Southern Lao PDR Research Articles

Contribution to the genus Clypeocaenis Soldán, 1978 (Ephemeroptera: Caenidae) from Lao People’s Democratic Republic with a key to Oriental species

Larvae of Clypeocaenis laosensis sp. nov. were collected from the Xe Nou River, Xe Bang Hieng River, and Tha Hao Stream in central and southern Lao PDR. This investigation also encompassed the examination of eggs extracted from female larvae, and we give here the first egg description of Cl. multisetosa Soldán, 1978 and Cl. oligosetosa Soldán, 1983. Clypeocaenis laosensis sp. nov. is closely related with Cl. gayathri Balasubramanian & Muthukatturaja, 2020 and Cl. kaveri Balasubramanian & Muthukatturaja, 2021. The new species is distinguishable from other Clypeocaenis species by specific morphological traits. These include the number of setae on the clypeus, the morphology of the labial palpus, the length of marginal setae on the middle and hind femora, setae of the transverse row on the forefemur, and body surface microtrichia. A detailed comparison of the morphological features between this new species and its closely related species is provided. Furthermore, the first-time reporting of Cl. multisetosa and Cl. oligosetosa in Lao PDR expands the known Caenidae diversity in the country to five species. A key to the nymphs of the Oriental species of Clypeocaenis is provided.

Steatotic liver disease among lean and non-lean individuals in Southern Lao PDR: a cross-sectional study of risk factors

Background Steatotic liver disease (SLD) prevalence is rising worldwide, linked to insulin resistance and obesity. SLD prevalence can surpass 10% even among those with normal weight. In Lao People’s Democratic Republic (Lao PDR), where Opisthorchis viverrini (OV) trematode infection and type 2 diabetes mellitus (T2DM) are common, infection related liver morbidity such as cholangiocarcinoma (CCA) is high, but data on SLD prevalence is lacking. The objective of this study was to estimate the prevalence and explore determinants of SLD in rural southern Lao PDR for lean and non-lean populations. Method A cross-sectional community-based study assessed SLD prevalence using abdominal ultrasonography (US). Factors investigated for association with SLD were identified by interview, serological tests (Hepatitis B surface antigen (HBsAg); lipids and HbA1c), anthropometrical measurements, and parasitological assessments (OV infection). Uni- and multivariable logistic regression analyses with SLD as endpoint were conducted separately for lean (body mass index (BMI) <23.0 kg/m2) and non-lean (BMI ≥ 23.0 kg/m2) participants. Result 2,826 participants were included. SLD prevalence was 27.1% (95% confidence interval (95% CI) 24.0%−30.4%), higher among non-lean (39.8%) than lean individuals (17.4%). Lean individuals with OV infection had a statistically significant association with lower odds of SLD (adjusted odds ratio (aOR) 0.49, 95% CI 0.33 − 0.73). T2DM showed a significant positive association with SLD in both lean (aOR 3.58, 95% CI 2.28 − 5.63) and non-lean individuals (aOR 3.31, 95% CI 2.31 − 4.74) while dyslipidemia was significantly associated only in the non-lean group (aOR 1.83, 95% CI 1.09 − 3.07). Females participants exhibited elevated odds of SLD in both lean (aOR 1.43, 95% CI 1.02 − 2.01) and non-lean SLD (aOR 1.50, 95% CI 1.12 − 2.01). Conclusion SLD prevalence is notably high among Laotian adults in rural areas, particularly in females and in non-lean individuals. Lean individuals with OV infection exhibited lower SLD prevalence. SLD was more prevalent in individuals with T2DM, independent of BMI. SLD adds to the burden of infection-related liver morbidity in Lao PDR.

