Microbes (bacteria, viruses and parasites)

Public summary: 

Learn about the fascinating world of microbes with our fun cuddly toy bacteria, viruses and parasites, plus awesome slides and pictures.

Three boxes of kit to explain microbiology
Useful information
Kit List: 

Three small grey boxes, one for each of bacteria, viruses and parasites. Details of what is in each box are given in the explanation below.

Packing Away: 

Please make sure that we have all the cuddly microbes, and that they go back in the right box.

Frequency of use: 


We’ve put together three boxes to talk about microbes. This can be combined into one big experiment, or split into three separate ones. Please try to keep each type of microbe in its rightful box.

Bacteria box

In the box:
• 9 x cuddly bacteria
• 1 x cuddly penicillin bug (to talk about antibiotics)
• 1 x cuddly yeast (to say that not all microbes are bacteria)
• 1 x plate of plastic bacteria (E.coli)
• 2 x bacteria viewers (look a bit like small microscopes)
• 3 x slides sets for bacteria viewers
• 1 x flask for growing bacteria
• Packets of tools for growing bacteria
• Laminated fact sheets for cuddly bacteria
• Laminated instructions sheets for hand washing activity
• UV hand wash cream (this is £15 per bottle, so use only minimum amount per group)
• UV light for hand wash activity

If you want to do the hand wash activity you'll need a soap, warm water and bowl and some paper towels to dry hands on.

There are several things to do: lots of cuddly bacteria to talk about (everyone loves these), UV hand-washing experiment (good for younger kids) and bacteria viewers and lab props (better for older kids).

Stories you could tell:
- How some bacteria are really good for us and others are bad (with the cuddly bacteria)
- How you can pass on bacteria (good and bad) on your skin- see hand wash activity notes (good for younger kids)
- How to grow bacteria in the lab (with lab props and slide viewers)

Element One: Cuddly Microbes
The following explanations are also found on laminated sheets in the box, and there is some additional information on labels attached to the cuddly bacteria:

1) E. coli (Escherichia coli): Gram negative, rod shaped
*SLIDE in microscope box*
Found in the intestines of most mammals- it’s there inside you only hours after you’re born! There are lots of bacteria in our digestive system that are harmless to us – in fact they stop harmful bacteria from living and growing there instead. Sometimes E.coli can make us ill; some unusual strains produce toxins which can give us food poisoning. Biologists like E. coli: It’s very easy to grow in the lab and can make lots of proteins and DNA very quickly.

2 ) Salmonella (Salmonella enterica): Gram negative, rod shaped
*SLIDE in microscope box*
Can infect humans and animals, so sometimes infects people of food isn’t cooked properly (particularly chicken or eggs). Causes gastroenteritis (diarrhoea and vomiting…) The bacterium itself can actually live inside certain types of white blood cell, which is a very effective way of hiding from the cells of the immune system that circulate in the blood.

3 ) Typhoid Fever (Salmonella typhimurium): Gram negative, rod shaped
Very closely related to the Salmonella bacteria that cause food poisoning. Typhoid fever is a lot worse than food poisoning however: its symptoms include a high fever, abdominal pain, a skin rash and headaches. Some people can be infected without having symptoms, but can still pass it to other people making them carriers of the disease. 'Typhoid Mary' (Mary Mallon) was the first recognised asymptomatic carrier and spread typhoid around New York in the early 1900s in her work as a cook, over 50 have fatalities have been linked to her. It is spread by drinking water or eating food contaminated with the bacterium. Typhoid fever is most common in India and its spread can be prevented by good hygiene.

4 ) Diarrhoea (Campylobacter jejuni): Gram negative, spiral shaped
Most common cause of food poisoning in the UK, linked to handling raw chicken. It produces a toxin that kills certain human cells, which helps the bacteria to survive, without being attacked by the immune system.

5 ) TB (Mycobacterium tuberculosis): ‘Acid fast’ will not gram stain
Infects the lungs when the bacterium is breathed in. Here it gets contained by the immune system in a tough shell. Only about 1 in 10 people who have the bacterium get ill: this usually happens when the immune system is weak and cannot contain the bacterium. The disease can cause damage to the lungs and in really bad cases it can spread to other parts of the body.

