Ship­ping fever

EQUUS - - Equus -

Even if you only haul your horse on shorter trips, it’s wise to be aware of the fac­tors that can cause pleu­rop­neu­mo­nia and take steps to min­i­mize the risks.

For many of us, haul­ing horses is a happy rit­ual of sum­mer. Wherever we're head­ing—shows or clin­ics, parks or pa­rades—road trips usu­ally mean there's a fun

day ahead, full of ac­tiv­i­ties with our horses. Most of the time, our horses seem to share in our en­thu­si­asm, com­ing down the trailer ramp bright-eyed and ready to go.

Yet for them, as for peo­ple, travel has a po­ten­tial down­side: ex­po­sure to res­pi­ra­tory bugs and other pathogens, par­tic­u­larly when their des­ti­na­tions are crowded with other horses. “It can be sim­i­lar to a per­son catch­ing a cold from the per­son sit­ting next to you on a plane,” says Vir­ginia Buech­ner-Maxwell, DVM, DACVIM, of the Vir­ginia–Mary­land Col­lege of Vet­eri­nary Medicine in Blacksburg, Vir­ginia. And those post-trip snif­fles are usu­ally a mi­nor prob­lem. “If horses get a res­pi­ra­tory in­fec­tion af­ter trans­port, like peo­ple with colds, they usu­ally just get over it. Rest from work may be all that’s needed.”

Some­times, how­ever, a fever and cough that start soon af­ter a trip are early signs of a much more se­ri­ous ill­ness: pleu­rop­neu­mo­nia (com­monly called ship­ping fever), an in­flam­ma­tion of the lungs and the pleu­ral mem­branes lin­ing the chest wall, which can cause fluid to build up in the space be­tween the lungs and the rib cage. “This is no longer sim­ply an up­per res­pi­ra­tory in­fec­tion that clears up in a few days,” Buech­ner-Maxwell says. “If the in­fec­tion has pro­gressed to pleu­rop­neu­mo­nia the re­sult­ing fluid buildup be­tween the chest wall and lungs com­presses and dam­ages the lung tis­sue and can have long term ef­fects or even lead to death if not di­ag­nosed and treated quickly.”

If the in­fec­tion is ad­vanced by the time it is de­tected, the treat­ment reg­i­men can be pro­tracted, ex­pen­sive and at times un­suc­cess­ful. Po­ten­tial com­pli­ca­tions in­clude lamini­tis as well as scar­ring of the lung tis­sues that may limit a horse’s abil­ity to per­form. Chances for a speedy re­cov­ery are best when ag­gres­sive treat­ment is be­gun within the first 48 hours---long be­fore more se­ri­ous out­ward signs of ill­ness are likely to be ev­i­dent.

So even if you only haul your horse on shorter trips, it’s wise to be aware of the fac­tors that can cause ship­ping fever while tak­ing steps to min­i­mize the risks. And call the vet­eri­nar­ian right away if your horse shows any signs of res­pi­ra­tory ill­ness af­ter trans­port.

Ship­ping fever is more likely to oc­cur in horses af­ter they have been in tran­sit for 20 hours or more. That doesn’t mean, how­ever, that horses tak­ing shorter trips have no chance of de­vel­op­ing the prob­lem.


Many sit­u­a­tions, in­clud­ing surgery un­der gen­eral anes­the­sia or re­peated, pro­longed ex­er­tion, can put a horse at risk for pleu­rop­neu­mo­nia, but the con­di­tion is called “ship­ping fever” for a rea­son: Trans­port presents a unique mix of phys­i­cal and psy­cho­log­i­cal stres­sors that can weaken a horse’s de­fenses.

