lama having skin crusts - mites not healing with treatment since two years

To the MITES issue I was reading already the older postes in the forum and some books, and i am not sure what to do in case of my white Lama Dana, he has crubs and skin irriation since two years and it does not heal or get any better with our treatment.
My vet treated Dana the last two years in sommer with dectomax injecions for three times after each 14 days . but the leathery red crusty skin of Dana stayed the same than before the treatment, just some more hairs where growing and it seems to hitch him less,Dana got less nervous after the treatment.

Dana has leathery crusts on the ears inside and outside, around the anus and under the tail, and large irritated crusty and red areas downside on his belly,foreskin and inside alle the four upper legs.
and also some round wet spots on the face ( thsi maybe a mushrooms says me vet.)

I send you here some photos of Danas skin

I also refer to your answer to me in the tapeworm thread.
Dr Nancy Richards . if you have mites, their are two treatments that could be considered. It may take both, depending upon what species of mites you may be dealing with. Sucking mites, require invermectin, whereas biting lice, require fipronil. 1. Treat with Ivermectin injectable, subcutaneously (under the skin), at a dose of 200-400 mcg/kg, repeating in 14 days, and 2. Treat topically with Fipronil spray on the lower legs and other affected areas, repeating every 21 days for a 5 treatment minimum. If their are secondary bacterial infections, those may need to be addressed with an antiseptic applied topically as well as skin conditioners. Your vet may be able to help you diagnose which you have by doing a skin scraping.

I gave Dana some extra zink but he does not eat it for too longtime.

I did not spray him on the skin with anything. my vet did not recommend it, because Frontline Products are having a very bad reoutatoin in Germany to cause pain inside the animals system. But maybe we should do something more locally..

This year in the second summer also two other llamas having got the same crusty and hitching skin just in lesser amount. so the infection is spreading out and this conerns me.
Ine Lllama got healing after one dectomax injecion -but the other Lama after two Decotmax injecion still had the same crusts under his fleece on the back
I am concerned that the symtoms may spread to all of the herd of 6 llamas- if I cannot really heal Danas skin .

My vet did not take a skin scraping, we tryed it- but Dana escaped him inside the catch pen like running from hell away form the scalpell and the vet did not want to hurt Dana too much . -so it is not proofed that Dana really has mites. but whatelse can it be ?
how do you handle a llama in camelidynamics way to take skin scratches from him ?

Maybe it would be a good idea how you write in another post it to wash his skin with jod water.
also not so easy to do.. Are your sure this will help in our case?
to wash the whole skin is quite an effort--. How can i wash a Lama downside on the belly??, how can touch him there?? how do you do it in camelidynamics- wont he refuse the washing and or kick ??

My vets means to use some coconut oil to soften the skin, what do you think of that option?

Is it reasonable and does it help to desinfect the whole barn and floor and equipment with hot steam pressure cleaner and hot water and chemical desinfections . ( thus written in the US book lama and alpaka care ) . OMG, also a lot of effort and chemical substances around and it is never guaranteed to reach every mite...

My vet means that is is normal to leive with a certai amount oa mites on animals and it is more to limit them and not very likely to get ridd of them totally , is this true?

I am not happy with this skin problems and i would like to reall get them healing.

So my question ist what treatments can we add and what is realistic to help Dana?