Brazil is facing an outbreak of Oropouche fever this year, according to the Ministry of Health. In total, there were more than 7 thousand cases in 21 states as of July 28.
Recently, the first two deaths caused by the disease and one fetal death caused by vertical transmission of the virus (when the pathogen passes from mother to fetus during pregnancy) were confirmed.
Eight cases of vertical transmission are under investigation, including occurrences of fetal death and congenital malformations, such as microcephaly.
The increase in Oropouche cases drew attention to an insect little known by most of the population: the Culicoides paraensis, popularly called maruim or sandfly.
Species insects Culicoides paraensis, popularly called maruim or sandfly. Photo: Ceratopogonidae Collection of IOC/Fiocruzi
Although the insect, which stands out for its small size, has not yet been captured and identified as being infected by the virus in this year's outbreak, since the 1980s the maruim has been identified as the main vector of Oropouche fever.
At the Oswaldo Cruz Institute (IOC/Fiocruz), the Ceratopogonidae Collection keeps a collection of around 10 thousand specimens of the maruin family, including the neotype of the C. paraensis, a specimen chosen by experts as a reference for studies of the vector.
Contributing to confronting the problem, researchers from the IOC recently developed a Technical Note to guide vector surveillance actions in response to demands from the Rio de Janeiro State Health Department (SES/RJ).
In an interview, the Collection's curator, Maria Luiza Felippe Bauer, and the deputy curator, Maria Clara Alves Santarém, discuss the insect's main characteristics. Check out the interview below and learn more about the maruim.
What is the origin of this insect and where is it found?
Maria Luiza: O Culicoides paraensis It is possibly an insect native to the Americas. It was described, for the first time, in Pará, in 1905, by Emilio Goeldi. The naming of the species refers to the state. Currently, it is found in most of the American continent, from the southern United States to Argentina. In Brazil, it is believed to be present in all states, despite only having been effectively registered in 15 states to date.
What are the main characteristics of this insect?
Maria Clara: All maruins are very small insects. They measure around 1,5 mm and can reach 3 mm. Another characteristic is the very painful bite. It is an insect that causes discomfort to the population when there is an infestation.
What kind of environment does he live in?
Maria Luiza: In general, C. paraensis lives in forests and rural areas, mainly where there are banana plantations. In the north of the country, the maruim is also found in urban areas. In cities in the Amazon region, urban areas are closer to wild areas and there is this urbanization of the vector. In some municipalities outside this region, we see maruins in urbanized areas close to the rural environment.
Maria Clara: Furthermore, recently we have evidence that the C. paraensis It has been found in some urban centers in the country, which still requires confirmation. Apparently, this is occurring in areas where there has been environmental change. However, it is important to say that, to date, maruim is not an urban vector, like Aedes.
Entomologists Maria Luiza Felippe Bauer (right) and Maria Clara Alves Santarém highlight the need to identify the insect's breeding sites to try to reduce the maruin infestation. Photo: Josué Damacena
Where do maruim breed?
Maria Clara: The female maruim looks for places with plenty of organic matter and humidity to lay her eggs. In forests, decomposing tree trunks, fruit peels fallen on the ground, bromeliads, stream banks, and foliage on the ground are the preferred locations. In banana plantations, she lays her eggs on the banana tree stump, the part of the stem that remains when the tree is cut down to harvest bananas. In urban areas, she can lay eggs in the backyard if there is any type of organic matter accumulated on the ground.
What is the maruim’s life cycle like?
Maria Luiza: The life cycle is similar to that of mosquitoes. In breeding areas, the eggs hatch releasing larvae that feed on organic matter. The larvae go through four stages of development, then become pupae, which do not feed and transform into the adult insect. Based on studies of Culicoides species that occur in Europe, the cycle takes about 30 days from egg to adult insect. However, there is no specific data on the development time of the C. paraensis.
How many eggs does the female lay?
