Causes of Fever in Rural Southern Laos

Murine Typhus: A Review of a Reemerging Flea-Borne Rickettsiosis with Potential for Neurologic Manifestations and Sequalae

Murine typhus is an acute febrile illness caused by Rickettsia typhi, an obligately intracellular Gram-negative coccobacillus. Rats (Rattus species) and their fleas (Xenopsylla cheopis) serve as the reservoir and vector of R. typhi, respectively. Humans become infected when R. typhi-infected flea feces are rubbed into flea bite wounds or onto mucous membranes. The disease is endemic throughout much of the world, especially in tropical and subtropical seaboard regions where rats are common. Murine typhus is reemerging as an important cause of febrile illness in Texas and Southern California, where an alternate transmission cycle likely involves opossums (Didelphis virginiana) and cat fleas (Ctenocephalides felis). Although primarily an undifferentiated febrile illness, a range of neurologic manifestations may occur, especially when treatment is delayed. Serology is the mainstay of diagnostic testing, but confirmation usually requires demonstrating seroconversion or a fourfold increase in antibody titer from acute- and convalescent-phase sera (antibodies are seldom detectable in the first week of illness). Thus, early empiric treatment with doxycycline, the drug of choice, is imperative. The purpose of this review is to highlight murine typhus as an important emerging and reemerging infectious disease, review its neurologic manifestations, and discuss areas in need of further study.

Community-level incidence and treatment seeking during febrile illness: Insights from health behaviour surveys in rural Thailand and Laos

OBJECTIVE

Critical gaps remain in understanding community perceptions and treatment-seeking behaviours in case of fever. This is especially relevant considering global antimicrobial resistance, where fever is assumed to provoke non-judicious antibiotic use. Our study objective was therefore to document the community-level incidence of fever, the resulting treatment-seeking processes, and their underlying behavioural drivers.

METHODS

In a cross-sectional observational design, we used descriptive and inferential statistics and multivariable regression analysis to estimate the population-level incidence of fever and individual and socio-economic factors associated with treatment-seeking process characteristics. We utilised a detailed publicly available survey of community-level treatment-seeking behaviour (collected in 2017/2018), comprising a representative sample of 2130 rural adults in Thailand (Chiang Rai Province) and Lao PDR (Salavan Province).

RESULTS

Fever was reported by 7.1% of the rural adult population in Chiang Rai (95% CI: 5.1%-9.0%) and 7.5% in Salavan (95% CI: 4.5%-10.5%) during a 2-month recall period. Treatment-seeking patterns varied by socio-economic characteristics like precarious employment. 69.3% (95% CI: 60.8%-77.7%) of fever episodes involved access to formal (public/private) healthcare providers, 11.0% (95% CI: 4.5%-17.5%) involved informal providers, and 24.3% (95% CI: 16.6%-32.1%) took place without either formal or informal healthcare access. Febrile patients had on average 0.39 antibiotic use episodes when accessing formal healthcare settings, compared to 0.05 otherwise (p < 0.01).

CONCLUSION

Treatment-seeking behaviour during fever varies according to population characteristics. Clinical studies would benefit from contextualising quantitative outcomes. Treatment algorithms for non-malarial febrile illnesses should involve outreach to informal healthcare and community settings to support patients in precarious circumstances, and antibiotic resistance interventions should prioritise formal healthcare facilities.

Characterizing dengue transmission in rural areas: A systematic review

Dengue has historically been considered an urban disease associated with dense human populations and the built environment. Recently, studies suggest increasing dengue virus (DENV) transmission in rural populations. It is unclear whether these reports reflect recent spread into rural areas or ongoing transmission that was previously unnoticed, and what mechanisms are driving this rural transmission. We conducted a systematic review to synthesize research on dengue in rural areas and apply this knowledge to summarize aspects of rurality used in current epidemiological studies of DENV transmission given changing and mixed environments. We described how authors defined rurality and how they defined mechanisms for rural dengue transmission. We systematically searched PubMed, Web of Science, and Embase for articles evaluating dengue prevalence or cumulative incidence in rural areas. A total of 106 articles published between 1958 and 2021 met our inclusion criteria. Overall, 56% (n = 22) of the 48 estimates that compared urban and rural settings reported rural dengue incidence as being as high or higher than in urban locations. In some rural areas, the force of infection appears to be increasing over time, as measured by increasing seroprevalence in children and thus likely decreasing age of first infection, suggesting that rural dengue transmission may be a relatively recent phenomenon. Authors characterized rural locations by many different factors, including population density and size, environmental and land use characteristics, and by comparing their context to urban areas. Hypothesized mechanisms for rural dengue transmission included travel, population size, urban infrastructure, vector and environmental factors, among other mechanisms. Strengthening our understanding of the relationship between rurality and dengue will require a more nuanced definition of rurality from the perspective of DENV transmission. Future studies should focus on characterizing details of study locations based on their environmental features, exposure histories, and movement dynamics to identify characteristics that may influence dengue transmission.

Phylogenetic Analysis of Transmission Dynamics of Dengue in Large and Small Population Centers, Northern Ecuador

Although dengue is typically considered an urban disease, rural communities are also at high risk. To clarify dynamics of dengue virus (DENV) transmission in settings with characteristics generally considered rural (e.g., lower population density, remoteness), we conducted a phylogenetic analysis in 6 communities in northwestern Ecuador. DENV RNA was detected by PCR in 121/488 serum samples collected from febrile case-patients during 2019-2021. Phylogenetic analysis of 27 samples from Ecuador and other countries in South America confirmed that DENV-1 circulated during May 2019-March 2020 and DENV-2 circulated during December 2020-July 2021. Combining locality and isolation dates, we found strong evidence that DENV entered Ecuador through the northern province of Esmeraldas. Phylogenetic patterns suggest that, within this province, communities with larger populations and commercial centers were more often the source of DENV but that smaller, remote communities also play a role in regional transmission dynamics.

