Credit: Camilo Tomckowiack Jeldres, Bayer AG
Because leptospirosis can also cause multiple organ infections in humans, Camilo Tomckowiack Jeldres has taken on the challenge of deciphering this disease and making it easier to diagnose and cure.
What is leptospirosis, and why is it a risk to human and animal health?
Leptospirosis is a bacterial disease that is transmitted between animals and can also be transmitted to humans, which makes it zoonotic. The disease lodges in the kidneys of infected animals, where it proliferates and disseminates through the urine, this being the infection’s main route of horizontal transmission.
Leptospirosis is acquired through ingestion of contaminated water or exposure to urine from infected animals. While the role of rats and mice as natural carriers of leptospira is well known, the role of domestic ruminants as a reservoir has also been discovered. Besides infected animals being a risk to herd health, farm workers that have close daily contact also puts them at risk of acquiring the disease. Although leptospirosis in dairy herds is mainly asymptomatic, spontaneous abortion may occur as a consequence of infectious status, resulting in significant financial losses for farmers and the dairy industry.
In Chile, the rate of spontaneous abortion among dairy cattle is estimated at 10 percent, with leptospirosis one of the more important causes. The seroprevalence of this disease in Chile is 75 percent of dairy herds. In contrast, human infections initially manifest with flu-like symptoms, and, as such, are often under-diagnosed. In most cases, the human immune system is able to resolve the infection. However, the disease can develop into a multi-organ infection, with mortality rates of up to seven percent of registered cases.
|Credit: Camilo Tomckowiack Jeldres, Bayer AG||
Leptospirosis, also known as Weil’s disease, is a zoonotic disease caused by a bacterium called leptospira. This bacterium is more common in warm climates such as Australia, Africa, Southeast Asia, Central and South America, and the Caribbean.
Leptospirosis: A Zoonotic Disease
A video interview
Is leptospirosis specific to Chile or a general challenge in Latin America, and possibly other tropical countries, around the world?
Leptospirosis is, in fact, classified as the zoonotic disease with the greatest global distribution. It is a major problem in tropical countries or in areas affected by flooding, as it spreads more easily through water. In Chile, leptospirosis is considered an emerging disease, and was incorporated into the Ministry of Health Decree No. 158 of Obligatory Declaration Diseases in July 2002.
Currently, 80 percent of the nation’s milk is produced in a high rainfall area, which is a characteristic that aids the prevalence of leptospirosis in dairy cattle and the environment.
The tropical countries of Latin America, such as Brazil, Africa and Southeast Asia, such as Thailand, recognize this disease as a public health issue. Since leptospirosis is generally confused with diseases such as influenza, malaria, dengue, yellow fever or hantavirus, it’s a challenge to reduce its impact on the population.
The Burden of Leptospirosis
With an estimated one million confirmed human cases each year, and a mortality rate of 60,000 cases annually, leptospirosis is one of the main causes of disease and mortality (according to a study published in the journal PLOS Neglected Tropical Diseases). As climate change affects global temperatures and urbanization accelerates, the prevalence of leptospirosis is likely to increase in the future.
Leptospirosis also has an impact on the health and well-being of farm animals and the people who work with them – the disease is disruptive, as it causes spontaneous abortions in dairy herds and equines, and it impacts the productivity of pigs. It has also been attributed to thousands of canine deaths.
What is the current state of research regarding prevention and cures for this disease?
In humans, in the early stages, leptospirosis responds to antibiotic treatment. However, it becomes more complex in the face of multi-organ infection, so the key is a correct initial diagnosis. But the biology of leptospira is quite special: These bacteria present a great variety of serovars, with more than 250 serovars grouped in 24 serogroups. Therefore, they have a high capacity to generate different antibody responses.
It is difficult to generate a serological diagnosis, since it is only possible to recognize a single serovar type, and it’s necessary to have a pure culture of each one to perform the microscopic agglutination test (MAT), a reference test for this disease. This means that diagnosis depends on analysis in the laboratory by specialized professionals.
According to WHO, only one-in-eight cases of human leptospirosis are correctly diagnosed. In cattle, this disease is easy to treat with antibiotics. However, the main difficulty is the identification of animals with an active infection.
In terms of prevention in animals, there are vaccines for dogs, pigs, and cattle. But again, the same challenge is due to the serovars: Each vaccine is based on dead bacteria from one to five serovars that are most relevant for the area or animal. Currently there is no universal vaccine for all pathogenic leptospira. And it is here where the greatest research efforts have been generated, since this is a scientific challenge.
What can be done to improve the situation of leptospirosis in the affected areas?
Based on my experience, I believe it is necessary to improve the diagnosis of this disease. The research group of the Laboratory of Infectious Diseases, of the Faculty of Veterinary Sciences of the Universidad Austral de Chile, where I do my Ph.D. studies in Veterinary Sciences, has undertaken research in this area in dairy cattle. The results suggest the identification and treatment of animals with an active infection status in order to decrease environmental shedding of this bacterium, and then to perform a preventive control by vaccination. But the reality in the herds is different.
Currently, a preventive diagnosis of this disease is not made. Almost all of the samples sent to the laboratory are from cows that have spontaneously aborted, and veterinarians want to identify leptospirosis as a cause, but not all cows that abort are analyzed. In contrast, a low number of samples from cows that abort is sent for analysis. In case of a positive result, vaccinations are reinforced, making vaccinations necessary three-to-four times a year.
