Diseases transmitted from animals to people are considered zoonoses. Diseases such as Rocky Mountain spotted fever, Q fever, hantaviruses and arenaviruses may present initial clinical pictures common to other infections. The similarity between the symptoms, which include fever, headache or body ache and malaise, contributes to making the proper diagnosis of infections difficult.
Researchers from the Oswaldo Cruz Foundation (Fiocruz) warn that, in the midst of the Covid-19 pandemic, zoonoses have been forgotten at the time of diagnosis of patients, leading to delays in detection and increasing the risks of serious conditions and deaths.
In an article published in the scientific journal The Lancet Regional Health – Americas, researchers from the Oswaldo Cruz Institute (IOC/Fiocruz) emphasize that awareness is essential to prevent deaths.
“Last year, a patient with hantavirus was diagnosed with Covid-19 in Rio Grande do Sul and ended up dying. This year, in an outbreak of Rocky Mountain spotted fever with five cases in Rio de Janeiro, two patients were diagnosed with Covid-19 and died because the Rocky Mountain spotted fever treatment was not started in time. Even in a pandemic period, it is necessary to take into account these zoonotic pathogens that circulate in Brazil, but that are made invisible”, said researcher Elba Lemos, from Fiocruz, in a statement.
Rocky Mountain spotted fever and hantaviruses are the most frequent diseases reported in the article. Between 2010 and 2020, more than 1,900 cases of spotted fever were confirmed in Brazil, with 679 deaths, which means a case fatality rate of 35%. In the same period, 996 hantavirus infections were confirmed, with 414 deaths, which corresponds to a case fatality rate of 41%.
“Spotted fever can be cured with an inexpensive antibiotic. However, if the drug is not given early in the infection, the bacteria do a lot of damage to the blood vessels and the damage becomes irreversible. In hantavirus, there is no specific treatment against the virus, but the diagnosis is important to offer adequate support to patients”, explains Elba.
Diseases associated with rains and floods
The summer period, marked by the combination of heavy rains and intense heat, favors the transmission of diseases. In addition to the direct risks to the lives of populations, due to the great force of the waters and landslides, the flooding favors the transmission of leptospirosis, diphtheria, cholera, typhoid fever, hepatitis A, giardiasis, amoebiasis, diarrheal gastroenteritis and schistosomiasis.
In the article, Fiocruz researchers recommend increasing care after the tragedy caused by the rains in Petrópolis, in the mountainous region of Rio de Janeiro, due to the risks of transmission of zoonoses.
“Animals rescued after the rains may have ticks, which are transmitters of the bacteria Rickettsia rickettsii, which causes spotted fever. It is very important to be careful at the time of rescue and treat the animals with ticks”, says the scientist. According to her, in 2011, when municipalities in the Serrana Region were devastated by heavy rains, five people died of spotted fever after dealing with rescued dogs.
Leptospirosis, caused by the bacteria Leptospira, shed in the urine of rats, can also infect people who come into contact with floodwater. “Depending on the history reported by the patient, these diseases need to be considered at the time of differential diagnosis in cases with nonspecific clinical manifestations, such as fever”, adds Elba.
Surveillance
As they are transmitted from animals to people, zoonoses present specific risk contexts, which favor human exposure to microorganisms. The researchers point to the importance of surveillance for knowledge of the areas of circulation of disease-causing agents and animals that act as reservoirs, with the aim of facilitating the early diagnosis of infections.
With the low rate of diagnoses, the impact of some zoonoses can be underestimated by managers and health authorities, warn the researchers. “We need to map the places where zoonotic infectious agents are present so that the health system is prepared. That’s why surveillance and research are so important. It is knowledge for action”, highlights Elba.
Rocky Mountain spotted fever
Rocky Mountain spotted fever is an infectious disease that causes an acute fever. The disease can present asymptomatically to more severe cases, with high chances of death.
In Brazil, it is caused by a bacterium called Rickettsia rickettsii, transmitted by the tick of the species Amblyomma cajennense, popularly known as the star tick. There are over 20 species of Rickettsia that can cause Rocky Mountain spotted fever worldwide.
Hantaviruses
Hantaviruses are caused by several viruses of the Hantaviridae family, found mainly in wild rodents. Infection happens when people inhale the viruses present in the urine and feces of these animals. Agricultural workers can contract the infection in fields or grain storage sheds, where rodents forage for food.
The infection is recorded in all regions of Brazil, with notifications in 15 states and the Federal District. The environmental imbalance, which favors contact between humans and rodents, contributes to the maintenance of cases of the disease.
Initial clinical manifestations include fever, headache, joint, back or belly pain, and gastrointestinal disorders. Patients can develop a cardiopulmonary syndrome, with shortness of breath, rapid breathing and heartbeat, coughing, and a drop in blood pressure. In the absence of specific medication, treatment is done in a personalized way with the aim of relieving symptoms.
Arenaviruses
Arenaviruses are microorganisms found in rodents that can cause neurological changes and hemorrhagic fever in people.
Causer of Brazilian hemorrhagic fever, the Sabiá virus re-emerged in 2020 after about 20 years without records, causing infection in a man, who died from the disease. The case was registered in São Paulo, the same state where the virus was first identified, in 1994. The disease would have been contracted during a trip to the city of Eldorado, in the south of the state.
In addition to the Sabiá virus, four arenaviruses are known to cause human infection in South America. Like hantaviruses, arenaviruses are transmitted through aerosols shed from rodent urine and feces. By presenting a picture similar to severe dengue and yellow fever, the researchers say that there may be an underreporting of arenaviruses.
Q fever
Q fever, caused by the bacteria Coxiella burnettiis mainly transmitted in rural areas by inhalation or direct contact with secretions from infected animals, including milk, feces, urine, vaginal mucus or semen from cattle, sheep, goats, dogs, cats and other domestic mammals.
Most of the time, the infection is asymptomatic or has flu-like symptoms. However, some patients may develop severe conditions, such as pneumonia or endocarditis. The infection is treated with antibiotics.
bartonelosis
Cat-scratch disease is the best-known form of bartonellosis, an infection caused by bacteria of the genus Bartonella. Animals infected by the bacteria Bartonella henselae they can transmit it through scratches or bites. Fleas and ticks present in these animals are also vectors of the disease.
According to Fiocruz researchers, the diversity of manifestations of the disease makes diagnosis difficult. In addition to asymptomatic cases, bartonellosis can cause inflammation at the wound site, swelling in the lymph nodes and fever to serious conditions that affect the nerves and heart.
Source: CNN Brasil
