Decline in transmission of schistosomiasis mansoni in Oman

Abstract

BackgroundIntestinal schistosomiasis due to Schistosoma mansoni was first reported in Oman in 1979. We describe the trend in parasitological and serological prevalence of human infection with S. mansoni in the endemic area over the period 1982–2014, and the compliance of data generated by the national monitoring and evaluation system with schistosomiasis elimination criteria set by the Ministry of Health of Oman.MethodsParasitological and serological assessments were carried out on population (mainly children) living in the area at risk for schistosomiasis in Dhofar, the country’s only endemic Governorate, for a period of over 30 years. Kato-Katz thick smear and Indirect Haemagglutination Assay were the techniques employed.ResultsData indicate a progressive decline in prevalence of S. mansoni throughout the 1980s and the 1990s, a recrudescence in the early 2000s, and a more marked decrease following the implementation of six rounds of mass treatment with praziquantel from 2007 to 2013. Latest parasitological prevalence (2011) was 0%, while latest serological prevalence (2014) was 0.11%.ConclusionTransmission of schistosomiasis has reached very low levels in Oman. Elimination criteria established by the Ministry of Health of Oman (parasitological prevalence ≤ 1% and serological prevalence ≤ 5%) have been met since 2008. Further investigations are required to assess whether interruption of transmission has been achieved in some or all foci, in view of the establishment of a formal verification process under the auspices of WHO.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0210-1) contains supplementary material, which is available to authorized users.

Core components, concepts and strategies for parasitic and vector-borne disease elimination with a focus on schistosomiasis: A landscape analysis

“…The views of key informants were confirmed by the findings from the literature review, where countries including Oman, Venezuela, Lao PDR, Cambodia and P.R. China reported the successful combination of targeted schistosomiasis screening and selective/targeted treatment with the aim to avoid the treatment of non-infected individuals and to increase compliance for treatment against Schistosoma infections in endemic areas [ 20 – 29 ]. The value for decision-making of tailored interventions to target asymptomatic carriers contributing to transmission through community-wide mass drug treatment and active case finding, in addition to mapping spatial and temporal transmission dynamics, has been established for malaria [ 30 – 34 ].…”

“…Concepts for schistosomiasis surveillance systems designed for elimination programs, including early warning systems [ 25 , 58 , 82 – 85 ], mapping of hot spots and modelling for targeted approaches [ 58 , 83 , 86 ] are covered in several reviewed articles. Challenges due to the lack of sensitive diagnostic tools for monitoring and validating stages of elimination in regards to low-prevalence settings and low intensity infections were discussed in articles pertaining to schistosomiasis control programs in Morocco [ 87 ], Venezuela [ 21 , 23 ], Oman [ 20 ] and P.R. China [ 28 ].…”

“…Most of the identified articles that focus on strategies for implementation of interventions refer to the Chinese schistosomiasis control programme. They describe a combination of tools and comprehensive strategies [ 11 , 20 , 21 , 23 , 36 , 90 , 92 – 94 ] implemented through collaborations between multiple sectors but under central coordination [ 26 , 29 , 39 , 95 , 96 ]. This approach has been identified as important to reduce schistosomiasis japonica levels across P.R.…”

Elimination of schistosomiasis: the tools required

“…However, with at least 218 million people requiring preventive treatment in 2015 and 66.5 million people treated, this disease must be deemed to have a low drug coverage compared to many other NTDs [ 4 ]. This notwithstanding, Morocco and Oman are already at the surveillance-and-response stage as discussed in five articles in this special issue dealing with the possibility of actually eliminating the disease there within the next few years [ 30 , 31 ]. However, the achievements made have to be sustained and the transition from infection control to transmission control requires guidelines how to proceed [ 32 ].…”

“…In contrast to Morocco, schistosomiasis ( S. mansoni ) in Oman was first reported in 1979 [ 35 ], although it might well have existed earlier. Recent data indicate a progressive prevalence decline throughout the 1980s and the 1990s and the disease is now said to have been eliminated [ 30 ]. However, further investigations with sensitive diagnostics along the lines used in Morocco [ 31 ] would be required to certify this.…”