Species of Diaspididae (Hemiptera: Coccomorpha) on citrus in southern Lao PDR, new records for Việt Nam, and revised records for Indochina

The Diaspididae (Hemiptera: Coccomorpha), also known as armoured scale insects, is a diverse family of obligate, phytophagous parasites that include major economic pests of terrestrial plants. There are over 2,700 diaspidid species, about 116 of which have been recorded worldwide feeding on species and hybrids of citrus. Citrus is widely cultivated in the Lao People’s Democratic Republic (Lao PDR) and has been promoted by the country’s government as a poverty alleviation crop. However, little is known about the pest and disease issues faced by farmers of this crop. To help address this, in 2018 we conducted surveys of diaspidids on citrus in southern Lao PDR and found 14 species infesting citrus growing in orchards and home gardens. Identifications were based on morphological features of adult females and 28S, COI and COII DNA sequences. An identification key to the species based on morphological characters is provided. Records of diaspidid species on citrus in Myanmar, Thailand and Cambodia are updated, and records from Peninsular Malaysia provided. The first record on citrus of a Pseudaulacaspis species in Indochina is reported from Việt Nam, and an undescribed species of Pseudaonidia is recorded on citrus in Lao PDR.

Low Prevalence of Schistosoma mekongi Infection and High Prevalence of Other Helminth Infections among Domestic Animals in Southern Lao People's Democratic Republic.

The prevalence of Schistosoma mekongi in humans in the Lao People's Democratic Republic (Lao PDR) has been relatively well monitored and has decreased due to effective interventions such as preventative chemotherapy with mass drug administration of praziquantel and community awareness programs. However, the prevalence among potential domestic reservoir animals remains broadly unclear, except for a few villages in the endemic area. Therefore, we conducted S. mekongi surveys for the domestic animals that had contact with Mekong River water. We conducted a cross-sectional study of the domestic animals in the seven sentinel villages in the Khong and Mounlapamok Districts of Champasak Province in southern Lao PDR in 2018 by random sampling with a statistically reliable sample size. Stool samples of the five predominant domestic animal species, cattle (n = 160), pig (n = 154), buffalo (n = 149), dog (n = 143), and goat (n = 85), were collected and examined using parasitological FECT method and the LAMP technique. The microscopic analysis did not detect any eggs of S. mekongi in the stool samples of any animal species. However, S. mekongi DNA was detected by the LAMP test in dog stool samples (0.7%; 1/143). On the other hand, the prevalence of other helminths was quite high and heterogeneous among animal species and sentinel sites by the microscopic analysis. These findings suggested that an intervention for S. mekongi infection should focus solely on human populations. However, periodic surveillance for S. mekongi infection among dogs should be conducted to monitor a possible resurgence of S. mekongi infection in the domestic animal population.

A Spatial Autocorrelation Method for Taenia solium Risk Mapping: The Case of Lao PDR.

The World Health Organization has identified Taenia solium mapping tools as an important development for intensifying control in hyperendemic areas. Taenia solium has also been identified as a priority by the Lao PDR government. There is a limited understanding of the distribution of T. solium due to inherent diagnostic challenges. Global and local autocorrelation statistics were applied to available risk factor data sourced from national censuses to map the risk of Taenia solium in Lao PDR. Approximately 50% of villages could be considered hot spots for one or more risk factors. Different risk factor hot spots co-occurred in 30% of villages. Twenty per cent of villages were classified as hot spots for the proportion of households owning pigs and another risk factor. Northern Lao PDR was the dominant high-risk area. This is consistent with passive reports, limited surveys, and anecdotal reports. One smaller area in southern Lao PDR was also identified as high-risk. This is of particular interest because T. solium has not previously been investigated in this area. The methods applied provide a simple, rapid, and versatile approach that allows endemic countries to begin mapping the risk of T. solium at a sub-national level.

