By Deeksha Bharti*, Akshay Kumar**, Abhishek Bhardwaj***
Leptospirosis, a spirochaetal zoonosis, has emanated as a serious global health problem concerned with veterinary and public health expanse. It is a global infection caused by pathogenic Leptospira spp. Leptospirosis is a paramount zoonosis, with infection acquired predominantly from wild and domestic animals. It is also a significant cause of mortality, morbidity,and economic loss in production and companion animals.The pathogenic leptospires are divided into more than 250 different serovars and the most common serovars affecting dogs compriseCanicola, Icterohaemorrhagiae, Pomona, Grippotyphosa, Bratislava, and Australis.Spirochetes are spiral, or corkscrew-shaped bacteria thatinvadethe system by burrowing into the skin. It is a systemic disease, characterized by fever, renal as well as hepatic insufficiency, pulmonary manifestations, and reproductive failure.
Leptospires enter via mucosal membranes or damaged skin when comes in proximity with Leptospira-infected urine or substrates contaminated with infected urine (e.g., water or soil) from a reservoir host. The most common reservoir hosts are wild animals such as rodents.Hematogenously, the organism spreads throughout the body during a febrile, bacteremic phase, which may last up to several days. The organisms propagate in various tissues like liver, kidneys, central nervous system, eyes, and reproductive system. When numbers of leptospires in various tissues reach a critical level, characteristic signs such as pulmonary hemorrhage appear, jaundice due to liver damage, and nephritis due to kidney damage occurs.
Clinical Signs And Symptoms
The clinical findings for dogs with leptospirosis can diversify markedly, depending on severity of illness, causative serovar, and the immune status of the affected dog.Acute kidney injury has been the most common clinical finding for canine leptospirosis. Acute leptospirosis is characterized by hepatic and renal failure. Dogs affected by leptospirosis can show other clinical signs and symptoms that include the following –
- Lethargy, anorexia, weakness
- Sore muscles, reluctance to move, stiffness in muscles, legs, stiff gait
- Polydipsia and polyuria
- Oliguria or anuria
- Increased thirst and urination, may be indicative of chronic renal (kidney) failure, progressing towards inability to urinate
- Rapid dehydration
- Vomiting, possibly with blood
- Diarrhea – with or without blood in stool (melena,hematochezia)
- Bloody vaginal discharge
- Yellow skin and/or whites of eyes – anemic symptoms
- Spontaneous cough
- Difficult or fast breathing, irregular pulse
- Swelling of the mucous membrane
- Mild swelling of the lymph nodes
- Reproductive failure
Diagnosis Of Canine Leptospirosis
1. On the basis of clinicopathological abnormalities
- The most common abnormal biochemical abnormality is azotemia.
- Elevated liver enzymes like alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and bilirubin.
- Electrolyte abnormalities like hyponatremia, hypokalemia, hypochloremia, and/or hyperphosphatemia.
- In dogs with oligoanuria, serum potassium may be paradoxically normal or low.
- In dogs with myositis,creatine kinase levels can be elevated.
2. Serologic Testing – Microscopic Agglutination Test (MAT).
These outer membrane antigens are responsible for the induction of agglutinating antibodies in infected animals andon the basis of microagglutination test (MAT) quantitative antibody titre can be evaluated.
3. CBC changes may include:
- Mild to moderate thrombocytopenia
- Prolonged prothrombin time (PT) or prolonged activated partial thromboplastin time (aPTT).
- Mild anemia
4. Urinalysis affirms the following:
- Hyposthenuria, isosthenuria, or hypersthenuria, depending on the degree of renal involvement
5. Ultrasonographic changes include:
- Increased cortical echogenicity
- Perinephric effusion
- Hyperechoic renal medullary band, hepatomegaly, hypoechoic liver
6. Molecular Testing like PCR
Treatment Of Leptospirosis In Dogs
- Antibiotic Therapy –doxycycline @ 5 mg/kg/day PO for 2 wk. For dogs that cannot tolerate doxycycline, initial therapy with penicillin is appropriate, but this should be followed by a 2-wk course of doxycycline to eliminate the renal carrier phase of infection.
- Supportive measures may include:
- Intravenous crystalloids in case of electrolyte imbalance
- GI protectants
- Hepatic support medications
- Dogs that recover from leptospirosis may have permanent renal insufficiency that requires life-long therapy for chronic renal failure like dietary modifications, phosphate binding.
- Hemodialysis in severe cases. It appeared to improve the prognosis for dogs with severe azotemia.
Prevention And Control
- Strict kennel sanitation, rodent control, and strict isolation of infected animals should be followed to decrease the exposure and spread of leptospirosis in endemic areas.
- Disinfectants, including bleach, povidone–iodine, and chlorhexidine, are usually very effective in controlling leptospirosis because of its labile nature.
- Proper vaccination of dogs – Bivalent bacterins containing the serovars canicola and icterohaemorrhagiae are available. In India, vaccines like Nobivac Lepto, VANGUARD etc. are present.
*Division of Veterinary Medicine,GBPUA&T, Pantnagar
**Division of Veterinary Surgery and Radiology, IVRI
***Division of Veterinary Gynaecology and Obstetrics, GADVASU