Flystrike: A serious problem for New Zealand’s sheep

Flystrike occurs when flies are attracted to dirty, moist areas of a sheep’s fleece – commonly the breech area, especially if dags or urine stains are present. The flies lay eggs, and when hatched, the resulting maggots begin to eat away at the sheep’s skin. As this happens, skin and muscle tissues are eroded and release toxins that spread throughout a sheep’s body. The process attracts more flies, exacerbating the problem. Warm, humid months are the most common time for this condition to appear; in New Zealand, the main flystrike season can extend from October to May.

Symptoms

Sheep experiencing flystrike may not show symptoms until the problem has become severe, so it’s important to keep a close eye on your flock. Initial symptoms include irritation in the form of tail twitching, stomping, and rubbing or biting the affected area; if you notice your sheep is more fidgety than usual, this may be an early sign. Affected sheep will likely exhibit a decrease in appetite and an increase in shade-seeking behaviour, depression, and may experience dehydration. Later in the process, wool will begin to fall out, and blackening skin and sores will appear, presenting a foul odour.

Mortality

Flystrike can be a fatal condition if left untreated. Sheep will usually die of fluid, protein and electrolyte loss, as well as toxaemia and ammonia poisoning. Some sources suggest that sheep can die from ammonia poisoning 3–6 days from the onset of the first strike.

Prevention and treatment

Flystrike prevention is multi-faceted, and starts with consistent hygiene practices and upkeep of sheep. Shearing is key; keeping fleece short and clean reduces dags, and areas in the wool that can attract flies. Prevention is always preferred to treatment, so be sure to keep a close eye on your sheep’s health and behaviour, especially during the warmer months. Finding and treating maggots and sores when they’re small is the best way to prevent a bigger issue. Examining your paddock environment can also help prevent future strikes; if there are more humid areas, like sheltered gullies, it can be beneficial to keep your flock away in warmer times of year. Flystrike prevention can also include chemical methods. Lifestyle block NZ recommends for treatment that maggots are removed and “the sore should be treated with flystrike powder containing diazinon, available from your veterinarian or rural supplier.”

Once flystrike sets in, affected sheep should be removed from the rest of the flock to prevent spread. After removing excess fleece and cleaning the area, treat sores with flystrike treatments from your veterinarian or rural supplier.Check affected sheep daily while they recover. Infection can cause fever, so be sure to provide your sheep with lots of food, water, and shade. We always recommend consulting your veterinarian for the best care and tips on how to treat your specific flock.

Buzz is just one of the manypet sheep who experience flystrike every year in New Zealand, and we’re so glad he found his way to SPCA so he could heal. In the two months he was with us, he made a stunning recovery, and became the happy, social sheep we knew he could be!

When recovered and desexed, he found his forever home with a larger flock of sheep – made up of mainly rescues! While we don’t know anything about Buzz’s past before he came to us, his adopter tells us he’s “clearly not aware that he’s a sheep,” so we’re thrilled he gets to join a group where he can learn the ropes.

All animals deserve a high standard of welfare and care. Flystruck sheep like Buzz have the opportunity to become healthy and happy once again, and here at SPCA, we’re committed to making recoveries like this possible – and finding great forever homes for our adoptable animals, just like Buzz.