Active: Health providers prepare, detect and refer cases.

Cases are prepared, detected and referred by health providers.

PaulM

Here is a lesson on passive sentence.

Active form of Imperative sentence:Teach him to learn
Kindly reply me the correct passive form in the earliest.

Passive imperatives are quite rare, except in examples like:

Be warned.
Don't be intimidated.
Get checked out by your own doctor.

But if we passivize your example, look what we get something like:

He is taught to learn. or Let him be taught to learn

They're grammatical, but not natural.

Why do you want to passivize that particular sentence?

PaulM

I am reading grammar books these days and whenever i am unable to get a proper answer or i feel that there is some mistake in the answer i try to confirm it from different websites and this time accidently i found the website, grammar-monster.com