Bostons are predisposed to a variety of heart ailments, respiratory problems and heatstroke caused by partial upper airway obstruction and the pushed - in nose anatomy. (soonervet.net)
Brachycephalic means short - headed, and when shortened to some extremes like we witness today with Bulldogs, this respiratory problem also called congenital obstructive upper airway disease leads to a series of related problem. (breedingbusiness.com)
When breathed in by a susceptible dog, the viruses attach to the lining of upper airway passages where the warm, moist conditions allow them to reproduce and sicken the pet. (roverstayover.net)