PEER REVIEWED
HEARTWORM HOTLINE
DOXYCYCLINE in the Management of HEARTWORM DISEASE
Clarke Atkins, DVM, Diplomate ACVIM (Internal Medicine & Cardiology)
The Heartworm Hotline column is cosponsored by Today's Veterinary Practice and The American Heartworm Society (heartwormsociety.org). Each article presents a question or questions on a particular area related to heartworm infection, prevention, diagnostics, and/or treatment.
Y ou asked…
What role does doxycycline play in the manage- ment of heartworm disease? The exact role of doxycycline in the management of heartworm disease (HWD) is not well established.
However, virtually all experts in the field would agree that doxycycline has a role in therapy and most U.S. veterinarians incorporate it into their management of HWD (Figure 1).
Several important questions regarding doxycy-
cline remain unanswered, including: UÊ7h>ÌÊ iÃÊ ÌhiÊ o«ÌimÕmÊ VonVomiÌ>nÌÊ ÌhiÀ>«ÞÊ (ie, most data to date have been generated using concomitant administration of iver- mectin)?
UÊ7h>ÌÊiÃÊÌhiÊiÝ>VÌÊ`oÃ>}i]ÊÌimi-«oinÌÊvoÀÊini- tiation, and duration of therapy?
UÊ7h>ÌÊ>ÀiÊÌhiÊÀiÃkÊ>n`ÊVoÃÌÊÌoÊLiniviÌÊÀ>ÌioÃ¶Ê UÊ nÊÜhiVhÊëiViviVÊ`iÃi>ÃiÊÃÌ>}iÃ®Ê iÃÊ`oÝÞVÞ- cline useful?
Doxycycline versus Wolbachia The benefits of doxycycline result from its ability to remove or reduce the burden of Wolbachia, a rickettsial organism that exists in a symbi- otic relationship with heartworms (and other filarids), occupying the reproductive tract and lateral chords of the host parasite (Figure 2).
Figure 1. Graphic representation of doxycycline use by vet- erinarians attending the American Heartworm Society ses- sions at the 2012 NAVC Conference; it is apparent that 84% of veterinarians surveyed use doxycycline on occasion (1/3 or more) in the management of HWD.
Figure 2. An adult female heartworm is shown with Wolbachia antigen evident as stained material (arrow); the endosymbiont
inhabits the lateral chord and the uterus. Courtesy Dr. Laura Kramer
July/August 2012 Today's Veterinary Practice 41