Found a field mouse

Question
Hello...
I'm writing to you, because I'd like some advice.
Yesterday, while we were entering the parking lot we saw something on the ground. As we approached we saw it was a mouse, just sitting there in the flashlights, not moving, all curled in(furball position) and not trying to escape or anything. I even petted its back and it was just sitting and breathing, like in a trance or something of a sort. Then I took it on my sleeves and he/she just curled even more and went to sleep. Initially his eyes were closed, but then when we got upstairs(we fixed him a temporary home in one of my guineapigs older cages, with bedding, lots of hay for him to nest/accommodate, water, a slice of carrot and some wheaty snacks from my guineapiggie's ''stash''.
The night has passed and in the morning we saw that he is still breathing, but he's barely moving, as if he's hibernating or something. He didn't eat, the food was untouched, and doesn't wanna leave his ''burrow''.

I've never had mice before, moreover field mice...and I don't know what's the situation. I asked my bf if we should take him to the vet, but he said that in the NEtherlands(where we are), they don't quite pay attention to such small creatures, from the wild. So, that saddened me and that's why I am seeking for your help.
Today I petted it a bit on the back(again, no problem), I palpated his body gently, to see if he has any pain(I was thinking that maybe he fell or something) and when I tried to pick him up he bit me(didn't pierce the skin...it was just a reflex I suppose).
My bf said that's quite peculiar at mice, since they're not aggressive, more like...they pee in your hand or try to make a run for it...but not this one. I'm worried about the little creature.
I'd like to know how to care for it and what are the diseases they can have and also if they can spread diseases to other creatures(my guineapigs) and to humans. He is in a different cage/different room than my guineapigs, so I'm thinking if the illness(if he/she has it) has to be airborn or something...

I hope you can help!

Best wishes from the NL,
Angelica

Answer
Dear Angelica,

First of all, thank you so much for caring about this little mouse.  I'm surprised that in the Netherlands mice aren't more liked, since they are much beloved in Germany, where I used to live.

Mice in the wild are certainly aggressive if they are threatened.  If this mouse was well, it would have bit you hard long ago.  Because it's sick, it may trust you, and the nip may have been gentle on purpose.  If this little guy survives, s/he might make a sweet pet.  Some animals understand being rescued by humans.

Although mice don't actually carry the number of zoonotic diseases that people think, it is still possible that the mouse has mites that the guinea pigs could get. I doubt this but it's certainly worth taking precautions.  Don't let the animals have direct contact with each other, wash your hands between holding them, and don't put them on the same surfaces.  As for human diseases, this is very rare.  There is an air-borne disease called hantavirus, which is transmitted through dried feces and urine, which people who clean out old barns and houses can sometimes get.  There are about 13 cases a year in the United States. Let's see what I find about the Netherlands...

From 1995:  "A serological survey for the prevalence of hantavirus infections in The Netherlands... Among individuals with a suspected occupational risk, 6% of animal trappers, 4% of forestry workers, 2% of laboratory workers and 0.4% of farmers were seropositive. The majority of the seropositive individuals lived in rural and forested areas. The main animal reservoir of the infection was shown to be the red bank vole (Clethrionomys glareolus)."
http://www.jstor.org/pss/3864250

Also in 2006 "A 12-year-old girl and a 57-year-old woman were admitted with fever, general malaise, abdominal pain, nausea and vomiting," which are the symptoms of the disease. Basically if you come down with a really nasty flu within 2-4 weeks of contact with wild mice, you should tell your doctor about it.  Because these are the only reports I found, it sounds like it doesn't happen very often where you are.

To care for the mouse, make sure it stays warm- a light near the cage or a hot water bottle or heating pad are good.  Try to get some calories into it-- give it butter, commercial peanut butter, nuts, seeds, and anything else it will eat. It may lick butter from your fingers.  It is important that it ingest some water.  Use an eyedropper, a syringe (no needle!), or even a bit of paper towel dipped in water, to try to get it to take it. Be sure not to give it too much water at once, or it will come out its nose.  

I wish your little foundling the best of luck.  Don't blame yourself if it doesn't make it-- it sounds pretty sick.  Let me know how it goes!

squeaks,

Natasha