If antibodies undetected can there be infection?

Editors Note: In a new series, DVM Newsmagazine asks experts within a variety of veterinary specialties to break commonly held medical, business or professional myths. This month, NCSU's expert, Dr. Edward Breitschwerdt, takes a swipe at diagnosing vector-borne infection.

MYTH: Failure to detect antibodies rules out active infection.

REALITY: Dr. Breitschwerdt: In any given patient, establishing the role of one or more viral, bacterial, rickettsial or protozoal organisms as the cause of illness is difficult even if resources are not limited, which is generally not the case in practice.

Serology is perhaps the greatest confounder in clinical practice. Detection of antibodies nearly always indicates prior exposure, but even high antibody titers may not be related to active infection. Failure to detect antibodies, even in the face of a chronic infection, does not rule out active infection.

Our current data would suggest that 40 percent of dogs infected with a Bartonella species do not have detectable antibodies in our laboratory. Historically, we have been very dependent upon the detection of antibodies, particularly for organisms that are difficult to isolate. Now, with the possibility of organism-specific DNA testing, we are finding that antibody testing has limitations that were not previously appreciated. — LINDA MARIE WETZEL