Primary immunodeficiencies of dogs and cats

Candida tropicalis infectious endocarditis in a dog with a patent ductus arteriosus

A 6-month-old male intact miniature Australian Shepherd presented for surgical consultation for a previously diagnosed patent ductus arteriosus. Echocardiogram revealed a patent ductus arteriosus and a hyperechoic oscillating lesion within the main pulmonary artery. Blood cultures and eventual post-mortem examination revealed Candida tropicalis endocarditis. This case report highlights a rare case of fungal endocarditis with both echocardiographic and post-mortem findings.

Histoplasma capsulatum, Toxoplasma gondii, Bartonella henselae and Bartonella clarridgeiae coinfections in an indoor-only Siamese cat

Case summary

A 6-year-old male castrated Siamese cat was referred for acute-onset blindness and mydriasis. Physical examination revealed serous retinal detachment with panuveitis and systemic hypertension. Abdominal ultrasound showed suspected dilation of the cisterna chyli and abdominal lymphadenopathy. Aspirates of mesenteric lymph nodes revealed intrahistiocytic yeast organisms with mild-to-moderate pyogranulomatous inflammation. Fungal culture and ITS1 sequencing of the lymph node aspirates confirmed infection with Histoplasma capsulatum. PCR performed on whole blood was positive for Bartonella henselae and Bartonella clarridgeiae, and Toxoplasma gondii IgG and IgM antibodies were detected in serum. The cat was prescribed prednisolone (0.5 mg/kg PO q24h), itraconazole (10 mg/kg PO q24h), clindamycin (13 mg/kg PO q12h), amlodipine (0.625 mg PO q24h), prednisolone acetate 1% drops (q6h) and ophthalmic lubricant for both eyes (q6h). The cat was doing well at home after 2 weeks of prednisolone, itraconazole and clindamycin administration, and no abnormalities were detected on repeat abdominal ultrasound 3 months later. The retinal detachment showed mild-to-moderate improvement at that time, but vision was not regained.

Relevance and novel information

This is the first report of coinfection of H capsulatum, T gondii, B henselae and B clarridgeiae in an indoor-only cat living in a H capsulatum non-enzootic area with no known travel history.

Vaccination of Immunocompromised Cats

Immunocompromise is a common condition in cats, especially due to widespread infections with immunosuppressive viruses, such as feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV), but also due to chronic non-infectious diseases, such as tumours, diabetes mellitus, and chronic kidney disease, as well as treatment with immunosuppressive drugs, such as glucocorticoids, cyclosporins, or tumour chemotherapy. In this review, the European Advisory Board on Cat Diseases (ABCD), a scientifically independent board of experts in feline medicine from eleven European countries, discusses the current knowledge and rationale for vaccination of immunocompromised cats. So far, there are few data available on vaccination of immunocompromised cats, and sometimes studies produce controversial results. Thus, this guideline summarizes the available scientific studies and fills in the gaps with expert opinion, where scientific studies are missing. Ultimately, this review aims to help veterinarians with their decision-making in how best to vaccinate immunocompromised cats.

Feline leukocyte adhesion (CD18) deficiency caused by a deletion in the integrin β2 (ITGB2) gene

BACKGROUND

Leukocyte adhesion deficiency (LAD) or CD18 deficiency is an autosomal recessive immunodeficiency which has been described in people, cattle, dogs, and knockout mice.

OBJECTIVES

The study goals were to characterize the clinicopathologic, immunologic, and molecular genetic features of feline LAD (FLAD) in a neutered male adult Domestic Longhair cat with severe leukocytosis and recurrent infections.

METHODS

Flow cytometry evaluated surface expression of CD18 on neutrophils. In vitro functional assays assessed CD18-dependent neutrophil adhesion and T-cell proliferation. Genomic DNA and cDNA were used to identify a causative mutation in the coding sequence of the integrin β₂ subunit (ITGB2) gene.

RESULTS

The affected cat developed periodontitis during the first months of life followed by recurrent infections poorly responsive to antibiotic therapy, accompanied by extreme neutrophilia. Neutrophils from the proband, compared to feline controls, did not express any CD18 on the cell surface. Adhesion of affected neutrophils was severely impaired with and without phorbol-myristate-acetate activation. The proband's T-cells proliferated weakly to 1 pg but normally to 100 pg staphylococcal enterotoxin A, suggesting a CD18-independent T-cell response at higher doses. Molecular genetic analysis of the ITGB2 gene revealed a 24 bp deletion at the exon 2 to intron 2 boundary (c.46_58 + 11del), predicting premature translational termination due to abnormal splicing of exon 1 to exon 3 or 4.

CONCLUSIONS

Feline LAD exhibits features similar to LAD in other species. However, clinical episodes in FLAD appeared milder allowing for an extended life expectancy under long-term antimicrobial therapy, possibly due to an alternative, CD18-independent T-cell proliferation pathway.

Cats are not small dogs: is there an immunological explanation for why cats are less affected by arthropod-borne disease than dogs?

It is widely recognized that cats appear to be less frequently affected by arthropod-borne infectious diseases than dogs and share fewer zoonotic pathogens with man. This impression is supported by the relative lack of scientific publications related to feline vector-borne infections. This review explores the possible reasons for the difference between the two most common small companion animal species, including the hypothesis that cats might have a genetically-determined immunological resistance to arthropod vectors or the microparasites they transmit. A number of simple possibilities might account for the lower prevalence of these diseases in cats, including factors related to the lifestyle and behaviour of the cat, lesser spend on preventative healthcare for cats and reduced opportunities for research funding for these animals. The dog and cat have substantially similar immune system components, but differences in immune function might in part account for the markedly distinct prevalence and clinicopathological appearance of autoimmune, allergic, idiopathic inflammatory, immunodeficiency, neoplastic and infectious diseases in the two species. Cats have greater genetic diversity than dogs with much lower linkage disequilibrium in feline compared with canine breed groups. Immune function is intrinsically related to the nature of the intestinal microbiome and subtle differences between the canine and feline microbial populations might also impact on immune function and disease resistance. The reasons for the apparent lesser susceptibility of cats to arthropod-borne infectious diseases are likely to be complex, but warrant further investigation.

Mastitis caused by Mycobacterium kansasii infection in a dog

A 2-year, 7-month-old female Chihuahua was admitted for a mammary mass measuring one cm in diameter. The dog had a history of demodicosis for 4 months and showed signs of pseudopregnancy at the time of the visit. Cytologic examination of an aspirate of the mass revealed a large number of macrophages containing nonstaining bacterial rods, which were acid-fast in a Ziehl-Neelsen stain, suggesting mycobacterial infection. Histologic examination of the mass revealed a pyogranulomatous mastitis characterized by an infiltration with macrophages containing acid-fast bacteria. Mycobacterium kansasii was subsequently cultured and identified by PCR. Surgical excision of the mass resulted in the growth of other dermal masses, but antimycobacterial treatment with rifampin and clarithromycin resolved these masses within 1 month. Three months after discontinuation of the treatment, similar organisms were found in aspirates of the enlarged bilateral inguinal lymph nodes by cytologic examination. Despite antimycobacterial treatment for another 4 months, there was no improvement and demodicosis also recurred. The dog eventually died of lymphoma 5 months after the relapse of mycobacterial infection. Although M kansasii is considered an important pathogen for pulmonary and cutaneous disease in people, there is only one report in a dog with an infection in a pleural effusion. As both adult-onset demodicosis in dogs as well as mycobacterial infection in people have been associated with T-lymphocyte deficiency, the M kansasii infection in this dog may have been associated with a condition of immune compromise.