Success in animal skin fashion in African countries or the boom of the wet market

The world and the way things are done have changed, from selling clothing in brick-and-mortar stores to online shopping through social media platforms. Population growth has significantly contributed to an increased clothing demand, which, in turn, has increased the demand for animal skin. Traditional markets, also known as wet markets, are considered as major zoonotic disease reservoirs due to human and animal contact. Some groups and individuals continue to believe in traditional medicine and clothing that is made from animal skin, and such beliefs are more accessible with the presence of wet markets. Hence, animal poaching and trafficking have increased to meet the high demands, primarily in the Western world. Poverty is a well-known motivation to commit a crime. Conservationists should not only look at the animal regulation site to propose a solution to animal poaching and trafficking but should also consider communal poverty. Thus, this review aimed to highlight the role of wet market and animal skin fashion on animal welfare and human health.

Unraveling the invisible leptospirosis in mainland Southeast Asia and its fate under climate change

Leptospirosis is a neglected waterborne zoonosis of growing concern in tropical and low-income regions. Endemic in Southeast Asia, its distribution and environmental factors such as climate controlling its dynamics remain poorly documented. In this paper, we investigate for the first time the current and future leptospirosis burden at a local scale in mainland Southeast Asia. We adjusted machine-learning models on incidence reports from the Thai surveillance system to identify environmental determinants of leptospirosis. The explanatory variables tested in our models included climate, topographic, land cover and soil variables. The model performing the best in cross-validation was used to estimate the current incidence regionally in Thailand, Myanmar, Cambodia, Vietnam and Laos. It then allowed to predict the spatial distribution of leptospirosis future burden from 2021 to 2100 based on an ensemble of CMIP6 climate model projections and 4 Shared Socio-economics Pathways ranging from the most optimistic to the no-climate policy outcomes (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). Leptospirosis incidence was best estimated by 10 environmental variables: four landscape-, four rainfall-, two temperature-related variables. Of all tested scenario, the worst-case scenario of climate change (SSP5-8.5) surprisingly appeared as the best-case scenario for the future of leptospirosis since it would induce a significant global decline in disease incidence in Southeast Asia mainly driven by the increasing temperatures. These global patterns are however contrasted regionally with some regions showing increased incidence in the future. Our work highlights climate and the environment as major drivers of leptospirosis incidence in Southeast Asia. Applying our model to regions where leptospirosis is not routinely monitored suggests an overlooked burden in the region. As our model focuses on leptospirosis responses to environmental drivers only, some other factors, such as poverty, lifestyle or behavioral changes, could further influence these estimated future patterns.

Outcome of Japanese Encephalitis Virus (JEV) Infection in Pediatric and Adult Patients at Mahosot Hospital, Vientiane, Lao PDR

Although Japanese encephalitis virus (JEV) infection is an important cause of acute febrile illness in Lao PDR (Laos), patient outcome has not been evaluated. We prospectively followed up 123 JEV-infected patients (70 children ≤ 15 years and 53 adults ≥ 15 years) admitted at Mahosot Hospital, Vientiane, from 2003 to 2013. Japanese encephalitis virus infection was diagnosed by the detection of anti-JEV IgM in cerebrospinal fluid and/or IgM seroconversion. Neurological sequelae were assessed using the Liverpool Outcome Score (LOS), total (maximum score = 75), and final (maximum score = 5). The median (interquartile range [IQR]) age of the patients was 12.0 (7.5-18.8) years, and 57% were male. The median (IQR) duration of patients' follow-up was 4.5 (3.2-7.3) years. Of all patients, 10/123 (8.1%) died during hospitalization, and 13/123 (10.6%) died at home after discharge, giving a mortality of 18.7% (23/123) (33 [26.8%] patients were lost to follow-up). The frequency of neurological sequelae at the last follow-up was 61.2% (48.4% in adults and 69.4% in children, P = 0.135). The proportion of patients with severe and moderate functional impairment at the last follow-up was significantly higher in children (25%) than adults (6.5%), P = 0.042. Half of the patients who were still alive at the last follow-up (67) and for whom LOS data were available (22) had improvements in their total and final LOS between discharge and the last follow-up. The total and final LOS at discharge were not significantly different between children and adults, but total LOS at the last follow-up was significantly higher in adults than children (median [IQR]: 74.5 [73-75] versus 73.0 [73-75], P = 0.019).

Screening of ectoparasites from domesticated dogs for bacterial pathogens in Vientiane, Lao PDR

Arthropod-borne diseases are widespread worldwide and are a complex interaction between animals, humans and ectoparasites. The understanding of the diversity and epidemiology of organisms transmitted by arthropod vectors, and the role of hosts and vectors in transmission of infections remain limited in Lao PDR. What knowledge does exist is primarily focused on more rural regions of the country. This study screened ectoparasites from domestic dogs in Vientiane city for the presence of bacterial pathogens of zoonotic importance. A total of 3,511 arthropod vectors were collected from 112 dogs. Vectors collected were Rhipicephalus sanguineus ticks, Ctenocephalides felis felis and Ctenocephalides felis orientis fleas and Heterodoxus spiniger lice. A sub-sample of vectors from each dog was analysed by PCR to identify the potential bacteria. From 129 vector pools, Rickettsia spp. was detected in 6.7% (7/105) pools of ticks, 86.4% (19/22) pools of fleas and both pools of lice. Sequencing analysis confirmed Rickettsia felis in 13 flea pools and one louse pool and Rickettsia asembonensis in six flea pools. Anaplasmataceae was identified in 14.3% (15/105) tick pools and 100% (22/22) flea pools. Sequencing revealed the presence of Anaplasma platys in ticks and Wolbachia pipientis in fleas. Leptospira spp. was detected in one tick and one louse pool, and Brucella spp. was detected in 12.4% (13/105) tick pools. All samples were negative for Bartonella spp., Coxiella burnetii and Borrelia burgdorferi. This is the first study providing evidence of R. asembonensis in fleas in Laos. Results from this study show arthropods are potential vectors to transmit zoonotic infection in Vientiane city, suggesting humans are at risk of zoonotic infections in the city.