6 ) Cholera (Vibrio cholerae): Gram negative, comma shaped
Usually spread when water is contaminated by the bacterium. Produces a toxin that stops you absorbing water through your intestines. This causes really bad diarrhoea, which can be fatal as you lose too much water and salt from your body.

7 ) Listeria (Listeria monocytogenes): Gram positive, rod shaped
Causes fever and muscle pains. If the bacterium can get to the brain this can cause meningitis. Pregnant women are the most commonly infected – the mother usually gets a mild fever but the baby might be badly affected or born early. The source of the infection is often food – pasteurising dairy foods helps kill the bacteria and reduce the numbers of infections.

8 ) Stomach Ache (Shigella): Gram negative, rod shaped
Very closely related to E. coli. When the bacterium is ingested it can get inside the cells of your intestine. It produces some toxins that can also make you ill.

9 ) Yogurt (Lactobacillus bulgaricus): Gram positive, rod shaped
One of a number of species of bacteria that can be used to make yoghurt.
What Wikipedia has to say about the use of L. bulgaricus in the manufacture of yoghurt:
“Lactobacillus delbrueckii subsp. bulgaricus is commonly used alongside Streptococcus thermophilus as a starter for making yoghurt. The two species work in synergy, with L. bulgaricus producing amino acids from milk proteins, which are then used by S. thermophilus. Both species produce lactic acid, which gives yoghurt its tart flavour and acts as a preservative. The resulting decrease in pH also partially coagulates the milk proteins, such as casein, resulting in yoghurt's thickness. While fermenting milk, L. bulgaricus produces acetaldehyde, one of the main yoghurt aroma components. Some strains of bulgaricus also produce bacteriocins which kill undesired bacteria. It is often helpful to sufferers of lactose intolerance, whose digestive systems lack the enzymes to break down lactose to simpler sugars.”

10) gonorea, syphilis, chalmydia

(Yes, we know that they're not bacteria, but we'd found that people ask about antibiotics, so we think that they're a nice bonus to have in the box)

Penicillin (Penicillium chrysogenum)
This is a fungus that makes penicillin, an antibiotic that kills some types of bacteria. It does this to kill off the bacteria that are competing for the food it needs for growth, but we have used penicillin from this fungus to treat bacterial infections in humans.

Yeast for bread and beer
Also a kind of fungus. It's one cell, just like the bacteria, though the cell is much bigger. In bread the yeast can use the sugars in the dough for its growth; it breaks them down in a reaction that produces the gas carbon dioxide, which make the bread rise. In beer the yeast converts the sugars to alcohols.

Element Two: Growing Bacteria in the Lab
The kit:
• 1 x plate of plastic bacteria (E. coli)
• 1 x flask for growing bacteria
• Packets of tools for growing bacteria

NB. The kit we have has not been used in a lab and the 'bacteria' on the plate are not real!

Under sterile (no other bacteria) conditions:
1) You can grow some types of bacteria in the lab. E. coli is happy to grow on agar plates, as long as it has all the nutrients it might need. The L-shaped spreader is used when you put the cells on the new plate, to make sure that the bacteria aren't too close together.
2) If you want more cells than this, get some bugs you're interested in with the green tool.
3) The plastic flask can be used to grow bacteria in a growth medium/ broth. (Extra detail: For E. coli you'd usually use Luria-Bertani medium (LB) at 37 degrees C to provide the necessary nutrients. This contains 10g Tryptone (enzymatically digested milk protein casein - supplies amino acids), 5g of Yeast Extract (supplies lots of nutrients), 1g glucose, 10g NaCl pH ~7.2, deionized, distilled water to 1 litre.)

