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.
Conze TM, Bagó Z, Revilla-Fernández S, Schlegel J, Goehring LS, Matiasek K.A final diagnosis in a horse with clinical signs of encephalopathy can be challenging despite the use of extensive diagnostics. Clinical signs are often not pathognomonic and need to be interpreted in combination with (specific) laboratory results and epidemiological data of the geographical region of the origin of the case(s). Here we describe the diagnostic pathway of tick-borne encephalitis virus infection in two horses using established molecular diagnostic methods and a novel in situ hybridization technique to differentiate between regionally important/emerging diseases for central Europe...
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...
Bantle CM, Rocha SM, French CT, Phillips AT, Tran K, Olson KE, Bass TA, Aboellail T, Smeyne RJ, Tjalkens RB.Viral infection of the central nervous system (CNS) can cause lasting neurological decline in surviving patients and can present with symptoms resembling Parkinson's disease (PD). The mechanisms underlying postencephalitic parkinsonism remain unclear but are thought to involve increased innate inflammatory signaling in glial cells, resulting in persistent neuroinflammation. We therefore studied the role of glial cells in regulating neuropathology in postencephalitic parkinsonism by studying the involvement of astrocytes in loss of dopaminergic neurons and aggregation of α-synuclein protein fo...
Hasan SS, Dey D, Singh S, Martin M.Alphaviruses are arboviruses that cause arthritis and encephalitis in humans. Eastern Equine Encephalitis Virus (EEEV) is a mosquito-transmitted alphavirus that is implicated in severe encephalitis in humans with high mortality. However, limited insights are available into the fundamental biology of EEEV and residue-level details of its interactions with host proteins. In recent years, outbreaks of EEEV have been reported mainly in the United States, raising concerns about public safety. This review article summarizes recent advances in the structural biology of EEEV based mainly on single-par...
Fouché N, Oesch S, Ziegler U, Gerber V.Tick-borne encephalitis is an important viral tick-borne zoonosis in Europe and Asia. The disease is induced by tick-borne encephalitis virus (TBEV). This report describes a 16-year-old Warmblood gelding presenting with sudden onset of lethargy, ataxia, and muscle fasciculations on the nostrils, the lips, and the eye lids as the most important clinical findings. The horse further had a mild facial nerve paralysis with drooping of the right upper and lower lip. Diagnosis was based on paired serum samples using TBEV-ELISAs revealing high serum IgM in the first sample with normal IgM in the secon...
Olufemi OT, Barba M, Daly JM.West Nile virus (WNV) is an emerging and re-emerging zoonotic flavivirus first identified in and endemic to Africa. The virus is transmitted between birds by biting mosquitoes, with equids and humans being incidental hosts. The majority of infected incidental hosts display no or only mild clinical signs, but a fraction develop encephalitis. The aim of this scoping review was to identify and evaluate primary research on the presence of antibodies to WNV among African equids. Three bibliographic databases and the grey literature were searched. Of 283 articles identified, only 16 satisfied all th...
Ortega Granda O, Valle C, Shannon A, Decroly E, Canard B, Coutard B, Rabah N.Venezuelan equine encephalitis virus (VEEV) is a reemerging arthropod-borne virus causing encephalitis in humans and domesticated animals. VEEV possesses a positive single-stranded RNA genome capped at its 5' end. The capping process is performed by the nonstructural protein nsP1, which bears methyl and guanylyltransferase activities. The capping reaction starts with the methylation of GTP. The generated mGTP is complexed to the enzyme to form an mGMP-nsP1 covalent intermediate. The mGMP is then transferred onto the 5'-diphosphate end of the viral RNA. Here, we explore the specificities of the...
Boos GS, Failing K, Colodel EM, Driemeier D, de Castro MB, Bassuino DM, Diomedes Barbosa J, Herden C.Like humans, horses are susceptible to neurotropic and neuroinvasive pathogens that are not always readily identified in histological sections. Instead, alterations in astrocytes and microglia cells can be used as pathological hallmarks of injured nervous tissue in a variety of infectious and degenerative diseases. On the other hand, equine glial cell alterations are poorly characterized in diseases. Therefore, in this study, we provide a statistically proved score system to classify astrogliosis and microgliosis in the central nervous system (CNS) of horses, based on morphological and quantit...
