Leptospirosis

Question 1

What is zoonosis?

Answer 1

= an infectious disease that is transmitted between species (sometime by a vector) from animals (other than humans) to humans

= can also have reverse zoonosis / anthroponosis
(from humans to animals)

Question 2

What is Leptospira sp?

Answer 2

Morphology
= gram - negative
= obligate aerobe spirochete
= periplasmic flagella
= motile, heliocidal
= 6-20 um in length, -.1 um in diameter

Ultrastructure
= heliocidal protoplasmic cylinder
= two axial filaments (between cylinder + envelope)
= outer envelope
= hooked ends

Physiology
= obligate aerobes , (+) respiratory metabolism
= transverse division
= oxidase, catalase + peroxidase positive
= optimal pH 7.2-7.4

Antigenic structure
= 13 species + >250 serovars

Determinants of pathogenicity
= soluble hemolysin
= endoflaggellum
= metallopeptidases
= collagenase
= resistance to oxidative stress
= OmpA loa22 (lipoprotein , function unknown)
= cell-mediated sensitivity reactions
= haem oxygenase
= endotoxin (LPS)

(LPS target = renal tubular Na, K-ATPase + H, K-ATPase activities)

Question 3

What is an example sp. of Leptospira?

Answer 3

= Leptospira interrogans

= results in clinical infection of Leptospirosis / Weil’s disease

(another example = Leptospira borapetersenii = causes Hardjo disease)

Question 4

What is Leptospirosis (/Weil’s disease)?

Answer 4

(caused by Leptospira interrogans)

= zoonotic disease, only some strains are pathogenic

= icterohaemorrhagiae = main serovar causing human disease

Question 5

What is the transmission of Leptospirosis?

Answer 5

= wide range of host reservoirs

= humans at risk are those with direct/indirect contact with animals / animal products

= esp. indirect contact with urine infected with virulent Leptospira from carrier / infected animal

= also from soil , food, water = through break in skin and mucus membranes

= readily killed by >60oC, detergents, desiccations + acids

Question 6

What is the pathogenesis of Leptospirosis?

Answer 6

= migration from bloodstream into lungs, liver, kidneys + CSF
(causes aggravation disease)

Renal injuries :
= interstitial nephritis with associated glomerular swelling
= hyperplasia
= thickening of basement membranes + tubules
= leads to renal failure

Heaptic injuries:
= heaptocellular disease due to vasculitis

Meningitis

Symmetric pretibial rash

Question 7

What is the clinical manifestation of Leptospirosis?

Answer 7

= incubation period of 10-12 days

= sudden chills with fever, headache, conjunctival suffusion, myalgia, GIT symptoms

= first leptospiremic stage (7 days)

= defervescence (abatement of fever)

= second leptospiremic stage (< 7 days)

= reside / avoid macrophages inducing high levels of cytokines
(causing spesis-like symptoms = life-threatening)

Question 8

How is Leptospirosis treated / prevented?

Answer 8

Antibiotic treatment within first 2 days after onset
= (penicillin, streptomycin, tetracycline, erythromycin)

Serovar-specific vaccine

Prophylaxis with short / long-term tetracycline

Question 9

What are some examples of exposure to Leptospira infections?

Answer 9

Occupational exposure
= water / animal
e.g. farmers, abattoir working, gamekkeper, stagnant water on building sites, rowing instructor

Recreational exposure
= water / animals
e.g. water sports, pet rats, sewers