It’s enough to make your skin crawl. Lice, fleas and bedbugs in their thousands are crawling all over our nice clean homes, their numbers swelling by the moment as they gorge on our blood. Does this largely unnoticed nightmare herald the return of killer diseases? Are our lifestyles to blame? Do our doctors know what to do? Ask John Maunder, head of Britain’s Medical Entomology Centre near Cambridge. He’s spent 35 years studying what most of us regard as deeply unwelcome visitors at the country’s only unit specialising in the medically-important insects found in temperate zones. But with most major pest-borne diseases still afflicting poor countries in the tropics, Claire Ainsworth asked Maunder why he’s worried.
Most people in Britain see bugs as a nuisance, not as carriers of diseases like plague. Are we wrong?
We don’t get too much disease, but that really partly depends on how well we control the insects that carry them. Basically, any flea that bites a rat and a human can carry plague. Black rat fleas are usually better at this, and we have few of them, but the last two natural outbreaks in Britain (Bristol, 1922, and Suffolk, 1917) were both spread by brown rat fleas. And we’ve never had more brown rats and their fleas than we have at the moment, with less being done about them. Plague is not disappearing from the world and there are still people who feel it is just a tropical disease. Well, there might have been people in London in 1660 who thought that, but not by 1670!
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What else should we watch out for?
The great louse-borne disease is typhus. Typhus was common in the 19th century. Lice are blood-sucking insects and that’s how they acquire the disease, then spread it through their faeces. The faeces contaminate food, and can be inhaled or scratched into louse bites. Even with antibiotics, the odds are still 6 to 4 on that you would die from it-and the antibiotics would have to be used very, very quickly. Typhus is spread primarily by clothing lice, although head lice can also carry it. We’ve got far too many head lice in the community at large, not just on children.
But I thought we had that under control?
We’re actually better at treating our cats for fleas than we are at treating ourselves, and we’re prepared to spend a lot more on it. But the really worrying thing is we’re beginning to get more clothing lice. This is because our washing machines no longer boil clothes-we have energy-saving buttons and low-temperature washing powders. If you wash lousy clothing at low temperatures, all you get is cleaner lice. By the time they’ve gone round and round in the tumble dryer, all the clothes are lousy. And then, of course, people tend to put those same clothes back on straight away.
Does that matter?
The old bath night once a week was successful against lice because we took clothes off and put other clothes on, giving the lice in the discarded clothes time to die from starvation. The increase in clothing lice means some louse-borne diseases are coming back, things like trench fever, a minor relative of typhus. We really do not want typhus back. One of the odd things is that we don’t completely understand exactly why it disappeared from Britain. If we don’t understand why it went away, we won’t be able to understand how it might come back.
Do lice affect us in less dramatic ways too?
If you get enough lice on you, you begin to feel quite unwell. That’s because they inject saliva when they bite and this saliva is fairly poisonous to us. There’s a word in the English language to describe how you feel-you feel lousy. And if you’re feeling lousy and not working very well, you may develop an educational disability and become a “nitwit”.
And could malaria make a comeback?
Here in East Anglia we have the right mosquitoes, but not many of them. Where we do have large numbers, they are only in small areas with few people. So we are not likely to get serious malaria problems again. In order to transmit malaria, the mosquito has to meet somebody with malaria-and we tend to put such people in hospital. The trouble comes because you may not know you’ve been bitten. Plenty of people say that the insects never bite them, so they don’t need to take anti-malarials. But they do bite, and people do need to take their anti-malarials. Hundreds of people catch malaria each year, having gone abroad without taking proper precautions, and they then come back to Britain.
How can they not know they’ve been bitten by mosquitoes?
The biting process is extraordinarily fascinating. They land on us without us noticing, drill a hole with their mouthparts and inject some of their saliva. This saliva contains a local anaesthetic to stop the bite hurting at the time. They also inject an anticoagulant into the wound, so quite a lot of insect protein goes in. Eventually, we become sensitised to the insect’s saliva, so we become allergic to the proteins of that species and start to itch. This is very important when it comes to malaria. If you go abroad and are bitten by a species of mosquito you’ve never met before, you will not react to their bites, and you’ll think you’re OK-when you could have contracted malaria.
What is the most important single pest at the moment?
