2017年 · 第06卷第01期

Schistosomiasis is a waterborne parasitic disease in sub-Saharan Africa, particularly common in rural populations living in impoverished conditions. With the scale-up of preventive chemotherapy, national campaigns will transition from morbidity- to transmission-focused interventions thus formal investigation of actual or expected declines in environmental transmission is needed as 'end game’ scenarios arise. Surprisingly, there are no international or national guidelines to do so in sub-Saharan Africa. Our article therefore provides an introduction to key practicalities and pitfalls in the development of an appropriate environmental surveillance framework. In this context, we discuss how strategies need to be adapted and tailored to the local level to better guide and support future interventions through this transition. As detection of egg-patent infection in people becomes rare, careful sampling of schistosome larvae in freshwater and in aquatic snails with robust species-specific DNA assays will be required. Appropriate metrics, derived from observed prevalence(s) as compared with predetermined thresholds, could each provide a clearer insight into contamination- and exposure-related dynamics. Application could be twofold, first to certify areas currently free from schistosomiasis transmission or second to red-flag recalcitrant locations where extra effort or alternative interventions are needed.

Schistosomiasis is a water borne parasitic disease of global importance and with ongoing control the disease endemic landscape is changing. In sub-Saharan Africa, for example, the landscape is becoming ever more heterogeneous as there are several species of Schistosoma that respond in different ways to ongoing preventive chemotherapy and the inter-sectoral interventions currently applied. The major focus of preventive chemotherapy is delivery of praziquantel by mass drug administration to those shown to be, or presumed to be, at-risk of infection and disease. In some countries, regional progress may be uneven but in certain locations there are very real prospects to transition from control into interruption of transmission, and ultimately elimination. To manage this transition requires reconsideration of some of the currently deployed diagnostic tools used in surveillance and downward realignment of existing prevalence thresholds to trigger mass treatment. A key challenge will be maintaining and if possible, expanding the current donation of praziquantel to currently overlooked groups, then judging when appropriate to move from mass drug administration to selective treatment. In so doing, this will ensure the health system is adapted, primed and shown to be cost-effective to respond to these changing disease dynamics as we move forward to 2020 targets and beyond.

Intestinal schistosomiasis is of public health importance in Uganda but communities living above 1400 m are not targeted for control as natural transmission is thought unlikely. To assess altitudinal boundaries and at-risk populations, conjoint malacological and epidemiological surveys were undertaken on Mount Elgon (1139 m–3937 m), in Fort Portal crater lakes and in the Rwenzori Mountains (1123 m–4050 m).

Seventy freshwater habitats [Mount Elgon (37), Fort Portal crater lakes (23), Rwenzori Mountains (8) and Lake Albert (2)] were inspected for Biomphalaria species. Water temperature, pH and conductivity were recorded. A parasitological examination of 756 schoolchildren [Mount Elgon (300), Fort Portal crater lakes (456)] by faecal microscopy of duplicate Kato-Katz smears from two consecutive stool samples was bolstered by antigen (urine-CCA dipstick) and antibody (SEA-ELISA) diagnostic assays.

Biomphalaria spp. was found up to 1951 m on Mount Elgon and 1567 m in the Fort Portal crater lakes. Although no snail from Mount Elgon shed cercariae, molecular analysis judged 7.1% of snails sampled at altitudes above 1400 m as having DNA of Schistosoma mansoni; in Fort Portal crater lakes three snails shed schistosome cercariae. Prevalence of intestinal schistosomiasis as measured in schoolchildren by Kato-Katz (Mount Elgon = 5.3% v. Fort Portal crater lakes = 10.7%), CCA urine-dipsticks (18.3% v. 34.4%) and SEA-ELISA (42.3% v. 63.7%) showed negative associations with increasing altitude with some evidence of infection up to 2000 m.

Contrary to expectations, these surveys clearly show that natural transmission of intestinal schistosomiasis occurs above 1400 m, possibly extending up to 2000 m. Using spatial epidemiological predictions, this now places some extra six million people at-risk, denoting an expansion of preventive chemotherapy needs in Uganda.

The crater lakes of Barombi Mbo and Barombi Kotto are well-known transmission foci of schistosomiasis and soil-transmitted helminthiasis having had several important control initiatives previously. To collect contemporary epidemiological information, a cross-sectional survey was undertaken inclusive of: signs and symptoms of disease, individual treatment histories, local water, sanitation and hygiene (WASH)-related factors and malacological surveillance, with molecular characterisation of specimens.

