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Super-flies and parasites

7 Posts tagged with the health tag

On 25 June the Museum will open its doors to a special event in celebration of the international and global commitment between countries, industry, charities and academia to work together against Neglected Tropical Diseases (NTDs). This commitment was first agreed upon in London in 2012 and has since been termed the London Declaration On NTDs.


By joining forces to fight NTDs the world would achieve a huge reduction in health inequality paving the way to sustainable improvements in health and development especially amongst the worlds poor. The 25 June sees the launch of the third progress report, 'Country Leadership and Collaboration on Neglected Tropical Diseases'. A pragmatic overview of what has been done, what has worked, what hasn't and what key areas still need to be achieved.


The Museum is thrilled to be participating in this event, having a long-standing history in parasitic and neglected tropical disease research. As both a museum and an institute of research our mission is to answer questions of broad significance to science and society using our unique expertise and collections and to share and communicate our findings to inspire and inform the public. We are excited to be hosting a day of free public events on Neglected Tropical Diseases.


What are NTDs?

Neglected Tropical Diseases are termed in this way because they infect hundreds of thousands to millions of people, predominantly the world's poorest and most vulnerable communities, and yet receive comparatively little funding for basic, clinical or drug-development research and even less attention from governments, people and the media of affluent countries. Until now!


In total the WHO has identified 17 diseases or groups of diseases that fall within this category.


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World Health Organization has identified 17 Neglected Tropical Diseases. 10 of these have been targeted for control and elimination by 2020


The 10 selected by the WHO for control and elimination by 2020 are:


  1. Onchocerciasis (aka river blindness): A blood worm infection transmitted by the bite of infected blackflies causing severe itching and eye lesions as the adult worm produces larvae and leading to visual impairment and permanent blindness.
  2. Dracunculiasis (aka Guinea-worm disease): A roundworm infection transmitted exclusively by drinking-water contaminated with parasite-infected water fleas. The infection leads to meter-long female worms emerging from painful blisters on feet and legs to deposit her young. This leads to fever, nausea and vomiting as well as debilitating secondary bacterial infections in the blisters.
  3. Lymphatic filariasis: A blood & lymph worm infection transmitted by mosquitoes causing abnormal enlargement of limbs and genitals (elephantiasis) from adult worms inhabiting and reproducing in the lymphatic system.
  4. Blinding trachoma: A chlamydial infection transmitted through direct contact with infectious eye or nasal discharge, or through indirect contact (e.g. via flies) with unsafe living conditions and hygiene practices, which if left untreated causes irreversible corneal opacities and blindness. Trachoma is the leading cause of blindness in the word.
  5. Schistosomiasis (aka bilharzia): A blood fluke infection transmitted when larval forms released by freshwater snails penetrate human skin during contact with infested water. The infection leads to anaemia, chronic fatigue and painful urination/defaecation during childhood, later developing into severe organ problems such as liver and spleen damages, bladder cancer, genital lesions and infertility.
  6. Visceral leishmaniasis (aka Kala azar): A protozoan blood parasite transmitted through the bites of infected female sandflies which attacks internal organs which can be fatal within 2 years. 
  7. Soil-transmitted helminths: A group on intestinal worm infections transmitted through soil contaminated by human faeces causing anaemia, vitamin A deficiency, stunted growth, malnutrition, intestinal obstruction and impaired development.
  8. Leprosy: A complex disease caused by infection mainly of the skin, peripheral nerves, mucosa of the upper respiratory tract and eyes.
  9. Chagas disease: A life-threatening illness caused by a blood protozoan parasite, transmitted to humans through contact with vector insects (triatomine bugs), ingestion of contaminated food, infected blood transfusions, congenital transmission, organ transplantation or laboratory accidents.
  10. Human African trypanosomiasis (aka sleeping sickness): A protozoan blood parasitic infection spread by the bites of tsetse flies that is almost 100% fatal without prompt diagnosis and treatment to prevent the parasites invading the central nervous system.


