Concealed for a Long Time on the Marches of Empires: Hepatitis B Virus Genotype I

Genotype I, the penultimate HBV genotype to date, was granted the status of a bona fide genotype only in the XXIst century after some hesitations. The reason for these hesitations was that genotype I is a complex recombinant virus formed with segments from three original genotypes, A, C, and G. It was estimated that genotype I is responsible for only an infinitesimal fraction (<1.0%) of the chronic HBV infection burden worldwide. Furthermore, most probably due to its recent discovery and rarity, the natural history of infection with genotype I is poorly known in comparison with those of genotypes B or C that predominate in their area of circulation. Overall, genotype I is a minor genotype infecting ethnic minorities. It is endemic to the Southeast Asian Massif or Eastern Zomia, a vast mountainous or hilly region of 2.5 million km2 spreading from Eastern India to China, inhabited by a little more than 100 million persons belonging primarily to ethnic minorities speaking various types of languages (Tibeto-Burman, Austroasiatic, and Tai-Kadai) who managed to escape the authority of central states during historical times. Genotype I consists of two subtypes: I1, present in China, Laos, Thailand, and Vietnam; and I2, encountered in India, Laos, and Vietnam.

Epidemiology and serotype distribution of Streptococcus pneumoniae carriage among influenza-like illness cases in metropolitan Vientiane, Lao PDR: a community-based cohort study

Background

Data on the epidemiology of Streptococcus pneumoniae among influenza-like illness (ILI) cases, particularly in low- and middle-income countries are scarce. This study assessed the prevalence, risk factors and serotype distribution of S. pneumoniae carriage among ILI cases in metropolitan Vientiane, Lao People's Democratic Republic. The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced among infants in October 2013.

Methods

Active ILI surveillance was conducted through weekly phone calls in an open community-based cohort study (April 2015-February 2019), involving 5,690 participants from 1,142 randomly selected households. Participants reporting ILI symptoms provided a nasopharyngeal swab and answered a questionnaire. S. pneumoniae and serotype pneumococcal-positive samples were screened by Multiplex PCR assays. Chi-squared tests and generalized linear mixed models were used to test for variables associated with pneumococcal positivity.

Results

Among 1,621 ILI episodes, 269 (16.6%) tested positive for nasopharyngeal pneumococcal carriage, with the highest prevalence (55.4%) in children under 5 years. Pneumococcal carriage was significantly associated with concurrent detection of Hemophilus influenzae (adjusted odds ratio [aOR]: 6.93; 95% CI: 2.10-22.9) and exposure to household cigarette smoke (aOR: 1.65; 95% CI: 1.07-2.54). PCV13 serotypes accounted for 37.8% of all pneumococcal isolates. Detection of PCV13 serotypes among ILI cases aged under 5 years declined significantly between 2015/16 and 2018/19.

Conclusions

Community-based surveillance of S. pneumoniae among ILI cases complement surveillance at healthcare facilities to provide a more complete picture of pneumococcal carriage. Our findings contribute also to the growing body of evidence on the effects of PCV13 introduction on circulating serotypes and their potential replacement.

Estimating the burden of hepatitis B virus infection in Laos between 2020 and 2021: A cross-sectional seroprevalence survey

BACKGROUND

Laos is considered highly endemic for persistent infection with hepatitis B virus (HBV). To eliminate this burden, it has gradually implemented universal anti-hepatitis B immunisation of newborns over the past two decades.

METHODS

Using VIKIA® HBsAg, a rapid test for the qualitative detection of the HBV surface antigen, we conducted between Sep 1st, 2020 and Aug 31st, 2021 the largest prospective prevalence survey ever in Laos. This survey included blood donors (BD, n = 42,277), patients attending care in capital and provincial hospitals (n = 37,347) including attending mothers (n = 20,548), HIV-infected patients (n = 7439, recruited from 2009 to 2020), students from the Health Sciences University (n = 609), and outpatients (n = 350) coming for diagnosis at the Center Infectiology Lao-Christophe Mérieux in Vientiane. In total, 88,022 persons were tested, representing approximately 1.22% of the national population. To reach a reasonable estimate of HBsAg prevalence in Laos, we segmented the population according to three variables, age (≤20 years as a cut-off), sex, and geographical origin. BD values were used to estimate HBsAg prevalence in patients aged <20 while hospital survey prevalence was used to estimate the prevalence in those aged older than 20 years.

