Introduction and epidemiology
What type of bacteria is Leptospira spp.?
spirochete
What are the most prominent manifestations of leptospirosis?
Aucte tubulointerstitial nephritis
Liver dysfunction
Kidney and hepatic manifestations usually occur together, but occasionally are recognized in isolation.
Leptospirosis should be considered a differential diagnosis in any dog evaluated for AKI. What is the reference standard test for diagnosis?
acute and convalescent serologic testing using MAT
MAT report lists the serovars tested and the serum titer at whihc 50% of the organisms agglutinate as observed using darkfield microscopy
What is the appropriate antimicrobial treatment for Leptospirosis?
IV penicillin derivative to suppress bacteremia, followed by PO doxycycline to avoid intrarenal persistence, has been the traditional strategy (2 weeks)
Bacterin
monovalent, bivalent, and quadrivalent
Immunity is serogroup-specific, although partial immunity to heterologous serogroups has been documented in some studies.
What is the most important reservoir host worldwide?
Rodents
Rattus norvegicus
A worldwide prevalence of 30% has been identified, with prevalence exceeding 80% in some regions.
How do Leptospira spp. injure the liver? What type of hepatopathy is seen on bloodwork?
Spirochetes disrupt hepatocyte intercellular junctions, causing leakage of bile into circulation.
Cholestatic hepatopathy
Elevated liver enzymes, hyperbilirubinemia, hypoalbuminemia
2-14 days
Titers are negative or low during the first week of illness because of insufficient time for the production of detectable antibodies.
List 5 items of supportive care that should be considered when formulating a treatment plan.
- Fluid therapy, careful due to risk of worsening pulmonary injury, vasculitis, and organ dysfunction, quantify urine production
- Nutrition: highly digestible, normal to high protein diet, with sufficient energy content to support GI recovery and minimize catabolism (consider pancreatitis, renal disease, and GI intolerance)
- Analgesia: myositis
- Oxygen therapy, mechanical ventilation
- Renal replacement therapy
- GI support
- Hepatic protectants and antioxidants
- Transfusion therapy, hemostatic disorders
How does Leptospirosis cause disease in humans?
Subclinical or influenza-like illness
Hepatic and kidney failure (Weil's disease) or LPHS
What role do cats play in the epidemiology of Leptospirosis?
There is serologic evidence of infection of domestic cats, but based on rare reports of clinical disease, cats are considered disease-resistant when compared to other animal species.
Cats may act as reservoir hosts.
What are the most common CBC and biochemical changes? Urinalysis? Coagulation panel?
thrombocytopenia, mild to moderate non-regenerative anemia
azotemia, elevated blood phosphorus, increased liver enzymes (ALP most significant), hyperbilirubinemia, mild to moderate hypoalbuminemia
increased CK
isosthenuria, glucosuria, proteinuria, mild pyuria, hematuria, bilirubinemia
Thrombocytopenia, hyper/hypofibrinogenemia, prolonged PT and aPTT, low antithrombin, increased D-dimers
How does the WITNESS Lepto Rapid test work?
detects IgM antibodies to whole cell extract from L. kirschneri serovar Grippotyphosa and L. interrogates serovar Bratislava
A positive IgM in an unvaccinated dog with consistent clinical signs is supportive of the disease diagnosis.
What are the indications for dialytic intervention?
Early RRT is recommended to prevent morbitity of AKI rather than as a delayed salvage for failed conventional management.
IRIS AKI grade 4, creatinine exceeds 5mg/dL
What is the risk of zoonotic transmission of pathogenic leptospires from sick dogs with leptospirosis to humans?
Appears to be low, especially when basic precautions are taken
What is the recommended diagnostic plan for a patient with an acute onset of febrile illness with no biochemical evidence of organ dysfunction during their first assessment?
Clinical reassessment and biochemical testing are recommended should the dog's condition not resolve with 24 hours.
If unvaccinated, high regional incidence, or history supports, nucleic amplification testing should be offered.
What are the radiographic changes seen with leptospiral pulmonary hemorrhage syndrome? When does the consensus statement recommend taking thoracic radiographs?
Bilateral caudal dorsal pulmonary infiltrates
All dogs suspected of having Leptospirosis, even in the absence of respiratory signs, because radiographic findings consistent with LPHS can aid in the diagnosis of leptospirosis and prompt judicious fluid therapy and close monitoring of respiratory signs
How are nucleic acid amplification tests used to make a diagnosis of Leptospirosis?
Detect Leptospira spp. DNA in blood or urine elary in the course of disease before a serologic response occurs
Specimens must be collected before antibiotics are administered.
A positive NAAT on blood in conjunction with appropriate clinical signs is diagnostic for Leptospirosis.
A negative urine or blood NAAT should not rule out disease.
How do you monitor response to treatment?
Serum biochemistry every 24 hours
CBC every 48 hours
Treatment is typically associated with a gradual return of serum urea and creatinine to reference ranges within 10-14 days. Serum bilirubin decreases more slowly than ALT and ALP. Platelet counts usually improve within 1 week of starting antibiotics.
Why is hospitalization in an isolation ward not required? How should urine be handled if an indwelling urinary catheter is not placed?
Isolation could negatively impact patient care
Walk patients in a restricted area without moisture, with good drainage, and exposure to ultraviolet light
How do Leptospira spp. infect their host?
Infections occur via mucous membranes and abraded skin that are exposed to pathogenic strains shed from the renal tubules of infected reservoir hosts.
Contaminate the soil and water, and can remain viable for weeks to months under optimal conditions.
More prevalent in areas with higher annual rainfall and warm climates.
Predation, bite wounds, venereal and placental transfer
Name five organs that can be involved in this multisystemic disease, excluding the kidneys and liver (there are 10 possible answers). What clinical signs can be seen?
1. Leptospiral pulmonary hemorrhage syndrome
2. Coagulopathy - thrombocytopenia, anemia, hypoalbuminemia, hyperfibrinogenemia
3. Vasculitis - peripheral edema, cavitary effusions
4. Pancreatitis - vomiting, diarrhea, abdominal pain
5. Ocular involvement - uveitis, conjunctivitis, retinal hemorrhages
6. Myocarditis - cardiac arrhythmias
7. Enteritis - intestinal intussception
8. Myositis - increased CK activity
9. Reproductive tract - abortion, infertility
10. Skin - calcinosis cutis
What are the confirmatory laboratory criteria? There are three.
Four-fold increase or higher in Leptospira agglutination titer at a single lab between acute and convalescent phase serum specimens.
Detection of pathogenic leptospirosis in blood using NAAT.
Isolation of Leptospira from a clinical specimen by a Leptospira reference laboratory.
What are negative prognostic factors in dogs?
Hyperbilirubinemia
Hypocoagulability
Usually, 7-10 days after infection
Dogs in the first few days of illness, before vet care is sought, may not represent a clinically relevant source of zoonotic infection
Consider prophylactic treatment with doxycycline because they may have been coincidentally exposed, ideally with monitoring of acute and convalescent phase antibody titers