February 2004

Internal Medicine @ Feline Focus

Alice M. Wolf, DVM, DACVIM, ABVP (Feline Practice)

Department of Small Animal Med/Surg, Texas A&M; University



Practical Stuff From ACVIM © 2004

Comparison of the Pharmacokinetics and Pharmacodynamics of Glargine, Protamine Zinc, and Porcine Lente Insulins in Normal Cats. - RD Marshall, et al. U Queensland, Australia

Because of the difficulties in insulin administration and regulation in some diabetic cats, there is considerable interest in glargine (Lantus®- Aventis) insulin. Glargine is marketed as "peakless" insulin and is given once daily in humans. This study was undertaken as a preliminary evaluation of glargine insulin in normal cats. Subjects were 9, healthy, neutered adult cats, 5 male, 4 female. Insulin of each type was administered as a single SQ injection at a dose of 0.5 U/kg. Blood glucose and insulin measurements were performed hourly for 24 hours post-injection. 3 days elapsed between each trial. There was no significant difference in time to onset among the 3 insulins. Time to reach glucose nadir was longer for glargine (16± 1.9 hours) than for PZI (6±2.3) or Lente (4±0.5). The glucose nadir was not significantly different among the insulins. Time for glucose to return to baseline was significantly shorter for Lente than for PZI or glargine. Conclusions: Glargine insulin produces a later glucose nadir than PZI or Lente and has a longer duration of activity than Lente. Apparently, unlike humans, in cats there are definite peaks of insulin activity comparable to other insulin types.

Comparison of the Pharmacokinetics and Pharmacydynamics of Once versus Twice Daily Administration of Insulin Glargine in Normal Cats. - RD Marshall, et al. U Queensland, Australia

This study performed by the same authors as above used 6 cats (3 each male and female). Glargine insulin was given at 0.5 U/kg SQ q24h or 0.25 U/kg SQ q12h. Conclusions: Both regimens produced a significant blood glucose lowering effect. The duration of glucose suppression was much longer with q12h dosing. In 33% of cats treated q12h, blood glucose concentrations were still suppressed at 24 hours which might produce a "piggybacking" effect during long term therapy. Further study is needed to determine the utility of glargine insulin in cats with naturally-occurring diabetes mellitus. Ed. Note: Information from the product literature indicates that glargine may produce more pain at the site of injection. It is available as 100 U/ml strength in 5 and 10 ml vials. If refrigerated, glargine should be used within 28 days of opening.

Parenteral Administration of FVRCP Vaccines Induces Antibodies Against Feline Renal Tissues. - MR Lappin, CSU

CRF often associated with lymphoplasmacytic interstitial nephritis (suggestive of immune-mediated disease) is a common cause of morbidity and mortality in older cats. Viruses used in feline FVRCP vaccines are commonly grown in Crandall-Reese Feline Kidney (CRFK) cells. Vaccines produced from these viral cultures will contain CRFK antigens. This study was undertaken to determine whether CRFK antigens in vaccines would stimulate antibody against feline renal tissue. 14 unvaccinated kittens were divided into 7 pairs. Treatments included: 10 µg CRFK protein SQ, 50 µg CRFK protein SQ, 50 µg CRFK protein + aluminum adjuvant SQ, IN feline FVRCP, or one of 3 commercial FVRCP vaccines SQ. The concentrations of CRFK proteins was comparable to those determined to be present in vaccines. CRFK proteins were given every 2-4 weeks for a total of 8 injections. FVRCP vaccines were given every 3 weeks for a total of 3 inoculations (typical vaccination series). Serum samples were collected prior to treatment and 6 months later. None of the cats was positive for antibody against CRFK or feline renal tissue (FRT) prior to inoculation. Six months post-inoculation, 6/6 kittens inoculated with CRFK had anti-CRFK antibody, 5/6 also had anti-FRT antibody. 5/6 vaccinated kittens had anti-CRFK antibody, 4/6 had anti-CRFK antibody. Neither of the IN vaccinated kittens had anti-CRFK or anti-FRT antibody. Conclusion: Administration of parenteral FVRCP vaccines SQ can induce anti-FRT antibodies which may play a role in the development of chronic progressive renal disease later in life. Further study is needed but this may be yet another reason to limit vaccination to what is absolutely necessary in cats.

