Bleeding from the rectal area in a Westie can be attributable to several different things, so it is important that you have your boy checked out by your vet as soon as you can to determine exactly what it may be. The fact that your Westie is young one increases the chances that your pet may be suffering from an infectious agent many times over, so this symptom is nothing to ignore!!
Anal sac infections can cause fresh blood in the stool. The anal sacs are located at 4 & 8 o'clock just within the rectal opening and secrete a potent scent each and every time your pet defecates, marks his territory, becomes excited or stimulated. Should these glands become distended or blocked, than they can "fester" and cause straining to defecate due to discomfort. Your puppy is a bit young to have developed any type of anal sac infection, but in this business, I never say never anymore!!
For more info on Anal Sac Disease, please read the following link:
Fresh blood in the stool in puppies can also be a sign that your pet is straining to pass some type of foreign material in the stools such as bones, rawhides, plastic, mulch....whatever a Westie pup may decide to ingest on any given day!! Please watch the stools closely to see if you can visually see any type of foreign material within the feces. If you can think of any type of material that he has ingested in the last few days or any abrasive products that you have given him, this may be the culprit.
Another source of fresh bleeding into the stool, especially in young pups, would be parasites, such as Whipworms or Giardia or Coccidia. Hopefully, your Westie has had routine fecal exams for parasites, and has been started on Heartworm Preventive monthly, but if he has not, than intestinal parasites could definitely be the source of the problem.
Lastly, and of greatest concern would be the onset or clinical symptoms of PARVO VIRUS in your young pup. Parvo can be fatal in young puppies and must be treated aggressively and EARLY on it's course to insure the best prognosis for recovery. Most parvo puppies show other signs in conjunction with blood in the feces, like depression, vomiting, inappetance, and diarrhea.
With this said, it is very important that your Westie have a complete physical examinanation, a Parvo test exam, and a fecal analysis to rule out each of these problems and to direct therapeutic options!
I hope you found this information helpful and supportive. Please remember to PRESS ACCEPT so that I can be compensated for my time and professional attention to your question and your pet's specific needs. I appreciate all feedback and any type of bonus!!
Best wishes to you and your pet!!
Dr. Jodi Lynn Smith