tiny worm
... that over 2,000 years ago two Chinese armies traveled 10,000 km to find "Heavenly Horses", apparently infected with a tiny worm causing them to "sweat blood" from sores"?
... that over 2,000 years ago two Chinese armies traveled <span about="#mwt26" class="nowrap" data-mw='{"parts":[{"template":{"target":{"wt":"Nowrap","href":"./Template:Nowrap"},"params":{"1":{"wt":"10,000 km"}},"i":0}}]}' id="mwBDo" typeof="mw:Transclusion">10,000 km</span> to find <a href="./Ferghana_horse" id="mwBDs" rel="mw:WikiLink" title="Ferghana horse">"Heavenly Horses"</a>, apparently infected with a <b id="mwBDw"><a href="./Parafilaria_multipapillosa" id="mwBD0" rel="mw:WikiLink" title="Parafilaria multipapillosa">tiny worm</a></b> causing them to "sweat blood" from sores"?