Parvo is shed in the feces so the fecal-oral route of transmission is most common.
However, it is also likely that the saliva and vomitus contain viral particles. In any case, CPV replicates in rapidly dividing cells, like those of the lymph nodes, spleen, bone marrow and intestines. In the intestines, the virus kills the germinal epithelium of the intestinal crypts, leading to epithelial loss, shortening of intestinal villi, vomiting and diarrhea. In lymph tissue, there is necrosis and destruction of myeloproliferative cells, leading to lymphopenia or in severe cases, panleukopenia. Other differentials should include Salmonellosis, Campylobacteriosis, E. coli infection, coronavirus infection, canine distemper or other enteric viruses.