Element three: bacteria viewers
The kit:
• 2 x bacteria viewers (look a bit like small microscopes)
• 3 x slides sets for bacteria viewers

These are essentially a more durable version of a set of slides and a microscope. In the set of slides (which come with a booklet for information) you can see various different shapes of bacteria - just like in the cuddly bugs:
1) Round (1= "coccus", 2+ = "cocci")
2) Rod (1= "baccilus", 2+ = "baccili")
3) Spiral

These shapes are determined by the cell wall (the tough outer layer) and the cytoskeleton (internal "scaffolding"). They matter because they affect how the cells can absorb nutrients from its environment, how they can attach to surfaces and how they're able to move.

Element four: Handwashing Activity

Why should we bother washing our hands? This activity uses glow in the dark stuff to show how easy it is to miss the bits of your hands where bacteria are...

The kit:
• Laminated instructions sheets for hand washing activity
• UV hand wash cream (this is £15 per bottle, so use only minimum amount per group)
• UV light for hand wash activity
*Also needs a bowl and paper towels that are not supplied in the box*

There is a set of laminated instructor notes in the box, taken from the Wellcome Trust. A full version can be viewed online here: http://www.yourgenome.org/downloads/pdf/teachers/handshake/handshake_tno...

• No hand washing: Form a ‘line’ around your group of children. Squirt UV cream on the first child’s hand and get them to rub their hands together, then shake the hand of the next person in the group, then they shake the next person’s hand... Shine the UV torch onto each of the kids’ hands to show up the ‘bacteria’. All should now wash their hands thoroughly.
• Compare the results with hand washing: Repeat the procedure but get each person to wash their hands in the bowl after the UV cream has been rubbed in but before they shake the hand of the next person.
• If the group activity isn’t suitable, you could always compare before and after hand washing on the same child.
• This should show that washing hands helps to remove microbes – and washing with soap does this better than with just water as the soap breaks down some of the natural oils on your hands that help the bacteria to stick. Look at where the bacteria were found – it’s easier for bacteria to stay between our fingers and under our nails – and that’s why it’s important to wash your hands properly!

Viruses box

In this box:
• 12 x cuddly viruses
• 1 x plastic model HIV virus (in box)
• microbiology text book

VIRUSES: Can be as simple as DNA or RNA in a protein coat. They use the cells of
their host to make lots of new viruses. Often these new viruses get released by
causing the cell to burst. Viruses can’t survive for very long outside of cells so new
viruses quickly find a new cell to infect.

HIV (Human Immunodeficiency Virus): Retrovirus (RNA genome copies itself into DNA, using viral reverse transcriptase. The DNA integrates into the host chromosome and new viral genomes are produced by host transcription/translation machinery)
Can be spread via some bodily fluids and blood. Lives in white blood cells (CD4+ helper T cells) and eventually kills them, which means the immune system cannot function properly. People where HIV has killed too many white blood cells have AIDS (acquired immune deficiency syndrome), and this means that they can become very ill or even die from diseases that would not harm a healthy person (opportunistic infections – a big killer is tuberculosis caused by Mycobacterium tuberculosis – cuddly bug in the bacteria box).

Common Cold (Rhinovirus): positive sense RNA
Spreads easily from infected people when they sneeze or contaminate surfaces. The virus is very happy at the temperature and conditions in the human nose which is where they initially infect. There are lots of different types of rhinovirus whose protein coats all look different to the immune system, which is why we don’t get become immune to the common cold.

Measles (Morbillivirus): negative sense RNA virus
Usually spread by breathing in virus from droplets in the atmosphere. Causes a fever, rash and red eyes. Most people will have been vaccinated against this with the MMR jab, which mostly eradicated measles from the UK. However since the scare about the MMR jab (spuriously linked to autism), the disease has been cropping up in affluent areas of London! (Vaccine scares can destroy herd immunity, the protection the population has when enough people are vaccinated and the virus cannot find enough hosts to spread to.)

Kissing Disease (Epstein-Barr Virus): DNA virus
Most of you will have this virus right now. It is usually spread via saliva, causing a mild fever in the majority of the population in early childhood. (Lots of people have asked me why this is and the answer is we don’t really know – scientists think it might be something to do with how the immune response develops over childhood.) However some people who don’t get the virus in early life might get it when they come into contact with other people’s saliva in their teenage years - they then get Glandular Fever. An interesting thing about the virus is that you never really get rid of it; some of its DNA forms little circles in the nucleus of the white blood cells it infects, and it can remain dormant (latent infection) for a long time (occasionally getting out into saliva but not making you ill). The virus that causes chicken pox can do this in nerve cells.

