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You are here: News » African snail: what are the real risks for the population?

African snail: what are the real risks for the population?

According to data from the International Union for Conservation of Nature (IUCN), invasive species represent the second greatest threat to biodiversity on the entire planet, second only to deforestation.
By Journalism IOC22/05/2007 - Updated on 25/08/2022

According to data from the International Union for Conservation of Nature (IUCN), invasive species represent the second greatest threat to biodiversity on the entire planet, second only to deforestation.

In Brazil, an example with negative impacts on nature, the economy and also on human health is the African snail, introduced in the country in the late 80s, illegally imported from East and Northeast Africa as a more profitable substitute for escargot.

The Department of Malacology at Instituto Oswaldo Cruz (IOC), National Reference Center for Medical Malacology, works to identify the mollusc and study the diseases it can transmit to humans.

In an interview, researcher Silvana Thiengo comments on the real risks offered by the species and clarifies which precautions should be taken by the population.

 
Currently in the explosive phase of the invasion, the African snail has dense populations, especially in the Southeast and Midwest regions. Photo: Gutemberg Brito

The Giant Snail or African Snail is an invasive species. How did she arrive in Brazil?

Achatina fulica It is a species of African origin. We have news that the species was introduced in Brazil through an agricultural fair that took place in the 80s, in the state of Paraná. However, there is no record of the import authorization for this material at the Brazilian Institute of the Environment and Renewable Natural Resources (IBAMA) or at the Ministry of Agriculture, Livestock and Supply (MAPA).

The initial purpose was to commercialize the species for consumption. What is the result of the failure of this attempt?

The African snail was imported for human consumption, as an option to the snail🇧🇷 This mollusk is mainly consumed in Africa and has its nutritional advantages, such as being rich in protein. At the fair held in Paraná, kits were sold that included the matrix with a certain number of copies and booklets that taught how to start breeding. The promise was of immediate profit. However, as Brazilians are not used to consuming this type of food, the demand did not exist and the breeders inadvertently released the molluscs into nature, without imagining the harm they were causing.

Where is the African snail present in the country today?

About two decades after being introduced, today the species is present, in addition to the Federal District, in 23 of the 26 Brazilian states, including the Amazon region and environmental reserves. Currently, we are witnessing the most explosive phase of the invasion, that is, the occurrence of dense populations, consisting of large specimens of these molluscs. Despite being a terrestrial mollusk, we observed in Brazil the presence of A. fulica on riverbanks and floating vegetation. In the total of 5.561 Brazilian municipalities, there are records of the presence of the African snail in 439 – around 8%. The largest number of infested municipalities is concentrated in the Southeast and Midwest regions. In Rio de Janeiro, for example, in June 2002 there were records of the presence of the African snail in eight municipalities. Five months later, there were already 16 municipalities. In June 2006, there were records in 57 of the 92 municipalities in Rio.  

Specialist Silvana Thiengo indicates the design of the edges of the snails, the main difference between the African snail (right) and the native species. Photo: Gutemberg Brito

The African snail is present in urban environments, but also in rural environments. What are the losses in this context?

In urban environments the populations of these molluscs are very dense, they invade and destroy vegetable gardens and gardens. In addition, as these populations are made up of large animals [10 cm on average], they cause a lot of inconvenience to communities in the affected areas. Economic losses have been observed, especially in areas of small-scale agricultural production where the African snail can be considered an agricultural pest. Bananas, broccoli, sweet potatoes, squash, tomatoes and lettuce are some of the hardest hit items.

The rapid proliferation of these molluscs has been scaring the population. What are the real risks offered by the African snail?

There are two zoonoses that can be transmitted by the African snail. One is called eosinophilic meningitis, caused by a worm [Angiostrongylus cantonensis], which passes through the central nervous system, before lodging in the lungs. The disease cycle involves molluscs and rodents. Man can accidentally get into this cycle. In Brazil, there is no record of any case of this disease, which has already been verified in the Pacific Islands, in Southeast Asia, Australia and the United States. The second zoonosis is abdominal angiostrongyliasis, with cases already registered in Brazil, but not transmitted by the African snail. Abdominal angiostrangiliasis [caused by the parasite Angiostrongylus costaricensis] is often asymptomatic, but in some cases it can lead to death, due to intestinal perforation and peritonitis. In laboratory tests, Achatine fulica did not prove to be a good host, therefore being considered a potential host for the parasite, which causes abdominal angiostrongyliasis – but, I emphasize, it is a host potential.

