I've also seen similar streaks on my basil's leaves but not as pronounced.
Leaf miner infestation. Leaf miners differ round the world, as does any possible treatment available, though most treatments are relatively ineffective because the miner is within the leaf. You may need to use a pesticide available where you are, though neem oil might offer some solution, not sure. Bear in mind that anything you do use should be appropriate for food plants. Otherwise, please see answer to your other question for further comment...
I once had this with other vegetables, such as beet. At first I used to cut the whole leaf. At some time I realized that when observed at the right time, you can spot the larva.
Always search for the "end" of the tunnel as it eats its way through. When spotted early, you can hold the leaf against the light. Where the miner is, you may see a darker yellowish mass that forms a bulge. You can then pull the bug with tweezers.
In my country I would see them in winter to early spring, and it is planted here as winter vegetable. You may see them at different times, though.