Cases first came to light in northern Indian around the beginning of October.
Unofficial estimates put the number of cases at more than 5000, most affecting working animals.
The outbreak of the highly contagious disease has disrupted racing programmes in several regions, and some movement bans are in place.
Racing in Mumbai, Delhi, Pune and Kolkata is on hold, but is continuing in unaffected Bangalore.
Racing in some of the disrupted regions is expected to resume early next year.