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Topic:Encephalitis
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.
Ocular Halicephalobus (syn. Micronema) deletrix in a horse. Ocular contents from a horse with a 4-week history of severe unilateral uveitis were submitted for histopathologic examination. A severe unilateral granulomatous chorioretinitis with intralesional Halicephalobus deletrix was diagnosed. The horse developed progressive neurologic signs several days following the surgery to remove ocular contents and implant a prosthesis and was subsequently euthanatized. A severe multifocal granulomatous encephalitis with intralesional H. deletrix, localized primarily to the optic chiasm, thalamus, and brain stem, was diagnosed from tissues acquired at necropsy....
Presence of CD4+ and CD8+ T cells and expression of MHC class I and MHC class II antigen in horses with Borna disease virus-induced encephalitis. Tissues from 9 horses and 1 donkey suffering from natural Borna disease were investigated immunomorphologically. Lymphocytic inflammatory reactions and increased expressions of MHC class I and class II antigen were found in the brain as well as in the trigeminal and olfactory system. Perivascular inflammatory infiltrates were dominated by CD4+ T cells, whereas the majority of CD8+ T cells were disseminated intraparenchymally. No evidence of inflammation was found in the retina. Borna disease virus proteins and nucleic acids were present in the hippocampus, thalamus and medulla oblongata in all...
Borna disease–neuropathology and pathogenesis. Natural BD is a nonpurulent acute/subacute encephalitis of horses and sheep with a propensity to involve the olfactory and limbic systems, and the brain stem. The inflammation is concentrated primarily in the gray matter, but subcortical white matter may also be affected. Experimental BD can be produced in a series of animals from birds to primates. The neuropathology after experimental infection is similar to that in natural disease but the inflammatory changes are more diffuse. In the rat and mouse, a persistent/tolerant infection can also be induced, in which inflammatory changes are conspi...
Emergence of eastern encephalitis in Massachusetts. The 20th century emergence in Massachusetts of zoonotic eastern encephalitis was interpreted in terms of recorded environmental change. The main mosquito vector of the infection, Cs. melanura, appears to have been scarce in eastern North America before the 1930s. Its relative scarcity resulted from destruction of the swamps that had been lumbered or drained for farming in the 18th and 19th centuries. When swamps matured once again early in the 1900s, the formation of subsurface pools of water beneath mature trees would have increased the availability of breeding sites for this mosquito. Transm...
Structural protein relationships among eastern equine encephalitis viruses. We have re-evaluated the relationships among the polypeptides of eastern equine encephalitis (EEE) viruses using SDS-PAGE and peptide mapping of individual virion proteins. Four to five distinct polypeptide bands were detected upon SDS-PAGE analysis of viruses: the E1, E2 and C proteins normally associated with alphavirus virions, as well as an additional more rapidly-migrating E2-associated protein and a high M(r) (HMW) protein. In contrast with previous findings by others, the electrophoretic profiles of the virion proteins of EEE viruses displayed a marked correlation with serotype. The pro...
In-situ hybridization for demonstration of equine herpesvirus type 1 DNA in paraffin wax-embedded tissues and its use in horses with disseminated necrotizing myeloencephalitis. 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...
Medically important arboviruses of the United States and Canada. Of more than 500 arboviruses recognized worldwide, 5 were first isolated in Canada and 58 were first isolated in the United States. Six of these viruses are human pathogens: western equine encephalitis (WEE) and eastern equine encephalitis (EEE) viruses (family Togaviridae, genus Alphavirus), St. Louis encephalitis (SLE) and Powassan (POW) viruses (Flaviviridae, Flavivirus), LaCrosse (LAC) virus (Bunyaviridae, Bunyavirus), and Colorado tick fever (CTF) virus (Reoviridae, Coltivirus). Their scientific histories, geographic distributions, virology, epidemiology, vectors, vertebrate hosts, transm...
Immunogens of encephalitis viruses. The equine encephalitis viruses are members of the genus Alphavirus, in the family Togaviridae. Three main virus serogroups represented by western (WEE), eastern (EEE) and Venezuelan equine encephalitis (VEE) viruses cause epizootic and enzootic infection of horses throughout the western hemisphere. All equine encephalitis viruses are transmitted through the bite of an infected mosquito. The first equine encephalitis virus vaccines were produced by virus inactivation. Problems with inadequate inactivation, which may have caused a major epidemic/epizootic of VEE in central America and Texas in ...
Diffuse cerebral encephalopathy associated with hydrocephalus and cholesterinic granulomas in a horse. Cholesterinic granulomas, commonly found at necropsy in aged horses, may cause neurologic signs by obstructing the interventricular foramina, resulting in hydrocephalus. Diffuse cerebral disease in horses may not always result in rapid progression of clinical signs. Intermittency of neurologic signs may be associated with intermittent increases in CSF pressure.
