Ocular mycobacterial lesions in cats.

Ocular mycobacterial infections are an under-recognized cause of morbidity in the domestic cat. This study aimed to explore the distribution, histopathological appearance, and severity of feline ocular mycobacterial lesions, and to characterize the immune cell population with immunohistochemistry. Routine histological staining with hematoxylin and eosin, and Masson's trichrome, was performed to identify ocular lesions and assign an inflammation score based on the number of cells present. Acid-fast bacilli were detected with Ziehl-Neelsen, and immunohistochemistry for ionized calcium-binding adaptor protein-1 (Iba1), calprotectin, cluster of differentiation 3 (CD3), and Pax5 was undertaken on formalin-fixed paraffin-embedded tissue samples from 24 cases of ocular mycobacteriosis. Posterior or panuveitis with concurrent retinitis was identified in 20/24 cases (83%), with retinal detachment in 16/20 (80%) of these cases. Choroidal lesions had the highest median inflammation score. Ziehl-Neelsen-positive organisms were detected in 20/24 cases (83%), with the highest prevalence of acid-fast bacilli detected in choroidal lesions (16/20, 80%). Lesions were typically granulomatous to pyogranulomatous, characterized by abundant numbers of Iba1-positive macrophages, followed by calprotectin-positive granulocytes and monocytes, fewer T cells, and rarer B cells. However, where iritis was identified, inflammation was typically lymphoplasmacytic (11/16 cases, 69%). Where diagnostic testing was performed, tuberculosis (ie, infection with Mycobacterium bovis, Mycobacterium microti, or a nonspeciated Mycobacterium tuberculosis-complex pathogen) was diagnosed in 20/22 cats (91%), with Mycobacterium lepraemurium infection identified in the other 2/22 cats (9%). These results suggest the choroid is the primary site of lesion development in most cases of feline ocular mycobacteriosis, and inflammatory changes are associated with the presence of mycobacteria localized to ocular tissues.

Leukemia cutis as a prominent clinical sign in a dog with acute myeloid leukemia.

An eight-year-old male neutered crossbreed dog presented with erosive and ulcerative cutaneous lesions in the inguinal regions, the medial aspect of both thighs, and the stifles. Hematologic assessment revealed nonregenerative anemia, thrombocytopenia, and high numbers of neoplastic mononuclear cells with a variable degree of maturation. The mononuclear neoplastic cells, with nuclei measuring 10-20 microns in diameter, accounted for 57% of the nucleated blood cells. In addition, the blood contained increased numbers of mature neutrophils and monocytes with atypical morphology. Cytologic examination of the right popliteal lymph node found high numbers of large mononuclear cells with similar morphology to those in the peripheral blood. Flow cytometry of peripheral blood revealed expression by the mononuclear neoplastic cells of the pan-leukocyte marker CD45 and myeloid markers CD14, MAC387, and myeloperoxidase (MPO). These results confirmed a diagnosis of acute myeloid leukemia (AML). Computed tomography found moderate nodular hepatosplenomegaly and multifocal bi-cavitary lymphadenopathy. Histopathologic examination of biopsies from the cutaneous lesions identified infiltration of the dermis by intermediate to large neoplastic round cells. Further treatment was declined, and the owners elected euthanasia. Postmortem examination confirmed AML involvement in the bone marrow, peripheral and intracavitary lymph nodes, heart, liver, kidney, and skin. Neoplastic cells in the bone marrow and skin showed positive immunolabeling for ionized calcium-binding adaptor protein 1 and MPO. To the best of our knowledge, this is the first report of ulcerative cutaneous lesions observed among the presenting clinical signs in a dog with AML and secondary leukemia cutis.

Development of an enzyme-linked immunosorbent assay for the diagnosis of feline tuberculosis.