Projected seasonal changes in future rainfall erosivity over the Lancang-Mekong River basin under the CMIP6 scenarios

Climate change is a driver of soil erosion, but the future projections of seasonal rainfall erosivity variability and spatial distribution over the Lancang-Mekong River Basin (LMRB) are still not well understood. Based on the bias-corrected precipitation data from five General Circulation Models (GCMs) in the sixth phase of the Coupled Model Intercomparison Project (CMIP6), the impacts of future climate change on the seasonal rainfall erosivity over the LMRB were assessed using three widely applied empirical daily rainfall erosivity models under three combined scenarios of the Shared Socioeconomic Pathways and the Representative Concentration Pathways (SSP1-RCP2.6, SSP3- RCP7.0 and SSP5- RCP8.5). The results show that rainfall erosivity would generally increase in the near term (2030–2060) and far term (2070–2100), and more ensemble members agree with the increase in rainfall erosivity, especially under the high emission scenarios in the far term. In the near term, the ensemble mean of basin-wide rainfall erosivity would increase by 2.5%-8.7% compared to the baseline period (1980–2010), while in the far term, the ensemble mean would increase by 12.2%-31.0%. Seasonal variations in rainfall erosivity show that summer rainfall erosivity from June to August accounts for more than two-thirds of the total annual rainfall erosivity. Although the projected basin-wide average summer rainfall erosivity would increase, the mid-southern basin in Thailand and southern Lao PDR would experience a decrease. For rainfall erosivity from March to May, large areas except for the mountainous part of China would also experience a decrease in seasonal rainfall erosivity. The projected changes in rainfall erosivity can contribute to a better understanding of soil erosion risk under climate change across the LMRB.

A NEW SPECIES OF THE GENUS Oligodon FITZINGER, 1826 (REPTILIA: COLUBRIDAE) FROM SOUTHERN LAOS

A new species of the genus Oligodon Fitzinger, 1826, is described based on two specimens originating from Champasak Province in southern Lao PDR. This species differs from congeners occurring in the Indochinese Region by possessing 15 dorsal scale rows at midbody, an unforked hemipenis, an entire cloacal plate, a relatively low number of ventral plates (150–159), and a dorsal pattern made of 29–30 pale (cream in life or pale yellowish-brown in preservative) crossbands on the body that are narrowly edged with blackish-brown. We compare the new species with other species of the Indochinese Peninsula and China that also have 15 dorsal scale rows, especially O. inornatus (Boulenger, 1914) and O. kampucheaensis Neang, Grismer &amp; Daltry, 2012. Finally, we provide an updated list of the Oligodon species of Laos and an identification key to these species.

Performance and adoption of submergence-tolerant TDK1-Sub1 rice in southern Lao PDR

Under short-term submergence (7–15 days), submergence-tolerant rice genotypes (e.g. TDK1-Sub1) have been reported to be higher yielding than their intolerant equivalents without the Sub1 gene. This paper examined whether TDK1-Sub1 was superior to Other locally-preferred genotypes, with and without submergence, using 66 on-farm comparisons in southern Lao PDR. Data were examined for 2 genotype categories (TDK1-Sub1, Other) in 3 environment groups (Favourable, Drought, and Submergence), with 22 farms per group used as replicates. Farmers saved seeds of TDK1-Sub1, planted it again in flood-prone fields, and disseminated its seeds to relatives, neighbours and friends, but they did not do so in areas with lower flood risk. Grain yield was generally higher under Favourable conditions (2.42 ​t ​ha−1) than under Submergence (1.94 ​t ​ha−1) or Drought (1.90 ​t ​ha−1). Under Submergence, the grain yield of TDK1-Sub1 (2.22 ​t ​ha−1) was significantly higher than the Other genotype (1.65 ​t ​ha−1; P ​< ​0.10). Conversely, under Drought, the grain yield of TDK1-Sub1 (1.58 ​t ​ha−1) was significantly lower than the Other genotype (2.22 ​t ​ha−1; P ​< ​0.10). Submergence-tolerant genotypes should enhance system intensification and food security in submergence-prone areas, but yields of other locally-preferred genotypes were more stable in the absence of submergence, especially under late-season drought. Current efforts to introgress additional resistances into submergence-tolerant genotypes are worthwhile, to reduce any downside risk in the absence of flooding. Nevertheless, for Lao PDR and others who prefer glutinous rice, the Sub1 gene should be introgressed into the best-adapted glutinous rice genotypes, which already possess other resistances.