FINDINGS

We observed an HBsAg seroprevalence ranging from 2.6% in blood donors to 8.0% in HIV-infected patients. In BD, men were significantly more at risk to be carriers than women (RR = 1.2, P = 0.00063). For BD, attending mothers, or HIV-infected patients, HBsAg was significantly more prevalent in northern Laos (5.1-8.4%) than in central (2.0-8.1%) or southern parts of the country (2.2-6.9%), thereby delineating a North-to-South gradient.

INTERPRETATION

We considered that HBsAg prevalence probably ranges between 5.0% and 6.0% of the total population. Thus, we consider that Laos may no longer be highly endemic for chronic HBV infection but rather a country with intermediate endemicity.

FUNDING

The funding sources were the Agence Universitaire de la Francophonie, the French Government, the French Institute for Sustainable Development (IRD), and European Union's Horizon 2020 Marie Sklodowska-Curie Actions (MSCA) - Research and Innovation Staff Exchange - (RISE) under grant agreement N° 823935.

Efficacy of careHPV™ human papillomavirus screening versus conventional cytology tests for the detection of precancerous and cancerous cervical lesions among women living with HIV-1 in Lao People's Democratic Republic

BACKGROUND

In the Lao People's Democratic Republic (Lao PDR), cervical cancer is the third leading cause of women cancer.

AIMS

The objective of this cross-sectional study was to compare the efficacy of careHPV™ test versus conventional Pap smear or Siriraj liquid-based cytology in the detection of cervical cancer in women living with human immunodeficiency virus type 1 (HIV-1).

MATERIALS & METHODS

Overall, 631 women consented to participate. Four cervical specimens were taken for the purpose of conventional Pap smear, Siriraj liquid-based cytology, careHPV™ test, and HPV-16 genotyping. The exact McNemar test was used to compare the efficacy and diagnostic performance of the tests.

RESULTS

Of the 631 women with follow-up, 331 were human papillomavirus (HPV) negative. High-grade squamous intraepithelial lesions were found in 37 women, biopsy-proven high-grade cervical intraepithelial neoplasia in 50 women, and invasive carcinoma in seven women. The proportion of women with high-grade cervical lesion or carcinoma detected after abnormal careHPV™ test was higher (6.02%; 95% confidence interval [CI]: 4.4-8.1) than that detected by conventional Pap smear (4.59%; 95% CI: 3.2-6.5). careHPV™ and HPV-16 genotyping had, respectively, the highest sensitivity (80.8%; 95% CI: 67.4-89.5) and specificity (92.2%; 95% CI: 89.8-94.2). HPV-16 was the most frequently detected genotype.

CONCLUSIONS

careHPV™ test represents a screening option in Lao PDR, particularly in women living with HIV-1 because of higher prevalence of chronic HPV in this population.

Factors associated with cervical cancer screening among women aged 25-60 years in Lao People's Democratic Republic

BACKGROUND

Despite cervical cancer being a major public health concern in the Lao People's Democratic Republic (Lao PDR), screening coverage is very low. The reasons and factors for this are unknown. This study aimed to identify factors associated with uptake of cervical cancer screening among women aged 25-60 years.

METHODS

The case-control study was conducted among women aged 25-60 years in Vientiane Capital and Luang Prabang province from March 15 to May 31, 2018. A total of 360 women were included in the study, a ratio of two controls per case. The cases were women who had undergone cervical cancer screening over the last five years. The controls were women who had never been screened or screened more than five years before, matched to the cases with residency and age (± five years). The cases were selected from central and provincial hospitals and the controls from the same community and districts where the cases resided. Conditional logistic regression was used to determine factors associated with cervical cancer screening.

RESULTS

The mean age was 42.37±9.4 years (range: 25-60), 66.67% were women from Vientiane Capital, and 86.11% were married. The common reasons for not being screened were the absence of clinical signs and symptoms (45.28%) followed by never having heard about cervical cancer (13.33%). In the multivariable analyses, we found that having sexually transmitted infections (AOR = 3.93; 95% CI = 1.92-8.05), receiving recommendations for screening from health workers (AOR = 3.85; 95% CI = 1.90-7.78), a high score for knowledge (AOR = 7.90; 95% CI = 2.43-25.69) and attitude towards cervical cancer prevention and treatment (AOR = 2.26; 95% CI = 1.18-7.16), and having a car to travel (AOR = 2.97; 95% CI = 1.44-6.11) had a positive impact on undergoing cervical cancer screening.

