The disease has a nearly 100% infection rate in an unvaccinated horse population that has not been previously exposed to the virus. The incubation time is one to five days.
Horses with horse flu can run a fever, have a dry hacking cough, have a runny nose, and become depressed and reluctant to eat or drink for several days but usually recover in 2 to 3 weeks.
"Vaccination schedules generally require a primary course of 2 doses, 3-6 weeks apart, followed by boosters at 6-12 month intervals. It is generally recognised that in many cases such schedules may not maintain protective levels of antibody and more frequent administration is advised in high-risk situations."
It is a common requirement at shows in Britain that horses are vaccinated against Equine flu and a vaccination card must be produced; the FEI requires vaccination every 6 months.
Definition - An epizootic specific fever of a very debilitating type, with inflammation of the respiratory mucous membrane, and less frequently of other organs, having an average duration of ten to fifteen days, and not conferring immunity from a second attack in subsequent epizootics.
Synonyms - The corresponding disease in man was known to the older physicians as Peripneumonia notha, P. typhoides, P. catarrhalis, Pleuritis humida, Fidris catarrahlis, Catarrhe plumonaire, Catarrhus á contagio, Defluxus catarrjalis, Cephalagia contagiosa, Rheuma epidemicuno, &c. As seen in animals it has received the following designations: Epizootic catarrh, catarrhal fever, gastro-catarrhal fever, mucous fever, gangrenous peripneumonia, epizootic pleuro-pneumonia, entero-pneumo-carditis, epizootic nervous fever, distemper, blitz katarrh, rheumatic catarrh, la grippe, cocote, typhose, septicœmio, &c
Past History - The frequent co-existence of an epizootic catarrh in man and the horse, and to a less extent in other animals, lends some color to the hypothesis that they are due to closely-allied causes. The records of its prevalence in man might therefore be profitably referred to as illustrating the action of such causes at a time when veterinary records are few and imperfect.
Between 415 and 412 before Christ, Hippocrates and Livius report the extraordinary prevalence of catarrhal maladies in Greece and Rome, which Schuurrer and Hæser suppose to have been influenza. Diodorus Siculus reports an epidemic, apparently of the same kind, in the Athenian army in Sicily in 415. Absyrtus, a Greek veterinarian, writing about A. D. 330, describes a disease in the horse having the general characters of influenza. This appears to be the earliest record of such an affection in the lower animals, yet the reports of epidemics at an earlier date almost necessarily imply the existence of the equine malady. Passing over a number of epidemics, we come to the next recorded equine influenza in A.D. 1299. In this year a catarrhal epidemic spread widely in Europe, (Parkes.) The equine disease is thus described by Laurentius Rusius, as it prevailed at Seville: “The horse carried his head drooping, would eat nothing, ran from the eyes, and there was hurried beating of the flanks. The malady was epidemic, and in that year one thousand horses died.”
Six epidemics of influenza are recorded in the fourteenth century, but among animals nothing more than an epizootic quinsy at Rome, from which Rusius, who reports it, lost fifty horses.
We have no distinct evidence of influenza in animals in the fifteenth and sixteenth centuries, though in 1510 and 1580-’81, during the prevalence of cattarrhal epidemics in Europe, animals suffered severely, from what disease is not stated, (Saliua Diversus, Thomas Short.) Solleysel describes an epizootic among the horses of the French army, operating in Germany in 1648, which closely agrees with influenza. It began by fever, great prostration, tears running from the eyes, and a profuse greenish mucous discharge from the nostrils. The appetite was lost and ears cold. Few recovered. This appears to have closely followed the epidemic influenza of 1647, mentioned by Hensinger. In 1688 influenza was epidemic over the whole of Europe, spreading from east to west. In England and Ireland it was immediately preceded by a nasal catarrh, from which horses universally suffered, (Short, Rutty.) In 1693 it again prevailed over the whole of Europe and the British Isles, attacking first horses, and then, after a short time, men, (Webster, Short, Forster.). In 1698, during an epidemic catarrh in France, cattle and horses suffered from what was described as a bilious plague, (Bascom.) The year following influenza prevailed among horses in France, and severely among men and horses in England, (Webster.) In America in the same year horses were first attacked, and afterward men, (Forster.)
The year 1707, remarkable for an eruption of Vesuvius and the upheaval of a new island in the Ægean Sea, witnessed an epidemic catarrh in Franconia, (Steurlius,) and in England, where horses also suffered, (Short.) A similar eruption, with earthquakes, in 1712, coincided with an epidemic and above all an equine influenza, (Laucisi, Kanold.) In the winter of 1727-’28, horses in Great Britain suffered from epidemic catarrh; in Ireland it attacked man a little later, (Rutty.).
