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.
Tan Y, Lam TT, Heberlein-Larson LA, Smole SC, Auguste AJ, Hennigan S, Halpin RA, Fedorova N, Puri V, Stockwell TB, Shilts MH, Andreadis T....Eastern equine encephalitis virus (EEEV) has a high case-fatality rate in horses and humans, and Florida has been hypothesized to be the source of EEEV epidemics for the northeastern United States. To test this hypothesis, we sequenced complete genomes of 433 EEEV strains collected within the United States from 1934 to 2014. Phylogenetic analysis suggested EEEV evolves relatively slowly and that transmission is enzootic in Florida, characterized by higher genetic diversity and long-term local persistence. In contrast, EEEV strains in New York and Massachusetts were characterized by lower genet...
Downs J, Vaziri M, Jenkins A, Unnasch T.Eastern Equine Encephalitis Virus (EEEV) is the most pathogenic arbovirus endemic to the United States. EEEV primarily infects birds but can be fatal to humans, horses, and some other mammals. Although EEEV transmission occurs in the Northeastern, Southeastern, and Midwestern United States, the largest number of horse and human cases have been reported in Florida, the only state where transmission occurs year round. Currently, a GIS-based risk index (RI) model is used to map EEE transmission risk to horses in Florida. This study validates that RI model using a 5-yr dataset of horse cases in Fl...
Carrera JP, Bagamian KH, Travassos da Rosa AP, Wang E, Beltran D, Gundaker ND, Armien B, Arroyo G, Sosa N, Pascale JM, Valderrama A, Tesh RB....Members of the genera (family ) and (family ) are important zoonotic human and equine etiologic agents of neurologic diseases in the New World. In 2010, an outbreak of Madariaga virus (MADV; formerly eastern equine encephalitis virus) and Venezuelan equine encephalitis virus (VEEV) infections was reported in eastern Panamá. We further characterized the epidemiology of the outbreak by studying household contacts of confirmed human cases and of equine cases with neurological disease signs. Serum samples were screened using a hemagglutination inhibition test, and human results were confirmed u...
Fortuna PRJ, Bielefeldt-Ohmann H, Ovchinnikov DA, Wolvetang EJ, Whitworth DJ.Horses are susceptible to a number of neurotropic viruses, including West Nile virus (WNV), which is a pathogen of global significance in both horses and humans. However, there are no in vitro models with which to study infectious neuropathic diseases in the horse. In an effort to redress this, we have generated neurons from equine induced pluripotent stem cells (equiPSCs) that express a range of cortical neuron-specific markers, in addition to the membrane-bound ligand ephrin B3, which plays an important role in axon guidance as well as functioning as the receptor through which henipaviruses,...
Chapman GE, Baylis M, Archer D, Daly JM.Equine populations worldwide are at increasing risk of infection by viruses transmitted by biting arthropods, including mosquitoes, biting midges (Culicoides), sandflies and ticks. These include the flaviviruses (Japanese encephalitis, West Nile and Murray Valley encephalitis), alphaviruses (eastern, western and Venezuelan encephalitis) and the orbiviruses (African horse sickness and equine encephalosis). This review provides an overview of the challenges faced in the surveillance, prevention and control of the major equine arboviruses, particularly in the context of these viruses emerging in ...
Schale S, Howe D, Yeargan M, Morrow JK, Graves A, Johnson AL.Infection by 2 or more protozoa is linked with increased severity of disease in marine mammals with protozoan encephalitis. Objective: To assess whether horses with equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona also have evidence of infection with Neospora hughesi or Toxoplasma gondii. We hypothesized that horses with EPM would be more likely than horses with cervical vertebral stenotic myelopathy (CVSM) to be positive for antibodies to multiple protozoan parasites. Methods: One hundred one horses with neurologic disease: 49 with EPM and 52 with CVSM. Methods: Case rev...
