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Topic:Encephalomyelitis
Encephalomyelitis in horses refers to inflammation of the brain and spinal cord, often caused by viral infections such as Eastern, Western, and Venezuelan equine encephalomyelitis viruses. These conditions can lead to neurological symptoms including fever, ataxia, and behavioral changes. The disease can be transmitted through mosquito vectors, with horses serving as dead-end hosts. Diagnosis typically involves serological testing and clinical evaluation. This page aggregates peer-reviewed research studies and scholarly articles that explore the etiology, pathogenesis, clinical presentation, and management strategies for encephalomyelitis in equine populations.
Screening for West Nile virus infections of susceptible animal species in Austria. Avian mortality and encephalomyelitis in equines are considered good indicators for West Nile virus (WNV) activity. We retrospectively tested 385 horse sera for WNV antibodies and looked for WNV nucleic acid and/or WNV antigen in paraffin embedded tissues from 12 horses with aetiologically unresolved encephalomyelitis and 102 free-living birds of different species which had been found dead. With the exception of four horses originating from eastern European countries investigated on the occasion of transit through Austria, all horse sera were negative. Nested RT-PCR of the horse tissues yielde...
Outbreak of equine herpesvirus type 1 myeloencephalitis: new insights from virus identification by PCR and the application of an EHV-1-specific antibody detection ELISA. Five of 10 pregnant, lactating mares, each with a foal at foot, developed neurological disease. Three of them became recumbent, developed complications and were euthanased; of the two that survived, one aborted an equine herpesvirus type 1 (EHV-1)-positive fetus 68 days after the first signs were observed in the index case and the other gave birth to a healthy foal on day 283 but remained ataxic and incontinent. The diagnosis of EHV-1 myeloencephalitis was supported by postmortem findings, PCR identification of the virus and by serological tests with an EHV-1-specific ELISA. At the time of the...
Prevalence of antibodies to Neospora caninum, Sarcocystis neurona, and Toxoplasma gondii in wild horses from central Wyoming. Sarcocystis neurona, Neospora caninum, N. hughesi, and Toxoplasma gondii are 4 related coccidians considered to be associated with encephalomyelitis in horses. The source of infection for N. hughesi is unknown, whereas opossums, dogs, and cats are the definitive hosts for S. neurona, N. caninum, and T. gondii, respectively. Seroprevalence of these coccidians in 276 wild horses from central Wyoming outside the known range of the opossum (Didelphis virginiana) was determined. Antibodies to T. gondii were found only in 1 of 276 horses tested with the modified agglutination test using 1:25, 1:50, ...
Transmission of eastern equine encephalomyelitis virus in central Alabama. A site near Tuskegee, Alabama was examined for vector activity of eastern equine encephalomyelitis (EEE) virus in 2001. More than 23,000 mosquitoes representing 8 genera and 34 species were collected during a 21-week period, and five species, Culiseta melanura, Aedes vexans, Coquillettidia perturbans, Culex erraticus, and Uranotaenia sapphirina, were examined for the presence of virus using a nested reverse transcriptase-polymerase chain reaction for EEE virus. Each species was infected at various times of the mosquito season (May-September) with different minimum infection rates (MIRs). Culis...
West Nile virus encephalomyelitis in horses in Ontario: 28 cases. West Nile virus encephalomyelitis was diagnosed in 28 horses presented to the Ontario Veterinary College Veterinary Teaching Hospital between August 20 and October 15, 2002. The age range of affected horses was 5 months to 20 years (mean 6.9 years, median 6 years). Clinical signs were highly variable. Duration of hospitalization ranged from < 1 to 12 days (mean 5 days, median 5.4 days). Overall, 16 of the 28 (57%) horses were discharged and, of the 14 from which follow-up information was available, 13 (93%) were reported to be clinically normal 4 to 6 weeks following discharge, while the ot...
Mosquitoes captured in a horse-baited stable trap in southeast Louisiana. A mosquito study based on collections from horse-baited stable traps was conducted in 1993 and 1994 at 3 sites in geographically and ecologically distinct areas of St. Tammany Parish (southeastern Louisiana) to determine the major horse-feeding mosquito species that could be possible bridging and epidemic vectors of eastern equine encephalomyelitis virus. A total of 4,535 mosquitoes in 1993 and 23,906 in 1994 involving 26 species were collected, of which, depending on the site, Culex salinarius, Cx. (Melanoconion) spp., Aedes vexans, Psophora ferox, Coquillettidia perturbans, Anopheles quadrim...