Fu DJ, Ramachandran A, Miller C.A 3-y-old, female Quarter Horse with a history of acute neurologic signs was found dead and was submitted for postmortem examination. Areas of petechial and ecchymotic hemorrhage were present on cross-sections of the cerebrum, cerebellum, and brainstem. Histologic examination of the brain revealed severe, purulent meningoencephalitis and vasculitis with a myriad of intralesional gram-positive cocci. was identified from formalin-fixed, paraffin-embedded tissue obtained from sites with active lesions by PCR and nucleotide sequencing of bacterial 16S ribosomal RNA. should be considered as a cau...
Motlou TP, Williams J, Venter M.The genus, family , contains several important emerging and re-emerging arboviruses of veterinary and medical importance. These viruses may cause mild febrile illness, to severe encephalitis, fetal deformity, abortion, hemorrhagic fever and death in humans and/or animals. Shuni virus (SHUV) is a zoonotic arbovirus thought to be transmitted by hematophagous arthropods. It was previously reported in a child in Nigeria in 1966 and horses in Southern Africa in the 1970s and again in 2009, and in humans with neurological signs in 2017. Here we investigated the epidemiology and phylogenetic relatio...
Weber MN, Mosena ACS, Baumbach LF, da Silva MS, Canova R, Dos Santos DRL, Budaszewski RDF, de Oliveira LV, Soane MM, Saraiva NB, Bellucco FT....Flaviviruses as West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), Ilhéus virus (ILHV), and Rocio virus (ROCV) are previously reported in different Brazilian regions, but studies in Southern Brazil are still scarce. To improve the information regarding flaviviruses in Southern Brazil, horse serum samples were analyzed using RT-qPCR and a commercial ELISA-Ab against WNV followed by PRNT. All 1000 samples analyzed by real-time RT-PCR resulted negative. The 465 subsampled samples were analyzed by a commercial ELISA-Ab against WNV, and the 18.5% (86/465) positive samples were further a...
Nunes JDSDSS, Casseb LMN, Guimarães RJPS, Reis WDM, de Barros BCV, Ferreira MS, Chiang JO, Pinheiro HHC, Vasconcelos PFDC, Cruz ACR.Serum samples from 89 equids were analyzed (75 horses, 9 donkeys, and 5 mules) from the municipality of Viseu, Pará state, Brazil. Samples were collected in November 2014 and August 2015. The antibody prevalence against the following alphaviruses was estimated: Eastern equine encephalitis virus, Western equine encephalitis virus, Mucambo virus, and Mayaro virus. Seroprevalence was determined by the hemagglutination inhibition (HI) technique. Sera that exhibited HI antibodies with heterotypic reactions for the analyzed viruses were subjected to the 90% plaque reduction neutralization test (PRN...
Snyman J, Koekemoer O, van Schalkwyk A, Jansen van Vuren P, Snyman L, Williams J, Venter M.Equine encephalosis virus (EEV) is a neglected virus endemic to South Africa and is considered to generally result in mild disease in equines. Specimens were analyzed from live horses that presented with undefined neurological, febrile, or respiratory signs, or sudden and unexpected death. Between 2010 and 2017, 111 of 1523 (7.3%) horse samples tested positive for EEV using a nested real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Clinical signs were reported in 106 (7.2%) EEV positive and 1360 negative horses and included pyrexia (77/106, 72.6%), icterus (20/106, 18.9%) an...
Malbon AJ, Dürrwald R, Kolodziejek J, Nowotny N, Kobera R, Pöhle D, Muluneh A, Dervas E, Cebra C, Steffen F, Paternoster G, Gerspach C, Hilbe M.Borna disease (BD), a frequently fatal neurologic disorder caused by Borna disease virus 1 (BoDV-1), has been observed for decades in horses, sheep, and other mammals in certain regions of Europe. The bicoloured white-toothed shrew (Crocidura leucodon) was identified as a persistently infected species involved in virus transmission. Recently, BoDV-1 attracted attention as a cause of fatal encephalitis in humans. Here, we report investigations on BoDV-1-infected llamas from a farm in a BD endemic area of Switzerland, and alpacas from holdings in a region of Germany where BD was last seen in the...
