Through mutations observed in the genome of the bacteria Mycobacterium bovis, the causal agent of bovine tuberculosis, scientists have been tracking the transmission of the disease in animals or in herds. The study has been conducted by researchers from Embrapa Beef Cattle (Campo Grande, MS), in a project funded by the National Council of Scientific and Technological Development (CNPq) and approved by the Mato Grosso do Sul State Foundation of Support to the Development of Education, Science and Technology (Fundect). This is the first result of the newly-initiated research, which is due to last two years. “We observed that farms that were close or that had traded animals would have genetically identical Mycobacterium bovis isolates. This allowed us to advance in the knowledge about the relationship between genotypes and spatial distribution of M. bovis strains", reports the immunologist Flábio Ribeiro de Araújo, a researcher at Embrapa. He stresses that this knowledge is important for studies on the maintenance and dissemination of foci of bovine tuberculosis, which are essential for the success of measures to eradicate the disease. "Potential users of the methodology to track bovine tuberculosis foci based on mutations in a single location include the Ministry of Agriculture's National Program of Tuberculosis Control and Eradication and other state health monitoring agencies", he anticipates. Araújo comments that the experiments performed in animals in Rio Grande do Sul can be the basis for other states and regions. "We sequenced isolates from bovine tissue cultures obtained by veterinarian services in that state in six rural properties", he reports. Each bovine isolate is accompanied by data on the location, animal origin, previous movements, results of diagnoses through intradermal tests (comparative cervical test), serology, tissue culture and nested-PCR. The scientist says that the next step will be to statistically work out the correlation between physical distance between the properties and the number of identical mutations. This is one of the goals of PhD candidate Rudielle Andrade, from the program of Veterinarian Sciences of the Federal University of Mato Grosso do Sul (UFMS), and advised by Araújo. Andrade conducted training in the area at the Sanger Institute, in the United Kingdom.. Monitoring the bacteria in humans Another frontline of work has been developed by researchers from institutions North of the country (in the states of Amazonas and Pará). They work with the sequencing of isolates from those regions with an original detail: focus on humans. "If we find M. bovis in humans, we will correlate how similar the isolates are in comparison with the bovine ones found the region. If this is confirmed, it will be the first description of zoonotic tuberculosis in Brazil, which represents a lot for the studies", Araújo stresses. These pioneering tests are conducted in Manaus' Central Public Health Laboratory (Lacen) under the Amazon Health Monitoring Foundation (FVS-AM), a project partner. The studies are led by the researchers Paulo Alex Carneiro (Federal Institute of Amazonas - IFAM and the Michigan State University - MSU - Center for Comparative Epidemiology), John Kaneene (MSU), Haruo Takatani and Christian Barnadd (Amazonas Agricultural and Forest Defense Agency - ADAF) and Marlucia Garrido (FVS-AM). The research group also comprises experts from several institutions, such as Universidade Católica Dom Bosco (UCDB), the University of São Paulo (USP), and the Rio Grande do Sul state Secretariat of Livestock, Agriculture and Rural Development. Disease affects animals and humans Bovine tuberculosis is a chronic contagious disease caused by M. Bovis bacteria, which affects animals and humans. The animals it afflicts include bovines, buffaloes, goats, sheep, swines and wild animals like boars, for instance. "Tuberculosis is of mandatory notification and one of the most important diseases catalogued by the World Organisation for Animal Health (OIE). If there is an occurrence of the disease , OIE member countries are obliged to notify it, as it influences international trade", explains Araújo. "Brazil adhered to OIE policies because it has intense and significant trade and thus follows preestablished rules". The presence of tuberculosis in the farm entails the exclusion of the property from the list of product exports to some markets, and the researcher warns that the meat of an infected animal cannot be consumed, as it represents a health hazard. "The most common way it infects humans is through the consumption of raw milk or dairy from infected animals. The ingestion of uninspected meat is also a potential risk", he underscores. The Embrapa scientist reports that diagnosing the disease in animals is not easy, as it does not always present symptoms. However, infected animals can grow thinner or show respiratory problems. Araújo reports that the longer the animal is infected, the worse for it and for the property. "The disease progresses gradually and causes injuries in the lungs and lymphatic system. The fall in production is around 10% to 15%", he clarifies. "Tuberculosis is a commercial obstacle and an important disease, hence advanced studies like the ongoing ones are needed in order to learn about disease transmission, origin and dissemination in more detail and hence elaborate guidelines to control, fight and eradicate it," the researcher defends. Photo: iStock Translation: Mariana Medeiros