1.2 History of Leptospirosis in Malaysia

        In April 1925, Fletcher encountered by chance the first case of leptospirosis in the Institute of Medical Research, Kuala Lumpur, Malaysia 10 years after the isolation of Leptospira for the first time from human patient blood in Japan (Inada, Ido, Hoki, Kaneko, & Ito, 1916). Fletcher also identified 3 different serovars (Leptospira interrogans serovar Icterohaemorrhagiae, Hebdomadis, and Pyrogenes) after isolating the pathogen from the liver, blood and kidney from the 21 patients in Malaysia. The blood from a patient with unknown origin fever was inoculated into guinea pigs and it developed jaundice and hemorrhages in the nose. The guinea pig died 13 days after inoculation and the postmortem result showed signs of leptospirosis. Fletcher also introduced a new medium in semi-solid form that is widely used in many laboratories nowadays for the isolation and maintenance of the leptospira culture (Fletcher, 1928).

Picture of two cultures of Leptospira sp. strain Manara. Two cultures of Leptospira sp. strain Manara in Fletcher medium supplemented with 3% (left tube) and 1% (right tube) seawater after 48 h of incubation at 28°C. The dinger rings corresponding to Leptospira sp. growth is indicated with red arrows. doi:10.1371/journal.pone.0144974.g001

In the earlier stage of work regarding the Leptospirosis in Malaysia, it only focused on the patients who were in the military hospital. In 1957, it was reported that 614 military personnel and 238 civilian patients admitted at the military hospital were suffering from the fever. Based on the serology test, 34.7% and 13% respectively were confirmed to have Leptospirosis (McCrumb et al, 1957). There was also a previous study that concluded that rubber plantation laborers and the workers at sewage, drainage, forestry, and town cleaning as well as antimalarial workers were exposed to high risk of Leptospirosis infection and become the an occupational disease (Shafie et al, 2012). However, travel to endemic areas and recreational activities such as water sports have increasingly been reported as a major risk for this infection (Victoriano et al, 2009). 

In 2014, it was reported that the peak of the leptospirosis cases was 7806 confirmed cases with 92 deaths (Zainudin, 2015). It does not include the cases that may be under-reported or misdiagnosed and it can be considered as a significant public health threat locally. In 2016, it has been reported that forty-two patients with confirmed diagnosis of leptospirosis in Perak. The case fatality rate was 14.3%. Malay ethenic was the most affected by the diseases and majority of them were male (Fann, Vidya, Chong, Indralingam, & Christoper Chan, 2020). Minly, the outbreak would occur after the effect of heavy rainfall or flood season and it can be a seasonal incidence.