Leptospirosis
Leptospirosis is an important worldwide problem in dogs but is rare in cats. It is caused by the Leptospira family of bacteria which has a number of pathogenic (disease causing) members, including Leptospira canicola (L. canicola) and Leptospira icterohaemorrhagiae (L. icterohaemorrhagiae) which are the most important, with L.grippotyphosa and L.pomona becoming more significant.
Leptospirosis can also affect humans.

The main clinical effects are seen in the urogenital system (urinary and reproductive systems).

Leptospira is primarily spread through contact with infected urine either directly or via urine comtaminated soil, bedding, food or water. Other means of infection include , sexual contact bite wounds. Leptospira can cross the placenta from the bitch to her pups causing abortion. Contact with aborted fetuses or after-birth can lead to infection. Leptospira have the ability to penetrate intact skin, enter cuts or gain entry through mucous membranes (the lining of the mouth, nose and urogenital tract).

Once in the body the leptospira enters the blood stream spreading throughout the body.
It then multiplies in various organs with the liver and kidney being particularly affected.
Many dogs will have subclinical ( not apparent) disease as their immune system is able to overcome the infection. Clinically affected dogs will show the first signs of illness approximately 7 days after infection. The dog will develop a fever and can show signs of anorexia, vomiting, diarrhea, tachypnoea (increased rate of breathing), dyspnoea (problems breathing), pale gums, jaundice (yellowing of the pale areas of the body), having an irregular fast pulse, sore muscles, polydipsia (increased drinking) and polyuria (increased urination). Death may result during this phase.
The heart, eye and nervous system are occasionally affected.

Two outcomes are possible after recovery from acute (active) disease, which will depend largely on the virulence (destructiveness) of the leptospira and the dog’s immune system capabilities. The leptospira may be completely eliminated or they may persist in the damaged kidney and liver, thereby causing a chronic (persistent) disease. This may be evident in the form of chronic renal (kidney), or chronic liver disease

Diagnosis is based on the clinical signs and specialised laboratory tests. In cases involving abortions, or animals that die, an autopsy is advised in order to confirm the diagnosis and thus instigate precautions to prevent other animals becoming sick.

Often intensive treatment with intravenous fluids and antibiotics is required for the acutely sick dogs. Acutely ill dogs have a poor prognosis. Care must be taken as affected animals will be excreting leptospira in their urine and humans can be infected. Iodine-based and bleach solutions should be used to clean the affected premises and gloves should be worn.

A few means of prevention of further spread include:
Vaccinate for L. canicola and L. icterohaemorrhagiae, the vaccine does not protect against other members of the Leptospira genus. Dogs at higher risk include show dogs, hunters and dogs with access to water. These animals should be vaccinated more frequently. Different vaccines have slightly different requirements for timing.
Maintain strict kennel hygiene with iodine-based and bleach solutions
Limit the dogs access to bodies of water and heavily irrigated pastures
Isolate any affected dogs in a kennel until treatment is complete
Control rodents on the premises