Travel-related schistosomiasis acquired in Laos

Cutaneous schistosomiasis: epidemiological and clinical characteristics in returning travelers

The clinical manifestations of parasitic diseases are well-covered in the infectious disease literature; however, cutaneous manifestations often receive limited attention. There is a need to update existing knowledge and improve reporting of disease characteristics. Given continued increases in travel and transportation, more individuals are acquiring cutaneous infections while traveling abroad. Schistosomiasis is the second most important tropical disease among returning travelers and affects more than 200 million individuals worldwide. The literature classically describes three forms of skin disease in those infected with Schistosoma: the immediate pruritic eruption of cercarial dermatitis, the urticarial response of Katayama syndrome, and the granulomatous lesions of late cutaneous schistosomiasis. Over the last two decades, more atypical presentations have been described. Travelers returning from Africa, South America, and Asia are at highest risk given these are the continents in which the parasite is endemic. This review highlights the cutaneous manifestations of schistosomiasis, with a focus on international travelers with atypical presentations. Additionally, genital schistosomiasis will be reviewed given its significant morbidity. The aim of this review is to update the current body of literature. Dermatologists and other physicians evaluating the skin should be aware of the following principles regarding schistosomal infections: (i) the importance of an early skin biopsy in making the diagnosis; (ii) the necessity of adding schistosomiasis to the differential diagnosis for zosteriform lesions; (iii) the resemblance of chronic cutaneous schistosomiasis of the genitals to sexually transmitted infections; and (iv) the need to revise definitions for early and late infection, specifically for cutaneous disease.

Clinical Spectrum of Schistosomiasis: An Update

Schistosomiasis is a helminthic infection and one of the neglected tropical diseases (NTDs). It is caused by blood flukes of the genus Schistosoma. It is an important public health problem, particularly in poverty-stricken areas, especially those within the tropics and subtropics. It is estimated that at least 236 million people worldwide are infected, 90% of them in sub-Saharan Africa, and that this disease causes approximately 300,000 deaths annually. The clinical manifestations are varied and affect practically all organs. There are substantial differences in the clinical presentation, depending on the phase and clinical form of schistosomiasis in which it occurs. Schistosomiasis can remain undiagnosed for a long period of time, with secondary clinical lesion. Here, we review the clinical profile of schistosomiasis. This information may aid in the development of more efficacious treatments and improved disease prognosis.

Schistosomiasis: still a neglected disease

Schistosomiasis remains an infrequent travel-related disease, mostly affecting returnees from Sub-Saharan Africa. The neglect of schistosomiasis research and development has consequences not only for endemic populations but also for travellers. Recent studies highlight deficits in clinical recognition, diagnostics and therapy of travel-related schistosomiasis, with significant morbidity, both acute and chronic.

First case report of Schistosoma japonicum in Nepal

Background

Schistosomiasis, globally, is significant public as well as veterinary health problem as it is associated with a wide range of clinical conditions in humans and animals. Schistosomiasis is mostly caused by the following species of genus Schistosoma: Schistosoma japonicum, Schistosoma haematobium, Schistosoma mekongi, Schistosoma intercalatum Schistosoma guineensis, Schistosoma malayensis and Schistosoma mansoni. S. japonicum might be considered as the most pathogenic among these species as the clinical disease caused by this parasite ranges from mild diarrhea, nausea, Katayama fever, portal hypertension, splenomegaly and ascites to liver cirrhosis and fibrosis. S. japonicum has been commonly encountered in China, the Philippines and Indonesia. According to WHO, at least 220.8 million people required preventive treatment for schistosomiasis in 2017 but only 102.3 million people were reported to have been treated. To our knowledge, there are no cases reported from Nepal. Hence, this is the first reported case of S. japonicum in Nepal.

