted in both the wet and dry seasons found malaria to be clearly endemic in areas below 1400 m in Menyamya and Wau-Bulolo, with overall prevalence rates in the wet season (25.5%, range: 9.1%-39.2%) greatly exceeding those in the dry season (8.3%, range: 2.4%-22.8%; p < 0.001). In the wet season surveys Plasmodium falciparum was the clearly predominant species, accounting for 63% of all infections. P. vivax increased in frequency in the dry season (from 27% to 46%, p < 0.001), while P. falciparum and P. malariae decreased. In line with past surveys a low prevalence of malaria was found in the Aseki area. Malaria was found to be the main source of febrile illness in the wet season with at least 60% of measured or reported fever associated with parasitaemia. Other causes of febrile illness dominated in the dry. In villages with parasite prevalence rates < 20% mean haemoglobin levels and prevalence of severe anaemia were strongly correlated with overall parasite prevalence. In addition concurrent malarial infections were associated with a strong reduction of individual haemoglobin levels (-1.2 g/dl) and there was increased risk of moderate-to-severe anaemia with concurrent malaria. Malarial infections are thus the most significant cause of febrile illness and anaemia in the highlands fringe populations in Morobe. As a consequence all villages below 1500-1600 m in Morobe Province should be included in malaria control activities.

The epidemiology of malaria in the Papua New Guinea highlands: 4. Enga Province.

Of all Papua New Guinea provinces, Enga has the largest proportion of people living at altitudes that preclude malaria transmission. However, the first systematic surveys in 1979 showed that malaria was endemic in lower-lying valleys to the north and east of the province. A series of new surveys conducted in both wet and dry seasons showed that these areas remain the main malaria focus in Enga. However, over the last 25 years the risk of malarial infections has increased substantially in areas < 1200 m (from 10% to 37-41%). In these low-lying areas people acquire substantial antimalarial immunity and most infections are asymptomatic. However, people in villages in these areas had significantly lower mean haemoglobin levels (13.0 vs 14.0 g/dl, p < 0.001) than in areas above 1200 m, where overall prevalence rates (0-9%) have not changed much. In areas between 1200 and 1600 m epidemics with parasite prevalence rates in excess of 20% have been found to occur. Malaria was a significant cause of febrile illness only in endemic areas or during outbreaks. Although rarely used, sleeping under a bednet was associated with a significant reduction in risk of malaria infection (adjusted OR = 0.45, p = 0.01). On the other hand, sleeping in garden houses away from the main villages increased the risk of malaria infection (adjusted OR = 1.6, p = 0.03). Malaria control in outlying, malarious areas of Enga province could therefore be based on the distribution of long-lasting impregnated bednets, while at the same time addressing the additional risks posed by the high mobility of many of these populations through targeted health education.