In 1732, seven earthquakes occurred in China, followed by pestilential diseases in man and malignant carbuncular diseases in animals. A little later influenza spread over Europe and America from east to west, (Glugo.) Arbuthnot and others who described it in England remarked upon the sulphurous vapors pervading the atmosphere, and that men and horses were attacked successively. Gibson, who furnishes a full description of the affection in the horse, says that it attacked mainly young or ill conditioned animals, and did not prove fatal. In 1736 and 1737 it again prevailed in England, attacking men and horses. Short, who records this, mentions an eruption of Vesuvius in the latter year. In 1740, 1742, and 1743 violent sore throats prevailed in man, horse, and ox, (Huxham, Rutty, Faulkener;) but whether due to influenza is not plain. In 1746 and 1750-’51 catarrh was epizootic among horses in Ireland, (Rutty, Osmer;) in 1758 in Scotland and England, attacking man as well, (Whytt, Bascom;) in 1760, after an eruption of Vesuvius, influenza appeared in Great Britain, Ireland, and elsewhere in Europe, attacking first horses, then men, (Bisset, Rutty.) In 1760 it is reported as in Denmark, attacking horses and dogs; and in 1762 in France, Ireland, and other parts of Europe, among horses and men, (Rutty, Bottain.)
In 1767 it prevailed in Europe, and above all in England, where it attacked first dogs and horses, then men, (Forster, Iteunsen;) also in America among horses. It carried off almost all the young horses and colts in New Jersey, and was very ruinous in New England, (Webster.)
In 1776, after a very severe winter and warm summer, with an earthquake in Wales, influenza spread over Europe. Fothergill, Cumming, Glass, Haggarth, and Pultney, in England, and Lorry, in France, noticed that horses and dogs suffered before it attacked human beings. Huzzard speaks of the horses suffering last. Poultry died in great numbers from an epizootic with defluxions from the eyes. In 1780, after eruptions of Vesuvius and Etna, and a terrible earthquake in Taurus, influenza appeared among horses. Huzzard describes it as seen at Paris. Gluge and Hensinger say that it broke out epidemically in September, 1780, in China, and, spreading over Asia, reached Moscow in December, 1781, gained Revel and Western Prussia in February, 1782, and Spain and Italy in August and September. Forster says it prevailed in America in the spring of 1781, and the following year in Europe. Haveman records an equine influenza at the same time in Germany, and Abilgaard leaves a monograph on the disease as it prevailed in the royal stud at Copenhagen. This year was rigorously cold all over Europe. In 1798 influenza again prevailed among horses in England, (Wilkinson, White.)
In 1800 influenza was said to have prevailed at Whampon, in China, whence it was believed to extend over Asia, reaching Europe in 1802 and England in January, 1803, (Gluge.) Though in some places man alone appears to have suffered, in others horses fell victims as well, (Hensinger.) In 1814 this affection prevailed in horses in Switzerland, (Hensinger,) and 1815, in a malignant form, in England, (Wilkinson, Youatt.) It appeared again in an epizootic form in England in 1819, 1823, (Field,) and 1828, (Brown.)
In 1833 it extended over Europe from east to west, attacking men, horses, dogs, and even cats. It prevailed in Courland from January to March, (Possart;) in Pomerania and Saxony in April, (Rhodes, Prinz;) and in France in May, (Compte Rendu de l’Ecole, Vet. d’Alfort.) In England Mr. Hayes describes it as lasting from October, 1832, to March, 1833. It was a “catarrhal fever, joined with inflammation of the lungs and liver and trachea and œsophagus and larynx and pharynx, and the mucous lining membrane of the bowels, frequently with all the symptoms of malignant catarrh, and these in an aggravated form. In some cases there was excessive diarrhœa, the fæces were black liquid mucus, bloody and exceedingly fetid, and accompanied by such extreme debility that the animal could not move without falling; there was quick pulse, injected nose, mouth and gums as red and dry as possible, and resembling a piece of lean dry beef. In some there was excessive anasarca; in others phlegmonous tumors in different parts of the body; in others again there were spasmodic jerkings and lameness in the legs, shoulders, and hips.”
In 1834 it is reported in Brandenburg, (Hensinger,) and in 1835 and 1836 in France and England, (Prinz, Veterinarian.) In the spring of 1845 it again prevailed in England, and in July became complicated by a severe inflammation of the eyes and dropsies beneath the belly and on the legs. (Veterinarian.) During the great influenza epidemic of 1847, it prevailed extensively among horses in Europe, and was unusually prevalent in England in the two following years as well. Since that time it has been especially prevalent in Great Britain, in 1851-’52, 1854, 1856-’57, in the early summers of 1862 and 1863, and in the latter part of 1871.