Maria Clara: Studies on insects of the genus Culicoides indicate that females can lay 30 to 450 eggs per clutch, depending on the species and blood meal. But there is no specific information about C. paraensis.
The small size is a striking characteristic of the maruim, which measures around 1,5 mm. Photo: Ceratopogonidae Collection of IOC/Fiocruzi
Why do maruim bite?
Maira Luiza: Adult maruins, both males and females, feed on plant nectar. However, females of the Culicoides genus bite because they need blood to mature their eggs.
How far does the insect fly? Is there a more frequent time for bites?
Maria Clara: It tends to stay close to its breeding site. Its own flight is around 500 m. But, as the maruim is very light, it is propelled by the wind. So, depending on the wind speed, it can fly up to 2 km.
Maria Luiza: The peak of activity, when the maruins feed with greater intensity, is in the late afternoon. But this does not mean that they are prevented from biting in the morning or at noon, if that is the time when the human being or other animal is present in the environment.
What are the control strategies for this vector?
Maria Luiza: To control the vector population it is necessary to eliminate breeding sites. In the case of maruim, the ideal is to remove the substrate where it reproduces. For example, if it is the banana tree stump, the banana plantation must be managed. If we have a yard, we must clean the land, not leaving fallen leaves or fruit peels on the ground or other decomposing organic matter. This can reduce the proliferation of the insect in that location.
What is the recommendation for personal protection?
Maria Luiza: When possible, avoid areas with the greatest infestation and try not to expose yourself during the insect's peak hours, in the late afternoon. Wear a long-sleeved blouse, long pants and closed shoes. If a person needs to enter an infested area, it is recommended to apply body oil to the skin. As maruim is very light, it sticks to the oil and cannot bite. If there is an infestation near your home, close the windows during the vector's peak hours. We know that some of these measures are difficult to adopt, mainly because the period of greatest transmission of Oropouche fever is in the summer.
Is there any point in using repellent, insecticide or screen?
Maria Clara: No. Both from scientific literature and from our own experience, we know that repellents are not effective against maru. Insecticides also don't work. These are compounds developed against mosquitoes, such as Aedes and Culex, which are insects from a different family. As maruins cross the common screen, it is recommended to use fine mesh screens, like voile, which would be as effective as closing the windows.
Specialists from the Ceratopogonidae Collection have already described 91 new species of maruins. Photo: Josué Damacena
How did the transmission of Oropouche fever begin in Brazil?
Maria Luiza: The Oropouche virus was described in 1955, from a single patient who presented the disease in the Vega de Oropouche community, in Trinidad and Tobago, in the Caribbean. But, at that time, it was not given importance because it was an isolated case.
In 1961, the first urban epidemic of Oropouche was recorded, in Belém do Pará, which reached 11 thousand cases. In the following years, several epidemics occurred in different locations in Pará.
It is believed that the disease spread in the state following the construction of the Belém-Brasília Highway, which deforested areas of forest. The workers entered the forest, where the disease circulated in the wild, and became infected.
From the 80s onwards, epidemics began to occur in other northern states and other countries, such as Peru, Panama, Colombia, Ecuador and French Guiana. More recently, there have been records in Bolivia and Cuba.
It was probably human movement that spread the disease, because the population has always moved internally in the Amazon, through rivers, and the vector is very well established in this region.
What is the difference between the sylvatic cycle and the urban cycle of Oropouche fever?
Maria Clara: In the wild cycle, animals such as monkeys, sloths, rodents and even birds are reservoirs of the virus. The maruim is considered the main vector and some species of mosquitoes also transmit the virus. Insects become infected by biting an infected animal and transmit the virus to other animals through the bite. When humans enter the forest, they can become infected in this cycle.
In the urban cycle, humans are the reservoir of the virus. Studies carried out in the 1980s indicate that the maruim is the main vector in this environment. According to these studies, the Culex quinquefasciatus, popularly called mosquito or muriçoca, can act as a secondary vector. Insects become infected by biting an infected individual and transmit the virus to other individuals through the bite.
