Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now the dilemma here is that it sounds like your lass may have chronic GI issues and this means that we have to consider that the weight loss and recent appearance of blood (often a sign of colonic irritation that can be seen with colitis, some parasite infections, or can just be secondary to profuse diarrhea for other reasons) could be linked to this or could be due to another more sudden onset reason. Furthermore, as I am sure you can appreciate, just like people, diarrhea in cats can be caused by a wide range of causative agents. This includes bacteria, viruses, parasites (GI worms and the protozoa like coccidia, giardia and also cryptosporidia, tritrichomonas), cancer (ie GI lymphoma --a concern if she is older), inflammatory disease (ie IBD), nutritional sensitivities, stress, and toxins (the last two hopefully less likely). So, it can be a daunting situation to tackle.
Still there are some steps you can take at this stage to see if you can slow the diarrhea (and hopefully the weight loss if its being triggered by the nutrition and protein loss diarrhea will have caused her over this time frame). To start, since she is keen to eat/drink and otherwise well in herself, I would suggest a trial on light/easily digestible diet. Examples of this would be boiled chicken, boiled white fish, scrambled eggs (made with water and not milk), meat baby food (do avoid the ones with garlic powder in the ingredients) or there are also veterinary prescription diets that can be used in cases like this (ie Hill’s I/D or Royal Canin’s sensitivity). This should be fed as small frequent meals. Our aim with this type of diet approach is that it will be easy for the compromised gut to digest, which means more nutrition into the cat and less material left in the gut to become diarrhea.
After you have put her on an easily digestible diet, then next step is to rule out GI worms (which would be ideal if this wasn't done when she came from that dodgy home). To rule these critters out, we'd want to use a good quality broad spectrum. There are many available OTC at your vet's or at your local pet stores but you'd want to make sure to use a good quality wormer that covers both round worms and tapeworms. In this situation, it would be ideal for you to treat your lass with Panacur, Drontal, or Milbemax as it will cover all the worms in question. Do make sure to have an idea of her weight before purchase wormer to make sure you get the correct dose for her size.
Now, if a cat has diarrhea, we do have an extra complication to consider. Specifically, we have to monitor for dehydration since she will be losing abnormal volumes of fluid in her loose stool (and often dehydration is what makes them feel poorly). Therefore, you do need to keep an eye on her water intake. To check her hydration status to make sure she is not becoming dehydrated there are a few things we can test at home. One is whether the eyes appear sunken, if the gums are tacky instead of wet/moist, and whether she has a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a wee video on this (HERE). They use a big dog but it makes it easier to see and the principles are exactly the same. If you are seeing any signs of dehydration already, then you do want to have your kitty seen by her vet before this gets out of control.
In regards XXXXX XXXXX you can do to help stave off dehydration at home (though do note that if she is already then she will likely need more the oral rehydration), encourage her to drink but offering fresh water or even low-sodium chicken broth. If she isn't amenable to drinking, you may wish to offer unflavored pedialyte via syringe feeding. A typical maintenance rate for hydration in an animal 48mls per kilogram of her body weight a day. If you do give syringe pedialyte, this should obviously be divided up into multiple offerings through the day rather then all at once. This value will give you the total she needs for the day and is a good starting point to give you an idea of her daily requirement (though we'd have to add in an equivalent amount to match her diarrhea losses as well). If she does vomits when you give pedialyte, I would discontinue this as a therapy. (since we don’t want vomiting because of our intervention).
Further to this, if a cat has diarrhea just due to benign GI upset, the above is usually enough to settle it for them. But sometimes we need to use feline safe anti-diarrheals to slow things down for their gut. As I am sure you appreciate, these would not be a cure (since cures would depend on the culprit and might include antibiotics or anti-parasitics, etc.) but would slow the diarrhea to aid the body potentially absorb more water/nutrients then it would have if the diarrhea were unchecked. In regards XXXXX XXXXX options for her the one we most commonly use in cats is Kaolin (More Info/Dose) available from your local pharmacy (do avoid using any PeptoBismol or similar products with aspirin in them) or Protexin Pro-Fiber (which is available OTC at vet practices; example). Both will slow diarrhea safely for a cat and the Pro-Fiber has the bonus of providing support to the delicate good bacteria of the GI.
Furthermore, you can also supplement her with a probiotic to try and restore the normal GI microflora (a consideration for a cat with chronic issues). One preparation we often use is FortiFlora for Cats (LINK). This produce is quite good for kitties with diarrhea from GI disturbance and will also give her a wee immune system boost. Some vets and pet stores carry it or you can get it online.
Overall, diarrhea can be caused by a wide range of agents. If she is otherwise well in herself, properly hydrated, and eating/drinking; then you can try supportive care to see if you can settle the signs at home. If you try the above and the diarrhea isn’t settling, then we'd have to consider more sinister causes for her diarrhea. In that case, that would be a good point to consider following up with her vet. Ideally, you could submit a fresh fecal sample to the vet for testing. Depending on the fecal test findings and your vet's exam, your vet will be able to advise you of the cause and guide you on effectively targeting treatment against the causative agent to settle this diarrhea for her.
I hope this information is helpful.
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All the best,
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