They were selected because the tools to achieve control are already available to us and, for some, elimination should be achievable.


Take the Guinea Worm:


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Guinea worm infection - from over 3.5 million people infected in the 80s to less than 130 cases in 2014. Set to be second human disease to be eradicated after smallpox (photo credits David Hamm&Peter Mayer)


In the 1980s over 3.5 million people were infected with Dracunculiasis (i.e. Guinea worm disease), with 21 countries being endemic for the disease. Now, thanks to the global health community efforts and extraordinary support from the Carter Center, only 126 cases were reported in 2014 and only 4 endemic countries remain: Chad, Ethiopia, Mali and South Sudan! If the WHO goal of global eradication of Guinea Worm by 2020 is met then Dracunculiasis is set to become the second human disease in history to be eradicated (the first, and only one, being smallpox). Not bad for an NTD! But there are still challenges!


At the Museum we have a long history of working on health related topics. Indeed our founding father Sir Hans Sloane was a physician who collected and identified plants from all over the world for the purpose of finding health benefits - in fact he developed chocolate milk as a health product.


Today we have a vast and biologically diverse collection of parasites and the insects/crustaceans/snails/arachnids that carry and transmit them. These are used by researchers both in the museum (such as myself and colleagues) but also internationally through collaborative work.


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Collaboration is key - Zanzibar Elimination of Schistosomiasis Transmission (ZEST) programme key players: the Zanzibar Ministry of Health, Public Health Laboratories Pemba, the World Health Organization, SCI, SCORE, Swiss TPH, NHM and others


We are immensely proud of our collections and the work we do in this field especially of the biological information we can contribute to health programmes in endemic countries. One of our most exciting contributions is to the Zanzibar Elimination of Schistosomiasis Transmission (ZEST) programme where we are working in collaboration with the Zanzibar Ministry of Health, various NGOs, the World Health Organization and the local communities to identify and implement the best tools and methods to achieve schistosomiasis elimination in Zanzibar. This would be the first time a sub-Saharan African country would achieve schistosomiasis elimination. Fingers-crossed we are up to the challenge! You can read more about this project in an earlier post on our Super-flies and parasites blog


On Thursday we are bringing out our Parasites and Vectors specimens to showcase them to the public galleries and answer any questions relating to these fascinating yet dangerous organisms. Our wonderful scientists and curators will be on hand to talk to people about our collections and research as will collaborating scientists from the London Centre of Neglected Tropical Disease Research who will talk to you about the diseases and the challenges faced to achieve the WHO 2020 goals. Please do pop by and say hello, come and look at our specimens and help us raise awareness of these devastating diseases and the fight to control and eliminate them.



We are working together with schools, communities, government and research institutes to fight Neglected Tropical Diseases. Schistosomiasis fieldwork photo with the team from the National Institute for Medical Research in Tanzania


Hello Super-flies & Parasites fans!


This time we are departing from the familiar world of blood flukes and having a look at something new and exciting: Welcome to the ‘Forever Flies’series of blog posts. I’ve really enjoyed writing this bit as it’s totally new to me and I’m learning so much from our wonderful scientists in the Forensic Entomology group of the Parasites & Vectors division here at the Museum.


About forensic entomology

I think I mentioned forensic entomology way back in the first ever Super-flies and Parasites post. But to refresh our memories and delve a bit deeper here’s an explanation taken from the group’s website:

'Forensic entomology is the study of insects and other arthropods (ie spiders, mites) in a situation where a crime may have been committed. The insects recovered from a crime scene can provide vital information for the investigating team. The most common role for Museum forensic entomologists is establishing a minimum time since death in suspicious cases, by analysing the carrion insects on the body.'


Flies use the bodies of dead animals to grow and develop, fulfilling a vital nutrient recycling role in an ecosystem. They can turn one vertebrate body into thousands or millions of flies, which are then fed on by other animals - insects, frogs and birds for example. The rate at which they do this, going from eggs to larvae to pupa to adult fly, is pretty consistent.