Perception of health risks in Lao market vendors

Wet markets are a critical part of South‐East Asian culture and economy. However, their role in circulation and transmission of both endemic and emerging disease is a source of concern in a region considered a hotspot of disease emergence. In the Lao People's Democratic Republic (Lao PDR, Laos), live and dead wild animals are frequently found in wet markets, despite legislation against the bushmeat trade. This is generally considered to increase the risk of disease transmission and emergence, although whether or not wildlife vendors themselves have indeed increased incidence of zoonotic disease has rarely been assessed. In preparation for a future longitudinal study of market vendors investigating vendors’ exposure to zoonotic pathogens, we conducted a pilot survey of Lao market vendors of wildlife meat, livestock meat and vegetables, to identify demographic characteristics and potential control groups within markets. We also investigated baseline risk perception for infectious diseases among market vendors and assessed the association between risk perception and risk mitigation behaviours. The surveys conducted with 177 vendors revealed similar age, sex, ethnic background and geographical origin between vendor types, but differences in professional background and work history for livestock meat vendors. The perception of disease risk was very low across all vendors, as was the reported use of personal protective equipment, and the two appeared unrelated. Personal risk discounting and assumptions about transmission routes may explain this lack of association. This information will help inform the development of future research, risk communication and risk mitigation policy, especially in the light of the COVID‐19 pandemic.

Causes of fever in primary care in Southeast Asia and the performance of C-reactive protein in discriminating bacterial from viral pathogens

OBJECTIVES

This study investigated causes of fever in the primary levels of care in Southeast Asia, and evaluated whether C-reactive protein (CRP) could distinguish bacterial from viral pathogens.

METHODS

Blood and nasopharyngeal swab specimens were taken from children and adults with fever (>37.5 °C) or history of fever (<14 days) in Thailand and Myanmar.

RESULTS

Of 773 patients with at least one blood or nasopharyngeal swab specimen collected, 227 (29.4%) had a target organism detected. Influenza virus type A was detected in 85/227 cases (37.5%), followed by dengue virus (30 cases, 13.2%), respiratory syncytial virus (24 cases, 10.6%) and Leptospira spp. (nine cases, 4.0%). Clinical outcomes were similar between patients with a bacterial or a viral organism, regardless of antibiotic prescription. CRP was higher among patients with a bacterial organism compared with those with a viral organism (median 18 mg/L, interquartile range [10-49] versus 10 mg/L [≤8-22], p = 0.003), with an area under the curve of 0.65 (95% CI 0.55-0.75).

CONCLUSIONS

Serious bacterial infections requiring antibiotics are an exception rather than the rule in the first line of care. CRP testing could assist in ruling out such cases in settings where diagnostic uncertainty is high and routine antibiotic prescription is common. The original CRP randomised controlled trial was registered with ClinicalTrials.gov, number NCT02758821.

Weil's Disease: A Rare Cause of Jaundice

Weil’s disease is a complication of untreated leptospirosis and can be fatal. Awareness of leptospirosis and its hepatic manifestations are limited. We report the case of a 50-year-old man with gastrointestinal symptoms and a cholestatic pattern of liver injury diagnosed with Weil’s disease. The patient showed remarkable improvement after treatment with appropriate antibiotics with normalization of liver function in one month. This case highlights the importance of recognizing leptospirosis and its myriad presentations. 

Geospatial analysis of dengue emergence in rural areas in the Southern Province of Sri Lanka

BACKGROUND

Dengue is a major cause of acute febrile illness in Sri Lanka. Dengue has historically been considered an urban disease. In 2012-2013, we documented that acute dengue was surprisingly associated with self-reported rural residence in the Southern Province of Sri Lanka.

METHODS

Patients admitted with an acute febrile illness were enrolled from June 2012-May 2013 in a cross-sectional surveillance study at the largest tertiary care hospital in the Southern Province. Acute dengue was diagnosed by serology and virology testing. Site visits were performed to collect residential geographical coordinates. Spatial variation in odds of acute dengue was modeled using a spatial generalized additive model predicted onto a grid of coordinate pairs covering the Southern Province.

RESULTS

Of 800 patients, 333 (41.6%) had laboratory-confirmed acute dengue. Dengue was spatially heterogeneous (local probability of acute dengue 0.26 to 0.42). There were higher than average odds of acute dengue in the rural northeast of the Southern Province and lower than average odds in the urbanized southwest of the Southern Province, including the city Galle.

CONCLUSIONS

Our study further affirms the emergence of dengue in rural southern Sri Lanka and highlights both the need for real-time geospatial analyses to optimize public health activities as well as the importance of strengthening dengue surveillance in non-urban areas.

Spotted Fever Group Rickettsia Infection of Cats and Cat Fleas in Northeast Thailand

Rickettsia species cause rickettsioses, which are zoonotic diseases found worldwide, and are transmitted by arthropods such as lice, fleas, ticks, and mites. In Thailand, flea infestations are common among cats and dogs. This study aimed at determining the exposure to spotted fever group rickettsiae (SFGR) of cats in surrounding areas of Rajabhat Maha Sarakham University, Muang district, Maha Sarakham province and rickettsial infection among cat fleas, Ctenocephalides felis, collected from dogs of the surrounding area of Waeng Noi district, Khon Kaen province. Forty-two cat sera were assessed for IgG antibody titers against SFGR by a group-specific enzyme-linked immunosorbent assay. The prevalence of seroreactive cats was 4.76% (2/42). DNA preparations from 23 individual cat fleas from three dogs were assessed by Rickettsia genus-specific, group-specific, and species-specific quantitative real-time PCR (qPCR) assays. Positive results were confirmed by ompB gene fragment sequencing. Twenty-one of 23 cat fleas were positive for Rickettsia asembonensis, and the other two DNA preparations were negative for rickettsial DNA. This study's finding indicates that companion cats and dogs in Northeast Thailand are exposed to SFGR and that exposure may be due to infection with R. asembonensis, an organism known to infect humans, monkeys, and dogs. Clinicians for humans and animals in Northeast Thailand should be aware of rickettsial infections among their patients.

An observational prospective cohort study of the epidemiology of hospitalized patients with acute febrile illness in Indonesia

BACKGROUND

The epidemiology of acute febrile illness, a common cause of hospitalization in Indonesia, has not been systematically studied.