Perspectives of health and community stakeholders on community-delivered models of malaria elimination in Lao People's Democratic Republic: A qualitative study.

In the Lao People's Democratic Republic (Lao PDR), village health volunteers play an important role in providing health services including those to reduce the burden of malaria. Over the last two decades, the volunteer network has expanded to bring malaria services closer to communities and contributed to the reduction of malaria cases. However, as malaria test positivity rates decreased, many volunteers have lost motivation to continue providing routine malaria services, and other services they provide may not reflect growing healthcare demands for common diseases in the community. This study explored the perspectives, knowledge and inputs of key health stakeholders and community members in southern Lao PDR on community-delivered models in order to refine the volunteer model in the context of Lao PDR's primary health care sector and malaria elimination goals. Semi-structured interviews with multi-level health stakeholders, participatory workshops with community leaders, and focus group discussions with community members and current village health volunteers were conducted. Deductive followed by inductive thematic analysis was used to explore and categorise stakeholders' perspectives on community-delivered models for malaria elimination. Both stakeholders and community members agreed that village health volunteers are essential providers of malaria services in rural communities. Apart from malaria, community members identified dengue, diarrhoea, influenza, skin infections and tuberculosis as priorities (in descending order of importance) and requested community-based primary health care for these diseases. Stakeholders and community members suggested integrating prevention, diagnosis, and treatment services for the five priority diseases into the current malaria volunteer model. A divergence was identified between community members' expectations of health services and the services currently provided by village health volunteers. Stakeholders proposed an integrated model of healthcare to meet the needs of the community and help to maintain volunteers' motivation and the long-term sustainability of the role. An evidence-based, integrated community-delivered model of healthcare should be developed to balance the needs of both community members and stakeholders, with consideration of available resources and current health policies in Lao PDR.

Nutrients enhance genotype and water responses in rainfed lowland rice in southern Lao PDR

Food security in Lao PDR, a small nation in southeast Asia categorized as low-income food-deficit, is strongly dependent on the success of the rainfed lowland rice crop in the southern provinces. Soils there are sandy in texture, low in water-holding capacity, and low in pH and available nutrients. Farmers are reluctant to apply recommended fertilizer doses, as rainfall and crop responses are unreliable. This paper examines fertilizer response, and considers opportunities to improve the risk profile. The effects of 12 fertilizer-water-genotype treatment combinations were examined across 60 locations, and combined analysis of variance and pattern analysis was used to examine crop response and its relationship to soil fertility, genotype, and climatic variability. The results showed there was little relationship between soil test and grain yield in unfertilized plots, suggesting nutrient release and capture were more important than soil nutrient concentration, so integrative measures of soil nutrient release should be more promising. Despite low yield in the absence of applied nutrients (0.89–2.66, mean 2.18 t ha-1), NPK alone increased yields by 1.0 t ha-1 on average (1.48–3.86, mean 3.12 t ha-1), while water and genotype together with NPK increased yields by up to a further 1.0 t ha-1 (1.95–4.76, mean 3.42 t ha-1). Fertilizer responses were greater and more reliable when soil nutrient buffering capacity was greater, which, together with seasonal expectations, could be used to better inform decisions on fertilizer application in relation to risk. A longer-term and moderate input strategy was proposed in order to gradually improve fine-fraction SOC, soil nutrient buffering, and soil microbial biomass, in order to improve soil nutrient and water retention and release characteristics. This strategy should be evaluated in future research.

