Thanet Star

Breeding Your Own Killer

the house fly
This is a fly. One of many types of fly that you are likely to see this summer. This summer we are likely to see a lot more of our friend the common housefly as well as his better dressed brethren - the blowfly family.

Blow-flies (also frequently spelled blow flies or blowflies) are members of the family Calliphoridae of flies (Diptera). Some members of this family are known as bluebottles, clusterflies or greenbottles. Flies in this family are often metallic in appearance and between 10 to 12 mm in length.

While not as common as the house fly the more fancy looking blowfly family is making something of a comeback in the UK. This is thanks largely to the dedicated work of many local councils in creating new breading grounds for all species of flies with their special reduced refuse collection projects.

At the height of the summer season, a generation of flies (egg to adult) may be produced in 12–14 days.

One of the side effects of fortnightly collections is that once more the fly population is allowed to increase in the UK. Is this good, bad or indifferent I wondered so I investigated.

You may find some images in this report disturbing.

An adult female blowfly (such as the bluebottle) can will lay a batch of approximately 200 eggs and can lay around 10 batches of 200 in her three-week life span. This amounts to 2,000 potential flies in a three week period and 2,000,000 could potentially be produced by her "grandchildren". Eggs will primarily be found on a dead meat, such as might readily be found in refuse, but can also occasionally be in open wounds or excrement.

Now a little maths before we continue. Regular refuse is collected by many councils every 14 days and there is talk of further reducing this to once a month (an average of 30 days). It takes just 12 days from the first batch of 200 eggs to be ready to lay eggs of their own and that's if just one female blowfly uses your dustbin to breed.

That's nothing on the common housefly. The female can lay up to 9,000 eggs and lives as long as a month. Even so assuming that for some reason the housefly is only as successfull as the blowfly (unlikely).

In the second two week wait there is enough time for 20,000 eggs to be laid and in the third 14 day period 2,000,000 eggs (at least). Even given that some maggots will fail to mature in time the refuse collectors face additional health dangers from this high fly concentrations as do any pets or bin owners that might get too close.

Let's imagin that you scrubbed your bin after the rubbish was last collected to a fanatically clean standard so that only one bacteria existed in your rubbish the day following all thatactivity. By the next collection date there would still be a number of bacteria so huge that if it were it written down in full it would fill at least one side of A4 paper as it goes on for 405 digits. Roughly 3.8398 times 10 raised to the power of 404 (exactly 2^1344-1 if you are interested in seeing it written down).

That's each bacteria in your bin. That's more than a novemnonagintillion (1 with 300 zeros after it) per bacteria witht he real number likely to be many googol's (1 with 100 zeros) of centillions (1 with 600 zeros using the British/Europian convention) of bacteria. If even one of those was dangerous your rubbish is now deadly. That extra week does more than double the number of bacteria growing in your rubbish it allows them to feed off traces of food and double in number more than 600 extra times.

Let's be honest mummy fly will have taken a large number and range of bacteria to your rubbish when she laid her eggs. It is this wealth of bacteria which produce the characteristic smell of rubbish (as they chemically break it down for food). It is the wealth of flies that then carry huge numbers of the bacteria (which you have been breeding) when they leave your rubbish and come and visit you at dinner time.

These increasingly common blowfles (bluebottles, greenbottles, etc.) are vectors (carriers) of a number of diseases such as dysentery, myiasis and general bacterial infections. Of these three myiasis is probably the most disturbing. Myiasis disease caused by parasitic fly larvae feeding on the host's necrotic or living tissue. This can effect animal or human.

Myiasis of the eye
A 5 year old Hondurian patient receives treatment for a case of Myiasis near his eye.

The greenbottle larvae are used in what is called maggot therapy due to the fact they feed on necrotic flesh (dead cells) exclusively while most other flies feed on living flesh as well. Prior to researching this article I did not know that and was under the impression that all fly larvae were like the larvae of the greenbottle.

While not all flies present the risk of myiasis some that are now finding the breeding contritions in Britain greatly improved do present such a risk. That risk goes along with the transmission of all sorts of bacteria onto everything that a fly lands on. That includes you, your food and every part of your house where flies get in.