Influenza: Negative sense RNA virus
Infects almost all mammals (eg. swine flu, bird flu), aquatic birds are primary host. Common problem in humans - see most in winter when low air humidity allows the visus to spread more effectively. Spread by breathing in virus particles (Respiratory tract). Causes symptoms including fever, headache, cough, muscle aches and less commonly vomiting and diarrhoea. It can be vaccinated against, however it is able to change its structure (by mutating its genome which is a random process) so it can evade the immune system. This means flu vaccines keep having to be updated to protect people against the new variations of the virus. This, and the fact that influenza virus also infects birds, is the reason why it would not be possible to eradicate influenza. Could compare this to viruses like smallpox and polio which have or have nearly been eradicated because they have more stable genomes and no animal reservoir.

Rabies: Negative sense RNA virus
Enters via skin and exits via saliva - spread through being bitten by an infected animal (usually dog). Results in death by killing brain cells in the cerebellum. The virus travels to the brain from the bite site up the nerves and it progresses slowly, so it is possible to stop the progression of the disease by vaccinating after being bitten.

Ebola: Negative sense RNA virus
Spreads by direct contact. This virus has a high fatality rate of up to 90% (but closer to 40% in the most recent outbreak). It causes symptoms including fever, muscle aches, skin rash, vomiting + diarrhoea, weakness, bleeding from nose, mouth etc. The virus can infect many cell types and it spreads within the body through the circulatory system. It causes such severe disease because it causes clotting within the blood vessels, bleeding inside the body (haemorrhage) leading to a drop in blood pressure and multi-organ failure. It is also so severe because it originated in a different animal to humans - the fruit bat - and transmitted to humans relatively recently. This is in contrast to viruses such as the common cold which have been in human populations for a long period of our evolution meaning we have adapted to survive it.

Winter Vomiting Disease (Norovirus): Positive sense RNA virus
Very common in the UK and very contagious. Causes vomiting and diarrhoea. Spread can be prevented by washing hands regularly.

Polio: Positive sense RNA virus
See "Polio, vaccination and disease eradication" experiment

Chicken Pox: Double stranded DNA virus
Otherwise known as Varicella-Zoster virus, a member of the herpesvirus family. Highly contagious; Spread through direct contact, coughing and sneezing, and causes red spots on the skin all over the body. Causes mild symptoms if caught when young, but causes Shingles in adults which is more serious. After initial infection, the virus goes dormant (latent) in the nervous system, and later in life it might reactivate to cause shingles.

T4 (T4-Bacteriophage):
Bacteriophage are viruses but they do not infect humans – they infect bacteria. One day this might be useful to us for treating bacterial infections (‘phage therapy’) where you can infect specific bacterial cells with genes that kill them/stop them reproducing.

HPV, here's, cancer (not virus)

Parasites Box

• 6 x cuddly parasites (4x protozoa, 2x insects)
• 2 x cuddly mosquitos (parasite "vectors")
• laminated fact sheets
• laminated parasite matching game
• microbiology text book

What is a parasite?

- Being a parasite is essentially free-loading off the host that it feeds on.
- Some parasites live on the surface of their hosts, these are ectoparasites (e.g. some mites/lice, ticks).
- Some types parasites live inside their "prey", these are endoparasites. Some of these live in gaps between the host tissues (eg trypansomes, tapeworms) while others live inside the host cells (eg malaria parasites)
- Most parasites live in more than one species at some point in their lifecycle (see individual descriptions).
- The parasites that you're most likely to hear about are single-celled Protozoa (including the parasites that cause malaria and trypanosomiasis), and parasitic worms (such as tapeworms).
- There is constant conflict between parasite and host: the host’s immune system is trying to kill the parasite, and the parasite is trying to hide from the immune system. Co-evolution of the parasite with the host has led to them becoming well adapted to each other – a good parasite is one that manipulates the host so it can reproduce maximally but doesn’t kill the host because it needs somewhere to live!
- Parasitic diseases are a massive problem for global health. Malaria kills nearly 1 million people per year, most African children under 5 years old. Parasitic worms might reduce your quality of life so much that you can’t care for your family, leading to a wider impact (eg elephantiasis). In many regions where parasitic diseases are a problem there is very basic healthcare, making treatment more difficult to access.
- Also a big problem in animals - cost to pet owners of preventative treatment (to avoid illness), most farm animals have a significant parasite burden (gives economic costs of reduced production, greater food intake required, medications etc.