Investigating the Impact of Huanglongbing in Citrus in Southern Lao PDR

Citrus has been promoted in the Lao People’s Democratic Republic (Lao PDR) as a poverty reduction strategy for at least two decades. However, citrus trees have been in widespread decline for no less than ten years. Since 2010, the authors have observed symptoms on citrus trees consistent with the bacterial disease huanglongbing (HLB). These symptoms included asymmetric leaf mottle, small lopsided fruit, poor fruit production and tree decline. The authors then initiated a long-term study on the occurrence of HLB in southern Lao PDR. Samples of leaf mid-ribs were collected from citrus trees in orchards, nurseries, and backyards across four provinces: Champasak, Sekong, Salavan, and Savannakhet. The presence of ‘Candidatus Liberibacter asiaticus’, the putative causal agent of the Asiatic form of HLB, was confirmed in 59 of 109 samples collected in all four provinces. The Asian citrus psyllid, the vector of ‘Ca. L. asiaticus’, was also observed on citrus trees and tested positive for the pathogen. The implications of these findings for citrus production in Lao PDR are discussed.&nbsp;

First report of Phyllosticta spp. associated with banana freckle disease in southern Lao PDR

A survey of small-holder banana farms was undertaken in February/March 2019 in Savannakhet, Salavan, Sekong and Champasak provinces in southern Lao People’s Democratic Republic (Lao PDR) to establish which banana leaf pathogens were present. Twenty-five farms were visited, seven different cultivars were assessed, and 13 leaf samples with characteristic symptoms of banana freckle disease collected. Phyllosticta musarum was detected on the variety ‘Kuay Nam’ in each of the four provinces surveyed. Phyllosticta cavendishii was detected in Salavan, Sekong and Champasak. Phyllosticta musaechinesis was recorded from Champasak. This is the first time these three species have been recorded associated with banana freckle disease in the Lao PDR.

Population size estimation of seasonal forest-going populations in southern Lao PDR

Forest-going populations are key to malaria transmission in the Greater Mekong Sub-region (GMS) and are therefore targeted for elimination efforts. Estimating the size of this population is essential for programs to assess, track and achieve their elimination goals. Leveraging data from three cross-sectional household surveys and one survey among forest-goers, the size of this high-risk population in a southern province of Lao PDR between December 2017 and November 2018 was estimated by two methods: population-based household surveys and capture–recapture. During the first month of the dry season, the first month of the rainy season, and the last month of the rainy season, respectively, 16.2% [14.7; 17.7], 9.3% [7.2; 11.3], and 5.3% [4.4; 6.1] of the adult population were estimated to have engaged in forest-going activities. The capture–recapture method estimated a total population size of 18,426 [16,529; 20,669] forest-goers, meaning 61.0% [54.2; 67.9] of the adult population had engaged in forest-going activities over the 12-month study period. This study demonstrates two methods for population size estimation to inform malaria research and programming. The seasonality and turnover within this forest-going population provide unique opportunities and challenges for control programs across the GMS as they work towards malaria elimination.

AGRICULTURE TRANSITION AND WOMEN’S DECISION-MAKING POWER IN COFFEE-FARMING HOUSEHOLDS IN LAO PDR

The Lao government introduced a new period of economic liberalisation with the New Economic Mechanism (NEM) in 1986. The present study examines whether market liberalisation and women’s participation translated into changes in women’s decision-making power in the coffee growing region of the Bolaven Plateau in southern Lao PDR. While women have always been involved in coffee farming, their participation increased when the more labour-intensive arabica coffee plants were introduced to replace the less popular robusta variety in the region. Drawing on quantitative and qualitative data, the study examines gender decision-making within coffee-farming households. The findings show an increase in women’s participation in decision-making with the introduction of the arabica coffee plants; however, men still hold higher decision-making power in farming households. While the NEM has brought about economic growth and provided better livelihoods for coffee farmers, this has not necessarily translated into women’s empowerment. Economic growth is not enough to bring about gender equality, and there is still a need for specific policy interventions.

First report of citrus exocortis viroid, citrus bent leaf viroid, hop stunt viroid and citrus dwarfing viroid in Lao PDR

Citrus exocortis viroid, citrus bent leaf viroid, hop stunt viroid and citrus dwarfing viroid were detected for the first time in Lao PDR. Samples were collected from citrus trees across southern Lao PDR for laboratory testing in Australia. RNA was extracted and amplified using quantitative reverse transcription polymerase chain reaction (qRT-PCR); viroid identities were confirmed by sequencing.