CONCLUSION

Gynecological consultations, increased knowledge and positive attitudes result in women undergoing screening. Therefore, health education and advocacy for cervical cancer prevention should be provided to women.

Hepatitis B virus in Lao dentists: A cross-sectional serological study

INTRODUCTION AND OBJECTIVES

Hepatitis B virus (HBV) is endemic in Lao PDR, with up to 10% chronic infections in adults. Dentists have high risk of exposure and transmission to their patients. The aim was to investigate the serological profiles of vaccination, exposure and susceptibility to HBV. In addition, we determined the knowledge, attitude and practice (KAP) of Lao dentists toward HBV.

MATERIALS AND METHODS

Dentists and dental assistants were recruited from 186 private dental clinics in Vientiane Capital. They completed a KAP questionnaire and serum was tested by ELISA for HBV markers (anti-HB surface antigen, anti-core antigen, HBV surface antigen).

RESULTS

206 dentists and 111 dental workers aged between 18-63 years were included. Serology data showed that 37.8% had previous exposure (49.0% of males and 32.4% of females) and 5.0% were chronically infected (7.7% of males and 3.8% of females). Less than 15% had serological evidence of vaccination and 66.8% were unprotected against infection. Knowledge of HBV was mostly low, for example 61.8% were aware of the childhood HBV vaccine. Just over half said that they should give dental care to HBV carriers. About one quarter reported accidental blood exposure during the last 6 months but knowledge about procedures after exposure was low.

CONCLUSIONS

Lao dentists are at high risk of occupational exposure to HBV but have low awareness and serological protection. There is a need to introduce mandatory vaccination, to strengthen occupational health in health care providers and to further develop the academic curricula of dental students.

A pilot study to investigate the risk of SARS-CoV-2 household transmission following hospital discharge of confirmed cases in Vientiane Capital, Lao PDR

Background

Global guidelines from the World Health Organization on discharging patients diagnosed with COVID-19 changed in 2021 to a symptom-based rather than negative PCR-based approach. Studies have shown that shedding of viable virus continues for approximately eight days after symptom onset in most patients. In Vientiane, Laos, until now, patients diagnosed with asymptomatic or mild COVID-19 are hospitalised for 2 weeks and then, if they still test PCR positive for SARS-CoV-2, stay for a further week in a designated quarantine hotel before being discharged home.

Objective

The aim of this pilot study was to investigate the risk of transmission of SARS-CoV-2 to household contacts of discharged patients who are still PCR-positive following 2-3 weeks quarantine in Vientiane, Lao PDR.

Methods

Adult participants, who were resident in Vientiane Capital and who were about to be discharged from hospital (after 2 weeks hospitalisation), or from a quarantine hotel, following a further one-week quarantine, were screened to assess eligibility for the study. The household of each case was visited a maximum of 48 hours before or up to 24 hours after the participant was discharged and a nasopharyngeal swab was taken from all household members. Repeat nasopharyngeal swabs from cases and contacts were taken on day 7 and day 14 after discharge home of each case.

Results

Between 20th May 2021 and 27th August 2021, 55 cases and 84 contacts in 27 households were enrolled in the study. The median [range] age of all 139 included participants was 26.5 years [3 months to 83 years] and 83 (60%) were female. By household, the median [range] number of cases and contacts were 1 [1-6] and 3 [1-13] respectively. At discharge home 32/48 (67%) cases tested positive for SARS-CoV-2. By day 7 11 of 47 cases (23%) still tested positive for SARS-CoV-2 by PCR and by day 14 this number was 2/24 (8%). No contacts tested positive during follow up and the numbers tested at the time of discharge of the case, 7 days later and 2 weeks later were 56, 57 and 37 respectively. Loss to follow up at day 7 and day 14 ranged from 15-50% (participants not at home at the time of visits).

Conclusion

In this pilot study we found no evidence of onward transmission of SARS-CoV-2 to contacts of cases discharged home with a positive PCR result. This suggests the current discharge policy for mild to moderate COVID-19 case following 2 weeks in hospital in the Lao PDR is safe.