Alphaviruses can produce febrile illness and encephalitis in dead-end hosts such as horses and humans. Within this genus, the Venezuelan Equine Encephalitis virus (VEEV) complex includes pathogenic epizootic subtypes and enzootic subtypes that are not pathogenic in horses (except subtype IE, Mexican strains), although they can cause febrile symptoms in humans. The Rio Negro virus (RNV-VEEV subtype VI) circulates in Argentina, where it was associated with undifferentiated febrile illness. Mayaro (MAYV) and Una (UNAV) viruses belong to a different group, the Semliki Forest virus complex, with co...
Zoll WM, Prakoso D, Dark M, Liu J, Stockdale-Walden H, Long MT.Eosinophils within the central nervous system are abnormal and are usually associated with fungal or parasitic infections in horses. Causative agents include Halicephalobus gingivalis, Sarcocystis neurona, and Neospora hughesi. Confirmation of these organisms via specific testing is typically not performed, and final diagnoses are often presumptive. With molecular technology, many of these organisms can now be confirmed. This is important for emerging and zoonotic pathogens, including Angiostrongylus cantonensis, an emerging parasite of interest in the southeastern United States. We retrospect...
Kumar R, Patil RD.The importance of horse (Equus caballus) to equine practitioners and researchers cannot be ignored. An unevenly distributed population of equids harbors numerous diseases, which can affect horses of any age and breed. Among these, the affections of nervous system are potent reason for death and euthanasia in equids. Many episodes associated with the emergence of equine encephalitic conditions have also pose a threat to human population as well, which signifies their pathogenic zoonotic potential. Intensification of most of the arboviruses is associated with sophisticated interaction between ve...
Weissenböck H, Bagó Z, Kolodziejek J, Hager B, Palmetzhofer G, Dürrwald R, Nowotny N.Borna disease, a lethal infection with Borna disease virus-1 (BoDV-1), was diagnosed in four horses from Upper Austria in 2015 and 2016. All cases occurred in winter (two cases in February 2015 and two cases in December 2016), and the maximal distance of the affected stables was 17 km. To demonstrate whether the causative agent was also harbored by its reservoir host, the bicolored white-toothed shrew (Crocidura leucodon), 28 shrews from this geographic area were collected in 2015 and investigated for the presence of BoDV-1. The shrew species were identified according to taxonomic clues and ...
Plumlee Q, Meason-Smith C, Dieterly A, Gomez G, Porter BF, Rodrigues Hoffmann A.Many previously unrecognized fungi are emerging as potential pathogens. One such group is dematiaceous fungi of the Chaetomiaceae family (phylum Ascomycota, class Sordariomycetes). These fungi are rare causes of opportunistic, neurotropic phaeohyphomycosis in humans but are not known to cause similar infections in animals. The aims of this study were to investigate equine hyphal mycotic encephalitis, characterize key histopathologic features, and classify causative organisms with molecular diagnostic techniques. Seven cases were evaluated by histopathology. Panfungal PCR targeting the ribosoma...
Vanhomwegen J, Beck C, Desprès P, Figuerola A, García R, Lecollinet S, López-Roig M, Manuguerra JC, Serra-Cobo J.The presence of major arbovirus vector species, climate change that promotes the expansion and increase of their populations, and potential animal reservoirs mean that vector-borne diseases represent a significant health risk for Mallorca's inhabitants. Microbiological monitoring of circulating arboviruses, particularly flaviviruses causing encephalitis, was initiated using domestic horses from localities near wetlands as "sentinel" hosts. A total of 291 blood samples were taken from 172 horses between 2011 and 2012, using paired samples to highlight seroconversion events. A multiplex immunoas...
Chaney SB, Marsh AE, Lewis S, Carman M, Howe DK, Saville WJ, Reed SM.Equine protozoal myeloencephalitis (EPM) remains a significant central nervous system disease of horses in the American continents. Sarcocystis neurona is considered the primary causative agent and its intermediate life stages are carried by a wide host-range including raccoons (Procyon lotor) in North America. S. neurona sarcocysts mature in raccoon skeletal muscle and can produce central nervous system disease in raccoons, mirroring the clinical presentation in horses. The study aimed to develop laboratory tools whereby the life cycle and various life stages of S. neurona could be better stu...