“Ship­ping is stress­ful for horses,” says Amy John­son, DVM, DACVIM, of the Univer­sity of Penn­syl­va­nia School of Vet­eri­nary Medicine, not­ing that, in ad­di­tion to the trans­port it­self, a horse must cope with be­ing sep­a­rated from his home herd and adapt­ing to an un­fa­mil­iar en­vi­ron­ment. “The stress re­sponse with var­i­ous hor­mones and other sub­stances that are re­leased in the body are im­muno­sup­pres­sive. The im­mune sys­tem then can­not fight off the pathogens that ac­cu­mu­late in the lower air­way as ef­fec­tively.”

Then there’s the phys­i­cal side of rid­ing in a trailer or van. A horse’s en­vi­ron­ment dur­ing trans­port may not be any more dusty than his home barn, but if he can’t read­ily lower his head, air­borne par­ti­cles may take a greater toll on his health. “Putting their heads down is es­sen­tial to en­able the nor­mal mu­cocil­iary clear­ance mech­a­nisms in the air­ways to do their job in clear­ing out pathogens and de­bris from the lower air­ways,” says Kather­ine Wil­son, DVM, DACVIM, of the Vir­ginia– Mary­land Col­lege of Vet­eri­nary Medicine. “There have been stud­ies show­ing that even without the trai­ler­ing as­pect, if horses are tied with their heads up for six to 12 hours, they de­velop ac­cu­mu­la­tions of bac­te­ria and in­flam­ma­tory cells in the lower air­ways.”

The du­ra­tion of a trip also mat­ters. Ship­ping fever is more likely to oc­cur in horses af­ter they have been in tran­sit for 20 hours or more. In one 2016 study of 869 horses who trav­eled by air to Hong Kong, 10.8 per­cent de­vel­oped ship­ping fever, and the in­ci­dence was higher among horses ar­riv­ing from Great Bri­tain and the United States than in those from New Zealand and Aus­tralia.

That doesn’t mean, how­ever, that

horses who travel shorter dis­tances have no chance of de­vel­op­ing ship­ping fever. “Many fac­tors can be in­volved,” says Wil­son. “Some stud­ies have looked at travel dis­tances and time, but we’ve also seen res­pi­ra­tory dis­ease in horses that have trav­eled for only a cou­ple of hours. There are also many horses that travel for more than 24 hours and are fine.”


The first in­di­ca­tors of any res­pi­ra­tory ill­ness tend to be sub­tle so it’s wise to keep a close eye on your horse af­ter a trip. Fever is of­ten the ear­li­est sign of trou­ble so check his tem­per­a­ture daily--twice a day, if pos­si­ble---for sev­eral days after­ward.

“Usu­ally within 24 to 72 hours af­ter ship­ping, a horse who is com­ing down with a res­pi­ra­tory in­fec­tion will de­velop a fever,” says Wil­son. “Some­times the first thing the owner no­tices is that the horse is dull and lethar­gic and doesn’t want to eat. These first signs may progress to nasal dis­charge and/or cough­ing but some­times not.”

Other early signs may in­clude an in­creased res­pi­ra­tory rate (the nor­mal rate ranges from eight to 12 breaths per minute), or dis­charge around the eyes. If the pleu­ral mem­branes are af­fected, the re­sult­ing pain may cause a horse to breathe shal­lowly and rapidly, take un­usu­ally short strides and flinch when touched.

Call your vet­eri­nar­ian when you first no­tice the signs of ill­ness. “If it’s a vi­ral in­fec­tion, most horses will re­cover in a few days, but what you don’t want to do is miss the horse that has some­thing more go­ing on,” says Buech­ner-Maxwell. “If a horse is cough­ing and has a nasal dis­charge and a fever, con­sult with your vet­eri­nar­ian. This is es­pe­cially im­por­tant if the nasal dis­charge con­tains pus or smells bad or there’s a change in the horse’s breath­ing pat­tern. It is much bet­ter to have your vet­eri­nar­ian come out for a mi­nor ill­ness than to wait and find out two days later that the horse is re­ally sick.”


