Getting a sprite to rotate towards mouse?

Here is the code im trying..

// Get mouse input for rotation
		b2Vec2 mousePoint = b2Vec2(sf::Mouse::getPosition().x, sf::Mouse::getPosition().y);
		float deltaX = mousePoint.x - Body->GetPosition().x;
		float deltaY = mousePoint.y - Body->GetPosition().y;

		float desiredAngle = (-180/3.1415927) * atan2f( -deltaX, deltaY);

		// Set Rotation
		Body->SetTransform( Body->GetPosition(), desiredAngle );
		sprite.setRotation( Body->GetAngle());
		std::cout<<Body->GetAngle()<<std::endl;

It turns, but not correctly. It also never turns in a full circle, it just kind of swings. The values of Body->GetAngle() range from 180 to -180. I think what i want is the values to range from 0 to 360?

Anyways, how is this usually done?