31 October 2018

Schistosomiasis in Kenya: an interview with Dr. Maurice R. Odiere

The forthcoming Phase III clinical trial of the Pediatric Praziquantel (PZQ) Consortium Formulation program will be conducted in Kenya, in addition to the Ivory Coast.

We asked Dr. Maurice R. Odiere, Head of the Neglected Tropical Diseases (NTD) Unit at the Centre for Global Health Research, Kenya Medical Research Institute (KEMRI), how the new formulation might impact schistosomiasis in Kenya, and about his work on diagnosis, treatment and operational challenges across different areas of Kenya.

How big is the challenge presented by schistosomiasis in Kenya?
The Schistosoma parasite is endemic in 158 of the 290 sub-counties in Kenya. Around six million people remain at risk from this disease, and 70% of these are in the 5-14 age group. There are three major endemic areas: the Coastal region (mainly Schistosoma haematobium), parts of Central and Lower Eastern areas (both S. haematobium & S. mansoni) and the Lake Victoria basin (mainly S. mansoni). Transmission is still commonplace in many areas, with people becoming infected during a wide range of activities such as domestic, agricultural and commercial. Exposure to the parasitic worm can happen while car washing, sand harvesting, fishing, and during recreation such as swimming.

What has been done to address the disease up to this point?
KEMRI is a key partner in the National School-Based Deworming Program (NSBDP), working with the Ministries of Health and Education and other partners. Our own work at the KEMRI NTD Unit (at the Centre for Global Health Research in western Kenya) has focused on understanding disease transmission dynamics, burden and morbidity, and immunity/resistance to infection. We also explore operational research on controlling schistosomiasis, and we evaluate new diagnostic tools for program managers. Kenya’s second National Strategic Plan for Control of Neglected Tropical Diseases (NTDs) 2016-2020 is currently underway with a focus on reducing schistosomiasis through periodic, targeted treatment using PZQ for large-scale preventive chemotherapy.

What is the impact of schistosomiasis in pre-school children?
Sensitive diagnostic approaches such as using multiple stool samples or serologic assays show that a sizeable proportion of young children is infected, confirming the urgent and acknowledged need for a formulation of PZQ for infants. Children currently have to wait for treatment until they are at least 5 years old, and this is a problem for two reasons. First, ultrasound examinations have shown evidence of liver changes in some children at an early age; so infection is not free of harm. Second, it is not possible to interrupt transmission while a reservoir of infection remains. We are therefore very committed to confirming the potential of the new pediatric PZQ formulation.

Is PZQ the only solution to schistosomiasis?
PZQ is extremely important, but drugs cannot meet the challenge on their own. At the KEMRI NTD Unit, we have conducted social and behavioral studies to identify activities that contribute to transmission. Long-term success depends on engaging properly with affected communities, rather than relying on a top-down ‘treat and leave’ approach. Some communities have taken part in community-directed intervention (CDI) approaches, where the community is empowered to take charge and ensure that interventions are sustained. This helps to address systematic non-compliance and areas that are difficult to reach, and we are currently comparing community-wide with school-based mass drug administration strategies.
Assessing different diagnostic tools is another essential element of our work. Widely used existing tools are limited by suboptimal sensitivity, slow turn-around time, or inability to distinguish between current and former infections. We have shown that a point-of-care circulating cathodic antigen assay (POC-CCA) may be a good field-friendly alternative both to Kato-Katz stool examinations and to an anti-schistosome enzyme-linked immunosorbent.

What else are you working on?
The basic attributes of schistosomes continue to be assessed, and important implications are emerging for other diseases. For example, we have found that patients with active schistosomiasis display higher cell surface densities of CCR5 and CXCR4 receptors – which are also co-receptors for invasion of cells by human immunodeficiency virus (HIV) type 1. There are additional potential health implications in areas as diverse as tuberculosis, cervical cancer and immune reconstitution inflammatory syndrome (IRIS). Collaboration with different partners is essential if we are to address these challenges, and KEMRI has many links with other organizations.

We also look at persistent hotspots – villages that resist elimination of the parasite – and we have seen that mass drug administration can be less effective in such hotspots compared with other villages. Finding ways to identify hotspots is important, because it changes our intervention strategies.

What comes next?
In addition to the forthcoming clinical trial together with the National NTD program, we are exploring how to tailor interventions to specific settings, such as western Kenya where transmission is high (and where a focus on morbidity is appropriate), and areas with low transmission, where elimination is a realistic goal. Education is key for populations and for frontline health care workers. We are also engaging with other health partners to capture data that needs to be shared more widely. Operational research remains an important ongoing element, giving operational managers new strategies and tools that can be layered onto existing activities.