Feline antibody response to Fort Dodge Fel-O-Vax FIV vaccine interferes with FIV diagnostic tests. - R Groat, et al: IDEXX Diagnostics

Subjects were 4 cats vaccinated with Fel-O-Vax FIV vaccine according to label directions. Blood samples were collected for assessment of the presence of anti-FIV antibody (positive "FIV test") prior to vaccination, at 28 days, 4, 7, and 13 months after completing the vaccination series. Samples were tested with the IDEXX Snap-Combo (FeLV and FIV), PetCheck FIV, and Western blot. All pre-vaccination samples were negative for anti-FIV antibody. All samples taken from 28 days to 13 months post vaccination were strongly positive for FIV antibody. Conclusions: It is impossible to distinguish antibody generated by FD FIV vaccine from AB generated by naturally-acquired FIV infection on the basis of presently available tests for at least 13 months.

Infectious organisms in feline chronic rhinosinusitis. Correlation of rhinoscopic findings with nasal biopsy in cats. LR Johnson, et al: U.C. Davis

Subjects included 10 cats with chronic Mucopurulent nasal discharge with a duration of signs from 3-24 months. The control group consisted of 5 apparently normal cats without respiratory tract signs. Rhinoscopy, unilateral diagnostic nasal flush, and bilateral biopsy was performed on all cats. Samples were submitted for aerobic, anaerobic, mycoplasma cultures, histopathology, PCR for Herpesvirus, virus isolation for other viruses. Three of 5 asymptomatic cats were found to have aerobic bacteria present on culture. In the "snuffler" cats, aerobic bacteria were cultured in 9/10, anaerobic bacteria in 3/10, Mycoplasma in 2/10. FHV was not cultured from any cat. PCR for herpesvirus was positive in 3/10 (30%) of the snuffler cats and 3/5 (60%) of the normal asymptomatic cats. This indicates that herpesvirus is not an active participant in the chronic snuffler complex and that while detectable it does not appear to be viable on culture.

Forty-five cats were evaluated with rhinoscopy and biopsy. Biopsy specimens were scored on the gross appearance and on the severity of histologic lesions. The results demonstrated that samples with minimal histologic change usually had low gross appearance scores. Samples with moderate to severe inflammation also often had low gross scores. The gross appearance of the nasal mucosa as assessed during rhinoscopy is often misleading with respect to the actual severity of the disease seen on histopathology. Therefore, ALWAYS take biopsies as part of your nasal cavity diagnostic testing.

Clinical efficacy of transdermal methimazole in cats with hyperthyroidism. - LL Sartor et al. University of Wisconsin

Subjects were 44 cats with newly diagnosed feline hyperthyroidism. Both transdermal (27 cats) and oral (17 cats) treatment groups received a methimazole dose of 2.5 mg q12h. Evaluation of the cat by body weight, physical examination, CBC, biochemistry profile, UA, total T4, blood pressure and owner evaluation was performed pre-treatment (day 0), and 2, and 4 weeks into the treatment regimen. There were no significant differences in laboratory or physical assessments between groups prior to treatment. At 2 weeks, 86% of the orally treated group was euthyroid compared to 56% of the topical group. At 4 weeks the results were 82% and 67% respectively. There was not a significant difference between groups. Gastrointestinal side-effects were seen in 23.5% of the group treated with oral methimazole but only 3.7% of the cats treated with transdermal drug. There was no difference in the occurrence of leucopenia, hepatotoxicity, or facial excoriations between the groups. The conclusions to the study were that transdermal methimazole is effective, requires slightly longer induction time to reach euthyroid status, and is associated with fewer GI side-effect compared to orally administered drug. Topical methimazole is a viable treatment option.

Prevalence and risk of Tritrichomonas foetus in cattery cats. - JL Gookin, et al, NCSU.

A study of 119 cats in 89 catteries was performed. The prevalence of T. foetus was 31% for all cats and 31% of catteries. The prevalence of Giardia sp was 31% for cats and 35% for catteries. Co-infection with both T. foetus and Giardia was present in 12% of cats and 16% of catteries.