Cases of feline tuberculosis (TB) can be challenging to diagnose. Currently, this is achieved through a combination of mycobacterial culture, polymerase chain reaction (PCR), or interferon-gamma release assay (IGRA); however, these each have limitations. There is limited data regarding the use of humoral immunodiagnostics for TB in cats. Therefore, we sought to develop an enzyme-linked immunosorbent assay (ELISA) to further facilitate the diagnosis of feline TB. A comparative PPD (purified protein derivative) antibody ELISA was optimised for use on serum and plasma, and was tested against samples from 14 cats with culture-confirmed TB and 24 uninfected controls. Selection of an appropriate positive cut-off value based on receiver-operator characteristic curve analysis gave test sensitivity of 64.3 % and specificity of 100 %. When tested on further samples from cats with strongly suspected mycobacteriosis, 32.9 % (23/70) were antibody positive. Notably, positive results were recorded in cats that failed to respond to the IGRA, and in one PCR and IGRA negative cat. No positive responses were identified in cats with non-tuberculous mycobacterial infections, or with non-mycobacterial diseases (n = 12). Therefore, antibody-based diagnostics may be useful adjunctive tests for cases of TB missed by the IGRA, helping protect both feline and, in turn, human health.

Ocular Tuberculosis: More than 'Of Mice and Men'.

Tuberculosis (TB), caused by infection with members of the Mycobacterium tuberculosis-complex, is one of the oldest known infectious disease entities, resulting in the death of millions of humans each year. It also results in a substantial degree of morbidity and mortality in animal species. Extrapulmonary TB is well recognized in humans, and the eye is one site that can be affected. Studies seeking to understand ocular TB have often relied on animal models; however, these have their limitations and may not truly reflect what happens in humans. We wish to raise awareness among ophthalmologists and vision scientists of naturally occurring cases of ocular TB in animals, namely cattle and domestic cats, and the possibilities of gaining further understanding of this presentation of TB by adopting a collaborative approach. This will hopefully improve outcomes for both human and animal patients.

Recognition of recombinant interferon-gamma from Felidae species by anti-cat antibodies.

Mycobacterial infections cause a reasonable burden of morbidity and mortality in global feline populations, many of which are 'Vulnerable' or 'Endangered'. Identifying these infections may facilitate efforts to protect these animals. An interferon-gamma (IFNγ) release assay (IGRA) to diagnose mycobacteriosis in domestic cats has been adapted for use in lions; however, the development of species-specific antibodies may be laborious. Therefore, we investigated whether anti-cat IFNγ antibodies can bind to recombinant IFNγ (rIFNγ) from other Felidae species, permitting use of the feline IGRA in a wider range of felids. Unique Felidae IFNγ protein sequences and their corresponding coding nucleotide sequence were identified from online databases; plasmids with an IFNγ-gene insert were synthesised to transform E. coli-DH5α and subsequently transfect HEK 293 T cells to secrete rIFNγ. Enzyme-linked immunosorbent assay using a commercial anti-cat IFNγ kit was performed to detect rIFNγ from Felidae, the domestic dog and cattle. Five unique rIFNγ Felidae proteins were synthesised; anti-cat IFNγ antibodies were able to bind to all five proteins, while cross-reactivity with canine and bovine rIFNγ was negligible. This suggests that anti-cat IFNγ antibodies are sufficient for detection of IFNγ across other Felidae species, namely the lion, tiger, cheetah, cougar, Iberian lynx and the Canadian lynx.

Diagnostic accuracy of the interferon-gamma release assay (IGRA) for cases of feline mycobacteriosis.