One of the first things a vet­eri­nar­ian will do when ex­am­in­ing a horse with post-travel res­pi­ra­tory signs is to de­ter­mine whether the prob­lem is a less se­ri­ous up­per res­pi­ra­tory in­fec­tion or a more wor­ri­some in­flam­ma­tion of the lungs (pneu­mo­nia). “Op­por­tunis­tic bac­te­ria set up a bac­te­rial pneu­mo­nia, but it can be treated at an early stage and the horse has a very good prog­no­sis for re­cov­ery and re­turn to use,” says Wil­son. “Oth­er­wise it may progress into a num­ber of more se­ri­ous con­di­tions, in­clud­ing pleu­rop­neu­mo­nia.”

Sim­ply lis­ten­ing to the horse breathe may pro­vide some clues. “Of­ten you can hear some ab­nor­mal lung sounds with a stetho­scope,” says John­son. “[Your vet­eri­nar­ian] might not be able to hear any lung sounds at the bot­tom of the chest but hear them at the top of the chest and be­come sus­pi­cious that there might be fluid in the pleu­ral cav­ity.”

Your vet­eri­nar­ian may also rec­om­mend ul­tra­sound imag­ing, “which will usu­ally show any dis­ease within the pleu­ral cav­ity and if there is fluid ac­cu­mu­la­tion,” says John­son. “It also gives a re­ally good idea about what’s hap­pen­ing at the sur­face of the lungs and how far into the lungs the dis­ease ex­tends.”

Of­ten, in hospi­tal set­tings, x-rays will also be taken to look for any is­sues missed by ul­tra­sound. “If there is an ab­scess or in­fec­tion in the mid­dle of the horse’s lung but still some nor­mal lung on the pe­riph­ery, you could miss that le­sion with an ul­tra­sound,” John­son says. “The ul­tra­sound beam doesn’t pen­e­trate through nor­mal lung con­tain­ing air. Thus we of­ten take ra­dio­graphs of the horse’s

Fever is of­ten the ear­li­est sign of trou­ble, so check a horse’s tem­per­a­ture daily--twice a day, if pos­si­ble ---for sev­eral days af­ter trans­port.

chest to make sure there is not any deeper dis­ease that is go­ing un­de­tected by the ul­tra­sound.”

Blood tests may also be help­ful. “The vet­eri­nar­ian may want to do blood­work to look at the white blood cell count to see if there is ev­i­dence of in­fec­tion,” says Wil­son. “There are also other fac­tors we look at that may be in­dica­tive of in­flam­ma­tion. One is fib­rino­gen, which is in­cluded in the com­plete blood cell count. The other test that has gained in use in the last few years is to mea­sure con­cen­tra­tions of serum amy­loid A [SAA]. This is an acute phase pro­tein, which means it in­creases rapidly when there is acute in­flam­ma­tion in the body.”

Fi­nally, if a bac­te­rial in­fec­tion is sus­pected, the vet­eri­nar­ian may have some lab work done to iden­tify the spe­cific cul­prits. “We might do a tra­cheal wash to get a sam­ple of fluid from in­side the trachea,” says Wil­son. “This sam­ple can be cul­tured, so we’ll know which bac­te­ria are in­volved. Most of the time, it’s a mix. Anaer­o­bic bac­te­ria [which don’t need oxy­gen] may form ab­scesses and cause some of the lung tis­sue to die. This can be a more se­ri­ous type of in­fec­tion.”


Faced with a horse in the early stages of res­pi­ra­tory dis­ease, one of the first treat­ment de­ci­sions a vet­eri­nar­ian will make is whether an an­tibi­otic is needed. “Vi­ral in­fec­tions won’t re­spond to an an­tibi­otic. The horse may sim­ply need med­i­ca­tion to con­trol fever. If it’s not a high fever, the horse may not need any med­i­ca­tion at all,” says Buech­n­erMaxwell. “How­ever, viruses of­ten dam­age the lin­ing of the air­way. In some cases when a horse gets re­ally sick from a virus, we may give an­tibi­otics, more as a pre­ven­ta­tive mea­sure, to com­bat pos­si­ble sec­ondary bac­te­rial in­fec­tions.”