Outcome of cats with diarrhea and Tritrichomonas foetus. - DM Foster et al: NCSU

Subjects were 26 cats with large bowel diarrhea and confirmed TF infection. 22/26 cats had abnormal stools daily, 3/22 weekly and 1/22 monthly. Signs had been present for a median of 2.5 months (range: 0-24 mos). Clinical signs resolved in 23 cats, 4-24 months after the onset of diarrhea (median 9 months). Recurrent bouts of diarrhea were seen in 12/25 cats after initial improvement or resolution. Organisms were still detectable (fecal culture, PCR) in 60% of cats despite apparent resolution of clinical signs. Conclusions: Cats may experience spontaneous resolution of T. foetus associated diarrhea within 2 years of diagnosis. Infrequent recurrences of diarrhea may be triggered by diet change, stress, or medication.

Enrofloxacin for Treatment of Cats Experimentally Infected with Large Form Haemobartonella felis. - KL Dowers, et al. CSU

Haemobartonella has recently been reclassified as a Mycoplasma. The large (pathogenic) variant now carries the name Mycoplasma haemofelis (Hflg). 16 cats were experimentally infected with Hflg and divided into 4 treatment groups: Doxycycline 5 mg/kg PO q12h, Enrofloxacin 5 mg/kg PO q24h, Enrofloxacin 10 mg/kg PO q24h, and an untreated control group. Clinical signs, PCV, blood smears, and PCR were used to monitor the cats. Cats PCR negative at 8 weeks were given methylprednisolone (20 mg/kg IM weekly) for 3 weeks and were evaluated weekly, then 6 months later for recurrence. All cats were positive for Hflg by PCR and blood smears following infection. During treatment, organism counts for the doxycycline treated group and 10 mg/kg Enro group decreased faster than those in the control group. Treatment had no effect on the PCV during the treatment period, however PCVs were higher in the Enro5 group compared to the control group after treatment. There was no significant effect of any treatment on the number of PCR positive results (cats still infected). 3 cats (1 doxy, 2 Enro 10) were persistently PCR negative even following methylprednisolone challenge. Conclusions: Enrofloxacin was as effective as doxycycline in the treatment haemobartonellosis in cats. Ed Note: The 10 mg/kg dose is higher than recommended and concern for ocular effects may limit its use at this dosage. Trials with other quinolones have not yet been performed.

Imidocarb diproprionate for the treatment of recurrent haemobartonellosis in cats - MR Lappin, CSU.

Subjects were 5 cats with treatment resistant haemobartonellosis. Two cats were infected with the large form: M. haemofelis, two with the small form: M. haemominutum, and one was not identified (cytologic diagnosis only). Previous failed treatments had included doxycycline and prednisone (2 cats), Doxy, Enro, and pred (1 cat), Doxy, Tetra, Enro, and Pred (1 cat), and Doxy, Enro, Chloro, Pred in one cat. Imidocarb was used as a sole agent or added to the failing protocol at a dose of 5 mg/kg IM. This treatment was repeated in 14 days as needed. One cat responsed to a single dose of imidocarb, one responded to 2 doses and both are normal after 9-14 months. Two cats required 4 doses (at 2 week intervals) both were normal after 3-7 months. One cat requires monthly imidocarb injections to maintain a normal PCV (after 14 months). Conclusions: Imidocarb diproprionate is useful for the treatment of resistant hemobartonellosis in cats. Ed note: This drug is not approved for cats. Pre-treat with atropine IM, 30 minutes prior to drug administration.

Infectious Causes of Fever in Cats. - MR Lappin, et al. CSU

Serum samples were collected from 121 cats with fever. These were matched with 99 geographically matched cats without fever. Cat sera were evaluated for FeLV, FIV, FCoV (coronavirus), T. gondii, E. canis, E. equi, Haemobartonellosis (M. hemofelis, M. hemominutum), B. heneslae, B. clarridgeiae, Ehrlichia species (PCR). Results showed evidence of exposure to one or more infectious agent in 54% of cats with fever and 50% of cats without fever. Conclusions: Since each of the assays can be positive in cats with and without fever, causation of fever cannot be proven on the basis of a test result alone.

