Canine Behavior/Dog suddenly afraid of being picked up
Me and my fiancee about a year ago rescued a chihuahua from a local shelter and up until recently have had minimal problems with her. She has always been a slight bit skittish but for the most part is pretty outgoing and very friendly with people and dogs alike.
When we adopted her, she was just coming off medication for a UTI and had cleared up when we adopted her. She has had some issues with going to the bathroom in the house but we have been addressing the issue with our vet. She still has some bladder control problems due to crystallization in urine but we have her on a new diet as of today to address this. She has not appeared to be in any pain and her behavior had been normal until yesterday.
I left the house yesterday for some errands and when I returned she was very scared and yelped when I tried to pick her up. Usually she cowers a little when getting picked up but is OK with it and wags her tail and gives kisses. We keep her in a kennel when we leave to prevent her from having any in house accidents and she has seemed to be OK with it. I opened her kennel and when she didn't come out (which was odd) that was when I tried to get her out and she yelped. She had done this once or twice before but I couldn't even touch her without her crying.
She got very lethargic and when I tried to take her outside to see if she had to use the bathroom she laid down and still wouldn't let me pick her up. I was able to get her into the kennel (she walked in on her own) and got her down to the vet. They checked her and she was fine and didn't yelp or anything while there. They took x-rays (mainly to check for bladder stones) and nothing popped out of why she would suddenly have that happen.
We brought her home last night and she seemed tired and we brought her to bed with us so we could keep an eye on her. I was able to pick her up to take her outside this morning and she was OK with that but when trying to put her in her kennel, she snapped at me and ran under the bed and got skittish again.
At this point I don't know what to do. Nothing environmental has changed and the other dog in the house is his normal self. She is eating and drinking normally and the vet is at a loss for words of what is happening as well. Any help would be tremendously appreciated since this is very stressful and I hate seeing her in pain and scared.
Get rid of the crate. She may have injured herself while in it, or something may have occurred while she was in it, and it is of absolutely no use now and, in fact, is causing a serious problem. A friendly dog that suddenly turns to bite is reacting to a strong conditioned fear response.
Do not pick up this dog routinely. This is a very dominant thing to do and right now your bigger problem is the aggressive response: you must not do anything to provoke further aggression. As you describe you "couldn't even touch her without her crying", it's obvious she did sustain some sort of injury (orthopedic) or strong emotional response. She "snapped" at you while you attempted to put her into the crate and then ran. Crate is now a place she fears; she will very soon begin to fear you if you physically force her to use it.
Instead of a crate, take her to a local pet supply store and purchase "panties" and "pads" to go with them. She will need to be fitted to this, that's why you are better off taking her with you. Wearing this garment (almost impossible to get out of) eliminates the need for a crate and will stop her from urinating indoors. However, some of the prescription diets intended to assist with UTIs can, and do, increase urination, so if you notice this stop using that diet. The lower the phosphorous content of the dog food, the better it is to prevent UTIs. My Toy Poodle also has crystals in her urine and has been treated for two UTIs; the prescription food was a disaster. I am feeding her Nutro Ultra, it has .6% phosphorous (lowest on the market) and so far so good.
The "lethargy" you describe sounds more like abject submission to me. If a dog lies down and refuses to move, this is part of the fight/flight/freeze response, it is not lethargy. If you force a dog out of this behavior (where little cognition is engaged, this is an autonomic reaction to threat), you will then create an aggressive response (as you described) coupled with flight and what is called "cognitive dissonance" will occur. This results in a dog that has learned its natural behaviors intended, in its culture, to signal submission and non-threat DO NOT WORK (caps are used for emphasis, not shouting) and the dog then must revert to outright offense or escape. THIS you do NOT want.
Put a very lightweight leash on her (using a body harness) when you are at home. If you need to "catch" her for any reason, pick up the leash and lead her with you. If she lies down, sit down and turn away from her and wait for her to come to you. Quietly praise, get up slowly, lead her again. What we are doing is quickly counter conditioning a flight response before it is "set" and becomes a very serious behavior problem.
Do not approach this dog directly (eye to eye from across the room in a straight line). Approach her on a curve and, as you do this, turn your gaze away and speak to her calmly and quietly. As mentioned above, scoot down slowly and pick up the tab (if you want to lead her somewhere) or simply scoot down, give her a scratch under the chin, praise, get up and walk away. Let's change her reaction to your physical approach since she appears to have rapidly acquired a fear response. Also, it is far better that she (and your other dog) sleep in your bedroom than in isolation. The more confidence she feels in her "place" in your social hierarchy, the less likely she is to develop a serious fear related problem toward you.
Use followup feature please and report back to me in one week. TY.