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How Houseflies Can Bring Dangerous Bacteria Into Your Home

I enjoy educating others about potential health hazards that can affect their home.

Though it might seem relatively harmless, the common housefly can bring dangerous bacteria into your home.

Though it might seem relatively harmless, the common housefly can bring dangerous bacteria into your home.

One of the most common insects on the planet is the housefly (Musca domestica), and it can carry over 100 pathogens dangerous to humans.

Our food is one of the main targets likely to become contaminated, so let's have a look at how the housefly spreads germs.

The Characteristics and Life of the Housefly

  • The common housefly is around 6–8 mm in length, while the lesser housefly tends to be around 6 mm (Bay Environmental Science UK & Ireland).
  • They have large, compound eyes: each section is called ommatidia. The lenses of the ommatidia are a thin, elongated-shape and are found on the outside of the eye. The thousands of ommatidia make a broad field of vision for the fly, with each individual lens acting as a separate eye. Vision is created almost like a mosaic that converges into one image. Unlike humans, however, a fly's eyes are immobile.
  • A fly cannot bite. Instead, its mouth consists of a spongy pad. This is used for releasing saliva and digestive juices that turn its food into liquid. The spongy area of its mouth then soaks up this liquid.
  • Depending on the size of the fly, a female can lay up to 500 eggs over a period of three to four days. Within a few hours—normally between 8 and 20 hours—of the female laying her eggs, the maggots emerge. They eat anything and prefer a warm, moist environment. The maggots continue to develop and grow for the next 4 to 10 days and then move onto the next stage of their growth.
  • The next development is the pupa stage. The maggot remains as a pupa, wrapped up in a skin, for up to ten days, before finally emerging as an adult fly. Their lifespan is around 15 to 30 days, and the female can begin to reproduce by the second day of her life. The female fly is larger than the male.
  • They can travel up to six miles in a 24-hour period, although most of them tend to stay around their breeding areas.

Now that we know how they live and breed, let's look at how they introduce germs into our homes.

The mouth and tongue of a housefly.

The mouth and tongue of a housefly.

How Houseflies Infect Our Homes

Houseflies are no doubt one of the biggest pests of the summer and one of the biggest germ carriers. Part of the problem is the way they live.

Flies walk among rotten food and other rubbish, feces, and decaying animals. They then fly straight into your home and onto your food. We've already mentioned how they liquefy food and then eat it. The main way that they contaminate our food, however, is when they rub their legs together.

Despite our feelings that the housefly is a dirty animal, it actually spends a good part of its day cleaning itself. If its body, eyes, and antennae become clogged with dirt, then the fly's ability to use these areas to find its way around is severely compromised.

It uses its legs to clean dirt from every area of its body and then rubs its legs so that the dirt falls off. Unfortunately, if the fly happens to be on your kitchen surface or food, then the dirt shaken off will land there.

What Kinds of Bacteria Can a Housefly Carry?

There are many kinds of bacteria that a housefly can carry—some studies show up to 200 different kinds—but a few of the most common are:

  • Shigellosis: Bacillary dysentery and other diseases causing diarrhea.
  • Salmonellosis: Food poisoning, typhoid, paratyphoid, and enteritis. Although flies are capable of carrying these diseases, it is much less common than the shigellosis diseases.
  • Bacteria causing conjunctivitis: This mainly occurs in areas such as Asia, Africa, and the Pacific regions.
  • E.coli (Escherichia coli): Can lead to diarrhea, abdominal cramping, nausea, and vomiting.
  • Poliomyelitis: Houseflies do have the ability to transmit this virus—and other similar viruses—but normally, only people who are perhaps already ill would be the most vulnerable.
  • Parasitic worms: Especially tapeworms.

Keep in mind that these are just a few of the many bacteria and viruses that houseflies can potentially transmit. Although this looks like an alarming list of bugs and diseases, flies don't always carry these pathogens along with them though. In addition, most of us have good immune systems that block the majority of dangerous bacteria and viruses.

In most cases, simple precautions and hygiene in and around the home will keep people safe for the majority of the time.

More Interesting Facts About Flies

  • Flies feel, taste, and smell with the hairs that cover their body. In particular, the hairs that are around its mouth and on its feet are both used for tasting food. So basically, a fly can taste what it walks on. If they have found a potential food source, they put the food in their mouth to taste it again.
  • Flies also have sticky pads on the bottom of their feet that allow them to walk upside down on smooth surfaces like glass with ease.
  • Despite the fact that flies do carry numerous germs, they are also essential for the whole ecosystem. They are important, along with some other insects, in converting waste products such as rotten vegetation and feces into soil. They also help to pollinate some plants.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2013 Helen Murphy Howell


frogyfish from Central United States of America on August 02, 2015:

Interesting and informative hub on these beautifully ugly creatures. The macro video was vivid! However, I do think there are some flies that bite -must have a different specie? I did not know basil was a repellent, but do use other essential oils - especially the lavender and lemon. We did use your electric zapper for a short while - and yes, got every kind of bug except the mosquitoes we were after. I don't probably agree that the fly-virus is a good idea either - we definitely need all the pollinators we have, as so many bees are being killed with chemicals. Your informative hub was a great read, so thank you!

