Current Understanding of the Pathogenesis of Progressive Chronic Kidney Disease in Cats

Renal alterations in cats (Felis catus) housed in shelters and affected by systemic AA-amyloidosis: Clinicopathological data, histopathology, and ultrastructural features

AA-amyloidosis is frequent in shelter cats, and chronic kidney disease is the foremost cause of death. The aims were to describe kidney laboratory and microscopic findings in shelter cats with AA-amyloidosis. Cats were included if kidney specimens were collected post-mortem and laboratory data were available within 6 months before death. Renal lesions were evaluated with optical and electron microscopy. Mass spectrometry was used to characterize amyloid. Nine domestic short-hair cats were included; 4 females and 5 males with a median age of 8 years (range = 2-13). All cats had blood analyses and urinalyses available. Serum creatinine concentrations were increased in 6 cats and symmetric dimethylarginine was increased in all of the cats. All of the cats had proteinuria. Eight of 9 cats had amyloid in the medulla, and 9 had amyloid in the cortex (glomeruli). All cats had amyloid in the interstitium. Six cats had concurrent interstitial nephritis and 1 had membranoproliferative glomerulonephritis. All cats had extrarenal amyloid deposits. Amyloid was AA in each case. In conclusion, renal deposition of amyloid occurs in both cortex and medulla in shelter cats and is associated with azotemia and proteinuria. Renal involvement of systemic AA-amyloidosis should be considered in shelter cats with chronic kidney disease. The cat represents a natural model of renal AA-amyloidosis.

Comparison of serum creatinine, point-of-care symmetric dimethylarginine and renal imaging with glomerular filtration rate measured by renal scintigraphy in healthy and early chronic kidney diseased cats

The aim of this study was to evaluate routinely used tests to diagnose cats in early stages of chronic kidney disease (CKD) and to describe a model for evaluating these variables simultaneously. Apparently healthy cats were screened using serum creatinine (sCr), point-of-care symmetric dimethylarginine (POC SDMA), urinalysis, urine protein/creatinine ratio (UPC) and imaging evaluation. Those parameters were compared to glomerular filtration rate (GFR) assessed by renal scintigraphy. Forty-four cats were included and consisted of 14 (31.8%) healthy cats (absence of abnormalities in renal morphology and sCr less than 1.6 mg/dL), 20 (45.5%) cats classified as CKD I (presence of abnormalities in renal morphology and sCr less than 1.6 mg/dL) and ten (22.7%) as CKD II (sCr equal to or greater than 1.6 mg/dL, with or without abnormalities in renal morphology). A large number (40.9%) of apparently healthy cats presented reduction in GFR, which included half of CKD I patients. Point-of-care SDMA was not a good predictor for decreased GFR, nor was it correlated with the variables GFR and sCr. Glomerular filtration rate was significantly lower in CKD I and II groups in comparison with healthy cats, but there was no significant difference between the CKD I and II groups. Multivariate logistic regression model identified three variables that affected the odds of a cat having decreased GFR (< 2.5 mL/min/kg): sCr (OR = 18.3; p = 0.019; CI = 1.6-207.2), and the ultrasonographic findings 'reduced corticomedullary definition' (OR = 19.9; p = 0.022; CI = 1.6-254.0) and 'irregular contour' (OR = 65.6; p = 0.003; CI = 4.2-1038.2). Renal ultrasonography evaluation should always be considered for screening early CKD in apparently healthy cats.

Chronic kidney disease in a giant panda (Ailuropoda melanoleuca): a case report

BACKGROUND

Chronic kidney disease (CKD) is a common cause of morbidity and mortality in captive wildlife species. However, CKD has been rarely documented in giant pandas.

CASE PRESENTATION

The following report describes a case of an eight-year-old female giant panda showing clinical signs of epistaxis, bloody diarrhea, polyuria, azotemia and anemia. The animal died despite of supportive treatments. Necropsy was performed. Grossly, both kidneys were shrunken and scarred with pallor. Subcutis edema and petechia on the epicardium of the heart were observed. The tissue samples were made into paraffin sections and stained by H.E and special staining including Periodic Acid-Schiff (PAS), von Kossa, Masson's trichrome, Phosphotungstic acid-hematoxylin (PTAH), and Congo red. Histopathology examination revealed severe chronic tubulointerstitial nephritis with marked interstitial fibrosis, glomerulosclerosis, tubular atrophy and calcification in kidneys, and acute necrotizing hemorrhagic myocarditis with calcification in heart. Other lesions included intestinal hemorrhage, hepatic fatty degeneration and necrosis with hemosiderin, and splenic hemosiderin.

CONCLUSIONS

In summary, chronic kidney disease was finally diagnosed based on the association of clinical, gross, and histopathological findings. Heart failure secondary to CKD is the leading cause of death in this giant panda. The potential cause of CKD in this animal is possibly due to long term and uncontrolled hypertension. Blood pressure monitoring is essential in establishing the diagnosis and management of hypertension in giant panda.