This year, for the first time, transmission of the disease was confirmed in several states outside the Amazon. If the vector is present throughout Brazil, why were cases of Oropouche fever concentrated for so long only in the North Region?
Maria Luiza: Biologically, we can question whether there are differences between maruin populations, which could make Amazon vectors more efficient in transmitting Oropouche.
However, there are other factors that can contribute to the pattern of the disease. In 2021, an outbreak of Oropouche was recorded in extra-Amazonian departments in Peru. This year, we are seeing cases outside the Amazon in Brazil.
One factor that we need to consider is population movement, which is increasingly intense between regions and countries. The virus moves with humans. If an infected individual arrives in a place where the vector is present, transmission of the disease can begin.
Maria Clara: Another very important factor is the diagnosis. Could it be that the disease did not exist outside the Amazon or was it not being diagnosed?
As the symptoms of Oropouche fever are very similar to those of dengue fever and the two diseases occur at the same time of year, cases of Oropouche can be clinically diagnosed as dengue fever.
Last year, the Ministry of Health decided to implement a protocol for diagnosing Oropouche, which was developed by Fiocruz Amazônia, at the Central Public Health Laboratories (Lacens) of the states.
Samples from patients suspected of having dengue, with a negative result for the dengue virus, began to be tested for the Oropouche virus. With this new data, we can have a clearer picture of what is happening.
Ceratopogonidae Collection holds the neotype of the species Culicoides paraensis, among other treasures. Photo: Josué Damacena
Does maruim remain the main vector of the disease?
Maria Clara: The available data indicates yes. Vector competence depends on numerous factors, but, to date, no other vector as or more competent than the maruim has been proven. The main studies on disease transmission were carried out in the 1980s, after several epidemics in the Brazilian Amazon region. In the urban cycle, these works pointed to the maruim as the primary vector of the virus and the mosquito as the secondary vector. In the experiments, it was observed that the maruim can become infected with a low viral load in the blood, while the mosquito needs a high viral load to become infected. Furthermore, during that period, the maruim was the most frequently found infected insect in epidemic areas. Our data shows that in many locations where Oropouche is currently being diagnosed, we have had previous reports of Oropouche infestation. C. paraensis, such as in Bahia, Santa Catarina, Espírito Santo and the mountainous region of Rio de Janeiro.
What makes up the collection of the Ceratopogonidae Collection of IOC?
Maria Luiza: The Collection has around 10 thousand specimens from the Ceratopogonidae family. In the collection, we have insects of hematophagous genera, in which the females feed on blood; predators, in which females feed on other insects; and pollinators, which feed exclusively on plant nectar. It is one of the most representative collections of this family in Latin America and includes species of medical and veterinary importance.
Which specimens stand out in the collection?
Maria Clara: The oldest specimens are from the work of Adolpho Lutz, from the beginning of the last century. We have, for example, type specimens, collected by him, which served as the basis for the description of 15 new species of maruins between 1912 and 1914. We also keep the neotype of the C. paraensis. It is a specimen that was designated by the Collection's curator, Maria Luiza, and the American entomologist Willis Wirth as a reference for the species, since the specimen that served as the basis for the description made by Emilio Goeldi, in 1905, was lost.
What is the relevance of this collection?
Maria Luiza: The deposited specimens are available for consultation and can contribute to new research. Furthermore, the Collection provides an important taxonomic identification service. Upon request from Health Departments or scientific institutions, we identify species of maruins that are causing infestation or were collected in research. Based on the work of the Collection, we have already described 91 new species of maruins, contributing to the knowledge of the biodiversity of these insects.
In the current context of Oropouche fever, we have worked to identify the vector, provide training and consult to implement entomological surveillance based on requests from health departments. We recently produced a Technical Note in collaboration with the Rio de Janeiro State Health Department (SES/RJ) to assist surveillance service professionals in identifying the C. paraensis.