At each lake, a community cross-sectional survey was undertaken using a combination of stool and urine parasitological sampling, and interview with pro-forma questionnaires. A total of 338 children and adults participated. Material from snail and parasite species were characterised by DNA methods.

Egg-patent prevalence of urogenital schistosomiasis was 8.7% at Barombi Mbo (all light-intensity infections) and 40.1% at Barombi Kotto (21.2% heavy-intensity infections). Intestinal schistosomiasis was absent. At Barombi Kotto, significantly more women reported signs and symptoms associated with female genital schistosomiasis. While there had been extensive recent improvement in WASH-related infrastructure at Barombi Mbo, water contact risk scores were higher among schistosomiasis-infected participants (P < 0.001) and at Barombi Kotto in general (P < 0.001). Across both lakes, mean prevalence of STH was very low (6.3%) evidencing an impressive decrease of 79.0% over the last decade; neither Strongyloides stercoralis nor Ascaris lumbricoides were found. A total of 29 freshwater sampling sites were inspected for snails, 13 in Barombi Mbo and 16 in Barombi Kotto; water chemistry differed significantly (P < 0.0001) between lakes for both mean pH (7.9 v. 9.6) and mean conductivity (64.3 μS v. 202.1 μS) respectively. Only two Bulinus camerunensis found on the central island of Barombi Kotto were observed to shed schistosome cercariae, but schistosome DNA was later detected in Bulinus sampled from both lakes as well as in Indoplanorbis exustus, an invasive species from Asia. (Continued on next page)

STH is currently at very low levels while urogenital schistosomiasis is of greatest concern at Barombi Kotto. This assessment highlights a unique opportunity for further study of the epidemiological dynamics at these crater lakes, to evaluate future intensified interventions both in terms of gaining and sustaining control at Barombi Kotto or in moving towards local interruption of transmission of both diseases at Barombi Mbo.

Urinary schistosomiasis has been a major public health problem in Zambia for many years. However, the disease profile may vary in different locale due to the changing ecosystem that contributes to the risk of acquiring the disease. The objective of this study was to quantify risk factors associated with the intensity of urinary schistosomiasis infection in school children in Lusaka Province, Zambia, in order to better understand local transmission.

Data were obtained from 1 912 school children, in 20 communities, in the districts of Luangwa and Kafue in Lusaka Province. Both individual- and community-level covariates were incorporated into an ordinal logistic regression model to predict the probability of an infection being a certain intensity in a three-category outcome response: 0 = no infection, 1 = light infection, and 2 = moderate/heavy infection. Random effects were introduced to capture unobserved heterogeneity.

Overall, the risk of urinary schistosomiasis was strongly associated with age, altitude at which the child lived, and sex. Weak associations were observed with the normalized difference vegetation index, maximum temperature, and snail abundance. Detailed analysis indicated that the association between infection intensities and age and altitude were category-specific. Particularly, infection intensity was lower in children aged between 5 and 9 years compared to those aged 10 to 15 years (OR = 0.72, 95% CI= 0.51–0.99). However, the age-specific risk changed at different levels of infection, such that when comparing children with light infection to those who were not infected, age was associated with a lower odds (category 1 vs category 0: OR= 0.71, 95% CI: 0.50–0.99), yet such a relation was not significant when considering children who were moderately or heavily infected compared to those with a light or no infection (category 2 vs category 0: OR= 0.96, 95% CI: 0.45–1.64). Overall, we observed that children living in the valley were less likely to acquire urinary schistosomiasis compared to those living in plateau areas (OR = 0.48, 95% CI: 0. 16–0.71). However, category-specific effects showed no significant association in category 1 (light infection), whereas in category 2 (moderate/high infection), the risk was still significantly lower for those living in the valley compared to those living in plateau areas (OR= 0.18, 95% CI: 0.04–0.75).

This study demonstrates the importance of understanding the dynamics and heterogeneity of infection in control efforts, and further suggests that apart from the well-researched factors of Schistosoma intensity, various other factors influence transmission. Control programmes need to take into consideration the varying infection intensities of the disease so that effective interventions can be designed.

The data on hepatitis b virus (HBV) infection in immigrants population are scanty. The porpoise of this study was to define the demographic, virological, and clinical characteristics of subjects infected with HBV chronic infection in a cohort of immigrants living in Naples, Italy.

A screening for HBV infection was offered to 1,331 immigrants, of whom 1,212 (91%) (831 undocumented immigrants and 381 refugees) accepted and were screened for hepatitis B surface antigen (HBsAg) and anti-hepatitis B core antibody (HBc). Those found to be HBsAg positive were further investigated at third-level infectious disease units.