Case presentation

A case of acute schistosomiasis due to S. japonicum was identified in CIWEC Hospital and Travel Medicine Center, Kathmandu, Nepal. The patient arrived with gastrointestinal symptoms without any pre-existing chronic illness with no evidence of travel outside of Spain since last August, but had travelled to many other countries 2 years ago. Timely diagnosis by stool routine and microscopic examination and formal-ether concentration technique led to successful treatment of the disease.

Conclusion

As the parasite has not been reported to date in Nepal, many people are unaware of its mode of infection and pathogenesis. Many laboratory workers are heedless with the egg of the parasite due to which this parasite might be misdiagnosed or undiagnosed. This case report might help laboratory workers to be sentient about the parasite and further diagnosis in future.

Effect of Praziquantel on Schistosoma mekongi Proteome and Phosphoproteome

Schistosoma mekongi causes schistosomiasis in southeast Asia, against which praziquantel (PZQ) is the only treatment option. PZQ resistance has been reported, thus increasing the requirement to understand mechanism of PZQ. Herein, this study aimed to assess differences in proteome and phosphoproteome of S. mekongi after PZQ treatment for elucidating its action. Furthermore, key kinases related to PZQ effects were predicted to identify alternative targets for novel drug development. Proteomes of S. mekongi were profiled after PZQ treatment at half maximal inhibitory concentration and compared with untreated worms. A total of 144 proteins were differentially expressed after treatment. In parallel, immunohistochemistry indicated a reduction of phosphorylation, with 43 phosphoproteins showing reduced phosphorylation, as identified by phosphoproteomic approach. Pathway analysis of mass spectrometric data showed that calcium homeostasis, worm antigen, and oxidative stress pathways were influenced by PZQ treatment. Interestingly, two novel mechanisms related to protein folding and proteolysis through endoplasmic reticulum-associated degradation pathways were indicated as a parasiticidal mechanism of PZQ. According to kinase–substrate predictions with bioinformatic tools, Src kinase was highlighted as the major kinase related to the alteration of phosphorylation by PZQ. Interfering with these pathways or applying Src kinase inhibitors could be alternative approaches for further antischistosomal drug development.

Transcriptomic analysis of male and female Schistosoma mekongi adult worms

Background

Schistosoma mekongi is one of five major causative agents of human schistosomiasis and is endemic to communities along the Mekong River in southern Lao People’s Democratic Republic (Laos) and northern Cambodia. Sporadic cases of schistosomiasis have been reported in travelers and immigrants who have visited endemic areas. Schistosoma mekongi biology and molecular biology is poorly understood, and few S. mekongi gene and transcript sequences are available in public databases.

Results

Transcriptome sequencing (RNA-Seq) of male and female S. mekongi adult worms (a total of three biological replicates for each sex) were analyzed and the results demonstrated that approximately 304.9 and 363.3 million high-quality clean reads with quality Q30 (> 90%) were obtained from male and female adult worms, respectively. A total of 119,604 contigs were assembled with an average length of 1273 nt and an N50 of 2017 nt. From the contigs, 20,798 annotated protein sequences and 48,256 annotated transcript sequences were obtained using BLASTP and BLASTX searches against the UniProt Trematoda database. A total of 4658 and 3509 transcripts were predominantly expressed in male and female worms, respectively. Male-biased transcripts were mostly involved in structural organization while female-biased transcripts were typically involved in cell differentiation and egg production. Interestingly, pathway enrichment analysis suggested that genes involved in the phosphatidylinositol signaling pathway may play important roles in the cellular processes and reproductive systems of S. mekongi worms.

Conclusions

We present comparative transcriptomic analyses of male and female S. mekongi adult worms, which provide a global view of the S. mekongi transcriptome as well as insights into differentially-expressed genes associated with each sex. This work provides valuable information and sequence resources for future studies of gene function and for ongoing whole genome sequencing efforts in S. mekongi.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3086-z) contains supplementary material, which is available to authorized users.