And the current diagnosis method itself has disadvantages. Since it is a serological diagnosis, the vaccination causes cross reactions with the microscopic agglutination test, possibly resulting in false positives. The presence of antibodies indicates exposure to the pathogen, but not necessarily an active infection status. Also, the limited number of serovars used in the detection may result in an inaccurate diagnosis.
For this reason, we aim to improve the capacity of the diagnostic tests, as well as awareness among dairy producers, in order to develop better management plans and encourage preventive diagnosis.
|Credit: Camilo Tomckowiack Jeldres, Bayer AG||
How does the disease affect smallholder farming, and what are the economic effects?
In dairy herds without surveillance against this disease, spontaneous abortion rates of up to 40 percent have been recorded. Losses at this scale can severely impact a dairy farmer. Vaccination has helped to mitigate spontaneous abortion rates in Chile, but not to eradicate the infection in herds. Since vaccinating already infected animals has no beneficial effect, these animals will continue to shed high bacterial loads into the environment, thereby infecting other animals.
Researchers have recorded up to 1.5 years of shedding through urine. Due to the potential economic losses and the health risk for the workers handling infected animals, herds that maintain this infection over a time are a significant problem for farmers.
The agricultural and livestock service (SAG) of Chile indicates the control measures that should be taken against leptospirosis in larger and smaller animals. These measures should focus on the elimination of the animal reservoir and vaccination of domestic animals, effective control of rats, disinfection of contaminated workplaces and the prohibition of animals drinking from contaminated water. Vector control and environmental hygiene are fundamental to avoid contagion. In case of spontaneous abortions, these and their annexes must be eliminated to avoid contact with other animals.
It is necessary to encourage farmers to diagnose the health of their animals. In order to achieve this, an easy, practical and affordable diagnostic tool is needed.
How can leptospirosis
A video interview
Why are you involved in the fight against leptospirosis?
I live in Chile’s key milk producing region. While in university, I dedicated myself to science and to the study of infectious zoonotic diseases in animals. During this time, I came across leptospirosis and realized that it is an unattended disease. Due to its impact, there is need to gain more information about the characteristics of leptospirosis, the limitations of the diagnosis and vaccinations in order to illustrate its reach in dairy herds and its risks to farmers. At the same time, I have a keen interest in applied science and biotechnology and saw the need to develop new diagnostic tools, given the potential benefit they can offer.
What do you hope to achieve personally in the next five years to improve public health?
We are currently developing a project called “Lepto Alive,” which relates to the development of a rapid diagnosis test for leptospirosis that would offer greater accessibility and accuracy. The aim is to create a portable device, similar to a pregnancy test, which detects the presence of the bacteria directly in the urine, while also being able to detect all pathogenic leptospira without discriminating by serovar, and is compatible with vaccination.
This device will enable field veterinarians to identify animals with an active infection in a highly specific way, with results available just five minutes after testing. This process would reduce the need for a laboratory or specialized workers. We believe that with the practicality and affordability of such a device, veterinarians will be able to better detect and diagnose the disease.
For starters, they will be able to determine if leptospirosis is a cause of a cow’s spontaneous abortion. In the long term, the device will enable preventive diagnoses. After being validated in dairy herds, it will have the capacity to diagnose leptospirosis in pigs, horses, dogs and even in humans. The device has great potential to benefit public health, especially in areas where people have been exposed to floods and have flu-like symptoms. In countries like India, for example, the incidence of leptospirosis after a flood is high.
|Credit: Camilo Tomckowiack Jeldres, Bayer AG||
The “Lepto Alive” research project aims both to simplify diagnosis and to sensitize dairy farmers towards better management plans and medical treatment in order to prevent infections.
How can veterinary medicine contribute to public health?
There is a close relationship between the pathogens, the host animals and the environment. In the case of leptospirosis, controlling this disease in cattle contributes to their health and well-being, reduces the risk of transmission to farm workers, as well as diminishes the negative economic effects on the dairy industry.
”We need to work together from the medical,
veterinary and farming sides to effectively fight against
zoonotic and neglected tropical diseases.
Bayer, for example, supports farmers by sharing its expertise
on enhancing farm and herd management practices
that put animal well-being and health at the forefront.”
Prof. Dr. Norbert Mencke,
Global Head of Policy & Stakeholder Affairs
Animal Health at Bayer
 Salgado, M., Otto, B., Sandoval, E., Reinhardt, G., & Boqvist, S. (2014)
 Costa, F., Hagan, J. E., Calcagno, J., Kane, M., Torgerson, P., Martinez-Silveira, M. S., ... & Ko, A. I. (2015). Global morbidity and mortality of leptospirosis: a systematic review. PLoS neglected tropical diseases, 9(9), e0003898)
 Picardeau, M. (2015). Leptospirosis: updating the global picture of an emerging neglected disease. PLoS neglected tropical diseases, 9(9), e0004039
Gädicke, P., & Monti, G. (2008). Aspectos epidemiológicos y de análisis del síndrome de aborto bovino. Archivos de medicina veterinaria, 40(3), 223-234)