Of the 1,212 immigrants screened, 116 (9.6%) were HBsAg positive, 490 (40.4%) were HBsAg negative/anti-HBc positive, and 606 (50%) were seronegative for both. Moreover, 21 (1.7%) were anti-human immunodeficiency virus positive and 45 (3.7%) were anti-hepatitis C virus positive. The logistic regression analysis showed that male sex (OR: 1.79; 95%CI: 1.28–2.51), Sub-Saharan African origin (OR: 6.18; 95%CI: 3.37–11.36), low level of schooling (OR: 0.96; 95%CI: 0.94–0.99), and minor parenteral risks for acquiring HBV infection (acupuncture, tattoo, piercing, or tribal practices, OR: 1.54; 95%CI: 1.1–2.16) were independently associated with ongoing or past HBV infection. Of the 116 HBsAg-positive immigrants, 90 (77.6%) completed their diagnostic itinerary at a third-level infectious disease unit: 29 (32.2%) were asymptomatic non-viremic HBsAg carriers, 43 (47.8%) were asymptomatic viremic carriers, 14 (15.6%) had chronic hepatitis, and four (4.4%) had liver cirrhosis, with superimposed hepatocellular carcinoma in two.

The data illustrate the demographic, clinical and virological characteristics of HBV infection in immigrants in Italy and indicate the need for Italian healthcare authorities to enhance their support for providing screening, HBV vaccination, treatment, and educational programs for this populations.

There has been a growing interest in camel anaplasmosis due to its recent emergence in this reservoir species and concerns for its zoonotic potential. The epidemiology of anaplasmosis in camels therefore remains poorly understood mostly because camels belong to marginalised poor and often transhumant populations whose interests are largely neglected. Most studies of anaplasmosis in camels have relied on microscopy and serology for diagnosis and only three studies, undertaken in Tunisia, Saudia Arabia and China, have used molecular diagnostics. The present work characterises Anaplasmataceae strains circulating in the Camelus dromedarius reservoir in Morocco using PCR.

Camels (n = 106) were randomly sampled from 6 regions representing different agro-ecological areas in southern Morocco. Whole blood was collected and screened using PCR methods targeting the gene groEL. Anaplasmataceae strains were characterised by sequence analysis of the gene groEL.

A total of 39.62% (42/106) camels screened were positive for Anaplasmataceae spp. GenBank BLAST analysis of five positive sequenced samples revealed that all strains were 100% identical to "Candidatus Anaplasma camelii". Phylogenetic investigation and genetic characterisation of the aligned segment (650 bp) of the gene groEL confirmed high similarity with A. platys.

This study demonstrates the circulation of a previously unidentified species of the genus Anaplasma in Morocco which is genetically close to the agent causing canine anaplasmosis but whose main reservoir is thought to be Camelus dromedarius. Trial registration number: This study is not a clinical trial and therefore a trial registration number does not apply.

Anthrax is an acute zoonotic infectious disease caused by the bacterium known as Bacillus anthracis. From 26 July to 8 August 2015, an outbreak with 20 suspected cutaneous anthrax cases was reported in Ganquan County, Shaanxi province in China. The genetic source tracking analysis of the anthrax outbreak was performed by molecular epidemiological methods in this study.

Three molecular typing methods, namely canonical single nucleotide polymorphisms (canSNP), multiple-locus variable-number tandem repeat analysis (MLVA), and single nucleotide repeat (SNR) analysis, were used to investigate the possible source of transmission and identify the genetic relationship among the strains isolated from human cases and diseased animals during the outbreak.

Five strains isolated from diseased mules were clustered together with patients’ isolates using canSNP typing and MLVA. The causative B. anthracis lineages in this outbreak belonged to the A.Br.001/002 canSNP subgroup and the MLVA15-31 genotype (the 31 genotype in MLVA15 scheme). Because nine isolates from another four provinces in China were clustered together with outbreak-related strains by the canSNP (A.Br.001/002 subgroup) and MLVA15 method (MLVA15-31 genotype), still another SNR analysis (CL10, CL12, CL33, and CL35) was used to source track the outbreak, and the results suggesting that these patients in the anthrax outbreak were probably infected by the same pathogen clone.

It was deduced that the anthrax outbreak occurred in Shaanxi province, China in 2015 was a local occurrence.