What is the risk of African snails transmitting these diseases?

In the current state of knowledge, we can say that the risk of the African snail transmitting these two parasites is very small. Even so, care must be taken when handling molluscs found free in the environment, which under no circumstances should be ingested. In addition, the vegetables should be washed well and soaked in a 1,5% sodium hypochlorite solution [1 tablespoon of bleach diluted in 1 liter of filtered water] for about 30 minutes. , before being consumed.

African snail populations are very numerous. What explains this fact?

The dense populations of this mollusk in Brazil are mainly due to its great biotic potential and the absence of specific pathogens. Despite being herbivores, they are very voracious and undemanding to feed themselves, eating practically anything. A specimen can lay an average of 200 eggs per posture and reproduce more than once a year. These eggs are about the size of a papaya seed, yellowish white and are half buried. Therefore, when picking is done, you must be careful to pick up and destroy the eggs as well.

What precautions should people take?

The main measure to be taken is control through collection. The use of pesticides is not recommended due to the high toxicity of these substances. The best option is manual collection with hands protected with gloves or plastic bags. This procedure can be carried out in the early hours of the morning or in the evening, times when the snails are most active and it is possible to collect the greatest number of specimens. During the day, they hide to protect themselves from the sun.

How to eliminate snails after collection?

Salt, which would be an option to eliminate molluscs, is not recommended because its excessive use harms the soil and planting. The Action Plan for the Control of Achatina fulica from IBAMA recommends that after collection, the molluscs should be crushed, covered with quicklime and buried. Other options are to pour boiling water into a container to kill the collected snails or to incinerate them, as long as these procedures are carried out safely. The material can be bagged and disposed of in common garbage, but it is necessary to break the shells so that they do not accumulate water and become breeding grounds for mosquitoes, such as the Aedes aegypti, dengue virus vector.

The African snail is often confused with a native Brazilian mollusk, the Megalobulimus sp., known as the pink-mouthed snail or aruá-do-mato. How is it possible to distinguish the two species?

O Megalobulimus sp. is a species of our fauna and looks like the Achatina fulica for its size. However, he only lays two eggs in each reproductive cycle. As the mollusk native to Brazil reproduces little, it is important to be able to distinguish the difference between the two so that the Brazilian species is not harmed. the shell of Achatina fulica it has more turns and is more elongated. Now the shell of megalobulimus sp is more bulging, fatter, has fewer turns and its opening is thick, not cutting.

Like IOC contribute to knowledge about the African snail?

We analyzed snails sent by health departments throughout Brazil and evaluated the possible presence of disease-causing parasites. This epidemiological surveillance activity is essential to monitor how African snails can pose a risk to the population. We have already found larvae of parasites from birds or other domestic animals, which are of no human interest. However, this fact indicates that the African snail population is already inserted in areas where parasite cycles occur. This is the researchers' biggest concern, since, due to its proximity to homes, it may become infected with other forms and become an intermediate host for human diseases. We also work on training and qualifying health and environment technicians on the subject.

What are the prospects for the natural control of these populations by the very conditions of the environment?

In Africa, the environment of origin of the giant snail, there are pathogens, such as, for example, bacteria, fungi and parasites, which carry out the natural control of this population. In Brazil, where the giant snail is not native, ecological studies on this species are still incipient and the perspectives we have are based on experiences in other countries, such as the United States and India. In some regions of India, where the introduction took place more than 100 years ago, no decline in the populations of these molluscs has been observed. In Hawaii, the great explosion of the African snail occurred a few years after its introduction, in the 30s, when it was introduced. Today, although they have not been eliminated in the country, due to factors not yet fully known, large specimens such as those found here are no longer found and the population has declined significantly, stabilizing at tolerable levels. We hope that the same thing that happened in Hawaii happens here in Brazil, but the fundamental thing, without a doubt, is to promote the control through the action of the population itself through the collection and elimination of the specimens, following the recommendations that we already mentioned.

