Epizootic diseases refer to outbreaks of infectious diseases that affect a large number of animals within a specific population, region, or period. In horses, these outbreaks can be caused by various pathogens, including viruses, bacteria, and parasites. The study of epizootics in equine populations involves understanding the transmission dynamics, environmental factors, and host-pathogen interactions that contribute to the spread of disease. Researchers focus on identifying the causes and impacts of these outbreaks, as well as developing strategies for prevention, control, and management. This page compiles peer-reviewed research studies and scholarly articles that explore the epidemiology, pathogenesis, and control measures related to epizootic diseases in horses.
Dollahite JW, Younger RL, Crookshank HR, Jones LP, Petersen HD.Lead acetate was fed to 4 groups of 2 horses each to study chronic lead intoxication. A 5th group of 3 horses was maintained as controls. The leas was fed in capsules, with the minimum dosage of 6.25 mg/kg/day of lead as lead acetate (group I). The dose was increased from group I through group IV in an approximate geometric series, with each group being given about 125% of the dose given the previous group. These doses were given for 105 days, a period designated as phase 1. Since clinical signs were not observed after 105 days, the doses were increased and fed for an additional 190 days (days...
Dietz WH, Alvarez O, Martin DH, Walton TE, Ackerman LJ, Johnson KM.Forty-five horses were infected peripherally or intrathecally with enzootic or epizootic strains of Venezuelan equine encephalomyelitis (VEE) virus. Low titers of virus appeared in cerebrospinal fluid (CSF) after peripheral inoculation of enzootic or epizootic VEE virus strains. Intrathecal infection with either epizootic or enzootic VEE virus produced higher titers of virus in CSF than did peripheral infection. In contrast to peripheral infections with enzootic strains, intrathecal infections with these strains caused death. The animals that died had widespread histopathologic changes and lar...
Tekerlekov P, Dilovski M, Enchev S, Peneva I.Coggins' immune diffusion test was modified, and was applied as a screening one in the study of the epizootic status. The positive reactions were characterized by the production of a precipitation line between the antigen and the respective serum that was tested. The appearance of such a line was associated with that formed with the use of the positive control serum, pointing to a reaction of identity. With the weakly positive reactions the ends of the precipitin lines, formed with the use of the positive control serum, were found to deviate slightly toward the site where the antigen had been ...
Goto H, Shimizu K.The first outbreak of equine influenza (EI) infection in Japan was recognized during the period December 1971 to January 1972 [1, 6]. No evidence of the disease had been found before then [2,6]. The etiological agent of this epizootic was identified by hemagglutination-inhibition (HI) and neutralization tests with chicken or ferret antiserum as the subtype 2 of EI virus (6, 7). However, the isolate, A/equine/Tokyo/71 (Tokyo) strain, was not completely identical to the prototypic A/equine/Miami /63 (Miami) strain of the subtype 2, since antibody responses of convalescent horses were 2 to 16 tim...
Berezin VV.Virologic and serological surveys of wild vertebrates carried out in various provinces of Cuba demonstrated definitely that birds were the main hosts of eastern equine encephalomyelitis (EEE) virus in this territory. Fifteen strains of this virus were isolated from 8 species of birds belonging to 5 orders. Isolation of EEE virus from the blood of the endemic genus of iguanas indicates a certain role of cold-blooded animals in the ecology of this agent. Active EEE virus foci have been found in 4 provinces of the Republic of Cuba: Pinar del Rio, Havana, Matanzas and Las Villas. Isolation of a nu...
Hayes CG, Wallis RC.Western equine encephalomyelitis (WEE) has been recognized as a serious public health problem in western North America for more than 30 years. WEE appears to exist endemically in numerous foci in that region, with a low incidence rate among humans. Severe outbreaks, however, have occurred periodically. For example, during 1941 a severe epidemic involving more than 3000 cases in humans occurred in North Dakota, Minnesota, and in the adjacent areas of Canada. The case fatality rate ranged from 8% to 15%. Epizootics among horses are more common. More than 600 cases of WEE were diagnosed among hor...
Young JB.An epizootic of anthrax in Eastern Falls County, Texas, killed at least 238 animals during a 6-week period ending July 31, 1974. Infection appeared to be caused by the ingestion of contaminated soil and grass in the drought-stricken central Texas area. The participation of the Texas Department of Agriculture, the Texas National Guard, and other state agencies was of great assistance to the Texas Animal Health Commission in handling the epizootic and panic stricken public. Use of the unencapsulated Sterne strain spore vaccine was credited with preventing many livestock losses in the area. Conta...
