Prevalence of Schistosoma japonicum infection in water buffaloes in selected areas in Davao del Norte and Davao de Oro, the Philippines

Transmission-Blocking Vaccines against Schistosomiasis Japonica

Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can generate 1000-2200 eggs per day, which is about 3- to 15-fold greater than the egg output of other schistosome species. Bovines (water buffalo and cattle) are the predominant definitive hosts and are estimated to generate up to 90% of parasite eggs released into the environment in rural endemic areas where these hosts and humans are present. Here, we highlight the necessity of developing veterinary transmission-blocking vaccines for bovines to better control the disease and review potential vaccine candidates. We also point out that the approach to producing efficacious transmission-blocking animal-based vaccines before moving on to human vaccines is crucial. This will result in effective and feasible public health outcomes in agreement with the One Health concept to achieve optimum health for people, animals, and the environment. Indeed, incorporating a veterinary-based transmission vaccine, coupled with interventions such as human mass drug administration, improved sanitation and hygiene, health education, and snail control, would be invaluable to eliminating zoonotic schistosomiasis.

Fasciola spp. in Southeast Asia: A systematic review

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 1st, 2000, and June 30th, 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.

The status of schistosomiasis japonica control in the Philippines: The need for an integrated approach to address a multidimensional problem

Schistosomiasis japonica remains a public health concern in many areas of the Philippines. Adequate and updated information is essential to enhance policy and service delivery toward control and elimination. Despite the efforts on schistosomiasis control in the Philippines, some challenges remain in these dimensions. An integrated surveillance system is recommended to determine the prevalence of infection in humans, animal reservoirs, and snail intermediate hosts, allowing the identification of high-priority areas for targeted interventions. This will entail the enhancement of laboratory diagnosis capacity through the use of more sensitive techniques, complemented by capacity building of concerned human and animal health professionals. Given the zoonotic nature of schistosomiasis japonica, adopting the One Health approach is essential to influence policies and interventions that may accelerate control and elimination. This can be achieved through the attainment of mass drug administration coverage targets and intensified case finding and management, robust implementation and integration of veterinary public health activities, the conduct of snail control measures, provision of safe water, sanitation, and hygiene services, and health promotion and education into the national schistosomiasis control and elimination program. This review aimed to describe the status of schistosomiasis japonica control in the Philippines in the context of human health, animal health, vector ecology and management, environmental health, and sociocultural dimensions.