Validity of aqueocentesis as a component of anterior uveitis investigation in dogs and cats

Clinicopathological and Molecular Analysis of Aqueous Humor for the Diagnosis of Feline Infectious Peritonitis

BACKGROUND

This study was designed to assess the diagnostic utility for FIP of cytology, protein measurement and RT-PCR for feline coronaviruses (FCoV) on aqueous humor (AH), since little information is currently available.

METHODS

AH samples (n = 85) were collected post-mortem from 13 cats with effusive FIP (E-FIP), 15 with non-effusive FIP (NE-FIP) and 16 without FIP, to perform cytology (n = 83) and RT-PCR (n = 66) and to calculate their sensitivity, specificity and positive and negative likelihood ratios (LR+ and LR-). The protein concentration was measured on 80 fluids.

RESULTS

The proportion of RT-PCR positive samples did not differ among groups, while positive cytology was more frequent in samples with FIP (p = 0.042) or positive RT-PCR (p = 0.007). Compared with other groups, the protein concentration was higher in samples with NE-FIP (p = 0.017), positive RT-PCR (p = 0.005) or positive cytology (p < 0.001). The specificity of cytology together with RT-PCR, cytology alone, RT-PCR alone and cytological proteinaceous background were 90.0%, 84.6%, 70.0%, 61.5%, and the LRs 3.48, 2.65, 1.83, 1.64, respectively. However, their sensitivities were low (34.8-63.0%) and their LR- high (0.60-0.72).

CONCLUSIONS

Based on the LR+, cytology and/or RT-PCR may support the diagnosis when the pre-test probability of FIP is high. The concentration of intraocular protein is a promising marker, especially in NE-FIP.

Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines

Feline coronavirus (FCoV) is a ubiquitous RNA virus of cats, which is transmitted faeco-orally. In these guidelines, the European Advisory Board on Cat Diseases (ABCD) presents a comprehensive review of feline infectious peritonitis (FIP). FCoV is primarily an enteric virus and most infections do not cause clinical signs, or result in only enteritis, but a small proportion of FCoV-infected cats develop FIP. The pathology in FIP comprises a perivascular phlebitis that can affect any organ. Cats under two years old are most frequently affected by FIP. Most cats present with fever, anorexia, and weight loss; many have effusions, and some have ocular and/or neurological signs. Making a diagnosis is complex and ABCD FIP Diagnostic Approach Tools are available to aid veterinarians. Sampling an effusion, when present, for cytology, biochemistry, and FCoV RNA or FCoV antigen detection is very useful diagnostically. In the absence of an effusion, fine-needle aspirates from affected organs for cytology and FCoV RNA or FCoV antigen detection are helpful. Definitive diagnosis usually requires histopathology with FCoV antigen detection. Antiviral treatments now enable recovery in many cases from this previously fatal disease; nucleoside analogues (e.g., oral GS-441524) are very effective, although they are not available in all countries.

Clinical Follow-Up and Postmortem Findings in a Cat That Was Cured of Feline Infectious Peritonitis with an Oral Antiviral Drug Containing GS-441524

This is the first report on a clinical follow-up and postmortem examination of a cat that had been cured of feline infectious peritonitis (FIP) with ocular manifestation by successful treatment with an oral multicomponent drug containing GS-441524. The cat was 6 months old when clinical signs (recurrent fever, lethargy, lack of appetite, and fulminant anterior uveitis) appeared. FIP was diagnosed by ocular tissue immunohistochemistry after enucleation of the affected eye. The cat was a participant in a FIP treatment study, which was published recently. However, 240 days after leaving the clinic healthy, and 164 days after the end of the 84 days of treatment, the cured cat died in a road traffic accident. Upon full postmortem examination, including histopathology and immunohistochemistry, there were no residual FIP lesions observed apart from a generalized lymphadenopathy due to massive lymphoid hyperplasia. Neither feline coronavirus (FCoV) RNA nor FCoV antigen were identified by quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunohistochemistry, respectively, in any tissues or body fluids, including feces. These results prove that oral treatment with GS-441524 leads to the cure of FIP-associated changes and the elimination of FCoV from all tissues.