Treatment of Feline Leukemia Virus Infection with 3-azido-2,3-diedeozythymidine (AZT) and Human Alpha-Interferon (huIFN). - K Hartmann, et al. U Zurich, Switzerland

Subjects consisted of 44 cats naturally-infected with FeLV. These were randomly assigned to one of 4 treatment groups. Cats were treated for a period of 6 weeks with: AZT (5 mg/kg PO q12h), huIFN (100,000 IU/kg SQ q24h), AZT and huIFN, or placebo. Evaluation included clinical, laboratory, virological, and immunologic assessment. Evaluators were blinded regarding treatments cats were receiving. None of the cats became FeLV antigen negative during the treatment period. A trend toward general clinical improvement and improvement in some specific signs (e.g. stomatitis) occurred in treated cats, however, the improvement was not statistically significant. CD4+ and CD8+ cell counts did not change significantly. No synergy between drugs was observed. Most patients did not show side effects of treatment, however, on cats was withdrawn from the AZT group due to severe anemia developing on the 3rd week of treatment. Conclusions: Treatment with AZT and/or huIFN (SQ) did not produce significant improvement in clinical signs, laboratory findings, viral load, or immunologic parameters. A longer treatment period might produce better results, however, cats quickly (7-8 weeks) develop antibodies to huIFN given SQ and a longer treatment period with this agent may not be possible.

Relation of survival time and urinary protein excretion on cats with renal failure and/or hypertension. - HM Syme - RVC, London UK

The objective of this study was to investigate the relationship of proteinuria to survival time in cats with variable renal function and with or without systemic hypertension. The subjects were normal cats (USG > 1.035, normal chemistry), cats with PCRD (USG < 1.035, Cr > 1.9) and cats with hypertension (consistently > 175 mmHg). Outcome: Median survival time of cats with UPC > 0.43 = 281 days, survival of cats with UPC < 0.43 = 766 days. Conclusions: proteinuria predicts reduced survival time in cats with CPRD. Further studies with interventions that decrease proteinuria are warranted to see whether this strategy increases survival times.

Influence of proteinuria on survival time in cats with chronic renal insufficiency. - D Gunn-Moore, Edinburgh

Subjects of the study were 193 cats with chronic progressive renal disease. Subjects were divided into two treatment groups: control (placebo) and treatment with benazapril HCl 0.5 - 1.0 mg/kg PO q24h. Cats were followed for up to 3 years and assessed for progression of their renal disease. The mean survival time for the control group was 520 days compared to 637 days for the benazapril treatment group. This difference overall was not statistically significant. However, for the subgroup of cats with proteinuria (UPC > 1.0), benazapril significantly increased survival time. Therefore it may be useful for this subgroup of cats with proteinuric CPRD.

Efficacy of Giardia vaccination for treatment of giardiasis in cats. - JE Stein, CSU

Subjects were 16 young adult cats, male and female, negative for FeLV/FIV/Giardia. Cats were individually housed and infected with a human-derived Giardia strain. All cats became positive and shed oocysts but had minimal clinical signs. Eight of the cats were selected randomly and vaccinated at 4, 6, and 10 weeks post-infection with Fel-O-Vax Giardia vaccine. Three fecal samples were collected weekly for 28 weeks post-infection. At 28 weeks, 5/8 vaccinated cats and 7/8 control cats were still shedding oocysts. There was a general trend towards decreased oocyst shedding in all cats over time. The investigators concluded that Giardia vaccine was not effective in eliminating oocyst shedding in this model. There were minimal clinical signs in both treated and untreated cats. The efficacy of the Giardia vaccine as a treatment in naturally-infected cats remains to be determined.



Unusual Manifestations of Cancer in Cats© 2004

There are a number of recently recognized vascular and metabolic metastatic manifestations of pulmonary neoplasia in cats. These include the lung-digit syndrome (metastatic digital carcinoma), neuromuscular weakness, hypercalcemia of malignancy, arterial thromboembolism (ATE), and posterior ocular segment metastasis. Several of these syndromes may occur in the same animal. Vascular complications may occur due to direct invasion by the tumor, thrombocytosis secondary to neoplasia, metastatic showering to distant locations, and coagulopathy associated with neoplasia. This presentation will use case studies to illustrate some of the syndromes so that they will be come more recognizable for the practitioner.