Some examples of parasites

PROTOZOA: Single-celled eukaryotes

1) Malaria (Plasmodium falciparum):
4 parasites cause malaria: Plasmodium falciparum (the most common and most deadly), Plasmodium vivax, Plasmodium malariae, Plasmodium ovale. These are carried by Anopheles mosquitoes, the vector, which are active and hence bite people at night. When they bite an infected person they take up the parasite into their digestive system (parasite stage = sporozoite), and then secrete it into the next person they bite in saliva (used to inject anticoagulants to keep the person bleeding so the mosquito can get its blood meal). The parasite then travels in the bloodstream to the liver where cells are infected (parasite stage = merozoite). Parasites are released and enter red blood cells in the circulation, where they multiply and burst the red blood cell, causing the symptoms of malaria. Inside some red blood cells the parasites become gametocytes which are taken up by another mosquito if it bites the person.
Symptoms at first include fever, chills, headache and vomiting. In some cases this can rapidly progress to severe anaemia, respiratory distress or cerebral malaria - and can be fatal. However if you live in a malarial area (and get infected often) you may develop partial resistance to malaria and be infected without symptoms (asymptomatic infection). When you travel to a malarial area (Asia, South America, Africa - but the range is spreading) you use chemoprophylaxis (drugs to stop an infection becoming established), in combination with avoiding being bitten (mosquito nets, DEET mosquito repellent) - and there are also drugs available to treat malarial infections.

2) African Sleeping Sickness (Trypanosoma brucei):
Parasites are injected into you by the bite of a tsetse fly in Africa (tsetse fly = the vector), or they can cross the placenta to infect a fetus. Trypanosomes don’t live inside cells like malaria but they live in the blood stream – this means they have to do clever things to hide from the immune system, such as constantly changing their protein coat so that the immune system can't recognise them as a parasite. 2 different trypanosome subspecies cause sleeping sickness: T. brucei rhodesiense gives a rapidly-progressing disease (death in weeks to months) whereas causes a slowly-progressing disease (you might not have any symptoms for years!). Sleeping sickness occurs when the trypanosomes enter the brain and start to destroy the areas that control sleep and wakefulness, leading to blurred sleep/wake transitions and falling asleep at inappropriate times, progressing to coma and death! Trypanosomiasis (disease caused by trypanosomes) is treatable - but it's much easier at the early stage (drugs: pentamidine/suramine) than once the parasites enter the brain (drugs: melarsoprol - which comes from arsenic and has nasty side effects that can be fatal themselves!).
African trypanosomes also infect cattle, making agriculture in areas with tsetse flies really unproductive - cattle become really thin and so can't work (pulling ploughs etc) and aren't useful as food for people either!

3) Chagas disease/ American trypanosomiasis (Trypanosoma cruzi)
Chagas disease, also known as American trypanosomiasis, is caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). 10 million people in the world are infected, mainly in South America. The vector transmitting the trypanosomes to humans is the triatomine bug ('kissing bugs'). These live on the walls of houses and are nocturnal, biting people on their exposed faces when they are asleep at night. Unlike the African trypanosomes, South American trypanosomes aren't injected with the bug's saliva but the bug defecates next to the bite and it's the faeces that contain the parasites. They get into the person's bloodstream when they rub their face and smear the faeces into the bite!
The first sign of infection is often a large swelling of the eyelid on the side of the face that was bitten. Parasites can then enter the heart (30% cases) causing problems with the heartbeat, and maybe sudden death. Digestive problems can also occur (10% cases) when there is enlargement of the oesophagus as food can't enter the stomach - the food that gets trapped can start rotting which is pretty disgusting! Chagas disease is highly treatable though, with nearly 100% of people cured if treated early (benznidazole or nifurtimox).

