Parvo in puppies, caused by the highly contagious parvovirus, is a severe and potentially life-threatening illness. It primarily affects the gastrointestinal tract, leading to symptoms such as vomiting, bloody diarrhea, lethargy, and loss of appetite. The virus spreads through contact with infected feces, contaminated surfaces, or unvaccinated dogs. Immediate veterinary care is critical, as dehydration and secondary infections can be fatal.