AORTIC THROMBOEMBOLISM

The presentation for these patients with ATE secondary to pulmonary neoplasia is identical to that of cats with ATE associated with cardiac disease. Clinical signs include acute paresis of limbs or muscular pain. Limbs are cool to the touch, pulses are weak to the affected limbs, and gross lesions of infarction may be evident in the distal extremities. Nail beds and paw pads are often purple and bleeding is sluggish or absent when a claw is trimmed to the quick. Extreme pain due to muscle anoxia is often present. Pulmonary radiographs taken at the time of the initial thromboembolic event may or may not demonstrate an obvious pulmonary mass. Disseminated pulmonary neoplasia may be very diffuse and below the level of detection of plain film radiographs. Diagnostic evaluation is directed to confirming the diagnosis of ATE and ruling out cardiac causes for this event. Laboratory evaluation often reveals leukocytosis and markedly elevated CPK and AST levels. Renal function may be compromised if the thrombus involves the renal arteries. Treatment is directed at pain control and supportive care to assist restoration of arterial blood flow. The prognosis for ATE overall is poor and these patients have the additional problem of pulmonary neoplasia that will worsen over time.

METASTATIC DIGITAL CARCINOMA

Pulmonary neoplasms in the cat may have an unusual metastatic distribution pattern involving the terminal phalanx of the digits. One or more digits of the same or different limbs may be affected. The affected digits are swollen, warm, painful, and may have evidence of exudation at the nail bed or sloughing of the nail. Topical (e.g. soaks or ointments) and systemic therapies (e.g. antibiotics or corticosteroids) do not resolve the problem. Radiographs of the affected digit reveal lysis of the bone of the third phalanx that does not involve or cross the joint space. Radiographs of the thorax will reveal various patterns of pulmonary neoplasia. The affected digit(s) may be excised to help resolve pain, however, the primary pulmonary problem still exists and recurrence in other digits is possible. In addition, depending on the type and aggressive nature of the pulmonary lesion, signs of lung dysfunction (dyspnea, etc) may appear soon.

POSTERIOR OCULAR SEGMENT METASTASIS


Intraocular metastasis of feline bronchiogenic carcinoma causes an ischemic chorioretinopathy. Clinical signs may or may not be related to the eye. A thorough ophthalmoscopic evaluation should be performed in all cats with suspect pulmonary neoplasia in order to detect these lesions. No specific treatment for the ocular lesions is indicated unless pain is severe. The prognosis is poor because of the primary pulmonary involvement.

NEUROMUSCULAR WEAKNESS


Vasoinvasive pulmonary carcinomas may metastasize to the muscle or neurologic tissue and produce weakness associated with either primary neurologic damage or polymyopathy. Muscular involvement may result in pain on deep palpation. Neurologic lesions may produce a diffuse array of deficits depending on the distribution of the metastases. Although this is an unusual manifestation of pulmonary neoplasia, thoracic radiography to evaluate for this problem, should be recommended in cats with poorly defined neuromuscular weakness or neurologic signs.

HYPERCALCEMIA OF MALIGNANCY


Pulmonary neoplasms may occasionally be associated with pseudohyperparathyroidism in cats. The clinical signs relating to this condition may or may not be present. Renal failure is the most common sequel to prolonged hypercalcemia. Because hypercalcemia is often associated with malignancy, thoracic radiographs are indicated in a search for occult neoplastic lesions. The prognosis for affected cats is very poor because of the effects of hypercalcemia as well as the presence of primary pulmonary neoplasia.

This presentation will use case studies to demonstrate some of these various syndromes.