In the present study, we serosurveyed the exposure of 222 draft horses to different arboviruses in the city of Santa Fe, Argentina. Plaque reduction neutralization tests confirmed exposure to Fort Sherman virus (FSV), Saint Louis encephalitis virus (SLEV), West Nile virus (WNV), and Río Negro virus (RNV). Apparently, Western and Eastern equine encephalitis viruses did not circulate in the population tested. The confirmation of five seroconversions for WNV, FSV, and SLEV and the association between prevalence and age are indicative of recent circulation. These results highlight the importance ...
León B, Jiménez-Sánchez C, Retamosa-Izaguirre M.Venezuelan equine encephalitis virus (VEEV) is an arbovirus transmitted by arthropods, widely distributed in the Americas that, depending on the subtype, can produce outbreaks or yearly cases of encephalitis in horses and humans. The symptoms are similar to those caused by dengue virus and in the worst-case scenario, involve encephalitis, and death. MaxEnt is software that uses climatological, geographical, and occurrence data of a particular species to create a model to estimate possible niches that could have these favorable conditions. We used MaxEnt with a total of 188 registers of VEEV pr...
Fares W, Gdoura M, Dhrif H, Touzi H, Hogga N, Hannachi N, Mhalla S, Kacem S, Karray H, Bougatef S, Ben-Alaya N, Triki H.West Nile Virus (WNV) is an arbovirus transmitted by mosquito bite involving birds as reservoirs, humans and equines as accidental hosts. Eight distinct lineages (WNV-1 to WNV-8) have been identified: WNV-1 and WNV-2 infect humans and animals, and WNV-3 to WNV-8 have been identified only in vectors. WNV has been implicated in neuroinvasives infections, especially meningitis and encephalitis. Tunisia experienced three epidemics in 1997, 2003 and 2012. Serological studies on humans, equines and birds as well as the detection of the virus in the vector favour a fairly frequent circulation in the ...
Carrera JP, Pittí Y, Molares-Martínez JC, Casal E, Pereyra-Elias R, Saenz L, Guerrero I, Galué J, Rodriguez-Alvarez F, Jackman C, Pascale JM....Human cases of Madariaga virus (MADV) infection were first detected during an outbreak in 2010 in eastern Panama, where Venezuelan equine encephalitis virus (VEEV) also circulates. Little is known about the long-term consequences of either alphavirus infection. Methods: A follow-up study of the 2010 outbreak was undertaken in 2015. An additional survey was carried out 2 weeks after a separate 2017 alphavirus outbreak in a neighboring population in eastern Panama. Serological studies and statistical analyses were undertaken in both populations. Results: Among the originally alphavirus-seronegat...
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...
Kotelevska TM, Pryimenko NO, Dubynska HM, Iziumska OM, Koval TI, Pikul KV, Purdenko TY.West Nile Fever (WNF) is the most common arbovirus infection caused by West Nile Virus (WNV), which has been responsible for numerous epidemic outbreaks of disease among humans, birds and horses on all continents, with the exception of Antarctica, over the past two decades. On the territory of Ukraine, the earliest reports of cases of WNV circulation in humans and birds relate to the 70s of the XX century. In Poltava region WNF was first registered in 2011. Though the epidemiological and clinical patterns of WNF in Ukraine and Poltava region remain understudied, primarily due to the lack of al...
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...
Salat J, Ruzek D.Tick-borne encephalitis (TBE), a disease caused by tick-borne encephalitis virus (TBEV), represents a serious neural infection of humans in Europe and Asia. The main reservoir hosts of TBEV are ticks, rodents and insectivores, but domestic animals may also be infected with the virus. This review summarizes what is known about TBE in domestic species (e.g., dogs, horses), in which infection may manifest with clinical signs similar to those seen in severe human cases. We also focus on TBE in ruminants where TBE infections are typically asymptomatic and do not cause health problems in the infecte...
