Hello blood fluke enthusiasts,
Once again I am posting about my favourite parasite, the blood fluke called Schistosoma. I want to tell you about an exciting project that is going on on the beautiful archipelago of Zanzibar.
Zanzibar is a semi-autonomous archipelago of Tanzania. The two main islands are called Unguja (or Zanzibar island) and Pemba. We are working on a very exciting project to stop schistosomiasis transmission on these islands.
This is a bit of a long post but please if you can bear it read on! If successful this project could revolutionize our approach to schistosomiasis (blood fluke disease) control.
As I explained in my first blood fluke post, infection with the blood fluke Schistosoma causes a disease called Schistosomiasis (aka Bilharzia).
This disease affects over 200 million people worldwide, the majority living in sub-Saharan Africa. It is strongly linked to poverty and does heart-breaking damage to children and adults in the poorest and most vulnerable communities.
The clinical symptoms of schistosomiasis aka bilharzia, the blood fluke disease: (L) bloody urine from children excreting the parasite eggs through urination and (R) a malnourished child with a hugely enlarged liver due to damage caused by the parasite eggs stuck in the tissue.
Depending on the species of the infecting schistosome worms the disease can cause:
• Diarrhoea, bloody stool, blood in urine, painful urination.
• Anaemia, stunted growth, enlarged liver and spleen.
• Damage to the liver leading to liver fibrosis.
• Damage to the genitals, kidneys and bladder potentially leading to bladder cancer.
• Increased risk to sexually transmitted diseases like HIV.
Currently there is no vaccine. Schistosomes are masters of disguise when it comes to the immune system which means vaccines that rely on your immune system are difficult to develop. Researchers are trying though! Thankfully there is an effective oral drug called Praziquantel that kills the adult worms in humans. BUT it is the only effective drug against all species of this parasite, which raises concerns regarding drug resistance, and it does not stop people from becoming re-infected.
A boy being treated for schistosomiasis. The treatment is an oral dose of Praziquantel. Although the side-effects are minimal the pill is quite bitter and can cause stomach upsets so making sure a child has some yummy juice and a bit of food with treatment is important.
Up until now efforts to control schistosomiasis in sub-Saharan Africa have focused on regular treatment of school children to reduce infections and prevent the severity of the disease. The theory being that if you treat regularly you can prevent the child from developing those nasty outcomes listed above. The drug is donated and there are excellent NGOs providing support to programmes wishing to deliver the drugs to schools. Hurrah!
However this regular treatment approach has NOT interrupted schistosomiasis transmission in a sub-Saharan African country. This means it requires a (very) long term commitment from the programmes and ministries of health. A lot of these countries have weak and struggling health systems burdened with many challenges (lack of water & electricity, clean needles & surgical equipment, painkillers, antiseptic cream etc) as well as a whole range of poverty-loving diseases to deal with. How long can a struggling health system keep up 'regular' treatments in difficult to reach areas? Once these are missed, or the programme is interrupted, the disease comes back.
What about stopping transmission?
Elimination = stopping local transmission
This is is exactly what is being attempted in Zanzibar through a multi-institute and major collaborative project led by:
- The Zanzibar Ministry of Health.
- Public Health Laboratories Pemba.
- Our very own Prof David Rollinson, head of the schistosomiasis group here at the Museum.
There are three additional key players:
- My friend and colleague Dr Steffi Knopp from the Museum and the Swiss Tropical and Public Health Institute. Steffi is tirelessly overseeing the details and daily running of this project as well as analysing the results and publishing whatever new insight we get into schistosomiasis elimination from this ambitious project.
- SCORE (Schistosomiasis Consortium for Operational Research and Evaluation) funds this project with money from the Bill and Melinda Gates Foundation.
- Schistosomiasis Control Initiative, a wonderful NGO based at Imperial College providing countries with all the logistical and implementation support needed for national treatment programmes (they do accept donations and fundraising so if interested just get in touch.
Together (and with a few other people whom I have not mentioned and I do hope will forgive me), they form (drum roll please...):
ZEST – the Zanzibar Elimination of Schistosomiasis Transmission
(And now superhero music, or better yet Vangelis’ Chariots of Fire)
This project aims to answer the question:
What tools do we have to stop transmission and what is the most effective way of achieving this?