Food-borne diseases are attracting a lot of attention in Vietnam as a result of repeated episodes of adulterated and unsafe food. In this paper, we provide some perspectives on food safety in Vietnam from the point of view of an international research institution working on food safety with partners in the country. We argue that one of the key issues of food safety in Vietnam is that certain food value chain stakeholders lack ethics, which leads to the production and trading of unsafe foods in order to make profits irrespective of adverse health effects on consumers. In turn, the shortfall in ethical behaviours around food can be attributed to a lack of incentives or motivating factors. Although food safety causes panic in the population, it is unclear how much contaminated food contributes to the burden of food-borne diseases and food poisonings in Vietnam. However, globally, the biggest health problem associated with food are infections from consuming food contaminated with viruses, bacteria or parasites. A major food safety challenge is the inappropriate way of communicating food risks to the public. Another key constraint is the inherent difficulty in managing food in wet markets and from smallholder production. On the other hand, local foods, and local food production and processing are an important cultural asset as well as being essential to food safety, and these aspects can be put at risk if food safety concerns motivate consumers to purchase more imported foods. In this paper, we also discuss good experiences in food safety management from other countries and draw lessons learnt for Vietnam on how to better deal with the current food safety situation.

Tuberculosis (TB) kills approximately two million people and infects around nine million worldwide annually. Its proper management, especially in resource-limited settings, has been hindered by the lack of rapid and easy-to-use diagnostic tests. Sputum smear microscopy remains the cheapest, readily available diagnostic method but it only identifies less than half of the patients with a HIV/TB co-infection because the bacilli would have disseminated from the lungs to other areas of the body. The fully automated Xpert^® MTB/RIF assay is a promising innovation for diagnosing TB and detecting resistance to rifampicin. This study aimed to evaluate the use of Xpert^® MTB/RIF assay and microscopy in the diagnosis of Mycobacterium tuberculosis in Namibia, by determining the disease’s epidemiology and calculating the proportion of cases infected just with TB and those with a resistance to rifampicin among the total suspected cases of TB in the country.

This retrospective study analysed TB cases that were diagnosed using both the Xpert^® MTB/RIF assay and microscopy. Data were collected from patient records from the Meditech laboratory information system of the Namibia Institute of Pathology for the time period of July 2012–April 2013. Data from 13 regions were collected.

The total number of specimens collected from patients with symptoms of pulmonary TB was 1 842. Of these, 594 (32.20%) were found to be positive for MTB by Xpert^® MTB/RIF assay, out of which 443 (24.05%) were also found to be positive by microscopy. The remainder was negative. The male patients were more resistant to rifampicin when compared to the female patients.

Tuberculosis is widely distributed throughout Namibia, with slightly more males infected than females. Most TB patients are also co-infected with HIV. Both microscopy and Xpert^® MTB/RIF assay are crucial for the diagnosis of TB in the country. Screening diagnostic efforts should focus on the sexually active HIV positive male population who could be the source of more RIF-resistant TB than females to prevent its spread.

To successfully eliminate malaria, an integrated system that includes a number of approaches and interventions—aimed at overcoming the threat of antimalarial drug resistance—is required. Significant progress has been made in reducing malaria incidence through large-scale use of artemisinin-based combination therapies and insecticide-treated nets. To consolidate these gains, attention should be paid to the missing links in the elimination of malaria. One of these gaps is the residual reservoir of submicroscopic resistant parasites, which remains after case management or other control measures have been carried out. Therefore, the present opinion piece highlights the importance of exploring the role that submicroscopic resistant parasites could play in hindering malaria elimination by allowing the persistence of transmission, particularly in areas of low transmission or in the pre-elimination and/or elimination phase.

If malaria elimination interventions are to be effective, the relative role of the hidden reservoir of resistant parasites needs to be assessed, particularly in regions that are low-transmission settings and/or in pre-elimination and/or elimination phases. Various ongoing studies are focusing on the role of submicroscopic malaria infections in malaria transmission but overlook the possible build-up of resistance to antimalarial drugs among submicroscopic parasite populations. This is an important factor as it may eventually limit the effectiveness of malaria elimination strategies.

An evidence-based estimation of the "true" reservoir of resistant parasites can help target the existing and emerging foci of resistant parasites before they spread. Emergence and spread of artemisinin-resistant Plasmodium falciparum malaria in Southeast Asia underline the need to contain drug resistance.

Recently, the mortality of 240 causes in China including a subnational analysis during 1990–2013 was published in The Lancet. This comprehensive analysis will undoubtedly impact policymaking regarding public health in China. However, it is unfavourable in some degree to neglected tropical diseases, which is the subject of this Letter to the Editor. Policymakers, especially those in less developed provinces of China, should fully consider the burden of neglected tropical diseases, which will benefit the control and final elimination of these diseases in the country.