EQUUS - - Medical Front -

Two years af­ter a ge­netic test for warm­blood frag­ile foal syn­drome (WFFS) was in­tro­duced, re­searchers have used it to doc­u­ment a pre­vi­ously un­di­ag­nosed case of the con­di­tion.

WFFS, sim­i­lar to hered­i­tary equine re­gional der­mal as­the­nia (HERDA), is char­ac­ter­ized by se­vere de­fects of the skin and other col­la­gen­con­tain­ing tis­sues. “Both [con­di­tions] are in­her­ited dis­eases re­sult­ing in off­spring with ab­nor­mally frag­ile skin,” says Chloé Mon­thoux, DVM, of the Uni­ver­sity of Zurich. In mild cases of HERDA, which may go un­di­ag­nosed for sev­eral years, the horse’s skin tears un­der pres­sure---from tack, for ex­am­ple---or is slow to heal. In WFFS, how­ever, se­verely af­fected foals may be born with ex­ten­sive skin le­sions and de­fects in ten­dons, lig­a­ments, blood ves­sels and other struc­tures.

In the WFFS case doc­u­mented by the Swiss re­searchers, a mare had been ad­mit­ted to the uni­ver­sity clinic be­cause of a pro­longed de­liv­ery. When the foal fi­nally ar­rived, she had ex­ten­sive skin le­sions and an 11-inch­long open­ing in her ab­domen through which her in­testines were pro­trud­ing. Be­cause of the poor prog­no­sis, the filly was eu­tha­na­tized, and the clin­i­cians col­lected tis­sue and blood sam­ples for testing from her and her dam.

The re­searchers ran a ge­netic test for HERDA on the sam­ples but it came up neg­a­tive. A year later, how­ever, the test for WFFS be­came avail­able, so the dam was retested as were re­tained tis­sue sam­ples from the foal. The re­sults showed that the dam was het­erozy­gous, mean­ing she car­ried one copy of the mu­tated gene re­spon­si­ble for WFFS, while the foal was ho­mozy­gous, mean­ing she car­ried two copies of the de­fec­tive gene---one in­her­ited from each par­ent.

“To our knowl­edge, this is the first de­tailed case de­scrip­tion of a ho­mozy­gous WFFS-pos­i­tive foal pub­licly avail­able. Milder cases may [have been] sus­pected as well as non-ob­served cases


BMC Ve­teri­nary Re­search, that ended in abor­tion,” says Mon­thoux, who adds that she hopes pub­lic­ity of this case will in­crease dis­ease aware­ness and testing prac­tices among breed­ers.

To de­velop WFFS, a foal must in­herit two copies of the mu­tated gene. This means that testing breed­ing stock for the mu­ta­tion can com­pletely elim­i­nate the risk of hav­ing an af­fected foal. “It is im­por­tant to no­tice that car­ri­ers (un­af­fected horses who have only one copy of the gene) do not nec­es­sar­ily need to be ex­cluded from breed­ing,” says Mon­thoux. “To avoid af­fected off­spring it is enough to en­sure that car­ri­ers are not bred to car­ri­ers.” She adds that all warm­blood horses are can­di­dates for screen­ing, as are any re­lated breeds “with a his­tory of abor­tion, still­birth, skin le­sions or mal­for­ma­tions of the skin in neonates.”

For in­for­ma­tion on testing a horse for WFFS, go to www. an­i­mal­ge­net­

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