Circulation of eastern equine encephalitis, western equine encephalitis, Ilhéus, Maguari and Tacaiuma viruses in equines of the Brazilian Pantanal, South America. Neutralizing antibodies to EEE (6.7%), WEE (1.2%), ILH (26.6%), MAG (28.2%) and TCM (15.7%) viruses were found in sera of 432 equines of the Brazilian Pantanal, area where undiagnosed horse deaths are frequently observed. A 4-fold rise in CF titer to EEE virus was detected in acute and convalescent sera of an encephalitis horse sacrificed in 1992. Antibodies to EEE, ILH, MAG and TCM viruses were detected in horses less than 2 years old indicating recent circulation of these viruses in the Pantanal. The evidence of recent equine encephalitis associated with rising CF titer to EEE warrants a mor...
Experimental equine leukoencephalomalacia, toxic hepatosis, and encephalopathy caused by corn naturally contaminated with fumonisins. A study to evaluate the effects of dietary fumonisin B1 was conducted using 6 ponies (4 test and 2 control). A ration naturally contaminated with fumonisin B1 was fed in 3 phases: 1) 44 ppm fumonisin B1, 2) less than 1 ppm fumonisin B1, and 3) 88 ppm fumonisin B1. All ponies were monitored daily, weighed weekly, and limit fed at a rate of 0.8% body weight plus hay. Feed intake was measured daily, and a serum chemistry panel was completed once or twice weekly. Four to 7 days after initiation of the trial (Phase 1), all 4 test ponies had decreased feed consumption, and selected serum chemistry p...
Eastern equine encephalitis virus in Ohio during 1991. During August and September of 1991, an epizootic of eastern equine encephalitis (EEE) virus in horses occurred in Wayne and Holmes countries, OH. This was the first recorded epizootic of EEE virus in the state. Twelve horses were confirmed positive for EEE virus through virus isolation or seroconversion, and seven additional horses with compatible symptoms were in close spatial and temporal proximity to the confirmed cases and were presumed to have died from EEE virus. The outbreak was centered around the Killbuck Wildlife Area, a 2,147-ha tract maintained by the state, half of which consists...
[Venezuelan equine encephalitis. Determination of antibodies in the human population of Municipio Mirand, Estado Zulia, Venezuela]. With the purpose of determining antibodies prevalence against Venezuelan Equine Encephalitis Virus in the population of Puertos de Altagracia and Sabaneta de Palmas of Miranda county, Zulia State, Venezuela, 199 subjects were studied: 57 from Puertos de Altagracia and 142 from Sabaneta de Palmas. They were classified in older (42.78%) and younger (57.2%) than 15 years. The blood specimens were processed for Hemagglutination Inhibition Test using EEV antigen Goajira strain at pH 6.5. We found that all 57 specimens from Puertos de Altagracia were negative, whereas of 142 specimens from Sabaneta ...
Molecular evidence for the origin of the widespread Venezuelan equine encephalitis epizootic of 1969 to 1972. Venezuelan equine encephalitis (VEE) virus is a mosquito-borne pathogen that has caused encephalitis in equine species and humans during sporadic outbreaks in the western hemisphere. The last, and most widespread, VEE outbreak occurred in South America, Central America, Mexico and the U.S.A. (Texas) during 1969 to 1972. We have cloned and sequenced the genome of a virulent VEE subtype I-AB virus, strain 71-180, isolated in Texas in 1971. Thirty-four nucleotide differences were detected between the genome of 71-180 virus and that of the subtype I-AB Trinidad donkey (TRD) virus isolated during t...
Outcome of treatment in 23 horses with progressive ethmoidal haematoma. This paper describes the outcome of treatment in 23 horses with an ethmoidal haematoma. In 22 cases a diagnosis could be made by endoscopic means alone but in 1 horse the lesion was confined to the maxillary sinus and a diagnosis was made only at surgery. One horse was destroyed at the owner's request but the other 22 underwent radical excision of the lesion via a facial flap approach under general anaesthesia. Post-operative haemorrhage was controlled by nasal packing with a gauze bandage and this was removed between the 2nd and 4th post-operative day. One horse died from encephalitis the day...
Phylogenetic analysis of alphaviruses in the Venezuelan equine encephalitis complex and identification of the source of epizootic viruses. We studied the evolution of alphaviruses in the Venezuelan equine encephalitis (VEE) complex using phylogenetic analysis of RNA nucleotide sequences from limited portions of the nsP4, E1, and 3' untranslated genome regions of representative strains. The VEE complex constituted a monophyletic group of viruses (descended from a common ancestor); some serologic VEE varieties such as subtype III formed monophyletic groups while subtype I did not. Subtype II Everglades and variety ID enzootic viruses formed a monophyletic group which also included all epizootic variety IAB and IC VEE isolates. Ever...
A five year (1985-1989) retrospective study of equine neurological diseases with special reference to rabies. A retrospective study of horses necropsied between 1985 and 1989 at a diagnostic laboratory of a veterinary school in North America is documented. In this investigation over 20 per cent of the horses had clinical neurological signs. Equine protozoal myeloencephalitis (caused by Sarcocystis neurona) and cervical stenotic myelopathy (wobbler syndrome) were the most common of these disorders. The veterinary school is located in the midst of a raccoon rabies enzootic area. However, only four cases of equine rabies were diagnosed during the 5-year study. The gross microscopical and immunohistochemi...