Zakopal J, Pour L.During the epizootic spreading in Europe, equine influenza was brought in also into Czechoslovakia. The disease gradually spread from Slovakia (where horses were isolated after a trip abroad) to race horses throughout the country. The serological examination by the IH test showed that, again, the A equi 1/Praha 56 virus was the causative agent of the infection. The application of the Grippeguin vaccine from France was effective. No clinical manifestations of the disease were observed in two mares from one farm that had not been vaccinated although they had been in the focus of infection. Howev...
Calisher CH, Maness KS.During the summer and fall of 1971, epizootic and epidemic Venezuelan equine encephalitis was detected in Texas. Isolates of epizootic (IB) and vaccine (TC-83) strains were distinguished by virulence of the former for guinea pigs. Vaccine virus was isolated from 1 to 14 days after vaccination and neutralization tests demonstrated the appearance of antibody about a week after vaccination. Viremia titers of subtype IB in horses ranged from 2.2 to 8.3 log10 suckling mouse intracranial 50% lethal doses per ml. Of 101 equines from which Venezuelan equine encephalitis virus (IB or TC-83) strains wer...
Dutta SK, Shipley WD.Foals (farms 1 and 2) and mares (farms 1 and 3) vaccinated with a commercially available rhinopneumonitis vaccine were tested for the level of antibodies and for protection against the natural infection. The serum-neutralization (SN) antibody titers against equine herpesvirus type 1 were 1:8 or less in the majority of foals and 1:16 or higher in about 10%. The level of the nasal secretory antibody in the foals (farm 2) was less than 1:4. The vaccinated foals did not show any apparent respiratory tract infection for about 6 months and then an epizootic of respiratory tract disease appeared on f...
Calisher CH, Sasso DR, Sather GE.During 1971, an epizootic of Venezuelan equine encephalitis (VEE) reached the United States. Laboratory tests were performed on a large number of sick, healthy, unvaccinated, and vaccinated horses. Neutralization (N) tests in cell cultures revealed that 153 of 193 (79.3%) equines outside the state of Texas and 175 of 204 (85.8%) within Texas (82.6% overall) had detectable N antibody to VEE virus a week or more after vaccination. Twenty-six of 40 (65%) non-Texas equines and 18 of 29 (62%) Texas equines which had no detectable antibody against VEE virus a week or more after vaccination had N ant...
Walton TE, Alvarez O, Buckwalter RM, Johnson KM.Ten horses (Equus caballus) were vaccinated with strain TC-83 Venezuelan equine encephalomyelitis (VEE) virus vaccine. Febrile responses and leukopenia due to a reduction of lymphocytes and neutrophils were observed in all animals. Viremias were demonstrable in eight horses, with a maximum of 10(3.5) median tissue culture infectious dose units per ml of serum in two horses. Clinical illness with depression and anorexia were observed in five horses. Neutralizing (N), hemagglutination-inhibiting, and complement-fixing antibodies to the vaccine virus were demonstrable by 5, 6.5, and 7 days, respe...
Pereira HG, Takimoto S, Piegas NS, do Valle LA.Influenza equine (Heq2Neq2) strains isolated during the course of epizootics observed in Guanabara (Rio de Janeiro) and São Paulo, Brazil, in July-October 1969 were shown to differ antigenically from earlier strains of the same subtype (A/equine/Miami/1/63 (Heq2Neq2)). The difference could be clearly demonstrated in haemagglutination inhibition tests performed with postinfection horse or ferret sera but not with hyperimmune rooster sera. Antibody responses of diseased horses were higher and more frequent against current isolates than against strain equine/Miami/1/63. Some animals also showed ...
Laegreid WW.African horsesickness (AHS) is a very serious, non-contagious disease of horses and other solipeds caused by an arthropod-borne orbivirus of the family Reoviridae. The epizootic nature of the disease makes rapid, accurate diagnosis of AHS absolutely essential. Currently, diagnosis of AHS is based on typical clinical signs and lesions, a history consistent with vector transmission and confirmation by laboratory detection of virus and/or anti-AHS virus antibodies. The clinicopathologic presentation of AHS, current and next generation laboratory diagnostic methods are discussed.
Hommel D, Bollandard F, Hulin A.Venezuelan equine encephalitis (VEE) is a mosquito-borne viral disease that occurs in equine species and in man. The strains can be grouped epidemiologically into two major categories: enzootic and epizootic. Enzootic strains cause sporadic human disease and are not associated with disease among equines. These strains are found throughout Florida. Central America, northern South America and Brazil. Epizootic strains are associated with enormous morbidity and mortality in equine species. In man, VEE virus infections are largely asymptomatic and in children and young adults there is an increased...
