Epidemiology of Leptospira Transmitted by Rodents in Southeast Asia

Abstract

BackgroundLeptospirosis is the most common bacterial zoonoses and has been identified as an important emerging global public health problem in Southeast Asia. Rodents are important reservoirs for human leptospirosis, but epidemiological data is lacking.Methodology/Principal FindingsWe sampled rodents living in different habitats from seven localities distributed across Southeast Asia (Thailand, Lao PDR and Cambodia), between 2009 to 2010. Human isolates were also obtained from localities close to where rodents were sampled. The prevalence of Leptospira infection was assessed by real-time PCR using DNA extracted from rodent kidneys, targeting the lipL32 gene. Sequencing rrs and secY genes, and Multi Locus Variable-number Tandem Repeat (VNTR) analyses were performed on DNA extracted from rat kidneys for Leptospira isolates molecular typing. Four species were detected in rodents, L. borgpetersenii (56% of positive samples), L. interrogans (36%), L. kirschneri (3%) and L. weilli (2%), which were identical to human isolates. Mean prevalence in rodents was approximately 7%, and largely varied across localities and habitats, but not between rodent species. The two most abundant Leptospira species displayed different habitat requirements: L. interrogans was linked to humid habitats (rice fields and forests) while L. borgpetersenii was abundant in both humid and dry habitats (non-floodable lands).Conclusion/Significance L. interrogans and L. borgpetersenii species are widely distributed amongst rodent populations, and strain typing confirmed rodents as reservoirs for human leptospirosis. Differences in habitat requirements for L. interrogans and L. borgpetersenii supported differential transmission modes. In Southeast Asia, human infection risk is not only restricted to activities taking place in wetlands and rice fields as is commonly accepted, but should also include tasks such as forestry work, as well as the hunting and preparation of rodents for consumption, which deserve more attention in future epidemiological studies.

A Comparative Study of the Epidemiology of Human Leptospirosis in Korea and Japan between 2006 and 2012

“…HL is transmitted from rodents via direct contact with infected urine or from infected surfaces. The pathogenic agent is known to persist in highly humid environments for longer periods (1)(2)(3)(4)(5)8). Although the global burden of this disease is unknown because of the paucity of data, the incidence is estimated to range from 0.1/100,000 to 1/100,000 of the population per year in temperate regions, to over 100/100,000 of the population per year during epidemics in the tropics.…”

Parasite diversity of disease-bearing rodents of Southeast Asia: habitat determinants and effects on sexual size dimorphism and life-traits

“…For microparasites, rodent species were investigated for hantaviruses, protists (Toxoplasma gondii, Trypanosoma levisi, and Trypanosoma levansii), Leptospira species (L. borgpetersenii; L. interrogans; L. kirshneri and L. wakefefiedae) and Bartonella sp.(B. coopersplainsensi; B. elizabethae; B. queenslandensis; B. rattimassiliensis; B.tribocorum; B. musii and B. phoceensis); (Jittapalapong et al, 2011;Jiyipong et al, 2012;Cosson et al, 2014;Pumhom et al, 2014Pumhom et al, , 2015. Table 1 summarizes the helminth species richness and microparasite species richness obtained from these published studies.…”

Leptospirosis and Extensive Urbanization in West Africa: A Neglected and Underestimated Threat?

“…Floods and heavy seasonal rainfall in tropical countries have been demonstrated to be a major cause of outbreaks [7,8]. Little is known about the circulating etiological agents of leptospirosis in most of the regions of the World but there is increasing evidence that leptospires are not only circulating in wetlands, as is commonly accepted, but also in arid regions (e.g., Niger: [9]) or dry non-floodable habitats (e.g., Southeast Asia: [10]). While traditionally associated with rural environments(e.g., [11,12]), leptospirosis is now also considered as an emerging disease in urban slum communities with poor sanitation infrastructure (e.g., [13][14][15][16]).…”