According to data from the International Union for Conservation of Nature (IUCN), invasive species represent the second greatest threat to biodiversity on the entire planet, second only to deforestation.
By: 
journalism

According to data from the International Union for Conservation of Nature (IUCN), invasive species represent the second greatest threat to biodiversity on the entire planet, second only to deforestation.

In Brazil, an example with negative impacts on nature, the economy and also on human health is the African snail, introduced in the country in the late 80s, illegally imported from East and Northeast Africa as a more profitable substitute for escargot.

The Department of Malacology at Instituto Oswaldo Cruz (IOC), National Reference Center for Medical Malacology, works to identify the mollusc and study the diseases it can transmit to humans.

In an interview, researcher Silvana Thiengo comments on the real risks offered by the species and clarifies which precautions should be taken by the population.

 
Currently in the explosive phase of the invasion, the African snail has dense populations, especially in the Southeast and Midwest regions. Photo: Gutemberg Brito

The Giant Snail or African Snail is an invasive species. How did she arrive in Brazil?

Achatina fulica It is a species of African origin. We have news that the species was introduced in Brazil through an agricultural fair that took place in the 80s, in the state of Paraná. However, there is no record of the import authorization for this material at the Brazilian Institute of the Environment and Renewable Natural Resources (IBAMA) or at the Ministry of Agriculture, Livestock and Supply (MAPA).

The initial purpose was to commercialize the species for consumption. What is the result of the failure of this attempt?

The African snail was imported for human consumption, as an option to the snail🇧🇷 This mollusk is mainly consumed in Africa and has its nutritional advantages, such as being rich in protein. At the fair held in Paraná, kits were sold that included the matrix with a certain number of copies and booklets that taught how to start breeding. The promise was of immediate profit. However, as Brazilians are not used to consuming this type of food, the demand did not exist and the breeders inadvertently released the molluscs into nature, without imagining the harm they were causing.

Where is the African snail present in the country today?

About two decades after being introduced, today the species is present, in addition to the Federal District, in 23 of the 26 Brazilian states, including the Amazon region and environmental reserves. Currently, we are witnessing the most explosive phase of the invasion, that is, the occurrence of dense populations, consisting of large specimens of these molluscs. Despite being a terrestrial mollusk, we observed in Brazil the presence of A. fulica on riverbanks and floating vegetation. In the total of 5.561 Brazilian municipalities, there are records of the presence of the African snail in 439 – around 8%. The largest number of infested municipalities is concentrated in the Southeast and Midwest regions. In Rio de Janeiro, for example, in June 2002 there were records of the presence of the African snail in eight municipalities. Five months later, there were already 16 municipalities. In June 2006, there were records in 57 of the 92 municipalities in Rio.  

Specialist Silvana Thiengo indicates the design of the edges of the snails, the main difference between the African snail (right) and the native species. Photo: Gutemberg Brito

The African snail is present in urban environments, but also in rural environments. What are the losses in this context?

In urban environments the populations of these molluscs are very dense, they invade and destroy vegetable gardens and gardens. In addition, as these populations are made up of large animals [10 cm on average], they cause a lot of inconvenience to communities in the affected areas. Economic losses have been observed, especially in areas of small-scale agricultural production where the African snail can be considered an agricultural pest. Bananas, broccoli, sweet potatoes, squash, tomatoes and lettuce are some of the hardest hit items.

The rapid proliferation of these molluscs has been scaring the population. What are the real risks offered by the African snail?

There are two zoonoses that can be transmitted by the African snail. One is called eosinophilic meningitis, caused by a worm [Angiostrongylus cantonensis], which passes through the central nervous system, before lodging in the lungs. The disease cycle involves molluscs and rodents. Man can accidentally get into this cycle. In Brazil, there is no record of any case of this disease, which has already been verified in the Pacific Islands, in Southeast Asia, Australia and the United States. The second zoonosis is abdominal angiostrongyliasis, with cases already registered in Brazil, but not transmitted by the African snail. Abdominal angiostrangiliasis [caused by the parasite Angiostrongylus costaricensis] is often asymptomatic, but in some cases it can lead to death, due to intestinal perforation and peritonitis. In laboratory tests, Achatine fulica did not prove to be a good host, therefore being considered a potential host for the parasite, which causes abdominal angiostrongyliasis – but, I emphasize, it is a host potential.

