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Fly Strike

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Staff member
Mar 10, 2009
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Coventry UK
What is fly strike?
There are several flies around the world that lay their eggs in the soiled bottoms of mammals, whether that is lifestock or pets during the summer months, whenever there is dead tissue. The maggots then develop by burrying into the flesh. Blow strike flies can smell the ideal breeding ground from a surprising distance.

How to spot fly strike and what to do
The very first signs are reddish, slightly bumpy dots around the genitalia and bum end area where the eggs have been alid, which then develop into white dots as the maggots develop around the swelling genitalia/in a swelling area. The piggy will try to bite the affected area and is looking increasingly unwell; if you can catch it before it does, it has a chance of survival.

If you happen see a maggot, please immediately check all pets and change your bedding; it is not necessarily a fly strike maggot, but you need to make sure.

If spotted early on and seen by a vet right there and then as a life and death emergency, a guinea pig (or rabbit) can be saved, otherwise the only kind thing you can do is having your piggy put to sleep as quickly as possible to spare it further suffering. It is one of the most horrible and excruciating ways a guinea pig can die!

The progression is very quick in guinea pigs andd rabbits; you cannot afford to wait even a few hours, you really need to be seen by a vet immediately - it is an absolute life or death emergency!

If you cannot be seen by a vet there and then try to remove any maggots you can spot as much as possible until you can get to the vet. Your guinea pig will still need a thorough go over from a vet, have any remaining maggot bits removed, and if there is still a chance of survival, will need an antibiotic and thorough disinfection.

You can usually find an out of hours contact on your vet's answering machine in an emergency, but especially in urban areas it is worth looking up all available out of hours services, as there are now cheaper ones available in the UK - ideally before an emergency! Don't wait for an exotics vet to have a slot; any local vet should be able to spot and treat fly strike.

How to minimise the risks of fly strike
- Use fly paper in the guinea pig areas during the summer months. Keep in mind that flies can get indoors, too, even though you have to be extremely unlucky if this happens to be a blow fly!
Normal house flies are not a problem, as they do not lay their eggs into the flesh of living animals, but the less flies there are, the better!

- Keep any bedding changed regularly and frequently, especially in the toiletting areas. This is even more important in outdoors guinea pigs. Remove any poos from other animals promptly (defecating cats, dogs, foxes etc.) and avoid putting your piggies' run near any soiled areas.

- Don't put any guinea pigs with acute urinary tract issues on the lawn. Make sure that you have cleaned and dried off any older/frail guinea pigs that struggle to clean themselves before putting them out on the lawn.

- Keep the hairs of long-haired guinea pigs that can get soiled and matted cut short at least around the genital and bum area. Ideally all long-haired guinea pigs will profit from a shorter summer haircut of at least the underlayer of their hair for their comfort.

- Use fly netting for open windows or an indoor cage, hutches and runs if you have got guinea pigs that could be at risk from fly strike. While indoors fly strikes are generally rare, we have had first-hand accounts of well cared for, but frail piggies being affected by it - in one case where the blow fly in question was never noticed in the room!

Guinea pigs at increased risk of fly strike
While healthy guinea pigs in regulary cleaned surroundings and able to keep their genital/bum area clean are not at any risk of fly strike, old/frail or ill guinea pigs can become a target.

At a higher risk of fly strike are:
- any long-haired guinea pigs with badly matted and/or soiled bums
- any older/frail guinea pigs that cannot clean their genitalia well/suffer from weak bladders
- boars with a major build-up of untreated impaction
- any guinea pig with open wounds (like skin biting with mange mites or ringworm etc.)
- any guinea pigs with blood in their urine, even if the blood is not visible to the eye (UTI, stones etc.)
- most at risk are any neglected guinea pigs living in filthy outdoors conditions and suffering open wounds through skin parasites, fungal or fights etc.

Please bring these piggies indoors and do not put them out on the lawn without thorough and regular inspection in the 2-4 days afterwards unless they have been cleaned up well beforehand or their problem has healed.
Carefully check the genitalia area when you bring any guinea pigs inside from the lawn and ideally every night with outdoors guinea pigs.
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