Brazil is facing an outbreak of Oropouche fever this year, according to the Ministry of Health. In total, there were more than 7 thousand cases in 21 states as of July 28.
Recently, the first two deaths caused by the disease and one fetal death caused by vertical transmission of the virus (when the pathogen passes from mother to fetus during pregnancy) were confirmed.
Eight cases of vertical transmission are under investigation, including occurrences of fetal death and congenital malformations, such as microcephaly.
The increase in Oropouche cases drew attention to an insect little known by most of the population: the Culicoides paraensis, popularly called maruim or sandfly.
Species insects Culicoides paraensis, popularly called maruim or sandfly. Photo: Ceratopogonidae Collection of IOC/Fiocruzi
Although the insect, which stands out for its small size, has not yet been captured and identified as being infected by the virus in this year's outbreak, since the 1980s the maruim has been identified as the main vector of Oropouche fever.
At the Oswaldo Cruz Institute (IOC/Fiocruz), the Ceratopogonidae Collection keeps a collection of around 10 thousand specimens of the maruin family, including the neotype of the C. paraensis, a specimen chosen by experts as a reference for studies of the vector.
Contributing to confronting the problem, researchers from the IOC recently developed a Technical Note to guide vector surveillance actions in response to demands from the Rio de Janeiro State Health Department (SES/RJ).
In an interview, the Collection's curator, Maria Luiza Felippe Bauer, and the deputy curator, Maria Clara Alves Santarém, discuss the insect's main characteristics. Check out the interview below and learn more about the maruim.
What is the origin of this insect and where is it found?
Maria Luiza: O Culicoides paraensis It is possibly an insect native to the Americas. It was described, for the first time, in Pará, in 1905, by Emilio Goeldi. The naming of the species refers to the state. Currently, it is found in most of the American continent, from the southern United States to Argentina. In Brazil, it is believed to be present in all states, despite only having been effectively registered in 15 states to date.
What are the main characteristics of this insect?
Maria Clara: All maruins are very small insects. They measure around 1,5 mm and can reach 3 mm. Another characteristic is the very painful bite. It is an insect that causes discomfort to the population when there is an infestation.
What kind of environment does he live in?
Maria Luiza: In general, C. paraensis lives in forests and rural areas, mainly where there are banana plantations. In the north of the country, the maruim is also found in urban areas. In cities in the Amazon region, urban areas are closer to wild areas and there is this urbanization of the vector. In some municipalities outside this region, we see maruins in urbanized areas close to the rural environment.
Maria Clara: Furthermore, recently we have evidence that the C. paraensis It has been found in some urban centers in the country, which still requires confirmation. Apparently, this is occurring in areas where there has been environmental change. However, it is important to say that, to date, maruim is not an urban vector, like Aedes.
Entomologists Maria Luiza Felippe Bauer (right) and Maria Clara Alves Santarém highlight the need to identify the insect's breeding sites to try to reduce the maruin infestation. Photo: Josué Damacena
Where do maruim breed?
Maria Clara: The female maruim looks for places with plenty of organic matter and humidity to lay her eggs. In forests, decomposing tree trunks, fruit peels fallen on the ground, bromeliads, stream banks, and foliage on the ground are the preferred locations. In banana plantations, she lays her eggs on the banana tree stump, the part of the stem that remains when the tree is cut down to harvest bananas. In urban areas, she can lay eggs in the backyard if there is any type of organic matter accumulated on the ground.
What is the maruim’s life cycle like?
Maria Luiza: The life cycle is similar to that of mosquitoes. In breeding areas, the eggs hatch releasing larvae that feed on organic matter. The larvae go through four stages of development, then become pupae, which do not feed and transform into the adult insect. Based on studies of Culicoides species that occur in Europe, the cycle takes about 30 days from egg to adult insect. However, there is no specific data on the development time of the C. paraensis.
How many eggs does the female lay?