Pintore MD, Cerutti F, D'Angelo A, Corona C, Gazzuola P, Masoero L, Colombo C, Bona R, Cantile C, Peletto S, Casalone C, Iulini B.A fatal case of meningoencephalitis was reported in a 13-year-old Koninklijk Warmbloed Paard Nederland stallion, suspected of West Nile virus (WNV) infection, in the Piedmont region of Italy. Clinical signs included right head tilt and circling, depression alternated with excitability, fever and lateral strabismus. Combined treatment consisting of dimethylsulfoxide, dexamethasone, sulphonamides and sedative was administered, but because of the poor conditions the horse was euthanatized and submitted for necropsy. At post-mortem examination no skin lesions were observed, all organs appeared nor...
Berrocal A, de Oliveira JB.Halicephalobus gingivalis is a free-living nematode that causes an opportunistic infection in animals and humans. Two fatal cases of encephalitis and nephritis caused by H. gingivalis in equines from Costa Rica and Honduras are reported. Case 1: a 6-year-old Arabian stallion, from Costa Rica, presented severe neurological signs and was treated with systemic anti-inflammatory drugs and antibiotics. Because there was no improvement, it was euthanatized. Grossly, both kidneys showed large white nodules, ranging from 0.10 to 2.50cm. Histopathologically, both kidneys showed similar changes consisti...
Vina-Rodriguez A, Eiden M, Keller M, Hinrichs W, Groschup MH. (VEEV) is an from the family that causes epizootic outbreaks in equids and humans in Central and South America. So far, most studies use conventional reverse transcriptase PCR assays for the detection of the different VEEV subtypes. Here we describe the development of a TaqMan quantitative real-time reverse transcriptase PCR assay for the specific detection and quantitation of all VEEV subtypes which uses in parallel a universal equine encephalitis virus control RNA carrying target sequences of the three equine encephalitis viruses. The control RNA was used to generate standard curves for t...
Cleton NB, van Maanen K, Bergervoet SA, Bon N, Beck C, Godeke GJ, Lecollinet S, Bowen R, Lelli D, Nowotny N, Koopmans MPG, Reusken CBEM.The genus Flavivirus in the family Flaviviridae includes some of the most important examples of emerging zoonotic arboviruses that are rapidly spreading across the globe. Japanese encephalitis virus (JEV), West Nile virus (WNV), St. Louis encephalitis virus (SLEV) and Usutu virus (USUV) are mosquito-borne members of the JEV serological group. Although most infections in humans are asymptomatic or present with mild flu-like symptoms, clinical manifestations of JEV, WNV, SLEV, USUV and tick-borne encephalitis virus (TBEV) can include severe neurological disease and death. In horses, infection wi...
Shepard JJ, Andreadis TG, Thomas MC, Molaei G.Eastern equine encephalitis virus (EEEV) is a highly pathogenic mosquito-borne arbovirus, with active transmission foci in freshwater hardwood swamps in eastern North America, where enzootic transmission is maintained between the ornithophilic mosquito, Culiseta melanura, and wild passerine birds. The role of other locally abundant mosquito species in virus transmission and their associations with vertebrate hosts as sources of blood meals within these foci are largely unknown but are of importance in clarifying the dynamics of enzootic and epidemic/epizootic transmission. Blood-engorged mosqu...
Burkett-Cadena ND, Gibson J, Lauth M, Stenn T, Acevedo C, Xue RD, McNelly J, Northey E, Hassan HK, Fulcher A, Bingham AM, van Olphen J, van Olphen A....Zoonotic mosquito-borne viruses, such as the West Nile virus (WNV) and eastern equine encephalitis virus (EEEV), are major public health threats in the United States. Early detection of virus transmission and targeted vector management are critical to protect humans against these pathogens. Sentinel chickens and pool screening of mosquitoes, the most widely used methods of arbovirus early detection, have technical time-lags that compromise their early-detection value. The exploitation of sugar-feeding by trapped mosquitoes for arbovirus surveillance may represent a viable alternative to other ...