Of course, an­tibi­otics are also war­ranted when a horse’s signs point to­ward a bac­te­rial in­fec­tion at the out­set. “If your horse is cough­ing and there is an odor to the breath, with nasal dis­charge con­tain­ing mu­cus or pus, he is hav­ing trou­ble breath­ing or is in­tol­er­ant of nor­mal ex­er­cise, he needs treat­ment,” Buech­ner-Maxwell says.

Of­ten, a broad-spec­trum an­tibi­otic will be pre­scribed even be­fore the causal bac­terium has been iden­ti­fied. “Many peo­ple, es­pe­cially with a sick horse, don’t want to wait to get the re­sults of the cul­ture be­fore start­ing treat­ment, so we gen­er­ally start these horses on a broad-spec­trum an­tibi­otic pro­to­col,” John­son says. Then, when the re­sults of the cul­ture are in, the drugs can al­ways be changed.

“Once these horses are sta­ble enough to go home for con­tin­ued care, we’d know which oral an­tibi­otics are ap­pro­pri­ate for con­tin­ued treat­ment,” says John­son. “There are some peo­ple, how­ever, who would only do the tra­cheal wash and the cul­ture if the horse was not re­spond­ing to the ini­tial se­ries of an­tibi­otic. I think most peo­ple do the tra­cheal wash ini­tially, but there is not com­plete con­sen­sus on that.”

Other sup­port­ive care may in­clude the use of an­ti­in­flam­ma­tory drugs as well as other anal­gesics. “The horse may need fluid sup­port if he’s feel­ing poorly enough that he’s not drink­ing,” says Wil­son. “Bron­chodila­tors can some­times help, as well. Clen­buterol

Dur­ing an ex­am­i­na­tion, a vet­eri­nar­ian may use a stetho­scope to lis­ten for ab­nor­mal lung sounds as a horse breathes.

is a bron­chodila­tor that can im­prove clear­ance of the air­ways.”

The goal in the ear­lier stages of treat­ment is to curb the in­fec­tion be­fore it ex­tends into the pleu­ral cav­ity. “The ear­lier you start the an­tibi­otics, the more likely you will have a faster and suc­cess­ful res­o­lu­tion of dis­ease,” says John­son. “The longer the horse goes without ap­pro­pri­ate an­tibi­otic treat­ment, the more likely he will de­velop more se­vere dis­ease or com­pli­ca­tions with more dam­age.”


Given the prac­ti­cal, emo­tional and fi­nan­cial toll that ship­ping fever can take, “the best sce­nario is to try to pre­vent in­fec­tions from de­vel­op­ing, and mon­i­tor the horses closely af­ter ship­ping---for a few days to a week,” Wil­son says. Here are some mea­sures that can help you pro­tect your horse:

Avoid ty­ing your horse’s head high for pro­longed pe­ri­ods. “The big­gest fac­tor is that most horses while trav­el­ing are tied with their heads up,” says Wil­son. “It is im­por­tant for horses to be able to put their heads down, to clear de­bris and bac­te­ria out of the up­per res­pi­ra­tory tract. If pos­si­ble, leave horses in a box stall or trailer com­part­ment in­stead of tied, so they can move around and put their heads down.”

If you must tie a horse in the trailer, to pre­vent bick­er­ing with a neigh­bor, for ex­am­ple, give him as much slack as pos­si­ble to let him drop his head be­low the level of his withers. On longer trips, sched­ule rest stops at least ev­ery four hours, if you can, and un­hook the horse’s hal­ter so he can stretch his neck and lower his head.

Also, al­low a horse time to re­cover with his head down af­ter a trip---for ex­am­ple, don’t tie him to a high­line for the night af­ter spend­ing all day in a trailer. “[One study] showed that the num­ber of bac­te­ria in tra­cheal se­cre­tions was sig­nif­i­cantly in­creased in horses af­ter six hours with their heads el­e­vated,” says Buech­ner-Maxwell. “In horses who had their heads tied up for 24 hours, it re­quired eight to 12 hours be­fore the air­ways re­turned to nor­mal.”