REFERENCES:
  1. Gottfried SD, Popovitch CA, Goldschmidt MH, et al: Metastatic digital carcinoma in the cat: A retrospective study of 36 cats. J Am Anim Hosp Assoc, 36:501-509, 2000.
  2. Hogan DF, Dhaliwal RS, Sisson DD, et al: Paraneoplastic thrombocytosis-induced systemic thromboembolism in a cat. J Am Anim Hosp Assoc. 35: 483-486, 1999.
  3. Cassotis NJ, Dubielzig RR, Gilger BC, et al: Angioinvasive pulmonary carcinoma with posterior segment metastasis in four cats. Vet Comp Ophthalmol 2:125-131, 1999.
  4. Anderson TE, Legendre AM, McEntee MM: Probably hypercalcemia of malignancy in a cat with bronchiogenic adenocarcinoma. J Am Anim Hosp Assoc , 36:52-55, 2000.
  5. Chauvet AE, Shelton GD, Dubielzig R, et al: Neuromuscular weakness as a primary clinical signs associated with metastatic neoplasia in two cats. Feline Pract, 25:6-9, 1997.



Zen and the Art of Cat Maintenance I & II © 2004

There is as much "art" as science in the practice of veterinary medicine generally, and in feline practice in particular. The following are some useful (I hope) thoughts gleaned from practical veterinary practice related to the feline species.

