Encephalitis in horses refers to inflammation of the brain, which can be caused by various infectious agents, including viruses, bacteria, and parasites. This condition affects the central nervous system and can lead to neurological symptoms such as ataxia, seizures, and changes in behavior. Common viral causes of equine encephalitis include Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), and West Nile Virus (WNV). Diagnosis often involves clinical evaluation, serological testing, and sometimes cerebrospinal fluid analysis. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, pathogenesis, clinical presentation, and management of encephalitis in horses.
CASALS J.A study by hemagglutination-inhibition test showed that 19 strains of eastern equine encephalitis virus grouped themselves in two main types, which have been designated North American and South American. The former consists of ten strains from the eastern half of the United States, from Massachusetts to Florida; Jamaica, the Dominican Republic, and, subject to confirmation, Thailand. The South American type comprises nine strains from Panama, Trinidad, British Guiana, Brazil, and Argentina. The strains were isolated from different natural hosts over a period of 30 years.
HAMMON WM, REEVES WC.In three cases of encephalitis in humans that occurred in the area where the newly described California virus was isolated from mosquitoes, serological evidence seemed to indict the California virus as the etiological agent. In the case of an infant with very severe disease, the serological evidence was convincing; the evidence was almost as strong in the case of a seven-year-old boy; the results in an adult were equivocal. Inapparent infection in man is quite common as indicated by neutralization tests on the sera of nearly 600 residents of California, but encephalitic manifestations of infec...
Hollyer JA, McGuinness E, Bowers LC, Didier ES, Giudice C, Perl DP, Fogarty U.A case of encephalitis of unknown origin in the horse was investigated. Postmortem examination findings revealed a nonsuppurative granulomatous meningoencephalitis in the right hemisphere of the cerebral cortex. Testing for West Nile virus, equine herpes virus, equine infectious anemia, , , and were negative. The horse had a titer for , and sections from the affected area of the brain tested positive for the organism using both polymerase chain reaction (PCR) and immunohistochemistry. Amplicons generated using PCR were sequenced, and genotype II was identified. This is the first case of gen...
Akimenko ZA, Ofitserov VI, Shaprov VV, Iastrebov SI.Homogeneous (according to PAGE) capsid and surface viral proteins were isolated from concentrated purified suspensions of tick-borne encephalitis and Venezuelan equine encephalomyelitis viruses by one-stage reversed-phase HPLC. The amino acid composition and the sequences of their N-terminal parts were determined.
Jennings SH, Wise AG, Nickeleit V, Maes RK, Cianciolo RE, Del Piero F, Law JM, Kim Y, McCalla AC, Breuhaus BA, Roberts MC, Linder KE.Polyomaviruses produce latent and asymptomatic infections in many species, but productive and lytic infections are rare. In immunocompromised humans, polyomaviruses can cause tubulointerstitial nephritis, demyelination, or meningoencephalitis in the central nervous system and interstitial pneumonia. This report describes 2 Standardbred horses with tubular necrosis and tubulointerstitial nephritis associated with productive equine polyomavirus infection that resembles BK polyomavirus nephropathy in immunocompromised humans.
Hay AN, Potter A, Lindsay D, LeRoith T, Zhu J, Cashwell S, Witonsky S, Leeth C.Sarcocystis neurona is the predominant etiological agent of the infectious equine neurologic disease, equine protozoal myeloencephalitis (EPM), which is prevalent in the United States. A wealth of knowledge about S. neurona biology and its life cycle has accumulated over the last several decades. However, much remains unknown about the aberrant equine host's immune response to S. neurona and the relatively high prevalence of exposure to the protozoa but relatively infrequent occurrence of clinical neurologic disease. Mouse models simulating EPM are commonly used to study the disease due to num...
Rakaki ME, van der Walt M, Williams J, Venter M.We detected Shuni virus in horses and ovine fetuses and Shamonda virus in a caprine fetus in South Africa. We identified a Shuni/Shamonda virus reassortant in a horse and Shuni/Caimito, Shamonda/Caimito, and Shamonda/Sango virus reassortants in Culicoides midges. Continued genomic surveillance will be needed to detect orthobunyavirus infections in Africa.
Peters M, Graf G, Pohlenz J.A 14-year-old standardbred mare with clinically suspected acute bronchitis was killed because of rapidly progressing central nervous disturbances. Necropsy revealed systemic granulomatous inflammation and vasculitis involving the lungs, thoracic lymph nodes, ribs, and liver. In the cerebrum there was a severe subacute bilateral encephalitis and malacia predominately affecting the white matter, and vasculitis with perivascular infiltration of lymphocytes, macrophages, and giant cells. A causative infectious agent could not be detected by Ziehl-Neelsen, Grocott, or Giemsa stains, by periodic aci...
Schmidt P, Meyer H, Hübert P, Hafner A, Andiel E, Grabner A, Dahme E.The detection of equine herpesvirus type 1 (EHV-1) in infected cell cultures, and in tissues taken at necropsy, by the in-situ hybridization technique is described. A 4.9 kb Bam HI fragment of EHV-1 vaccine strain RacH was used as a probe after labelling with [alpha-32P] thymidine 5'-triphosphate ([32P]TTP) or digoxigenin-deoxyuridine 5'-triphosphate (dUTP). Both probes specifically detected EHV-1 DNA in either cytospin or paraffin wax-embedded preparations of infected cells. The digoxigenin-labelled probe was further used to examine tissue sections of equine fetuses which had been aborted due...
León B, González G, Nicoli A, Rojas A, Pizio AD, Ramirez-Carvajal L, Jimenez C.Venezuelan Equine Encephalitis virus (VEEV) is an arboviral pathogen in tropical America that causes lethal encephalitis in horses and humans. VEEV is classified into six subtypes (I to VI). Subtype I viruses are divided into epizootic (IAB and IC) and endemic strains (ID and IE) that can produce outbreaks or sporadic diseases, respectively. The objective of this study was to reconstruct the phylogeny and the molecular clock of sequences of VEEV subtype I complex and identify mutations within sequences belonging to epizootic or enzootic subtypes focusing on a sequence isolated from a mare in C...
Scarratt WK, Furr MO, Robertson JL.A pregnant, miniature horse mare had clinical signs of hepatoencephalopathy and concurrent hypocalcemia. The signs included dullness, inappetence, blindness, head pressing, weakness, muscle fasiculations, uveitis, and urinary incontinence. Hepatic dysfunction and hypocalcemia were confirmed by serum biochemical analysis. The mare was treated successfully with a continuous infusion of Ringer solution, calcium gluconate, dextrose, B-complex vitamins, sodium ampicillin, and flunixin meglumine; topical administration of ophthalmic ointments; and decompression of the urinary bladder. Histologic exa...