First insights into the genetic characteristics and drug resistance of Mycobacterium tuberculosis population collected during the first national tuberculosis prevalence survey of Lao PDR (2010-2011)

Background

In Lao People’s Democratic Republic (PDR), tuberculosis (TB) prevalence was estimated at 540/100,000 in 2011. Nevertheless, little is known about the genetic characteristics and anti-TB drug resistance of the Mycobacterium tuberculosis population. The main objective of this work was to study the genetic characteristics and drug resistance of M. tuberculosis population collected during the first National TB Prevalence Survey (TBPS) of Lao PDR (2010–2011).

Methods

Two hundred and twenty two isolates collected during TBPS (2010–2011) were analyzed with the GenoType MTBDRplus test for M. tuberculosis identification and drug resistance detection. Then, 206 of the 222 isolates were characterized by spoligotyping and MIRU-VNTR typing.

Results

Among the 222 M. tuberculosis isolates, 11 were mono-resistant to isoniazid and 2 were resistant to isoniazid and rifampicin (MDR-TB), using the GenoType MTBDRplus test. Among the 202 genetically characterized isolates, the East African-Indian (EAI) family was predominant (76.7%) followed by the Beijing (14.4%) and T (5.5%) families. EAI isolates came from all the country provinces, whereas Beijing isolates were found mainly in the northern and central provinces. A higher proportion of Beijing isolates was observed in people younger than 35 years compared to EAI. Moreover, the percentage of drug resistance was higher among Beijing (17.2%) than EAI (5.2%) isolates, and the two MDR-TB isolates belonged to the Beijing family. Combined analysis of the MIRU-VNTR and spoligotyping results (n = 202 isolates) revealed an estimated clustering rate of 11% and the occurrence of mini-outbreaks of drug-resistant TB caused by Beijing genotypes.

Conclusions

The EAI family, the ancient and endemic family in Asia, is predominant in Lao PDR whereas the prevalence of Beijing, the most harmful M. tuberculosis family for humans, is still low, differently from neighboring countries. However, its association with drug resistance, its presence in young patients and its potential association with recent transmission suggest that the Beijing family could change TB epidemiological pattern in Lao PDR. Therefore, efficient TB control and surveillance systems must be maintained and reinforced to prevent the emergence of highly transmissible and drug-resistant strains in Lao PDR, as observed in neighboring countries.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4435-z) contains supplementary material, which is available to authorized users.

Perinatal hepatitis B virus transmission in Lao PDR: A prospective cohort study

Background

Mother-to-child transmission of hepatitis B virus (HBV) is the main cause of new infections worldwide. We aimed at assessing the percentage of infants successfully immunized in two major hospitals in Vientiane, Lao PDR where HB immune globulin (HBIg) is not available.

Methods

We studied a prospective cohort of chronically HBV infected pregnant women and their infants until 6 months post-partum from January 2015 to March 2017. All infants received HB vaccine at birth and 6, 10 and 14 weeks thereafter, and HBV status was assessed at 6 months of age. HBV surface gene sequencing was performed in infected mother-infant pairs.

Results

Of 153 mothers with HB surface antigen (HBsAg), 60 (39%) had detectable serum HBe antigen (HBeAg). HBeAg positive pregnant women were younger than those negative (median age 26 versus 28 years; p = 0.02) and had a significantly higher HBV viral load at delivery (median 8.0 versus 4.0 log₁₀ IU/mL, p <0.001). Among the 120 infants assessed at 6 months of age, 5 (4%) were positive for HBsAg and had detectable HBV viral load by polymerase chain reaction. All were born to mothers with HBeAg and viral load >8.5 log₁₀ IU/mL. However, only four (3.3%, 95% CI 0.5% to 7.0%) had a virus strain closely related to their mother’s strain. HBV surface gene mutations were detected in 4 of the 5 infected infants. Anti-HBs antibody levels were below 10 IU/L in 10 (9%) uninfected infants at 6 months of age.

Conclusions

Mother-to-child transmission occurred less frequently than expected without the use of HBIg. Adding HBIg and/or maternal antiviral prophylaxis may have prevented some of these infections. The observation of unsatisfactory levels of anti-HBs antibodies in 9% of the uninfected infants at 6 months highlights the need for improvement of the universal immunization procedures.