Knowing enough about the species of flies we can exploit this information when they develop on corpses. By determining how long the insects have been feeding on the tissues of the corpse, we can determine the length of time elapsed since flies found the body; thereby providing crime scene investigators with a minimum post-mortem interval.


Some flies however don’t hang about and wait for death, they prefer feeding on live animal tissues, and can cause a horrible disease called myiasis, a major economic and animal welfare problem.

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Female Bluebottle blow fly, Calliphora vicina, and maggots feeding on a dead pig.


Dr Martin Hall and colleagues within the Museum and around the world work together on the taxonomy and biology of flies that develop as larvae on living or dead vertebrate animals. Their expertise and research greatly contributes to the control of a painful and damaging disease, myiasis, but also to the field of forensic entomology, helping CSIs determine crucial information from a crime scene.


So there you have it, some real life crime scene investigation stuff! These are the guys CSIs turn to for help! (Cue CSI theme song!)


The beauty of maggots lies in their mouthparts


I asked Martin for a little blurb to get the Forever Flies series rolling and he sent me some surprisingly beautiful photos of maggots! Here’s what he has to say about them:

To most people maggots are repulsive creatures; they all look much the same and have zero redeeming features.


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Maggots, thought of as repulsive creatures with zero redeeming features. Read on to see how they are transformed by confocal microscopy into beautiful works of art.

However, viewed under a microscope they become much more interesting, with a range of characters that can be used in discrimination, especially when you look at the business end of the maggot, its mouthparts!


It’s not so easy to ask a tiny 2mm long newly hatched maggot to 'open wide' to view the teeth, and traditionally we have been limited to viewing slide-mounted specimens by light microscopy. Scanning electron microscopy has its merits, but only for the external features. In normal light microscopy, imaging of these mouthpart structures is limited by problems of resolution, illumination and depth of field.

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Greenbottle blowfly, Lucilia sericata light microscope high power image. With normal light microscopy the relationship of the sclerites of the cephaloskeleton (mouthparts) to each other is unclear.


At the Museum we have been using a laser confocal microscope for the first time to look inside these maggots to view the mouthparts, the so-called cephaloskeleton, in three dimensions. The mouthparts are crucial to the maggots in establishing themselves on their food source, be it a live animal or a decomposing corpse. The images produced by the confocal microscope rely on the autofluorescence of structures of the cephaloskeleton.

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Greenbottle blowfly, Lucilia sericata confocal microscope low power image - relationships are still unclear but, with the autofluorescence under laser light, the structures look so much more beautiful!


We were especially interested in the relationships of the small sclerites to each other and the so called 'hump', present in newly hatched larvae of Lucilia greenbottle blowflies but absent in Calliphora bluebottles.

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Greenbottle blowfly, Lucilia sericata confocal microscope high power image: The structure relationships are becoming clearer (the 'hump' is arrowed) and this is finalised in the next image.


The 177 optical sections scanned by the confocal microscope enabled us to rotate and view this structure in three dimensions (see green false-coloured sclerite in image below) and see clearly for the first time how it relates to other structures.


In addition to their academic and practical value in identification, the images are also things of beauty in their own right and would not look out of place in an art gallery!

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Greenbottle blowfly, Lucilia sericata confocal microscope high power image and false colour sclerites. We have rotated the original to give three dimensionality. The red wavelength was selected, as this is the wavelength that gave most autofluorescence of the cephaloskeleton, to enable us to discard other structures and here false-colour has been added to show the different structures, including the 'hump' (in green) or epistomal sclerite.


The work was done at the Museum and involved Drs Andrzej Grzywacz (a visitor under the EC-funded SYNTHESIS project) and Krzysztof Szpila from the Nicolaus Copernicus University in ToruĊ„, Poland, collaborating with Tomasz Góral and Martin Hall. We used the Museum’s Nikon A1-Si Confocal Microscope.


For more information see the article published online in Parasitology Research on 19 September 2014.

