According to the World Health Organization (WHO) about 18 million people are infected by the bite of the black fly in several countries of sub-Saharan Africa, Brazil and Venezuela. In Spain, the transmission of infectious diseases by this insect has not yet been demonstrated, but it has expanded rapidly, especially in areas close to riverbeds and swamps.
The most affected areas are Andalusia, Aragon, Catalonia and Madrid. Although it is true that climate change, with longer hot periods, as well as the increase in water temperature and the cleaning of riverbeds (breeding areas of the insect) are key factors in the increase in the proliferation of the black fly. In this article, Dr. Manuel Menduiña Guillén, specialist in Internal Medicine, explains the risk involved, how the bite occurs, what we should do if we are bitten and how to avoid it.
What risks does the black fly pose?
In sub-Saharan Africa, Brazil and Venezuela, the black fly transmits a serious disease called onchocerciasis or “river blindness”: an infestation caused by the filaria Onchocerca volvulus. Transmission to humans occurs through repeated exposure to the bites of infected black flies (genus Simulium) and the main symptoms are intense itching, disfiguring skin conditions and visual impairment, which can lead to permanent blindness. Some 270,000 people have been blinded by this disease.
In addition, it can transmit other diseases such as Nile fever, detected two years ago in our country, or, currently, monkeypox. Nile fever can occur with febrile illness with severe encephalitis that can lead to death.
How does the bite occur?
According to Dr. Menduiña, the insect begins its attack by inoculating a small dose of anesthetic, which allows it to bite without the affected individual being aware of it. The bite is quite painful and in some people it triggers an allergic reaction that requires urgent medical treatment. In addition, the black fly bites in the form of a saw, generating a significant wound and can lead to infections.
The final effect is a welt of several centimeters that usually bleeds and is accompanied by severe swelling that can last up to a month. Particular danger is associated with stings in areas of the face due to the significant inflammatory component that accompanies them.
What should we do if we are stung?
It is very important not to scratch, as this may worsen the wound and cause it to become infected. It is recommended to apply ice to reduce the inflammation and, in case the swelling does not go down, go to the doctor who may prescribe a mild topical or oral corticosteroid. In case of superinfection of the bite, topical or systemic antibiotics may be administered.
If an allergic reaction occurs, emergency care should be sought, especially if there is generalized skin reaction, swelling of the lips (angiedema), changes in the tone of voice or difficulty in breathing.
How to prevent stings?
“It is necessary that public administrations turn their efforts to the prevention and control of the proliferation of this species, extending prevention campaigns beyond the summer months, using larvicides to combat this pest from the earliest stages of development of the specimens of these insects,” says Dr. Menduiña.
At an individual level, we can follow some advice to prevent black fly bites:
- Wear light-colored, long-sleeved clothing.
- Avoid walking near rivers and reservoirs, wetlands, swamps and landscaped areas with fountains, especially early in the morning and late in the day.
- Do not wear bright colors.
- Install mosquito nets on the doors and windows of the house, especially if we live near rivers and wetlands.
- Use air conditioning to avoid the entry of insects due to the good temperature.
- Use insect repellents from pharmacies.