I occasionally hike in the Sahyadri ranges in Maharashtra (India). During the rainy season there are a lot of crabs on the trail. In case the crab bites, what are the first aid steps that can be taken?
Crabs are scavengers, so their pincers are always to be considered evil sources of infection. You can use fluoride (if you act promptly); find the mouthwash with the highest fluoride content, and force it into a cut/wound with a syringe. Needle not required. After 5 minutes, rinse the wound with sterilized water and apply a proper bandage. If you have not brought mouthwash, you can use toothpaste, which can be easily diluted with sterilized water.
Be aware that fluoride is not intended for use inside wounds, so the wound must be rinsed with water.
Also, liquor with >=35-40% alcohol concentration will kill bacteria quite well.
India’s rural areas are notorious for their lack of proper and prompt healthcare, so you’d be wise to pack blisters with a wide-spectrum antibiotic as well. Similar to the fluoride, you can create a fast-acting antibacterial solution by extracting the powder from the capsules, mixing them with room-temperature sterilized water, and applying a thin paste to the cut/wound - then wrap a bandage around it. Simply eating a capsule will not bring a high enough concentration of antiobiotic to the wound.