2022 AAFP/EveryCat Feline Infectious Peritonitis Diagnosis Guidelines

CLINICAL IMPORTANCE

Feline infectious peritonitis (FIP) is one of the most important infectious diseases and causes of death in cats; young cats less than 2 years of age are especially vulnerable. FIP is caused by a feline coronavirus (FCoV). It has been estimated that around 0.3% to 1.4% of feline deaths at veterinary institutions are caused by FIP.

SCOPE

This document has been developed by a Task Force of experts in feline clinical medicine as the 2022 AAFP/EveryCat Feline Infectious Peritonitis Diagnosis Guidelines to provide veterinarians with essential information to aid their ability to recognize cats presenting with FIP.

TESTING AND INTERPRETATION

Nearly every small animal veterinary practitioner will see cases. FIP can be challenging to diagnose owing to the lack of pathognomonic clinical signs or laboratory changes, especially when no effusion is present. A good understanding of each diagnostic test's sensitivity, specificity, predictive value, likelihood ratio and diagnostic accuracy is important when building a case for FIP. Before proceeding with any diagnostic test or commercial laboratory profile, the clinician should be able to answer the questions of 'why this test?' and 'what do the results mean?' Ultimately, the approach to diagnosing FIP must be tailored to the specific presentation of the individual cat.

RELEVANCE

Given that the disease is fatal when untreated, the ability to obtain a correct diagnosis is critical. The clinician must consider the individual patient's history, signalment and comprehensive physical examination findings when selecting diagnostic tests and sample types in order to build the index of suspicion 'brick by brick'. Research has demonstrated efficacy of new antivirals in FIP treatment, but these products are not legally available in many countries at this time. The Task Force encourages veterinarians to review the literature and stay informed on clinical trials and new drug approvals.

An unusual case of eosinophilic uveitis in a cat

An 8-year-old female spayed domestic short-haired cat was examined for recurrent unilateral anterior uveitis of 5 month's duration. No underlying cause was found on infectious disease screening. The cat also had a 4-year history of allergic or immune-mediated skin disease that was controlled with corticosteroid injections followed by long-term oral cyclosporine therapy. Medical management with frequent topical anti-inflammatory drugs (prednisolone acetate 1% suspension, diclofenac 0.1% solution) controlled the intraocular inflammation; however, the uveitis would relapse when therapy was discontinued. Eventually, secondary glaucoma developed OD and the eye was enucleated. At the time of surgery, a complete blood count showed a mild eosinophilia. Histopathology revealed a marked panuveitis characterized by an abundant accumulation of mixed inflammatory cells, with a predominantly eosinophilic infiltrate in the anterior chamber, iris, ciliary body, and choroid. No etiologic agents were found on serial sections, and there were no cellular criteria for malignancy noted. Nine months after enucleation, the chronic dermatitis appeared to be in remission despite no further medical management. This is the first known report of a primarily eosinophilic uveitis in a cat with chronic allergic skin disease and may be considered an ocular variant of feline eosinophilic granuloma complex.

Comparison of the prevalence of Domestic Cat Hepadnavirus in a population of cats with uveitis and in a healthy blood donor cat population in the United Kingdom

OBJECTIVE

Domestic Cat Hepadnavirus (DCH) is a novel virus recently identified in the domestic cat. Currently, little is known regarding its clinical significance. The hepadnaviridae family includes the Hepatitis B Virus (HBV). Co-infection of HBV and Hepatitis C in humans increases the risk of uveitis. We aimed to determine whether DCH is present in the United Kingdom (UK) and whether DCH warrants investigation as a potential cause of uveitis in cats.

PROCEDURES

Clinical records from the Royal Veterinary College (RVC) and the Animal Health Trust (AHT) were reviewed for feline cases diagnosed with endogenous uveitis. A healthy control group was identified from cats presented to the RVC as blood donors. DNA was extracted from stored blood samples using commercially available kits. Polymerase chain reaction assays were performed to confirm the presence of feline DNA and to detect the presence of DCH DNA using previously described protocols.

RESULTS

Blood samples were available from 65 cats with endogenous uveitis and 43 healthy control cats. Two blood samples from cats with endogenous uveitis tested positive for the presence of DCH DNA. DCH DNA was not detected in the control group. There was no statistically significant difference between the prevalence of DCH between the groups.

CONCLUSIONS

Domestic Cat Hepadnavirus is present in the UK. This study failed to demonstrate a conclusive link between DCH and uveitis in cats, although further studies to investigate an association with other feline diseases are warranted.