Torquato RBC, Iamamoto K, Fernandes ER, Achkar S, Silva SR, Katz ISS, Guedes F.Laboratory diagnosis of rabies in equines is essential for distinguishing the disease from other sources of encephalitis. Diagnosis by conventional techniques such as a direct fluorescent antibody test (dFAT) or viral isolation in mice or cell culture can be difficult, and the application of molecular biological methods may be necessary. We performed an indirect rapid immunohistochemistry test (iRIT) for the detection of the rabies virus (RABV) antigen in the central nervous system (CNS) of equines and compared the results with those of other diagnostic techniques. We reviewed result records f...
Camino E, Schmid S, Weber F, Pozo P, de Juan L, König M, Cruz-Lopez F.Tick-borne encephalitis virus (TBEV) and louping-ill virus (LIV) are two closely related zoonotic flaviviruses leading to neurological diseases and belonging to the tick-borne encephalitis (TBE) serocomplex. Both viruses are transmitted by the same ixodid tick vector, Ixodes ricinus. Due to global warming affecting vector biology and pathogen transmission, the viruses pose an emerging threat for public health in Europe and Asia. These flaviviruses share some hosts, like sheep, goats and humans, although the main hosts for LIV and TBEV are sheep and small rodents, respectively. Whereas LIV has ...
León B, Käsbohrer A, Hutter SE, Baldi M, Firth CL, Romero-Zúñiga JJ, Jiménez C.Eastern equine encephalitis and Venezuelan equine encephalitis are endemic neglected tropical diseases in the Americas, causing encephalitis in both horses and humans. In 2013, a cross-sectional study was performed in 243 horses located in the highlands and lowlands throughout Costa Rica. Serum samples were analyzed with an IgG ELISA and confirmed by the plaque-reduction neutralization test (PRNT80). Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) overall seroprevalences by the PRNT80 were 36% (95% confidence interval [CI]: 29.9-42.5; 78/217 horses) and...
Steyn J, Fourie I, Steyl J, Williams J, Stivaktas V, Botha E, van Niekerk S, Reininghaus B, Venter M.Alphaviruses from Africa, such as Middelburg virus (MIDV), and Sindbis virus (SINV), were detected in horses with neurologic disease in South Africa, but their host ranges remain unknown. We investigated the contribution of alphaviruses to neurologic infections and death in wildlife and domestic animals in this country. During 2010-2018, a total of 608 clinical samples from wildlife and nonequine domestic animals that had febrile, neurologic signs or unexplained deaths were tested for alphaviruses. We identified 32 (5.5%) of 608 alphavirus infections (9 SINV and 23 MIDV), mostly in neurotissue...
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...
Avila VA, López-García Y, Hernández-Castro R, Salas-Garrido CG, Ramírez-Lezama J, Calderón-Villa R, Martínez-Chavarría LC.Aberrant nematode larval migration in the CNS of horses is rare but frequently fatal; one of the main etiological agents involved in this illness is Halicephalobus gingivalis. This soil nematode has been associated with several fatal equine meningoencephalitis reports worldwide; however, it had never been diagnosed in horses of Mexico. A 10 year-old Andalusian horse presented dysphagia, fever, weakness, prostration and ataxia; the patient expired during the medical attention. Post mortem examination was performed and no gross alterations were found. Histopathology revealed meningoencephalitis...
Guzmán C, Calderón A, Oviedo T, Mattar S, Castañeda J, Rodriguez V, Moraes Figueiredo LT.Venezuelan equine encephalitis virus (VEEV) is an alphavirus that causes encephalitis with a high impact on public health in Latin America. However, only in Guatemala, Trinidad and Tobago, and Mexico have found antibodies in VEEV in bats, using immunohistochemistry, the sensitivity and specificity are improved; thus, it is better for demonstrating natural infection in bats as potential hosts. This study aimed to determine the presence of VEEV in tissues of frugivorous bats. Methods: A prospective descriptive cross-sectional study with a non-probabilistic sampling was carried out in 12 localiti...
