My Jack Russell is not being responsive like he used to

Question
Hello I have a 5 month JRT that we got about a month ago and when we first got him he was all over the place full of energy. running around the house, playing with his ball interacting with us, chasing after me up and down the stairs and today we noticed that he's a little different not responding to anything at all!! all he wants to do is lie down and sleep. almost acting like he's depressed wondering what's wrong with him?

Answer
Hi Sandro,
It could be any number of things ranging from dehydration, to Lyme disease, or heartworm, or anything!! Make sure he is drinking water and call the vet to have him looked at right away. He may have eaten something that is making him sick... there are just too many things it could be which a stool and blood test could diagnose in minutes, please take him as soon as you can. When they are this little and young, they can go downhill fast, so act quickly. It's not in their nature to be lethargic, something is going on, call the vet!
Best of luck with your little guy.