One of my 9 dogs has this.

Is it infectious?

Any idea the total cost of the full treatment?

Thanks.

Dogs should be on the monthly medication to prevent it. If they are not, they need to be tested by the vet before they can start the medication. It is quite likely others have it, as it is spread by the bite of infected mosquitoes.

I am not sure if there is an effective cure once infected.

I am thinking expensive like many things relating to animal care. Seems only the richer Thai bother treating their animals so gives 'some' vets another reason to charge as they please. The treatment is quite extensive, injections to kill the adult worms and then antibiotics in the hope the dog doesn't have complications with the death of the worms. Depending how bad it is, surgery and other medications. Once at that point, I would most likely opt to put the dog down if in Thailand (depending how good the vets are where you live). 

Get the other dogs on the preventative. It is very effective, however, like all things it fails sometimes. 

Most important thing to do is test all the dogs. Even if negative, test in another 6 months if this dog has been found positive. 

Going to have to severely restrict exercise for this dog. As in, leave him in a room and just take him out to go toilet/short walk. Or if an outside dog, cage him (in decent size cage), so he cannot break into a run. 

If can get on top of controlling the amount of energy the dog exerts then treatment has a higher chance of being successful. Test again 6 months later to check if it was successful.

If no clinical symptoms yet (i.e. cough or exercise intolerance) then high chance of successful treatment. If symptoms, then lower chance and even if treated the damage to the organs is already done so the dog will live a lower quality of life.