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Background The role of rodents in Leptospira epidemiology and transmission is well known worldwide. Rats are known to carry different pathogenic serovars of Leptospira spp. capable of causing disease in humans and animals. Wild rats (Rattus spp.), especially the Norway/brown rat (Rattus norvegicus) and the black rat (R. rattus), are the most important sources of Leptospira infection, as they are abundant in urban and peridomestic environments. In this study, we compiled and summarized available data in the literature on global prevalence of Leptospira exposure and infection in rats, as well as compared the global distribution of Leptospira spp. in rats with respect to prevalence, geographic location, method of detection, diversity of serogroups/serovars, and species of rat. Methods We conducted a thorough literature search using PubMed without restrictions on publication date as well as Google Scholar to manually search for other relevant articles. Abstracts were included if they described data pertaining to Leptospira spp. in rats (Rattus spp.) from any geographic region around the world, including reviews. The data extracted from the articles selected included the author(s), year of publication, geographic location, method(s) of detection used, species of rat(s), sample size, prevalence of Leptospira spp. (overall and within each rat species), and information on species, serogroups, and/or serovars of Leptospira spp. detected. Findings A thorough search on PubMed retrieved 303 titles. After screening the articles for duplicates and inclusion/exclusion criteria, as well as manual inclusion of relevant articles, 145 articles were included in this review. Leptospira prevalence in rats varied considerably based on geographic location, with some reporting zero prevalence in countries such as Madagascar, Tanzania, and the Faroe Islands, and others reporting as high as >80% prevalence in studies done in Brazil, India, and the Philippines. The top five countries that were reported based on number of articles include India (n = 13), Malaysia (n = 9), Brazil (n = 8), Thailand (n = 7), and France (n = 6). Methods of detecting or isolating Leptospira spp. also varied among studies. Studies among different Rattus species reported a higher Leptospira prevalence in R. norvegicus. The serovar Icterohaemorrhagiae was the most prevalent serovar reported in Rattus spp. worldwide. Additionally, this literature review provided evidence for Leptospira infection in laboratory rodent colonies within controlled environments, implicating the zoonotic potential to laboratory animal caretakers. Conclusions Reports on global distribution of Leptospira infection in rats varies widely, with considerably high prevalence reported in many countries. This literature review emphasizes the need for enhanced surveillance programs using standardized methods for assessing Leptospira exposure or infection in rats. This review also demonstrated several weaknesses to the current methods of reporting the prevalence of Leptospira spp. in rats worldwide. As such, this necessitates a call for standardized protocols for the testing and reporting of such studies, especially pertaining to the diagnostic methods used. A deeper understanding of the ecology and epidemiology of Leptospira spp. in rats in urban environments is warranted. It is also pertinent for rat control programs to be proposed in conjunction with increased efforts for public awareness and education regarding leptospirosis transmission and prevention., Author summary The role of rodents in the transmission of many diseases, including leptospirosis, is widely known. Rats abundant in urban and peridomestic environments are the most important reservoirs and sources of Leptospira infection in humans and animals. Leptospirosis is a significant but neglected disease of humans and animals that is increasing in incidence in regions affected by natural disasters. This paper summarizes the global prevalence and distribution of Leptospira infection in rats and will add to the literature that supports research, education, and public awareness regarding leptospirosis transmission and prevention.

A pilot seroprevalence study was conducted to document exposure to selected pathogens in wild rats inhabiting the Caribbean island of St. Kitts. Serum samples collected from 22 captured wild rats (Rattus norvegicus and Rattus rattus) were tested for the presence of antibodies to various rodent pathogens using a rat MFI2 serology panel. The samples were positive for cilia-associated respiratory bacillus (13/22, 59.1%), Clostridium piliforme (4/22, 18.2%), Mycoplasma pulmonis (4/22, 18.2%), Pneumocystis carinii (1/22, 4.5%), mouse adenovirus type 2 (16/22, 72.7%), Kilham rat virus (15/22, 68.2%), reovirus type 3 (9/22, 40.9%), rat parvovirus (4/22, 18.2%), rat minute virus (4/22, 18.2%), rat theilovirus (2/22, 9.1%), and infectious diarrhea of infant rats strain of group B rotavirus (rat rotavirus) (1/22, 4.5%). This study provides the first evidence of exposure to various rodent pathogens in wild rats on the island of St. Kitts. Periodic pathogen surveillance in the wild rat population would be beneficial in assessing potential regional zoonotic risks as well as in enhancing the current knowledge when implementing routine animal health monitoring protocols in facilities with laboratory rodent colonies.

