Maximizing the chances of detecting pathogenic leptospires in mammals: the evaluation of field samples and a multi-sample-per-mammal, multi-test approach

TY - JOUR

T1 - Maximizing the chances of detecting pathogenic leptospires in mammals

T2 - the evaluation of field samples and a multi-sample-per-mammal, multi-test approach

AU - Tulsiani, Suhella

AU - Graham, G C

AU - Dohnt, M F

AU - Burns, M-A

AU - Craig, S B

PY - 2011/3

Y1 - 2011/3

N2 - Identification of wild animals that harbour the causative leptospires, and the identification of the most important of these 'wild reservoirs' (in terms of threat to human health), are key factors in the epidemiology of human leptospirosis. In an epidemiological investigation in the Australian state of Queensland, in 2007-2008, samples were collected from fruit bats (Pteropus conspicillatus) and rodents (to investigate the potential role of fruit bats in the maintenance and transmission of leptospires to ground-dwelling rodents) and checked for pathogenic leptospires. The results of these studies have now been carefully analysed in attempts to see which method of detection and type of test sample were best. The effects of pentobarbitone sodium used to euthanize wild mammals before collection of necropsy samples, on the survival and detection of leptospires in vitro, were also explored. In the earlier field investigation, serum, renal tissue and urine were collected from wild mammals, for the detection of pathogenic leptospires by culture, the microscopic agglutination test (MAT), real-time PCR and silver impregnation of smears. Although 27.6% of the rodents investigated were found leptospire-positive, culture only yielded four isolates, probably because many cultures were contaminated. The main aims of the present study were to quantify the performance of the individual diagnostic tests and examine the reasons behind the high incidence of culture contamination. The results of sensitivity and specificity analyses for the different diagnostic tests indicated that isolation by culture (the definitive diagnostic test for leptospiral shedding) had perfect (100%) sensitivity when compared with the results of the PCR but a low specificity (40%). The MAT performed poorly, with a sensitivity of 50% when compared against the results of culture. The prevalence of leptospiral carriage revealed by the PCR-based investigation of kidney and urine samples (59.2%) was higher than that revealed using any other method and far higher than the 2.0% revealed by culture. The results of the culture of renal tissue agreed fairly well with those of the PCR-based investigation of such tissue, with a Cohen's unweighted kappa coefficient (k) of 0.5 (P=0.04). The levels of agreement between other pairs of tests were generally poor.

AB - Identification of wild animals that harbour the causative leptospires, and the identification of the most important of these 'wild reservoirs' (in terms of threat to human health), are key factors in the epidemiology of human leptospirosis. In an epidemiological investigation in the Australian state of Queensland, in 2007-2008, samples were collected from fruit bats (Pteropus conspicillatus) and rodents (to investigate the potential role of fruit bats in the maintenance and transmission of leptospires to ground-dwelling rodents) and checked for pathogenic leptospires. The results of these studies have now been carefully analysed in attempts to see which method of detection and type of test sample were best. The effects of pentobarbitone sodium used to euthanize wild mammals before collection of necropsy samples, on the survival and detection of leptospires in vitro, were also explored. In the earlier field investigation, serum, renal tissue and urine were collected from wild mammals, for the detection of pathogenic leptospires by culture, the microscopic agglutination test (MAT), real-time PCR and silver impregnation of smears. Although 27.6% of the rodents investigated were found leptospire-positive, culture only yielded four isolates, probably because many cultures were contaminated. The main aims of the present study were to quantify the performance of the individual diagnostic tests and examine the reasons behind the high incidence of culture contamination. The results of sensitivity and specificity analyses for the different diagnostic tests indicated that isolation by culture (the definitive diagnostic test for leptospiral shedding) had perfect (100%) sensitivity when compared with the results of the PCR but a low specificity (40%). The MAT performed poorly, with a sensitivity of 50% when compared against the results of culture. The prevalence of leptospiral carriage revealed by the PCR-based investigation of kidney and urine samples (59.2%) was higher than that revealed using any other method and far higher than the 2.0% revealed by culture. The results of the culture of renal tissue agreed fairly well with those of the PCR-based investigation of such tissue, with a Cohen's unweighted kappa coefficient (k) of 0.5 (P=0.04). The levels of agreement between other pairs of tests were generally poor.

KW - Animals

KW - Bacteriological Techniques

KW - Carrier State

KW - Chiroptera

KW - Disease Reservoirs

KW - Disease Vectors

KW - Kidney

KW - Leptospira

KW - Leptospirosis

KW - Mammals

KW - Polymerase Chain Reaction

KW - Rodent Diseases

KW - Rodentia

KW - Specimen Handling

KW - Spleen

U2 - 10.1179/136485911X12899838683205

DO - 10.1179/136485911X12899838683205

M3 - Journal article

C2 - 21396251

SN - 2047-7724

VL - 105

SP - 145

EP - 162

JO - Pathogens and Global Health

JF - Pathogens and Global Health

IS - 2

ER -