"Epidemiology and aetiology of influenza-like illness among households in metropolitan Vientiane, Lao PDR": A prospective, community-based cohort study

Respiratory diseases are a major contributor to morbidity and mortality in many tropical countries, including Lao PDR. However, little has been published regarding viral or bacterial pathogens that can contribute to influenza-like illness (ILI) in a community setting. We report on the results of a community-based surveillance that prospectively monitored the incidence of ILI and its causative pathogens in Vientiane capital in Lao PDR. A cohort of 995 households, including 4885 study participants, were followed-up between May 2015 and May 2016. Nasopharyngeal swabs, throat swabs, and sputum specimens were collected from ILI cases identified through active case-finding. Real-Time PCR was used to test nasopharyngeal swabs for 21 respiratory pathogens, while throat and sputum samples were subjected to bacterial culture. Generalized linear mixed models were used to assess potential risk factors for associations with ILI. In total, 548 episodes of ILI were reported among 476 (9.7%) of the study participants and 330 (33.2%) of the study households. The adjusted estimated incidence of ILI within the study area was 10.7 (95%CI: 9.4-11.9) episodes per 100 person-years. ILI was significantly associated with age group (p<0.001), sex (p<0.001), and number of bedrooms (p = 0.04) in multivariate analysis. In 548 nasopharyngeal swabs, the most commonly detected potential pathogens were Streptococcus pneumoniae (17.0%), Staphylococcus aureus (11.3%), influenza A (11.1%; mostly subtype H3N2), rhinovirus (7.5%), and influenza B (8.0%). Streptococci were isolated from 42 (8.6%) of 536 throat swabs, most (27) of which were Lancefield Group G. Co-infections were observed in 132 (24.1%) of the 548 ILI episodes. Our study generated valuable data on respiratory disease burden and patterns of etiologies associated with community-acquired acute respiratory illness Laos. Establishment of a surveillance strategy in Laos to monitor trends in the epidemiology and burden of acute respiratory infections is required to minimize their impact on human health.

Association between helminth infections and diabetes mellitus in adults from the Lao People's Democratic Republic: a cross-sectional study

BACKGROUND

As a result of epidemiological transition, the health systems of low- and middle-income countries are increasingly faced with a dual disease burden of infectious diseases and emerging non-communicable diseases. Little is known about the mutual influence of these two disease groups. The aim of this study was to investigate the co-occurrence of helminth infections and diabetes mellitus in adults in Lao People's Democratic Republic (Lao PDR).

METHODS

We conducted a cross-sectional study among 1600 randomly selected adults aged 35 and older from four different socio-economical and ecological provinces. Information on socio-demographics, risk factors and health conditions was obtained from personal interviews. Clinical assessments including anthropometry (height, weight, waist and hip circumference) and blood pressure measurements were also conducted. Diabetes was classified based on self-reported diagnoses and a point-of-care glycated haemoglobin (HbA1c) test from finger prick blood samples. Stool samples for helminth diagnosis were examined with formalin-ether concentration technique for intestinal parasitic infections. The independent associations of helminth infections with diabetic status and HbA1c were assessed using multiple regression analyses.

RESULTS

The prevalence of pre-diabetes and diabetes was 37.3% and 22.8%, respectively. Fifty-six percent of diabetic cases were undiagnosed and 85% of diagnosed diabetic cases had poor glycemic control. Participants from rural areas and from southern parts of the country had higher infection rates, with Opisthorchis viverrini, being the most common helminth infection (30.5%). We found a positive association between Taenia spp. infections and HbA1c (β = 0.117; 95% CI: 0.042-0.200) and diabetes mellitus risk (OR = 2.98; 95% CI: 1.10-8.05). No other helminth species was associated with glycated hemoglobin.

CONCLUSIONS

Hyperglycaemia and diabetic rates in Lao PDR are alarmingly high, but consistent with other high rates in the region. Given the high rates of under-diagnosis and poorly-controlled glycaemia in diabetes mellitus patients, routine diabetes screening and treatment is essential for the local healthcare system. Large longitudinal cohorts integrating biomarkers are warranted in the search of causal diabetes mellitus risk factors in the region. Common intestinal helminth infections, including O. viverrini, are unlikely to explain the high diabetes mellitus rates observed.