By Dr Martin Hall


I hope you enjoyed the first 'Forever Flies' post. For more on flies head over to Erica McAlister's Diptera blog.


There will be more coming soon but just to let you know there may be a couple of weeks break whilst some important maintenance work is done to the site and my life


See you soon


Hello honorary parasitologists,


I know there has been a bit of radio silence on my part and I apologise, summer was calling me and there was a lot of stuff to get through before I could escape on annual leave.


I'm back now and picking up where we left off. Perhaps you are wondering what happened to all those samples we collected in Tanzania in May (see previous posts). Well wonder no longer, I am about to reveal all.


A quick recap of our collecting in Tanzania:

  1. We collected miracidia, the parasite larval stage from infected children, and stored them onto special paper (called Whatman® FTA cards) that stores their genetic material.
  2. We also collected the intermediate host snail from potential transmission sites on the banks of Lake Victoria.
  3. Finally we collected cercariae, the larval stage from infected snails, and stored their genetic material on the Whatman® FTA paper.



Visiting schools to identify infected children, collect the schistosome larval stage (miracidia) and treat the children.


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Snail collecting on the banks of Lake Victoria.


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Collecting cercariae, the Schistosoma larval stage, from infected snails.


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Whatman® FTA cards store the genetic material of schistosome larvae collected from infected children and/or snails.


Storing our collected schistosome larvae on Whatman® FTA cards is ideal for us because:

  1. We avoid storing them in flammable liquids like ethanol.
  2. We avoid having to bring back live, infected snails.


...two things that aiports and customs really don't like!


The Whatman® FTA cards lyse (break) open the parasite cells and lock the genetic material onto the card, keeping it stable and safe at room temperature until we need to use it. So this means we can bring back our samples safely in our suitcases. Hurrah!


The snails, on the other hand, have to be stored in glass tubes with ethanol, so these we have to leave behind in the safe hands of the National Institute for Medical Research, Mwanza. Our collaborators take good care of them until we can arrange a courier service to bring them to the Museum.


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Whatman® FTA cards with collected schistosome genetic material from Tanzania, catalogued and stored safely by SCAN in the Molecular Collections Facility at the Museum.


Once back in the UK I hand over all collected samples and forms to the wonderful SCAN,Schistosomiasis Collection at the Natural History Museum, team. SCAN takes care of the thousands of schistosome samples collected from all over the world and stored at the Museum. This colleciton is very precious and in high demand for lab-based scienists researching the genome of the parasite and host snail in search of new ways to understand and control the disease. 


SCAN cares for collected samples and manages all the associated data, such as:

  • GPS coordinates - so we know where the sample has come from.
  • Collection method - what technique was used to collect the sample?
  • Date of collection - how old is the sample?
  • Storage medium -  is the sample stored on Whatman FTA card or ethanol or any other storage tool?
  • Data on the parasite host - did the sample come from an infected human, cattle, snail? If a snail what species? If a human what age? Gender? 

And lots more.

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The fieldwork forms I fill in when collecting samples in Tanzania. I hand these forms over to the SCAN team along with all my collected samples. They then have the frustrating task of trying to decipher my handwriting.


You have met two members of the SCAN team in my previous posts; Fiona Allan, who acted as our fieldwork photographer whilst helping me in Tanzania and Muriel Rabone, who came to my rescue after Fiona had to head back to the UK. There is just one more person for you to meet; the ever-patient and resourceful Aidan Emery, who manages SCAN


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Fiona and I going through my fieldwork forms and samples - "what have you written here? It's illegible!" Oops!


As you can see there is A LOT of data that goes with each and every schistosome/snail collected and researchers need to have all this information when analyising a parasite or snail sample. SCAN ensures that all this information is properly entered into a database and linked with the samples stored in the Molecular Collection Facility (more on this in a bit).


The SCAN team has even created a wonderful online catalogue of all the collected samples they care for, along with all the data linked to each sample. This greatly assists researchers from all over the world, allowing them to have a look and see what samples are available to them. 