California state Mosquito-Borne Virus Surveillance and Response Plan: a retrospective evaluation using conditional simulations. The California Mosquito-Borne Virus Surveillance and Response Plan recently was developed to provide a semi-quantitative means for assessing risk for western equine encephalomyelitis (WEE) or St. Louis encephalitis (SLE) viruses and to provide intervention guidelines for mosquito control and public health agencies during periods of heightened risk for human infection. West Nile virus recently has arrived in California, and the response plan also will provide a baseline for assessing the risk for human and equine infection with this virus. In the response plan, overall risk is calculated by ave...
Serologic survey of domestic animals for zoonotic arbovirus infections in the Lacandón Forest region of Chiapas, Mexico. A serologic survey in domestic animals (birds and mammals) was conducted in four communities located in the Lacandón Forest region of northeastern Chiapas, Mexico, during June 29 to July 1, 2001, with the objective to identify zoonotic arboviruses circulating in this area. We collected 202 serum samples from healthy domestic chickens, geese, ducks, turkeys, horses and cattle. The samples were tested by plaque-reduction neutralization test for antibodies to selected mosquito-borne flaviviruses (family Flaviviridae), including St. Louis encephalitis (SLE), Rocio (ROC), Ilheus (ILH), Bussuquara ...
West Nile virus encephalomyelitis in horses: 46 cases (2001). To determine signalment, clinical findings, results of diagnostic testing, outcome, and postmortem findings in horses with West Nile virus (WNV) encephalomyelitis. Methods: Retrospective study. Methods: 46 horses with WNV encephalomyelitis. Methods: Clinical data were extracted from medical records of affected horses. Results: On the basis of clinical signs and results of serologic testing, WNV encephalomyelitis was diagnosed in 46 of 56 horses with CNS signs. Significantly more males than females were affected. Increased rectal temperature, weakness or ataxia, and muscle fasciculations were t...
Limited potential for mosquito transmission of genetically engineered, live-attenuated western equine encephalitis virus vaccine candidates. Specific mutations associated with attenuation of Venezuelan equine encephalitis (VEE) virus in rodent models were identified during efforts to develop an improved VEE vaccine. Analogous mutations were produced in full-length cDNA clones of the Cba 87 strain of western equine encephalitis (WEE) virus by site-directed mutagenesis in an attempt to develop an improved WEE vaccine. Isogenic viral strains with these mutations were recovered after transfection of baby hamster kidney cells with infectious RNA. We evaluated two of these strains (WE2102 and WE2130) for their ability to replicate in and...
The effect of aging on immune responses. Although vaccine manufacturers make no specific recommendations regarding the vaccination of older horses and ponies, the similarities in age-induced immunologic changes between human beings and equids suggests that similar vaccination recommendations should be followed. The need for vaccination of the older horse depends, of course, on the relative risk of exposure for the individual horse. Particular care should be taken when using attenuated vaccine products because these live agents may pose a unique risk to the older individual. Immunization with inactivated agent vaccines is likely to be...
Findings in cerebrospinal fluids of horses infected with West Nile virus: 30 cases (2001). To evaluate CSF in horses with confirmed West Nile virus encephalomyelitis. Methods: Retrospective study. Methods: 30 horses. Methods: Results of CSF analyses from horses with acute neurologic signs attributed to West Nile virus infection that was confirmed by immunoglobulin M antibody capture ELISA were reviewed and analyzed. Results: Among 30 CSF samples, findings in 8 (27%) were within reference ranges and in 22 (73%) were abnormal. Among the 22 abnormal samples, mononuclear pleocytosis was found in 16 (73%) and high protein concentration with nucleated cell count within reference range was...
Clinical signs of West Nile virus encephalomyelitis in horses during the outbreak in Israel in 2000. Between August and October 2000, 76 horses were reported by veterinary practitioners as having signs of a neurological disorder, varying from an involvement of the spinal cord alone to the entire central nervous system; 15 of the horses died or were euthanased as a result of their grave prognosis or secondary complications. At the same time, an outbreak of West Nile virus infection affected people and birds, principally domestic geese. West Nile virus was isolated from four of the horses with encephalomyelitis and five other horses seroconverted, indicating that the virus was the probable caus...