DISEASE PROCESSES IDENTIFIED IN CAPTIVE ARABIAN SAND CATS (FELIS MARGARITA HARRISONI)

The objective of this retrospective study is to identify common and significant causes of mortality and disease processes in the Arabian sand cat (Felis margarita harrisoni) captive population at Al Ain Zoo (Abu Dhabi, United Arab Emirates). Complete postmortem records of 25 Arabian sand cats, dead between 2009 and 2022, were reviewed retrospectively. A complete postmortem examination was done in all cases, and information was recorded in the Al Ain Zoo database and files. Out of 25 animals dead, 11 were adults (4-12 yr) and 12 were classified as geriatric animals (>12 yr), with only two neonatal (0-4 mon) deaths and no recorded deaths in juveniles (4 mon to 4 yr). Interestingly, but also expected because of the age range, 24% of the cases had concurrent pathologies at the time of death. As expected in adult and geriatric felines, more than half of the cases (60%) developed nephropathies that were either one of the most important contributors or the main cause of death of the animal. Different neoplastic lesions were described in four cases and reported for the first time in this subspecies: benign peripheral nerve sheath tumor, hepatobiliary carcinoma, and two different thyroid neoplasia. A vasculoproliferative disorder of the liver, peliosis hepatis, was described in one of the cases. Additionally, in at least four cases, hyperthyroidism was strongly suspected in connection with thyroid neoplasia and hyperplasia, clinical signs, and other observed postmortem lesions. Traumatic causes of death also were reported in six cases, including the only two neonates recorded dead. This information will contribute to Arabian sand cat improved veterinary care by identifying common pathologies in this species, potentially allowing earlier diagnosis and, ultimately, improving their management and husbandry in the captive breeding populations.

Comparison of ultrasonographic renal measurements in kittens up to 3 months of age and young cats

OBJECTIVES

This study aimed to evaluate renal measurements by B-mode ultrasound in kittens during their first 3 months and compare them with those of young adult cats.

METHODS

Forty-eight healthy mixed-breed cats (24 males and 24 females) were enrolled in this study. The cats were divided into six age groups: groups 1-5 (kittens) and group 6 (young adult cats). Each kidney was examined using B-mode imaging and the following measurements taken: renal length (RL), renal height (RH), renal width (RW), cortical thickness (CoT), medullary thickness (MdT) and corticomedullary ratio (CMr). The ratio and correlation of RL to aortic diameter (AoD) and the length of the fifth/sixth lumbar vertebrae (LLV) were also determined.

RESULTS

Among groups, there was a statistically significant difference between RW, renal volume (RV), CoT, MdT and CMr. The smallest renal dimensions were obtained in the youngest kittens (up to 10 days of age), including RL (1.84 ± 0.40 cm), RH (1.14 ± 0.17 cm), RW (1.25 ± 0.20 cm) and RV (1.47 ± 0.68 ml). A strong correlation was observed between RL:AoD and RL:LLV, allowing for linear regression equations and reference intervals for RL:AoD and RL:LLV to be created for each age group.

CONCLUSIONS AND RELEVANCE

B-mode ultrasound showed that renal measurements in kittens differed from those in young adult cats, and that the renal dimensions, renal CoT and CMr increased with the growth of the cat. The RL-LLV ratio is a reliable method for measuring RL according to age group.

Balancing the scale

Traditional discussions involving 'basic' and 'applied' behavioral research often focus on the differences, or gaps, between these areas. They take place in different environments, use different methods, ask different questions, and have different objectives. Applied animal behavior is no exception. Focusing on the differences in these areas is to the detriment of a cohesive and complete understanding of animal behavior. This paper instead focuses on the similarities between these two sides, and presents them as a matter of scale. A series of real-life examples experienced by the authors is used to highlight how the skills and knowledge of both the applied and the basic sides are valuable and necessary to not only further both fields independently, but to develop a comprehensive understanding of animal behavior.

Serum fibroblast growth factor-23 concentrations in young and mature adult cats with chronic kidney disease

OBJECTIVES

The aim of this study was to investigate serum fibroblast growth factor (FGF)-23 concentrations in young and mature adult cats with chronic kidney disease (CKD).

METHODS

The present study retrospectively investigated the serum samples and medical records of 1-8-year-old clinically healthy cats (control group, n = 7) and cats with CKD (n = 54). Cats with CKD were divided into four stages based on serum creatinine concentrations, according to the International Renal Interest Society (IRIS) CKD guidelines. Serum FGF-23 concentrations were compared between cats in the control group, IRIS stages 1, 2 and 3-4 CKD. Continuous variables were analysed using correlations and multiple linear regression.

RESULTS

Serum FGF-23 concentrations were significantly higher in cats with IRIS stages 1, 2 and 3-4 CKD, compared with those in the control group (P = 0.02, P = 0.002 and P = 0.002, respectively). Additionally, serum FGF-23 concentrations in cats with IRIS stages 3-4 CKD had higher serum FGF-23 concentrations than those with IRIS stages 1 and 2 CKD (P = 0.04 and P = 0.02, respectively). In the multiple linear regression analysis, serum urea nitrogen concentration, serum phosphorus concentration and blood ionised calcium concentration were independent variables predicting serum FGF-23 concentration.

CONCLUSIONS AND RELEVANCE

Serum FGF-23 concentrations in younger cats with CKD increased in early-stage CKD and were associated with mineral metabolic markers, as also occurs in geriatric cats.

MicroRNAs are differentially expressed in the serum and renal tissues of cats with experimentally induced chronic kidney disease: a preliminary study

OBJECTIVE

To identify differentially expressed microRNA in the serum and renal tissues of cats with experimentally induced chronic kidney disease (CKD).

SAMPLE

Banked renal tissues and serum from 4 cats.

