Leptospirosis: Butantan test detects disease early – 01/11/2024 – Health

Researchers at the Butantan Institute developed a new protein in the laboratory for diagnosing leptospirosis in the initial stage of the disease. The test is superior to MAT (microagglutination), which is recommended by the WHO (World Health Organization).

The test — created by the group of researcher Ana Lucia Tabet Oller Nascimento, from the Butantan Vaccine Development Laboratory — detected leptospirosis early in more than 70% of patients who had obtained false negative results in the first days of symptoms.

For the study, a recombinant chimeric protein was used, synthetically constructed and called rChi2, composed of fragments of the ten main surface proteins of the bacteria. Leptospira.

The protein was recognized by antibodies both at the beginning of the disease, when the MAT was negative, and in the recovery phase, in 75% and 82% of the samples, respectively.

“In conventional diagnosis, the patient’s serum is brought into contact with Leptospires live organisms that agglutinate in the presence of antibodies [resultado positivo]. The problem is that it takes more than ten days for the individual to produce these agglutinating antibodies, making early identification of the disease difficult”, explains the first author of the research Luis Guilherme Virgílio Fernandes, a biotechnologist with a doctorate and post-doctorate at Butantan.

“My doctoral and postdoctoral advisor, Luis Guilherme, assembled a protein by taking different pieces of other proteins already known in the literature and generated a new one. We tested this protein with the sera of patients diagnosed with leptospirosis. The technology used was the ELISA [que avalia a presença de anticorpos no soro de pacientes por meio da reação com antígenos]”, explains Nascimento.

It is not possible to say how long after infection with the bacteria the protein identified the disease in patients because the researchers did not have access to the medical records.

“What we know is that while the conventional test is negative, we can already be positive”, says the researcher. By diagnosing the disease early, it is possible to treat it early and improve the patient’s quality of life.

The conventional test allows diagnosis 7 to 14 days after infection, according to the literature, depending on each person’s immune response. “The sequence is like this. The person feels bad, goes to the PS. There the serum is collected, which goes to the reference laboratory, the Adolfo Lutz Institute. It is sent to serology to see if they have malaria, dengue fever, leptospirosis. Suppose everything was negative. This patient leaves, but does not recover. After a while, he returns to the hospital. Another serology is performed. And then, he is often diagnosed with leptospirosis.

It is important to highlight that the standard test is an important tool for public health and epidemiology, and should continue to be applied. “It contains cultures of bacteria Leptospira of different serotypes, helping to identify which type is in greater circulation or causing epidemics. To the Leptospires pathogenic [que causam doença] they have more than 200 serotypes”, explains the researcher.

The serum samples used in the study were obtained from partner researchers at the Adolfo Lutz Institute and the Fiocruz National Reference Laboratory for Leptospirosis (Fundação Oswaldo Cruz).

The new diagnosis showed 99% specificity for leptospirosis and did not cross-react with other infectious diseases such as dengue, malaria, HIV and Chagas disease.

For the research, 142 samples were used. Ana Lucia said that the protein is not ready to be used and that more studies are needed.

The Butantan Institute has already requested the patent. “The whole world has been looking for an earlier diagnosis and this test is better than MAC, simpler and detects the disease faster”, says the researcher.

The idea, in the future, is to develop a rapid test (similar to the Covid test found in pharmacies), using the same chimeric protein.

What is leptospirosis?
Infectious disease caused by bacteria Leptospira interrogans. It is very present in dogs, rats, pigs, cows and goats. The bacteria lodges in the kidneys of these animals, which eliminate it through urine.

How does the transmission take place?
Through the urine of infected animals, food that had contact with water contaminated by the bacteria and was not properly sanitized, especially fruits and vegetables, and in floods.

How does contagion occur?
Through the consumption of poorly sanitized food and contact with the urine of infected animals, which can occur in flood water. Bruises are beneficial, but the bacteria penetrates the skin even when there are no injuries.

“A raised skin on the foot or a poorly cut nail is enough for the bacteria to penetrate. We are talking about bacteria that are microscopic, so there is no need for a large wound”, says Lina Paola Miranda Ruiz Rodrigues, infectious disease specialist at BP – A Beneficência Portuguesa de São Paulo.

What are the symptoms of leptospirosis?
The disease can be asymptomatic. When there are symptoms, the patient has body and head pain, high fever, 38.5ºC, 39ºC, diarrhea, nausea, vomiting, calf pain, conjunctivitis (or reddened eyes). Because it is confused with a more common infectious disease, care is often delayed.

In severe forms, the manifestation of leptospirosis is Weil syndrome. “The patient has jaundice, pulmonary hemorrhage and kidney failure, he stops urinating. He becomes drowsy, confused and needs to be cared for in an ICU”, explains the doctor.

How long do symptoms appear after contamination?
The incubation period — the time interval between transmission of the infection and the onset of symptoms — can vary from 1 to 30 days and normally occurs between 7 and 14 days after exposure to risk situations.

“Sometimes, the patient even forgets that he had contact with flood water, that he crossed a flooded street and that 7 to 14 days have already passed. He does not make the connection with this episode.”

“It is important to recommend to people that, during this rainy season, if they cross a flooded street and are wearing sandals, flip-flops, or if they are going to wash their yard with flood water, that they wash their feet with clean water and soap immediately. If they are in the street, buy a bottle of water to wash quickly and when you get home, repeat with soap and water”, advises Rodrigues.

“If you are cleaning a flooded area, use rubber boots”, he concludes.

According to the expert, it is also important to vaccinate dogs so that they do not get sick and bring leptospirosis into the home.

From January 1, 2023 to January 4, 2024, the city of São Paulo recorded 179 cases of leptospirosis with 18 deaths, according to the epidemiological bulletin from the Municipal Health Department. The number of infected people is lower than that confirmed in 2022 (201), but the number of deaths exceeded (20).