The molecular epidemiology of equine herpesvirus 1 (equine abortion virus) in Australasia 1975 to 1989. The restriction endonuclease DNA fingerprints of 57 isolates of equine herpesvirus 1 (EHV1; equine abortion virus) from abortion, perinatal foal mortalities and encephalitis from 15 epidemics that occurred in Australasia between 1975 and 1989 were examined using the enzymes Bam HI, EcoRI and Bgl II. There was a remarkable degree of uniformity in the restriction patterns; mobility differences were observed in only 14 of 52 (27%) of the fragments. Twelve of these 14 fragments were located within the repeat structures that bracket the unique short region of the genome or were located at the left ...
[Teratogenic effect of the Venezuelan equine encephalitis virus: a review of the problem]. Clinical findings on Venezuelan Equine Encephalitis virus infection and the teratogenic effects of several Togaviruses are described. Similarities between the intrauterine alterations induced by Venezuelan Equine Encephalitis virus and rubella virus are pointed out. Findings described by Wenger in 1967 were those of massive cerebral necrosis in fetuses of women presumably suffering of encephalitis and they are commented along with the development of an animal experimental model at the end of 1970-1980. Pathogenesis of the intrauterine infection seemed to be related to changes in the placental ...
Hepatoencephalopathy and hypocalcemia in a miniature horse mare. 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...
[Epidemiology of encephalitis caused by arbovirus in the Brazilian Amazonia]. An overview of ecological, epidemiological and clinical findings of potential arthropod-borne encephalitis viruses circulating in the Amazon Region of Brazil are discussed. These viruses are the Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), Mucambo (MUC) and Pixuna (PIX). These last two are subtypes (III and IV) of Venezuelan Equine Encephalitis virus. The areas of study were the highways and projects of development, as well as places where outbreaks of human diseases caused by arboviruses had been detected. These viruses are widespread in ...
[Symptomatology and diagnosis of Borna encephalitis of horses. A case analysis of the last 13 years]. In a retrospective study of 38 horses with Borna encephalitis which were clinically and histopathologically examined in the "I. Medizinische Tierklinik" in Munich between 1977 and 1990, the epidemiology, the clinical symptomatic and the diagnostic procedures available are presented. Indirect immunofluorescence showed antibodies in the serum of 12 out of 29 cases (41%) and in the cerebrospinal fluid (CSF) of 17 out of 28 cases (61%). The evaluation of 23 cases in which indirect immunofluorescence of serum and CSF, and also the post mortem virological and histopathological examination of the bra...
Aujeszky’s disease in a horse. A horse with neurological signs and severe meningoencephalitis caused by Aujeszky's disease is described. The diagnosis was established by immunohistochemistry, DNA-in situ hybridization and serological tests. Aujeszky's disease virus antigen and Aujeszky's disease viral DNA were detected in neurons of the cerebrum. In the serum of the horse antibodies against Aujeszky's disease virus were detected in a virus neutralization test, in a blocking ELISA which specifically detects antibodies against the glycoprotein I (Ig) of the virus, in an indirect double sandwich ELISA and with colloidal gold i...
Trajectory analysis of winds and eastern equine encephalitis in USA, 1980-5. Backward trajectories of winds were determined to identify possible sources of eastern equine encephalitis virus associated with isolation of virus from mosquitoes or birds or outbreaks in horses between 1980 and 1985 in Maryland, New Jersey, New York and Michigan, USA. The results of the trajectory analyses suggested that eastern equine encephalitis virus could have been carried by infected mosquitoes on surface winds at temperatures 13 degrees C or higher from North Carolina north-eastwards along the Atlantic Coast to Maryland and New Jersey and thence to upstate New York and from western Ke...
[Antibodies against Venezuelan equine encephalitis in the human population of the Mara district of the state of Zulia, Venezuela]. Antibodies against Venezuelan Equine Encephalitis Virus (VEEV) were studied in the human population of Mara District, Zulia State, Venezuela. Two hundred thirty nine blood samples were taken from the towns of San Rafael de Mara, Santa Cruz de Mara, La Sierrita-4 Bocas, Carrasquero, Isla de San Carlos e Isla de Toas, during june, july and september, 1988. Donors samples were classified by age, sex and serological titres. Eighty nine were less than 15 years old (37.2%) and 150, over 15 years old (62.7%). From the 239 samples, 224 were negative (93.7%) and 15 positive (6.3%). Our results indicate...
Toxicity of field samples and Fusarium moniliforme from feed associated with equine-leucoencephalomalacia. Feed samples of corn, pelleted feed, and oats associated with equine leucoencephalomalacia (ELEM) were obtained from North Carolina, Illinois, Indiana, and Oklahoma. These samples contained a high colony density of Fusarium moniliforme Sheldon which ranged from 64 to 87% of the total fungi. Fifty-nine F. moniliforme strains were isolated. Isolates of F. moniliforme in feed samples from Illinois, Indiana, and Oklahoma were cultured on corn. The fermented corn, mixed with regular feed and fed to one-day-old ducklings, effected a high mortality coefficient (average 55%). Methanol extracts of corn...
