Fly Strike: 24 Hour Hatch, 2 cm Wound, Vet Today

Fly strike is maggots living on a cat, and the whole window is about 24 hours. A blowfly lays 100 to 200 eggs on a 2 cm wound or a patch of urine soaked fur, and they hatch in 12 to 24 hours once daytime temperatures pass 20 degrees Celsius. Do the 3 checks daily, never clip the fur or pull larvae out yourself, and go to a vet the same day. This is not a watch-and-wait problem.

What fly strike is, and why 24 hours decides it

Myiasis means fly larvae feeding on tissue. The flies that cause it are attracted to anything wet, dark, and smelly: an open wound, a draining abscess, diarrhea stuck to the rear, urine on the belly of an obese cat that cannot reach. Eggs hatch in 12 to 24 hours in summer, and the larvae grow through 3 stages, from 2 mm to 15 mm, in 3 to 4 days. A cat that was clean on Monday can have a moving wound on Wednesday. The damage is not only the hole: larvae release toxins, and toxemia or sepsis can develop within 24 to 72 hours of the first egg.

The 3 checks, 2 minutes a day

Do these in the same order every day from May through September, and once a week the rest of the year.

• Wound check: every scratch, hot spot, and abscess, front and back, with the fur parted by hand.
• Rear check: lift the tail, look at the perineum, the base of the tail, and the back legs for staining or a sour smell.
• Fur and bedding check: feel for damp patches on the belly, flanks, and under the chin, then look at where the cat sleeps.

What you are looking for is small and specific: a 1 mm dark speck cluster like coffee grounds, a patch of fur that looks wet and will not dry, or a wound that suddenly smells wrong. Maggots avoid light, so a wound can look shallow until it is parted. Photograph anything doubtful at the same distance each time, and put the photo next to yesterday's.

Wounds from 2 cm up: size is not the point

A 2 cm wound is the size that reliably attracts flies, but a 5 mm mat of diarrhea soiled fur does the same job. The variables that matter are moisture, smell, and access. A wound under the tail, between the toes, or inside an ear is worse than a larger one on the flank that stays dry and clean. A cat that cannot groom its own rear, because of arthritis, obesity, or a cone, is the highest risk group regardless of wound size.

Hours since eggs laid	Larva length	What you see	Action
0 to 8	0 mm, eggs only	Grainy specks stuck to fur	Vet today, do not wash off
8 to 12	1 to 2 mm	Wound edge looks wet and moving	Vet within 12 hours
12 to 24	2 to 5 mm	Visible larvae, sour smell	Emergency, same day
24 to 48	5 to 10 mm	Enlarged wound, cat restless	Emergency, toxemia risk rising
48 to 72	10 to 15 mm	Deep cavity, pale gums, lethargy	Emergency, IV fluids likely
Over 72	15 mm, leaving to pupate	Wound may look cleaner, cat still sick	Vet anyway, damage is internal

What not to do: no clipping, no tweezers, no spray

Do not cut the fur yourself. Matted fur holds the larvae against the skin, and kitchen scissors cut skin in 1 of 3 attempts on a moving cat; the vet will clip with clippers and a sedation plan, which is faster and safer. Do not pull larvae out with tweezers: they grip tissue, the body breaks, and the head stays in the wound, which causes a second infection. Do not apply insecticide, flea spray, alcohol, hydrogen peroxide, or iodine. These drive larvae deeper, damage tissue, and are absorbed through the wound. Do not bathe the cat either; water pushes larvae under the skin edges and hides the extent of the damage.

What the vet does in the first 3 hours

Expect sedation or a short anesthetic, full clipping of the area, and manual removal of every larva under good light, then flushing of the wound and often a 2 to 5 day course of antibiotics. Some cases need debridement of dead tissue and a drain. Pain relief is standard. Deworming products such as selamectin or ivermectin are used under veterinary direction only, because the dose depends on weight and on whether the skin is broken. Bloodwork is common: anemia from feeding larvae and a raised white count both change the plan.

Who gets struck, and what prevention actually works

Risk clusters in 3 groups: cats over 10 years with arthritis, cats with a body condition score over 7 of 9, and any cat with ongoing diarrhea or urinary incontinence. Add a wound, a surgical incision, or a skin fold infection and the risk doubles. Practical prevention: check the rear daily in warm months, keep the fur around the perineum trimmed by a groomer every 6 to 8 weeks for cats that cannot reach, wash soiled bedding every 2 to 3 days at 60 degrees, screen the windows, and clear food waste from the garden. Fly traps help outside but do not replace the 2 minute check.

When it is already an emergency

Go now, not tomorrow, if you see moving larvae, a wound that has doubled in 24 hours, a sour smell, pale gums, labored breathing, or a cat that stops eating and hides. Do not wait for an appointment slot: call and say the words fly strike, because clinics triage it as urgent. Cover the wound with a clean damp cloth for the car ride, keep the cat warm, and do not feed it. A cat with a 2 cm strike can be stable at 09:00 and in shock by 15:00.

Warm weather also brings the other external parasites, and the 5 minute tick check at the door is worth pairing with this routine; summer tick removal covers the mouthparts rule. Cats that spend hot afternoons outdoors also pick up pond and hose water, which is where the ear and skin problems in summer water play start. Anything used on the wound, from shampoo to spray, should be checked against the toxin list first, since cats lack the liver pathway that clears many common antiseptics.

Terms mentioned in this article

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