A multicenter retrospective study into endogenous causes of uveitis in cats in the United Kingdom: Ninety two cases

PURPOSE

The purpose of this study was to investigate the most common causes of endogenous feline uveitis in a UK referral population and to investigate associations based on signalment.

METHODS

Retrospective multicenter cross-sectional study from 2010 to 2019 including cats presented to the Animal Health Trust and the Royal Veterinary College with clinical signs consistent with uveitis. Cats were included in analyzes if they had a full physical examination including an ophthalmic examination, complete blood count, serum biochemistry, and infectious disease testing for at least two diseases unless the diagnosis was found on clinical examination (eg, neoplasia).

RESULTS

A total of 92 cats were included in the study. The majority of cats presenting with uveitis were male (66.3%). The most common causes of endogenous uveitis were idiopathic uveitis (42/92 45.7%), feline infectious peritonitis (FIP) 15/92 16.3%), and lymphoma (10/92 10.9%). Fisher's exact test showed differences in breed across diagnosis groups (p = .002) with purebred cats being overrepresented in the lymphoma and FIP groups. Kruskal-Wallis test showed differences in median age across diagnosis groups (p < .001) with cats in the FIP group having the youngest age (median 1.4 years, interquartile range (IQR) 0.4-1.8 years) and cats in the neoplasia (primary or paraneoplastic) group having the oldest age (median 12.8 IQR 10.8-13.8). Idiopathic uveitis was unilateral in 56.1% of cases, and infectious causes were unilateral in 47.8% of cases.

CONCLUSIONS

The most common cause of endogenous uveitis in a population of cats in the UK was idiopathic uveitis, followed by FIP and lymphoma.

Diagnosis of Feline Infectious Peritonitis: A Review of the Current Literature

Feline infectious peritonitis (FIP) is a fatal disease that poses several challenges for veterinarians: clinical signs and laboratory changes are non-specific, and there are two pathotypes of the etiologic agent feline coronavirus (FCoV), sometimes referred to as feline enteric coronavirus (FECV) and feline infectious peritonitis virus (FIPV) that vary fundamentally in their virulence, but are indistinguishable by a number of diagnostic methods. This review focuses on all important steps every veterinary practitioner has to deal with and new diagnostic tests that can be considered when encountering a cat with suspected FIP with the aim to establish a definitive diagnosis. It gives an overview on all available direct and indirect diagnostic tests and their sensitivity and specificity reported in the literature in different sample material. By providing summarized data for sensitivity and specificity of each diagnostic test and each sample material, which can easily be accessed in tables, this review can help to facilitate the interpretation of different diagnostic tests and raise awareness of their advantages and limitations. Additionally, diagnostic trees depict recommended diagnostic steps that should be performed in cats suspected of having FIP based on their clinical signs or clinicopathologic abnormalities. These steps can easily be followed in clinical practice.

Utility of an immunocytochemical assay using aqueous humor in the diagnosis of feline infectious peritonitis

Objective

In cats suffering from feline infectious peritonitis (FIP) without effusion, antemortem diagnosis is challenging. Uveitis is common in these cats. It was the aim of this study to evaluate sensitivity and specificity of an immunocytochemical assay (ICC) in aqueous humor of cats suspected of having FIP.

Animals studied

The study included 26 cats with immunohistochemically confirmed FIP and 12 control cats for which FIP was suspected due to similar clinical or laboratory changes, but which suffered from other diseases confirmed via histopathology.

Procedures

All aqueous humor samples were collected postmortem by paracentesis. ICC was carried out as avidin–biotin complex method. Sensitivity, specificity, and the overall accuracy including 95% confidence intervals (95% CI) were calculated.

Results

Immunocytochemistry was positive in 16 of 25 cats with FIP and 2 of 11 control cats (one cat with lymphoma, one with pulmonary adenocarcinoma). Aqueous humor samples of one cat with FIP and of one control cat were excluded from statistical analysis. Sensitivity was 64.0% (95% CI: 42.5–82.0); specificity 81.8% (95% CI: 48.2–97.7); and overall accuracy 69.4% (95% CI: 51.9–83.7).

Conclusions

As false‐positive results occurred and specificity is most important in the diagnosis of FIP, the diagnostic utility of ICC in aqueous humor is limited. Further studies are required to clarify the origin of false‐positive ICC results.