Two hamsters balding at roughly the same time

[timidLittleHamster]

I have two female Syrians, which in their own cage (120cm x 60cm), but these cages are stacked so one cage is on top of another. It's a custom build we made.

Some information about them both:

Maddie

• age: 1 year and 9 months
• weight: 141g (stable)
• symptoms: balding on bottom, end of spine, symmetrical. As time is going on, I'm seeing a bald spot on her middle back on each side. Yesterday looked at her and it seemed like her hair was thinning at the back of the neck.
• water intake: normal
• activity levels: normal
• pee and poop: normal
• cage: bottom cage

Poppy

• age: 1 and 3 months (estimated)
• weight: 153g (stable)
• symptoms: balding on bottom, end of spine, asymmetrical. One side has more balding them the other.
• water intake: normal
• activity levels: normal
• pee and poop: normal
• cage: top cage

On 10/07/2024 I noticed Maddie had 2 balding spots on each side of her bottom, at the end of the spine. I booked a vet visit at my local exotic vet and the vet told us that she appears to have a case of Demodex mites (no skin scrapping done). The vet applied 9 drops of Invermectin to the back of her neck and said that, since we caught this so early (very little balding), that she didn't think she would need more Invermectin. I was told to wait 2 to 4 weeks to see if the fur had grown back.

A bit more than 2 weeks later, on the 27/07/2024, I noticed that my other hamster Poppy was getting bald spots on the same areas as Maddie. She just had one area bigger than the other. I took her to the same exotics vet but she was seen by a different professional. This vet diagnosed her with mites (no tests done) and recommended 3 treatments of Invermectin every 2 weeks at the back of the neck, for both Poppy and Maddie.

While this was happening, I had noticed that there were book lice on both of their cages. I had seen one or two book lice with my past hamster Vanilla and knew they were harmless but this time I was seeing a bigger quantity of them so, after the treatment for both my hamsters yielded no results, I took Maddie to the vet again (03/09/2024) and told the vet about everything I did and these lice.

She told me that, in all her years of career, she only saw allergy to book lice once, in a cat. She doesn't think it's a coincidence that they are both getting bald at the same time, and thinks it has to be something in the environment causing this. She did consider Cushings for Maddie but doesn't think just the balding is enough to really consider it. So her current theory is:

• They're both allergic to book lice
• Maddie got book lice first and the balding started
• Then, because the cages are stacked, the book lice travelled up to Poppy's cage
• Poppy then started balding

So her course of treatment is the following:

• Deep clean both cages, disinfecting the cages inside and out
• Remove and disinfect all toys, houses, etc
• Remove all the bedding and put it in the bin
• With clean and empty cages, add new bedding (~15cm height, so it's easier to clean)
• Add back the toys, houses, etc
• No herbs or sprays
• Apply the Invermectin treatment on both (a total of 2 treatments, every 2 weeks)
• Deep clean weekly (removing peed on bedding, replacing with new, etc)

Yesterday was the start of the treatment and I did all these steps, for both hamsters.

I went through all my notes and the only thing that changed prior to them getting these symptoms, was that I changed my deep cleans to be once every month and a half instead of every month. That could link well with the book lice: more humidity because of wet bedding, they appeared. I feel extremely guilty... I only changed the regimen because I couldn't smell pee when I was doing it every month, since the aspen shavings are much more absorbent that my previous bedding, Teabag bedding.

I'm quite worried about them, specially Maddie since her balding is symmetrical and I read that that could be Cushings or an hormonal problem.

Does this plan sound right to you?
Have you had any hamsters going through similar symptoms?
They're healthy otherwise, it's just the balding. I do health checks on them both weekly.

Thank you for reading, I know it was a long post