Klaus C, Hörügel U, Hoffmann B, Beer M.During a routine examination of 130 horse sera from 13 herds in Thuringia one TBEV antibody positive serum - with a very high titre - could be detected. The horse had been bought from a holding in Bavaria, and was reported to have clinical signs that may have been caused by a TBEV infection. To identify the source of the suspected TBEV infection, ticks from the surroundings of the barn in Thuringia as well as horse sera and ticks from two herds in Bavaria were examined. In the holding in Bavaria, where the horse was kept before, two out of ten horse sera were found to be TBEV antibody positive...
Lecollinet S, Pronost S, Coulpier M, Beck C, Gonzalez G, Leblond A, Tritz P.Neurological disorders represent an important sanitary and economic threat for the equine industry worldwide. Among nervous diseases, viral encephalitis is of growing concern, due to the emergence of arboviruses and to the high contagiosity of herpesvirus-infected horses. The nature, severity and duration of the clinical signs could be different depending on the etiological agent and its virulence. However, definite diagnosis generally requires the implementation of combinations of direct and/or indirect screening assays in specialized laboratories. The equine practitioner, involved in a missi...
Prow NA.West Nile virus (WNV) is a mosquito-borne virus responsible for outbreaks of viral encephalitis in humans and horses, with particularly virulent strains causing recent outbreaks of disease in Eastern Europe, the Middle East and North America. A strain of WNV, Kunjin (WNVKUN), is endemic in northern Australia and infection with this virus is generally asymptomatic. However in early 2011, an unprecedented outbreak of encephalitis in horses occurred in south-eastern Australia, resulting in mortality in approximately 10%-15% of infected horses. A WNV-like virus (WNVNSW2011) was isolated and found ...
Kumar B, Manuja A, Gulati BR, Virmani N, Tripathi BN.Zoonotic diseases are the infectious diseases that can be transmitted to human beings and vice versa from animals either directly or indirectly. These diseases can be caused by a range of organisms including bacteria, parasites, viruses and fungi. Viral diseases are highly infectious and capable of causing pandemics as evidenced by outbreaks of diseases like Ebola, Middle East Respiratory Syndrome, West Nile, SARS-Corona, Nipah, Hendra, Avian influenza and Swine influenza. Unassigned: Many viruses affecting equines are also important human pathogens. Diseases like Eastern equine encephalitis (...
Giannitti F, Diab S, Mete A, Stanton JB, Fielding L, Crossley B, Sverlow K, Fish S, Mapes S, Scott L, Pusterla N.Equine coronavirus (ECoV) is a Betacoronavirus recently associated clinically and epidemiologically with emerging outbreaks of pyrogenic, enteric, and/or neurologic disease in horses in the United States, Japan, and Europe. We describe the pathologic, immunohistochemical, ultrastructural, and molecular findings in 2 horses and 1 donkey that succumbed to natural infection with ECoV. One horse and the donkey (case Nos. 1, 3) had severe diffuse necrotizing enteritis with marked villous attenuation, epithelial cell necrosis at the tips of the villi, neutrophilic and fibrinous extravasation into th...
Chung DH, Jonsson CB, Tower NA, Chu YK, Sahin E, Golden JE, Noah JW, Schroeder CE, Sotsky JB, Sosa MI, Cramer DE, McKellip SN, Rasmussen L, White EL....Alphaviruses present serious health threats as emerging and re-emerging viruses. Venezuelan equine encephalitis virus (VEEV), a New World alphavirus, can cause encephalitis in humans and horses, but there are no therapeutics for treatment. To date, compounds reported as anti-VEEV or anti-alphavirus inhibitors have shown moderate activity. To discover new classes of anti-VEEV inhibitors with novel viral targets, we used a high-throughput screen based on the measurement of cell protection from live VEEV TC-83-induced cytopathic effect to screen a 340,000 compound library. Of those, we identified...
Bilzer T, Planz O, Lipkin WI, Stitz L.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...
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 ...