Borland EM, Ledermann JP, Powers AM.Highlands J virus (HJV) is an alphavirus closely related to western equine encephalitis virus (WEEV) and eastern equine encephalitis virus (EEEV). HJV is an avian pathogen with the potential for disruption of poultry operations, but is not known to cause human or equine disease. HJV has only been identified in the eastern United States and is thought to have a transmission cycle similar to that of EEEV involving Culiseta melanura mosquitoes and birds. However, HJV is more genetically similar to WEEV and it remains unclear if it may be transmitted by Culex species mosquitoes like WEEV. Seven st...
Hannaman D, Dupuy LC, Ellefsen B, Schmaljohn CS.Venezuelan equine encephalitis virus (VEEV), a mosquito-borne alphavirus, causes periodic epizootics in equines and is a recognized biological defense threat for humans. There are currently no FDA-licensed vaccines against VEEV. We developed a candidate DNA vaccine expressing the E3-E2-6K-E1 genes of VEEV (pWRG/VEE) and performed a Phase 1 clinical study to assess the vaccine's safety, reactogenicity, tolerability, and immunogenicity when administered by intramuscular (IM) or intradermal (ID) electroporation (EP) using the Ichor Medical Systems TriGrid™ Delivery System. Subjects in IM-EP gro...
Żuraw A, Plog S, Lierz M, Gruber AD.Sarcocystis calchasi has recently been identified as the cause of pigeon protozoal encephalitis, PPE, a lethal brain disease in pigeons and parrots. While only avian species have been identified so far to be susceptible to this pathogen as definitive or intermediate hosts, we speculated whether mammals may be susceptible as well, as in Sarcocystis neurona and other related apicomplexan parasites. Specifically, we hypothesized its involvement in mammalian meningoencephalitis of unknown origin, MUO. A total of 143 archived formalin fixed, paraffin embedded brain samples with MUO from dogs, cats,...
Abad-Cobo A, Llorente F, Barbero MDC, Cruz-López F, Forés P, Jiménez-Clavero MÁ.West Nile fever/encephalitis (WNF) is an infectious disease affecting horses, birds and humans, with a cycle involving birds as natural reservoirs and mosquitoes as transmission vectors. It is a notifiable disease, re-emerging in Europe. In Spain, it first appeared in horses in the south (Andalusia) in 2010, where outbreaks occur every year since. However, in 2014, an outbreak was declared in horses in central Spain, approximately 200 km away from the closest foci in Andalusia. Before that, evidence of West Nile virus (WNV) circulation in central Spain had been obtained only from wildlife, bu...
Ballarin C, Povinelli M, Granato A, Panin M, Corain L, Peruffo A, Cozzi B.The domestic bovine Bos taurus is raised worldwide for meat and milk production, or even for field work. However the functional anatomy of its central nervous system has received limited attention and most of the reported data in textbooks and reviews are derived from single specimens or relatively old literature. Here we report information on the brain of Bos taurus obtained by sampling 158 individuals, 150 of which at local abattoirs and 8 in the dissecting room, these latter subsequently formalin-fixed. Using body weight and fresh brain weight we calculated the Encephalization Quotient (EQ)...
Oliver J, Lukacik G, Kramer LD, Backenson PB, Sherwood JA, Howard JJ.In New York State (NYS), Eastern equine encephalitis (EEE) was first reported in a human in 1971, in horses in 1970, and in pheasants in 1952. Methods: Following work for the interval from 1970 to 1991, we identified cases in vertebrates from 1992 to 2012, through a passive surveillance system involving veterinarians in clinical practice, county health departments, and the Departments of Agriculture and Markets, Environmental Conservation, and Health, of the State of New York. Results: During an 11-year hiatus, from 1992 to 2002, no case in any vertebrate was observed. In a re-emergence, from ...
Petrov AA, Lebedev VN, Kulish VS, Pyshnaya NS, Stovba LF, Borisevich SV.Epidemiologic analysis of epidemic outbreaks caused by American equine encephalitis causative agents is carried out in the review. Eastern equine encephalomyelitis (EEE), Western equine encephalomyelitis (WEE) and Venezuela equine encephalomyelitis (VEE) viruses are etiologic agents of dangerous transmissive diseases that are usually accompanied by fever and neurologic symptoms. Among the New World alphaviruses, VEE virus has the most potential danger for humans and domestic animals. Currently, enzootic strains of VEE play an increasing role as etiologic agents of human diseases. Most of the V...