The house dust mite. It is virtually the sole cause of childhood asthma, which kills about 2000 people a year in Britain as well as causing immense suffering. We shed enormous amounts of skin into our beds, but mites can’t eat it providing it remains completely dry and unchanged. If the shed skin goes mouldy-and there are specialist moulds that live in damp beds-then the skin scales become softer and more nutritious. So if bedrooms are absolutely dry, fine. Unfortunately, too many bedrooms are very damp. Bronchial asthma was quite rare among children until we started to block up chimneys and double-glaze windows and do everything to decrease ventilation in our houses, forgetting that humans need a constant supply of clean, fresh air. In fact, many people who air their beds and sleep with the windows open won’t have any house dust mites at all. But the average air quality in a bedroom at dawn is so low that if you found this level in a workplace, the employers would be prosecuted.
I’m sleeping with the window open! How else can people banish dust mites?
Quite a lot live in people’s pillows and we are, thank God, beginning to convince people of the idea that pillows should be washed or thrown away. Some people were using six-year-old pillows continuously without being washed, in unventilated bedrooms where the windows were kept shut at night. At the end of the six years, a tenth of the weight of the pillow consisted of old human skin, mould growing on the skin, mites growing on the mould, dead mites and mite dung. If you ask children to put their heads down on bags of grot like that night after night for a third of their lives, you don’t have to invent traffic fumes as a cause of asthma.
How many people die because of insects every year in this country?
Strictly speaking they’re not insects, but if you include the mites then you’ve got 2000 straight away because of the asthma. Everything else, such as fatal wasp and bee stings, probably adds another 40.
My home is getting more unpleasant by the moment. Is there anything else lurking under the skirting boards?
Bedbugs. Bedbugs live in the cracks and crevices of a building, always within a couple of metres of a bed. They visit the bed in the middle of the night, usually when it’s darkest. They won’t get under the bedclothes-that scares them stiff-so they bite the exposed bits, usually the face. They tiptoe across your face without waking you because they have beautifully sprung legs and put their mouth parts deep into your skin. Their instinct is to bite the same person over and over again and each bedbug will walk past half-a-dozen sleeping people to reach that person.
Are there any other aspects of our modern lives that make us easy prey?
Increasingly we’re getting insects in food, mainly due to the latest fad for organic produce. We examined six consecutive batches of Californian grapes a couple of years ago and found live black widow spiders in all of them-they’re going to kill somebody sooner or later. But we’re getting all sorts of other insects flown in alive that used to come in dead in imported food. Now they’re coming in alive and angry!
Has anyone got hurt?
The other day, a woman picked up a bunch of bananas in a supermarket and was stung by a scorpion. Luckily everyone did the right thing. They sent the scorpion to us fast so we could advise the hospital which anti-venom to use. It was one of the most poisonous kinds in the world-Centruroides. I don’t think it could have given her a complete dose of the venom, otherwise she’d be dead.
We don’t seem to be on top of this. What should we be doing?
Teach our doctors more in basic training. All doctors used to get 20 hours of medical entomology in their basic training. It was stopped around 1935 because they thought medical entomology was only about tropical medicine. You’d think it would be necessary, but no doctor gets even five minutes on insect bites or any kind of medical entomology. Which is why we’ve got trouble with asthma.
What else should we do?
We can partly counter insecticide resistance by better and safer insecticides, and we’re also using growth regulators which can stop an insect’s reproduction. But anything will become resistant to anything given enough time and enough fools. We need to change aspects of our lifestyles to keep insects at such a low population that they really don’t affect us much. With head-lice infestation, we should treat it for what it is-an infectious disease. If you want to half-treat an insect, half-kill it and make it resistant, put a shampoo on and wash it off again almost immediately! What we should do is put the control agent in the blood the insect feeds on. We’ve got things for flea control in pets which are so good they don’t affect the animals at all but have a devastating effect on the fleas. The vets are miles ahead of us. We need proper tablet treatments for children.
Who else asks you for help?
Apart from constantly being called on to date corpses by the maggots in them, we’re also helping detect people who make a good living out of claiming that insects have been found in various bits of food. Fraudsters are getting clever. Sometimes they cook the insect before they put it into the products, because a raw insect in a cooked product didn’t always ring true. But sometimes they cook them the wrong way. So if you get a microwaved beetle in a fried product, you can be fairly certain something’s up.
Will we ever rid ourselves of parasites?
I’m not sure whether we should get rid of them completely, because I think that anyone who has never seen a flea jump is socially deprived. And even if we did eradicate something from Britain, we’d be constantly defending ourselves against influxes from abroad.