General:
  1. Less (restraint) is more when handling cats.
  2. If you develop a rapport with cat owners and with cats, you will rapidly develop a very loyal and enthusiastic clientele.... however, the reverse is also true.
  3. Tortie and calico cats have a "devil" gene.
  4. Many solid black cats have Siamese heritage. Kink at the end of the tail is a Siamese trait.
Musculoskeletal:
  1. Hip dysplasia is not uncommon in cats.
  2. ACL tears are more common in Abyssinian cats and are more common in cats with poor hip conformation. A "joint mouse" is often seen with ACL tears in cats.
  3. Medial luxation of the patella may also be associated with poor hip conformation and may be a congenital problem.
  4. Aseptic necrosis/spontaneous (non-traumatic) capital physeal fracture of one or both femoral head/necks occurs in young, usually male, overweight cats. May be confused with traumatic fracture. Both unilateral and bilateral disease occurs. One leg may be affected before the other.
  5. Most increases in CPK are due to anorexia in cats.
  6. Meloxicam (0.1 mg/kg x 4-5 days, then 0.1 mg (total dose) q24h) may be a useful and safe NSAID for cats.
Hemolymphatic system:
  1. Hemobartonellosis is a rare primary clinical disease and is over diagnosed by commercial veterinary laboratories. If your patient isn't anemic, even if the "FIA" is positive, look for some other primary problem. New names: Mycoplasma haemofelis, Mycoplasma haemominutum
  2. If you use a QBC machine, be sure to look at the cytology of the blood smear. Otherwise you may miss significant cellular abnormalities not detected by the machine.
  3. If an owner complains that their cat licks bricks, cement, eats kitty litter etc, the cat is probably anemic (no, I don't know why they do it but they do).
  4. Nucleated RBCs do not make an anemia responsive... be sure to check a reticulocyte count.
  5. Do a bone marrow if there is an abnormality in more than one cell line in the peripheral blood. If there are severe cytopenias, get a core sample for histopathology as well as one for cytologic examination.
  6. Be sure to save several unstained marrow slides for FeLV IFA when you do bone marrow aspirates.
  7. Neutropenia +- fever + chronic illness .... consider Toxoplasma. Do IgM titer for active disease.
  8. Some cats are more comfortable if you place them in lateral recumbency to draw blood from the jugular vein.
  9. Try Rutin therapy for idiopathic chylothorax: 50 mg/kg/PO q8h. Available at GNC and other health food stores.
Respiratory system:
  1. Cats have a very small tidal volume and it's very difficult to hear significant lung pathology until it is very severe. Watch breathing patterns as this will provide the most subtle clue to respiratory disease.
  2. Radiographs are your best first diagnostic tool for suspected respiratory abnormalities in cats. But use extreme caution in radiographing dyspneic cats.
  3. Severe dyspnea without major radiographic abnormalities suggests functional airway disease (eg asthma). Look for the airway "doughnuts". Another possible cause is pulmonary thromboembolism but this is RARE.
  4. Collapse of the right middle lung lobe in cats is a common sequel to any chronic lung disease.
  5. Evidence of a traumatic tracheal tear or rupture may not appear until several days to a week after the trauma.
  6. SQ emphysema (if not related to a sucking skin wound): Look for disruption in the trachea, pneumomediastinum.
  7. Bordetella infection in cats may cause an URI syndrome with nasal and ocular discharge and coughing but it is not a common disease of cats.
Dermatology:
  1. Don't forget to use your usual diagnostic techniques (skin scrapings, Wood's light, fungal cultures, cytology of exudate, biopsies) for feline dermatologic problems.
  2. Atypical bacterial infections (Mycobacterium, Nocardia, Actinomyces) like to involve the inguinal area of cats and are resistant to the usual AB therapies.
  3. L-form bacterial infections appear like typical cat bite abscesses, often involve joints, but respond only to the tetracycline drugs.
  4. Watch out for Demodex in cats! And look for underlying immunosuppressive diseases or chronic diseases if you find it.
  5. Do not use griseofulvin in FIV-positive cats.
  6. Biopsy!!! and culture from tissue in all cats with chronic (apparently non-responsive) draining tracts.
  7. Always ask for special stains (acid-fast, fungal) on cat biopsy specimens and tell the lab what you are looking for.
  8. The behavior of cutaneous mast cell tumor in cats is much more benign than dogs and usually has an excellent prognosis.
Gastrointestinal:
  1. Inflammatory bowel disease is very common in cats and may occur without typical signs of vomiting or diarrhea.
  2. Ollulanus tricuspus (stomach worm) will not shed eggs in feces, larva must been seen in cat vomitus.
  3. Neutropenia + fever + diarrhea ... think Salmonella (esp. in the Northeast in the Fall)
  4. Chronic "infectious" diarrhea in cats... Clostridial diarrhea may not be responsive to metronidazole, try Clavamox.
  5. HWD causes vomiting in cats... keep on your differential in endemic areas.
  6. Check under the tongue in every vomiting cat.
  7. Giardia are hard to find. Try fenbendazole or albendazole for resistant Giardia cases.
  8. Try oral IFN or azathioprine for resistant LPS in cats, chlorambucil is another good adjunct for cats that fail corticosteroid therapy. Oral lactoferrin (Laktoferrin - Allergy Research Group (800) 654-4432) may also be helpful in some cats with LPS. Dose is: 350 mg (one capsule) q24h mixed in milk or swabbed on gums.
Liver:
  1. A yellow cat is NOT necessarily a dead cat.
  2. Liver enzymes are not elevated in up to 25% of cats with significant hepatic disease.
  3. Ptyalism (drooling) is the most common sign in cats with portosystemic shunts. Also consider PSS in any cat with urate calculi. Shunts are more common in Persian and Himalayan cats.
