PATHOLOGY

Detailed explanation-1: -Then the L2 larvae migrate to the mosquito’s salivary glands, where they molt to the infective L3 stage. This molting process takes 10 to 20 days, but it is vital to a heartworm’s life cycle. After the microfilariae have reached the L3 stage, they can infect a new host animal via a mosquito bite.

Detailed explanation-2: -Stage 2: Stage two of heartworms in dogs is accompanied by moderate symptoms including intolerance for exercise and a more lingering cough. The heartworms have been present long enough in the body for antibody production and probable microfilariae production.