Maria Clara: Studies on insects of the genus Culicoides indicate that females can lay 30 to 450 eggs per clutch, depending on the species and blood meal. But there is no specific information about C. paraensis.
The small size is a striking characteristic of the maruim, which measures around 1,5 mm. Photo: Ceratopogonidae Collection of IOC/Fiocruzi
Why do maruim bite?
Maira Luiza: Adult maruins, both males and females, feed on plant nectar. However, females of the Culicoides genus bite because they need blood to mature their eggs.
How far does the insect fly? Is there a more frequent time for bites?
Maria Clara: It tends to stay close to its breeding site. Its own flight is around 500 m. But, as the maruim is very light, it is propelled by the wind. So, depending on the wind speed, it can fly up to 2 km.
Maria Luiza: The peak of activity, when the maruins feed with greater intensity, is in the late afternoon. But this does not mean that they are prevented from biting in the morning or at noon, if that is the time when the human being or other animal is present in the environment.
What are the control strategies for this vector?
Maria Luiza: To control the vector population it is necessary to eliminate breeding sites. In the case of maruim, the ideal is to remove the substrate where it reproduces. For example, if it is the banana tree stump, the banana plantation must be managed. If we have a yard, we must clean the land, not leaving fallen leaves or fruit peels on the ground or other decomposing organic matter. This can reduce the proliferation of the insect in that location.
What is the recommendation for personal protection?
Maria Luiza: When possible, avoid areas with the greatest infestation and try not to expose yourself during the insect's peak hours, in the late afternoon. Wear a long-sleeved blouse, long pants and closed shoes. If a person needs to enter an infested area, it is recommended to apply body oil to the skin. As maruim is very light, it sticks to the oil and cannot bite. If there is an infestation near your home, close the windows during the vector's peak hours. We know that some of these measures are difficult to adopt, mainly because the period of greatest transmission of Oropouche fever is in the summer.
Is there any point in using repellent, insecticide or screen?
Maria Clara: No. Both from scientific literature and from our own experience, we know that repellents are not effective against maru. Insecticides also don't work. These are compounds developed against mosquitoes, such as Aedes and Culex, which are insects from a different family. As maruins cross the common screen, it is recommended to use fine mesh screens, like voile, which would be as effective as closing the windows.
Specialists from the Ceratopogonidae Collection have already described 91 new species of maruins. Photo: Josué Damacena
How did the transmission of Oropouche fever begin in Brazil?
Maria Luiza: The Oropouche virus was described in 1955, from a single patient who presented the disease in the Vega de Oropouche community, in Trinidad and Tobago, in the Caribbean. But, at that time, it was not given importance because it was an isolated case.
In 1961, the first urban epidemic of Oropouche was recorded, in Belém do Pará, which reached 11 thousand cases. In the following years, several epidemics occurred in different locations in Pará.
It is believed that the disease spread in the state following the construction of the Belém-Brasília Highway, which deforested areas of forest. The workers entered the forest, where the disease circulated in the wild, and became infected.
From the 80s onwards, epidemics began to occur in other northern states and other countries, such as Peru, Panama, Colombia, Ecuador and French Guiana. More recently, there have been records in Bolivia and Cuba.
It was probably human movement that spread the disease, because the population has always moved internally in the Amazon, through rivers, and the vector is very well established in this region.
What is the difference between the sylvatic cycle and the urban cycle of Oropouche fever?
Maria Clara: In the wild cycle, animals such as monkeys, sloths, rodents and even birds are reservoirs of the virus. The maruim is considered the main vector and some species of mosquitoes also transmit the virus. Insects become infected by biting an infected animal and transmit the virus to other animals through the bite. When humans enter the forest, they can become infected in this cycle.
In the urban cycle, humans are the reservoir of the virus. Studies carried out in the 1980s indicate that the maruim is the main vector in this environment. According to these studies, the Culex quinquefasciatus, popularly called mosquito or muriçoca, can act as a secondary vector. Insects become infected by biting an infected individual and transmit the virus to other individuals through the bite.