METHODOLOGY/PRINCIPAL FINDINGS

This prospective observational study enrolled febrile patients (temperature ≥38°C) aged ≥1 year from July 2013 until June 2016 at eight government referral teaching hospitals in seven provincial capitals in Indonesia. Patients were managed according to the hospital standard-of-care (SOC), and blood samples were drawn for molecular and serological assays. Clinical data, laboratory results, and specimens for additional tests were collected at enrollment, days 14-28, and at three months. Regular follow-up visits were then scheduled for every three months either until symptoms resolved or until one year. In total, this study included 1,486 adult and pediatric patients presenting with multi-organ (768, 51.7%), gastrointestinal (497, 33.0%), respiratory (114, 7.7%), constitutional (62, 4.2%), skin and soft-tissue (24, 1.6%), central nervous system (17, 1.1%), or genitourinary (4, 0.3%) manifestations. Microbiological diagnoses were found in 1,003/1,486 (67.5%) participants, of which 351/1,003 (35.0%) were not diagnosed during hospitalization using SOC diagnostic tests. Missed diagnoses included all cases caused by Rickettsia spp., chikungunya, influenza, and Seoul virus. The most common etiologic agents identified were dengue virus (467, 46.6%), Salmonella spp. (103, 10.3%), and Rickettsia spp. (103, 10.3%). The overall mortality was 89 (5.9%).

CONCLUSIONS/SIGNIFICANCE

Febrile illness in Indonesia has various microbiologic etiologies and substantial overall mortality. Diagnostic limitations and lack of epidemiologic data resulted in potentially treatable, and at times fatal, diseases being missed.

The Rickettsioses: A Practical Update

Rickettsia are small, obligately intracellular, gram-negative bacilli. They are distributed among a variety of hematophagous arthropod vectors and cause illness throughout the world. Rickettsioses present as an acute undifferentiated febrile illness and are often accompanied by headache, myalgias, and malaise. Cutaneous manifestations include rash and eschar, which both occur at varying incidence depending on the infecting species. Serology is the mainstay of diagnosis, and the indirect immunofluorescence assay is the test of choice. Reactive antibodies are seldom present during early illness, so testing should be performed on both acute-phase and convalescent-phase sera. Doxycycline is the treatment of choice.

Dengue-like illness surveillance: a two-year longitudinal survey in suburban and rural communities in the Lao People's Democratic Republic and in Thailand

Objective

This study aimed to determine the incidences of dengue-like illness (DLI), dengue virus (DENV) infection, and serotypes and to identify socio-demographical and entomological risk factors of DLI in selected suburban and rural communities in the Lao People's Democratic Republic and in Thailand.

Methods

A two-year longitudinal study was conducted in four villages during the inter-epidemic period between 2011 and 2013. Entomological surveys, semi-structured interviews of household heads and observations were conducted. Occurrences of DLI were recorded weekly using the World Health Organization’s dengue definition along with blood samples; results were compared with national surveillance dengue data. Risk factors of DLI were assessed using logistic regression.

Results

Among the 2007 people in the study, 83 DLI cases were reported: 69 in suburban Lao People's Democratic Republic, 11 in rural Thailand, three in rural Lao People's Democratic Republic and none in suburban Thailand. Four were confirmed DENV: two from suburban Lao People's Democratic Republic (both DENV-1) and two from rural Thailand (both DENV-2). Although the number of detected DLIs during the study period was low, DLI incidence was higher in the study compared to the dengue surveillance data in both countries. DLI in suburban Lao People's Democratic Republic was associated with age and occupation, but not with the number of pupae per person.

Discussion

This study highlights the importance of continuous clinical and vector surveillance for dengue to improve early detection of dengue and other mosquito-borne diseases in the region.

Study on causes of fever in primary healthcare center uncovers pathogens of public health concern in Madagascar

BACKGROUND

The increasing use of malaria diagnostic tests reveals a growing proportion of patients with fever but no malaria. Clinicians and health care workers in low-income countries have few tests to diagnose causes of fever other than malaria although several diseases share common symptoms. We propose here to assess etiologies of fever in Madagascar to ultimately improve management of febrile cases.

METHODOLOGY

Consenting febrile outpatients aged 6 months and older were recruited in 21 selected sentinel sites throughout Madagascar from April 2014 to September 2015. Standard clinical examinations were performed, and blood and upper respiratory specimens were taken for rapid diagnostic tests and molecular assays for 36 pathogens of interest for Madagascar in terms of public health, regardless of clinical status.

PRINCIPAL FINDINGS

A total of 682 febrile patients were enrolled. We detected at least one pathogen in 40.5% (276/682) of patients and 6.2% (42/682) with co-infections. Among all tested patients, 26.5% (181/682) had at least one viral infection, 17.0% (116/682) had malaria and 1.0% (7/682) presented a bacterial or a mycobacterial infection. None or very few of the highly prevalent infectious agents in Eastern Africa and Asia were detected in this study, such as zoonotic bacteria or arboviral infections.

CONCLUSIONS

These results raise questions about etiologies of fever in Malagasy communities. Nevertheless, we noted that viral infections and malaria still represent a significant proportion of causes of febrile illnesses. Interestingly our study allowed the detection of pathogens of public health interest such as Rift Valley Fever Virus but also the first case of laboratory-confirmed leptospirosis infection in Madagascar.

Febrile illness in Asia: gaps in epidemiology, diagnosis and management for informing health policy

BACKGROUND

Increasing evidence is becoming available on the aetiology and management of fevers in Asia; the importance of these fevers has increased with the decline in the incidence of malaria.

AIMS

To conduct a narrative review of the epidemiology and management of fevers in South and South-East Asia and to highlight gaps in our knowledge that impair evidence-based health policy decisions.

SOURCES

A narrative review of papers published since 2012 on developments in fever epidemiology, diagnosis and treatment in South and South-East Asia. The papers that the authors felt were pivotal, from their personal perspectives, are discussed.

CONTENT

We identified 100 studies. Among the 30 studies (30%)-including both children and adults-that investigated three or more pathogens, the most frequently reported fever aetiology was dengue (reported by 15, 50%), followed by leptospirosis (eight, 27%), scrub typhus (seven, 23%) and Salmonella serovar Typhi (six, 20%). Among four studies investigating three or more pathogens in children, dengue and Staphylococcus aureus were the most frequent, followed by non-typhoidal Salmonella spp, Streptococcus pneumoniae, Salmonella serovar Typhi, and Orientia tsutsugamushi. Increased awareness is needed that rickettsial pathogens are common but do not respond to cephalosporins, and that alternative therapies, such as tetracyclines, are required.

