Gastroenteritis is the inflammation of the stomach, small and large intestines. The severity of the infection seen in the extent of mucosal irritation, invasion or even ulceration, causes very acute symptoms like severe and sudden vomiting and diarrhea.
The definition of inbred is someone who is born from people who are closely related, or is something that exists in a person or animal from birth. When two cousins get married and have a child, this is an example of a time when the child isinbred.
There is a well studied, although only partially understood phenomenon called inbreeding depression. Inbreeding depression is thought to be caused primarily by the collection of a multitude of deleterious mutations, few in themselves fatal, but all diminishing fitness. Normally, in an outbreeding population these alleles would be selected against, hidden, or corrected by the presence of good alleles (versions of genes) in the population.