Gendered Roles in Agrarian Transition: A Study of Lowland Rice Farming in Lao PDR

Traditional lifestyles of lowland rice farmers of the southern provinces of Lao People’s Democratic Republic are rapidly changing, due to two important trends. Firstly, there is a push towards modernization and commercialization of farming. Secondly, though farmers still focus on rice farming as a key activity, there is an increasing move towards diversification of livelihoods. The changes have seen the uptake of non-rice crops, livestock husbandry and forest and river utilization; as well as non-farming activities. This has influenced gender relations, impacting household agricultural production decisions and amplified transitional trends. To explore the processes, we analyzed data from a study of innovation adoption amongst rice farmers in southern Lao PDR. The study revealed nuances of gender-based differences in the priorities and attitudes towards farming and off-farm activities, as well as differences in behaviour related to the adoption of new practices. Women were more focused on non-farming practices and considered engaging in the modern, non-traditional, economy more so than men. Women also reported experiencing greater challenges when engaging and trading in the agricultural marketplace. The study supports the importance of taking a gendered approach to understanding the inherent complexities within agrarian change.

Combining species distribution modeling and distance sampling to assess wildlife population size: A case study with the northern yellow-cheeked gibbon (Nomascus annamensis).

Population size and distribution data for wildlife species play an important role in conservation and management, especially for endangered species. However, scientists seriously lack data on the population status of many species. The northern yellow-cheeked gibbon (Nomascus annamensis) is found in southern Lao PDR, central Vietnam, and northeastern Cambodia. The population of the species has significantly declined due to hunting, habitat loss, and the wildlife trade. To examine the population size and distribution of N. annamensis, we conducted a field survey in Song Thanh Nature Reserve, Quang Nam Province, central Vietnam from February to April 2019 using the audio point count method. We combined Distance Sampling and Ecological Niche Modeling to estimate the population of the gibbons. Results showed that the total suitable area for the gibbons was about 302.32 km2 , with the two most important variables of the habitat model being the distance-to-villages and forest type. We detected 36 gibbon groups through field surveys and estimated 443 (95% CI, 278-707) gibbon groups in Song Thanh Nature Reserve. Our results indicate that the gibbon population in Song Thanh Nature Reserve is the largest known population of N. annamensis in Vietnam. In addition, our study was the first to combine species distribution modeling with distance sampling to estimate gibbon density and population size. This approach might be useful in surveying and monitoring gibbon populations because it takes imperfect detection probability into account in estimating gibbon population density while estimating the area of potential habitat using environmental variables.

Study protocol for a cluster-randomized split-plot design trial to assess the effectiveness of targeted active malaria case detection among high-risk populations in Southern Lao PDR (the AcME-Lao study)

Introduction: Novel interventions are needed to accelerate malaria elimination, especially in areas where asymptomatic parasitemia is common, and where transmission generally occurs outside of village-based settings. Testing of community members linked to a person with clinical illness (reactive case detection, RACD) has not shown effectiveness in prior studies due to the limited sensitivity of current point-of-care tests. This study aims to assess the effectiveness of active case finding in village-based and forested-based settings using novel high-sensitivity rapid diagnostic tests in Lao People’s Democratic Republic (Lao PDR). Methods and analysis: This study is a cluster-randomized split-plot design trial. The interventions include village-based mass test and treat (MTAT), focal test and treat in high-risk populations (FTAT), and the combination of these approaches, using high-sensitivity rapid diagnostic tests (HS-RDTs) to asses P. falciparum infection status. Within four districts in Champasak province, Lao PDR fourteen health center-catchment areas will be randomized to either FTAT or control; and within these HCCAs, 56 villages will be randomized to either MTAT or control. In intervention areas, FTAT will be conducted by community-based peer navigators on a routine basis, and three separate rounds of MTAT are planned. The primary study outcome will be PCR-based Plasmodium falciparum prevalence after one year of implementation. Secondary outcomes include malaria incidence; interventional coverage; operational feasibility and acceptability; and cost and cost- effectiveness. Ethics and dissemination: Findings will be reported on clinicaltrials.gov, in peer-reviewed publications and through stakeholder meetings with Ministry of Health and community leaders in Lao PDR and throughout the Greater Mekong Subregion. Trial registration: clinicaltrials.gov NCT03783299 (21/12/2018)

Clonality, spatial structure, and pathogenic variation in Fusarium fujikuroifrom rain-fed rice in southern Laos.

