Maíra Menezes (Oswaldo Cruz Institute/Fiocruz)
Diseases transmitted from animals to humans, such as spotted fever, Q fever, hantavirus diseases, and arenavirus diseases present early clinical symptoms that are similar to those of other infections, including fever, headache, or aches in the body, and malaise. Amidst an epidemic, when all eyes are focused on diseases that are circulating widely, such as dengue fever or Covid-19, these zoonoses are often forgotten when diagnosing a patient. This leads to delayed identification, therefore increasing the risk of severe disease and death.
Researchers from Hantavirus and Rickettsia Laboratory highlights that raising awareness is crucial to prevent deaths (Image: Josue Damacena)
The alert regarding the circulation of these “invisible zoonotic diseases” is in a paper recently published on The Lancet Regional Health – Americas by researchers of the Oswaldo Cruz Institute (IOC/Fiocruz). Elba Lemos, the author of the publication and the head of the Hantavirus and Rickettsia Laboratory of IOC/Fiocruz, highlights that raising awareness is crucial to prevent deaths.
“Last year, a patient with hantavirus was diagnosed with COVID-19 in the state of Rio Grande do Sul and eventually died. This year, in an outbreak of spotted fever with five cases in Rio de Janeiro, two patients were diagnosed with COVID-19 and died because the treatment against spotted fever was not used in time. Even during a pandemic, it is necessary to take into account these zoonotic pathogens that circulate in Brazil, but that tends to be overlooked”, the researcher says.
Among the diseases highlighted in the paper, spotted fever and hantavirus diseases are the most common ones. Although they do not cause epidemics, these diseases have a very significant impact on public health, especially due to the high rate of deaths. Between 2010 and 2020, more than 1.9 thousand cases of spotted fever were confirmed in Brazil, with 679 deaths - a lethality rate of 35%. In the same period, 996 infections by hantavirus were confirmed, with 414 deaths, corresponding to a lethality rate of 41%.
“Spotted fever can be cured with cheap antibiotics. But if it is not administered early in the infection, the bacteria wreak havoc in blood vessels and damage becomes irreversible. As for the hantavirus, there is no specific treatment against it, but diagnosing it is important so patients can receive adequate support. For instance, hydration, which is indicated for dengue fever, can be harmful in these cases, worsening pulmonary lesions”, says Lemos.
Risk after floods
Considering the high transmission rates of zoonosis after the tragedy caused by intense rain in Petrópolis, in the highlands of the state of Rio de Janeiro, increased attention is a must. “Animals rescued after the rains may be carrying ticks, which transmit Rickettsia rickettsii, the bacteria that causes spotted fever. It is very important to be careful during rescue and to treat the animals with a tick pesticide”, she says.
Leme also highlights that other zoonoses are associated with heavy rains, especially leptospirosis, caused by the Leptospira bacteria eliminated in rat’s urine. It can infect people that come into contact with floodwater.
As they are transmitted from animals to humans, zoonoses present specific risk contexts that result in human exposure to the microorganisms. This means that not only health professionals must be warned, but that it is also crucial to know the areas in which pathogens circulate and the animals that serve as reservoirs, to facilitate the early diagnosis of these infections.
In the paper, the authors highlight that as diagnoses of these infections are very low, the impact of some zoonoses is underestimated, making it even more important to carry out surveillance and research actions. To illustrate the impact of forgotten zoonoses, the paper describes recent outbreaks that have been investigated by the Hantavirus and Rickettsia Laboratory of IOC/Fiocruz, National Reference Laboratory for rickettsia diseases, and as Regional Reference for hantavirus for the Ministry of Health. In addition to spotted fever and hantavirus, the paper also addresses arenavirus diseases, Q fever, and bartonellosis.