  4. Don't be fooled by chem panels... clinical icterus should be present if the bilirubin value is > 2.0 mg/dl (lipemia and hemolysis may give falsely high values).
  5. Feline SAP half life is 6 hours, no steroid isoenzyme, pay attention if the value is significantly elevated.
  6. If the SAP >>>, ALT >, GGT is N to > think hepatic lipidosis.
  7. If the ALT>>>, SAP>, GGT>, think hepatitis/CHC.
  8. AST (SGOT) is not liver specific in the cat.
  9. Any bilirubin in the urine of a cat is abnormal.
  10. If serum bilirubin is > 3.0 mg/dl, 90% of feline patients have a hepatic problem. If serum bilirubin is < 3.0 mg/dl, 50% of patients have a nonhepatic problem.
  11. Fine needle aspiration is diagnostic for HL in the majority of cases, and useful for DX many other liver diseases in the cat.
Ophthalmology:
  1. Non-traumatic uveitis: think FIP, toxoplasmosis, systemic mycoses
  2. Try oral interferon for cats with chronic herpetic keratitis.
  3. Intermittent fluctuating anisocoria, think FeLV.
  4. "Jiggly eyeballs" in Siamese or Siamese crossbred cats (ocular titubation) is caused by a visual pathway defect (but does not cause visual problems, just an interesting breed oddity).
  5. Check retinas in any cat with FUO as many chronic granulomatous diseases (FIP, systemic mycoses, etc) will cause retinitis.
  6. Acute retinal detachment is usually caused by hypertension. This is most often associated with renal insufficiency or hyperthyroidism.
  7. Enrofloxacin can cause blindness in cats. Especially at high doses, may not be reversible. Causes retinal degeneration. Use with caution.
Urinary:
  1. FeLV and FIV are the most common causes of non-traumatic urinary incontinence in cats.
  2. Urinalyses should always be collected by cystocentesis. Save 1ml of urine in a sterile container (sterile red top blood tube) in the refrigerator... if sediment suggests infection, you already have a specimen to culture.
  3. Most FLUDT cases clear within 7-10 days no matter what we do (or don't do).
  4. True bacterial UTI is rare in cats but more common in older cats... and these are also more likely to have pyelonephritis.
  5. Oxalate urinary calculi are becoming more common... due to acidifying diets?
  6. Surgery for renal calculi is not indicated in most patients...unless obstruction is present.
  7. Hypokalemia may result from renal disease and/or contribute to progression of renal lesions... supplement older cats with documented hypokalemia.
Reproductive:
  1. Bad breeders beget more bad breeders.
  2. Pyometra is a disease of young cats and diagnosis is more difficult than in dogs.
  3. If PGF is used to treat pyometra, breed on next cycle.
  4. Mammary hypertrophy hyperplasia causes massive symmetrical mammary development, OHE is curative but the mammary enlargement may take months to resolve.
  5. Mammary neoplasia in cats is almost always malignant.
  6. Protatitis does occur in intact male cats. If you can palpate the prostate, it is abnormal.
Endocrine:
  1. Hyperthyroidism is very common. Check a T4 on all cats over 8 years of age when performing routine screening.
  2. Free T4 values may be helpful in diagnosis in "borderline" or early hyperthyroid cases.
  3. Use serum fructosamine levels to help separate stress hyperglycemia from true diabetes mellitus.
  4. Use human recombinant insulin types. This author prefers NPH as most reliable in cats.
  5. Use microdose syringes and don't dilute insulin for best results.
  6. Some newer reflectance glucose meters are not accurate on venous blood samples (require capillary blood). Check instructions and label directions carefully before buying.
  7. Perform glucose curves to accurately reflect insulin activity and duration.
  8. Concurrent diseases are the most common cause of apparent insulin resistance in cats. Infection is the most common cause for insulin resistance overall, always culture urine! Of concurrent endocrinopathies, hyperthyroidism and HAC are the most common.
  9. If performing ACTH stimulation adrenal gland testing with synthetic ACTH in cats, take a 30 minute and one hour post-ACTH stimulation sample for cortisol analysis.
  10. The HIGH dose dexamethasone suppression test is the test of choice for diagnosing HAC in the cat.
Neurologic:
  1. Beware rabies! In endemic areas, rabies should always be on your list of DDX for unusual neurologic signs in cats. NEVER use a MLV rabies vaccine in a cat.
  2. Drooling (esp. young cats) +- behavior changes or seizures, think PSS.
  3. FIP is the most common cause of neurologic abnormalities in middle aged to older cats.
  4. Meningioma is the most common brain tumor of aged cats and is potentially very treatable by surgery. Circling and/or pacing is a common sign.
  5. Urinary incontinence and periodic anisocoria think of FeLV or FIV infection.
  6. Aberrant HW migration may cause neurologic dysfunction so think of this in endemic areas.
Infectious diseases:
  1. ALWAYS test sick cats for FeLV and FIV.
  2. FeLV PCR - there is no benefit to this technology for this disease except in evaluation of bone marrow.
  3. FIP PCR - this test is no more specific and may be less sensitive than others when used for blood testing, not recommended. There is NO "FIP-specific" ELISA (sorry, Antech)
  4. Definitive diagnosis of FIP relies on FA or immunohistochemistry of biopsy specimens from affected tissues.
  5. Bordetella may be a cause of URI in some catteries and groups of housed cats.
  6. Beware of plague and tularemia in sick cats with FUO in endemic areas. Be sure to alert your physicians to the possiblility of exposure if you become ill.
Cardiac:
  1. Many acquired feline cardiac murmurs are best heard near the sternum.
  2. Hypertension is common in older cats with renal insufficiency, hyperthyroidism, etc. Start checking pressures.
  3. Ultrasound is more useful than ECG in cats unless a rhythm disorder is the primary problem.




© 2004 - Alice M. Wolf, DVM, DACVIM, ABVP - All rights reserved