Introduction Central Luconia, offshore NW Borneo, is a mature gas province with over 45TCF of gas discovered to date in Miocene carbonate build-ups buried under Miocene-Recent deltaic clastics. Most commercial discoveries to date are in carbonate platforms whose large areas contain substantial hydrocarbon volumes even with relatively short columns. However, the remaining prospectivity resides mostly in pinnacle-shape carbonates where commercial volumes require long hydrocarbon columns (Fig. 1A). Overburden Sequence Stratigraphy Central Luconia has been characterized by tectonic stability throughout the Miocene resulting in depositional cyclicity and carbonate-clastic interactions chiefly reflecting eustatic sea-level variations. It thus differs from the surrounding basins (i.e., West Baram Delta and West Luconia Delta; Fig. 1B) where high subsidence rates have largely over-written the eustatic signal and where the dominant stratigraphic pattern is aggradation with high-relief clinoforms deposited in front of the deltas. In contrast, gentle subsidence across the Central Luconia plateau has produced slabs of relatively thin shallow-water shelf systems characterized by far (up to 150km) and swift migrations of the palaeocoastlines across the flat shelf-top in response to eustatically driven sea-level oscillations. Back-steps of the systems resulting from sea-level rises were followed by swift regressions of the deltas back to the loci of the previous shelf edges (Fig. 2). The overburden clastic stratigraphy is thus organised into a succession of deltaic to shallow-marine shelf units punctuated by erosional unconformities and flooding surfaces. In a vertical sense, the stacked depositional cycles show a shallowing-up tendency with sand-prone lithologies resting on top of each cycle (Fig 2). In a lateral sense, well-developed clinoforms allow the extent of each cycle to be mapped out, along with internal building blocks such as topsets, foresets and bottomsets (Fig. 3A). The terminal shelf edges for most overburden cycles are found along the seaward limit of Central Luconia (Fig. 3B), suggesting that carbonate build-ups have been repeatedly transgressed by the topsets of the advancing shallow-marine shelves and land-locked during lowstands. The same pattern of cyclicity and shallowing-up trends can be followed throughout the stratigraphy. Strata surrounding carbonate platforms still growing near the current shelf-edge, some 150km from the present shoreline and submerged under some 100m of seawater, are demonstrably fluvial in origin and sand-rich (Fig. 4).

Background Toxoplasma gondii is a worldwide protozoan parasite of felids which can infect almost all warm-blooded animals, including humans. Free-roaming chickens are good indicators of environmental contamination with T. gondii oocysts because they feed from the ground. Previous research has demonstrated a high seroprevalence of T. gondii in domestic animals on St. Kitts but little is known about the genotypes circulating in the environment. Methods Hearts and brains from 81 free-roaming chickens in St. Kitts were digested and inoculated into 243 Swiss Webster mice in a bioassay. DNA was extracted from digested chicken tissues and the brains of all mice, and screened for T. gondii. Positive samples were genotyped using restriction fragment length polymorphism. Chicken sera were also screened for T. gondii antibodies using a modified agglutination test (MAT). Results Overall, 41% (33 out of 81) of chickens were positive for T. gondii either by serology and/or by PCR. Antibodies to T. gondii were detected by MAT in 32% (26 out of 81) of chickens, and T. gondii DNA was detected in mouse brains representing 26% (21 out of 81) of chickens. Genotyping of 21 DNA isolates, using polymorphisms at 10 loci, including SAG1, SAG2 (5′-3′ SAG2 and alt.SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico, revealed that 7 were ToxoDB genotype #141, 6 were #1 (Type II), 3 were #13, 3 were #265, one was #264 and one was #2 (Type III). Genotypes #13 and #141 appear to be more virulent. Conclusions The results of this study highlight the greater genetic diversity of T. gondii circulating in the Caribbean region, with potentially different degrees of virulence to humans.