Ultrasonographic investigation of cholangiocarcinoma in Lao PDR

Opisthorchis viverrini is a group 1 carcinogen that causes cholangiocarcinoma (CCA). Although opisthorchiasis is known to be severely endemic to several areas along the Mekong River in Lao PDR, the CCA status of residents of this region is still under investigation. In this study, we analyzed the results of abdominal ultrasonography (US) performed on 6113 residents in 9 provinces (Vientiane Municipality, Savannakhet, Phongsaly, Khammouane, Saravane, Champasak, Vientiane, Xieng Khuouang, and Luang Prabang provinces) of Lao PDR from 2007 to 2011. Overall, 51 cases (0.83%) were detected with suspected CCA. The CCA rates in Vientiane Municipality and in Savannakhet and Khammouane provinces were 1.45%, 1.58%, and 1.09%, respectively. However, in the other 6 provinces, the rate of CCA averaged only 0.26%. In the 3 provinces with higher rates of CCA, bile duct dilatation (grade ≥ 2) was also significantly more prevalent (P < 0.0001). These results are concordant with previous reports showing a higher endemicity of opisthorchiasis in Vientiane Municipality and in Savannakhet and Khammouane provinces.

Serological approaches for the diagnosis of schistosomiasis - A review

Schistosomiasis is a common disease in endemic areas of Sub-Saharan Africa, South America and Asia. It is rare in Europe, mainly imported from endemic countries due to travelling or human migration. Available methods for the diagnosis of schistosomiasis comprise microscopic, molecular and serological approaches, with the latter detecting antigens or antibodies associated with Schistosoma spp. infection. The serological approach is a valuable screening tool in low-endemicity settings and for travel medicine, though the interpretation of any diagnostic results requires knowledge of test characteristics and a patient's history. Specific antibody detection by most currently used assays is only possible in a relatively late stage of infection and does not allow for the differentiation of acute from previous infections for therapeutic control or the discrimination between persisting infection and re-infection. Throughout the last decades, new target antigens have been identified, and assays with improved performance and suitability for use in the field have been developed. For numerous assays, large-scale studies are still required to reliably characterise assay characteristics alone and in association with other available methods for the diagnosis of schistosomiasis. Apart from S. mansoni, S. haematobium and S. japonicum, for which most available tests were developed, other species of Schistosoma that occur less frequently need to be taken into account. This narrative review describes and critically discusses the results of published studies on the evaluation of serological assays that detect antibodies against different Schistosoma species of humans. It provides insights into the diagnostic performance and an overview of available assays and their suitability for large-scale use or individual diagnosis, and thus sets the scene for serological diagnosis of schistosomiasis and the interpretation of results.

Advances in the Diagnosis of Human Schistosomiasis

Schistosomiasis is a major neglected tropical disease that afflicts more than 240 million people, including many children and young adults, in the tropics and subtropics. The disease is characterized by chronic infections with significant residual morbidity and is of considerable public health importance, with substantial socioeconomic impacts on impoverished communities. Morbidity reduction and eventual elimination through integrated intervention measures are the focuses of current schistosomiasis control programs. Precise diagnosis of schistosome infections, in both mammalian and snail intermediate hosts, will play a pivotal role in achieving these goals. Nevertheless, despite extensive efforts over several decades, the search for sensitive and specific diagnostics for schistosomiasis is ongoing. Here we review the area, paying attention to earlier approaches but emphasizing recent developments in the search for new diagnostics for schistosomiasis with practical applications in the research laboratory, the clinic, and the field. Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis.

Parasitic infections in travelers and immigrants: part II helminths and ectoparasites

Travel and migration contribute to the emergence of certain parasites which may be imported into nonendemic areas. Noncontrolled importation of food products and animals may also contribute to the diagnosis of infections caused by helminths in nonendemic countries. Some helminth infections such as strongyloidiasis may be life-threatening, especially in immunocompromised patients, and outcome depends on correct diagnosis and treatment. Other helminth infections are neglected tropical diseases associated with chronic disease and/or disability. Major challenges concern the development of improved diagnostic techniques, safer and more effective drug therapies and identification of markers of response to treatment. The study of these imported infections in travelers and immigrants may provide opportunities for research which may not be readily available in resource-poor endemic countries. Updated reviews and guidelines are necessary as new data become available. The second part of this review focuses on infections in travelers and immigrants caused by helminths and ectoparasites.