Hepatitis C in Laos: A 7-Year Retrospective Study on 1765 Patients

Hepatitis C virus (HCV) is a global health concern, notably in Southeast Asia, and in Laos the presentation of the HCV-induced liver disease is poorly known. Our objective was thus to describe a comprehensive HCV infection pattern in order to guide national health policies. A study on a group of 1765 patients formerly diagnosed by rapid test in health centres was conducted at the Centre of Infectiology Lao Christophe Merieux in Vientiane. The demographic information of patients, their infection status (viral load: VL), liver function (aminotransferases) and treatments were analysed. Results showed that gender distribution of infected people was balanced; with median ages of 53.8 for men and 51.6 years for women (13-86 years). The majority of patients (72%) were confirmed positive (VL > 50 IU/mL) and 28% of them had high VL (> 6log₁₀). About 23% of patients had level of aminotransferases indicative of liver damage (> 40 IU/mL); but less than 20% of patients received treatment. Patients rarely received a second sampling or medical imaging. The survey also showed that cycloferon, pegylated interferon and ribavirin were the drugs prescribed preferentially by the medical staff, without following any international recommendations schemes. In conclusion, we recommend that a population screening policy and better management of patients should be urgently implemented in the country, respecting official guidelines. However, the cost of biological analysis and treatment are significant barriers that must be removed. Public health resolutions should be immediately enforced in the perspective of meeting the WHO HCV elimination deadline by 2030.

Intestinal Parasitic Infections and Environmental Water Contamination in a Rural Village of Northern Lao PDR

A field survey studying intestinal parasites in humans and microbial pathogen contamination at environment was performed in a Laotian rural village to identify potential risks for disease outbreaks. A parasitological investigation was conducted in Ban Lak Sip village, Luang Prabang, Lao PDR involving fecal samples from 305 inhabitants as well as water samples taken from 3 sites of the local stream. Water analysis indicated the presence of several enteric pathogens, i.e., Aeromonas spp., Vibrio spp., E. coli H7, E. coli O157: H7, verocytotoxin-producing E. coli (VTEC), Shigella spp., and enteric adenovirus. The level of microbial pathogens contamination was associated with human activity, with greater levels of contamination found at the downstream site compared to the site at the village and upstream, respectively. Regarding intestinal parasites, the prevalence of helminth and protozoan infections were 68.9% and 27.2%, respectively. Eight helminth taxa were identified in fecal samples, i.e., 2 tapeworm species (Taenia sp. and Hymenolepis diminuta), 1 trematode (Opisthorchis sp.), and 5 nematodes (Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis, trichostrongylids, and hookworms). Six species of intestinal protists were identified, i.e., Blastocystis hominis, Cyclospora spp., Endolimax nana, Entamoeba histolytica/E. dispar, Entamoeba coli, and Giardia lamblia. Questionnaires and interviews were also conducted to determine risk factors of infection. These analyses together with a prevailing infection level suggested that most of villagers were exposed to parasites in a similar degree due to limited socio-economic differences and sharing of similar practices. Limited access to effective public health facilities is also a significant contributing factor.

Intestinal parasitic infections in HIV-infected patients, Lao People's Democratic Republic

Background

HIV infection is an emerging problem in Laos. We conducted the first prospective study on intestinal parasites, including opportunistic protozoa, in newly diagnosed HIV infected patients, with or without diarrhea. The aims were to describe the spectrum of infections, to determine their prevalence and to assess their associations with diarrhea, CD4 cell count, place of residence and living conditions.

Methodology

One to three stool samples over consecutive days were obtained from 137 patients. The Kato thick smear method, formalin-ethyl concentration and specific stains for coccidia and microsporidia diagnosis were performed on 260 stool samples. Baseline characteristics regarding relevant demographics, place of residence and living conditions, clinical features including diarrhea, were collected using a standardized questionnaire.