Salmonellosis has also been proven to be transmitted by the blow fly through saliva, feces and tarsi. Adult flies may be able to spread pathogens via their sponging mouthparts, vomit, intestinal tract, sticky pads of their feet or even their body or leg hairs.

As vectors of many diseases, the importance of identifying the transmissible agents, the route and prevention are becoming increasingly important. With the ability to lay hundreds of eggs in a lifetime and the presence of thousands of larvae at a time in such close proximity, the potential for transmission is high especially at ideal temperatures.

Which while an impressive collection of ways to kill us it is again nothing on the more common housefly.

In colder climates, houseflies survive only with humans. They have a tendency to aggregate and are difficult to be dispelled. They are capable of carrying over 100 pathogens, such as typhoid, cholera, Salmonella, bacillary dysentery, tuberculosis, anthrax, ophthalmia, and parasitic worms. The flies in poorer and lower-hygienic areas usually carry more pathogens. Some strains have become immune to most common insecticides.

House flies feed on liquid or semi-liquid substances beside solid material which has been softened by saliva or vomit. Because of their high intake of food, they deposit faeces constantly, one of the factors that makes the insect a very dangerous and heinous carrier of pathogens.

Clearly the ongoing reduction of collections wherein bacteria and larvae can breed presents a significant health risk with the refuse approaching it's most potent when households are required to drag it onto the public curbside early enough for children to walk past on the way to school.

When, as often happens, collections do not take place when they should the chances of significant fly related health problems becomes all the greater. With the hotter weather upon us we are going to want to have windows open right when the disease spreading population of flies are at the highest. Last nights dinner at the bottom of the kitchen bin that did not make it to the main bin for this fortnights collection is going to be an idea nesting ground for 200 or more baby flies.

So what can you do?

Very little, to be honest. While you and your household can take every precaution and that includes keeping your rubbish in the freezer it does not take a maths whiz to work out that if 99% of people did the same thing that leaves over a thousand bins with anywhere up to 200 flies hatching or hatched and up to 28,000 at different levels of maturity.

The only real way is to close the gap and prevent the breeding cycle of the flies from taking place. Ideally weekly processing or collection of household waste should suffice.

Suggested further reading: Blowfly, Housefly, Myiasis, Lucilia Illustris, Maggot Therapy, large numbers and very large numbers.

You may also be interested in the theory behind some of the numbers

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Public Comments

This Normal comment was left by Nikki [score: 0]:

Oh my goodness! I started to read this article as I have been having a problem with flies in my house. Even though I clean they still persist in flying around my house and the only way to kill them is using fly spray which is not a great solution because of its disasterous effects on th world.

I never in all my life realised how bad and how disgusting flies can be and what they could cause.

I definately feel refuse collection should be more regular! Especially with the problem of seagulls in this area causing disruption and waste spillage on our streets.

Very interesting information Thankyou!
14/07/2008 08:07:44

This Normal comment was left by Matt B [score: 0]:

You are quite welcome. I was surprised by some of what I discovered too. One thing we can do is to freeze all our rubbish until bin day but who wants a freezer full of rubbish?
15/07/2008 16:45:02

This Normal comment was left by Kate [score: 0]:

Exactly! Who wants a freezer full of rubbish? I bought mine to keep food in - novel or what LOL

I'm completely against this fortnightly collection idea. It's not that I'm against recycling, just that I'd rather not fall victim to an avoidable epidemic. In the early days of the refuse collection system, weekly collections were decided on because they broke the life cycle of flies, therefore not allowing them the chance to massively reproduce in areas of habitation. For some reason councils no longer think this applies
17/07/2008 21:30:02

This Normal comment was left by Matt B [score: 0]:

I find it all troubling. But then TDC are not exactly well known for any form of reasonable thinking.
21/07/2008 08:33:29

This Normal comment was left by Matt B [score: 0]:

That is not to say that they do not think more that they have a very poor reputation in that area.
02/10/2008 10:50:14
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