Serological Prevalence of Schistosoma japonicum in Mobile Populations in Previously Endemic but Now Non-Endemic Regions of China: A Systematic Review and Meta-Analysis

BACKGROUND

Schistosomiasis japonica has been resurging in certain areas of China where its transmission was previously well controlled or interrupted. Several factors may be contributing to this, including mobile populations, which if infected, may spread the disease. A wide range of estimates have been published for S. japonicum infections in mobile populations, and a synthesis of these data will elucidate the relative risk presented from these groups.

METHODS

A literature search for publications up to Oct 31, 2014 on S. japonicum infection in mobile populations in previously endemic but now non-endemic regions was conducted using four bibliographic databases: China National Knowledge Infrastructure, WanFang, VIP Chinese Journal Databases, and PubMed. A meta-analysis was conducted by pooling one arm binary data with MetaAnalyst Beta 3.13. The protocol is available on PROSPERO (No. CRD42013005967).

RESULTS

A total of 41 studies in Chinese met the inclusion criteria, covering seven provinces of China. The time of post-interruption surveillance ranged from the first year to the 31st year. After employing a random-effects model, from 1992 to 2013 the pooled seroprevalence ranged from 0.9% (95% CI: 0.5-1.6%) in 2003 to 2.3% (95% CI: 1.5-3.4) in 1995; from the first year after the disease had been interrupted to the 31st year, the pooled seroprevalence ranged from 0.6% (95% CI: 0.2-2.1%) in the 27th year to 4.0% (95%CI: 1.3-11.3%) in the second year. The pooled seroprevalence in mobile populations each year was significantly lower than among the residents of endemic regions, whilst four papers reported a lower level of infection in the mobile populations than in the local residents out of only 13 papers which included this data.

CONCLUSIONS

The re-emergence of S. japonicum in areas which had previously interrupted transmission might be due to other factors, although risk from re-introduction from mobile populations could not be excluded.

Schistosoma mansoni antigen detects Schistosoma mekongi infection

Northern Cambodia and Southern Laos are highly endemic for Schistosoma mekongi. However, there is currently no immunological assay available that is specific for this form of schistosomiasis. We have validated Schistosoma mansoni antigens to detect S. mekongi-directed antibodies in human sera collected from a highly S. mekongi endemic region in Laos. On two consecutive days stool samples of 234 individuals were analyzed by Kato-Katz for presence of S. mekongi eggs and the results were correlated with serology. A sensitivity of 94.5% was calculated for a combination of ELISA and indirect fluorescence assay (IFA) as compared to the detection of S. mekongi eggs in stool samples as gold standard. The results demonstrate that S. mansoni antigens can be used for the diagnosis of S. mekongi infections.

Chronic Schistosoma mekongi in a traveler--a case report and review of the literature

Travel-related schistosomiasis can be detected in patients without symptoms of acute or chronic infection. A case of Schistosoma mekongi acquired in an endemic area of Laos and discovered unexpectedly from colon biopsies taken 5 years after infection is presented here. A literature review of previous cases of S. mekongi infection specifically associated with travelers is then presented.

Molecular differentiation of Schistosoma japonicum and Schistosoma mekongi by real-time PCR with high resolution melting analysis

Human schistosomiasis caused by Schistosoma japonicum and Schistosoma mekongi is a chronic and debilitating helminthic disease still prevalent in several countries of Asia. Due to morphological similarities of cercariae and eggs of these 2 species, microscopic differentiation is difficult. High resolution melting (HRM) real-time PCR is developed as an alternative tool for the detection and differentiation of these 2 species. A primer pair was designed for targeting the 18S ribosomal RNA gene to generate PCR products of 156 base pairs for both species. The melting points of S. japonicum and S. mekongi PCR products were 84.5±0.07℃ and 85.7±0.07℃, respectively. The method permits amplification from a single cercaria or an egg. The HRM real-time PCR is a rapid and simple tool for differentiation of S. japonicum and S. mekongi in the intermediate and final hosts.

