In the UK, wagering integrity is certainly something that is watched and worked on. If I were planning a betting coup, I would not be wanting to try it across the pond.
..... Information arrives from all sectors of racing, from officers in the field, from courses, from weighing rooms, stables, punters, the public, and from a network of informants. "We run informants in the same way the police run informants, right down to safety and protection where appropriate," Beeby says.
...... Chignell signals an alert "when we know we've got a situation that doesn't look good". In such cases, the stewards routinely interview the connections of whichever horse has prompted the alert. When the unit was at a fledgling stage in 2004, there were around three alerts per week. Now it is around one every three weeks. Slowly and surely, racing is becoming less and less corruptible.
More at link