IMPLICATIONS

Many key gaps remain, and consensus guidelines for study design are needed to aid comparative understanding of the epidemiology of fevers. More investment in developing accurate and affordable diagnostic tests for rural Asia and independent evaluation of those already on the market are needed. Treatment algorithms, including simple biomarker assays, appropriate for empirical therapy of fevers in different areas of rural Asia should be a major aim of fever research. Enhanced antimicrobial resistance (AMR) surveillance and openly accessible databases of geography-specific AMR data would inform policy on empirical and specific therapy. More investment in innovative strategies facilitating infectious disease surveillance in remote rural communities would be an important component of poverty reduction and improving public health.

Molecular epidemiology of dengue viruses in three provinces of Lao PDR, 2006-2010

Few data on dengue epidemiology are available for Lao PDR. Here, we provide information on the complexity of dengue epidemiology in the country, demonstrating dynamic circulation that varies over space and time, according to serotype. We recruited 1,912 consenting patients presenting with WHO dengue criteria at Mahosot Hospital, Vientiane (central Laos), between 2006 and 2010. Between 2008 and 2010, 1,413 patients with undifferentiated fever were also recruited at Luang Namtha (LNT) Provincial Hospital (northern Laos) and 555 at Salavan (SV) Provincial Hospital (southern Laos). We report significant variations in Dengue virus (DENV) circulation between the three sites. Peaks of DENV infection were observed in the rainy seasons, although 11% of confirmed cases in the provinces and 4.6% in the capital were detected during the dry and cool seasons (between December and February). Four DENV serotypes were detected among the 867 RT-PCR positive patients: 76.9% DENV-1, 9.6% DENV-2, 7.7% DENV-4 and 5.3% DENV-3. DENV-1 was the predominant serotype throughout the study except in LNT in 2008 and 2009 when it was DENV-2. Before July 2009, DENV-2 was not detected in SV and only rarely detected in Vientiane. DENV-3 and DENV-4 were commonly detected in Vientiane, before 2008 for DENV-4 and after 2009 for DENV-3. The phylogenetic analyses of DENV envelope sequences suggest concurrent multiple introductions of new strains as well as active DENV circulation throughout Laos and with neighboring countries. It is therefore of great importance to develop and strengthen a year-round nation-wide surveillance network in order to collect data that would allow anticipation of public health issues caused by the occurrence of large dengue outbreaks.

Dengue is a mosquito-borne disease that can be caused by 4 viruses. It is a flu-like disease but can sometime be more severe and cause hemorrhage or death. An estimated 390 million people are infected every year, mainly in the Western Pacific and in South-East Asia. In Laos, where our study was conducted from 2006 to 2010, little was known on the circulation of the different dengue viruses. A total of 1,912 patients were recruited at Mahosot Hospital, Vientiane (central Laos), 1,413 patients at Luang Namtha Provincial Hospital (northern Laos) and 555 at Salavan Provincial Hospital (southern Laos). Although most Dengue virus infections were detected during rainy seasons (where mosquitoes are the most active) in all three provinces, some patients were also infected during the dryer months. All 4 dengue viruses were detected with different distributions: mostly type 1 in the capital and in the South, and type 1 and 2 in equal proportion in the north. Type 3 and 4 were not detected in Luang Namtha and rarely in Salavan. Comparison of Dengue virus sequences from Laos with sequences collected worldwide showed an active year-round circulation of dengue within Laos and with neighboring countries. It is hence of great importance to develop and strengthen a year-round nation-wide surveillance network in order to collect data that would allow anticipation of public health issues caused by the occurrence of large dengue outbreaks.

Reducing Uncertainty for Acute Febrile Illness in Resource-Limited Settings: The Current Diagnostic Landscape

AbstractDiagnosing the cause of acute febrile illness in resource-limited settings is important-to give the correct antimicrobials to patients who need them, to prevent unnecessary antimicrobial use, to detect emerging infectious diseases early, and to guide vaccine deployment. A variety of approaches are yielding more rapid and accurate tests that can detect more pathogens in a wider variety of settings. After decades of slow progress in diagnostics for acute febrile illness in resource-limited settings, a wave of converging advancements will enable clinicians in resource-limited settings to reduce uncertainty for the diagnosis of acute febrile illness.

Scrub typhus: risks, diagnostic issues, and management challenges

Scrub typhus is an acute febrile illness in the “tsutsugamushi triangle”, transmitted by chiggers that can be treated effectively if detected early. Laboratory testing, including molecular and serological assays, is needed for confirming the diagnosis, especially in the absence of the pathognomonic eschar. In this review, factors that play a role in disease occurrence and clinical clues for diagnosis, in addition to risk factors contributing to disease severity, including mortality, are discussed in detail. Moreover, issues related to diagnostic assays, treatment, and mixed infections are also enumerated and described.

Bacterial arthropod-borne diseases in West Africa

Arthropods such as ticks, lice, fleas and mites are excellent vectors for many pathogenic agents including bacteria, protozoa and viruses to animals. Moreover, many of these pathogens can also be accidentally transmitted to humans throughout the world. Bacterial vector-borne diseases seem to be numerous and very important in human pathology, however, they are often ignored and are not well known. Yet they are in a phase of geographic expansion and play an important role in the etiology of febrile episodes in regions of Africa. Since the introduction of molecular techniques, the presence of these pathogens has been confirmed in various samples from arthropods and animals, and more rarely from human samples in West Africa. In this review, the aim is to summarize the latest information about vector-borne bacteria, focusing on West Africa from 2000 until today in order to better understand the epidemiological risks associated with these arthropods. This will allow health and veterinary authorities to develop a strategy for surveillance of arthropods and bacterial disease in order to protect people and animals.