Delcambre GH, Liu J, Herrington JM, Vallario K, Long MT.Phenotypic characterization of cellular responses in equine infectious encephalitides has had limited description of both peripheral and resident cell populations in central nervous system (CNS) tissues due to limited species-specific reagents that react with formalin-fixed, paraffin embedded tissue (FFPE). This study identified a set of antibodies for investigating the immunopathology of infectious CNS diseases in horses. Multiple commercially available staining reagents and antibodies derived from antigens of various species for manual immunohistochemistry (IHC) were screened. Several techni...
Baer A, Lundberg L, Swales D, Waybright N, Pinkham C, Dinman JD, Jacobs JL, Kehn-Hall K.Venezuelan equine encephalitis virus (VEEV) is a previously weaponized arthropod-borne virus responsible for causing acute and fatal encephalitis in animal and human hosts. The increased circulation and spread in the Americas of VEEV and other encephalitic arboviruses, such as eastern equine encephalitis virus and West Nile virus, underscore the need for research aimed at characterizing the pathogenesis of viral encephalomyelitis for the development of novel medical countermeasures. The host-pathogen dynamics of VEEV Trinidad donkey-infected human astrocytoma U87MG cells were determined by car...
Morita K, Nabeshima T, Buerano CC.Japanese encephalitis (JE) is an inflammation of the central nervous system in humans and animals, specifically horses and cattle. The disease, which can sometimes be fatal, is caused by the flavivirus Japanese encephalitis virus (JEV), of which there are five genotypes (genotypes 1, 2, 3, 4 and 5). The transmission cycle of the virus involves pigs and wild birds as virus amplifiers and mosquitoes as vectors for transferring the virus between amplifying hosts and to dead- end hosts, i.e. humans, horses and cattle. In horses and cattle the disease is usually asymptomatic, but when clinical sign...
Wendell LC, Potter NS, Roth JL, Salloway SP, Thompson BB.Eastern Equine Encephalitis (EEE) virus is an arbovirus that mostly causes asymptomatic infection in humans; however, some people can develop a neuroinvasive infection associated with a high mortality. Methods: We present a case of a patient with severe neuroinvasive EEE. Results: A 21-year-old man initially presented with headache, fever, and vomiting and was found to have a neutrophilic pleocytosis in his cerebrospinal fluid. He eventually was diagnosed with EEE, treated with high-dose methylprednisolone and intravenous immunoglobulin. His course in the NeuroIntensive Care Unit was complicat...
Makrynitsa GI, Ntonti D, Marousis KD, Birkou M, Matsoukas MT, Asami S, Bentrop D, Papageorgiou N, Canard B, Coutard B, Spyroulias GA.Venezuelan equine encephalitis virus (VEEV) is a new world alphavirus which can be involved in several central nervous system disorders such as encephalitis and meningitis. The VEEV genome codes for 4 non-structural proteins (nsP), of which nsP3 contains a Macro domain. Macro domains (MD) can be found as stand-alone proteins or embedded within larger proteins in viruses, bacteria and eukaryotes. Their most common feature is the binding of ADP-ribose (ADPr), while several macro domains act as ribosylation writers, erasers or readers. Alphavirus MD erase ribosylation but their precise contributi...
Schulze V, Große R, Fürstenau J, Forth LF, Ebinger A, Richter MT, Tappe D, Mertsch T, Klose K, Schlottau K, Hoffmann B, Höper D, Mundhenk L....Borna disease virus 1 (BoDV-1) is the causative agent of Borna disease, an often fatal neurologic condition of domestic mammals, including New World camelids, in endemic areas in Central Europe. Recently, BoDV-1 gained further attention by the confirmation of fatal zoonotic infections in humans. Although Borna disease and BoDV-1 have been described already over the past decades, comprehensive reports of Borna disease outbreaks in domestic animals employing state-of-the-art diagnostic methods are missing. Here, we report a series of BoDV-1 infections in a herd of 27 alpacas (Vicugna pacos) in t...
