Veterinarians more aggressive in vaccinating aqainst Leptospirosis
Practices, military base note more cases

DVM Newsmagazine November 2004

ATLANTA—An increase of pets present-ing with Leptospirosis spurred Banfield, The Hospital to document the number of cases the hospitals are diagnosing.
Thirteen cases have been confirmed at Banfield hospitals alone in
a span of 60 days-, says Dr. Pam Hale, Southeastern medical director for Banfield.
"The cases have been very typical, presenting with lethargy or more severe cases that are already in renal failure," Hale says.
Two to three months after heavy rains, the bacteria are more prevalent, with the preliminary way to contact being through urine.
The disease primarily affects canines, but it can be transferred to people, typically those who deal with animals regularly.
Banfield's tracking of Leptospirosis cases will be done strictly by counting the number of cases seen by Banfield veterinari-
ans. Animals testing positive will be entered into the company's database that will collect the data from the company's hospitals around the country.
Hale suggests veterinarians recommend their clients vaccinate their pets against Leptospirosis despite some of the potential unfavorable side effects, which includes facial swelling, itching, muscle soreness and fever.
Hale suggests veterinarians vaccinate dogs in areas even if the region has not yielded a high number of cases.
"This isn't what I would call an epidemic, but an increased awareness to prevent the problem and test for it should be recognized," Hale says.
Other Leptospirosis cases
A recent outbreak of Leptospirosis among military canines and dog handlers at a Texas military base has
spurred an ongoing investigation on how the bacteria made its way to the closely tended to dogs.
It has been a long-standing veterinary policy for the Department of Defense to vaccinate all military working dogs (MWD) against the bacteria, according to Dr. Peggy Carter.
Two MWDs became ill with renal failure. Dog handlers also presented with flu-like symptoms during the same week.
A third ill dog was confirmed with Leptospira organisms via dark field microscopy.
Carter has posted updates regarding the military dog's status on ProMed mail. The updates can be checked by visiting www.promedmail.org.

States Leptospirosis is most predominate

•Arkansas •Florida •Georgia •Illinois •Indiana •Maryland •Minnesota •North Carolina

Environmental Risk Factors for Leptospirosis in Dogs

JAVMA 225(1 ):72-77, 2004. Ward MP, Guptill LF, Wu CC.
Purdue University School of Veterinary Medicine
West Lafayette, Indiana

Leptospires are unusual organisms—more than 200 serovars have been reported and at least one host species acts as a reservoir for each serovar. Historically, Leptospira interrogans serovars canicola and icterohemorrhagiae have been known to cause leptospirosis in dogs. However, more recent reports have identified L. interrogans serovar Bratislava, L. kirschneri serovar grippotyphosa, and L. interrogans serovar pomona as causative agents of leptospirosis in dogs. In addition, the prevalence of leptospirosis in dogs has been increasing over the past 20 years.
Using geographic information system (GIS) technology, researchers from the Purdue University School of Veterinary Medicine conducted a study to identify why-these changes are occurring. Specifically, the study was designed to identify the exact localities in Indiana where dogs are at increased risk of contracting leptospirosis. In addition, environmental factors were examined to identify any that may place dogs at increased risk of infection.
The medical records of 36 dogs examined at the Purdue University School of Veterinary Medicine and diagnosed with leptospirosis during a 6-year period were evaluated. The records of an additional 138 dogs seen at the hospital during the same time frame that were seronegative for leptospirosis were included as controls. Owner addresses were used to geocode locations of dogs using zip code, street, and street number. A buffer zone of 1,000 meters was included for each dog as a "home range" on the map that was generated. Data sources for environmental factors included the State Soil Geographic Database, areas classified as urban by the 1990 and 2000 National Censuses, National Wetlands Inventory, State Recreational Inventory, hog and cattle densities, county forest density, and similar sources. The risk of being an exposed case versus an unexposed case was determined.
The most striking result was the finding that the risk of a dog being diagnosed with leptospirosis was significantly associated with living in an area that had been classified asrural in 1990 but was considered urban in 2000. Using this information in a statistical model, the investigators were able to correctly estimate the status of infection with leptospirosis in more than 80% of the study dogs.
One theory for this result is that urbanization is often accompanied by reforestation in areas previously used for agriculture. This allows increased contact between dogs and wildlife that serve as key reservoirs for leptospirosis. In 19 of 30 dogs in which the infecting serovar was identified, L. kirschneri serovar grippotyphosa was found. The reservoirs for this serovar include raccoons, voles, skunks, and opossums—animals often found in forested, periurban areas. Analysis of other environmental variables did not significantly improve the investigators' accuracy. Therefore, the authors concluded that dogs in periurban areas are at increased risk of infection with leptospirosis and should therefore be protected by vaccination.—SEP

COMMENT: Leptospirosis, not an uncommon endemic disease in any particular geographic region, can be caused by infection with only one or several serovars (www. ivis.org/advances/Inf ect_Dis_Carmichael/mcdonough/ chapter_frm. asp?LA=l). Leptospires become adapted to primary reservoir hosts that are common wildlife species. These same Leptospira spp also occur in almost any other mammal as incidental or accidental hosts. Dogs are the primary reservoir host to L. interrogans serovar canicola, which is found in the incidental hosts rats, raccoons, hedgehogs, voles, and skunks, and to L. interrogans serovar Bratislava, which occurs in the incidental hosts hedgehogs and voles. Dogs can also become infected with several other serovars and can serve as accidental or incidental hosts.
Historically, the serovars associated with clinical disease in dogs included L. interrogans serovar canicola and L. icterohaemorrhagiae (primary reservoir host is rats; incidental hosts are mice, raccoons, opossum, hedgehogs, fox, woodchuck, skunks, and muskrats). Since 1996, both L. interrogans serovar grippotyphosa (primary reservoir host is voles; incidental hosts are mice, rats, raccoons, opossum, fox, squirrels, skunks, hedgehogs,
muskrats, and moles) and L.interrogans serovar pomona (primary reservoir hosts are cows and pigs; incidental hosts are deer, mice, raccoons, opossum, hedgehogs, foxes, woodchucks, and voles) have become more prevalent in the northeastern region of the United States. L. interrogans serovar bratislava (primary reservoir in pigs and horses) emerged in 2000 as an additional problem.
The reported prevalence and incidence of leptospirosis in dogs are probably underestimated because it is likely that much of the disease in dogs is undiagnosed, as many infections remain asymptomatic. In addition, many veterinarians have not included leptospirosis in the differential diagnosis of acute renal or liver disease, or in many instances, owners do not seek veterinary help when signs of the disease do occur.
It should be recognized that seroconversion does not always correlate with overt clinical disease in dogs. Leptospires do not multiply outside the host animal species, but they survive well in the environment under optimal conditions. For direct infection to occur, dogs must be exposed to leptospires from infectious urine via transpla-cental and venereal routes, bite wounds, or iiigestion of contaminated meat or water. The most common source of leptospirosis in dogs is contaminated water. Indirect transmission can also occur from ingestion of vegetation, soil, or food contaminated by infectious urine.—JDH