Past history of the influenza of 1872 - According to information received from Professor A. Smith, veterinary surgeon, Toronto, the first cases occurred in the townships of York, Scarboro’, and Markham, about fifteen miles to the north of that city, among the last days of September. He says, “I think the first cases were noticed among horses running at pasture.”
Cases were seen in the city of Toronto by October 1, and in three days it had attacked nearly all the horses of the street-cars and livery-stables. On October 18 it was reported as general in Montreal and Quebec and throughout the Dominion. Several Canadian horses were introduced into Detroit on October 10 or 11 suffering from what was supposed to be a catarrh. On arrival they were at once placed in a large stable in the city, but almost immediately transferred to a smaller one to guard against the possibility of contagion. Two days later the disease showed itself in the horses occupying the larger stable, and in three days all of these were attacked. Meanwhile it had appeared in the smaller stable as well. No other cases are known to have occurred in the city until October 20, and soon after this it became general. Two of the imported horses were well enough to work from the first, and were constantly on the streets in the business part of the town.
On October 14 it was reported in Buffalo, New York, and was general by October 21. By October 17 Rochester had half its horses ill, and West Batavia bad been attacked.
On October 19 it existed in Syracuse in newly-arrived Canadian horses; on the 22d one hundred to two hundred were sick in boarding and livery stables, and it spread with great rapidity in the country around.
As early as October 20 it was reported in Warren County, Pennsylvania; on October 21 at Depauville, Jefferson County, Attica, Wyoming County, and Steuben County, New York, and Keene, New Hampshire. On October 22 at Brooklyn, New York, Jersey City, and Boston. On October 23 it was prevalent at Newburgh and in the country round New York, in the towns situated on the New York Central Railroad, from Syracuse to Albany inclusive; in Hartford and New Haven, Connecticut; in Block Island, in Providence, and Newport, Rhode Island; in Lunenburgh, Vermont; in Bangor, Portland, and Augusta, Maine; in Washington and Carrollton, Ohio, and in Chicago, Illinois. On October 24 Lexington, Sanilac County, Michigan, and Baltimore, Maryland, were affected. On October 25 the first cases appeared in Oswego, New York, also in Clarkstown, Buckland County, and in Livingston County, New York; Westfield, Massachusetts; Lewistown, Bethel, Topsham, and South Parsonfield, Maine, (at the latter place, which is thirty miles from a city, the first case was a horse from a city stable, and a week later a colt in the same stable.) It was also reported at Corry, Pennsylvania, at this date. On October 26 it reached Sheridan, Chautauqua County, New York, and Pontiac, Michigan. On October 27 it attacked Glens Falls, Catskill, and Poughkeepsie, New York, and Rockville, Tolland County, Connecticut; in the last case it was supposed from Springfield, Massachusetts.
On October 28 the Watertown street-cars were stopped, and the disease had just appeared at Binghamton, New York, Paterson, New Jersey, Philadelphia, Pennsylvania, and Washington, District of Columbia, October 28; in the last place in sick horses brought from the North.
On October 29 it was announced in Washington county, Vermont; in West Chester County, Port Jervis, and Carmel, New York; at Titusville, Pennsylvania, and Columbus, Ohio.
On October 30 it was reported for the first time in Peekskill and Nyack, New York. On the 31st it appeared in Little Genesee, in Rosendale, and Deposit, and in Ithaca, New York, having existed since the 25th in Trumansburgh, ten miles to the northwest of the place last named, and slowly reached Varna, three miles to the east of Ithaca, on November 6. Pittsburgh, Pennsylvania, and New Hope, Pennsylvania, were reached on October 31, the first of these places by five or six horses brought from New York City to the livery stables of Messrs. Moreland and Mitchell; the street-cars had to be stopped on November 5 for the lack of horses. Yet even up to this date Belmont’s horses at Babylon, Long Island, and McDaniels’s at Saratoga, were still reported sound.
On November 1 it reached Kingston, on the west side of the Hudson and Washington County, New York, attacking first the livery and canal horses, contrary to what occurred at Buffalo, where canal horses escaped until October 22. Is this difference to be accounted for by the fact that the canal did not extend into Canada? At the same date it was reported at Germantown and Lancaster, Pennsylvania; Cincinnati, Bucyrus, and Etna, Ohio; Romeo, Michigan; Portsmouth and Chuckatuck, Virginia, and Newark, Delaware, starting in the last case with a horse just arrived from Baltimore, Maryland.
On November 2 it appeared at Adams, Massachusetts; on the 4th at Pittsfield; on the 5th at Great Barrington, and on the 6th at Richmond; all in the Hoosac Valley. On the same date it was observed at Charleston, South Carolina, in town and country at once.
On November 3 it broke out at Elyria, Ohio, confining itself for five days to teams which had been driven to Cleveland; at Goldsborough, North Carolina, and Columbia, South Carolina.