Effects of socio-demographic characteristics and household water management on Aedes aegypti production in suburban and rural villages in Laos and Thailand

BACKGROUND

Dengue fever is a mosquito-borne disease accounting for 50-100 million annual cases globally. Laos and Thailand are countries in south-east Asia where the disease is endemic in both urban and rural areas. Household water storage containers, which are favourable breeding sites for dengue mosquitoes, are common in these areas, due to intermittent or limited access to water supply. This study assessed the effect of household water management and socio-demographic risk factors on Aedes aegypti infestation of water storage containers.

METHODS

A cross-sectional survey of 239 households in Laos (124 suburban and 115 rural), and 248 households in Thailand (127 suburban and 121 rural) was conducted. Entomological surveys alongside semi-structured interviews and observations were conducted to obtain information on Ae. aegypti infestation, socio-demographic factors and water management. Zero-inflated negative binomial regression models were used to assess risk factors associated with Ae. aegypti pupal infestation.

RESULTS

Household water management rather than socio-demographic factors were more likely to be associated with the infestation of water containers with Ae. aegypti pupae. Factors that was significantly associated with Ae. aegypti infestation were tanks, less frequent cleaning of containers, containers without lids, and containers located outdoors or in toilets/bathrooms.

CONCLUSIONS

Associations between Ae. aegypti pupae infestation, household water management, and socio-demographic factors were found, with risk factors for Ae. aegypti infestation being specific to each study setting. Most of the containers did not have lids, larvicides, such as temephos was seldom used, and containers were not cleaned regularly; factors are facilitating dengue vector proliferation. It is recommended that, in Lao villages, health messages should promote proper use and maintenance of tightly fitted lids, and temephos in tanks, which were the most infested containers. Recommendations for Thailand are that small water containers should be cleaned weekly. Furthermore, in addition to health messages on dengue control provided to communities, attention should be paid to larval control for indoor containers in rural villages. Temephos or other immature control measures such as the use of pyriproxyfen, antilarval bacteria, or larvivorous fish should be used where temephos resistance is prevalent. Dengue control is not possible without additional adult mosquito control and community participation.

Causes and outcomes of sepsis in southeast Asia: a multinational multicentre cross-sectional study

BACKGROUND

Improved understanding of pathogens that cause sepsis would aid management and antimicrobial selection. In this study, we aimed to identify the causative pathogens of sepsis in southeast Asia.

METHODS

In this multinational multicentre cross-sectional study of community-acquired sepsis and severe sepsis, we prospectively recruited children (age ≥30 days and <18 years) and adults (age ≥18 years) at 13 public hospitals in Indonesia (n=3), Thailand (n=4), and Vietnam (n=6). Hospitalised patients with suspected or documented community-acquired infection, with at least three diagnostic criteria for sepsis according to the Surviving Sepsis Campaign 2012, and within 24 h of admission were enrolled. Blood from every patient, and nasopharyngeal swab, urine, stool, and cerebrospinal fluid, if indicated, were collected for reference diagnostic tests to identify causative pathogens. We report causative pathogens of sepsis and 28-day mortality. We also estimate mortality associated with enrolment with severe sepsis. This study was registered with ClinicalTrials.gov, number NCT02157259.

FINDINGS

From Dec 16, 2013, to Dec 14, 2015, 4736 patients were screened and 1578 patients (763 children and 815 adults) were enrolled. Dengue viruses (n=122 [8%]), Leptospira spp (n=95 [6%]), rickettsial pathogens (n=96 [6%]), Escherichia coli (n=76 [5%]), and influenza viruses (n=65 [4%]) were commonly identified in both age groups; whereas Plasmodium spp (n=12 [1%]) and Salmonella enterica serovar Typhi (n=3 [0·2%]) were rarely observed. Emerging pathogens identified included hantaviruses (n=28 [2%]), non-typhoidal Salmonella spp (n=21 [1%]), Streptococcus suis (n=18 [1%]), Acinetobacter spp (n=12 [1%]), and Burkholderia pseudomallei (n=5 [<1%]). 28-day mortality occurred in 14 (2%) of 731 children with known statuses and 108 (13%) of 804 adults. Severe sepsis was identified on enrolment in 194 (28%) of 731 children and 546 (68%) of 804 adults, and was associated with increased mortality (adjusted odds ratio 5·3, 95% CI 2·7-10·4; p<0·001).

INTERPRETATION

Sepsis in southeast Asia is caused by a wide range of known and emerging pathogens, and is associated with substantial mortality.

FUNDING

National Cancer Institute, National Institute of Allergy and Infectious Diseases, National Institutes of Health, USA, and Wellcome Trust, UK.

Use of eschar swabbing for the molecular diagnosis and genotyping of Orientia tsutsugamushi causing scrub typhus in Quang Nam province, Vietnam

BACKGROUND

Scrub typhus is a rickettsiosis which is caused by Orientia tsutsugamushi and occurs throughout the Asia-Pacific region. Molecular diagnosis of rickettsioses using eschar swabs has recently emerged, and may be very useful for the diagnosis of these diseases in tropical settings.

METHODOLOGY/PRINCIPAL FINDINGS

Quantitative polymerase chain reaction (qPCR) was used to detect O. tsutsugamushi DNA in whole blood and eschar swab specimens of 67 patients who were clinically suspected of scrub typhus in Quang Nam province, Vietnam. Among the 20 patients for whom both eschar and whole blood were obtained, 17 (85%) of the eschar specimens and 5 (25%) of the whole blood specimens tested positive for O. tsutsugamushi. Genetic analysis of the 56-kDa TSA gene sequences demonstrated that the 14 sequences obtained in this study, including 12 eschar swabs and 2 whole blood specimens, were related to 4 groups: Karp, Kawasaki, Gilliam (JG-v and TG-v) and TA716. The majority (9/14; 64.4%) of contemporary O. tsutsugamushi genotypes in Quang Nam province were related to the Karp group.

CONCLUSIONS

These results suggest that polyclonal antigen pools used for serological testing in the future should contain at least Karp, Kawasaki, Gilliam and TA716 antigens for Vietnamese patients, as well as patients who have traveled to Vietnam. qPCR after eschar swabbing should be considered for molecular diagnosis of scrub typhus in endemic patients as well as in travelers, since it is easy to perform and appears very useful for the rapid detection of Orientia tsutsugamushi in the early phase of infection.

