A duplex endpoint PCR assay for rapid detection and differentiation of Leptospira strains

Host population structure and rare dispersal events drive leptospirosis transmission patterns among Rattus norvegicus in Boston, Massachusetts, US

Leptospirosis (caused by pathogenic bacteria in the genus Leptospira ) is prevalent worldwide but more common in tropical and subtropical regions. Transmission can occur following direct exposure to infected urine from reservoir hosts, such as rats, or a urine-contaminated environment, which then can serve as an infection source for additional rats and other mammals, including humans. The brown rat, Rattus norvegicus , is an important reservoir of leptospirosis in urban settings. We investigated leptospirosis among brown rats in Boston, Massachusetts and hypothesized that rat dispersal in this urban setting influences the movement, persistence, and diversity of Leptospira . We analyzed DNA from 328 rat kidney samples collected from 17 sites in Boston over a seven-year period (2016-2022); 59 rats representing 12 of 17 sites were positive for Leptospira . We used 21 neutral microsatellite loci to genotype 311 rats and utilized the resulting data to investigate genetic connectivity among sampling sites. We generated whole genome sequences for 28 Leptospira isolates obtained from frozen and fresh tissue from some of the 59 Leptospira -positive rat kidneys. When isolates were not obtained, we attempted Leptospira genomic DNA capture and enrichment, which yielded 14 additional Leptospira genomes from rats. We also generated an enriched Leptospira genome from a 2018 human case in Boston. We found evidence of high genetic structure and limited dispersal among rat populations that is likely influenced by major roads and/or other unknown dispersal barriers, resulting in distinct rat population groups within the city; at certain sites these groups persisted for multiple years. We identified multiple distinct phylogenetic clades of L. interrogans among rats, with specific clades tightly linked to distinct rat populations. This pattern suggests L. interrogans persists in local rat populations and movement of leptospirosis in this urban rat community is driven by rat dispersal. Finally, our genomic analyses of the 2018 human leptospirosis case in Boston suggests a link to rats as the source. These findings will be useful for guiding rat control and human leptospirosis mitigation efforts in this and other urban settings.

Epidemiology of leptospirosis in Tanzania: A review of the current status, serogroup diversity and reservoirs

Background

Tanzania is among the tropical countries of Sub-Saharan Africa with the environmental conditions favorable for transmission of Leptospira. Leptospirosis is a neglected zoonotic disease, and although there are several published reports from Tanzania, the epidemiology, genetic diversity of Leptospira and its host range are poorly understood.

Methods

We conducted a comprehensive review of human and animal leptospirosis within the 26 regions of the Tanzanian mainland. Literature searches for the review were conducted in PubMed and Google Scholar. We further manually identified studies from reference lists among retrieved studies from the preliminary search.

Results

We identified thirty-four studies describing leptospirosis in humans (n = 16), animals (n = 14) and in both (n = 4). The number of studies varied significantly across regions. Most of the studies were conducted in Morogoro (n = 16) followed by Kilimanjaro (n = 9) and Tanga (n = 5). There were a range of study designs with cross-sectional prevalence studies (n = 18), studies on leptospirosis in febrile patients (n = 13), a case control study in cattle (n = 1) and studies identifying novel serovars (n = 2). The most utilized diagnostic tool was the microscopic agglutination test (MAT) which detected antibodies to 17 Leptospira serogroups in humans and animals. The Leptospira serogroups with the most diverse hosts were Icterohaemorrhagiae (n = 11), Grippotyphosa (n = 10), Sejroe (n = 10), Pomona (n = 9) and Ballum (n = 8). The reported prevalence of Leptospira antibodies in humans ranged from 0.3–29.9% and risk factors were associated with occupational animal contact. Many potential reservoir hosts were identified with the most common being rodents and cattle.

Conclusion

Leptospirosis is prevalent in humans and animals in Tanzania, although there is regional and host variation in the reports. Many regions do not have information about the disease in either humans or their animal reservoirs. More studies are required to understand human leptospirosis determinants and the role of livestock in leptospirosis transmission to humans for the development of appropriate control strategies.

