My dog is always scabing on its skin. Little lice type insects are present on its hair . I use some insecticides but it can not effective will you tell me some other suggestion?
If you can see something on the fur of your dog it is very unlikely scabies,Scabies are a tiny mite living in the skin of animals(including humans).
Here is a link to help you identify the problem http://www.petsandparasites.org/dog-owners/scabies/ on the right hand side of this page are links to different parasites that are common on pets.
Your dog might have lice,You can identify this by holding your hand on one spot on the back of your dog for 20-30 seconds,if your dog have lice you will see it when you remove your hand(lice are attracted to the heat of your hand).
The reason i mention lice are because it is not on the list on the web page.
the lice that dogs can get are not the same as the ones humans get,And the lice that cats can get does not infect dogs or humans.
The common remedies against fleas are effective against lice too.
I hope this can point you in the right direction to solve your dogs problem.