PROCEDURES

Cats previously underwent 90-minute unilateral ischemia with delayed contralateral nephrectomy 3 months after ischemia. Tissues were collected from the contralateral kidney at the time of nephrectomy and from the ischemic kidney 6 months after nephrectomy (study end). Serum was collected prior to ischemia (baseline serum) and at study end (end point serum). Total RNA was isolated from tissues and serum, and microRNA sequencing was performed with differential expression analysis between the contralateral and ischemic kidney and baseline and end point serum.

RESULTS

20 microRNAs were differentially expressed between ischemic and contralateral kidneys, and 52 microRNAs were differentially expressed between end point and baseline serum. Five microRNAs were mutually differentially expressed between ischemic and contralateral kidneys and baseline and end point serum, with 4 (mir-21, mir-146, mir-199, and mir-235) having increased expression in both the ischemic kidney and end point serum and 1 (mir-382) having increased expression in the ischemic kidney and decreased expression in end point serum. Predicted target search for these microRNA revealed multiple genes previously shown to be involved in the pathogenesis of feline CKD, including hypoxia-inducible factor-1α, transforming growth factor-β, hepatocyte growth factor, fibronectin, and vascular endothelial growth factor A.

CLINICAL RELEVANCE

MicroRNAs were differentially expressed after CKD induction in this preliminary study. Regulation of renal fibrosis in feline CKD may occur through microRNA regulation of mRNAs of pro- and anti-fibrotic genes.

Renal Senescence, Telomere Shortening and Nitrosative Stress in Feline Chronic Kidney Disease

Kidney tissues from cats with naturally occurring chronic kidney disease (CKD) and adult and senior cats without CKD were assessed to determine whether telomere shortening and nitrosative stress are associated with senescence in feline CKD. The histopathologic assessment of percent global glomerulosclerosis, inflammatory infiltrate, and fibrosis was performed. Senescence and nitrosative stress were evaluated utilizing p16 and iNOS immunohistochemistry, respectively. Renal telomere length was evaluated using telomere fluorescent in situ hybridization combined with immunohistochemistry. CKD cats were found to have significantly increased p16 staining in both the renal cortex and corticomedullary junction compared to adult and senior cats. Senior cats had significantly increased p16 staining in the corticomedullary junction compared to adult cats. p16 staining in both the renal cortex and corticomedullary junction were found to be significantly correlated with percent global glomerulosclerosis, cortical inflammatory infiltrate, and fibrosis scores. p16 staining also correlated with age in non-CKD cats. Average telomere length was significantly decreased in CKD cats compared to adult and senior cats. CKD cats had significantly increased iNOS staining compared to adult cats. Our results demonstrate increased renal senescence, telomere shortening, and nitrosative stress in feline CKD, identifying these patients as potential candidates for senolytic therapy with translational potential.

Machine-learning algorithm as a prognostic tool in non-obstructive acute-on-chronic kidney disease in the cat

OBJECTIVES

The aim of this study was to develop an algorithm capable of predicting short- and medium-term survival in cases of intrinsic acute-on-chronic kidney disease (ACKD) in cats.

METHODS

The medical record database was searched to identify cats hospitalised for acute clinical signs and azotaemia of at least 48 h duration and diagnosed to have underlying chronic kidney disease based on ultrasonographic renal abnormalities or previously documented azotaemia. Cases with postrenal azotaemia, exposure to nephrotoxicants, feline infectious peritonitis or neoplasia were excluded. Clinical variables were combined in a clinical severity score (CSS). Clinicopathological and ultrasonographic variables were also collected. The following variables were tested as inputs in a machine learning system: age, body weight (BW), CSS, identification of small kidneys or nephroliths by ultrasonography, serum creatinine at 48 h (Crea48), spontaneous feeding at 48 h (SpF48) and aetiology. Outputs were outcomes at 7, 30, 90 and 180 days. The machine-learning system was trained to develop decision tree algorithms capable of predicting outputs from inputs. Finally, the diagnostic performance of the algorithms was calculated.

RESULTS

Crea48 was the best predictor of survival at 7 days (threshold 1043 µmol/l, sensitivity 0.96, specificity 0.53), 30 days (threshold 566 µmol/l, sensitivity 0.70, specificity 0.89) and 90 days (threshold 566 µmol/l, sensitivity 0.76, specificity 0.80), with fewer cats still alive when their Crea48 was above these thresholds. A short decision tree, including age and Crea48, predicted the 180-day outcome best. When Crea48 was excluded from the analysis, the generated decision trees included CSS, age, BW, SpF48 and identification of small kidneys with an overall diagnostic performance similar to that using Crea48.

CONCLUSIONS AND RELEVANCE

Crea48 helps predict short- and medium-term survival in cats with ACKD. Secondary variables that helped predict outcomes were age, CSS, BW, SpF48 and identification of small kidneys.