This year, for the first time, transmission of the disease was confirmed in several states outside the Amazon. If the vector is present throughout Brazil, why were cases of Oropouche fever concentrated for so long only in the North Region?
Maria Luiza: Biologically, we can question whether there are differences between maruin populations, which could make Amazon vectors more efficient in transmitting Oropouche.
However, there are other factors that can contribute to the pattern of the disease. In 2021, an outbreak of Oropouche was recorded in extra-Amazonian departments in Peru. This year, we are seeing cases outside the Amazon in Brazil.
One factor that we need to consider is population movement, which is increasingly intense between regions and countries. The virus moves with humans. If an infected individual arrives in a place where the vector is present, transmission of the disease can begin.
Maria Clara: Another very important factor is the diagnosis. Could it be that the disease did not exist outside the Amazon or was it not being diagnosed?
As the symptoms of Oropouche fever are very similar to those of dengue fever and the two diseases occur at the same time of year, cases of Oropouche can be clinically diagnosed as dengue fever.
Last year, the Ministry of Health decided to implement a protocol for diagnosing Oropouche, which was developed by Fiocruz Amazônia, at the Central Public Health Laboratories (Lacens) of the states.
Samples from patients suspected of having dengue, with a negative result for the dengue virus, began to be tested for the Oropouche virus. With this new data, we can have a clearer picture of what is happening.
Ceratopogonidae Collection holds the neotype of the species Culicoides paraensis, among other treasures. Photo: Josué Damacena
Does maruim remain the main vector of the disease?
Maria Clara: The available data indicates yes. Vector competence depends on numerous factors, but, to date, no other vector as or more competent than the maruim has been proven. The main studies on disease transmission were carried out in the 1980s, after several epidemics in the Brazilian Amazon region. In the urban cycle, these works pointed to the maruim as the primary vector of the virus and the mosquito as the secondary vector. In the experiments, it was observed that the maruim can become infected with a low viral load in the blood, while the mosquito needs a high viral load to become infected. Furthermore, during that period, the maruim was the most frequently found infected insect in epidemic areas. Our data shows that in many locations where Oropouche is currently being diagnosed, we have had previous reports of Oropouche infestation. C. paraensis, such as in Bahia, Santa Catarina, Espírito Santo and the mountainous region of Rio de Janeiro.
What makes up the collection of the Ceratopogonidae Collection of IOC?
Maria Luiza: The Collection has around 10 thousand specimens from the Ceratopogonidae family. In the collection, we have insects of hematophagous genera, in which the females feed on blood; predators, in which females feed on other insects; and pollinators, which feed exclusively on plant nectar. It is one of the most representative collections of this family in Latin America and includes species of medical and veterinary importance.
Which specimens stand out in the collection?
Maria Clara: The oldest specimens are from the work of Adolpho Lutz, from the beginning of the last century. We have, for example, type specimens, collected by him, which served as the basis for the description of 15 new species of maruins between 1912 and 1914. We also keep the neotype of the C. paraensis. It is a specimen that was designated by the Collection's curator, Maria Luiza, and the American entomologist Willis Wirth as a reference for the species, since the specimen that served as the basis for the description made by Emilio Goeldi, in 1905, was lost.
What is the relevance of this collection?
Maria Luiza: The deposited specimens are available for consultation and can contribute to new research. Furthermore, the Collection provides an important taxonomic identification service. Upon request from Health Departments or scientific institutions, we identify species of maruins that are causing infestation or were collected in research. Based on the work of the Collection, we have already described 91 new species of maruins, contributing to the knowledge of the biodiversity of these insects.
In the current context of Oropouche fever, we have worked to identify the vector, provide training and consult to implement entomological surveillance based on requests from health departments. We recently produced a Technical Note in collaboration with the Rio de Janeiro State Health Department (SES/RJ) to assist surveillance service professionals in identifying the C. paraensis.
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