Coccidioidomycosis (Valley Fever) is a systemic fungal infection endemic to the desert southwestern United States. Dogs are affected, with an estimated $60 million per year in diagnostic and treatment costs. Valley Fever has a variable clinical picture, ranging from subclinical infections to mild disease to severe, uncontrolled disease. Development of a vaccine to prevent, or reduce, illness in dogs is currently underway. T-cells are a type of immune system cell called lymphocytes. It has been demonstrated that a robust T-cell mediated immune response is needed to control the infection in mice and humans. Exploratory work suggests this is also true in dogs. The investigators plan to develop an assay of canine T-cells, from dogs with variable clinical responses to naturally-occurring infections, that will allow them to correlate T-cell responses with the severity of clinical disease. This information will allow better prediction of the clinical course of disease in dogs, resulting in improved treatment recommendations. This assay will also assess the protective response to the vaccine by mimicking the T-cell mediated response seen in dogs with coccidioidomycosis and will also be applicable to future studies of immune responses to other canine infectious diseases.