Hypoxia and chronic kidney disease: Possible mechanisms, therapeutic targets, and relevance to cats

There is mounting evidence that kidney ischaemia/hypoxia plays an important role in feline chronic kidney disease (CKD) development and progression, as well as in human disease and laboratory animal models. Ischaemic acute kidney injury is widely accepted as a cause of CKD in people and data from laboratory species has identified some of the pathways underlying this continuum. Experimental kidney ischaemia in cats results in morphological changes, namely chronic tubulointerstitial inflammation, tubulointerstitial fibrosis, and tubular atrophy, akin to those observed in naturally-occurring CKD. Multiple situations are envisaged that could result in acute or chronic episodes of kidney hypoxia in cats, while risk factors identified in epidemiological studies provide further support that kidney hypoxia contributes to spontaneously occurring feline CKD. This review evaluates the evidence for the role of kidney ischaemia/hypoxia in feline CKD and the proposed mechanisms and consequences of kidney hypoxia. As no effective treatments exist that substantially slow or prevent feline CKD progression, there is a need for novel therapeutic strategies. Targeting kidney hypoxia is one such promising approach, with therapies including those that attenuate the hypoxia-inducible factor (HIF) pathway already being utilised in human CKD.

Absence of renal cortical anisotropic backscattering artifact in feline chronic kidney disease

Renal cortical anisotropy backscattering artifact (CABA) is a focal hyperechoic region where the tubules are parallel to the incident ultrasound beam, reflecting most of the beams to the transducer. To investigate the association between chronic kidney disease (CKD) and the absence of renal CABA in cats. Ultrasonographic renal images of 40 cats with CKD (stage II-IV) and 36 clinically healthy cats were blindly evaluated by two observers to determine the visibility of renal CABA. Inter- and intraobserver agreements were evaluated using McNemar's test. The association between the absence of renal CABA and CKD was assessed using Fisher's exact test. Excellent intraobserver and substantial interobserver agreements were demonstrated. A significant association (P < .0001) between absent renal CABA and CKD stage was revealed in all cats. Cats with CKD had an increased risk of the absence of renal CABA (Odds ratio, 56.0; 95% CI, 13.8-227.0) compared with the clinically healthy cats. The absence of renal CABA revealed 87.5% sensitivity and 88.9% specificity to detect CKD in all cats, and 91.7% sensitivity and 83.3% specificity in aged cats. Our study demonstrated a correlation between feline CKD and the absence of renal CABA, providing a feasible and alternative method for feline CKD evaluation.

Feline Morbillivirus Infection in Domestic Cats: What Have We Learned So Far?

Feline morbillivirus (FeMV) was identified for the first time in stray cats in 2012 in Hong Kong and, since its discovery, it was reported in domestic cats worldwide. Although a potential association between FeMV infection and tubulointerstitial nephritis (TIN) has been suggested, this has not been proven, and the subject remains controversial. TIN is the most frequent histopathological finding in the context of feline chronic kidney disease (CKD), which is one of the major clinical pathologies in feline medicine. FeMV research has mainly focused on defining the epidemiology, the role of FeMV in the development of CKD, and its in vitro tropism, but the pathogenicity of FeMV is still not clear, partly due to its distinctive biological characteristics, as well as to a lack of a cell culture system for its rapid isolation. In this review, we summarize the current knowledge of FeMV infection, including genetic diversity of FeMV strains, epidemiology, pathogenicity, and clinicopathological findings observed in naturally infected cats.

The utility of combined urine dipstick analysis and specific gravity measurement to determine feline proteinuria

OBJECTIVES

To assess the utility of urine dipstick strips for detection of feline proteinuria when used in combination with urine-specific gravity, compared with urine protein-to-creatinine ratio as the gold standard.

MATERIALS AND METHODS

Retrospective analysis of clinical records of comprehensive urine examination obtained from cats presented to a referral hospital. Diagnostic agreement and test accuracy were calculated for the dipstick test alone and in combination with the urine-specific gravity, using different cut-off values for proteinuria. Receiver-operating characteristic curves were also calculated.

RESULTS

A total of 121 urine samples were included. The diagnostic agreement between dipstick and urine protein-creatinine ratio was poor. A dipstick result of equal or greater than "Trace" (0.1-0.3 g/L) had a sensitivity of 81% and a specificity of 31% to detect proteinuria. Grouping the samples by urine-specific gravity did not increase dipstick agreement with the urine protein-creatinine ratio and only resulted in a slight improvement in the accuracy of detecting proteinuria.

CLINICAL SIGNIFICANCE

The dipstick test was not accurate for detecting proteinuria when combined with urine-specific gravity in cats. Clinicians should not rely on this test and, regardless of the urine concentration, other appropriate quantitative methods such as urine protein-creatinine ratio should always be performed to detect proteinuria in cats.

Molecular epidemiology and genome analysis of feline morbillivirus in household and shelter cats in Thailand

Background

Feline morbillivirus (FeMV) has been discovered in domestic cats associated with tubulointerstitial nephritis, but FeMV is also detected in healthy cats. This research aimed to identify and characterize the FeMV strains detected in a Thai cat population.

Results

Two-hundred and ninety-two samples (131 urine and 161 blood) derived from 261 cats (61 sheltered and 200 household cats) were included for investigating the FeMV prevalence using real-time reverse transcription PCR. The overall prevalence of FeMV detection was 11.9% (31/261) among both samples, which accounted for 14.5% (19/131) and 7.5% (12/161) of the urine and blood samples, respectively. Among the FeMV-PCR positive cats, the FeMV-detected prevalence was insignificantly associated with healthy cats (58.1%; 18/31) or urologic cats (41.9%; 13/31). Full-length genome analysis of these FeMV-Thai strains revealed that their genomes clustered together in the FeMV-1A clade with up to 98.5% nucleotide identity. Selective pressure analysis showed that overall FeMV-1 has undergone negative selection, while positive selection sites were more frequently observed in the phosphoprotein gene.

