Canine leptospirosis is
caused by an order of bacteria called spirochetes-slender, spirally undulating
bacteria. There are at least four species of the leptospira bacteria (or
serovars) that can infect dogs: canicola,
icterohemorrhagiae, grippotyphosa, and pomona.
Leptospira are found in wild and domestic animals. The bacteria are spread
in the urine, often making their way into water sources and remaining infective
in the soil for up to six months. Rats, pigs, raccoons, cattle, skunks, and
opossums appear to be the primary reservoirs. With housing spreading into the
suburbs, more wildlife are coming into contact with pet dogs. This may be the
cause of the upswing in leptospirosis cases. Spirochetes enter a dog’s system
through a break in the skin or when the
dog drinks contaminated water. Dogs who spend a lot of time in the water are at
increased risk, as are dogs who drink out of puddles and dogs who spend time in
yards that get a lot of runoff or stay wet after it rains.
Although the name suggests otherwise, ringworm is not caused by a worm at all-but a fungus. This highly contagious infection can lead to patchy areas of hair loss on a dog, and can spread to other animals-and to humans, too.
Most infections are mild and do not show clinical signs. Signs appear 4 to
12 days after exposure. Fever is present in the early stage. Other signs are
loss of appetite for several days, vomiting,
lethargy, depression, muscle pain, and sometimes diarrhea
or blood in the urine. Leptospirosis primarily affects the kidneys and/or the
In severe cases, the whites of the dog’s eyes turn yellow (jaundice). This
with destruction of liver cells. Coagulation problems can ensue, with
spontaneous bleeding from the mouth and blood in the stools. Following
recovery, untreated dogs can become carriers and shed bacteria in their urine
for up to a year.
The canicola and gripotyphosa serovars tend to cause kidney damage, and the
pomona and icterohemorrhagiae serovars most often affect the liver. Young dogs
tend to show liver damage with all of the serovars.
The diagnosis can be suspected based on the dog’s clinical signs. Tests of
kidney and liver function will be abnormal. Spirochetes can be detected in the
urine and blood by fluorescent antibody staining. Blood tests are available to
confirm the diagnosis.