Fiona and Aidan storing the Tanzanian schistosome samples collected onto Whatman® FTA cards. Fiona is showing off the little blue booties we have to wear in the Molecular Collections Facility to avoid bringing in contaminants or anything that could harm the hundreds of thousands of precious samples stored there. 


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The SCAN team takes a photo and measures the size of every snail that arrives from our African collaborators. In order to extract the DNA from the snail for molecular work the shell must be crushed and removed. It is good to have a picture of what the shell looked like before doing so.


The Molecular Collections Facility is a crucial facility in the Museum, as it has all the equipment necessary to keep molecular and genetic samples (such as our schistosome samples) stored safely, stabily and for a long, long time. What equipment am I talking about? I mean: -80 freezers, nitrogen tanks, air-tight cabinets, equipment to release/elute genetic material from stored samples, centrifuges, pipetting robots, you name it. It is run by the very helpful Jackie Mackenzie-Dodds.



Jackie runs the Molecular Collections Facility where all our schistosome samples are stored. All the freezers and nitrogen tanks have alarms linked to them to make sure they continue to function correctly. If one fails an alarm goes off on Jackie's mobile phone so no matter where she is she is immediately notified and able to respond.



Jackie is showing me the liquid nitrogen tanks in the Molecular Collections Facility. Whilst nitrogen in gas form is harmless, liquid nitrogen is very, very cold and any contact with it can cause severe frostbite, even freeze your arm off. Also as it boils it uses up a lot of oxygen in the air, which can lead to asphyxiation. So oxygen monitors are always used. Its incredible freezing ability means it is very effective at storing rare, degraded and old tissue samples.


So there you have it, all our samples are archived carefully until we are able to perform the molecular work we need to do for species identification and to determine how the genetic diversity of the parasites is being affected by treatment control programs. My next couple of blood fluke posts will be about the techniques we use to do this. So read up on Polymerase Chain Reactions (PCR)... it does feature!



Fiona and I have managed to decipher my handwriting! Hurrah! The samples are saved!


Jambo from Mwanza, Tanzania


It's my last week here and as much as I have enjoyed the fieldwork I can't wait to get back home. But there are a few more days of work to do first!


Back to blood-fluke fieldwork


This time I want to tell you about our snail collecting work. Snail in Swahili is called Konokono. The snails we are interested in are aquatic, pulmonate little dudes belonging to the Biomphalaria genus.


They are the intermediate host of Schistosome mansoni, the blood fluke species responsible for intestinal schistosomiasis and it's detrimental health consequences in humans (see previous post - the Blood Fluke story).


We collect these snails in order to study the blood fluke parasites they carry.


The collecting process involves:


  • Scooping for snails on banks of Lake Victoria. We use protective waders to prevent blood fluke infection from the water.
  • Carrying the snails back to the lab, where we use microscopes to identify schistosome parasites.
  • Documenting the infected snails, which will be taken back to the Museum for DNA analysis.



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Aquatic snail of the Biomphalaria genus, host to the human blood fluke Schistosoma mansoni, the causative agent of schistosomiasis.


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Muriel and the team scooping for snails on the banks of Lake Victoria.


Mr Revocatus and Mr James with the snail scoops and protective clothing (hip waders) to prevent blood fluke infection from the water. Credit Fion Allan.

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Village kids from local fishing village. Credit Fiona Allan.

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Mr Revocatus carrying the dredge to our next snail site. Yes this is a beach on Lake Victoria. Not the sea!


Mr James with the dredge getting ready to collect those lake bottom snails. Credit Fiona Allan.

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Dredged up snails from the lake bottom. Now we have to find the small Biomphalaria species we are after. Credit Fiona Allan.


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Sometimes we have to work around the local fauna.


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More local fauna. Credit Fiona Allan.


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Activities by the snail collecting sites. This lady is drying small fish in the sun.



Back in the lab, we sort through all our collected snails, put them in water and check for schistosome parasites.