Chabchoub A, Landolsi F, Zientara S, Amira A, Mejri M, Ghorbel A, Ghram A.The authors describe an equine influenza epizootic that occurred in Tunisia during February and March 1998 in the regions of Tozeur, Sousse and Tunis. They relate the symptoms, the different stages of diagnosis and the serological results.
Goto H, Shimizu K, Taya Y, Noda H, Tokunaga T.The antibody responses to equine influenza viruses were investigated during a postepizootic period of the disease. Serum samples were collected from a total of 128 horses on three occasions during the years 1967-77. No significant increase of hemagglutination-inhibition antibody titers to subtypes 1 and 2 of equine influenza virus were detected in any of the sera tested. The maternal hemagglutination-inhibition antibody titers of foals decreased over a four month interval. A marked increase of the titers was recognized in only the equine influenza virus vaccinated horses. These findings sugges...
Baker EF, Sasso DR, Maness K, Prichard WD, Parker RL.In 1971, more than 370 horses in south Texas were studied with respect to their clinical, virologic, and neutralizing antibody responses to vaccination with Venezuelan equine encephalomyelitis (VEE) strain TC-83. This study confirms reported findings that the vaccine used in the 1971 epizootic in the lower Rio Grande Valley of Texas was safe and efficacious. Vaccinal virus viremia titers were generally below the postulated infection threshold of epizootic vectors. In general, reactions to the vaccine were minimal and transient, with no observed abortions or deaths attributable to use of the va...
Calisher CH, Maness KS.During the summer and fall of 1971, epizootic and epidemic Venezuelan equine encephalitis was detected in Texas. Isolates of epizootic (IB) and vaccine (TC-83) strains were distinguished by virulence of the former for guinea pigs. Vaccine virus was isolated from 1 to 14 days after vaccination and neutralization tests demonstrated the appearance of antibody about a week after vaccination. Viremia titers of subtype IB in horses ranged from 2.2 to 8.3 log10 suckling mouse intracranial 50% lethal doses per ml. Of 101 equines from which Venezuelan equine encephalitis virus (IB or TC-83) strains wer...
Dollahite JW, Younger RL, Crookshank HR, Jones LP, Petersen HD.Lead acetate was fed to 4 groups of 2 horses each to study chronic lead intoxication. A 5th group of 3 horses was maintained as controls. The leas was fed in capsules, with the minimum dosage of 6.25 mg/kg/day of lead as lead acetate (group I). The dose was increased from group I through group IV in an approximate geometric series, with each group being given about 125% of the dose given the previous group. These doses were given for 105 days, a period designated as phase 1. Since clinical signs were not observed after 105 days, the doses were increased and fed for an additional 190 days (days...
Oxburgh L, Berg M, Klingeborn B, Emmoth E, Linné T.The antigenic properties of H3N8 equine influenza virus from the Swedish epizootic of 1991 differ from those of A/eq 2/Fontainebleau/79 (representative of the Swedish vaccine strain) in hemagglutination inhibition tests. The amino acid sequence of the hemagglutinin (HA) of an isolate from the 1991 outbreak was deduced from the nucleotide sequence and comparison was made to the A/eq 2/Fontainebleau/79 strain. Twenty-three amino acid substitutions were found, 10 mapping onto areas of the HA known to bind antibodies in human H3 influenza viruses. The amino acid changes together with the serologic...
Kaiser A, Meier HP, Straub R, Gerber V.Equine Infectious Anemia (EIA) is a reportable, eradicable epizootic disease caused by the equine lentivirus of the retrovirus family which affects equids only and occurs worldwide. The virus is transmitted by blood, mainly by sanguivorous insects. The main symptoms of the disease are pyrexia, apathy, loss of body condition and weight, anemia, edema and petechia. However, infected horses can also be inapparent carriers without any overt signs. The disease is diagnosed by serological tests like the Coggins test and ELISA tests. Presently, Switzerland is offi cially free from EIA. However, Switz...
Morier L, Cantelar N, Soler M.Eastern Equine Encephalitis (EEE) was in Cuba before the 1940s; the virus has been isolated from horses, birds, and rodents during epizootic as well as interepizootic periods. The only isolation of Western Equine Encephalitis (WEE) virus was from a sick pigeon found in the vicinity of Havana University. Both viruses can cause human disease; the isolation of WEE virus from the centre of an urban area emphasises the need for the prompt isolation and rapid identification of these agents. The object of this work was to compare the sensitivity of a continuous cell line (XL-2) from the toad, Xenopus...