Taylor KG, Paessler S.Equine encephalids have high mortality rates and represent a significant zoonotic public health threat. Of these the most pathogenic viruses to equids are the alphaviruses in the family Togaviridae. The focus of this review Venezualen equine encephalitis virus (VEEV) has caused the most widespread and recent epidemic outbreaks of disease. Circulation in naturally occuring rodent-mosquito cycles, results in viral spread to both human and equine populations. However, equines develop a high titer viremia and can transmit the virus back to mosquito populations. As such, the early recognition and c...
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.
Roche SE, Wicks R, Garner MG, East IJ, Paskin R, Moloney BJ, Carr M, Kirkland P.To provide an overview and descriptive analysis of the 2011 arboviral disease epidemic in horses that involved three important Australian mosquito-borne viruses: Murray Valley encephalitis virus, West Nile virus (Kunjin strain) and Ross River virus. Methods: Data from states affected between January and June 2011 were collated and comprised reports of horses showing signs of neuromuscular disease and the associated laboratory findings. A summary of the data is presented, together with a spatiotemporal analysis of cases and preliminary assessment of rainfall patterns and case distribution. Resu...
Weaver SC, Powers AM, Brault AC, Barrett AD.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...
Iversson LB, Silva RA, da Rosa AP, Barros VL.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...
Kinney RM, Tsuchiya KR, Sneider JM, Trent DW.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...
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...
Sudia WD, Newhouse VF, Beadle ID, Miller DL, Johnston JG, Young R, Calisher CH, Maness K.A major epidemic of Venezuelan equine encephalitis occurred in south Texas in the summer of 1971. More than 1500 equines died of VEE in Texas, and 110 human cases with no deaths were reported. Vector studies in south Texas and northern Tamaulipas revealed that the overall mosquito infection rates during the peak of the epidemic were about 1:100, one of the highest rates observed for a major epidemic. Mosquito infection rates of this magnitude could easily explain the intensity of VEE outbreaks in both equines and man. A total of 943 VEE virus isolations were made from mosquitoes. Eight of the ...
Pauvolid-Corrêa A, Juliano RS, Campos Z, Velez J, Nogueira RM, Komar N.The Pantanal hosts diverse wildlife species and therefore is a hotspot for arbovirus studies in South America. A serosurvey for Mayaro virus (MAYV), eastern (EEEV), western (WEEV) and Venezuelan (VEEV) equine encephalitis viruses was conducted with 237 sheep, 87 free-ranging caimans and 748 equids, including 37 collected from a ranch where a neurologic disorder outbreak had been recently reported. Sera were tested for specific viral antibodies using plaque-reduction neutralisation test. From a total of 748 equids, of which 264 were immunised with vaccine composed of EEEV and WEEV and 484 had n...
Rossi SL, Russell-Lodrigue KE, Killeen SZ, Wang E, Leal G, Bergren NA, Vinet-Oliphant H, Weaver SC, Roy CJ.Venezuelan equine encephalitis virus (VEEV) is an arbovirus endemic to the Americas that is responsible for severe, sometimes fatal, disease in humans and horses. We previously described an IRES-based VEE vaccine candidate based up the IE serotype that offers complete protection against a lethal subtype IE VEEV challenge in mice. Here we demonstrate the IRES-based vaccine's ability to protect against febrile disease in cynomolgus macaques. Vaccination was well tolerated and elicited robust neutralizing antibody titers noticed as early as day 14. Moreover, complete protection from disease chara...
Ulbert S.West Nile virus (WNV) is a zoonotic virus that circulates in birds and is transmitted by mosquitoes. Incidentally, humans, horses and other mammals can also be infected. Disease symptoms caused by WNV range from fever to neurological complications, such as encephalitis or meningitis. Mortality is observed mostly in older and immunocompromised individuals. In recent years, epidemics caused by WNV in humans and horses have become more frequent in several Southern European countries, such as Italy and Greece. In 1999, WNV was introduced into the USA and spread over North America within a couple o...
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...
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...