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Biomphalaria snails in individual wells with water. We check each well for the presence of the parasite larval stage, cercariae.


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Blood fluke larvae (cercariae) under the microscope - those little white things in the water. They're looking for humans to infect!


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Identifying infected snails and giving them an ID number. We then preserve the snail in ethanol and bring them back to the Museum for genetic barcoding (species identification).


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After a hard days work, Muriel and James getting ready to tuck into some food.



Me about to eat some Wali na Samaki (rice and fish).


Jambo from Tanzania,


I realise I'm a bit late with this post so lets get straight to it. Just a warning though, this will be a rather disgusting post so get ready to be grossed out.


You'll remember from my previous post about our school visits that we collect stool samples from infected children. This is because we collect the miracidia larval stage that hatches out of the parasite eggs. And these eggs come out with stool.


The blood fluke life cycle - a recap


Schistosoma. The worm pair releases schistosome eggs into the blood system. The eggs pierce through the wall of the intestinal/urinary tract and exit the host when he/she defecates or urinates. They reach fresh water and hatch out into a larval stage called miracidia.


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Life cycle of Schistosome, blood fluke parasite and the specimens we collect during our fieldwork (circled in yellow).


So in order to collect miracidia we need stool from infected children. Diagnosis of infection is achieved using the Kato Katz method: a specimen of stool viewed on a microscope slide. If schistosome (blood fluke) eggs are observed in the stool specimen then the person is infected with at least one pair of schistosomes. For more information on diagnosis have a look at this video.


Collecting eggs from stool


Once we know which kids are infected we go to the schools and get stool samples (see previous post). We take these back to the lab and then a long process of stool filtering begins. We filter the stool for schistosome eggs, these we place in water and light. This induces them to hatch out into miracidia. We collect the miracidia onto special cards that store their DNA. We transport these back to the UK.


We use a pair of filters called Pitchford funnels (devised by Pitchford & Visser). The inner smaller funnel has bigger pores that allow the schistosome eggs to pass through but stops larger pieces of stool. The outer funnel is made of a finer mesh with pores that stop schistosome eggs from going through, this allows us to pour lots of water through the funnel thereby washing the eggs of stool material that may stop them from hatching.



Pitchford Funnels (devised by Pitchford & Visser). Credit Fiona Allan.



Stool Samples. Credit Fiona Allan.



Sieve to break up stool. Credit Fiona Allan.



Using the sieve to break up the stool sample.



Pouring stooly water through Pitchford Funnel. Credit Fiona Allan.


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Myself and Mr John processing stool samples. Credit Fiona Allan.



Adding formalin to left over stool samples to kill of anything inside. These are disposed of safely later. Credit Fiona Allan.



>Revocatus adding formalin to stool. Credt Fiona Allan.



My Nagai releasing the eggs and some water into a petri dish.



Petri dishes of eggs and water. Waiting to hatch.



Fiona starts checking for miracidia swimming in the petri dish.


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Fiona and James in the lab in National Institute for Medical Research in Mwanza.


Sometimes out in rural areas where we use local hospitals to process our samples things can go wrong, such as a power cut. No electricity means no light through the microscope. Thankfully we rise to the challenge and strap our head torches round our microscopes as an alternate source of light. Not quite as clear but it still works.



Even a power cut will not stop us, we use our head torches as a light source and continue working.


So that's it for now. Tune in for the next post - snail collecting on the banks of Lake Victoria.


Jambo (hi) from Tanzania!


We are now into our second week of the trip and the blood fluke parasite collection is going well. A few logistical hiccups but nothing we can’t handle (so far).


Last week we went to a few schools to collect schistosomes from infected children. Just to recap why and what we are collecting from schools, here is the life cycle with the stages we are collecting on this trip:


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The life cycle of blood flukes, Schistosoma, involving a vertebrate (e.g. human) host and an aquatic snail host. Transmission is through contact of infested freshwater. The yellow circles are the stages and specimens we collect when doing fieldwork.