Helen Murphy Howell (author) from Fife, Scotland on October 16, 2013:

LOL! Yes they are nasty little blighters. I do love nature and of course animals, but have to admit to having a hard time with flies and slugs - Yuck!!

Mackenzie Sage Wright on October 08, 2013:

Ewww... I always hated flies in the house but now I'm going to be just grossed out. That is nasty!

Helen Murphy Howell (author) from Fife, Scotland on June 01, 2013:

Hi Jo_Goldsmith 11,

Many thanks for stopping by and glad you enjoyed the hub.

I'm the same, I can't stand flies or wasps - bees I don't have a problem with. My dogs are going nuts at the moment trying to catch any flies that do come into the house, so I've got the insect netting up, especially for nighttime, there's nothing worse than trying to sleep with some daft moth or crane fly buzzing about your head!!

I'm not sure, but I would think that if it is 'lemon scented' then it would have some of the extract from a lemon distilled into it and I would imagine it would work just the same.

Many thanks for the vote and the tweet!!

Jo_Goldsmith11 on June 01, 2013:

This is a great article and advice. I don't like houseflies and our cats are not doing their jobs lately in trying to catch them. We will be installing a screen door soon. :) I can keep our front door opened and let the air in and keep the flies out! I didn't know about wiping down the counter tops with lemon. I use Mr. Clean lemon scented. Is this the same thing?

Voted this Up +++, shared & tweeted. thanks again. :)

Helen Murphy Howell (author) from Fife, Scotland on May 11, 2013:

Hi mikkar - many thanks for stopping by and for leaving a very interesting comment. Yes, I think the powers that be always have a reason for creating everything even if we don't always understand it. Now, I didn't know about hungry cats eating house flies, my dogs certainly chase them! LOL!

Michael from Nairobi on May 11, 2013:

Sometimes you wonder why God created some things, but when you understand how ecosystem work you apprecite them. A hungry cat also eats houseflies

Helen Murphy Howell (author) from Fife, Scotland on April 26, 2013:

Hi Rasam, I know flies do have their place in nature, but like you I can't stand them. Especially when they target your food. Also when out with the dogs, I hate the way the can really harass them! I had a fly swatter once but I missed most of the time so gave it up!!

Helen Murphy Howell (author) from Fife, Scotland on April 26, 2013:

Hi sparkster - lol! yes, yuck indeed! They are all part of nature to be sure but why do so many of them have suck crappy habits!!

Helen Murphy Howell (author) from Fife, Scotland on April 26, 2013:

Hi ChitrangadaSharan, lovely to hear from you as always and I'm glad that flies are not a problem for you and I agree, even one fly is very irritating!

Helen Murphy Howell (author) from Fife, Scotland on April 26, 2013:

Hi Om Paramapoonya, many thanks for stopping by and glad that you will give the oils a try. I certainly find that lavender works well where I live but there are many to chose from - good luck!

Gypsy Rose Lee from Daytona Beach, Florida on April 26, 2013:

Thanks for this informative and useful hub. I sure hate flies. They are a pain. We keep up plenty of fly papers and have swatters about because where we live we have a very old house and no air conditioning. So summer means open doors and open windows. Passing this on.

Marc Hubs from United Kingdom on April 26, 2013:

Oh how beautiful God's creatures are haha! Very informative hub... but yuck!

Chitrangada Sharan from New Delhi, India on April 25, 2013:

Very useful and informative hub!

I don't have much problem of flies within my home as such, but I do take care that they don't enter my home, simply by avoiding sweet food here and there and keeping general cleanliness. Even one fly is very irritating. Thanks for this helpful hub!

Om Paramapoonya on April 25, 2013:

Thanks for your helpful advice. I do have a fly issue every summer here. I like the idea of using natural oils. It can repel flies and make the house smell nice at the same time. I'll definitely give this trick a try.

Helen Murphy Howell (author) from Fife, Scotland on April 25, 2013:

LOL! Hi Frank, I know, not the most positive way to start the summer - not that Scotland has that great summers at the moment, but we might get a surprise this year! But yes, the spiders do help and I have netting and lots of lavender hanging around inside and out and it tends to keep the little -------- away for most of the time!

Frank Atanacio from Shelton on April 25, 2013:

House flies are nasty.. I get a lot of spiders because of the flies .. because I live near the woods and the flies are attracted to the rotting wild-life.. I have taken measures to keep them outdoors.. but spiders do help.. thanks for reminding us of the nasty side of summer LOL