Komar N, Panella NA, Boyce E.We evaluated West Nile (WN) virus seroprevalence in healthy horses, dogs, and cats in New York City after an outbreak of human WN virus encephalitis in 1999. Two (3%) of 73 horses, 10 (5%) of 189 dogs, and none of 12 cats tested positive for WN virus-neutralizing antibodies. Domestic mammals should be evaluated as sentinels for local WN virus activity and predictors of the infection in humans.
Gonzalez-Salazar D, Estrada-Franco JG, Carrara AS, Aronson JF, Weaver SC.To assess the role of horses as amplification hosts during the 1993 and 1996 Mexican Venezuelan equine encephalitis (VEE) epizootics, we subcutaneously infected 10 horses by using four different equine isolates. Most horses showed little or no disease and low or nonexistent viremia. Neurologic disease developed in only 1 horse, and brain histopathologic examination showed meningeal lymphocytic infiltration, perivascular cuffing, and focal encephalitis. Three animals showed mild meningoencephalitis without clinical disease. Viral RNA was detected in the brain of several animals 12-14 days after...
Rodrigues A, Fighera RA, Souza TM, Schild AL, Barros CS.The clinical signs and pathology of the central nervous system in 9 horses with naturally occurring neurologic disease due to Trypanosoma evansi are described. The clinical course was 2 to 20 days; clinical signs included marked ataxia, blindness, head tilt and circling, hyperexcitability, obtundity, proprioceptive deficits, head pressing, and paddling movements. Grossly, asymmetric leukoencephalomalacia with yellowish discoloration of white matter and flattening of the gyri were observed in the brain of 7 of 9 horses. Histologically, all 9 horses had necrotizing encephalitis that was most sev...
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...
Tauro LB, Rivarola ME, Lucca E, Mariño B, Mazzini R, Cardoso JF, Barrandeguy ME, Teixeira Nunes MR, Contigiani MS.Bunyamwera virus (BUNV) is the prototype virus for both the Orthobunyavirus genus and the Bunyaviridae family. Different strains of BUNV have been associated with clinical diseases in domestic animals, mainly ruminants. During 2013, in Argentina's Santa Fe Province, three new isolates of BUNV were recovered from the brain and spleen of two horses with encephalitis, and from the brain of an aborted equine fetus. This isolation of BUNV from domestic animals provided the first association of BUNV infection with disease of the central nervous system and abortion in equines in Argentina.
Ostlund EN, Andresen JE, Andresen M.WNV encephalitis in horses, previously reported in Africa, Asia, and Europe, occurred for the first time in the Western Hemisphere in 1999. The causative agent, WNV, is a flavivirus maintained in nature by a bird-mosquito cycle. The disease in horses is manifested primarily by ataxia of variable severity. Outbreaks of encephalitis may have a case fatality rate in excess of 40%, although this virus infection is inapparent in some horses. Early evidence indicates that WNV has overwintered in the northeastern United States and poses a threat for future disease occurrences in horses. No vaccine is...
Amaya M, Keck F, Lindquist M, Voss K, Scavone L, Kehn-Hall K, Roberts B, Bailey C, Schmaljohn C, Narayanan A.Many viruses have been implicated in utilizing or modulating the Ubiquitin Proteasome System (UPS) to enhance viral multiplication and/or to sustain a persistent infection. The mosquito-borne Venezuelan equine encephalitis virus (VEEV) belongs to the Togaviridae family and is an important biodefense pathogen and select agent. There are currently no approved vaccines or therapies for VEEV infections; therefore, it is imperative to identify novel targets for therapeutic development. We hypothesized that a functional UPS is required for efficient VEEV multiplication. We have shown that at non-tox...
Pant GR.Japanese encephalitis (JE) is an emerging disease of animals and humans in Nepal. A serological study for antibody to JE virus was conducted in Nepal from September 2003 to August 2004 by collecting 280 sera from pigs, ducks, and horses covering 10 districts of the country. These sera were tested by performing competitive enzyme-linked immunosorbent assay for the detection of antibodies against JE virus. The total number of tested sera was 280, of which 43.92% were found positive for the presence of antibodies against JE virus infection in Nepal. Sero-prevalence of JE in pigs, ducks, and horse...
