Testing for vector-borne pathogens in dogs: The best use of diagnostic panels

Serologic and PCR panels can help identify infection with vector-borne disease agents. So how do you choose which panel to use?
Jul 01, 2013

Vector-borne disease is an important cause of morbidity and mortality in dogs. Clinical findings include those commonly associated with idiopathic immune-mediated disease. Like vector-borne disease, the incidence of idiopathic immune-mediated disease can be seasonal.1,2 It has been hypothesized that many patients with immune-mediated disease actually have undiagnosed underlying infections with vector-borne and other infectious agents.

In addition to ruling out infection in patients with immune-mediated disease, vector-borne disease screening is also sometimes performed in healthy animals to detect subclinical infections and to screen blood donors and animals living with or interacting with immunocompromised people. Inappropriately declaring that infection has been ruled out because of a "negative tick panel" may adversely affect the health of dogs and people.

"Tick panels" and "vector-borne disease panels" give clinicians the ability to test blood for multiple agents and the presence of coinfection by using serology, polymerase chain reaction (PCR) assays, or both. Although these panels can be comprehensive, clinicians should remember that both PCR and serologic test results may be negative in the presence of infection, even if the assays are exquisitely sensitive.

It has been shown that using a combination of serology and PCR can substantially increase recognition of the presence of vector-borne disease.3,4 Familiarity with the epidemiology and pathophysiology of each organism helps determine which agents should be included and which type of testing—PCR or serology, or both—should be used.

This article reviews the concepts that help clinicians decide which organisms to include in screening, which type of test may have the highest sensitivity and specificity for a patient, and whether further testing for a particular organism is warranted in a particular case context. The form Vector-borne disease testing: Helpful questions to ask yourself summarizes the questions clinicians can ask to facilitate the testing process.