On November 4 it was reported at Springfield, Illinois and in Lehigh County, Pennsylvania, where “it spread like fire along the canal and into the surrounding country.”
On November 5 it was reported in Tioga, Elk, Chester, and Wyoming Counties, Pennsylvania, and at Grand Rapids, Michigan.
On November 6 it reached Cooperstown, Otsego County, New York; Greensburgh, Pennsylvania, and Richmond and Campbell County, Virginia; and on November 7 Butler County, Pennsylvania.
On November 8 it had attacked Montcalm, Livingston, and Ottawa Counties, and Lincoln and Tuscola, Michigan; Ravena, Ohio, and Danville, Virginia, where it prostrated 75 per cent of the horses in twenty-four hours. It was reported, November 9, in Hampton, Virginia, and two severe cases at Johnstown, Cambria County, Pennsylvania, where, however, it did not become general till the 24th, so that these must be considered questionable.
November 10 it existed in Sandusky, Ohio, on November 11, at Marshall, Michigan, Indianapolis, Indiana, and Savannah, Georgia. November 13 it reached Scranton and Forest County, Pennsylvania, Hamilton and Marion, Ohio, and Wilmington and Tarborough, North Carolina, while it had reached its height at Louisville, Kentucky, and Milwaukee, Wisconsin, and was merging into dropsical and other fatal complications in Buffalo, New York, Baltimore, Washington, Philadelphia, and Raleigh, North Carolina.
November 14 it existed at Toledo, Ohio, and Lynchburgh, Virginia, and was nearly universal in Buckingham County and at Wheeling, West Virginia. November 15 it was reported in Mechanicsburg, Grampian Hills, and in Clearfield County, Pennsylvania, in Defiance, Ohio, and Madison, Wisconsin.
November 16, in Beaver County, Pennsylvania, and 17th at Cedar Springs, Clinton County, having traveled northward along the Susquehanna River. It had existed to the southeast and west for several days previously.
November 18 it broke out at Atlanta, Georgia, and Chattanooga, Tennessee. At Nashville, Tennessee, it broke out between the 15th and 20th, and spread slowly, so that exact figures are difficult to arrive it. At this time it prevailed in Giles, Rutherford, Manry, Davidson, and Sumner Counties, at points recently visited by a circus, which came from an infected district. At Memphis, Tennessee, it existed in a mild form on the 19th.
November 21 the street-cars in Augusta, Georgia, were stopped, and the first thirteen cases occurred at Martha Furnace, Blair County, Pennsylvania.
November 24, fifty horses and mules were attacked at once at Johnstown, Cambria County, Pennsylvania.
November 27 the street-cars were stopped at Halifax, Nova Scotia, on account of the disorder; it was reported to be spreading rapidly in New Orleans; and had appeared in Jacksonville, Illinois, Keokuk, Iowa, and Montgomery, Alabama.
November 28 it was reported at Jacksonville, Florida; November 30 it prevailed in Fulton County, Georgia, and Newberry County South Carolina, making a westward progress.
December 2 it broke out in East Saint Louis, Missouri; December 3, in Boonville, Missouri, and Omaha, Nebraska. December 7 it reached Havana, Cuba, attacking native and northern horses alike. On December 14 it had reached its height, many horses were dying, and Mexican horses were being imported by the Spanish government. The outbreak has varied widely in its nature at different places. Sometimes it has spread slowly along the course of railroads or turnpikes, and its progress can be very satisfactorily connected with the intercourse between the different places attacked. In other cases it appears, from the reports, to have struck down a whole city or limited district in twelve or twenty-four hours, and in a manner which it appears impossible to account for otherwise than by some subtle and generally pervading influence. The earliest reports of the disease from many points allege that colts, mares, and other animals, running at grass, have escaped, but later intelligence seldom or never fails to report their sickness. So, too, at Scranton and other mining regions in Pennsylvania the mules working underground kept well for about six days after those on the surface were suffering. The majority of the reports testify that animals at grass in mild weather were later in being attacked, and suffered less than those in regular work and stabled. Yet some report that those at pasture and away from all other horses suffered as early and as severely as those indoors.
The percentage of horses attacked has been variously stated at from 80 to 99. As the reports are mostly written before the disease has quite passed away, it is probable that the latter number is nearest the general average.
The fatality appears to have been from 1 to 2 per cent on a general average, though it has been considerably higher than this in some of the larger cities. The highest reported was at Farmingdale, New York, where it was claimed that 10 per cent of the heavy horses had died. This was, however, drawn from too small a number of cases to be of any value as an average.
(This comment marks the end of a series of direct quotes from the "Report of the Commissioner of Agriculture for the year 1872".)