Fasciola spp. in Southeast Asia: A systematic review

Abstract

Background

Fasciolosis is an emerging public health threat in a number of regions worldwide. To date, we lack an overview of both its occurrence and distribution in Southeast Asia across all actors involved in the life cycle, which impedes the development of disease control measures. Therefore, our objective was to collect recent information on the distribution and the prevalence of Fasciola spp. and the associated risk factors for infection in humans, animals, snails and plant carriers in Southeast Asia.

Methodology

Bibliographic and grey literature databases as well as reference lists of important review articles were searched for relevant records published between January 1 ^st, 2000, and June 30 ^th, 2022. The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for reporting systematic reviews. A total of 3,887 records were retrieved, of which 100 were included in the final analysis.

Principal findings

The studies focused mainly on one host species (96.0%), with Fasciola spp. infection in animals being the most studied (72.0%), followed by humans (21.0%). Based on the used inclusion and exclusion criteria, reports were retrieved describing the presence of Fasciola spp. infection in seven out of 11 countries in Southeast Asia. Depending on the diagnostic tool applied, the prevalence of Fasciola spp. infection ranged between 0.3% and 66.7% in humans, between 0% and 97.8% in animals, and between 0% and 66.2% in snails. There were no studies reporting the presence of metacercariae on plant carriers.

Conclusions/Significance

Our study reconfirms that Fasciola spp. infections are widespread and highly prevalent in Southeast Asia, but it remains difficult to accurately assess the true occurrence of Fasciola spp. in absence of well-designed surveys covering all hosts. As next steps we propose to assess the occurrence of the infection across all actors involved in the transmission, to identify associated risk factors and to estimate the burden of the disease to support national and international decision makers.

Author summary

Fasciolosis is a foodborne disease that is caused by a parasitic worm. The disease affects both public and animal health worldwide. The transmission of Fasciola is complex and involves humans, animals and plants. The adult worms are observed in both humans and ruminants, while larval stages develop in freshwater snails. The infective larval stage attaches to aquatic plants. In recent decades, human fasciolosis has been considered an emerging disease in many regions of the world, including Southeast Asia. Although various studies surveyed Fasciola infection, an overview of existing knowledge on the distribution and prevalence of Fasciola across the different hosts is missing for this region. Yet, this is important to develop appropriate disease control measures. In this study, we systematically searched for literature on Fasciola spp. infection in Southeast Asia. Our study reconfirms that Fasciola is widespread in this region, but that it remains difficult to accurately assess the occurrence of parasite in the absence of well-designed surveys. A firm response to control fasciolosis requires both transdisciplinary and international partnerships. As next steps we propose to assess the occurrence of Fasciola spp. across all actors involved in the transmission, to identify associated risk factors and to estimate the disease burden to support national and international decision makers.