Temperature of a Dengue Rapid Diagnostic Test under Tropical Climatic Conditions: A Follow Up Study

The Dengue Duo Rapid Diagnostic Test (SD Dengue RDT) has good specificity and sensitivity for dengue diagnosis in rural tropical areas. In a previous study, using four control sera, we demonstrated that that the diagnostic accuracy of these RDTs remains stable after long-term storage at high temperatures. We extended this study by testing sera from 119 febrile patients collected between July-November 2012 at Salavan Provincial Hospital (southern Laos) with RDTs stored for 6 months at 4°C, 35° and in a hut (miniature traditional house) at Lao ambient temperatures. The dengue NS1 antigen results from RDTs stored at 35°C and in the hut demonstrated 100% agreement with those stored at 4°C. However, lower positive percent agreements, with broad 95%CI, were observed for the tests: IgM, 60% (14.7–94.7) and 40% (5.3–85.3) for RDTs store at 35°C and in the hut, compared to those stored at 4°C, respectively. This study strenghtens the evidence of the robustness of the NS1 antigen detection RDT for the diagnosis of dengue after storage at tropical temperatures.

Emergence of Epidemic Dengue-1 Virus in the Southern Province of Sri Lanka

BACKGROUND

Dengue is a frequent cause of acute febrile illness with an expanding global distribution. Since the 1960s, dengue in Sri Lanka has been documented primarily along the heavily urbanized western coast with periodic shifting of serotypes. Outbreaks from 2005-2008 were attributed to a new clade of DENV-3 and more recently to a newly introduced genotype of DENV-1. In 2007, we conducted etiologic surveillance of acute febrile illness in the Southern Province and confirmed dengue in only 6.3% of febrile patients, with no cases of DENV-1 identified. To re-evaluate the importance of dengue as an etiology of acute febrile illness in this region, we renewed fever surveillance in the Southern Province to newly identify and characterize dengue.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional surveillance study was conducted at the largest tertiary care hospital in the Southern Province from 2012-2013. A total of 976 patients hospitalized with acute undifferentiated fever were enrolled, with 64.3% male and 31.4% children. Convalescent blood samples were collected from 877 (89.6%). Dengue virus isolation, dengue RT-PCR, and paired IgG ELISA were performed. Acute dengue was confirmed as the etiology for 388 (39.8%) of 976 hospitalizations, with most cases (291, 75.0%) confirmed virologically and by multiple methods. Among 351 cases of virologically confirmed dengue, 320 (91.2%) were due to DENV-1. Acute dengue was associated with self-reported rural residence, travel, and months having greatest rainfall. Sequencing of selected dengue viruses revealed that sequences were most closely related to those described from China and Southeast Asia, not nearby India.

CONCLUSIONS/SIGNIFICANCE

We describe the first epidemic of DENV-1 in the Southern Province of Sri Lanka in a population known to be susceptible to this serotype because of prior study. Dengue accounted for 40% of acute febrile illnesses in the current study. The emergence of DENV-1 as the foremost serotype in this densely populated but agrarian population highlights the changing epidemiology of dengue and the need for continued surveillance and prevention.

Leptospirosis: risk factors and management challenges in developing countries

Leptospirosis is a widespread bacterial zoonosis with highest burden in low-income populations living in tropical and subtropical regions, both in urban and in rural environments. Rodents are known as the main reservoir animals, but other mammals may also significantly contribute to human infections in some settings. Clinical presentation of leptospirosis is nonspecific and variable, and most of the early signs and symptoms point to the so-called “acute fever of unknown origin”, a major diagnostic challenge in tropical and subtropical areas. However, leptospirosis can rapidly evolve to life-threatening complications, especially if left untreated. There is a need for good awareness of leptospirosis and rapid antibiotic treatment based on clinical and epidemiological suspicion. Severe leptospirosis cases include renal and/or respiratory failure and shock, necessitating intensive care, also seldom available or with limited capacity. Confirmation of leptospirosis relies on biological diagnosis, which unfortunately uses tricky methods seldom available. This biological confirmation, however, is essential for surveillance and public health purpose. A good knowledge of leptospirosis epidemiology (eg, the reservoir animals involved, the Leptospira strains circulating, the seasonal and geographical patterns, and specific populations at risk) can be achieved through adequate surveillance and diagnosis. This can pave the way to prevention and intervention strategies and in turn alleviate the toll leptospirosis takes on affected populations. Over the past few years, leptospirosis has been increasingly recognized, as the need for multidisciplinary approaches in a One-Health perspective has been acknowledged, raising hope to successfully tackle the challenges of this zoonosis.

Challenges in the Etiology and Diagnosis of Acute Febrile Illness in Children in Low- and Middle-Income Countries

Acute febrile illness is a common cause of hospital admission, and its associated infectious causes contribute to substantial morbidity and death among children worldwide, especially in low- and middle-income countries. Declining transmission of malaria in many regions, combined with the increasing use of rapid diagnostic tests for malaria, has led to the increasing recognition of leptospirosis, rickettsioses, respiratory viruses, and arboviruses as etiologic agents of fevers. However, clinical discrimination between these etiologies can be difficult. Overtreatment with antimalarial drugs is common, even in the setting of a negative test result, as is overtreatment with empiric antibacterial drugs. Viral etiologies remain underrecognized and poorly investigated. More-sensitive diagnostics have led to additional dilemmas in discriminating whether a positive test result reflects a causative pathogen. Here, we review and summarize the current epidemiology and focus particularly on children and the challenges for future research.

Asymptomatic Plasmodium infections in 18 villages of southern Savannakhet Province, Lao PDR (Laos)

Background

A large fraction of Plasmodium infections do not cause clinical signs and symptoms of disease and persist at densities in blood that are not detectable by microscopy or rapid diagnostic tests. These infections may be critical as a transmission reservoir in areas of low malaria endemicity. Understanding the epidemiology of these infections would be helpful for malaria elimination.

Methods

A cross-sectional survey was conducted in Thapangthong and Nong Districts of Savannakhet Province, Lao PDR, to determine the prevalence of parasitaemia. A total of 888 blood samples were collected from afebrile volunteers aged ≥15 years in 18 villages during March and July 2015. Plasmodium infections were diagnosed by rapid diagnostic tests (RDT) and high volume, ultra-sensitive quantitative polymerase chain reaction (uPCR).