Conclusions

The detected FeMV infections in the Thai cat population were not correlated with urologic disorders, although the virus was more detectable in urine samples. The genetic patterns among the FeMV-1 Thai strains were more consistent. A large-scale study of FeMV in Thai cat samples is needed for further elucidation.

Aldosterone and the mineralocorticoid receptor in renal injury: A potential therapeutic target in feline chronic kidney disease

There is a growing body of experimental and clinical evidence supporting mineralocorticoid receptor (MR) activation as a powerful mediator of renal damage in laboratory animals and humans. Multiple pathophysiological mechanisms are proposed, with the strongest evidence supporting aldosterone-induced vasculopathy, exacerbation of oxidative stress and inflammation, and increased growth factor signalling promoting fibroblast proliferation and deranged extracellular matrix homeostasis. Further involvement of the MR is supported by extensive animal model experiments where MR antagonists (such as spironolactone and eplerenone) abrogate renal injury, including ischaemia-induced damage. Additionally, clinical trials have shown MR antagonists to be beneficial in human chronic kidney disease (CKD) in terms of reducing proteinuria and cardiovascular events, though current studies have not evaluated primary end points which allow conclusions to made about whether MR antagonists reduce mortality or slow CKD progression. Although differences between human and feline CKD exist, feline CKD shares many characteristics with human disease including tubulointerstitial fibrosis. This review evaluates the evidence for the role of the MR in renal injury and summarizes the literature concerning aldosterone in feline CKD. MR antagonists may represent a promising therapeutic strategy in feline CKD.

The Multicomponent, Multitarget Therapy SUC in Cats with Chronic Kidney Disease: A Multicenter, Prospective, Observational, Nonrandomized Cohort Study

BACKGROUND

We compared the natural multicomponent, multitarget therapy SUC (Solidago compositum ad us. vet., Ubichinon compositum and Coenzyme compositum, Heel GmbH, Baden-Baden, Germany) to the well-known angiotensin-converting enzyme inhibitor benazepril in a prospective, observational, nonrandomized, two-arm cohort study of cats with chronic kidney disease (CKD). The objective was to assess the tolerability and the effectiveness of SUC in cats with CKD.

MATERIAL AND METHODS

One hundred thirty-six cats were screened for CKD, and 70 cats were eligible for the study. Thirty-three cats were assigned to the SUC treatment, and 35 cats received benazepril. All cats were diagnosed with CKD. The follow-up period was 168 days. Response was assessed as an improved or stable serum creatinine from baseline to the end of the study. Additionally, a clinical summary score, as measure of quality of life, was evaluated.

RESULTS

Serum creatinine remained close to baseline in both study groups with slightly improved values in the SUC group. The clinical summary score improved significantly in the SUC group on days 3, 7, 28, 56 and 112, but not on day 168.

CONCLUSIONS

Within the limitations of the study, the results carry implications for the usefulness of SUC as an interesting new treatment option for feline CKD. The results indicate that SUC might be more effective if given at least twice weekly.

Epidemiology, pathological aspects and genome heterogeneity of feline morbillivirus in Italy

Feline morbillivirus (FeMV) is an emerging morbillivirus first described in cats less than a decade ago. FeMV has been associated with chronic kidney disease of cats characterized by tubulointerstitial nephritis (TIN), although this aspect is still controversial and not demonstrated with certainty. To investigate FeMV prevalence and genomic characteristics, an epidemiological survey was conducted in a total number of 127 household cats originating from two Italian regions, Abruzzi and Emilia-Romagna. A total number of 69 cats originating from three feline colonies were also enrolled for the study. Correlation with TIN was investigated by employing a total number of 35 carcasses. Prevalence of FeMV RNA was higher in urine samples collected from cats of colonies (P = 31.8%, CI 95% 22.1-43.6) compared to household cats (P = 8.66%, CI 95% 4.9-14.9) and in young and middle-aged cats while prevalence of FeMV Abs was higher in old cats. Sequences obtained straight from infected biological samples, either partial or complete, cluster into two clades within FeMV genotype 1, distantly related to FeMV genotype 2. Immunohistochemistry analysis of kidney sections of FeMV RNA positive cats revealed immunoreactivity within epithelial cells of renal tubuli and inflammatory cells. However, statistically significant association between FeMV and renal damages, including TIN, was not demonstrated (p= 0.0695, Fisher exact test). By virus histochemistry performed with FeMV-negative feline tissues and a FeMV isolate, tropism for different cellular types such as inflammatory cells residing in blood vessels of kidney and brain, airway epithelial cells, alveolar macrophages and to a lesser extent, the central nervous system, was demonstrated. Additional studies are warranted in order to establish viral tropism and immune response during the early phases of infection and to disentangle the role of FeMV in co-infection processes.

