Signalment:  

8-year-old, castrated male, domestic short hair, feline (Felis domestics).This cat was referred to the University Veterinary Hospital, University College Dublin with a two-month history of weight loss. It presented with periorbital alopecia, nasal discharge, pale mucus membranes and a heart murmur. Blood tests revealed a severe non-regenerative anaemia, neutropaenia and thrombocytopaenia.

Gross Description:  

The cat presented in poor body condition with pale mucus membranes. Focal areas of alopecia extended over both upper eyelids to the bases of both ears, and red crusted lesions were present over the upper eyelids and lateral canthuses (more extensive on the right). The right third eyelid was thickened and erythematous as were the nasal conchae. The nasal planum, particularly on the right, had a dry, crusty and flaky appearance. There was a small amount of serohaemorrhagic pericardial fluid. The mesenteric lymph nodes were enlarged and on sectioning contained mottled red and pale pink areas. The bone marrow was dark red in color and filled the marrow space.

Histopathologic Description:

Multifocal ulcers covered by serocellular crust are present on the anterior surface of the eyelid. There is a moderate perifollicular and mural follicular inflammatory infiltrate consisting of macrophages, occasional neutrophils, lymphocytes and plasma cells along with a large numbers of mast cells. Hair follicles often contain mites. Multiple large areas of ulceration covered by a serocellular crust are apparent on the conjunctival surface of the eyelid and moderate neutrophilic and lymphocytic infiltration is apparent in the underlying mucosa. Epithelial cells immediately adjacent to the ulcerated areas are enlarged and occasionally contain large eosinophilic to amphophilic intra-nuclear inclusion bodies with marginated chromatin. There are accompanying necrotic -�-�ghost epithelial cells. Additional histological lesions include an ulcerative lymphoplasmacytic rhinitis and bone marrow hypercellularity with a reduced erythroid ratio (not submitted).

Morphologic Diagnosis:  

1. Severe acute ulcerative conjunctivitis with intralesional intranuclear inclusion bodies consistent with feline herpesvirus infection.
2. Subacute ulcerative folliculitis with intralesional mites suggestive of Notoedres cati.

Condition:  

Feline Herpesvirus; Demodex sp.

Contributor Comment:  

Feline herpesvirus 1 (FHV-1) is a common, worldwide infection of domestic cats of high morbidity and low mortality. A member of the alphaherpes virus subfamily, latency often develops after infection.(2,6) Up to 90% of tested cats are seropositive for this virus.(6)

Most cats are infected as kittens, developing conjunctivitis, corneal ulceration or rhinitis of varying severity depending on viral strain and host susceptibility. The virus replicates in epithelial cells at temperatures below 37^o Celsius and so its preferential proliferation sites are peripheral locations such as ocular and nasal mucosa. The virus damages tissue by direct cytolysis during replication and secondarily by immune-mediated inflammation. Cytolysis results in corneal ulceration, conjunctivitis with ulceration and rhinitis with erosions. Immunemediated injury is less common and results in stromal keratitis. In primary infections the most common presenting lesion is conjunctivitis.(2,7)

Up to 80% of infected cats go on to develop virus latency, typically in the trigeminal nerve, from which latency associated transcripts of FHV-1 have been demonstrated. More recently, evidence of persistent low-grade viral infection has been demonstrated in the cornea.(2,6,7) In approximately 50% of carriers, reactivation of infection can occur either spontaneously or during periods of stress or corticosteroid administration. Classically, this is associated with centrifugal spread of the virus from the trigeminal nerve along the sensory nerves to the original epithelial site of invasion. Upon reactivation, viral shedding recommences and this can be with or without recrudescence of clinical signs. With reactivation, the most common presenting clinical sign is conjunctivitis.(2)

Notoedres cati (feline scabies) is a rare, highly contagious ectoparasite of cats causing alopecia with adherent crusts around the head and ears, particularly the ear pinna. Histologically the parasite triggers superficial dermatitis with eosinophil-rich perivascular inflammation.(3)

JPC Diagnosis:  

1. Eyelid: Blepharoconjunctivitis, ulcerative, focally extensive, severe with intranuclear viral inclusions.
2. Haired skin, eyelid follicles and sebaceous glands: Adult arthropod parasites, etiology consistent with Demodex cati.

Conference Comment:  

The contributor provides an excellent review of feline herpesvirus-1. Conference participants discussed the three most common clinical differential diagnoses for upper respiratory disease in cats, specifically feline viral rhinotracheitis (caused by FHV-1), feline calicivirus rhinitis (caused by feline calicivirus) and feline chlamydiosis (caused by Chlamydophila felis).(5) In general, feline viral rhinotracheitis manifests clinically as rhinitis, conjunctivitis and/or ulcerative keratitis; whereas, feline calicivirus often causes rhinitis, conjunctivitis, ulcerative gingivitis and stomatitis5 and signs of Chlamydophila felis infection are often limited to rhinitis and conjunctivitis. Participants noted that these differences in presentation can be helpful in making a clinical diagnosis.

Dr. Chris Gardiner, JPC consultant in veterinary parasitology, believes these arthropods are more consistent with Demodex rather than Notoedres cati and provided by following justification: -�-�The mites in this specimen are elongate and found within the hair follicles; whereas, Notoedres cati mites are dorsoventrally flattened, similar to other members of the Family Sarcoptidae, and are typically observed in the stratum corneum.(1,4) Additionally, Demodex spp. are the only parasitic mites in which all four pairs of appendages originate together. Notoedres mites, on the other hand, have two pairs of two appendages that originate together separated by a space from another two pairs of two appendages that originate together. (C.H. Gardiner, personal communication).

References:

1. Bowman, DD. Arthropods. In: Georgis Parasitology for Veterinarians. 9th ed. St. Louis, MO: Saunders Elsevier; 2009:64-66.
2. Gaskell R, Dawson S, Ramford A, Thiry E. Feline herpesvirus. Vet Res. 2007;38:337-354.
3. Ginn PE, Mansell JEKL, Rakich PM. Skin and appendages. In: Maxie MG, ed. Jubb, Kennedy and Palmers Pathology of Domestic Animals. 5th ed. vol. 1. Philadelphia, PA: Elsevier Saunders; 2007:721-722.
4. Hargis Am, Ginn PE. The integument. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary Disease. St. Louis MO: Elsevier Mosby; 2012:1043.
5. Lopez A. Respiratory system, mediastinum, and pleurae. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary Disease. St. Louis MO: Elsevier Mosby; 2012:473.
6. Maggs DJ. Update on pathogenesis, diagnosis and treatment of feline herpesvirus type 1. Clin Tech Small Anim Pract. 2005;20:94-101.
7. Wilcock BP. Eye and ear. In: Maxie MG, ed. Jubb, Kennedy and Palmers Pathology of Domestic Animals. 5th ed. vol. 1. Philadelphia, PA: Elsevier Saunders; 2007:490-491.

Click the slide to view.

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4-1. Eyelid

4-2. Eyelid, conjunctival surface

4-3. Eyelid, haired skin

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