University of São Paulo: Research shows urgency in controlling bovine tuberculosis among wild animals

Brazil does not have specific legislation for the control of bovine tuberculosis in wild animals. However, these animals are susceptible to the disease and can become potential reservoirs for maintaining the disease, in addition to being a threat to endangered wild species. A survey by the Institute of Biomedical Sciences (ICB) at USP and three other institutions made it possible to understand the extent of the outbreak of bovine tuberculosis in wild animals at the Pampas Safari theme park, which operated in the municipality of Gravataí, in Rio Grande do Sul (RS), until 2017. The results serve as an alert for the need for a disease control program among these animals, whether in nature, in zoos or parks.

Developed in partnership with the Brazilian Agricultural Research Corporation (Embrapa), the Secretary of Agriculture, Livestock and Rural Development of Rio Grande do Sul (SEAPDR) and the Faculty of Veterinary Medicine and Animal Science (FMVZ) at USP, the research shows that the The disease was probably transmitted from oxen to at least 16 different species of animals, mostly deer, such as rusa unicolor, fallow deer and red deer. Three genetic variants of the disease-causing bacteria, Mycobacterium bovis , were also found .

The work, published in the journal Transboundary and Emerging Diseases , is the first study to show the prevalence of the disease in an environment that is not fully enclosed, such as a zoo.

“These numbers, both for variants and species of infected animals, are probably higher because there is no specific diagnostic test for bovine tuberculosis in wild animals,” says Daiane Lima, a researcher at Embrapa’s Animal Research Group and first author of the paper. study. “The problem was certainly much bigger than reported; we only took a fragment of what happened there, with tests on dead animals”, adds Flabio Ribeiro de Araújo, researcher at Embrapa’s Animal Research Group.

Bovine tuberculosis is an infectious disease that affects domestic and wild animals and humans . Transmission to humans occurs mainly by ingestion (raw unpasteurized milk, in most cases) or inhalation of aerosols in close contact with animals with the disease. In the case of animals, there is no treatment or vaccines, only measures to prevent and contain the spread of outbreaks, which involve the slaughter of the animal after diagnosis. The disease, of a chronic nature, causes economic losses for beef and dairy cattle, in addition to sanitary barriers.

“Worldwide, the notification of bovine tuberculosis to the World Organization for Animal Health (OIE) is mandatory. But in Brazil, cases in wild animals do not need to be reported by the Ministry of Agriculture, Livestock and Supply. We want this work to help correct this legal vacuum, given that the Ministry’s National Bovine Tuberculosis Control Program does not take wild animals into account”, says Ana Márcia Sá Guimarães, coordinator of the Laboratory for Applied Research to Mycobacteria at the ICB , where part of the tests was carried out.

Diagnosis and sequencing

In the research, samples of material from sacrificed animals were analyzed, collected between 2003 and 2018. In addition to samples of llamas that died, samples from the deer diagnosis performed by the SEAPDR veterinary team were also included, following guidelines of researchers and the diagnostic protocol of the US Department of Agriculture (USDA), USA, which also took care of the euthanasia of clinically diagnosed animals.

Over the years, samples from these animals were sent to Embrapa and FMVZ, which were responsible for carrying out the diagnosis through bacterial culture and the positive samples were submitted to genomic sequencing. Thus, it was possible to understand whether there was transmission between the animals and whether there were multiple introductions of the bacterium over time.

At the ICB, the samples underwent bioinformatics analyses, where all the DNAs were captured and compared to assess whether there were mutations in the bacterium. “We evaluated the samples to see which genomes would be closer to each other and which would be further apart and which could be of different origins”, explains Cristina Zimpel, a doctoral student at the institute. “With the study, we were able to show, through the three variants found, that there were at least three different introductions of the disease in the park during the period”, adds Guimarães.

Everything indicates that the outbreak in the Pampas Safari was due to two factors: inadequate feeding of these animals, which compromised their immunity and ability to fight the pathogen, and the overcrowding of animals of different species in a small space.

“The deer that became infected were euthanized. But as the Pampas Safari is a private place and the farm where it was located still exists, it is not possible to say that the outbreak is over”, recalls Guimarães. The researchers estimate that the disease may have spread to other states, as there was intense activity in the park of selling live animals to other farms.

case tracking

The group seeks new partnerships to analyze other cases of bovine tuberculosis transmission in wild animals. “We want to talk to people responsible for zoos in different regions of the country to see if they have already witnessed cases of the disease and what has been done, and then analyze them in order to have a real idea of ​​its prevalence in Brazil”, says Guimarães. At the same time, the group will continue to carry out studies on the transmission and diagnosis of tuberculosis in cattle and buffaloes.

In the researchers’ assessment, a disease control program aimed at wild animals is essential, with mandatory notification of cases and the establishment of clear diagnostic criteria. Without these measures, the risk of spreading the disease in Brazil, through wild animals, tends to increase.

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