Komar N, Spielman A.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...
Siger L, Bowen R, Karaca K, Murray M, Jagannatha S, Echols B, Nordgren R, Minke JM.Efficacy of the Recombitek Equine West Nile Virus (WNV) vaccine was evaluated against a WNV intrathecal challenge model that results in WNV-induced clinical disease. Ten vaccinated (twice at days 0 and 35) and 10 control horses were challenged 2 weeks after administration of the second vaccine with a virulent WNV by intrathecal administration. After the challenge, eight of 10 controls developed clinical signs of encephalomyelitis whereas one vaccinate exhibited muscle fasciculation only once. Nine controls and one vaccinate developed a fever. Histopathology revealed mild to moderate nonsuppura...
Lubelczyk C, Mutebi JP, Robinson S, Elias SP, Smith LB, Juris SA, Foss K, Lichtenwalner A, Shively KJ, Hoenig DE, Webber L, Sears S, Smith RP.From July to September, 2009, an outbreak of eastern equine encephalitis virus (EEEv) occurred in five counties in Maine. The virus was isolated from 15 horses, 1 llama, and pheasants in three separate captive flocks. One wild turkey, screened before translocation, also showed exposure to the virus in January 2010. Two pools of Culiseta melanura (Coquillett) tested positive for EEEv during routine seasonal surveillance in York County in September, but none of the mosquitoes collected during rapid response surveys tested positive. There were more Cs. melanura in July, August, and September 2009...
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...
Yamanaka T, Tsujimura K, Kondo T, Yasuda W, Okada A, Noda K, Okumura T, Matsumura T.Japanese encephalitis (JE) developed in an unvaccinated half-bred horse kept in Tottori Prefecture, Japan. The animal showed ataxia with pyrexia and low appetite, and ultimately died. A viral strain was isolated from the cerebrum of the horse and was identified as JE virus (JEV) by RT-PCR using JEV specific primers. The isolated JEV was classified into genotype I by nucleotide sequence analysis of the viral envelope gene. We believe that this is the first report of the genotype I strain being isolated from a horse.
Wang T, Hu L, Liu M, Wang T, Hu X, Li Y, Liu W, Li Y, Wang Y, Ren H, Zhang W, Wang C, Li L.The equine herpesvirus type 8 (EHV-8) can cause significant economic losses in the global horses and donkey industry. The disease has been associated with abortion and respiratory symptoms. However, it is rare for a study to be reported about donkeys with neurological diseases induced by EHV-8 infection. In the present study, one 2-year-old male donkey, from a large-scale donkey farm in China, died with a severe neurological disorder. The causative agent, donkey/Shandong/10/2021 (GenBank accession: OL856098), was identified and isolated from the brain tissue of the dead donkey. Meanwhile, BALB...
Smith DR, Schmaljohn CS, Badger C, Ostrowski K, Zeng X, Grimes SD, Rayner JO.Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV) are mosquito-borne viruses in the Americas that cause central nervous system (CNS) disease in humans and equids. In this study, we directly characterized the pathogenesis of VEEV, EEEV, and WEEV in cynomolgus macaques following subcutaneous exposure because this route more closely mimics natural infection via mosquito transmission or by an accidental needle stick. Our results highlight how EEEV is significantly more pathogenic compared to VEEV similarly to what is observed in humans. Interestingly, EEEV appears...
Hill V, Koch RT, Bialosuknia SM, Ngo K, Zink SD, Koetzner CA, Maffei JG, Dupuis AP, Backenson PB, Oliver J, Bransfield AB, Misencik MJ, Petruff TA....Eastern equine encephalitis virus (EEEV) causes a rare but severe disease in horses and humans and is maintained in an enzootic transmission cycle between songbirds and Culiseta melanura mosquitoes. In 2019, the largest EEEV outbreak in the United States for more than 50 years occurred, centered in the Northeast. To explore the dynamics of the outbreak, we sequenced 80 isolates of EEEV and combined them with existing genomic data. We found that, similar to previous years, cases were driven by multiple independent but short-lived virus introductions into the Northeast from Florida. Once in the ...
