Tackling the lack of uniformity in Schistosomiasis Transmission

by Prof. Louis-Albert Tchuem Tchuente, Pamela Bongkiyung, Prof. Russell Stothard

Schistosomiasis or Bilharzia or snail fever as some call it remains one of the neglected tropical diseases (NTDs) that is ravaging many poor people around the world. They thrive in areas with poor sanitation, often inhabited by those with limited to no access to health care. It can cause liver damage or sterility in women. A major symptom is having blood in urine. Controlling this NTD remains a great challenge given that its transmission has no uniformity across countries.

In Africa, the dynamic of transmission is not uniform – it differs from one area to another even in the same country. In Cameroon for example, the transmission is not uniform because what happens in one locality is completely different from others, the dynamic of transmission is different, the snails’ species are different, the interactions between the snails and parasites are different, the re-infection rates also differ. It is important to understand all these aspects and we need more scientists working on this.

Schistosomiasis has different species which vary from Asia to those in Africa. Praziquantel is effective in all six-human species of schistosomiasis. Speaking to Prof. Louis-Albert, we learn that in Cameroon – a West Central African country; there are three species of human schistosomiasis, one specie responsible for urogenital schistosomiasis – Schistosoma haematobium and two responsible for intestinal schistosomiasis – Schistosoma mansoni and Schistosoma guineensis. schistosoma intercalatum is the fourth specie, making a total of four species in Africa. The same drug – Praziquantel is used against all four species and the two-other species prevalent only in Asia – Schistosoma japonicum and Schistosoma mekongi. Both continents use different formulations of Praziquantel.

A major challenge to schisto control and elimination has been controlling human interactions with the water snails. How can African countries extrapolate from the Chinese experience?  According to Prof. Tchuem-Tchuenté, there has to be a change in human behaviour and control of the snail. If there is no snail, there is no schisto. That is why snail control remains key for a move towards elimination.

The Problem with Snail Control 

This was a major control strategy in the 70s but because of the high cost it was abandoned. China has now developed many molluscicides and they have a vast experience on this. With all these new chemicals, it is hoped the cost of snail control will be reduced and that the snail control will make a comeback on the agenda so that it can be integrated to MDA with snail control in other activities of WASH (Water, Sanitation & Hygiene). With this integrated approach, perhaps we can move towards transmission control and elimination.

 People still live in very organic set-ups in schisto endemic areas compared to China where a lot of town planning has been done. How can we successfully implement the aspect of hygiene (WASH) or improve people’s behaviours in controlling schisto?

This is mainly linked to the economic situation in many countries postulates Prof.  Tchuem-Tchuenté. He further advances that to improve hygiene and have health education to modify people’s behaviour, it is necessary that their standards of living increase. To this end, more investment is needed.

“Within the countries, more resources need to be allocated to the control of this disease so that we shift completely from the word ‘control’ to ‘elimination’. If we keep using the word control, you find that we will stay in the same place. If we increase our ambition to elimination, the increase of resources to achieve this goal will be automatic. The country will have no choice but to increase their resources in line with the Sustainable Development Goals”, said Prof. Tchuem-Tchuenté.

The priority intervention for schistosomiasis control is preventive chemotherapy using mass drug administration as the treatment. However, treatment alone is not the solution to interrupt transmission; because reservoirs still exist with the adult population. The current focus is on school-aged children but the parasites exist in people not targeted such as pre-school children and adults. Even if there is high coverage of the school-aged children, lowering transmission and prevalence, there will be a patch of the community with some parasite reservoirs that will maintain the transmission cycle. Recently, there has been attempts to extend treatment to all population age-groups.

(Photo courtesy of Dr Suzy Campbell - Ghana)

In addition to treatment, it is very important that the intervention addresses water-contact and hygiene. This explains why WASH activities have been included in control solutions. In the recent WHO NTD report titled ‘Integrating Neglected Tropical Diseases into Global Health and Development’, it was highlighted that providing safe water, sanitation and hygiene (known as WASH) is critical for preventing and providing care for most NTDs. WASH component of the NTD strategy has tended to be neglected relative to its importance. There is also environmental modification because these diseases are linked to the poverty – lack of hygiene. If there is no open defecation into the environment, we can reduce the transmission of schistosomiasis and then you can interrupt it. If open defecation continues and some part of the population still have no access to latrines, defecating or urinating into the environment will not be stopped. With treatment, this population will remain at the risk of re-infection and the disease can be re-introduced and spread anew.

Another area of schistosomiasis research that is garnering more attention these days is female genital Schistosomiasis (FGS) or urogenital schistosomiasis. COUNTDOWN has incorporated some elements of FGS into its research work in Ghana.

Read below more publications with input from COUNTDOWN researchers, engaging in knowledge cross-share with other researchers and programmes on various areas relating to schistosomiasis.

Paediatric and maternal schistosomiasis: shifting the paradigms by Amaya L Bustinduy, J Russell Stothard, Jennifer F Friedman

Female genital schistosomiasis (FGS) in Ogun State, Nigeria: a pilot survey on genital symptoms and clinical findings by U F Ekpo, O M Odeyemi, S O Sam-Wobo, O B Onunkwor, H O Mogaji, A S Oluwole, H O Abdussalam, J R Stothard

COUNTDOWN will be at the upcoming British Society of Parasitology Autumn Symposium, taking place on 28th September 2017. We will be presenting our work from Cameroon highlighting challenges relating to helminthiasis control, how  NTDs are faring amidst changing partnerships, networks and global health policies on the development agenda. There will be a presentation on the evolving needs of vector-borne diseases surveillance across the world. We hope to see you there or engage with you on social media. Tweet us @NTDCOUNTDOWN

Visit https://countdownonntds.wordpress.com/  and http://countdowncameroon.org/blogs/ for more on COUNTDOWN's work.