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Horse­keep­ers in trop­i­cal and sub­trop­i­cal re­gions are wise to be on the look­out for pythiosis, which is caused by a fun­gus­like or­gan­ism (Pythium in­sid­io­sum) com­monly found in swamps and stag­nant wa­ter.

P. in­sid­io­sum usu­ally en­ters open wounds or other breaks in the skin, but pythiosis can also oc­cur in or near the mouth if the horse grazes in­fected grass. Char­ac­ter­ized by hard, yel­low or white co­ral-like chunks of dead tis­sue (“kunkers”) that ap­pear in the af­fected wound, pythiosis also causes swelling around the in­fec­tion site, as well as the growth of masses of gran­u­lo­ma­tous tis­sue, re­sem­bling proud0 flesh.

Early di­ag­no­sis and treatment are vi­tal for re­cov­ery from pythiosis. Sur­gi­cal re­moval of in­fected tis­sue is the first step, which may be fol­lowed by im­munother­apy. Re­search shows that horses treated within 30 days of the oc­cur­rence of a pythiosis le­sion have a 90 per­cent or bet­ter cure rate. But the re­cov­ery rate drops to 50 per­cent when treatment is ini­ti­ated 90 days af­ter a le­sion de­vel­ops or later.

Pythiosis is en­demic to trop­i­cal and sub­trop­i­cal cli­mates. In the United States, most cases oc­cur in the Gulf states: Texas, Louisiana, Mis­sis­sippi, Alabama and Florida. How­ever, iso­lated cases have been di­ag­nosed as far north as Wis­con­sin and New York. The dis­ease can af­fect any mam­mal, in­clud­ing peo­ple. tools, hay carts, etc.,” says Gre­nager. “The other chal­leng­ing fac­tor is that horses can look healthy and still be shed­ding the pathogen in their ma­nure, es­pe­cially when they are stressed. This is prob­a­bly also true of the other an­i­mals that pe­ri­od­i­cally shed it---and then it gets into the wa­ter sup­ply.”

• S. en­ter­ica is di­vided into six sub­species and more than 2,600 serovars, some of which are nor­mally found in warm-blooded an­i­mals and some in cold-blooded an­i­mals. But all are zoonotic---mean­ing that they can cause dis­ease in peo­ple as well as an­i­mals. In horses, the two most com­mon forms that cause dis­eases are S. en­ter­ica serovar Typhimuriu­m and S. en­ter­ica serovar Ag­ona.

“There are thou­sands of kinds of sal­monella and dif­fer­ent kinds in­fect dif­fer­ent species of an­i­mals,” Gre­nager says. “Al­most any an­i­mal can get sal­monella, and it can be a se­ri­ous dis­ease in horses---foals and adults.” Sal­monella is com­mon around large live­stock op­er­a­tions, and the bac­te­ria can sur­vive in wet en­vi­ron­ments for months. Many forms of sal­monella are be­com­ing re­sis­tant to an­tibi­otics.

• Once in­gested, sal­monella bac­te­ria pen­e­trate the cells in the wall of the in­tes­tine and mul­ti­ply, caus­ing dam­age that leads to di­ar­rhea. In some cases, the bac­te­ria may get into the blood­stream (sep­ticemia), and in­fec­tions may de­velop in other parts of the body. “Foals can be­come bac­teremic or sep­ticemic with in­fec­tion through­out the body and then lo­cal­iz­ing in joints and other or­gans, which can be dev­as­tat­ing,” Gre­nager says.

Salmonello­sis gen­er­ally takes three forms in adult horses:

• A sub­clin­i­cal car­rier shows no signs of ill­ness but may shed the bac­te­ria in his ma­nure, which can then

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