National survey data for zoonotic schistosomiasis in the Philippines grossly underestimates the true burden of disease within endemic zones: implications for future control

Abstract

Zoonotic schistosomiasis has a long endemic history in the Philippines. Human mass drug administration has been the cornerstone of schistosomiasis control in the country for the past three decades. Recent publications utilizing retrospective national survey data have indicated that the national human prevalence of the disease is <1%, hence the disease is now close to elimination. However, the evidence for such a claim is weak, given that less than a third of the human population is currently being treated annually within endemic zones and only a third of those treated actually swallow the tablets. For those who consume the drug at the single oral dose of 40mg/kg, the estimated cure rate is 52% based on a recent meta-analysis. Thus, approximately 5% of the endemic human population is in reality receiving the appropriate treatment. To compound this public health problem, most of the bovines in the endemic communities are concurrently infected but are not treated under the current national control programme. Given this evidence, it is believed that the human prevalence of schistosomiasis within endemic regions has been grossly underestimated. Inherent flaws in the reporting of national schistosomiasis prevalence data are reported here, and the problems of utilizing national retrospective data in making geographic information system (GIS) risk maps and advising policy makers of the outcomes are highlighted.

Biennial versus annual treatment for schistosomiasis and its impact on liver morbidity

“…3 In the Philippines, over 865 000 people are estimated to have schistosomiasis, with another 12 million exposed to the disease. 4,5 The poverty-stricken regions of the Visayas (Samar and Leyte) and Mindanao are the main endemic foci (80%) in the country. These include 28 provinces, 190 municipalities, and 2230 barangays (villages).…”

“…According to the Philippines National Schistosomiasis Control Programme, the recent human prevalence has dropped to less than 3% nationwide. 5,6 However, contradictory reports have stated that the programme is failing due to poor drug compliance, poor drug coverage, irregular monitoring and evaluation, and rapid reinfection rates. [4][5][6] Moreover, recently published data reported a very high prevalence of the disease in both humans and bovines throughout the country.…”

“…5,6 However, contradictory reports have stated that the programme is failing due to poor drug compliance, poor drug coverage, irregular monitoring and evaluation, and rapid reinfection rates. [4][5][6] Moreover, recently published data reported a very high prevalence of the disease in both humans and bovines throughout the country. [4][5][6] Advanced schistosomiasis cases and related deaths are currently being reported by the National Department of Health for Mindanao, Samar, Leyte, and Oriental Mindoro.…”

“…[4][5][6] Moreover, recently published data reported a very high prevalence of the disease in both humans and bovines throughout the country. [4][5][6] Advanced schistosomiasis cases and related deaths are currently being reported by the National Department of Health for Mindanao, Samar, Leyte, and Oriental Mindoro. 6 Hepatic fibrosis is the major cause of morbidity and mortality among people with chronic schistosomiasis.…”

Statistical evaluation of spatial uncertainty in schistosomiasis mapping

“…For the purpose of this study, it was decided to work at a local spatial scale in the Province of Leyte, due to the localized nature of the surveys and the high endemicity of the disease (Olveda et al, 2016). For the analysis, we identified a small area surrounding surveyed points (Figure 3.1).…”