4) Toxoplasmosis (Toxoplasma gondii)
Toxoplasma gondii is a species of parasitic protozoa.The definitive host (where the sexual stage of the life cycle occurs) is the cat - gametes are formed in the digestive tract and exit in the faeces. Then they enter another host (intermediate host) when they eat or drink contaminated food or water. So far every warm-blooded animal tested can act as a host - including humans. Here the parasite can enter any nucleated cell and replicates to form a tissue cyst. This can be passed on to another intermediate host or a cat by carnivory.
Usually toxoplasmosis has very mild symptoms (there might be some fever) and in France up to 90% of adults are infected (due to the French love of rare meat)! However serious disease can be caused in immunocompromised people (AIDS sufferers or post-transplant patients on immunosuppressive drugs) and pregnant women (increasing the risk of spontaneous abortion and birth defects). This is why pregnant women are advised not to touch cat litter! (also explains why pregnant women are advised to clean fruit/veg thoroughly as gametes can contaminate them, and women become infected this way)
T.gondii infection of the brain can lead to changes in behaviour by changing the amounts of chemicals in the brain (dopamine). Rats and mice lose their fear response to the scent of cats (tested using cat urine) and are more curious - very important effect, as means rats are more likely to be caught and eaten by cats giving greater rate of infection of cats (completing the parasites life cycle). Studies in humans have linked toxoplasmosis to schizophrenia (including hallucinations and reckless behaviour), slower reaction times and greater chance of causing traffic accidents.


(There's some slides for these in "Microscopes & Cells" which can be borrowed - same for some preserved specimens in "Horrible Housemates".)

Flukes (Trematodes): Adult flukes are leaf-shaped flatworms. Prominent suckers at the mouth and on the stomach help maintain position. Flukes are hermaphroditic (both male and female) except for blood flukes (schistosomes), which are bisexual. The life-cycle includes a snail intermediate host.

Tapeworms (Cestodes): Adult tapeworms are elongated, segmented, hermaphroditic flatworms that inhabit the intestinal lumen. You can eat the cysts in undercooked animal tissues (pork is probably the greatest risk if undercooked), and then they develop in your intestines. They eat your food from your intestine – instead of you getting the nutrients. They attach to the intestinal wall using suckers in the head. Problematic in the developing world where there is already malnutrition. People used to use tapeworms as a slimming aid… They can grow up to 15 metres long and live for 20 years! Larval forms live in extraintestinal tissues.

Roundworms (Nematodes): Adult and larval roundworms are bisexual, cylindrical worms. They inhabit intestinal and extraintestinal sites.

1) Schistosomiasis (caused by a fluke/ trematode)
• Schistosomiasis is a chronic, parasitic disease caused by blood flukes (schistosomes)
• At least 230 million people require treatment every year – praziquantel
• Infection from larval forms released from freshwater snails in contaminated water
• Penetrate the skin and live in circulation where females release eggs
• Cause damage because of the host immune response to the parasites

2) Liver fluke (Fasciola hepatica) (caused by a fluke)
• Freshwater snail intermediate host, where reproduction occurs, then they are released as cercariae and swim through water to be ingested by ruminants normally, or sometimes humans eating uncooked foods like watercress
• Adult lives in the liver where they feed on the lining of bile ducts – makes cheese-like holes in the liver
• Produce eggs – up to 25000 a day per female

3) Dracunculiasis (guinea-worm disease, caused by a nematode)
• Dracunculiasis (caused by Dracunculus medinensis, a long thread-like worm) is a parasitic disease on the verge of eradication
• Exclusively transmitted by drinking water contaminated with parasite-infected fleas such as rural isolated ponds
• Takes 10-14 months for worm to mature in the body