Eastern equine encephalomyelitis virus infection in a horse from California. A yearling quarter horse, which was raised in southern California, received routine vaccinations for prevention of infection by Eastern equine encephalomyelitis virus (EEEV). One week later, severe neurologic signs developed, and the horse was humanely destroyed. A vaccine-related encephalomyelitis was later suspected. A final diagnosis of EEEV infection was established on the basis of acute onset of the neurologic signs, histopathologic and serologic testing, and isolation and molecular characterization of EEEV from brain tissue. The vaccine was extensively tested for viral inactivation. Nucl...
High intensity light increases olfactory bulb melatonin in Venezuelan equine encephalitis virus infection. In mice infected with the Venezuelan equine encephalomyelitis (VEE) virus and exposed to high intensity light (2500 lux) with a 12 h light: 12 h dark photoperiod, a significant increase in the levels of melatonin in the olfactory bulb was observed. The significance of these findings deserves further studies to understand the mechanisms involved in this effect since the olfactory bulbs have been proposed as first portal for VEE virus entry into the CNS. The increase in melatonin content could represent one of the mechanisms of defense against the viral attack.
Pathologic and immunohistochemical findings in naturally occuring West Nile virus infection in horses. The pathologic and peroxidase immunohistochemical features of West Nile flavivirus (WNV) infection were compared in four horses from the northeastern United States and six horses from central Italy. In all 10 animals, there were mild to severe polioencephalomyelitis with small T lymphocyte and lesser macrophage perivascular infiltrate, multifocal glial nodules, neutrophils, and occasional neuronophagia. Perivascular hemorrhages, also noted macroscopically in two animals, were observed in 50% of the horses. In the four American horses, lesions extended from the basal nuclei through the brain st...
Clinical, pathologic, immunohistochemical, and virologic findings of eastern equine encephalomyelitis in two horses. Natural eastern equine encephalitis alphavirus (EEEV) infection was diagnosed in two adult horses with anorexia and colic, changes in sensorium, hyperexcitability, and terminal severe depression. Myocardium, tunica muscularis of stomach, intestine, urinary bladder, and spleen capsule had coagulative necrosis and perivascular lymphocytic infiltrate. Central nervous system (CNS) lesions were diffuse polioencephalomyelitis with leptomeningitis characterized by perivascular T lymphocyte cuffing, marked gliosis, neuronophagia, and multifocal microabscesses. Lesions were more prominent within cerebr...
Borna disease in horses. Borna disease is a sporadically occurring, progressive viral polioencephalomyelitis that primarily affects horses and sheep. The etiological agent, Borna disease virus (BDV), is an enveloped, single-stranded RNA virus that has been classified in the new virus family Bornaviridae within the order Mononegavirales. Serological evidence of BDV infection has been found in an increasing number of countries throughout the world. After an incubation period lasting a few weeks to several months, BDV infection can cause locomotor and sensory dysfunction followed by paralysis and death. Borna disease is ...
Diagnosis of eastern equine encephalitis by immunohistochemistry in two flocks of Michigan ring-neck pheasants. The diagnosis of eastern equine encephalitis (EEE) virus infection in avian species is relatively difficult when compared with other species. There are no characteristic histologic lesions in the avian brain that would serve to distinguish EEE from infections with, for example, Newcastle disease or highly pathogenic avian influenza virus. Traditionally, virus isolation (VI) and/or hemagglutination inhibition (HI) has been used for a definitive diagnosis of EEE in birds. Recently, we developed an immunohistochemistry (IHC) technique for confirmatory diagnosis of EEE infection in equine brain. T...
Effect of eastern equine encephalomyelitis virus on the survival of Aedes albopictus, Anopheles quadrimaculatus, and Coquillettidia perturbans (Diptera: Culicidae). The effect of eastern equine encephalomyelitis (EEE) virus on the survivorship of Aedes albopictus (Skuse), Anopheles quadrimaculatus Say, and Coquillettidia perturbans (Walker) was determined experimentally. Female mosquitoes were allowed to feed on EEE viremic chicks, and survival rates were compared for infected and uninfected mosquitoes. Additionally, the survival of female Cq. perturbans and An. quadrimaculatus intrathoracically (i.t.) inoculated with EEE was compared with controls receiving diluent inoculations. Infection with EEE significantly reduced survival in Cq. perturbans compared...
