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Leptospirosis
Microbiology
Life-cycle
- usual hosts: small wild animals eg rodents, hedgehogs, and larger
farm/domestic animals eg pigs, cattle, dogs
- excreted in urine and found in stagnant water and wet soil
- humans infected whilst working in paddy fields or on farms, swimming in
contaminated water or playing with dogs, via skin, conjunctiva, mucous membranes
- incubation usually 5-14 days (2-20)
Serogroups
Leptospira canicola
- host often canine
- children playing with puppies may develop Canicola fever; may be associated
with aseptic meningitis
- often passed from pigs to rats and vice versa with farm workers as incidental
hosts
Leptospira icterohaemorrhagiae
- rats best known resevoir
- in humans may cause Weil's disease
Leptospira hebdomadis
- cattle, field mice and voles are the main resevoirs
Clinical features
Severity depends on dose of organisms and host factors. Mild form may be
subclinical and can only be diagnosed by serology
2 presentations:
- Weil's disease, with jaundice and multi-organ development
- acute but anicteric form with milder clinical symptoms. 90% of patients
Both forms follow biphasic course after incubation period
Septicaemic phase
Lasts 4-7 days and consists of fevers and chills and:
- Respiratory system
- pulmonary involvement frequent
- dry cough, occasionally with blood-stained sputum
- +/- creps
- +/- pleural rub (rare)
- Cardiovascular
- +/- pericardial rub (rare)
- CCF and hypotension in severe cases
- tachycardia common
- Splanchnic
- abdominal pain
- nausea and vomiting
- splenomegaly in 15-20% (not massive)
- hepatomegaly
- cholestatic jaundice, with liver impairment in severe cases
- 70% of patients who present to ICU are jaundiced
- does not progress to hepatic failure
- Genitourinary
- renal involvement invariable: ranges from urinary sediment changes and
mild proteinuria to renal failure (67% of patients)
- renal failure usually non-oliguric
- associated with hypokalaemia
- creatinine raised out of proportion to urea
- rarely: orchitis, epididymitis, prostatitis
- Central nervous system
- headache: intense, +/- throbbing, often not controlled by analgesics.
Commonly frontal, may be associated with retrobulbar pain
- Skin
- macular, maculopapular, erythematous, urticarial or haemorrhagic rash
- largely confined to the trunk
- ENT
- pharyngitis
- +/- epistaxis
- parotitis and otitis media rare
- Eye
- conjunctival suffusion and haemorrhage
- photophobiaocular pain
- Musculoskeletal
- myalgia: hallmark of condition. Calf, abdo and lumbar-sacral muscles
most often affected
- arthritis (rare)
Immune phase
- 4-30 days
- fever has already subsided with disappearance of leptospires from most
tissue except kidney and aqueous fluid. Coincides with an increase in
circulating antibody titres
- asymptomatic in 35% of cases
- renal and heptic manifestations continue from first period
- CNS
- meningeal symptoms in 40%, decrease within a few days. Responsible for
6% of lymphocytic meningitis
- CSF pleocytosis, predominantly polys initially
- +/- raised CSF pressure
- encephalitis, focal weakness, spasticity, paralysis, nystagmus, fits,
visual disturbance, peripheral neuritis, cranial nerve palsies,
radiculitis, myelitis and Guillain-Barre rare
- Eyes
- anterior uveal tract may be affected by the 3rd week of the illness.
Characterised by:
- iritis
- iridocyclitis
- chorioretinitis
- may uni- or bilateral
Investigations
Haematology
- raised WBC with neutrophilia. Leucopaenia can occur
- raised ESR
- raised fibrinogen with consequent increase in plasma viscosity
- raised FDPs
- thrombocytopaenia. Severity reported to be related to severity of disease
Biochemistry
- +/- raised urea and creatinine
- markedly raised alk phos and bilirubin with moderately increased transaminases
- normal INR. Combination of high bilirubin and alkaline phosphatase and
normal INR highly suggestive of leptospirosis
CSF
- increased polys initially, later mononuclear cells.
- glucose normal
- protein v. slightly raised
Immunology
- decreased C3 in early stages
- leptospiral complement fixation test and micro-agglutinins become positive
during the second week. Repeat samples to show a rising titre
Microbiology
- dark-ground microscopy and culture of urine. Alkalinise urine before
collection. May be positive in 2nd week. Usually +ve by 3rd.
- dark-ground microscopy and culture of blood. May be +ve in 1st week
CXR
- variety of lesions including small patchy lesions, confluent infiltration
or even consolidation
Differential diagnosis
- malaria
- may be advisable to treat patients for both severe malaria and
leptospirosis until the diagnosis becomes clear
- enteric fever
- rickettsial disease
- glandular fever
- brucellosis
- viral hepatitis
- influenza
- dengue
- relapsing fever
- atypical pneumonia
- aseptic meningitis
Prevention
- protective clothing for those at occupational risk (eg sewerage/abattoir
workers)
- rodent control
- disinfection of infected premises
- prophylactic penicillin for high-risk patients who develop cuts/abrasions
while at work
Treatment
- benzylpenicillin 1 MU qds IV for 1/52
- must be given within 4-7 days of onset
- decrease dose in renal failure
- tetracycline for penicillin sensitive patients
Prognosis
- usually favourable |
