eline retroviral infections cause the most disease- related deaths in domestic cats. Feline Leukemia virus and related disorders are presented at veterinary hospitals on a regular basis. The myriad of associated disease states involve almost every organ system. Feline leukemia becomes a differential for almost any sick, depressed, doing-anything-unusual cat. With the improved accuracy and ease of obtaining laboratory confirmation of FeLV infections, the FeLV positive cat is more frequently identified. Most hospitals have some protocol for these cats, which ranges from recommending euthanasia to a full line of supportive therapy. Unfortunately, the prognosis for FeLV-positive, clinically ill cats has never been encouraging. The survival rate in our Cincinnati, Ohio, clinic was less than 5%, but that was before we changed our protocol. In February 1984, a drug distributor introduced me to Immunoregulin (Immunovet).

and made a statement half way between a claim and a disclaimer for its application for FeLV- positive cats. The principal behind Immunoregulin is to stimulate whatever immune competency an animal may still carry to fight off foreign agents. Since I had been only able to delay temporarily the death of these cats, I decided to try this product, not really expecting any results. This article is my findings on the use of immunoregulin as an aid to immunosuppressive conditions in cats, specifically FeLV. The article will remain clinical opinion. Although our practice is computerized, our software does not generate data-base information, so I cannot put together exact percentages and have never set up any controls. We do have a large client volume (nine small animal veterinarians), and have used Immunoregulin in 700 cats. I feel that this "volume of opinion" warrants merit. Cats responded well

Immediately upon adding Immunoregulin to our protocol, it was obvious that some cats responded positively. Appetites improved. Cats went home. They gained weight. There are so many different associated FeLV diseases that it is difficult to describe specific responses, but your typical anemic, anorectic, debilitated cats responded and the responses were permanent in many cases. More specifically, approximately 50% of all cats present that were symptomatic and FeLV positive, responded in some way to Immunoregulin. We generally hospitalize a symptomatic cat for 10 days and begin our treatment with IV injection of ½ ml every third day for four doses. During those 10 days the cat’s fate becomes apparent. Regardless of all other supportive therapy, these cats will either respond, begin to eat, show an improved attitude, regenerate red blood cells or show absolutely no response. Little gray area exists. I have heard many reasons as to why one responds and not

another, and some ideas why some cats are better candidates than others. But in my opinion I have seen no patterns except for two. Lymphosarcoma and other FeLV-associated tumors seem to be totally unresponsive; therefore, any cat with tumors is considered a poor candidate. Also, vomiting associated with a positive FeLV test has consistently been a non-responsive condition. Of course, one cause of vomiting in FeLV cats is lymphosarcoma, often not discovered until necropsy. But I am not sure I have ever seen a vomiting FeLV positive cat survive. Otherwise, regardless of the degree of anemia, dehydration, emaciation (some cats even collapsed on presentation), I consider all candidates for Immunoregulin. On the other side, moderately ill cats are not better candidates. It seems some have enough immune competence to respond others do not. I do not find other supportive measures (IV fluids, transfusion, forced feeding, etc.) to influence the outcome. I usually include some broad-spectrum antibiotic. Improvement comes quickly From the initiation of the program, it takes three to four days to see improvement. Therefore, if a cat is badly dehydrated or anemic, we will correct immediate problems. Even a cat severely anemic but stable will not be transfused (I don’t feel it is contraindicated, but I do believe that an immune response is really the bottom line to survival).

The cats (50%) that show clinical response are released and followed-up with a weekly physical exam (no other bloodwork usually) and another dose of Immunoregulin for a period of four weeks minimum. This is done weekly for as long as it takes to return to normal body weight, PCV or relief of other clinical signs. The average weekly follow-up in this practice probably runs six weeks. Side effects are low Side effects from Immunoregulin are minimal. Local reactions will occur if the drug is not given IV, and swelling is observed at the site if some perivascular infusion occurs. Of the cats that receive four to 10 weekly follow-ups and are doing well (probably clinically normal), 90% are never treated again for any FeLV-associated disease. A few relapses have been seen and were restarted on Immunoregulin at weekly intervals for four to six weeks. Most have responded. The number one reason a cat returns is for FeLV associated tumors, and these usually are non-responsive to any therapy. The usual time for relapse or associated tumors is four to eight months. Cats that get past the eight-month period are seldom ever presented with FeLV associated disease again. One other factor to consider is that seroconversion is not a response that we often see. Along with this, I do not really advocate treating non-symptomatic FeLV positive

cats. Admittedly, some of these will become symptomatic, but I cannot justify its use in these conditions, primarily because most will remain FeLV positive. I believe that waiting until the occasional carrier becomes symptomatic and then treating will not adversely affect the survival rate of these cats. It will also keep from putting a chronic carrier through a therapy that will not help seroconversion. The proponents for treating these non-symptomatic positives make the point that we know that a certain percentage of these cats will show up later with FeLV associated diseases. They also say that by vaccinating and using an immunostimulant could head off that crisis. Technically, that reasoning seems sound, but I have a problem applying that to private practice. Primarily because of the low percentage of seroconversion, ELISA rechecks of treated cats is not part of our protocol. These cats, although clinically normal, should be considered potentially infective, especially owing to the nature of retroviruses to begin with. In summary, I have clearly been impressed with the response from adding Immunoregulin to our FeLV-positive cat protocol and that I have seen no adverse drug reactions. For practicing veterinarians, I recommend you try Immunoregulin in at least 10 cats to satisfy yourself that the

Page 2

drug does or does not improve the survival rate of FeLV-positive cats. The concept of adding an immune stimulant to a condition of immune suppression seems logical, and that is how I justify its use. Primarily, I recommend the protocol based on the number of cats that have returned home to lead normal lives. I should say that I have never heard any independent research facility or university researcher say anything except that it does not help. It is no

approved for use in cats at this time, nor is it restricted. However, I do believe the clinical data accumulated both at our clinic and from others using Immunoregulin around the country should compel the research community to investigate more comprehensively the role Immunoregulin may play in assisting immune competence for viral suppressive disease. I would be glad to offer assistance in an investigation of Immunoregulin.

Editor’s Note: Veterinary Forum invites letters for publication from other practitioners and the academic community on this topic. _________________________ Dr. Lies (OSU 1980) practices small animal medicine at Colerain Animal Clinic, Cinn., Ohio, 513-923-4400

Page 3