4) Hookworm (Ancylostoma duodenale and Necator americanus, kinds of nematodes)
• Soil-transmitted helminths (parasitic worms)
• Major burden of disease worldwide - estimated 576-740 million people infected with hookworm
• Hookworms live in the small intestine, eggs are passed in faeces of infected person – this is a problem in the developing world where people may defecate outside (near bushes, in a garden, or field) of if the faeces of an infected person are used as fertilizer, eggs are deposited on soil.
• Eggs then mature and hatch, releasing larvae (immature worms).
• The larvae mature into a form that can penetrate the skin of humans, and infection is mainly acquired by walking barefoot on contaminated
• Most people infected with hookworms have no symptoms. Some have gastrointestinal symptoms, especially persons who are infected for the first time. The most serious effects of hookworm infection are blood loss leading to anemia, in addition to protein loss.
• Infection is treatable – anthelminthic medications eg. albenadazole


(There are two cuddly toys for this, so you can show a second uninfected mosquito feeding off a human host)

Mosquito (Culex pipiens):
• Most mosquitoes are harmless but some can transmit disease
• Viral diseases, such as yellow fever, dengue fever and Chikungunya, transmitted mostly by Aedes aegypti
• Parasitic disease malaria, carried by mosquitoes of the genus Anopheles
• Lymphatic filariasis (the main cause of elephantiasis – worms block lymphatics impairing lymph drainage causing swelling of the limbs)
• We have cuddly toys of mosquitoes – in the parasites box


(There's some cuddly toys and slides for these, and hopefully some preserved samples borrowed from the "Horrible Housemates" experiment)
1) Head louse (Pediculus humanus capitis)
• Lice are wingless biting or sucking insects. Lice infestation of any part of the body is called pediculosis!
• Live on your head (an ectoparasite) - has a single strong claw on each leg that can grab onto 6 hairs so they can move rapidly (may be on several heads in one day). But their short stumpy legs mean they can’t jump or walk well on flat surfaces.
• Your head provides a source of food - blood
• Eggs are called nits and the female attaches the eggs close to the scalp with a transparent quick-setting glue
• The time taken to hatch depends upon temperature
• Head lice have no lungs! They take in air by muscle contraction of the abdomen (via spiracles)
• Head lice have been recovered from prehistoric mummies!

2) Bed bug (Cimex lectularius)
• Ectoparasites that feed on human blood (haematophagous)
• Live in houses and especially beds – most active at night so they can feed on the host without being noticed
• Adults can survive more than a year without feeding
• They don’t usually spread disease but they can cause allergic skin reactions
• Light brown flattened oval-shaped body, vestigial front wings, microscopic hairs on abdomen that give a banded appearance

Risk Assessment
Date risk assesment last checked: 
Sun, 20/01/2019
Risk assesment checked by: 
Matt Worssam
Date risk assesment double checked: 
Wed, 23/01/2019
Risk assesment double-checked by: 
Risk Assessment: 
Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Microbe toys and accessories Trip hazard if dropped on the floor. 3 2 6 Keep all props in contained area and pick up any fallen toys as soon as is safe. Call first aider in case of injury. 2 2 4
UV cream UV cream in eyes. 2 3 6 When giving UV cream to children, tell them not to put their fingers near their eyes and ensure they rinse it off.
Call first aider in case of injury. If washing up liquid gets into an eye, demonstrator must call a first aider and may perform an eye wash if trained and confident to do so.
1 3 3
UV cream Slip hazard if spilled. 1 2 2 All spills should be cleared up immediately. Call first aider in case of injury. 1 1 1
UV cream Possible allergic reaction to cream? (Widely used in teaching, so severe reaction is likely to be rare). 1 3 3 Suggest that volunteer from group isn't one who is known to have sensitive skin.
Call first aider in case of allergic reaction, then seek further medical advice where appropriate.
1 3 3
Sensitive Topics We have a cancer cell and some things here which can cause cancer which effects lots of people, there are also several other potentially fatal diseases. 4 2 8 Deal with topic respectfully, move on if it seems distressing. Move to different experiment if required. 3 0 0
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Experiment photos: