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Leptospirosis Infection can be with one of two main forms of the disease, the organisms involved being Leptospira canicola, and Leptospira icterohaemorrhagiae these will be dealt with as separate disease syndromes. Leptospira canicola infection Mostly dogs under 3 years of age affected, it is transmitted through contact with urine from infected animals, the organism can penetrate through breaks in the skin or mucous membranes. After infection, if immunity is insufficient, it takes approximately 4-7 days for disease to develop. During this time the bacteria multiply in the blood and then invade organs such as the liver and kidney. After this period the immune response starts to eliminate the infection, but it can persist in certain sites within the kidney where it is inaccessible to the immune system. persistence in these sites can last months, or even years, with the bacteria being shed through the urine. The infection within the kidney causes a swelling and breakdown of the kidney tissue, the immune response creates an influx of white blood cells. The swelling and cell influx cause a rise in kidney pressure which results in a failing of the blood filtration, this leads to a state of uraemia and failure of urine production. The damaged kidney tissue is replaced by fibrous tissue during the healing process. The consequences of this depend on the extent of the damage, small areas of damage will allow complete recovery with only minor scarring on the kidney, in severe cases the blood pressure rises to try and maintain blood filtration, and if this persists it can itself damage the fragile kidney blood vessels leading, over a period of months to years, to terminal renal failure. The initial condition is called 'acute interstitial nephritis', the late kidney failure is the result of 'chronic interstitial nephritis'. There are 3 stages of clinical disease, initially there is a transient fever, inappetance, and general lethargy lasting 3-5 days. The second stage develops as a result kidney inflammation. Mild cases may pass unnoticed, severe cases become dull, thirsty, anorexic, vomit, and produce either excessive or restricted amounts of urine. There may be some abdominal pain. As uraemia develops mouth ulceration and bad breath (halitosis) can result. The worst cases are fatal within a few days of these developments. The third stage is the development of terminal renal failure at a later stage. Many case will appear to recover after the second stage only to deteriorate later. Diagnosis can be confirmed by demonstrating Leptospira in the urine. Blood tests for urea, creatinine, and phosphate will indicate kidney damage and tests for antibodies to Leptospira show a rise at 7 to 10 days post infection. Leptospira icterohaemorrhagiae infection This is a disease that is relatively uncommon in dogs, and occurs mainly in those exposed to infected rats. The damage that occurs in the initial infection tends to be more severe and is more frequently fatal. The liver is the organ which sustains the most damage in the initial phase which tends to result in jaundice. Spontaneous haemorrhage may be present in several organs and in subcutaneous sites. Presents with fever, lethargy, anorexia, and occasionally sudden death. Later weight loss, vomiting and dehydration. Jaundice and haemorrhage can be seen on the mucous membranes, the abdomen is painful. Acute kidney failure can occur causing uraemia and oliguria. Blood tests will show a mild anaemia and raised levels of liver enzymes, antibody tests can be used to confirm infection. Treatment and control are the the same for both conditions. The treatment of choice for leptospirosis is a combination of penicillin and streptomycin or oxytetracycline, continuing the course for around 10 days. Fluids to reverse dehydration and diuretics to induce urine production. In chronic renal failure low protein diets to reduce urea levels, unrestricted access to water and vitamin B supplementation are useful. In cases of liver disease anabolic steroids may be used during recovery. Vaccination confers effective immunity when 2 doses are given with a 2-4 week interval. These are organisms capable of causing disease in man, spread mainly by urine contamination. Clinically healthy animals can shed these organisms in their urine. Leptospira icterohaemorrhagiae is responsible for Weil's disease in man. Good hygiene is essential to minimize the health risk. |
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