A RETROSPECTIVE STUDY OF MORBIDITY AND MORTALITY IN THE NORTH AMERICAN AMUR LEOPARD ( PANTHERA PARDUS ORIENTALIS) POPULATION IN ZOOLOGIC INSTITUTIONS FROM 1992 TO 2014

The Amur leopard ( Panthera pardus orientalis) is one of the most critically endangered leopards on the International Union for the Conservation of Nature red list. The primary objective of this retrospective study was to identify common and significant causes of morbidity and mortality in the North American Amur leopard zoo population. This information provides insights that contribute to their improved care, health, and medical management and, ultimately, affects the sustainability of this leopard subspecies in the wild. Medical records and complete postmortem reports were requested from all North American zoologic institutions that held Amur leopards in their collections from 1992 to 2014. Information from 175 individuals, representing 93% of the population (188 animals), was received. Data were reviewed generally and by subdivision into the following age groups: neonate: 0 day-3 mo ( n = 45); juvenile-young adult: 3 mo-5 yr ( n = 21); adult: 5-10 yr ( n = 17); senior: 10-15 yr ( n = 31); or geriatric: >15 yr ( n = 61). The major causes of morbidity, listed by body system for the study population, excluding neonates, were musculoskeletal (40%), reproductive (24%), dental (19%), cardiopulmonary (13%), gastrointestinal (13%), and urogenital (12%). The two most common causes of death or euthanasia, primarily in senior and geriatric animals, were chronic renal disease and neoplasia; maternal neglect and maternal trauma were most common in neonates. The largest populations in this study were neonates and geriatrics, indicating that if animals survive the neonatal period, they often live into their late teens to early 20s. This is the first comprehensive study of the causes of morbidity and mortality in the Amur leopard zoo population in North America.

Urinary neutrophil gelatinase-associated lipocalin in dogs with stable or progressive kidney disease

BACKGROUND

Active kidney injury may play a role in chronic kidney disease (CKD) progression in dogs. Neutrophil gelatinase-associated lipocalin (NGAL), a novel tubular kidney injury biomarker, may help differentiate progressive CKD from stable CKD in dogs.

OBJECTIVES

To determine if urinary NGAL : creatinine ratio (UNCR) differentiates stable and progressive CKD in dogs. We hypothesized that UNCR would be higher in dogs with progressive CKD versus stable CKD.

ANIMALS

Twenty-one healthy control dogs, 22 with prerenal azotemia, 19 with stable CKD, 30 with progressive CKD, and 27 with acute kidney injury (AKI).

METHODS

Prospective study. Azotemic (serum creatinine concentration >1.6 mg/dL) dogs or nonazotemic AKI dogs were enrolled and classified into 4 groups: (1) prerenal azotemia, (2) stable CKD, (3) progressive CKD, and (4) AKI. Urinary NGAL was measured by ELISA and UNCR compared among groups. Urine protein : creatinine ratio (UPC) in dogs with stable and progressive CKD was compared to UNCR for differentiating CKD groups.

RESULTS

UNCR was significantly higher in dogs with progressive CKD than stable CKD. UNCR of the prerenal azotemia group was significantly lower than that of the progressive CKD and AKI groups. No significant difference was found in UNCR between stable CKD and prerenal azotemia groups. ROC curve analysis of UNCR for differentiating progressive CKD from stable CKD resulted in an AUC of 0.816 (95% confidence interval [CI], 0.673-0.959), greater than that of UPC (0.696; 95% CI, 0.529-0.863).

CONCLUSIONS AND CLINICAL IMPORTANCE

Urinary NGAL could be helpful to predict the risk of progression in dogs with CKD.

A New Genotype of Feline Morbillivirus Infects Primary Cells of the Lung, Kidney, Brain and Peripheral Blood

Paramyxoviruses comprise a large number of diverse viruses which in part give rise to severe diseases in affected hosts. A new genotype of feline morbillivirus, tentatively named feline morbillivirus genotype 2 (FeMV-GT2), was isolated from urine of cats with urinary tract diseases. Whole genome sequencing showed about 78% nucleotide homology to known feline morbilliviruses. The virus was isolated in permanent cell lines of feline and simian origin. To investigate the cell tropism of FeMV-GT2 feline primary epithelial cells from the kidney, the urinary bladder and the lung, peripheral blood mononuclear cells (PBMC), as well as organotypic brain slice cultures were used for infection experiments. We demonstrate that FeMV-GT2 is able to infect renal and pulmonary epithelial cells, primary cells from the cerebrum and cerebellum, as well as immune cells in the blood, especially CD4⁺ T cells, CD20⁺ B cells and monocytes. The cats used for virus isolation shed FeMV-GT2 continuously for several months despite the presence of neutralizing antibodies in the blood. Our results point towards the necessity of increased awareness for this virus when clinical signs of the aforementioned organs are encountered in cats which cannot be explained by other etiologies.

Cats with IRIS stage 1 and 2 chronic kidney disease maintain body weight and lean muscle mass when fed food having increased caloric density, and enhanced concentrations of carnitine and essential amino acids

A prospective, randomised, 6-month feeding trial was performed in 28 adult cats with International Renal Interest Society (IRIS) stage 1 and 2 chronic kidney disease (CKD). All cats were assigned to either a control food: Royal Canin Renal Support A Feline, dry or a test food: Hill's Prescription Diet k/d Feline with chicken, dry. Food intake was recorded daily; body weight weekly; and serum, urine, dual-energy x-ray absorptiometry (DEXA) and body condition assessments were performed at 0, 1, 3 and 6 months. Twenty cats (9 control, 11 test group) completed the study according to protocol. Cats consuming control food had significant loss of body weight (n=14; mean, -13.0 per cent, P<0.0001) and lean body mass (LBM; mean, -11.1 per cent, P<0.0001) over the 6-month feeding period, whereas cats consuming test food had a significant increase in body weight (n=14; mean, 5.8 per cent, P=0.003) and no change in LBM (P=0.42). Cats consumed 23 per cent more calories (P=0.05) when fed test food (mean, 207.1 kcal/day) compared with cats fed control food (mean, 168.0 kcal/day). Serum creatinine increased at a faster rate (P=0.0004) in cats consuming control food compared with cats consuming test food. Cats consuming test food had increased caloric and essential amino acid intake, increased body weight, stable biomarkers of kidney function and maintained LBM compared with cats consuming control food.