Make your trailer “lung friendly.” Travel with vents and win­dows open; use screens if you’re wor­ried about de­bris blow­ing into the trailer, and blan­ket the horses if it’s too cold.

Good ven­ti­la­tion is al­ways bet­ter for a horse’s lungs, but you’ll also want that air to be clean. “If you are trans­port­ing horses with win­dows wide open and have hay right in their face in a hay net, you might want to do some­thing a lit­tle dif­fer­ent so the horse isn’t get­ting a lot of dust in his face,” says Buech­ner-Maxwell.

Wet­ting down hay be­fore plac­ing it in the trailer might re­move some dust and/or make it less likely to blow in your horse’s nos­trils. Also, use a low-dust bed­ding, if any is needed at all. Dried ma­nure can also be a source of air­borne bac­te­ria in­side a trailer.

Hose out the trailer thor­oughly af­ter each trip, and re­move fresh ma­nure at rest stops along the way. “Feed­ing pel­lets in­stead of hay and fre­quent re­moval of ma­nure and urine from the trailer have been shown to re­duce the in­sult to the horse’s lungs,” says Buech­ner-Maxwell.

Avoid un­nec­es­sary travel with an ill horse, or one who has only re­cently re­cov­ered from ill­ness. A horse who is sick or who has been ill within the pre­vi­ous week or two may still have a weak­ened im­mune re­sponse. And if he’s re­cov­er­ing from a vi­ral res­pi­ra­tory in­fec­tion, his air­ways may not have fully healed. “Those viruses dam­age the cilia that line the up­per res­pi­ra­tory tract,” says Wil­son.

The cilia, the fin­ger­like pro­jec­tions that line the air­ways and help cap­ture and re­move in­haled par­ti­cles, can

Avoid ty­ing your horse’s head high for pro­longed pe­ri­ods. If you must tie a horse in the trailer---to pre­vent bick­er­ing with a neigh­bor, for ex­am­ple--give him as much slack as pos­si­ble to let him drop his head be­low the level of his withers.

be dam­aged by a vi­ral in­fec­tion such as equine in­fluenza, and it takes two to three weeks for them to fully heal, even af­ter the horse has oth­er­wise re­cov­ered. Un­til then, a horse’s abil­ity to ex­pel in­haled pathogens and dusts will be com­pro­mised.

Vac­ci­nate as ap­pro­pri­ate. If you fre­quently take your horse to shows or other venues where he will en­counter many other horses, con­sider hav­ing him

vac­ci­nated against rhinop­neu­moni­tis, in­fluenza and pos­si­bly stran­gles. Lim­it­ing his risks of ex­po­sure to ill­nesses like these may pre­vent more se­ri­ous in­fec­tions from gain­ing a foothold.

“If you plan to show the horse through the sum­mer, talk with your vet­eri­nar­ian about the best vac­ci­na­tion pro­to­col for the area where you live,” says Buech­n­erMaxwell. “If you are go­ing to show all sum­mer it may be best to vac­ci­nate ahead

of the show sea­son and then give a booster if you are on the show cir­cuit for more than four or five months.”

By tak­ing steps to limit your horse’s risks of de­vel­op­ing ship­ping fever, and act­ing quickly when you no­tice the ear­li­est signs of ill­ness, you and your horse will likely be able to keep on rolling for many years to come.

pleu­ral spacepleur­a lung

SUP­PORT­IVE CARE: De­pend­ing on a horse’s sit­u­a­tion, he may re­ceive an­ti­in­flam­ma­tory drugs, bron­chodila­tors and/ or anal­gesics, along with an­tibi­otics. Ad­min­is­tra­tion of in­tra­venous flu­ids may also be ne­c­es­sary.

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