Abstract
Eosinophilic meningoencephalitis (EME) has been described in various species of animals and in humans. In dogs it has been associated with protozoal infections, cuterebral myiasis and various other aetiologies. Ten cases of idiopathic eosinophilic meningoencephalitis have been reported in dogs and one in a cat where the origin was uncertain or unknown. The dogs were all males, of various breeds but with a predominance of Golden Retrievers and Rottweilers; they generally had a young age of onset. Two cases with no apparent underlying aetiology were diagnosed on post mortem examination. The 18-month-old, male Boerboel presented with sudden onset of cerebellar ataxia, as well as various asymmetrical cranial nerve deficits of 2 weeks' duration and without progression. Haematology revealed a peripheral eosinophilia. Necropsy showed extreme generalised congestion especially of the meninges and blood smear and histological sections of various tissues showed intravascular erythrocyte fragmentation with the formation of microcytes. Histopathology revealed severe diffuse cerebrocortical subarachnoidal meningitis and submeningeal encephalitis, the exudate containing variable numbers of eosinophils together with neutrophils and mononuclear cells. There was also deeper white matter and hippocampal multifocal perivascular mononuclear encephalitis and multifocal periventricular malacia, gliosis and phagocytosis of white matter. The cerebellum, brain stem and spinal c showed only mild multifocal oedema or scattered occasional axon and myelin degeneration respectively, with no inflammation. Immunohistochemical staining of central nervous tissue for Toxoplasma gondii failed to show any antigen in the central nervous tissue. Ultrastructure of a single submeningeal suspected parasitic cyst showed it to be chromatin clumping within a neuron nucleus indicating karyorrhexis. Gram stain provided no evidence of an aetiological agent. The 3-year-old Beagle bitch had a Caesarian section after developing a non-responsive inertia 8 days prior to presentation. This animal's clinical signs included status epilepticus seizures unrelated to hypocalcaemia and warranted induction of a barbiturate coma. She died 4 hours later. Post mortem and histopathological findings in the brain were almost identical to those of the Boerboel and she also showed histological evidence of recent active intravascular haemolysis with microcyte formation. Rabies, distemper and Neospora caninum immunohistochemical stains were negative in the brains of both dogs. Immunohistochemical staining of the cerebral and meningeal exudates of the Beagle for T- and B-lymphocyte (CD3 and CD79a) markers showed a predominance of T-lymphocytes with fewer scattered B lymphocytes. A possible allergic response to amoxicillin/clavulanate is considered, as this appeared to be the only feature common to the recent history of both animals. An overview of EME in humans, dogs and cats is given and the previously published cases of idiopathic EME in dogs and the single published cat case are briefly reviewed.
Highlights
Eosinophilic meningoencephalitis (EME) is diagnosed in humans and animals when neurological disease is associated with eosinophilic pleocytosis, which is the presence of increased numbers of eosinophils in the cerebrospinal fluid (CSF)
In a series of 93 dogs with neurological disease, eosinophilic pleocytosis was found in single cases of cryptococcosis (80% of the white cells counted in the CSF were eosinophils), toxoplasmosis (2.5 %), infarction of the caudate nucleus (6 %), cerebrocortical infarction (7 %), cerebral lymphosarcoma (1.5 %), in 4 dogs with granulomatous encephalitis (23.5 %), and in 5 dogs with tumours of the spinal and epidural tissues (1.4 %)[32]
Meningoencephalitis with eosinophilic pleocytosis has been recognised in aberrant migration of Angiostrongylus cantonensis in dogs, protothecal meningoencephalitis, distemper virus, rabies virus and bacterial infections[9,27,28,31]
Summary
Eosinophilic meningoencephalitis (EME) is diagnosed in humans and animals when neurological disease is associated with eosinophilic pleocytosis, which is the presence of increased numbers of eosinophils in the cerebrospinal fluid (CSF). Cerebral sections showed marked subarachnoidal meningitis extending down the sulci and with an exudate containing few to numerous eosinophils, as well as neutrophils, some lymphocytes, macrophages and a few plasma cells (Fig. 2). Nine days after the Caesarian, and 4 days after cessation of antibiotic treatment, the bitch became anorexic despite her rectal temperature being normal (reference range 36.5–39.5 C), the surgical wound was assessed to be healing well, only a small amount of pigmenturia was observed and there was no vaginal discharge She was enticed to eat with tinned food, after which she went outside, barked at another dog, returned inside, collapsed, and subsequently started to have seizures. The spleen was noticeably fairly bloodless in the red pulp, which had scattered megakaryocytes
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