Infectious diseases

image of Infectious diseases
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This chapter will focus on some of the more common causes of feline infectious diseases encountered in first-opinion practice, notably cat ’flu, chronic rhinosinusitis, feline infectious peritonitis, retroviral infections and toxoplasmosis.

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19.1 FHV infection. Severe conjunctivitis with associated symblepharon of the right eye and nasal discharge in a kitten. Severe ulcerative facial and nasal dermatitis in an adult cat. Skin biopsy samples have been taken, necessitating the suturing shown.
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19.2 FCV infection. Lingual ulcers in a kitten. Ulceration of the nasal planum in an adult cat.
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19.6 Effusive FIP. Distended abdomen caused by a large volume of peritoneal effusion, comprised of viscous straw-coloured proteinaceous fluid . Abdominal effusion and lesions typical of effusive FIP were present in the visceral peritoneum , including whitish fibrinous deposits on the spleen and liver (white arrows), intestinal granulomas (yellow arrow) and a thickened omentum.
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19.7 Atypical presentations of effusive FIP. Ventral oedema of the chin. Ventrodorsal radiograph with enlarged globoid cardiac silhouette due to a large volume of fibrinous pericardial effusion. Pericardial sac of a cat with a pericardial effusion due to FIP, opened on post-mortem examination following euthanasia. The large size of the sac surrounding the heart can be seen; the pericardial fluid was extensive and white fibrinous deposits can be seen within the sac at the top of the image.
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19.8 Ocular signs are common in non-effusive FIP. Uveitis in the left eye; note the colour change of the lateral iris from blue to brown (arrowed). Keratic precipitates or ‘mutton-fat deposits’ on the inner surface of the cornea of the right eye formed from fibrin and inflammatory cells. The left pupil in (b) is dilated due to chorioretinitis. (Courtesy of Dr Mark Billson, SASH, Sydney, Australia)
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19.10 Multiple renal nodules with renomegaly in non-effusive FIP. Cytology of an ultrasound-guided aspirate from a renal cortical nodule, demonstrating pyogranulomatous inflammation. L = lymphocyte; M = macrophage; N = neutrophil. (Diff-Quik; original magnification X1000 with oil immersion.)
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19.11 Light microscopy immunofluorescence preparation of peritoneal effusion from a cat with effusive FIP. Macrophages containing intracytoplasmic FCoV antigen fluoresce bright green. (Courtesy of A/Prof Jacqui Norris, University of Sydney)
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19.13 Rivalta’s test. The image shows a positive test on peritoneal fluid from a cat with effusive FIP. (Courtesy of Dr Dianne Addie)
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19.14 Referral for MRI may be indicated in cases suspected of having neurological manifestations of FIP. This MRI transaxial post-contrast FLAIR image shows hyperintensity (white) associated with the lateral ventricles, consistent with inflammation. Such periventricular hyperintensity has been described in cats with FIP. Differential diagnoses include viral or bacterial ependymitis, choroiditis and periventricular encephalitis or leucomalacia.
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19.15 Severe anaemia manifesting as white gums in a kitten with progressive FeLV infection.
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19.17 Lateral thoracic radiograph of a 15-year-old male neutered cat with cranial mediastinal lymphoma. The cat tested persistently positive for FeLV p27 antigen and had high levels of provirus on PCR. Note the dorsal tracheal elevation, caudal displacement of the carina and diffuse opacity in the cranial thorax. Repeat radiographs in the same cat taken after 9 days of chemotherapy (crisantaspase (-asparginase), vincristine, cyclophosphamide and prednisolone), showing remission of the lymphoma and normal chest radiography.
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19.18 FIV infection. Severe gingivostomatitis and faucitis. Anisocoria due to chronic uveitis (right eye); note the relatively increased iris pigmentation (arrowed).
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19.19 FIV-infected cats with advanced infection are susceptible to ectoparasitism. mites and egg. (Skin scrapings in paraffin oil, X40 objective lens.)
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19.20 Non-healing wound in an FeLV-positive cat; the definitive cause was not identified. The haircoat on the ventral abdomen is stained by exudates. Cats with non-healing wounds should be tested for FIV and FeLV infection. Other differentials for non-healing wounds include atypical bacterial infections (e.g. spp.), fungal infections, neoplasia, foreign bodies and corticosteroid therapy.
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19.21 Longitudinal section through a kidney removed from an FIV-infected cat with high-grade B cell renal lymphoma.
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19.23 Lateral thoracic radiograph showing multiple foci of increased opacity (alveolar infiltrates) in a cat with severe toxoplasmosis. (Courtesy of Dr Katherine Briscoe, University of Sydney)
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19.25 Multiple tachyzoites (arrowed) in a smear of abdominal fluid from a cat with FIP and toxoplasmosis. (Diff-Quik; original magnification X330.) (Courtesy of Dr Amy Lingard, University of Sydney) Immunohistochemical staining of a spinal cord sample from a cat with toxoplasmosis. There is positive (brown) staining of multiple, variably sized thin-walled cysts and of free tachyzoites within the neuropil.
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