Rabies deaths in MG warn about vaccination in higher risk populations

After ten years without deaths from human rabies, Minas Gerais had three new deaths from the disease in the last month. The victims were children from an indigenous community in the region of Bertópolis, in the east of the state.

A fourth case of infection is investigated. The occurrences shed light on strategies to control the emergence of outbreaks in the most vulnerable populations.

“For those who work with rabies cases, the alert was already on. Our epidemiological situation requires attention because we have hematophagous bats [que se alimentam de sangue] that penetrate homes and can transmit the disease”, says José Geraldo Ribeiro, epidemiologist and professor emeritus at the Faculty of Medical Sciences of Minas Gerais​.

In Brazil, in 2020, two cases of the disease were recorded and, in 2021, there was only one diagnosis.

Rabies is transmitted through bites from domestic and wild animals such as bats and dogs. At first, the symptoms of the disease are mild and common, such as fever, dizziness and pain. However, the picture evolves and convulsions, delusions, coma and other signs can occur, even death – cases of recovery are rare.

“It’s an almost 100% fatal disease, but it can also be 100% preventable”, says Jacy Andrade, infectious disease specialist and professor at UFBA (Federal University of Bahia).

One of the forms of prevention is the vaccination of dogs and cats in campaigns organized by the Ministry of Health. With the increase in vaccination coverage, cases of the disease caused by these domestic animals have been falling in recent years.

But there were flaws in the application. In 2019, for example, the Ministry of Health reported that rabies vaccination was restricted to areas at greatest risk for the disease in the Northeast region (Maranhão, Ceará, Piauí and Rio Grande do Norte) and in states bordering Bolivia ( Mato Grosso do Sul, Mato Grosso, Rondônia and Acre).

In 2020, there were fewer applications because, according to the ministry, many municipalities chose not to carry out the vaccination campaign due to the Covid-19 pandemic.

human vaccination

With the decrease in rabies cases caused by dogs and cats, bats became the main direct transmitters to humans — a hypothesis investigated for the new cases in Minas Gerais. In 2018, an outbreak of 11 cases of rabies in the Amazon was also caused by bats.

“Rabies transmitted by bats has always existed, but it was more seen as a reservoir of the virus from nature that it transmitted to other animals. The importance of direct aggression by the bat was not so well understood”, explains Ribeiro. “In a region like South America, where you have reservoir blood-sucking bats, it will never be possible to completely eradicate the virus in nature,” he says.

In this scenario of greater relevance of wild animals for the spread, the systematic vaccination of populations that are at greater risk of being infected, such as professionals who work with the capture of bats or residents of regions that have records of the disease, gains importance.

According to Andrade, from UFBA, many workers are not even aware that they can receive this care. “Often, we only think about post-exposure [ao vírus]. Of course, this is important, but we need a pre-exposure culture,” explains the researcher.

When a person is exposed to the virus — when bitten by an animal, for example — they receive a treatment that can combine serum and vaccine, depending on the severity of the case. Ribeiro points out that, at times, the excess of vaccines applied outside the recommendation in post-exposure cases may have had a negative impact on the supply of doses for pre-exposure campaigns.

A recent change in national vaccination guidelines should change that scenario, he said.

According to data from the Ministry of Health, in the last nine years the average number of pre-exposure applications was approximately 15 thousand, while in the post-exposure period in which only the vaccine was used, it was 121 thousand.

Sought by the report, the folder said that “the pre-exposure prophylaxis scheme is indicated for people at risk of permanent exposure to the rabies virus, during occupational activities”, such as medicine professors and veterinary students.

The ministry was also asked whether pre-exposure doses are expected to have a lower number compared to vaccines given after accidents, but did not respond to this until the publication of the report.

The folder also says that it participates in a pilot project that seeks to subsidize vaccination strategies in populations that are at risk. The initiative follows the immunization of a riverside population in an area of ​​transmission of rabies by bats in the Amazon. The estimated completion date of the study was not reported.

For Ribeiro, the experience of applying a pre-exposure vaccine to the entire population of a locality “is unique in the world” and can be important for controlling the disease in more vulnerable places.

“There is a very small experiment and we have to see if this is really going to work because it has a whole population dynamic [como novas pessoas chegando a região e que inicialmente não estariam vacinadas]”, says the researcher.

In the case of Minas Gerais, until April 28, the State Health Department says that 982 of the 1,037 people living in the community in Bertópolis were vaccinated with the first anti-rabies dose and 802 with the second dose. The interval between application is seven days.

Animal rabies vaccine was also provided for the immunization of dogs and cats in the region, and the Environment Department says it analyzes bats in the area to understand how the rabies virus is circulating among wild animals.

collaborated Isac Godinhofrom Belo Horizonte