Comparison of novel and standard diagnostic tools for the detection of Schistosoma mekongi infection in Lao People’s Democratic Republic and Cambodia

Background:Given the restricted distribution of Schistosoma mekongi in one province in Lao People’s Democratic Republic(Lao PDR)and two provinces in Cambodia,together with progress of the national control programmes aimed at reducing morbidity and infection prevalence,the elimination of schistosomiasis mekongi seems feasible.However,sensitive diagnostic tools will be required to determine whether elimination has been achieved.We compared several standard and novel diagnostic tools in S.mekongi-endemic areas.Methods:The prevalence and infection intensity of S.mekongi were evaluated in 377 study participants from four villages in the endemic areas in Lao PDR and Cambodia using Kato-Katz stool examination,antibody detection based on an enzyme-linked immunosorbent assay(ELISA)and schistosome circulating antigen detection by lateral-flow tests.Two highly sensitive test systems for the detection of cathodic and anodic circulating antigens(CCA,CAA)in urine and serum were utilized.Results:Stool microscopy revealed an overall prevalence of S.mekongi of 6.4%(one case in Cambodia and 23 cases in Lao PDR),while that of Opisthorchis viverrini,hookworm,Trichuris trichiura,Ascaris lumbricoides and Taenia spp.were 50.4%,28.1%,3.5%,0.3%and 1.9%,respectively.In the urine samples,the tests for CCA and CAA detected S.mekongi infections in 21.0%and 38.7%of the study participants,respectively.In the serum samples,the CAA assay revealed a prevalence of 32.4%,while a combination of the CAA assay in serum and in urine revealed a prevalence of 43.2%.There was a difference between the two study locations with a higher prevalence reached in the samples from Lao PDR.Conclusions:The CCA,CAA and ELISA results showed substantially higher prevalence estimates for S.mekongi compared to Kato-Katz thick smears.Active schistosomiasis mekongi in Lao PDR and Cambodia might thus have been considerably underestimated previously.Hence,sustained control efforts are still needed to break transmission of S.mekongi.The pivotal role of highly sensitive diagnostic assays in areas targeting elimination cannot be overemphasised.

How elimination of lymphatic filariasis as a public health problem in the Kingdom of Cambodia was achieved

Background:Endemicity of lymphatic filariasis(LF)in Cambodia was proven in 1956 when microfilariae were detected in mosquitos in the Kratiéprovince.In 2001,an extensive study confirmed the presence of both Brugia malayi and Wuchereria bancrofti microfilariae.In 2003,the Ministry of Health established a national task force to develop policies and strategies for controlling and eliminating neglected tropical diseases(NTDs),with the goal of eliminating LF by 2015.This article summarizes the work accomplished to eliminate LF as a public health problem in Cambodia.Methods:The National Program to Eliminate Lymphatic Filariasis made excellent progress in the goal towards elimination due to strong collaboration between ministries,intensive supervision by national staff,and advocacy for mobilization of internal and external resources.Mass drug administration(MDA)with diethylcarbamazine citrate and albendazole was conducted in six implementation units,achieving>70%epidemiological coverage for five consecutive rounds,from 2005 to 2009.In 2006,in 14 provinces,healthcare workers developed a line list of lymphedema and hydrocele patients,many of whom were>40 years old and had been affected by LF for many years.The national program also trained healthcare workers and provincial and district staff in morbidity management and disability prevention,and designated health centers to provide care for lymphedema and acute attack.Two reference hospitals were designated to administer hydrocele surgery.Results:Effectiveness of MDA was proven with transmission assessment surveys.These found that less than 1%of school children had antigenemia in 2010,which fell to 0%in both 2013 and 2015.A separate survey in one province in 2015 using Brugia Rapid tests to test for LF antibody found one child positive among 1677 children.The list of chronic LF patients was most recently updated and confirmed in 2011-2012,with 32 lymphoedema patients and 17 hydrocele patients listed.All lymphedema patients had been trained on self-management and all hydrocele patients had been offered free surgery.Conclusions:Due to the success of the MDA and the development of health center capacity for patient care,along with benefits gained from socioeconomic improvements and other interventions against vector-borne diseases and NTDs,Cambodia was validated by the World Health Organization as achieving LF elimination as a public health problem in 2016.