So we have the delightful job of collecting the larval stage, called miracidia, that hatch out from eggs. How do we do this? We go into a school, collect stool samples from infected children and filter out the eggs. We then put them in some water in sunlight and wait for them to hatch. I will explain this in more detail in a subsequent post on lab work. For now let's stick to the first stage: visiting schools.


We visit state primary schools in the Mwanza region of Lake Victoria. To get to these schools we sometimes have to drive for hours through dirt tracks. All sorts of obstacles occur but the most common one is this: cattle!



On our way to a school, a herd of cattle, goats and sheep block our path.


When we arrive we visit the head teacher and get a proper greeting from the school. The teacher then calls out our selected students - the ones we know are infected from a previous survey, more on this later.



Children were practicing singing, dancing and music on the day we arrived. Credit: Fiona Allan.



Up close and personal, the kids stare at us. Eventually we do get them to smile. Credit: Fiona Allan.


We’re a small team: two scientists from the Museum (Fiona and myself) and 3 research technicians from the National Institute for Medical Research in Mwanza - Mr John, Mr Nagai and Mr James. As well as our trusted driver – Mr Lenard.



The team, Mr John, Mr Nagai and me. Getting our gloves on and our kit ready. Credit: Fiona Allan.



My colleague Fiona Allan, a brilliant schistosome expert and our trip’s photographer.



Me holding a football I am about to present to the headteacher as a present. Credit: Fiona Allan.


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Mr James is teaching the children how to give us a stool samples and most importantly to wash their hands afterwards! Good hygiene practice!


We give the kids a container to put a stool sample, and some toilet paper. They run off to the latrines and come back with a full container. How they are able to poop on demand always amazes me. We label the containers with unique identification numbers for each child. And then go back in the lab to process the samples. All the children in the school receive treatment a couple of weeks later. We always treat any infected child!


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Mr Nagai and Mr John handing out toilet paper to the kids. Credit: Fiona Allan.


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The children all grab for a container for their stool sample.



School latrines. Credit: Fiona Allan.


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Mr James supervises the hand washing.


We were very happy to see this in some of the schools: a warning about schistosomiasis, called Kichocho in Kiswahili, and an explanation about the life cycle. Credit: Fiona Allan.


Some shots from the school. A little girl with a necklace of bottle tops, this actually serves as a abacus in the schools. Credit: Fiona Allan.



Local abacus, device for learning arithmetic. Credit: Fiona Allan.



Kids playing in front of a typical Mwanza rock.


This time I came with some gifts for the schools. Back in the UK I decided to get a football for each school. The footballs they use are often just rags and plastic wrapped into a tight ball and tied together, or completely deflated punctured balls. So I went shopping at Altimus. The staff and manager were curious about why I wanted 16 footballs. When I explained they very kindly gave me a generous discount. So this is a thank you to Altimus!



Kids playing football with their old cloth ball.



The new football next to the old football. You can see why the teachers and kids are delighted with the gift. Thank you Altimus.


Girls playing basketball with the new ball from Altimus.

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Time to say Asante (thank you) and Kwaheri (good bye).


That's it for today. Next post - what do we do with poo and how to go parasite fishing with a microscope.


Asante sana (thank you very much in Swahili).


The blood fluke story

Posted by Anouk Gouvras May 1, 2014

Hello super-fly and parasite enthusiasts. Time for blog post 2, which is coming to you from the Mwanza region of Tanzania, bordering the banks of Lake Victoria. My colleague and I are here to collect specimens of the blood fluke Schistosoma from infected humans and snails.


Infection with the blood fluke Schistosoma causes a disease called Schistosomiasis (aka Bilharzia). Over 200 million people worldwide are infected with over 700 million people living at risk of infection. Over 80% of infected people live in sub-Saharan Africa. It is a disease of low socio-economic status, affecting the poorest communities and most neglected, vulnerable people. Infants and children are especially prone to infection due to their less developed immune system.


