Eastern equine encephalitis in puppies in Michigan and New York states

Abstract

Eastern equine encephalitis virus (EEEV) is classified as a select agent and is capable of causing mortality in humans and a number of veterinary species. Herein, we describe 3 cases of EEE in puppies in Michigan and New York. Two puppies were euthanized following an acute history of seizures and obtundation. A littermate of one of these puppies died 2 wk earlier following a history of anorexia and fever. All 3 puppies lacked significant gross anatomic lesions at autopsy and tested negative for rabies virus. In all 3 puppies, histologic examination revealed necrotizing, neutrophilic, lymphoplasmacytic meningoencephalitis with strong positive immunohistochemical labeling for EEEV antigen in neurons and glial cells. The diagnosis of EEE was confirmed by PCR in one puppy and by plaque reduction neutralization testing in the other 2 dogs. EEE is rare in dogs, and has only been reported in puppies. The initial clinical signs of EEE in puppies are typically nonspecific, including anorexia, fever, and diarrhea, but rapidly progress to severe neurologic disease characterized by seizures and recumbency. Although rare, EEE should be considered as a differential diagnosis for neurologic disease in puppies, especially after more common diseases, such as canine distemper, rabies, and toxoplasmosis have been ruled out.

Eastern Equine Encephalomyelitis in Michigan: Historical Review of Equine, Human, and Wildlife Involvement, Epidemiology, Vector Associations, and Factors Contributing to Endemicity

“…Suspected and confirmed cases of infection and death in equids (mostly horses, but occasionally others such as donkeys) and other domesticated animals were identified from reports from veterinary practitioners to the Michigan Department of Agriculture and Rural Development (MDARD), and through review of clinical and laboratory records. Brain tissues from equids were examined at the Veterinary Diagnostic Laboratory (VDL) at Michigan State University (MSU) for histopathology and immunohistopathology ( Williams et al 2000 , Schmitt et al 2007 , Andrews et al 2018 ). Before and after 2003, histopathology was done on brain tissues if the specimen was suitable.…”

“…Human cases of EEE have been reported previously ( MMWR 1980 , 1992 ; Davenport et al 1982 ; Deresiewicz et al 1997 ; Lindsey et al 2018 ), including a review of the outbreak in 2019 when 10 human cases in Michigan were reported ( Lindsey et al 2020 ). Case reports in various animal species ( McLean et al 1985 ; MMWR 1993 , 1995 ; Williams et al 2000 ; Andrews et al 2018 ; Thompson et al 2021 ) and risk analysis of equid and white-tailed deer outbreaks ( Ross and Kaneene 1995 , 1996 ; Schmitt et al 2007 ; Downs et al 2015 ) have been published previously. Additionally, there are at least two unpublished master’s theses dealing with the topic of EEE in Michigan ( Shaw 1976 , Solis 2000 ), and an important but unpublished report of studies of mosquito and bird involvement conducted from 1980 to 1982 ( Newson 1983 ).…”

Clinical Toxoplasmosis in Dogs and Cats: An Update

“…Also, non-infectious neurological diseases showing a wide range of signs are frequent in cats (30, 93) and dogs (94, 95). In dogs, CDV is an important cause of neurological disease, but other infectious agents include eastern equine encephalitis virus (96), S. neurona (97), and N. caninum (8, 85). Co-infections of T. gondii with viruses, like CDV, canine adenovirus type 1 and type 2, and canine parvovirus type 2 (7, 72), along with rickettsial bacteria (47) and protozoans, like Leishmania spp., N. caninum , and S. neurona (6, 15, 49, 98–100), can mask the infections, so clinicians need to pay attention to all variables.…”

Eastern Equine Encephalitis Virus in Mexican Wolf Pups at Zoo, Michigan, USA

“…Among the naturally occurring encephalitic alphaviruses, EEEV has the highest mortality rate in humans (50%–75%) and equids (70%–90%) ( 4 ). Additional reports exist of clinical disease in a wide variety of mammalian and avian species, including swine, cattle, white-tailed deer, alpacas, seals, domestic canids, pheasants, emus, penguins, and cassowary birds ( 5 – 10 ). Clinical signs of EEEV range from asymptomatic infection to severe and often fatal neurologic disease; signs may include pyrexia, anorexia, recumbency, diarrhea, ataxia, seizures, nystagmus, and head pressing.…”

“…Clinical signs of EEEV range from asymptomatic infection to severe and often fatal neurologic disease; signs may include pyrexia, anorexia, recumbency, diarrhea, ataxia, seizures, nystagmus, and head pressing. Previous reports of EEEV in domestic canids have been rare and have mainly been in young puppies <6 months of age ( 9 , 10 ). Serologic evidence suggests that exposure to EEEV in free-ranging gray wolves ( Canis lupus ) is low (0% of pups and 3% of adults) in Minnesota ( 11 ), where EEEV is uncommon.…”