Leptospirosis in Dogs  

Definition: What is Leptospirosis in Dogs?

Leptospirosis is a disease in dogs caused by spiral-shaped bacteria. It is commonly referred to as Stuttgarter Dog Disease or Weil’s disease. The causative agent is the bacterium Leptospira (L.), which is found worldwide and can even cause severe infections in dog owners.

The most common species is Leptospira interrogans, although other species such as L. pomona or L. australis also exist. Leptospires thrive in warm, moist environments, which is why they are particularly prevalent in the Mediterranean area and other warm and humid climates. Consequently, infection rates increase during the summer and autumn months.

Causes of Leptospirosis: How Do Dogs Become Infected?

They are present in various domestic animals and are especially common in wild animals such as rodents, which are the primary hosts. They spread to the final host through direct and indirect contact, such as contaminated objects, food, or water.

Infectious urine is the main source of infection in most cases, but the bacteria can also be transmitted during mating or during pregnancy in the womb to the foetal puppies. Once leptospires enter the body, they quickly spread through the bloodstream to the entire body.

Whether and to what extent symptoms appear depends on the formation of protective proteins (antibodies): 

• Animals with antibodies: the pathogens are eliminated and the disease does not occur 
• Animals without antibodies: the bacteria multiply in various organs, leading to a disease outbreak 

Leptospirosis Symptoms in Dogs 

When leptospirosis breaks out in dogs, the liver and kidneys are particularly affected. However, reproductive organs, the nervous system, and other organs can also be affected. 

Depending on the severity of the disease and the activity of the immune system, there are three different types of progression with varying symptoms. These symptoms do not always fully develop, and in many cases, leptospirosis follows a milder course. 

Sudden (Peracute) Progression: 

• The bacteria multiply so rapidly that the affected animals die within a short time from organ damage 

Relatively Sudden (Subacute) Progression: 

• Poor general condition and fever spikes 
• Vomiting and dehydration 
• Increased tendency to bleed, e.g. nosebleeds, breathing difficulties due to lung bleeding (severe pulmonary haemorrhage syndrome, SPHS) 
• Yellow mucous membranes (jaundice) 
• Increased water and urine output (polyuria, polydipsia) and possibly acute kidney failure 
• Neurological deficits 

Slow (Chronic) Progression: 

• Kidney inflammations 
• Liver inflammations and increased restructuring of the liver (liver fibrosis) 

Leptospirosis Diagnosis in Dog

A detailed owner interview (anamnesis) is the basis of any diagnosis. A stay abroad and other important indications, such as a change in drinking behaviour, are important signs of leptospirosis in dogs. Through a general clinical examination, the vet can determine other important parameters such as general condition and body temperature.

If the vet suspects an infection with leptospires, a special examination is initiated. In a blood test, affected animals typically show an increased number of white blood cells (leukocytosis) and a lack of blood platelets (thrombocytopenia), which disrupts clotting and can lead to bleeding. 

The chemical analysis of the blood provides important clues about kidney and liver function. If the organs are already damaged, the animals show, among other things, elevated levels of nitrogenous toxins in the blood (azotaemia) and high liver values such as ALT (alanine aminotransferase) or GLDH (glutamate dehydrogenase).

Since the blood test is not definitive proof of leptospirosis, the vet can initiate a direct or indirect pathogen detection. A direct pathogen detection is carried out with a dark-field microscope using a urine sample, but this test method is relatively unreliable because pathogens cannot always be detected in the urine. 

Thus, a standard method is to perform an indirect serological test, the microscopic agglutination test (MAT). This test detects specific antibodies produced by immune cells when leptospires are present. However, if the animal was vaccinated before becoming ill, it is difficult to distinguish between vaccine titers and an infection.

Therefore, the test is conducted over several weeks, as only a significant increase in antibodies is conclusive. 

Treatment for Leptospirosis in Dogs

Treating leptospirosis in dogs involves various therapeutic measures: 

• Two-phase antibiotic administration 
• Symptomatic therapy, including: 
• Infusion therapy 
• Painkillers (analgesics) 
• Medications for nausea (antiemetics) 
• Gastroprotective tablets 
• Oxygen for breathing difficulties 
• Artificial feeding 
• Urinary catheter 

Continuous monitoring of the sick dog’s vital parameters is essential to intervene quickly in case of deterioration. Special attention should be paid to kidney activity, as there is a high risk of acute kidney failure. 

Prognosis of Leptospirosis in Dogs

The prognosis of leptospirosis in dogs strongly depends on the dog’s age, the form of disease progression, and the treatment administered. The peracute form is usually fatal, whereas a subacute infection can be successfully eliminated with correct treatment. Severe cases are more common in unvaccinated animals. 

Leptospirosis in Dogs: Prevention

Vaccination can be given from 8 weeks of age. Dogs receive basic immunisation through 2 injections 4 weeks apart. Booster vaccinations are then administered annually. Research is ongoing for new vaccines that will also cover other species. Therefore, it is advisable to protect dogs from leptospirosis with these new vaccinations. 

Additionally, other preventive measures can help prevent leptospirosis infection, including avoiding endemic areas and regularly cleaning and disinfecting food areas and the dog’s toilet.