Eastern equine encephalitis in 9 South American camelids.
Authors: Nolen-Walston Rose, Bedenice Daniela, Rodriguez Carlos, Rushton Steven, Bright Amy, Fecteau Marie-Eve, Short Diana, Majdalany Ron, Tewari Deepanker, Pedersen Douglas, Kiupel Matti, Maes Roger, Del Piero Fabio
Journal: Journal of veterinary internal medicine
Summary
# Eastern Equine Encephalitis in South American Camelids: An Emerging Clinical Concern Eastern equine encephalitis (EEE) virus, a mosquito-borne alphavirus responsible for severe and frequently fatal encephalitis across multiple mammalian species, had never been documented in South American camelids prior to this investigation. A retrospective analysis identified nine cases (eight alpacas and one llama, ranging from 3.5 weeks to 12 years of age) across the East Coast of the United States, with four animals under ten weeks old, predominantly presenting during late summer and autumn months. Clinical presentation was consistent with acute encephalitis—including fever, lethargy, ataxia, seizures, recumbency, torticollis, opisthotonus, and vestibular dysfunction—though notably, standard haematological parameters proved unreliable for diagnosis; of paramount concern, 89% of affected camelids died or required euthanasia within a mean timeframe of just two days, with no successful therapeutic interventions identified in any case. Confirmation relied upon alphavirus detection via immunohistochemistry and polymerase chain reaction of central nervous system tissue, alongside characteristic neuropathological findings of polioencephalitis with lymphocytic perivascular cuffing, gliosis, and intracytoplasmic viral inclusions within neurones and glial cells. For practitioners in endemic regions, EEE warrants consideration as a critical differential diagnosis in both young and adult camelids presenting with neurological disease; definitive diagnosis requires brain tissue histopathology combined with immunohistochemistry or PCR analysis, given the disease's rapid progression and uniformly poor prognosis.
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Practical Takeaways
- •In endemic areas, EEE must be considered in the differential diagnosis for young and adult camelids presenting with neurological signs, particularly during late summer and fall
- •The prognosis is grave with 89% mortality and rapid progression; no successful therapeutic interventions were identified in this series
- •Diagnosis requires brain tissue analysis using immunohistochemistry or PCR on CNS samples, as hematologic and routine CSF findings are not consistent; serological testing may also confirm infection
Key Findings
- •Nine South American camelids (8 alpacas, 1 llama) were naturally infected with EEE virus, representing first reported cases in this species
- •89% of infected camelids (8 of 9) died or were euthanized within mean of 2 days of presentation
- •Clinical signs included fever, lethargy, ataxia, seizures, recumbency, torticollis, opisthotonus, and vestibular signs consistent with encephalitis
- •EEE was confirmed by alphavirus detection via immunohistochemistry and PCR in CNS tissue showing polioencephalitis with lymphocytic perivascular cuffing and neuronal necrosis