Acute schistosomiasis in European students returning from fieldwork at Lake Tanganyika, Tanzania

BACKGROUND

Schistosomiasis is common in many African regions and poses a risk for travelers and the local population. So far, schistosomiasis in travelers or expatriates returning from the Tanzanian bank of Lake Tanganyika has not been reported.

METHODS

We report a group of students who sought treatment with signs of acute schistosomiasis after having returned from Lake Tanganyika, Tanzania. Information as to travel and exposure as well as clinical and laboratory data were collected.

RESULTS

Schistosomiasis was diagnosed in 8 of 16 students from Berlin, Germany, who had returned from a 2- to 3-month stay of fieldwork in Kigoma District at Lake Tanganyika, Tanzania. All 16 students reported frequent freshwater exposure at the lake. Six patients showed signs of acute schistosomiasis and had fever, and some of them also had cough, weakness, headache, or abdominal pain. Eosinophilia was present in five of the six symptomatic individuals. Notably, two serologically enzyme-linked immunosorbent assay (ELISA)-positive individuals did not report or present with symptoms or abnormal laboratory parameters. Schistosoma mansoni eggs were found in one symptomatic and one asymptomatic individual each. Blood and stool samples from the other eight individuals who were equally exposed to freshwater yielded negative results.

CONCLUSIONS

This is the first report of an outbreak of acute schistosomiasis imported from the Tanzanian shore of Lake Tanganyika and highlights the risk for travelers and the local population of acquiring the infection in that part of Tanzania. It provides arguments for routine serological screening for schistosomiasis in individuals who had prior freshwater contact in endemic areas, irrespective of symptoms or other laboratory findings.

Diagnostic issues of acute schistosomiasis with Schistosoma mekongi in a traveler: a case report

A Belgian traveler returning from Laos developed acute schistosomiasis. Feces microscopy and polymerase chain reaction (PCR) followed by sequence analysis revealed Schistosoma mekongi. Schistosome antibody test results and real-time PCR in serum were initially negative or not interpretable. A HRP-2 antigen test for Plasmodium falciparum and an enzyme-linked immunosorbent assay (ELISA) antibody test for Trichinella yielded false-positive results.

Pyrosequencing for rapid molecular identification of Schistosoma japonicum and S. mekongi eggs and cercariae

Schistosomiasis, which is caused by Schistosoma japonicum and S. mekongi, is a chronic and dangerous widespread disease affecting several countries in Asia. Differentiation between S. japonicum and S. mekongi eggs and/or cercariae via microscopic examination is difficult due to morphological similarities. It is important to identify these etiological agents isolated from animals and humans at the species or genotype level. In this study, a pyrosequencing assay designed to detect S. japonicum and S. mekongi DNA in fecal samples and infected snails was developed and evaluated as an alternative tool to diagnose schistosomiasis. New primers targeting the 18S ribosomal RNA gene were designated for specific amplification. S. japonicum and S. mekongi were identified using a 43-nucleotide pattern of the 18S ribosomal RNA gene and were differentiated using 7 nucleotides within this region. S. japonicum and S. mekongi-infected snails and fecal samples derived from infected mice and rats were differentially detected within a short period of time. The analytical sensitivity of the method enabled the identification of as little as a single cercaria artificially introduced into a pool of 10 non-infected snails and 2 eggs inoculated in 100mg of non-infected fecal sample. To evaluate the comparative efficacy of the assay, identical samples were also analyzed via microscopy and Sanger sequencing. The pyrosequencing technique was found to be superior to the microscopy method and more rapid than the Sanger sequencing method. These results suggest that the pyrosequencing assay is rapid, simple, sensitive and accurate in identifying S. japonicum and S. mekongi in intermediate hosts and fecal samples of the final host.

