During my farm visit to a cow-calf farm, I immediately notice that some very young calves are abnormally slow. What is going on here?


The animals had a dirty tail and a dirty hindquarters. Wet spots were clearly visible.

My first impression was Myiasis, a diagnosis confirmed by the ammonia smell and the presence of dead tissue with maggots in various stages underneath.

The calves were immediately washed with an agent that kills maggots and with a wound disinfectant.

Then they are treated with a long-acting combination drug consisting of antibiotic and analgesic.


The farmer told me that a cow had calved the day before my visit. Her calf was hiding at the edge of a forest. The calf was lying in tall grass and was already covered with flies, especially the green meat fly ("Lucilia sericata").

On the calf you could already see small maggots. A quick treatment with a maggoticide and fly repellent brought relief to this (several hours old) calf.



A maggot infection is caused by flies (including the green meat fly), which are attracted to body odors.

More specifically, ammonia odor.

A wet fur, often caused by body fluids, is the perfect place for these flies to lay their eggs.

A fly lays hundreds of eggs, which, under favorable conditions, hatch within hours and result in an invasion of larvae and maggots.



The larvae and maggots produce enzymes that cause skin and underlying tissue to decompose.

The decomposing skin becomes soft, making it even easier for the maggots to pierce and digest it.

This makes it more easy for them to absorb their host's nutrients.


It is a downward spiral, in which more and more flies are attracted to the decomposing smell of the skin.

Finally, the affected animal dies from the toxins (in the enzymes produced by the maggots), from exhaustion, and from damaged tissues. 

Thankfully, it all ended well here. The farmer is alarmed by these 3 cases in his herd.

He is now monitoring his group of animals extra closely and doing preventive fly control.



A maggot infection is unfortunately not limited to cow calf herds.

In fact, I regularly see them on farms where newborn calves are housed in calf Iglo's.

I also see maggot infections in sheep, goats, dogs, rabbits, guinea pigs, even in the hooves of horses. 

You are hereby warned!