Niczyporuk JS, Samorek-Salamonowicz E, Lecollinet S, Pancewicz SA, Kozdruń W, Czekaj H.Serum samples of 474 wild birds, 378 horses, and 42 humans with meningitis and lymphocytic meningitis were collected between 2010 and 2014 from different areas of Poland. West Nile virus (WNV) antibodies were detected using competition enzyme linked immunosorbent assays: ELISA-1 ID Screen West Nile Competition, IDvet, ELISA-2 ID Screen West Nile IgM Capture, and ELISA-3 Ingezim West Nile Compac. The antibodies were found in 63 (13.29%) out of 474 wild bird serum samples and in one (0.26%) out of 378 horse serum samples. Fourteen (33.33%) out of 42 sera from patients were positive against WNV a...
Crans WJ, McNelly J, Schulze TL, Main A.Eastern equine encephalitis virus (EEE) was isolated from the salt marsh mosquito, Aedes sollicitans, collected from coastal areas of New Jersey on 3 occasions during the late summer and fall of 1982. The isolations were made at a time when local Culiseta melanura were either undergoing a population increase or exhibiting high levels of EEE virus. Although no human cases were reported during the epizootic period, the data lend support to the hypothesis that Ae. sollicitans is capable of functioning as an epidemic vector in the coastal areas of New Jersey where human cases of EEE have been most...
Barba M, Fairbanks EL, Daly JM.Members of several different virus families cause equine viral encephalitis, the majority of which are arthropod-borne viruses (arboviruses) with zoonotic potential. The clinical signs caused are rarely pathognomonic; therefore, a clinical diagnosis is usually presumptive according to the geographical region. However, recent decades have seen expansion of the geographical range and emergence in new regions of numerous viral diseases. In this context, this review presents an overview of the prevalence and distribution of the main viral causes of equine encephalitis and discusses their impact an...
Bouzalas IG, Diakakis N, Chaintoutis SC, Brellou GD, Papanastassopoulou M, Danis K, Vlemmas I, Seuberlich T, Dovas CI.During the summer of 2010, an outbreak of West Nile virus (WNV) infections attributed to a lineage 2 WNV strain was reported among humans and horses in Central Macedonia, Northern Greece. Here, the clinical and laboratory investigation of horses that showed severe neurological signs due to WNV infection is being described. Specifically, between August and September 2010, 17 horses with neurological signs were detected. WNV infection was confirmed in all 17 clinical cases by applying laboratory testing. The duration of WNV-specific IgM antibodies in sera obtained from seven of the clinically af...
Ma H, Lundy JD, Cottle EL, O'Malley KJ, Trichel AM, Klimstra WB, Hartman AL, Reed DS, Teichert T.Alphaviruses such as Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) are arboviruses that can cause severe zoonotic disease in humans. Both VEEV and EEEV are highly infectious when aerosolized and can be used as biological weapons. Vaccines and therapeutics are urgently needed, but efficacy determination requires animal models. The cynomolgus macaque (Macaca fascicularis) provides a relevant model of human disease, but questions remain whether vaccines or therapeutics can mitigate CNS infection or disease in this model. The documentation of alphavirus e...
Kinde H, Mathews M, Ash L, St Leger J.Two horses, a 16-year-old male Holsteiner and a 5-year-old male miniature horse, were diagnosed with halicephalobiasis at the California Veterinary Diagnostic Laboratory System, San Bernardino Branch, in April and June of 1998. Over a period of 4 weeks, the Holsteiner horse developed renal dysfunction, blepharospasm, and blindness in the right eye. A 15-cm-diameter mass was detected on ultrasound examination in the right kidney. Terminally, the animal developed seizures and was euthanized. The miniature horse had a 6-week-long illness characterized by testicular enlargement and uveitis. This a...