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Children in a school in Niger, West Africa, queuing to be tested for schistosomiasis. The little boy at the front is showing the swollen liver and spleen symptom. A result of being infected with schistosomiasis.


There are two forms of the disease, depending on the species of the infecting schistosome worm:


Intestinal Schistosomiasis

  • diarrhoea, bloody stool
  • anaemia, stunted growth
  • enlarged liver and spleen
  • severe damage to the liver leading to liver fibrosis


Urogenital schistosomiasis

  • blood in urine, painful urination
  • anaemia, stunted growth
  • damage to the genitals, kidneys and bladder
  • bladder cancer
  • increased risk of sexually transmitted diseases like HIV


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Urine samples from children infected with Schistosoma haematobium, the urogenital form of schistosomiasis. The red colour indicates blood seeping out with the urine due to the damage done by the schistosome eggs.


To help fight schistosomiasis we need to understand the complex life cycle of Schistosoma, which involves a vertebrate (in this case human) host, a snail host and transmission via water contact.


The blood fluke life cycle


Lets start with a worm pair living inside a little boy in sub-Saharan Africa. The worm pair resides in the blood system of the little boy, either around the intestinal tract or around the urinary tract depending on the species of Schistosoma.


The worm pair releases schistosome eggs into the blood system. The eggs pierce through the wall of the intestinal/urinary tract and exit the boy when he defecates or urinates. They reach fresh water and hatch out into a larval stage called miracidia. These infect a specific aquatic snail species and reproduce asexually, creating thousands of clonal larval stages called cercaraie.


Cercaraie leave the snail to locate and infect a human by piercing through exposed skin in the water. They travel to the liver via the blood system and there they mature into adult worms, ready to reproduce and continue the life cycle (see diagram below).


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The life cycle of blood flukes, Schistosoma, involving a vertebrate (e.g. human) host and an aquatic snail host. Transmission is through contact with infested freshwater. The yellow circles are the stages and specimens we collect when doing fieldwork. Credit: Aidan Emery.


Schistosoma blood fluke worm pair700p.jpgA schistosome worm pair. The fat male carries the thinner female worm folded in a little groove where he feeds and shelters her whilst she produces eggs. The worm pair lives inside the veins of animals.


The schistosome species I work on (Schistosoma mansoni) causes intestinal schistosomiasis. It lives in the vein blood system of the liver and intestinal tract of humans. The adult worms themselves don’t cause much harm but it is the eggs they produce that cause the disease, by:


  • Piercing the barrier between the blood system and the intestinal wall = bloody diarrhoea and painful cramps.
  • The eggs that don’t make it out get trapped in organ tissues, causing the immune system to overreact and damage the surrounding human tissues.
  • More worm pairs = more eggs = more damage to the organs and the host. This is what causes the chronic and more severe aspects of the disease such as kidney failure, bladder cancer and liver fibrosis in adulthood.


Thankfully there is an effective oral drug called Praziquantel that kills the adult worms. However it cannot prevent children from becoming infected. So in areas where there is no clean piped water or a sewage system, the local water bodies such as Lake Victoria are the only sources of water for the local population. People have no choice but to fish, wash, bathe and collect water from these schistosome-infested waters and therefore are reinfected quickly.


Treatment needs to be repeated regularly to avoid heavy worm numbers and high egg outputs. Regular treatment means controlling the disease but does not mean eliminating it. For this we need more research to develop better tools to fight the disease. There is also a major the worry that the parasite will become resistant to the drug. If the parasite develops resistance and the drug stops working there is currently no alternative treatment.


West Africa schistosome transmission site and local water collection point.jpg

Clean water is not available so local water-bodies are used, such as this irrigation canal in Niger, West Africa.

We are researching the impact of human treatments on the parasite population. This will reveal how the parasite is responding to ongoing treatment programmes, if the drug is working effectively and if there are any warning signs regarding drug resistance.


That’s it for now. Coming up, a visit to the schools to collect stool samples from infected children. Disgusting work but someone’s got to do it.