Bites from infected animals are potentially a risk, but unlike with the famous bite-transfer illnesses such as rabies, leptospirosis is not easily spread in saliva. During bites it is however possible for the animal’s gums to bleed and so for direct blood-to-blood transfer to take place.
Direct infection from rat bites has been recorded, although it is difficult to tell the exact route the bacteria took when dealing with rats – they are naturally incontinent and often their urine is found in and around their moth and whiskers – and there are several other infections possible from rat bites, some even more serious than leptospirosis.
If you have been bitten by any animal you think could be carrying leptospirosis, you should seek urgent medical assistance and be given a program of antibiotics. Other specific medication (such as tetanus boosters) will often be given as well. A blood test can be taken to confirm if there is any infection.