Biological variation of routine haematology and biochemistry measurands in the horse.

BACKGROUND: Clinical pathology results are typically interpreted by referring to population-based reference intervals. The use of individualised (subject-based) reference intervals is more appropriate for measurands with a high degree of variation between individuals. OBJECTIVES: To determine the biological variation of routinely analysed equine haematology and biochemistry measurands and calculate indices of individuality and reference change values which enable production of individualised reference intervals, in a group of healthy, privately owned horses. STUDY DESIGN: In a prospective cohort study, thirty-nine privately owned horses were sampled by jugular venipuncture for analysis of haematology and biochemistry measurands at weekly intervals for 6 weeks. METHODS: Haematology was analysed on the day of collection. Serum was frozen and biochemistry analyses performed on thawed samples. Duplicate results were obtained and the coefficient of variation was calculated for analytical variation, within-subject variation and between-subject variation. The index of individuality and reference change value were derived for each measurand. RESULTS: Haematology (red blood cell count, mean corpuscular haemoglobin and mean cell volume) and biochemistry measurands (total protein, globulins, albumin, gamma-glutamyl transferase, aspartate aminotransferase) demonstrated high individuality, indicating that individualised reference intervals are more appropriate for evaluation of these measurands. Two haematology (mean corpuscular haemoglobin concentration and platelets) and three biochemistry measurands (chloride, glucose and sodium) had low individuality, indicating that the use of traditional population-based reference intervals is appropriate for these measurands. Remaining measurands had intermediate individuality suggesting interpretation of the reference change value should occur with consideration of the population-based reference interval. MAIN LIMITATIONS: The use of privately owned horses, variable management and environmental factors. CONCLUSIONS: The use of individualised reference intervals is justified for many measurands in horses, supporting the use of serial sampling, consideration of biological variation and application of reference change values for improved clinical decision making and patient management in equine practice.

Susceptibility of rapidly growing mycobacteria isolated from cats and dogs, to ciprofloxacin, enrofloxacin and moxifloxacin.

Rapidly growing mycobacteria (RGM) cause infections in cats and dogs which require prolonged antibacterial medication for resolution. In Australia, pathogens from the Mycobacterium fortuitum and Mycobacterium smegmatis clusters are responsible for most of the RGM infections in cats and dogs. As fluoroquinolones are often recommended for treating such infections, 14 M. fortuitum isolates, 51 isolates from the M. smegmatis cluster and 2 M. mageritense isolates, collected from feline and canine patients, underwent susceptibility testing to the second generation fluoroquinolones ciprofloxacin and enrofloxacin and the newer generation fluoroquinolone moxifloxacin. Using microbroth dilution, the MIC(90) of ciprofloxacin, enrofloxacin, and moxifloxacin that inhibited growth of M. fortuitum isolates were 0.500, 0.250 and 0.063 µg/mL respectively. For the M. smegmatis cluster isolates the corresponding MIC(90) was 0.500, 0.250 and 0.125 µg/mL respectively. E-test results showed similar trends but MICs were lower than those determined by microbroth dilution. Additionally, moxifloxacin was administered to 10 clinically normal cats (50mg per cat, once daily for 4 days). The plasma moxifloxacin concentration 2h after the last dose was determined by liquid chromatography as 2.2 ± 0.6 µg/mL. The plasma concentration at 2h:MIC(90) ratios for moxifloxacin for M. fortuitum and M. smegmatis cluster was 34.9 and 17.6 respectively which exceeded the recommended threshold of 10, indicating that moxifloxacin has good theoretical efficacy for treatment of those M. fortuitum and M. smegmatis infections in cats and dogs that have become refractory to other antibacterial drug classes.

Prevalence of Bartonella species, Rickettsia felis, haemoplasmas and the Ehrlichia group in the blood of cats and fleas in eastern Australia.

