Considerable progress has been made in the field of leptospiral vaccines development since its first use as a killed vaccine in guinea pigs. Despite the fact that the immunity conferred is restricted to serovars with closely related lipopolysaccharide antigen, certain vaccines have remained useful, especially in endemic regions, for the protection of high-risk individuals. Other conventional vaccines such as the live-attenuated vaccine and lipopolysaccharide (LPS) vaccine have not gained popularity due to the reactive response that follows their administration and the lack of understanding of the pathogenesis of leptospirosis. With the recent breakthrough and availability of complete genome sequences of Leptospira, development of novel vaccine including recombinant protein vaccine using reverse vaccinology approaches has yielded encouraging results. However, factors hindering the development of effective leptospiral vaccines include variation in serovar distribution from region to region, establishment of renal carrier status following vaccination and determination of the dose and endpoint titres acceptable as definitive indicators of protective immunity. In this review, advancements and progress made in LPS-based vaccines, killed- and live-attenuated vaccines, recombinant peptide vaccines and DNA vaccines against leptospirosis are highlighted.
Here, we investigated an outbreak of leptospirosis among reserve military recruits that occurred following a survival exercise in the Hulu Perdik forest within the Hulu Langat district, Kuala Lumpur, Malaysia. Blood samples from the 12 patients that presented symptoms for febrile illness on clinical examination were subjected to laboratory investigation, comprising Lepto IgM rapid test, IgM ELISA, and microscopic agglutination test (MAT). All these patients were interviewed for possible risk factors for leptospirosis. Rodent trapping and environmental sampling for possible isolation of leptospires in the outbreak site was performed. The isolated leptospires were genetically characterized and investigated for the potential epidemiological link with human leptospirosis. Among the 12 patients, two (2/12; 16.6%) were confirmed positive for leptospirosis by microscopic agglutination test (MAT with titers 400-800; serovar autumnalis and hardjobovis). Two Leptospira species from rodents (L. interrogans and L. borgpetersenii) and two from the environment (L. kmetyi and L. wolffii) were identified. The possible epidemiological link between human serovars and animal Leptospira species indicates rodents as the potential reservoir while the environment (soil and water) serves as a transmission route. This investigation highlights the robust presence of pathogenic leptospires on Malaysian environment and rodents which may present the risk of infection, especially among high-risk individuals. Hence, occupational risk individuals are cautioned to observe appropriate preventive measures including prophylaxis and seek immediate medical attention for any illness following similar activities.
Leptospirosis is caused by the spirochetal bacterium Leptospira of which rodents are considered the most important reservoir. This study aims to determine and characterize virulent Leptospira species among rodents and small mammals found in human settlements and recreational spots within the Hulu Langat and Gombak districts of Selangor, Malaysia; regions that frequently report probable human leptospirosis cases. Molecular analysis revealed an overall Leptospira detection rate of 14.3% among the 266 small mammals captured, and the human settlements were found to have the highest number of isolates (15.1%), followed by recreational sites (14.5%). The molecular characterization conducted based on the lipL32, secY genes and MLST revealed that the strains belonged to four different species, including; Leptospira interrogans (29; 76.3%; ST50, ST238, ST243), L. kirschneri (5; 13.15%; ST110), L. borgpetersenii (3; 8%; ST143) and L. weilii (1; 2.63%; ST242). The study revealed genotypes of circulating strains among small mammals in Malaysia, which include Leptospira locus ST110 L. kirschneri, ST 50 L. interrogans, ST143 L. borgpetersenii and ST242 L. weilii. Among the small mammals studied, 17/105 (16.2%) Rattus norvegicus, 7/59 (11.9%) of Rattus rattus, 5/24 (20.8%) of Maxomys whiteheadi, 4/18 (22.2%) of Sundamys muelleri, 2/22 (9%), Tupaia gliss, 2/16 (12.5%) Rattus tiomanicus and 1/4 (25%) of Suncus murinus carried pathogenic leptospires. The data from the present study may imply that, in addition to rodents, other small mammals also serve as maintenance hosts for Leptospira. Hence, much remains unknown about Leptospira maintenance hosts, and there is need for further investigation to ascertain the prevailing serovars of pathogenic Leptospira in Malaysia. This will assist in the development of efficient diagnostic assays with improved microscopic agglutination test (MAT) panels, and in the implementation of suitable prevention and control measures.