Principal Findings

The 137 patients were young (median age: 36 years) and severely immunocompromised (83.9% at WHO stage 3 or 4, median CD4 cell count: 41/mm³). Diarrhea was present in 43.0% of patients. Parasite infection was found in 78.8% of patients, infection with at least two species in 49.6%. Prevalence rates of protozoan and helminth infections were similar (54.7% and 58.4% respectively). Blastocystis sp. was the most frequent protozoa (26.3%). Cryptosporidium sp., Cytoisospora belli and microsporidia, found at low prevalence rates (6.6%, 4.4%, 2.9%, respectively), were described for the first time in Laos. Cryptosporidium sp. was associated with persistent diarrhea. Strongyloides stercoralis was the most prevalent helminth following Opisthorchis viverrini (20.4% and 47.5% respectively). The most immunocompromised patients, as assessed by a CD4 count ≤ 50 cells/mm³, were more likely to be infected with intestinal parasites.

Conclusions/Significance

HIV infection was mainly diagnosed at an advanced stage of immunosuppression in Lao patients. Intestinal parasite infections were highly prevalent regardless of their diarrheal status. Opportunistic infections were reported. Improving the laboratory diagnosis of intestinal parasite infections and the knowledge on their local risk factors is warranted.

2009 A(H1N1) seroconversion rates and risk factors among the general population in Vientiane Capital, Laos

OBJECTIVE

To assess 2009 A(H1N1) seroconversion rates and their determinants within an unvaccinated population in Vientiane Capital, Laos.

METHODS

CoPanFlu Laos, a general population cohort of 807 households and 4,072 participants was established in March 2010. Sociodemographic data, epidemiological data, and capillary blood samples were collected from all the household members in March, and again in October 2010, in order to assess the level of antibodies to 2009 A(H1N1) with the haemagglutination inhibition assay. 2009 A(H1N1) seroconversion was defined as a fourfold or greater increase in titre between inclusion and follow-up. Determinants for pandemic influenza infection were studied using the generalized estimating equations model, taking household clustering into account.

RESULTS

Between March and November 2010, 3,524 paired sera were tested. Prior to the pandemic, our cohort was almost completely vaccine-naive for seasonal influenza. The overall seroconversion rate among nonvaccinated individuals (n = 2,810) was 14.3% (95%CI [13.0, 15.6]), with the highest rate for participants under 20 yo (19.8%, 95%CI [17.4, 22.4]) and the lowest rate for participants over 60 yo (6.5%, 95%CI [3.7, 10.4]). Participants with lower baseline titres had significantly higher infection rates, with a dose-effect relationship. Odds ratios (ORs) ranged from 76.5 (95%CI [27.1, 215.8]), for those with a titre at inclusion of 1∶10, to 8.1 (95%CI [3.3, 20.4]), for those with a titre of 1∶40. Having another household member with a titre ≥1∶80 was associated with a higher likelihood of immunity (OR = 3.3, 95%CI [2.8, 3.9]).

CONCLUSION

The determinants and age distribution for seroconversion within a vaccine-naive population were similar to those found in developed countries. This pandemic was characterized by strong epidemiological determinants, regardless of geographical zone and level of development. Moreover, we detected pre-existing cross-reacting antibodies in participants over 60 yo, which could not have originated from former multiple vaccination as has been suggested elsewhere.

Bleach treatment of sputum samples aids pulmonary tuberculosis screening among HIV-infected patients in Laos

BACKGROUND

Laos has a high prevalence of tuberculosis (TB) and a slowly increasing prevalence of human immunodeficiency virus/acquired immunedeficiency syndrome (HIV/AIDS). Sputum smear microscopy is the only method currently available for routine screening of pulmonary TB, although it only detects one in three cases among persons living with HIV (PLWH). Bleach treatment of sputum samples (bleach method) has been shown to significantly improve the sensitivity of the test; however, its effectiveness in PLWH remains to be determined in Laos.

OBJECTIVES

To determine the performance of the bleach method as a diagnostic tool for pulmonary TB in PLWH and to assess its cost-effectiveness in Laos.

RESULTS

Of 174 sputum samples collected from 92 patients, 29 were culture-positive for Mycobacterium tuberculosis in 17 patients. The sensitivity of the direct method and the bleach method was respectively 59% and 93%, and specificity was 100% for both methods. The incremental cost-effectiveness ratio for screening an additional case was US$17.40.

CONCLUSION

The bleach method is simple, cheap, easy to perform and cost-effective in PLWH. Its implementation in laboratories involved in routine screening of pulmonary TB among PLWH would allow practitioners to start the treatment of this life-threatening co-infection earlier.