What we still don’t know about leptospirosis in dogs

Veterinarians know leptospirosis is on the rise, but many of the most basic questions about how dogs become infected are still unresolved. In this interview with dvm360, Jane Sykes, BVSc, DACVIM (SAIM), PhD, MPH, MBA, FNAP, a researcher and professor of medicine and epidemiology at the University of California, Davis, School of Veterinary Medicine, discusses the research gaps that matter most and what progress may be on the horizon.

Below is the transcript, lightly edited for clarity.

dvm360: What gaps in leptospirosis research still need to be addressed, and what developments do you anticipate in the next few years?

Sykes: We still don't really understand transmission cycles in dogs, and that's really the focus of our research right now—is really trying to understand what serovars are out there, and how they're circulating among different animal species and the environment and their risk to humans. And that’s a difficult thing to study, because really the only way to understand it is to do whole-genome sequencing on isolates from urine.

We were able to do that in the West Los Angeles outbreak, and we were able to show that at least in the post-peak period, the organisms were a little bit different from one another in several dogs. So it didn't suggest that there was, you know, dog-to-dog transmission occurring during that period, although there could have been during the peak. So we need more studies like that to kind of understand, you know, are rodents infected with the same strains that dogs are infected with? You know, what about other wildlife species—urban wildlife species—and their role in transmitting infections to dogs, and what's out there in the environment too? So it's a real One Health problem.

So we badly need that. We also badly need vaccines that are not serovar-specific. And I think once we have vaccines that are broader and not serovar-specific, then, you know, a lot of this stuff about understanding serovars will not be so important, because we're still trying to understand serovars so that we can design appropriate vaccines to protect against those serovars, because they're serovar-specific. But as soon as we have vaccines that are non-serovar-specific, it'll become less important to know what serovars are infecting dogs.

And really importantly, you cannot use the MAT test as a serovar test. It's a diagnostic test for leptospirosis, and serovars are added to improve the sensitivity of the test, not to help identify serovars—because you could easily keep adding on more and more serovars to the panel and see higher and higher titers to additional serovars. So it's not a good serovar test.