Ballarin C, Povinelli M, Granato A, Panin M, Corain L, Peruffo A, Cozzi B.The domestic bovine Bos taurus is raised worldwide for meat and milk production, or even for field work. However the functional anatomy of its central nervous system has received limited attention and most of the reported data in textbooks and reviews are derived from single specimens or relatively old literature. Here we report information on the brain of Bos taurus obtained by sampling 158 individuals, 150 of which at local abattoirs and 8 in the dissecting room, these latter subsequently formalin-fixed. Using body weight and fresh brain weight we calculated the Encephalization Quotient (EQ)...
Cavalleri JV, Korbacska-Kutasi O, Leblond A, Paillot R, Pusterla N, Steinmann E, Tomlinson J.Horses and other equids can be infected with several viruses of the family Flaviviridae, belonging to the genus Flavivirus and Hepacivirus. This consensus statement focuses on viruses with known occurrence in Europe, with the objective to summarize the current literature and formulate clinically relevant evidence-based recommendations regarding clinical disease, diagnosis, treatment, and prevention. The viruses circulating in Europe include West Nile virus, tick-borne encephalitis virus, Usutu virus, Louping ill virus and the equine hepacivirus. West Nile virus and Usutu virus are mosquito-bor...
Mattar S, Komar N, Young G, Alvarez J, Gonzalez M.We prospectively sampled flavivirus-naïve horses in northern Colombia to detect West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) seroconversion events, which would indicate the current circulation of these viruses. Overall, 331 (34.1%) of the 971 horses screened were positive for past infection with flaviviruses upon initial sampling in July 2006. During the 12-month study from July 2006-June 2007, 33 WNV seroconversions and 14 SLEV seroconversions were detected, most of which occurred in the department of Bolivar. The seroconversion rates of horses in Bolivar for the period of M...
Pupo M, Guzmán MG, Fernández R, Llop A, Dickinson FO, Pérez D, Cruz R, González T, Estévez G, González H, Santos P, Kourí G, Andonova M....A surveillance system to detect West Nile virus (WNV) was established in Cuba in 2002. WNV infection was confirmed by serologic assays in 4 asymptomatic horses and 3 humans with encephalitis in 2003 and 2004. These results are the first reported evidence of WNV activity in Cuba.
Ross PF, Ledet AE, Owens DL, Rice LG, Nelson HA, Osweiler GD, Wilson TM.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...
Charlton KM, Mitchell D, Girard A, Corner AH.During an outbreak of abortion caused by equine herpesvirus 1, a neurologic disease characterized clinically by dullness and ataxia occurred in several mares. Equine herpesvirus 1 was isolated from brain and lung of two severely affected mares. Histologically, both mares had disseminated meningoencephalomyelitis characterized by necrotizing arteritis, focal malacia in grey and white matter of brain and spinal cord, and accumulation of lymphocytes and neutrophils in paravertebral ganglia. Eosinophilic intranuclear inclusion bodies occurred in foci of necrosis in thyroid adenomas of both mares.
Tauro L, Marino B, Diaz LA, Lucca E, Gallozo D, Spinsanti L, Contigiani M.St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) present ecological and antigenic similarities and are responsible for serious human diseases. In addition, WNV is a significant pathogen in terms of equine health. The purpose of our study was to analyse the seroprevalence of SLEV and WNV in equine sera collected in Santa Fe Province, Argentina. The seroprevalence determined using the plaque reduction neutralisation test was 12.2% for SLEV, 16.2% for WNV and 48.6% for a combination of both viruses. These results provide evidence of the co-circulation of SLEV and WNV in equines in Sa...
West Nile virus (WNV) was first detected in the Western Hemisphere in 1999 in New York City and has since caused seasonal epidemics of febrile illness and neurologic disease across the United States, where it is now the leading cause of arboviral encephalitis. This report updates a previous report and summarizes WNV activity in the United States reported to CDC in 2009. A total of 38 states and the District of Columbia (DC) reported 720 cases of WNV disease. Of these, 33 states and DC reported 386 cases of WNV neuroinvasive disease, for an incidence of 0.13 per 100,000 population. The five sta...