Schistosomiasis: current epidemiology and management in travelers

Schistosomiasis is increasingly encountered among travelers returning from the tropics, mainly from Africa. Schistosoma-infected travelers have served as sentinels for the existence of unknown foci of transmission even outside Africa. Acute schistosomiasis (also termed Katayama syndrome) is the common manifestation among travelers and may follow exposure to any of the Schistosoma species. Neuroschistosomiasis is a rare complication but may result in severe disability. Diagnosis in travelers is hampered by the poor sensitivity of microscopy in urine and stool, especially during acute infections, while seroconversion may be delayed for a period of weeks. During acute schistosomiasis, symptomatic treatment is the only available therapy, while for chronic schistosomiasis, praziquantel is the only drug available, despite reports of emerging resistance to it. Since the potential for exposure to Schistosoma through travel will probably continue to increase, it is clear that new, sensitive diagnostic methods and drugs affecting the parasite in all its stages are needed.

Observations on Neotricula aperta (Gastropoda: Pomatiopsidae) population densities in Thailand and central Laos: implications for the spread of Mekong schistosomiasis

Background

The snail Neotricula aperta transmits Mekong schistosomiasis in southern Laos and Cambodia, with about 1.5 million people at risk of infection. Plans are under consideration for at least 12 hydroelectric power dams on the lower Mekong river and much controversy surrounds predictions of their environmental impacts. Unfortunately, there are almost no ecological data (such as long term population trend studies) available for N. aperta which could be used in impact assessment. Predictions currently assume that the impacts will be the same as those observed in Africa (i.e., a worsening of the schistosomiasis problem); however, marked ecological differences between the snails involved suggest that region specific models are required. The present study was performed as an initial step in providing data, which could be useful in the planning of water resource development in the Mekong. Snail population density records were analyzed for populations close to, and far downstream of, the Nam Theun 2 (NT2) project in Laos in order to detect any changes that might be attributable to impoundment.

Results

The population immediately downstream of NT2 and that sampled 400 km downstream in Thailand both showed a long term trend of slow growth from 1992 to 2005; however, both populations showed a marked decline in density between 2005 and 2011. The decline in Thailand was to a value significantly lower than that predicted by a linear mixed model for the data, whilst the population density close to NT2 fell to undetectable levels in 2011 from densities of over 5000 m^-2 in 2005. The NT2 dam began operation in 2010.

Conclusions

The impact of the NT2 dam on N. aperta population density could be more complex than first thought and may reflect the strict ecological requirements of this snail. There was no indication that responses of N. aperta populations to dam construction are similar to those observed with Bulinus and Schistosoma haematobium in Africa, for example. In view of the present findings, more ecological data (in particular population density monitoring and surveillance for new habitats) are urgently required in order to understand properly the likely impacts of water resource development on Mekong schistosomiasis.

Development of a real-time PCR assay with fluorophore-labelled hybridization probes for detection of Schistosoma mekongi in infected snails and rat feces

Schistosoma mekongi, a blood-dwelling fluke, is a water-borne parasite that is found in communities along the lower Mekong River basin, i.e. Cambodia and Lao People's Democratic Republic. This study developed a real-time PCR assay combined with melting-curve analysis to detect S. mekongi in laboratory setting conditions, in experimentally infected snails, and in fecal samples of infected rats. The procedure is based on melting-curve analysis of a hybrid between an amplicon from S. mekongi mitochondrion sequence, the 260 bp sequence specific to S. mekongi, and specific fluorophore-labelled probes. This method could detect as little as a single cercaria artificially introduced into a pool of 10 non-infected snails, a single cercaria in filtered paper, and 2 eggs inoculated in 100 mg of non-infected rat feces. All S. mekongi-infected snails and fecal samples from infected rats were positive. Non-infected snails, non-infected rat feces, and genomic DNA of other parasites were negative. The method gave high sensitivity and specificity, and could be applied as a fast and reliable tool for cercarial location in water environments in endemic areas and for epidemiological studies and eradication programmes for intermediate hosts.