Bakanae disease, caused by the fungal phytopathogen Fusarium fujikuroi, can be detected in most rice (Oryza sativa L.) growing areas worldwide. In this study, we investigated the population structure of this fungus in southern Lao PDR, a country located near the geographic origin of rice domestication. Microsatellites (SSRs) and mating type (MAT) analyses, pathogenicity and fungicide sensitivity tests were integrated in the study. The first key finding is that the population genetic structure of F. fujikuroi in Lao PDR is consistent with high clonal reproduction. Indeed, (i) “true” clones were identified; (ii) within populations, MAT types were frequently skewed from 1:1 ratio, (iii) linkage disequilibrium (among SSRs as also among SSRs and MAT) was present, and (iv) gene-flow between opposite MAT types within the same population is restricted. The presence of genetic divergence among areas and populations and the occurrence of positive spatial autocorrelation of genetic variation, indicate that migration is restricted, and that genetic drift plays an important role in the evolution of this fungus. Two main well-defined groups of isolates were detected (FST = 0.213) that display a non-random spatial distribution. They differ in the ability to induce seedlings death but not seedlings elongation (the typical Bakanae symptom) suggesting that the pathogen’s ability to induce the two symptoms is under different genetic control. Finally, we compared two agroecosystems with contrasting characteristics: low-input and traditional (Lao PDR) vs high-input and modern (Italy). We found differences in the level of population structuring and of spatial autocorrelation. This suggests that the evolutionary potential of the fungus not only depends on its intrinsic characteristics, but is strongly influenced by other external factors, most likely by the dynamics of infested seed exchange. Thus, quarantine and chemical treatments are a way to reduce population connectivity and hence the evolutionary potential of this pathogen.

Study protocol for a cluster-randomized split-plot design trial to assess the effectiveness of targeted active malaria case detection among high-risk populations in Southern Lao PDR (the AcME-Lao study).

Introduction: Novel interventions are needed to accelerate malaria elimination, especially in areas where asymptomatic parasitemia is common, and where transmission generally occurs outside of village-based settings. Testing of community members linked to a person with clinical illness (reactive case detection, RACD) has not shown effectiveness in prior studies due to the limited sensitivity of current point-of-care tests. This study aims to assess the effectiveness of active case finding in village-based and forested-based settings using novel high-sensitivity rapid diagnostic tests in Lao People's Democratic Republic (Lao PDR). Methods and analysis: This study is a cluster-randomized split-plot design trial. The interventions include village-based mass test and treat (MTAT), focal test and treat in high-risk populations (FTAT), and the combination of these approaches, using high-sensitivity rapid diagnostic tests (HS-RDTs) to asses P. falciparum infection status. Within four districts in Champasak province, Lao PDR fourteen health center-catchment areas will be randomized to either FTAT or control; and within these HCCAs, 56 villages will be randomized to either MTAT or control. In intervention areas, FTAT will be conducted by community-based peer navigators on a routine basis, and three separate rounds of MTAT are planned. The primary study outcome will be PCR-based Plasmodium falciparum prevalence after one year of implementation. Secondary outcomes include malaria incidence; interventional coverage; operational feasibility and acceptability; and cost and cost- effectiveness. Ethics and dissemination: Findings will be reported on clinicaltrials.gov, in peer-reviewed publications and through stakeholder meetings with Ministry of Health and community leaders in Lao PDR and throughout the Greater Mekong Subregion. Trial registration: clinicaltrials.gov NCT03783299 (21/12/2018).