OBJECTIVES: To define the prevalence of Bartonella spp., Rickettsia felis, Mycoplasma haemofelis, 'Candidatus Mycoplasma haemominutum' (Mhm) and 'Candidatus Mycoplasma turicensis' (Mtc) in cats and their fleas in eastern Australia. DESIGN AND PROCEDURE: Conventional PCR assays that detect Bartonella spp., M. haemofelis, Mhm, Mtc, Rickettsia spp., Ehrlichia spp., Anaplasma spp. and Neorickettsia spp. were performed on DNA extracted from blood and fleas collected from 111 cats. Cat sera were assayed by ELISA for IgG of Bartonella spp. RESULTS: DNA of M. haemofelis, Mtc and Mhm was amplified from 1 (0.9%), 1 (0.9%) and 17 cats (15.3%), respectively. Only DNA of Mhm was amplified from the 62 of 111 pooled flea samples (flea sets; 55.9%). Overall, the prevalence rates for Bartonella spp. DNA in the cats and the flea sets was 16.2% (18 cats) and 28.8% (32 flea sets), respectively. Bartonella spp. IgG was detected in 42 cats (37.8%), of which 11 (26.2%) were positive for Bartonella spp. DNA in their blood. R. felis DNA was amplified from 22 flea sets (19.8%), but not from cats. Overall, DNA of one or more of the organisms was amplified from 27% (30) of cats and 67.6% (75) of the flea sets. CONCLUSIONS: This is the first Australian study to determine the prevalence of R. felis and B. clarridgeiae in both fleas and the cats from which they were collected. Flea-associated infectious agents are common in cats and fleas in eastern Australia and support the recommendation that stringent flea control be maintained on cats.

Naturally-occurring chronic renal disease in Australian cats: a prospective study of 184 cases.

OBJECTIVE: To describe cases of naturally occurring feline chronic renal disease (CRD) in a defined population of Sydney. DESIGN: Prospective case series. METHODS: The inclusion criteria were the presence of a serum creatinine concentration above the reference range with either inadequately concentrated urine (urine specific gravity < or = 1.035), necropsy findings consistent with CRD, renal proteinuria or persistent azotaemia despite rehydration. Cats were excluded if a specific aetiology was identified ante or post mortem. Patients were divided into two categories (renal insufficiency or renal failure) on the basis of history, physical findings and serum creatinine concentration. The gender and age of cats with CRD was compared to an estimated Australian urban pet cat population. The breeds of cats with CRD were compared to the breeds of cats visiting the respective veterinary hospital where possible. Breed and gender comparisons were made using Fisher's exact tests. Age comparisons were made using Mann-Whitney U tests. The age at which cats were diagnosed with CRD was compared between veterinary hospitals using a Kruskal-Wallis test. RESULTS: One hundred and eighty-four (99 female; 85 male) cats fulfilled the inclusion criteria. Amongst cats with CRD, males (median 12 years) were significantly younger than females (median 15 years; p = 0.001). The overall proportion of male and female cats with CRD was similar to that of the reference urban cat population (p = 0.41), however, between the ages of 9 and 11 years, male cats with CRD were over-represented (p = 0.038). Patients diagnosed with renal insufficiency (123 cats; median age 15 years) were significantly older than patients diagnosed with renal failure (61 cats; median age 11 years; p = 0.0001). The age at diagnosis of cats with CRD differed significantly between veterinary hospitals (p = 0.002). CONCLUSION: Male cats with CRD were significantly younger than female cats with CRD. Younger cats were more likely to be diagnosed at an advanced stage of disease than older cats. The age at which cats were diagnosed with CRD was influenced by the clinic the cats attended. Whether these differences reflect differences in the aetiology of CRD or in the rate of disease progression warrants further investigation. Breed did not appear to play a significant role in the development of CRD in this survey.

Susceptibility of bacteria from feline and canine urinary tract infections to doxycycline and tetracycline concentrations attained in urine four hours after oral dosage.