Correlation of the severity of chronic kidney disease with serum inflammation, osteoporosis and vitamin D deficiency

Correlation of the severity of chronic kidney disease (CKD) with serum inflammation, osteoporosis and vitamin D deficiency was investigated. A total of 78 patients suffering from CKD who presented to the Union Hospital from December 2015 to December 2017 were selected randomly and divided into three groups based on the severity of the disease. Comparisons of interleukin-6 (IL-6), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), indicators of osteoporosis [serum phosphate, serum calcium and bone mineral density (BMD)], content of 25(OH)D, serum sodium, serum potassium and BUN were conducted among groups. The correlation of in vivo creatinine (Cr) with C-reactive protein (CRP), TNF-α, BMD and vitamin D deficiency were analyzed. With the aggravation of illness, IL-6, CRP, TNF-α, serum phosphate, serum sodium, serum potassium and blood urea nitrogen (BUN) were increased gradually, while serum calcium, BMD and vitamin D were decreased significantly (P<0.05). The content of Cr in patients suffering from osteoporosis was significantly higher than that in normal group (P<0.05). The Cr of patients in the group with abnormal CRP was significantly higher than that with normal CRP (P<0.05). Analysis showed that there is positive correlation between Cr and CRP (r=0.6961, P<0.001), as well as between Cr and TNF-α (r=0.8969, P<0.001); and negative correlation between Cr and BMD (r=0.5472, P<0.001), and between Cr and 25(OH)D (r=0.4733, P<0.001). The severity of CKD is correlated with serum inflammation, osteoporosis and vitamin D deficiency. The higher the severity of the illness, the worse the condition of osteoporosis will be.

A new perspective on the pathogenesis of chronic renal disease in captive cheetahs (Acinonyx jubatus)

The sustainability of captive cheetah populations is limited by high mortality due to chronic renal disease. This necropsy study, conducted on 243 captive cheetahs from one institution, investigated the relationships between focal palatine erosions, gastritis, enterocolitis, glomerulosclerosis, chronic renal infarcts, renal cortical and medullary fibrosis, and renal medullary amyloidosis at death. Associations between the individual renal lesions and death due to chronic renal disease and comparisons of lesion prevalence between captive bred and wild born and between normal and king coated cheetahs were also assessed. All lesions were significantly positively correlated with age at death. Renal medullary fibrosis was the only lesion associated with the likelihood of death being due to chronic renal disease, and cheetahs with this lesion were younger, on average, than cheetahs with other renal lesions. Alimentary tract lesions were not associated with amyloidosis. All lesions, except for palatine erosions, were more common in wild born than in captive bred cheetahs; the former were older at death than the latter. Having a king coat had no clear effect on disease prevalence. These results suggest that age and renal medullary fibrosis are the primary factors influencing the pathogenesis of chronic renal disease in captive cheetahs. Apart from amyloidosis, these findings are analogous to those described in chronic renal disease in domestic cats, which is postulated to result primarily from repetitive hypoxic injury of renal tubules, mediated by age and stress. Cheetahs may be particularly susceptible to acute renal tubular injury due to their propensity for stress and their extended life span in captivity, as well as their adaptation for fecundity (rather than longevity) and adrenaline-mediated high speed prey chases. The presence of chronic renal disease in subadult cheetahs suggests that prevention, identification and mitigation of stress are critical to the successful prevention of chronic renal disease in captive cheetahs.

Contrast-Enhanced Ultrasound Examination for the Assessment of Renal Perfusion in Cats with Chronic Kidney Disease

Background

Contrast‐enhanced ultrasound examination (CEUS) is a functional imaging technique allowing noninvasive assessment of tissue perfusion. Studies in humans show that the technique holds great potential to be used in the diagnosis of chronic kidney disease (CKD). However, data in veterinary medicine are currently lacking.

Objectives

To evaluate renal perfusion using CEUS in cats with CKD.

Animals

Fourteen client‐owned cats with CKD and 43 healthy control cats.

Methods

Prospective case‐controlled clinical trial using CEUS to evaluate renal perfusion in cats with CKD compared to healthy control cats. Time‐intensity curves were created, and perfusion parameters were calculated using off‐line software. A linear mixed model was used to examine differences between perfusion parameters of cats with CKD and healthy cats.

Results

In cats with CKD, longer time to peak and shorter mean transit times were observed for the renal cortex. In contrast, a shorter time to peak and rise time were seen for the renal medulla. The findings for the renal cortex indicate decreased blood velocity and shorter total duration of enhancement, likely caused by increased vascular resistance in CKD. Increased blood velocity in the renal medulla has not been described before and may be because of a different response to regulatory factors in cortex and medulla.

Conclusions and Clinical Importance

Contrast‐enhanced ultrasound examination was capable of detecting perfusion changes in cats with CKD. Further research is warranted to assess the diagnostic capabilities of CEUS in early stage of the disease process.

