EQUUS - - Eq Tack & Gear -

The role of stag­nant wa­ter as habi­tat for mosquito pop­u­la­tions is well known, as are West0 Nile en­cephali­tis, east­ern0 and west­ern0 equine en­cephalomye­li­tis and other dis­eases that mos­qui­toes can trans­mit to horses. But there’s an­other less com­mon but se­ri­ous threat as­so­ci­ated with still wa­ter: blue-green al­gae.

De­spite the name, blue-green al­gae are ac­tu­ally a type of bac­te­ria, known as cyanobac­te­ria, that cre­ate en­ergy via pho­to­syn­the­sis. They are nor­mally present in small num­bers in most nat­u­ral wa­ters. Un­der the right con­di­tions, how­ever—in warm, still wa­ters with high lev­els of phos­pho­rus or ni­tro­gen from fer­til­izer runoff—blue-green al­gae mul­ti­ply quickly and form thick, float­ing mats called “blooms” or “pond scum.”

Some species of cyanobac­te­ria pro­duce tox­ins that can make both peo­ple and horses ill. “There are sev­eral dif­fer­ent species of al­gae and they pro­duce dif­fer­ent tox­ins,” says Michelle Abra­ham Lin­ton, BSc, BVMS, DACVIM (LAIM), of the Uni­ver­sity of Penn­syl­va­nia. “One is a neu­ro­toxin that af­fects the cen­tral ner­vous sys­tem; the horse de­vel­ops neu­ro­log­i­cal signs. The other is a he­patic toxin that cre­ates liver dis­ease. We no­tice the more ap­par­ent neu­ro­log­i­cal prob­lems such as tremors, ex­cess sali­va­tion, ataxia0 or acute death. There isn’t much you can do for the horse once signs ap­pear.”

Horses may in­gest the toxin when they drink af­fected wa­ter. “Some peo­ple feel that this dis­ease is un­der­diag­nosed be­cause of the sever­ity–if you just find the horse dead, it may be hard to de­ter­mine the cause,” says Lin­ton. “The im­por­tant thing is to be able to iden­tify the al­gae and make sure you don’t have it in any of the wa­ter sources where your horse might drink, es­pe­cially in warm weather.”

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