Making a breakthrough in the study of leptospirosis, a bacterial infection transmitted from animals, a team of Sri Lankan researchers in a collaborative endeavour has discovered six new genotypes of this largely undermined tropical disease. In an exclusive interview with the Sunday Island, they throw light on the findings of their research which are now in international literature enabling new knowledge on the world’s commonest zoonotic disease.

by Randima Attygalle

No longer considered the ‘rural farmer’s disease’, leptospirosis, commonly called rat fever or mee una in Sinhala, is changing its dynamics, urging clinicians, health policy-makers and the public to revisit this common tropical disease of both humans and animals. The bacterium that causes leptospirosis is spread through the urine of infected animals, which can get into water or soil and can survive there for weeks or months. Many different kinds of wild and domestic animals carry the bacterium including cattle, pigs, rodents, dogs, horses and wild animals.

Humans can become infected with the bacterium either through contact with urine of an infected animal or with water or soil contaminated with the urine of infected animals. The bacteria can enter the body through skin, eyes, nose or mouth. Outbreaks of leptospirosis are usually caused by exposure to contaminated water, such as floodwaters. It is a serious occupational hazard for those working outdoors such as farmers, miners etc. and professionals such as veterinarians in close contact with animals. According to global research findings, around one million cases of leptospirosis and 58,900 deaths are estimated to occur worldwide each year. More than 70% of the deaths are reported from the tropical, poorest regions of the world.

A re-merging disease here at home, leptospirosis has gained much attention since the large outbreak in 2008. “The annual incidence of leptospirosis that had required hospitalization from 2008 to 2015 was 52.1 per 100,000 people, with an estimated case fatality rate of 7.0% according to National Health Bulletin data. In 2018 there was another resurgence in numbers. The disease is no more a ‘seasonal’ one as it was conventionally known to be, resulting in multiple outbreaks per year, notably during rainy seasons. Manifestations of the disease have also changed, with a wide array of new clinical entities such as pulmonary haemorrhage (bleeding into the lungs), pancreatitis, and myocarditis coupled with high case fatality. These shifts in the disease call for new strategies, new interventions and the need to reorganize ourselves as the health care sector,” says Dr. Panduka Karunanayake, Senior Lecturer from the Department of Clinical Medicine, University of Colombo.

The purpose of this research project between researchers from several local institutions (Medical Research Institute and Base Hospital Elpitiya under the Ministry of Health, and University of Peradeniya and University of Colombo) and Japan (National Institute of Infectious Diseases in Tokyo, and Graduate School of Infectious Diseases and Institute of Genetic Medicine of Hokkaido University) had been to identify the serogroups and genetic groups of Leptospira organisms that are found here at home. “This knowledge is important to better understand the new clinical manifestations for their early diagnosis and treatment, and to know the carrier animal for specific control measures, as this disease is carried by animals,” explains Dr. Karunanayake.

A laborious process, first, the organisms need to be ‘isolated’ (grown) in artificial culture, and thereafter artificially ‘maintained’ (kept alive) in culture media. This needs specialized laboratories with biosafety measures. The National Reference Laboratory (NRL) for Leptospirosis at the MRI offers this service to hospitals routinely. “Organisms were isolated from blood of patients affected by the 2015-2017 leptospirosis outbreak from the Base Hospital in Elpitiya and animal kidney tissue from Kandy. Once they were successfully grown and maintained in culture, they were sent to Japan for the genetic characterization which was done for us by the Japanese collaborator (Dr. Nobuo Koizumi, National Institute of Infectious Diseases (NIID), Japan),” says Dr Karunanayake.

The genetic characterization and serogroup analyses were done in NIID, Japan which demonstrated that these strains belonged to three genetically-defined species. “When their genotypic strains were analyzed, it was found that the isolates belong to 15 different strains, of which six were not described before in the world literature, hence treated as ‘novel genotypes’. Of these, three were from patients treated at the Base Hospital in Elpitiya. They were causing multiple complications such as kidney, liver, heart and lung involvement and septic shock. However, all of these patients survived,” says Dr. Karunanayake.

Although leptospirosis had been prevalent in our country since the 1950s, it has been changing its nature in the last decade. “While the number of cases are increasing alarmingly, the clinical picture too is changing, with the identification of new and troublesome complications including pulmonary haemorrhage, pancreatic involvement, heart involvement, community-acquired sepsis, etc.” he said. The disease is also affecting a wider group of people, such as those living in urban areas and people exposed only briefly to stagnant waters or floods.