Justines G, Oro G, Alvarez O.The P-676 and MF-8 epizootic strains of Venezuelan equine encephalitis (VEE) virus were found to contain a minute plaque (MP), different from the predominant small plaque (SP) present in these virus strains. The MP and SP were stable after passages in Vero cells, mice, or horses. Equines were inoculated with the SP or MP of the P-676 and MF-8 strains. Inoculation of either P-676 SP or MP into horses induced high fever and viremia but no signs of encephalitis or death. Four horses infected with MF-8 SP became very ill, with high fever and viremia; three of the inoculated animals died. Four hors...
Walton TE, Holbrook FR, Bolivar-Raya R, Ferrer-Romero J, Ortega MD.The arthropod-borne virus (arbovirus) diseases of livestock have worldwide impact. The prevention of an introduction of an exotic disease and the control of one subsequent to an introduction will require the attention, cooperation, and support of the livestock industry, regulatory agencies, and researchers. The most effective protection of our livestock industries is to prevent the introduction of an exotic disease agent. This implies complete restriction of animal imports and exports. However, "zero risk" is an unacceptable option in today's world of internationally integrated and interdepend...
Docherty DE, Samuel MD, Egstad KF, Griffin KM, Nolden CA, Karwal L, Ip HS.After the 2001 occurrence of West Nile virus (WNV) in Wisconsin (WI), we collected sera, during 2003-2006, from south-central WI mesopredators. We tested these sera to determine WNV antibody prevalence and geometric mean antibody titer (GMAT). Four-fold higher antibody prevalence and 2-fold higher GMAT in 2003-2004 indicated greater exposure of mesopredators to WNV during the apparent epizootic phase. The period 2005-2006 was likely the enzootic phase because WNV antibody prevalence fell to a level similar to other flaviviruses. Our results suggest that, in mesopredators, vector-borne transmis...
Wiebe ME, Scherer WF, Peick WJ.Ninety-four strains of Venezuelan encephalitis (VE) virus isolated from sentinel hamsters exposed in the Middle American countries of Mexico, Guatemala, Belize, and Honduras were examined for the presence of virions with marker characteristics of strains that cause large epidemics and equine epizootics. Thirty-four strains came from before and 60 strains came from after the Middle American epidemics and equine epizootics of 1966 and 1969-1972. Twenty-three virion clones that resembled epizootic strains by hydroxylapatite chromatography and Vero monkey kidney cell plaque size determinations wer...
Young JB.An epizootic of anthrax in Eastern Falls County, Texas, killed at least 238 animals during a 6-week period ending July 31, 1974. Infection appeared to be caused by the ingestion of contaminated soil and grass in the drought-stricken central Texas area. The participation of the Texas Department of Agriculture, the Texas National Guard, and other state agencies was of great assistance to the Texas Animal Health Commission in handling the epizootic and panic stricken public. Use of the unencapsulated Sterne strain spore vaccine was credited with preventing many livestock losses in the area. Conta...
Sandybayev N, Strochkov V, Beloussov V, Orkara S, Kydyrmanov A, Khan Y, Batanova Z, Kassenov M.Equine influenza (EI) is a highly contagious disease that causes fever and upper respiratory tract inflammation. It is caused by influenza virus A, belonging to the family, with subtypes H3N8 and H7N7. This study presents data on the development of a real-time polymerase chain reaction (RT-PCR) assay using TaqMan probes to detect the H3 subtype of EI virus (EIV). Unassigned: The evaluation of the developed RT-PCR assay involved five strains of EIV as positive controls and ten nasopharyngeal swab samples collected from horses. RNA was isolated using the GeneJet Viral DNA and RNA Purification K...
Medical mycologyDecember 6, 2023
myad124 doi: 10.1093/mmy/myad124
Wernery U, Joseph M, Joseph S, Al Mheiri F.Epizootic equine lymphangitis (EEL) is a chronic fungal disease that affects equids. The causative agent is a dimorphic fungus called Histoplasma capsulatum var farciminosum. H. capsulatum var farciminosum field strain 7 (D 2878/2023) isolated from the eye socket of an EEL Ethiopian horse was sub-cultured on 4 different solid media and incubated at 26°C and 37°C for 6 weeks. Details of growth morphology were recorded and shown in images during 6 weeks of incubation. H. capsulatum var farciminosum grew best at 26°C on all 4 agars, but only on sheep blood agar at 37°C as small, white dry col...
Zakopal J, Pour L.During the epizootic spreading in Europe, equine influenza was brought in also into Czechoslovakia. The disease gradually spread from Slovakia (where horses were isolated after a trip abroad) to race horses throughout the country. The serological examination by the IH test showed that, again, the A equi 1/Praha 56 virus was the causative agent of the infection. The application of the Grippeguin vaccine from France was effective. No clinical manifestations of the disease were observed in two mares from one farm that had not been vaccinated although they had been in the focus of infection. Howev...