OBJECTIVES: To measure urinary concentrations of doxycycline in cats and dogs and tetracycline in dogs 4 h after conventional oral dosing and determine whether these antibiotics were present in sufficient concentrations to be effective against common feline and canine urinary tract pathogens as assessed in vitro by Epsilometer and disc diffusion antimicrobial susceptibility methods. DESIGN: A prospective study involving oral administration to clinically normal cats and dogs of doxycycline or tetracycline (dogs only) and culture of bacteria from dogs and cats with urinary tract infections to determine their susceptibility to both doxycycline and tetracycline in vitro. PROCEDURE: In the first study, nine cats and eight dogs were administered doxycycline monohydrate (5 mg/kg every 12 h) and a further eight dogs were administered tetracycline hydrochloride (20 mg/kg every 8 h) for 72 h. Blood was collected at 2 and 4 h, and urine at 4 h, after the last dose. The concentration of each agent in serum and urine was determined by modified agar diffusion. In the second study, 45 urine samples from cats and dogs with urinary tract infections were cultured. Every bacterial isolate was tested in vitro using both Epsilometer (doxycycline and tetracycline) and disc diffusion (doxycycline, tetracycline or amoxycillin-clavulanate) tests. RESULTS: Serum doxycycline concentrations in sera of cats and dogs at 2 h were 4.2 +/- 1.0 mg/mL and 3.4 +/- 1.1 mg/mL, respectively. The corresponding concentrations at 4 h were 3.5 +/- 0.7 mg/mL and 2.8 +/- 0.6 mg/mL. Urinary doxycycline concentrations at 4 h (53.8 +/- 24.4 mg/mL for cats and 52.4 +/- 24.1 mg/mL for dogs) were substantially higher than corresponding serum values. Serum tetracycline concentrations in dogs at 2 and 4 h, and in urine at 4 h, were 6.8 +/- 2.8, 5.4 +/- 0.8, 144.8 +/- 39.4 mg/mL, respectively. Most of the urinary tract pathogens (35/45) were susceptible to urinary concentrations of doxycycline and 38/45 were susceptible to tetracycline. In contrast 41/45 of all isolates were susceptible to amoxycillin-clavulanate. CONCLUSION: This is the first report of urinary concentrations of doxycycline after conventional oral administration. Concentrations attained in the urine of normal cats and dogs were sufficient to inhibit the growth of a significant number of urinary tract pathogens and thus doxycycline may be a useful antimicrobial agent for some urinary tract infections.

Clinicopathological findings associated with feline infectious peritonitis in Sydney, Australia: 42 cases (1990-2002).

OBJECTIVES: To review the clinicopathological findings in naturally-occurring, histopathologically confirmed cases of feline infectious peritonitis in client-owned cats in Sydney, Australia, with the purpose of identifying factors assisting in the diagnosis of this complex disease syndrome and to characterise the disease as it occurs in this region. DESIGN: Retrospective clinical study: the clinical records of all cats with histopathologically confirmed feline infectious peritonitis at the University Veterinary Centre Sydney and a private cat hospital in Sydney between 1990 and 2002 were reviewed for signalment, history, physical findings, diagnostic test results and the distribution of histological lesions throughout the body at necropsy. RESULTS: Forty-two cats met the inclusion criteria. Significant features of this study that unique to the contemporary literature are i) the over-representation of certain breeds (Burmese, Australian Mist, British Shorthaired, and Cornish Rex) and the under-representation of other breeds (Domestic Shorthaired, Persian); ii) the overrepresentation of males; iii) the tendency for effusive disease in Australian Mist cats and non-effusive disease in Burmese; iv) the even age distribution of disease seen in cats older than 2 years-of-age; and v) the presence of fulminant immune-mediated haemolytic anaemia in two cats in this study. CONCLUSION: The study highlights the diverse range of clinical manifestations and the complexities experienced by clinicians in diagnosing this fatal disease. Some aspects of the epidemiology and clinical manifestations of feline infectious peritonitis appear different to the disease encountered in Europe and North America, most notably the over-representation of specific breeds and the presence of immune-mediated haemolytic anaemia.