“After 40 years since Dr. K. Nityananda’s work in the 1960s and 1970s at the NRL, we have been able to introduce new strains for the first time to the world literature on leptospirosis, again from the NRL,” observes Dr. Lilani Karunanayake, Consultant Clinical Microbiologist and Head/National Reference Laboratory for Leptospirosis at the Medical Research Institute. The emergence of new genotypes, as she points out, imply the importance of strict quarantine of imported cattle as well as other imported domestic animals that are potential reservoirs of leptospirosis. “Unintentional introduction of rodent reservoirs through improper garbage disposal and the existence of unidentified reservoir animals in the country also call for attention,” says the senior microbiologist who further says that new knowledge from this study will be valuable in future research for patient management and specifically-targeted control approaches for reservoir hosts in the prevention and control of leptospirosis in Sri Lanka. She extended her thanks to the clinicians from various hospitals who sent in samples, which enabled these discoveries in the best interest of people.

The National Reference Laboratory (NRL) for Leptospirosis at the MRI which serves as the central referral laboratory in the country performs certain specific leptospirosis tests, samples for which are sent from hospitals island-wide. “Although certain tests could be performed at peripheral levels, some of the advanced cases need to be referred to the central lab,” notes Dr. Karunanayake, adding that the Teaching Hospitals at regional level should be strengthened with testing facilities for early detection.

Non-specific features of the patients such as fever, headaches, body aches, diarrhea which could mimic other conditions such as dengue has rendered early detection of leptospirosis very challenging, says Dr. Sajiv De Silva, Consultant Physician, Base Hospital, Balapitiya. “Hence kidney complications and the lung involvement are two specific features we give attention to in our investigations which often require intensive care. We also take serious account of the patient’s exposure to paddy fields and muddy water. In the Elpitiya patient cluster which we took as our research sample, the kidney complications and pulmonary haemorrhage were very severe which enabled us to add the new genotypes from this cluster to the world literature on leptospirosis.” He further remarks that these genotypes are more virulent than those found in the Western Province. Similar to the cluster in Elpitiya, more recent samples from patients in Galle, Balapitiya and Udugama in the Southern Province have reflected more severe complications, particularly lung and kidney complications which trigger rapid deterioration of the patient.

Patient demographic changes are also significant as the research reveals, points out Dr. De Silva. “Apart from farmers and miners who were traditionally identified as the most vulnerable to the disease, today we find a considerable percentage of young patients who had contacted it by merely visiting a paddy field or bathing in a river.” Diagnosing leptospirosis has become a “dilemma” for the physicians at the peripheral level, observes the Consultant who adds that, blurring lines between dengue and leptospirosis makes it more challenging. “In both situations platelets will drop. However in the treatment of dengue, while fluids need to be administered proportionate to the urine output, in the case of leptospirosis, fluids cannot be administered to mitigate pulmonary hemorrhage.”

Reiterating on the urgency of seeking early hospital care, the physician notes, “the earlier they come, faster the laboratory diagnosis would be.” Although clinical diagnosis of leptospirosis was not possible in the first few days of symptoms, today the availability of the PCR test (free in the state health sector) makes this possible, he adds. The toll the disease takes on families and the national health budget cannot be undermined. In a bid to create awareness on prevention of it by promoting safety footwear and early detection among the communities at rural level, a programme is now in place facilitated by the MOHs and PHIs says Dr. De Silva.

The breakthrough research is also a reflection of the validity of the ‘One Health’ concept where collaborative health efforts of multiple disciplines working nationally and globally can attain optimal health for people, animals and the environment, observes Dr. Chandika Gamage, Veterinarian and Senior Lecturer from the Department of Microbiology, Faculty of Medicine, University of Peradeniya. “Pathogens isolated from rats and humans in a molecular study during the research had revealed same genetic strain types which have enabled us to enlarge our knowledge on leptospirosis,” explains Dr. Gamage.

Although traditionally leptospirosis had been considered a disease spread by rats (‘natural reservoirs’), it is now becoming clear that there are other animals, such as cattle, that harbour the bacteria and spread it, points out Dr. Gamage. The research had further thrown light on dairy cattle as a potent reservoir of the disease. They are often grazed on grassland infected with rat urine and can can set off a vicious cycle, says the Veterinarian. “One excretion of cattle urine can be an amplifier pathogen of leptospirosis.”

Concurrent studies in humans, animals and environmental sampling can determine how these interact to bring about disease in humans which validates the One Health approach, says the Veterinarian. Furthermore, diverse sero groups were found in this study to cause both human disease and that present in animals like cattle and buffalo, pointing towards the need for new preventive strategies to control human leptospirosis in Sri Lanka, he says. Research will also be extended to the study of domestic animals such as dogs and cats as potential carriers of the disease.

“It is imperative that we contribute to the control of leptospirosis through One Health perspective through preventive measures such as safe garbage disposal which would otherwise become breeding grounds for rats, vaccination of cats and dogs, use of preventive footwear in agrarian and other outdoor pursuits. While a patient infected with the disease may be treated, unless we adopt a holistic approach towards prevention, the environment around us could still be a catalyst of the disease hindering the control or even elimination of the disease.”