Transmission between humans and snails occurs in the local water bodies. In order to reach the water the parasite eggs come out with stool or urine. Because there are rarely toilets and no sewage system or human waste treatment facilities this human waste reaches the water that people frequent and the snails live in. The parasite is then able to continue its life cycle by first infecting a snail and then infecting a human.
So where on the life cycle can we intervene to stop transmission?
- We can kill the adult worms inside people by treating them with Praziquantel – Mass Drug Administration to communities at risk of infection.
- We can remove the intermediate host snail from the human water contact areas – Snail Control in local water contact sites.
- We can stop the eggs from reaching the water and warn people from going into known transmission sites – Behavioural Change Intervention.
A typical transmission site for schistosomiasis. Families come to the water to wash, clean, fish, etc.
These are the three interventions we have available to us. What is the most effective way to eliminate schistosomiasis in an area?
In order to test this ZEST has randomly organised all the distinct community areas of Zanzibar and Pemba into our three intervention groups:
A car full of donated Praziquantel treatment for schistosomiasis, about to head out to the communities.
Collecting urine samples from children to test for the presence of schistosoma eggs. This is how we diagnose schistososmiasis.
Spraying local water contact sites with a chemical that kills the aquatic snail host of schistosomes.
This is a familiar face to you I’m sure, Dr Fiona Allan our resident schistosome snail expert surveying sites in Zanzibar. She has a sixth sense on where the snails will be and where transmission occurs. We are now calling her 'snail whisperer'.
1. Mass Drug Administration – Treatment of communities twice a year with Praziquantel. Now the truth is it would be unethical not to treat people we know to be suffering from the disease purely in the name of science. We may be scientists but we’re not evil scientists! So EVERYONE on BOTH ISLANDS IS GETTING TREATMENT. But in group 1 they are ONLY receiving treatment. No snail control, no behavioural intervention. This is to test the effectiveness of the current approach (treating people regularly).
2. Snail Control - Snail Control by spraying transmission sites with a safe and gentle dose of Niclosamide. The communities are receiving treatment as normal however their villages have been surveyed for human-snail water contact and schistosomaisis transmission sites. These sites then get sprayed with the molluscicide (chemical that kills snails) Niclosamide. Niclosamide is also used as parasite treatment for livestock and is safe for mammals and birds. It does kill all snails though so we only want to use it in the areas that have transmission, nowhere else. We also know that it quickly breaksdown in the environment. This is good because it means it does not linger around however it’s also bad because a good rain storm and off it goes down the river without killing any schistosome infected snails.
3. Behavioural Change Intervention – Mobilizing communities by teaching them about schistosomiasis transmission and supporting them to find their own solutions. Education teams go out to the communities, teach the village leaders, the religious leaders, the teachers about schistosomaisis and the blood fluke life cycle. They then help the communities to develop ways of raising awareness of schistosomiasis, educating parents and children and encouraging positive behaviour change that will prevent disease transmission. This has taken form of:
- Special Kichocho (Swahili word for schistosomiasis) events, where safe games are played, little educational sketches are watched and fun is had.
- Training teachers to teach children at schools about the schistosoma life cycle.
- Building latrines and urinals for children and adults to use instead of urinating outside.
- Making signs warning people of the presence of kichocho in the water and the risk of infection.
- Other solutions like safe clothes washing areas etc.
Big red signs warning the community about the presence of Kichocho (schistosomes) and konokono (snails - intermediate hosts of schistosomes) in the local water.
The behavioural intervention team on Pemba and Michael, an MSc student from the University of Tulane, with the help of the wonderful behaviour scientist Dr Bobbie Person, have created an amazing educational video in Kiswahili to show in villages and schools. Do take a look - it is fantastic!
A video made by the schistosomiasis behaviour intervention team on Pemba with the help of Michael Celone to teach communities about the life cycle of Kichocho (schistosomiasis). The video is in Kiswahili with English subtitles.
A second video teaching communities about behaviours that increase transmission and risk of infection as well as what they can do to prevent Kichocho (schistosomiasis). The video is in Kiswahili with English subtitles.
The Zanzibar Elimination of Schistosomiasis Transmission study design. MDA – Mass drug administration of safe anti-schistosomal drug Praziquantel delivered to the villagers twice a year. Snail Control – removing snails in human water contact sites by spraying with safe molluscicide Niclosamide. Behaviour Intervention – Community-lead behavioural change intervention to stop behaviour that leads to transmission/infection of schistosomes.
Wish us luck and watch this space!