False-positive Plasmodium falciparum histidine-rich protein 2 immunocapture assay results for acute schistosomiasis caused by Schistosoma mekongi

We report seven cases of false-positive Plasmodium falciparum histidine-rich protein 2 (PfHRP2) malaria assay results in patients with acute schistosomiasis caused by Schistosoma mekongi. PfHRP2 assays were negative in travelers infected with Schistosoma mansoni or Schistosoma haematobium (n = 13). Malaria was ruled out and rheumatoid factor was negative in all patients.

Pulmonary vascular disease associated with schistosomiasis

In this article we focus on the pathogenesis and clinical characteristics of schistosomiasis infection on the lung vasculature. Overall, the basic biology and understanding of Schistosoma immune responses and their effect on the cardiopulmonary system is limited in both animal and human models, which hinders clinical care and drug development. The inflammatory response to the eggs in the lung appears to contribute to the remodeling of the pulmonary vessels. Portal hypertension caused by parasitemia also appears to contribute to the development of pathophysiologic alterations of the pulmonary vascular bed. Antischistosomal therapy, praziquantel, used for pulmonary hypertension secondary to schistosomiasis usually has no effect, but it is given to prevent further progression of disease. Currently, there are no clinical trials for the treatment of pulmonary vascular disease secondary to schistosomiasis. Specialty drugs such as phosphodiesterase type 5 or tyrosine kinase inhibitors exhibit some interesting activity, yet are prohibitively expensive, lack safety and efficacy studies in schistosomiasis endemic populations, and tend to be limited by safety, efficacy, route of administration and compliance problems.

Schistosoma mekongi in Cambodia and Lao People's Democratic Republic

Schistosomiasis found in communities along the Mekong River in Cambodia and Lao People's Democratic Republic (Lao PDR) is caused by the blood fluke Schistosoma mekongi. Early observations on patients in 1957 revealed severe intestinal and hepatosplenic disease. High mortality rates and widespread disease were reported from the provinces of northern Cambodia (Stung Treng and Kratié) and southern Lao PDR (Champasack) in the early 1970s and 1990s. Control programmes built around mass drug administration, with praziquantel, and combined with information and education campaigns, were carried out. In Cambodia, such programmes were started in 1995 in the endemic provinces and sustained until today; these efforts resolved the public health problem of schistosomiasis mekongi and led to a significant reduction in transmission. In Lao PDR, the interventions started in the late 1980s, but suffered several interruptions which permitted transmission to resume. Today, a number of small foci continue to show substantial prevalence rates. The snail intermediate host, Neotricula aperta, is present in the Mekong River and some of its tributaries. There is evidence that the snail might not yet have reached its full geographical distribution emphasising the need to sustain vigilance. New infections with S. mekongi occur in the endemic population and travellers alike. Comprehensive guidelines for the elimination of S. mekongi and bilateral efforts between Cambodia and Lao PDR are required.

Acute schistosomiasis, a diagnostic and therapeutic challenge

In non-endemic countries, acute (invasive) schistosomiasis (AS) is typically seen in non-immune travellers, whereas chronic schistosomiasis is more frequently diagnosed in immigrants. Travellers with AS initially present with non-specific signs such as fever, cough, headache, and urticaria. Life-threatening cardiac and neurological complications may occur. The positive diagnosis of AS relies on seroconversion, which appears together with hypereosinophilia approximately 3 weeks after the onset of symptoms. When prescribed during AS, praziquantel usually does not prevent the chronic phase of the disease and is associated with exacerbation of signs and symptoms in approximately 50% of cases. According to the published literature, corticosteroids may be recommended alone or in association with praziquantel. When associated with corticosteroids, pharmacokinetic interactions may impair the efficacy of praziquantel. We suggest that corticosteroids should be restricted to use in patients with systemic complications of AS, whereas praziquantel should be initiated only when ova are detected in either stools or urine, depending on the culprit species.