What is the risk of African snails transmitting these diseases?

In the current state of knowledge, we can say that the risk of the African snail transmitting these two parasites is very small. Even so, care must be taken when handling molluscs found free in the environment, which under no circumstances should be ingested. In addition, the vegetables should be washed well and soaked in a 1,5% sodium hypochlorite solution [1 tablespoon of bleach diluted in 1 liter of filtered water] for about 30 minutes. , before being consumed.

African snail populations are very numerous. What explains this fact?

The dense populations of this mollusk in Brazil are mainly due to its great biotic potential and the absence of specific pathogens. Despite being herbivores, they are very voracious and undemanding to feed themselves, eating practically anything. A specimen can lay an average of 200 eggs per posture and reproduce more than once a year. These eggs are about the size of a papaya seed, yellowish white and are half buried. Therefore, when picking is done, you must be careful to pick up and destroy the eggs as well.

What precautions should people take?

The main measure to be taken is control through collection. The use of pesticides is not recommended due to the high toxicity of these substances. The best option is manual collection with hands protected with gloves or plastic bags. This procedure can be carried out in the early hours of the morning or in the evening, times when the snails are most active and it is possible to collect the greatest number of specimens. During the day, they hide to protect themselves from the sun.

How to eliminate snails after collection?

Salt, which would be an option to eliminate molluscs, is not recommended because its excessive use harms the soil and planting. The Action Plan for the Control of Achatina fulica from IBAMA recommends that after collection, the molluscs should be crushed, covered with quicklime and buried. Other options are to pour boiling water into a container to kill the collected snails or to incinerate them, as long as these procedures are carried out safely. The material can be bagged and disposed of in common garbage, but it is necessary to break the shells so that they do not accumulate water and become breeding grounds for mosquitoes, such as the Aedes aegypti, dengue virus vector.

The African snail is often confused with a native Brazilian mollusk, the Megalobulimus sp., known as the pink-mouthed snail or aruá-do-mato. How is it possible to distinguish the two species?

O Megalobulimus sp. is a species of our fauna and looks like the Achatina fulica for its size. However, he only lays two eggs in each reproductive cycle. As the mollusk native to Brazil reproduces little, it is important to be able to distinguish the difference between the two so that the Brazilian species is not harmed. the shell of Achatina fulica it has more turns and is more elongated. Now the shell of megalobulimus sp is more bulging, fatter, has fewer turns and its opening is thick, not cutting.

Like IOC contribute to knowledge about the African snail?

We analyzed snails sent by health departments throughout Brazil and evaluated the possible presence of disease-causing parasites. This epidemiological surveillance activity is essential to monitor how African snails can pose a risk to the population. We have already found larvae of parasites from birds or other domestic animals, which are of no human interest. However, this fact indicates that the African snail population is already inserted in areas where parasite cycles occur. This is the researchers' biggest concern, since, due to its proximity to homes, it may become infected with other forms and become an intermediate host for human diseases. We also work on training and qualifying health and environment technicians on the subject.

What are the prospects for the natural control of these populations by the very conditions of the environment?

In Africa, the environment of origin of the giant snail, there are pathogens, such as, for example, bacteria, fungi and parasites, which carry out the natural control of this population. In Brazil, where the giant snail is not native, ecological studies on this species are still incipient and the perspectives we have are based on experiences in other countries, such as the United States and India. In some regions of India, where the introduction took place more than 100 years ago, no decline in the populations of these molluscs has been observed. In Hawaii, the great explosion of the African snail occurred a few years after its introduction, in the 30s, when it was introduced. Today, although they have not been eliminated in the country, due to factors not yet fully known, large specimens such as those found here are no longer found and the population has declined significantly, stabilizing at tolerable levels. We hope that the same thing that happened in Hawaii happens here in Brazil, but the fundamental thing, without a doubt, is to promote the control through the action of the population itself through the collection and elimination of the specimens, following the recommendations that we already mentioned.

The non-profit reproduction of the text is allowed as long as the source is cited (Comunicação / Instituto Oswaldo Cruz)