Role of artesunate in TGF‑β1‑induced renal tubular epithelial‑mesenchymal transdifferentiation in NRK‑52E cells

The implications of epithelial-mesenchymal transdifferentiation (EMT) have extended beyond the confines of renal fibrosis to renal tubulointerstitial fibrosis. It has been proposed that EMT may be one of the mechanisms involved in the pathogenesis of renal fibrosis. However, the underlying mechanisms remain unknown. Transforming growth factor (TGF)-β1 is considered to be an important cytokine which regulates the transdifferentiation of tubular epithelial cells into myofibroblasts in renal tubulointerstitial fibrosis. In the present study, normal rat kidney tubular epithelial cells (NRK-52E) were treated for 48 h with TGF-β1 (5 ng/ml) and different concentrations of artesunate (ART; 0.01, 0.1 and 1 µg/ml). Western blotting, reverse transcription-semi quantitative polymerase chain reaction analysis and immunofluorescence staining were used to evaluate the expression of bone morphogenetic protein (BMP)-7, uterine sensitization-associated gene (USAG)-1, E-cadherin, α-smooth muscle actin (α-SMA) and extracellular matrix collagen type I (Col I) mRNA. ART was able to attenuate renal injury in a unilateral ureteral obstruction model. However, its anti-fibrotic effect remains to be elucidated. In the present study, it was observed that ART was able to ameliorate the TGF-β1-induced alterations in cellular morphology. In addition, ART inhibited the TGF-β1-induced USAG-1 increase and the decrease in BMP-7. Treatment with ART markedly attenuated the TGF-β1-induced upregulation of α-SMA and downregulation of E-cadherin. Additionally, ART was able to significantly attenuate the deposition of interstitial collagens, including Col I. The results of the present study further verified the therapeutic efficacy of ART in TGF-β1-induced renal interstitial fibrosis. These findings indicated that ART may hold the potential to prevent chronic kidney diseases via the suppression of USAG-1 expression or by increasing BMP-7 expression.

[Evaluation of nutritional characteristics of commercial canned cat diets]

OBJECTIVE

To evaluate commercial complete canned cat foods according to their composition, labeling and nutritional characteristics.

MATERIALS AND METHODS

A total of 21 commercial complete canned compound feeds for adult cats were analyzed for crude nutrients, minerals, vitamins, selected amino acids and taurine. The analyzed parameters were compared to the internal set of standards of the European Pet Food Industry Federation (FEDIAF). The energy content was calculated and compared with the labeled recommendations regarding the amounts of diet that should be fed. Analyzed nutrients were compared with the labeled nutrients according to the regulations of the EU food and feed law (directive EU regulation 767/2009).

RESULTS

In many cases, the labeled feeding protocols did not match the calculated daily energy requirements. In eight complete foods, the recommended daily feed amounts were underestimated and four recommendations exceeded energy requirements of adult cats. In 12 complete foods, the calcium and phosphorus contents were threefold higher than the respective requirement. In 16 of 21 complete foods, substantial discrepancies were observed between the recommendations and the analyzed trace elements. In particular, selenium contents exceeded the selenium requirement more than threefold. The vitamin, arginine and taurine contents showed no significant discrepancies to the recommendations. With respect to the labeled nutrients, there were only minor deviations from the regulations of the European law.

CONCLUSION AND CLINICAL RELEVANCE

In general, healthy adult cats are adequately supplied with energy and nutrients when feeding commercial canned complete diets for cats. In cases of body weight loss or gain, the labelled feed amounts should be questioned. The high phosphorus contents are an issue of concern, because a high phosphorus intake can potentially increase the risk for urinary stones and particularly for older cats the risk for renal insufficiency. Furthermore, it is recommended to decrease the high selenium levels by the reduction of selenium-rich feed materials such as offal.

Intrinsic factors, adrenal gland morphology, and disease burden in captive cheetahs (Acinonyx jubatus) in South Africa

Adrenal gland weight (AW) and corticomedullary ratio (ACMR) are used as indicators of stress in animals. Captive cheetahs (Acinonyx jubatus) have higher ACMRs than free-ranging ones and stress has been linked to gastritis, amyloidosis, glomerulosclerosis, and myocardial fibrosis. We reviewed age, sex, body weight (BW), kidney weight (KW), and left AW and ACMR with necropsy findings in 51 South African captive cheetahs. Eleven common histopathologic lesions were counted for each animal as measure of its disease burden. Adrenal corticomedullary hyperplasia was significantly correlated with left AW and ACMR. Males had significantly higher AWs than females; other parameters showed no difference between the sexes. Disease burden, gastritis, and myocardial fibrosis were moderately correlated with adrenal morphology supporting prior evidence that gastritis and myocardial fibrosis are linked to stress. Glomerulosclerosis was not correlated with adrenal morphology and neither kidney nor liver amyloidosis contributed significantly to variation in AW or ACMR on multivariate analyses. Interstitial nephritis showed much stronger correlations with kidney and liver amyloidosis than gastritis. All three adrenal parameters were correlated with age; age was the only significant variable affecting ACMR on the multivariate analyses; and disease burden as well as systemic amyloidosis and kidney disease (except for fibrosis) showed moderate correlations with age. Age may, therefore, be important in the pathogenesis of disease in captive cheetahs, particularly of amyloidosis and kidney disease. None of the intrinsic measurements or adrenal parameters were sufficiently closely linked to disease to be used as ante-mortem proxies for disease burden or specific diseases. Zoo Biol. 36:40-49, 2017. © 2016 Wiley Periodicals, Inc.