It's best to get your manure tested first. That way if you do have an issue you can treat it before using it. I wouldn't put horse manure in the garden directly. You can buy a horse manure spreader to spread it on the lawn, but if you're trying to grow food or flowers it'll need to go into the compost pile. I would avoid putting anything organic into a compost pile or worm bin as they will contain pathogens and disease causing organisms. It's best to get your manure tested first. That way if you do have an issue you can treat it before using it.