Most chicken keepers at some point have to deal with a mite infestation, be it on the bird, or in the coop. There are many types of mites, some more well documented than others and some yet to be classified.

I first came across the Straw Itch Mite (SIM) about six years ago and in my ignorance mistook it for Scaly Leg Mite (SLM). I had a bantam hen sitting on a clutch of eggs in her tribes coop and noticed when she left the nest each day to eat, poop and bath that her feet in particular looked sore and some of the lower scales on her legs were missing.

My problem was that my usual treatment for SLM is to smother the legs in a 75% to 25% mixture of Vaseline and Betadine which I’ve found works well; the Vaseline smothers the mites and the Betadine helps to prevent infection and given Betadine is antifungal, deals with the mite droppings that can give the crusty look to SLM. While this treatment is fine for most circumstances it is problematic for a hen sitting on eggs. The likelihood is some of the mixture will get transferred to the eggs as the hen moves the eggs underneath her. Part of the transfer mechanism will be through direct contact of the eggs to the hens legs. More concerning is the mixture gets transferred to the hens belly and chest which is warm making the mixture more viscous, and in the rubbing motion hens make when sitting to polish and improve body contact with the eggs coat the eggs and sealing the pores in the egg shells.

The solution to the problem I chose was to dip the hens legs in rubbing alcohol for about 20 seconds which drowns the mites and disinfects the site.

This treatment while working in the past for other chickens with SLM didn’t seem to work with the sitting hen and within a couple of days her legs looked sore to the extent that areas between the toes and places where scales had been were bleeding slightly.

The hen hatched her chicks and within a few days her legs started to return to normal.

Some years on after a couple of further incidents of sitting hens having a similar problem a hen called Knock sat on her clutch and her feet and legs looked extremely uncomfortable to the point where I had no choice but to try and treat her. I had reached the conclusion that this wasn’t SLM and didn’t really know what it was.

I spoke to a local chicken keeper and explained the problem and what I got told was there were spiders in the straw and they bite the hens legs. I looked and I couldn’t see any spiders. If my Catalan language skills had been better I would have known that mites are called spiders here and improved my understanding of the problem a lot more quickly.
It took some very unpleasant rash problems on myself and a couple of others who live here from handling the hay and straw to make the final connection.

I spoke to the person who had told me about the spiders in the straw again and found out that these were minute spiders, smaller even than SLM and got told more clearly what the symptoms were. They described the symptoms very clearly, right down to the raw and bleeding patches between the toes and the absence of the smaller scales particularly on the lower part of the leg.

I did find many references to straw itch mite on the Internet. Some further reading on various sites and I had my explanation.

On a day to day basis the chickens contact with straw which has a lower density of Itch Mites than hay doesn’t cause them any noticeable problems. When a hen is sitting on a clutch the ambient humidity rises as does the temperature. This creates an ideal environment for the mite to reproduce. An adult mite can produce hundreds of offspring and apparently they are ready to feed immediately. The straw the hens is sitting in is now infested with Itch mites which proceed to feed on her.

I’ve had a few Itch mite bites from handling the hay here and they are really itchy and form a rash. It’s almost impossible not to scratch them. Of course scratching just makes them worse. It seems that the damage done to the scales and the raw patches between the hens toes is from the hen pecking at the bites.

These are not the clearest of pictures but they do show some of the damage. Unfortunatly I didn't take any pictures of the other incidents and any future chances are not under my control.

Permethrine and probably other treatments for mites will kill them. Having properly kept straw seems to reduce their population. There’s is a problem though and that is one doesn’t want to be soaking a nest with a clutch of eggs in it with any chemicals and in my experience the only time the Itch mite becomes a serious problem is when a hen is sitting on a clutch. Administering drugs such as Ivermectine isn’t a solution either. While the mite may die after feeding it still bites the hen and she will cause further damage by pecking at it.

It may be possible to change the bedding type, but it would likely be a few days into the hens sit and there is a chance of her abandoning the nest if it’s interfered with to such an extent.

A lot of the hens here sit and hatch on straw nests. It would seen possible that either some hens are allergic to the Itch mite as some humans are, or the mite wasn’t in the straw in the first place given not all hens show the symptoms.

In the case of Knock in the pictures above I treated her feet and legs with a cream called, Blastoestimulina which I’ve used for other wounds in the past. While it appeared to make a difference (the sore rash appearance became less vivid) her legs and feet didn’t improve significantly until she had left the nest.

There are lots of reports on SIM effecting other creatures but none that I’ve found on this particular problem with sitting hens.