Leptospirosis Flashcards
What is the importance of Leptospirosis?
Common in dogs
Rare in cats
Both can be carriers and shed in urine
In humans - flu like symptoms, nothing, mild, or Weil’s disease
What is leptospirosis?
Gram -ve spriochete
250 serovars
Each serovar adapted to a different host
How is it transmitted?
On fomites/ soil/ water or through bite
placental/ venereal
How do reservoir hosts act?
Low levels of clinical disease
Shed disease from the renal tubules for a long time
What are the risk factors for leptospirosis?
3m after high rainfall Exposure to wildlife and their u+ Living close to outdoor water sources Outdoor hunting (cats) Presence of infected resevoir hosts
Outline the use of vaccines
Needs a higher dose of antigen to prevent renal carrier state and prevent u+ shedding compared to preventing clincal disease
L2 - icerohaemorrhagiae and canicola - only 34% of main infections
L4 - covers against 84%
3 weeks until the onset of immunity
Lasts 12 months
First vax 6-9 weeks
2nd 10-13
Annual re-vax, ideally a few months before the peak season
Outline the pathophysiology of infection
Penetrates intact mucosae/ abraided skin
haematogenous spread
Exact mechanism causing tissue damage is unknown
Immunotoxic mechanism
7d incubation
Initial immune evasion until adaptive immune response occurs
Possible persistence in immune priviledged sites - e.g. eye and renal tubule
What are the main organ manifestations
99.7% renal
36% hepatic with hyperbilirubinaemia
70% pulmonary
18% haemorrhagic (DIC)
Approx 44% one organ system, with a quarter each having 2 or 3 systems affected
What are the indications to prompt a search for lepto?
AKI
isothenuria with glucosuria without hyperglycaemia
Acute hepatopathy +/- jaundice
Acute resp distress +/- haemoptysis of unclear aetiology with focal or generalised reticulonodular interstitial pattern +/- patchy alveolar conditions
What slightly less common findings should prompt you to consider lepto?
Acute h+ d+ Pyrexia Uveitis/ retinal bleeding Myocardial damage Repro complications
What may you find on haematology?
Mild to severe thrombocytopaenia
Mild to severe anaemia
Neutrophilia
What may you find on biochem?
Azotaemia Raised liver enzymes, esp ALP (tbili > 10 is -ve prognositic indicator) High or low K+/ Phos Low Na, Low Cl High CK High troponin High cPLi
(leptospires inhibit Na-K ATPase in the renal tubule
What may you find on urine analysis?
Blood, glucose, protein, haem, pyruria, bilirubinuria
isosthenuria
granular casts
What may you find on coags?
15% high PT and aPPT
75% high fibrinogen
100% C-reactive protein
75% haptoglobin
What may you see on U/S?
Organomegaly (liver/spleen/kidney) Ascites Pancreatitis Thickened stomach/ intestines Lymphadenomegaly Kidneys - increased echogenicity of the meduallry band, mild pyelectasia, peri-renal fluid accumulation
What is LPHS?
Lung Pulmonary Haemorrhagic
Bilateral, non lobar
Initially caudodorsal lung fields
Interstitial nodular to diffuse alveolar pattern
Rarely mild pleural effusion
Rads may underestimate changes - CT may be better
What are the main options for dx?
Culture MAT dark microscopy PCR ELISA
Outline the use of culture
V slow
Only available test for serovars
Insensitive
Not widely available
Outline the use of dark microscopy
On u+ samples
Poor sens and spec
Need fresh u+ sample
False +ves poss
What are the 2 besst tests?
PCR and MAT
Outline MAT
Microscopic agglutination test
Detects AB in serum sample
Relatively inexpensive
Can get false -ves as takes 7-9d to make the ABs, or the patient may be immunocompromised, the serovar may not be included in the test
Can get false +ves if the pet has been recently vaccinated
Therefore best way to confirm is to 2 tests 1-2 weeks apart
Want to see a 4 fold increase
If >800 suggestive
Outline the use of PCR
On blood, u+, tissue Useful early in the disease process Good if the pet has been vax No info on serovar given Only in blood in first 10d infection, best to test both blood and u+ at the same time, BEFORE AB TX
Why may a pet have a -ve PCR but +ve infection?
Leptospiraemia is transient
Prev AB tx
U+ shedding is delayed after acute infection
What is the test to use to detect a renal carrier?
Urine PCR
Outline the use of ELISAs
For IgM and IgG
IgM - increases in the first week, peak 14d
IgG - increases after 2-3 weeks, peak 1 m, remains high for a while
Very quick but has the same limitations as MAT
If -ve but still suspected, repeat test after a few days
Ideally use in conjunction with MAT titres
Outline AB tx
Needs 14d doxy to clear kidneys
If GI signs, not eating initially, use IV penicillin derivative
If stage 4 AKI - double the dosing interval
Give prophylactic doxy for 14d for all other dogs (not cats) in the house
How do you treat the AKI component
Standard AKI - if using antiemetics, ensure there is no intussusception as these can be seen
When should renal replacement be considered?
Oliguria or anuria Life threatening high K Severe volume overload Advanced uraemia refractory to medical management Ideally refer early!
How do you treat LPHS
Reduce stress and manipulation
Avoid over hydration
02 tx/ mechanical ventilation
Plasma/ whole blood transfusion
What is the Px?
Excellent with early aggressive tx
Success = normalisation of biochem parameters in 14d
50% survivors have renal imparement 12m after - so need to monitor
When should you RC the patient?
1 week post dc, then 1-3w, then 1-6m, then 12m
RC bloods, urine, BP as needed
Outline lepto in cats
Poss reservoirs? No Vax - therefore MAT more useful poss Incubation period longer Hepatic injury less frequent Dx serology or urine PCR Tx doxy
What occurs in the kidneys?
acute interstitial nephritis and tubular dysfunction, although acute tubular necrosis can occur
How do MAT titres change in non-infected dogs
Titers can persist for at least 1 year after natural infection, and in 1 study, generally declined by 4 months after vaccination
Can PCR be affected by recent vaccination?
No