The aim of this study was to evaluate the sensitivity and specificity of the interferon-gamma release assay (IGRA) for diagnosing infections with members of the Mycobacterium (M.) tuberculosis-complex (MTBC) and non-tuberculous mycobacteria (NTM) in domestic cats, and to generate defined feline-specific cut-off values using receiver operating characteristic (ROC) curve analysis to improve test performance. Records of 594 cats that had been tested by IGRA were explored to identify individuals that had a culture and/or polymerase chain reaction (PCR)-confirmed case of mycobacterial disease, and those that had a final diagnosis of non-mycobacterial disease. A total of 117 cats - 80 with mycobacterial disease and 37 diagnosed with a condition other than mycobacteriosis - were identified for further detailed analysis. This population was used to estimate test sensitivity and specificity, as well as likelihood ratios for the IGRA to correctly identify a cat with or without mycobacterial disease. Agreement between IGRA results and culture/PCR using current and proposed new cut-off values was also determined. ROC analysis of defined confirmed infected and non-mycobacterial disease control cats allowed an adjustment of current test cut-offs that increased the overall test sensitivity for MTBC infections from 83.1 % (95 % confidence interval [CI]: 71.5-90.5 %) to 90.2 % (95 % CI: 80.2-95.4%), and M. bovis infection from 43 % (95 % CI: 28.2-60.7%) to 68 % (95 % CI: 51.4-82.1%) while maintaining high test specificity (100 % in both cases). Overall agreement between IGRA results and culture/PCR, while recognising that neither culture nor PCR tests have perfect sensitivity, improved from weak (κ = 0.57) to moderate (κ = 0.71) using new proposed IGRA test cut-off values. Application of these results, based upon the statistical analysis of accumulated test data, can improve the diagnostic performance of the feline IGRA, particularly for identifying infections with M. bovis, without compromising specificity.

Serial Interferon-Gamma Release Assay (IGRA) Testing to Monitor Treatment Responses in Cases of Feline Mycobacteriosis.

The interferon-gamma release assay (IGRA) is used to diagnose cases of feline mycobacteriosis, but the use of serial testing to monitor treatment responses has not been evaluated in this species. From a population of cats that underwent IGRA testing for diagnostic investigation, individuals were identified with a pre- and end-of-treatment IGRA that passed control thresholds. The number of cats which reverted to negative at the end-of-treatment IGRA, changes in paired antigen-specific optical density (OD) values and differences in the pre-treatment antigen-specific OD values for those which underwent reversion were compared. Factors to explain reversion or recurrence of disease post-treatment were explored. Four of 18 cats (22%) reverted to negativity at the point of clinical resolution (p = 0.33), there was no difference in paired antigen-specific OD values (p ≥ 0.12), and cats that reverted did not have a lower baseline OD value (p = 0.63). No statistically significant factors were identified to predict reversion (p ≥ 0.08). Remaining positive at the end of treatment IGRA was not associated with recurrence of disease post-treatment (p = 0.34). Overall, these data suggest there is limited value in the use of the IGRA to monitor treatment responses in cats.

Systemic Mycobacterium kansasii Infection in Two Related Cats.

Mycobacterial infections are a major concern in veterinary medicine because of the difficulty achieving an etiological diagnosis, the challenges and concerns of treatment, and the potential zoonotic risk. Mycobacterium kansasii, a slow-growing non-tuberculous mycobacteria, causes disease in both humans and animals. While infections have been well described in humans, where it may be misdiagnosed as tuberculosis, there are fewer reports in animals. Only four cases have been reported in the domestic cat. This case report describes systemic M. kansasii infection in two sibling indoor-only cats that presented two and half years apart with cutaneous disease that was found to be associated with osteolytic and pulmonary pathology. Infection with M. kansasii was confirmed in both cats by polymerase chain reaction on fine-needle aspirate of a lumbosacral soft tissue mass in one cat and on a tissue punch biopsy of a skin lesion in the other; interferon-gamma release assay inferred M. avium-complex and M. tuberculosis-complex infection in the two cats, respectively. Both patients made a full recovery following antimicrobial therapy with rifampicin, azithromycin, and pradofloxacin (plus N-acetyl cysteine in cat 2). This report highlights successful treatment of systemic M. kansasii mycobacteriosis in the cat and the challenge of accurately diagnosing this infection.