leptospirosis

Question 1

what is the pathogenesis of leptspirosis?

Answer 1

• first leptospiremic phase - flu like symptoms
• then targets:
  ◦ The kidneys: Organisms persist and multiply in the tubular aspect of the renal tubular epithelial cells causing cytokine release, inflammatory cell recruitment, and acute nephritis
  ◦ The liver: centrilobular necrosis and subcellular damage, bile canaliculi, and duct occlusion, may cause icterus.
  ◦ Endothelium: tissue edema and disseminated intravascular coagulation may occur within the first few days of infection as a result an acute endothelial injury
• A **benign meningitis **can form if the bacteria enters the CNS and it is also possible for it to cause pulmonary disease

Question 2

how is leptosirosis spread?
what are the hosts?

Answer 2

zoonotic!
leptospirosis can be transmitted directly between hosts in close contact through urine, venereal routes, placental transfer, bites, or ingestion of infected tissues as the organism penetrates mucosa or broken skin.
Shedding by infected animals occurs, usually via urine.

The dog serves as the reservoir host only for the pathogenic L interrogans serovar canicola.
The reservoir hosts for the other serovars include common rodents, skunks, raccoons, farm animals, and deer, which can carry and excrete the bacteria in their urine for extended period.

Question 3

what are the clinical signs of leptospirosis?

Answer 3

Clinical signs of dogs with leptospirosis can vary from subclinical or minimal clinical disease or mild fever to severe kidney, liver, and pulmonary disease.

The disease presentation may be subacute, acute or peracute.
Clinical signs can be non-specific and multi-systemic and include vomiting, weakness, lethargy, fever, polyuria/polydipsia (PU/PD) and jaundice.
Dyspnoea may be present and, in such patients, leptospiral pulmonary haemorrhagic syndrome (LPHS) should be considered.

Question 4

how do you test for leptospirosis?

Answer 4

• PCR of organism from EDTA blood (up to 5 days post infection) and urine (from 7-10 days post infection)
  ◦ samples collected before antibiotic most helpful
• Antibody titres (Microscopic Agglutination Test - MAT)
  ◦ if high in unvaccinated dogs could be diagnostic
  ◦ need a rising titre in vaccinated dogs
  ◦ most convincing is with rising titre (4 fold increase in 2-4 weeks)
  ◦ low in chronic disease therefore not helpful for carrier state
  ◦ false negative (low) results if antibiotics have been given
• Dark field microscopy – difficult and low sensitivity and specificity
• Post mortem: FISH identification of leptospires in tissue samples
  ◦ too unstable to consider liver biopsy for diagnostics in most acute cases

Question 5

what treatment and support is given for leptospirosis?

Answer 5

Supportive therapy:
* IVFT;
* Potassium management: if hyperkalaemic consider Calcium gluconate, dextrose/insulin
* Anti-emetics
* Antioxidants (SAMe)
* Assisted nutrition

Specific therapy:
Early antibiotic treatment is strongly recommended
* Penicillin G, ampicillin or amoxycillin for 2 weeks
◦ Kills circulating organisms very effectively
◦ Does not remove the carrier state

• Then use Doxycycline for 2 weeks
  ◦ Elimination of carrier state
  ◦ May cause vomiting and not always tolerated in acute cases

Question 6

how can leptospirosis be prevented?

Answer 6

• More common in unvaccinated animals but can occur in fully vaccinated animals as well

Vaccination:
* Inactivated organisms
* Duration of immunity variable in different animals
◦ probably does need annual vaccination unlike other vaccines
* Serology to assess vaccination efficacy?
◦ correlation between antibody levels and protection is poor (This makes if hard to recommend antibody titre testing in place of vaccination)

Lifestyle:
* Reduce access to potential sources of exposure
* Avoid drinking from or wading/ swimming in fresh or stagnant water sources and marshland
* Control rodent sources; avoid hunting or access to wildlife