Results

uPCR detected Plasmodium infections in 175 of 888 samples (20 %). The species distribution was Plasmodiumfalciparum 3.6 % (32/888), Plasmodium vivax 11.1 % (99/888), mixed infections with P. falciparum and P. vivax 1.6 % (14/888) and Plasmodium of undetermined species 3.4 % (30/888). RDT identified only 2 % (18/888) positive cases. Using uPCR as reference, the sensitivity and specificity of RDTs were 28 and 100 %, respectively, in detecting P. falciparum infections, and 3 and 99 % in detecting asymptomatic P. vivax infections. The K13 kelch propeller domain C580Y mutation, associated with reduced susceptibility to artemisinin derivatives, was found in 75 % (12/18) of P. falciparum isolates from Thapangthong and in 7 % (2/28) from Nong (p < 0.001). In a multivariate analysis, males were more likely to have P. vivax infections [adjusted odds ratio (aOR) 4.76 (95 % CI 2.84–8.00)] while older villagers were at lower risk for parasitaemia [aOR for increasing age 0.98 (95 % CI 0.96–0.99)].

Conclusion

There is a high prevalence of asymptomatic Plasmodium infections in southern Savannakhet. Artemisinin-resistant P. falciparum strains form an increasing proportion of the parasite population in Thapangthong District and are already present in the more remote Nong District. This worrying trend has wider implications for Laos and could reverse the gains achieved by the successful control of malaria in Laos and the Greater Mekong Sub-region (GMS). Rapid elimination of P. falciparum has to be a top priority in Laos as well as in the wider GMS.

The Aetiologies and Impact of Fever in Pregnant Inpatients in Vientiane, Laos

INTRODUCTION

Laos has the highest maternal mortality ratio in mainland Southeast Asia and a high incidence of infectious diseases. Globally, malaria has been the pathogen most intensively investigated in relation to impact on pregnancy, but there has been relatively little research on the aetiology and impact of other diseases. We therefore aimed to determine the causes and impact of fever in pregnant women admitted to two central hospitals in Vientiane City, Lao PDR (Laos).

MATERIALS AND METHODS

This hospital-based prospective study was conducted in Mahosot Hospital and the Mother and Child Hospital, Vientiane, between 2006 and 2010, with the aim to recruit 250 consenting pregnant women admitted with tympanic temperature ≥37.5°C. Primary outcome was the cause of fever and secondary outcomes were pregnancy outcomes. Specific investigations (culture, antigen, molecular and serological tests) were performed to investigate causes of fever. After discharge, all pregnant women were asked to return for review and convalescence serum on day 10-14 and were monitored until delivery.

PRINCIPLE FINDINGS

250 pregnant women were recruited to this study between February 2006 and November 2010. Fifty percent were pregnant for the first time. Their median (range) gestational age on admission was 24 (4-43) weeks. The median (range) tympanic admission temperature was 38.5°C (37.5-40.5°C). Fifteen percent of patients stated that they had taken antibiotics before admission. Headache, myalgia, back pain and arthralgia were described by >60% of patients and 149 (60%) were given a laboratory diagnosis. Of those with confirmed diagnoses, 132 (53%) had a single disease and 17 (7%) had apparent mixed diseases. Among those who had a single disease, dengue fever was the most common diagnosis, followed by pyelonephritis, scrub typhus, murine typhus and typhoid. Patients were also diagnosed with tuberculosis, appendicitis, Staphylococcus aureus septicemia, leptospirosis, Japanese encephalitis virus infection and Plasmodium falciparum malaria. Severe consequences, including maternal death, miscarriage, stillbirth, low birth weight and preterm birth, were found among 28 (78%) mothers with dengue fever, rickettsioses and typhoid.

CONCLUSION

Fevers other than malaria, such as dengue, pyelonephritis, rickettsioses and typhoid are common causes of fever during pregnancy in the Asian tropics. Further investigations of their impact in the community on maternal death, fetal loss, vertical transmission, low birth weight and preterm birth are needed.

Multiple Pathogens Including Potential New Species in Tick Vectors in Côte d'Ivoire

BACKGROUND

Our study aimed to assess the presence of different pathogens in ticks collected in two regions in Côte d'Ivoire.

METHODOLOGY/PRINCIPAL FINDINGS

Real-time PCR and standard PCR assays coupled to sequencing were used. Three hundred and seventy eight (378) ticks (170 Amblyomma variegatum, 161 Rhipicepalus microplus, 3 Rhipicephalus senegalensis, 27 Hyalomma truncatum, 16 Hyalomma marginatum rufipes, and 1 Hyalomma impressum) were identified and analyzed. We identified as pathogenic bacteria, Rickettsia africae in Am. variegatum (90%), Rh. microplus (10%) and Hyalomma spp. (9%), Rickettsia aeschlimannii in Hyalomma spp. (23%), Rickettsia massiliae in Rh. senegalensis (33%) as well as Coxiella burnetii in 0.2%, Borrelia sp. in 0.2%, Anaplasma centrale in 0.2%, Anaplasma marginale in 0.5%, and Ehrlichia ruminantium in 0.5% of all ticks. Potential new species of Borrelia, Anaplasma, and Wolbachia were detected. Candidatus Borrelia africana and Candidatus Borrelia ivorensis (detected in three ticks) are phylogenetically distant from both the relapsing fever group and Lyme disease group borreliae; both were detected in Am. variegatum. Four new genotypes of bacteria from the Anaplasmataceae family were identified, namely Candidatus Anaplasma ivorensis (detected in three ticks), Candidatus Ehrlichia urmitei (in nine ticks), Candidatus Ehrlichia rustica (in four ticks), and Candidatus Wolbachia ivorensis (in one tick).

CONCLUSIONS/SIGNIFICANCE

For the first time, we demonstrate the presence of different pathogens such as R. aeschlimannii, C. burnetii, Borrelia sp., A. centrale, A. marginale, and E. ruminantium in ticks in Côte d'Ivoire as well as potential new species of unknown pathogenicity.