Like us, dogs also get diseases. One of the most common ones are heartworms. This disease is caused by a parasitic worm and they can be spread by the bite of a mosquito. Heartworms may cause heart and lung damage, and other fatal consequences. Luckily there are medications for this type of disease for prevention and treatment,
Source: https://www.thevetshed.com.au/dogs/healthcare/worm-treatment/heartwormers/