Bacteria from the genus Leptospira is an important agent for causing a disease called leptospirosis in humans and a range of animal species. Leptospirosis is often under-recognized as it presents varied symptoms that mimic malaria, typhoid, brucellosis and other diseases. More than 250 pathogenic Leptospira serovars are known to cause leptospirosis in humans and animals. The diversity of Leptospira serovars and their distribution in humans and animals is little defined in Tanzania. We conducted a systematic review to gather information on the diversity of Leptospira serovars with their reservoir distribution and the most common diagnostics methods used. We included studies (n = 34) in the review and found 17 serogroups described in 28 studies that utilized microscopic agglutination test (MAT). So far human and other animal hosts including cattle, dogs, pigs, bats, buffalo, fish, rodents, goats, lion, zebra, sheep and shrews have been investigated for leptospirosis in Tanzania. Our results show that cattle and rodents are likely to be important reservoirs of pathogenic Leptospira spp. and can be a source of human leptospirosis principally in the farming system. Further studies are needed to explore predominant serovars in livestock for the development of prevention strategies to reduce transmission and risks in humans.

Use of the Leptospira sp. ligB C-terminus coding region as a diagnostic tool of animal leptospirosis

Leptospirosis is the most widespread zoonosis worldwide, and it can cause reproductive failures in livestock, while in humans may vary from a mild fever to multi-organ failure and death. Due to this, in this study, we evaluated the usefulness of the segment encoding LigB C-terminus region, only present in pathogenic as target for a diagnostic PCR. This new PCR yielded a 100 % positivity for pathogenic Leptospira species and no cross-reactivity was found with intermediate or non-pathogenic species, or with other microorganisms, demostrating its high analytical specificity. The estimated analytical sensitivity was higher in serum samples than in blood or urine samples (6-9 × 10² lept/mL and 6-9 × 10⁵ and 6-9 × 10⁶ lept/mL, respectively). Multiple sequence alignment of the target region from different pathogenic Leptospira species confirmed that this gene region is highly conserved among these species, with few single nucleotide polymorphisms. The ligb-ct PCR here developed appears as a useful tool for the molecular diagnosis of leptospirosis.

Leptospira infection in people in the city of Durango, Mexico: a cross sectional study

Objective

To determine the seroprevalence of Leptospira immunoglobulin (Ig)G and IgM antibodies and its association with the characteristics of the study population from the northern Mexican city of Durango, Mexico.

Methods

Through a cross-sectional study design, inhabitants of Durango City, Mexico were surveyed between June 2018 and November 2018. Serum samples from the subjects were analysed for anti-Leptospira IgG and IgM antibodies using commercially available enzyme-linked immunosorbent assays. Sociodemographic, clinical, behavioural and housing characteristics were recorded. Data were analysed by bivariate and multivariate analyses.

Results

The study enrolled 413 people, of which 124 (30.0%) and 137 (33.2%) were positive for anti-Leptospira IgG antibodies and anti-Leptospira IgM antibodies, respectively. Multivariate analysis showed that Leptospira seropositivity was associated with professional occupation, alcohol consumption, ill clinical status, memory impairment and a history of surgery.

Conclusions

This is the first study to report the seroepidemiology of Leptospira infection in an urban general population in the north of Mexico. The seroprevalence of Leptospira infection found was higher than those previously reported in Mexican studies.

Development of a Multiplex PCR Assay for Detection and Discrimination of Pathogenic and Saprophytic Leptospira in Water

Leptospirosis is a zoonosis prevalent in tropical countries and affects animals and humans alike. Leptospira interrogans, the causative organism for this waterborne infection, spreads through the urine of infected animals. There is a direct link between contaminated water and Leptospira outbreaks. This study reports a rapid assay to detect and differentiate pathogenic Leptospira from non-pathogenic in environmental water using multiplex PCR. The assay uses primers targeting the Lipl32 and Lipl21 gene. The multiplex PCR has been standardized using 11 pathogenic and one saprophytic serovar of Leptospira. The analytical sensitivity of the developed method was evaluated with different concentrations of template DNA. This method was used to screen water samples collected from 20 different sources from Chengalpattu town in Kancheepuram District, Tamil Nadu, India. Of the 20 water samples screened, 13 samples tested positive for pathogenic Leptospira, and seven samples tested negative. Four water samples were found to carry both pathogenic and saprophytic species. The developed multiplex PCR assay is highly useful for detecting and distinguishing pathogenic and saprophytic leptospires in water.