Leptospirosis

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 cross-reactivity 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 Reservoir 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 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 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 Anicteric leptospirosis Icteric leptospirosis

Clinical Notes cont. Anicteric leptospirosis - mild fever with sudden onset 90% of cases Headache Chills Severe myalgia (calves and thighs) Skin rash (on occasion) Icteric leptospirosis – more severe form 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 Treatment 7 - 12 days Antibiotics beneficial if given in the first 4 days of illness Penicillin, Doxycycline, Cephalosporins, Erythromycin

Differential diagnosis Investigate the possibility of the following: Influenza Dengue fever Malaria Typhoid Other disease that may mimic leptospirosis include 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 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 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 Panbio Leptospira IgM Dip-S-Tick 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 Indirect ELISA IgM ELISA only, as IgG antibodies not always produced. Diagnosis using one serum sample only Fast - 1hr 10min assay time

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

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