Transcript West Nile virus

Leptospirosis
The disease and Panbio product training
Overview
• Presumed to be the most widespread zoonosis in the
world (WHO 1999)
• Also referred to as Weil’s disease as it was first
described by Adolf Weil in 1886.
• Animals are reservoirs, infections may occur from
contact with infected animals, their urine or
contaminated water, soil or vegetation.
• Infection is often an occupational hazard.
Infectious agent
• Caused by Leptospira interrogans
– Thin, highly motile spirochaetes
– More than 200 serovars of which there are 23 serogroups
– Serovars are antigenically related – high degree of crossreactivity
– In Australia, L. interrogans serovar hardjo is most common
in infections of people in contact with animals
– In Europe serovars copenhageni and icterohaemorrhagiae
(carried by rats) are usually responsible for infection
– In SouthEast Asia serovar lai is common
Epidemiology
• Occurrence
– Worldwide however incidence is highest in tropical regions
due to longer survival of leptospires in warm, humid
conditions
– Disease is seasonal
• Temperate regions – peak occurs in summer or fall
• Tropical regions – peak occurs during rainy season
• Reservoir
– Animals (Rodents, dogs, sheep, pigs, cattle)
Transmission
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Enters body when mucous membranes or abraded skin
come in contact with contaminated environmental sources
(animal urine, contaminated water, soil or vegetation).
Multiplies in the blood and tissue and can spread to any part
of the body but tends to affect the liver and kidney.
Infection is often an occupational hazard.
Recreational activities such as canoeing, hiking and fishing
pose a risk also.
• 1997 US travelers visiting Costa Rica contracted lepto while
white-water rafting
• 1998 athletes who participated in a triathlon in Illinois
developed lepto after swimming in a lake.
• Eco-Challenge-Sabah 2000 athletes in Malaysia developed
lepto most likely from kayaking/swimming in the Segama River.
Clinical Notes
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Clinical presentation in man is variable making
diagnosis difficult
May imitate other diseases e.g. dengue fever and viral
haemorrhagic diseases (WHI, ILS)
The majority of infections are subclinical or very mild
Symptoms may recur 7-10 days after initial episode
Infection may be categorized into two forms
1. Anicteric leptospirosis
2. Icteric leptospirosis
Clinical Notes cont.
1. Anicteric leptospirosis - mild fever with sudden onset
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90% of cases
Headache
Chills
Severe myalgia (calves and thighs)
Skin rash (on occasion)
2. Icteric leptospirosis – more severe form
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Progresses rapidly
Characterised by jaundice. Abdominal pain with diarrhea
or constipation, hepatosplenomegaly, nausea, vomiting
and anorexia are also seen.
Mortality rate of between 5 and 10% (Heath 1965)
Complications include acute renal failure, pulmonary
haemorrhage, respiratory involvement, myocarditis and
ocular involvement
Clinical Notes cont.
• Incubation period
– 7 - 12 days
• Treatment
– Antibiotics beneficial if given in the first 4 days of illness
• Penicillin, Doxycycline, Cephalosporins, Erythromycin
Differential diagnosis
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Investigate the possibility
of the following:
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Influenza
Dengue fever
Malaria
Typhoid
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Other disease that may
mimic leptospirosis include
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Encephalitis
Poliomyelitis
Rickettsiosis
Glandular fever
Brucellosis
Malaria
Viral hepatitis
Pneumonitis
Dengue & lepto misdiagnosis
• Differentiation on clinical grounds between dengue and
leptospirosis may be impossible during the early
stages of the illness (Levett et al 2000)
– Levett at al (2000) found a large proportion diagnosed with
leptospirosis actually had dengue and vice versa.
– Dual infections may also occur (Levett et al 2000)
– The characteristic rash of dengue may be the only
distinguishing feature
• An outbreak of an undifferentiated fever in India (2000)
was thought to be a “viral” or “dengue-like” illness.
– Investigation by Karande et al found that at least 1/3 had
leptospirosis.
Antibody Response
• Immunity to specific serovar after infection.
• Antibodies from an infection with a particular serovar
do not necessarily protect against infection with other
serovars (WHO, ILS)
• IgM antibody
– detectable from 2nd day of infection and usually occurs in
all patients
– IgM antibody may persist for several months
• IgG antibody
– rises for 10-30 days after onset of symptoms
– IgG antibody may not occur in all patients
Diagnosis
• Diagnostic Aids
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Isolation
Microscopic Agglutination Test (MAT)
Dip-S-Tick
IgM ELISA
Isolation
• Transitory bacterial shedding, although may be
present up to 7-10 days after onset of symptoms in
blood and CSF.
• May be isolated from urine from 7-30 days.
– Organism is fastidious in its growth requirements.
– Culture difficult to perform and can take 6-8 weeks to obtain
isolates.
Microscopic Agglutination Test
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Abbreviation = MAT
IgM antibody is the major antibody detected by MAT
Antibodies may not be detectable for up to 21 days
Requires maintenance of live pathogenic leptospires
Subjective interpretation – best results with highly
skilled personnel
• Requires paired sera for optimal results
• Recent studies suggest that the MAT is less sensitive
than the ELISA (Levett et al, 2001)
Panbio leptospirosis products
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Panbio Leptospira IgM Dip-S-Tick
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USA-FDA Cleared
Simple to use – no specialised equipment required
Ideal for small volume testing
Visual reading
Built in control well
Detects positives earlier than MAT
Detects antibodies to a broad range of serovars
Panbio Leptospira IgM ELISA
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Indirect ELISA
IgM ELISA only, as IgG antibodies not always produced.
Diagnosis using one serum sample only
Fast - 1hr 10min assay time
Detects positives earlier than MAT
Detects antibodies to a broad range of serovars
Panbio leptospirosis products
• High sensitivity and specificity demonstrated by
independent studies
Panbio Leptospirosis IgM ELISA
Specific serum antibodies combine with leptospirosis
antigens attached to the polystyrene
surface of the microwells
Washing removes residual serum
Peroxidase-conjugated anti-human specific
immunoglobulin is added
The colourless substrate,
tetramethylbenzidine/hydrogen peroxide (TMB /
H2O2) is hydrolysed to a blue chromogen
Stopping the hydrolytic reaction
with acid turns the TMB yellow
Colour development indicates the presence
leptospirosis antibodies in the test sample
Panbio Serological Assays
• Offer alternative to culture and MAT
• Can facilitate differential diagnosis
• Tests to meet demands of either sporadic cases or
high throughput screening