Halicephalobus gingivalis encephalomyelitis in a horse. An 8-year-old, Arabian mare presented with acute progressive ataxia and a firm swelling over the right mandible. Radiographs revealed multiple radiolucent areas on the mandibles. The mare's neurological signs progressed, she was consequently euthanized. Postmortem examination revealed mandibular granulomatous reactions and meningoencephalitis due to the nematode Halicephalobus gingivalis.
Role of peridomestic birds in the transmission of St. Louis encephalitis virus in southern California. In response to the 1984 St. Louis encephalitis (SLE) epidemic in the Los Angeles Basin of southern California (USA), an investigative program was initiated to evaluate the interactive components of the SLE virus transmission cycle. From 1987 through 1996 (10 yr), 52,589 birds were bled and their sera tested for SLE and western equine encephalomyelitis (WEE) virus antibodies by the hemagglutination inhibition (HAI) test. Eighty-three percent of the birds tested were house finches (Carpodacus mexicanus) (48.7%) and house sparrows (Passer domesticus) (34.6%); 1.1% of these birds were positive for...
Clinical and neuropathological features of West Nile virus equine encephalomyelitis in Italy. West Nile (WN) virus infection is a mosquito-borne flavivirosis endemic in Africa and Asia. Clinical disease is usually rare and mild and only in a few cases the infection causes encephalomyelitis in horses, fever and meningoencephalitis in man. We report here the clinical and pathological findings in an epidemic of the disease involving 14 horses from Tuscany, Italy. All cases were observed from August to October 1998. Affected horses showed ataxia, weakness paresis of the hindlimbs and, in 6 cases, there was paraparesis progressing to tetraplegia and recumbency within 2 to 9 days. Eight anim...
Toward the incrimination of epidemic vectors of eastern equine encephalomyelitis virus in Massachusetts: abundance of mosquito populations at epidemic foci. Putative epidemic/epizootic eastern equine encephalomyelitis virus (EEE) vector populations were compared at 15 recent (1982-90) human and horse case sites in Bristol and Plymouth counties in southeastern Massachusetts. Carbon dioxide-baited American Biophysics Corporation light traps were used for trapping adult mosquitoes to estimate biting risk in these foci of known transmission. Population data suggest that Coquillettidia perturbans, Aedes canadensis, and Culex salinarius are more likely vectors of EEE in Massachusetts than Aedes vexans, Anopheles punctipennis, and Anopheles quadrimaculat...
[HPLC separation and characterization of tick-borne encephalitis and equine Venezuela encephalomyelitis viral proteins]. 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.
Molecular epidemiological studies of veterinary arboviral encephalitides. Recent studies using molecular genetic approaches have made important contributions to our understanding of the epidemiology of veterinary arboviral encephalitides. Viruses utilizing avian enzootic hosts, such as Western equine encephalitis virus (WEEV) and North American Eastern equine encephalitis virus (EEEV), evolve as relatively few, highly conserved genotypes that extend over wide geographic regions; viruses utilizing mammalian hosts with more limited dispersal evolve within multiple genotypes, each geographically restricted. Similar findings have been reported for Australian alphaviruse...
Intestinal lesions in a horse associated with eastern equine encephalomyelitis virus infection. The primary lesions of eastern equine encephalomyelitis (EEE) virus infection in the horse are limited to the brain and spinal cord. Intestinal lesions in addition to the changes in the central nervous system were found in a 6-month-old male Tennessee Walking Horse. One week prior to death, this colt was vaccinated for EEE virus, western equine encephalomyelitis virus, influenza virus, equine rhinopneumonitis virus, and tetanus. The clinical signs consisted of ataxia and rear-end weakness, with a body temperature of 102.8 F. Gross lesions consisted of yellowish discoloration, swelling, edema, ...
Arboviral infections of the central nervous system–United States, 1996-1997. Arboviruses include mosquitoborne and tickborne agents that persist in nature in complex cycles involving birds or mammals, including humans. Arboviral infection can cause fever, headache, meningitis, encephalitis, and sometimes death. During 1996-1997, health departments in 19 states reported to CDC 286 confirmed or probable cases (eight fatal) of arboviral encephalitis in humans (132 cases in 1996 and 154 provisionally in 1997). Surveillance programs in 18 states detected enzootic arboviral activity in mosquito or sentinel or wild bird populations, and cases of arboviral disease were recogni...
