In the rural areas of Ilhota, a municipality of approximately 17,000 residents in Santa Catarina’s Vale do Itajaí region, residents are reporting an overwhelming presence of tiny biting insects that have forced many to remain indoors despite warm temperatures. Locally known as maruins, these insects—scientifically identified as Culicoides paraensis—measure up to three millimeters in length and are recognized as the primary vector for Oropouche fever in the region.
The infestation has intensified in recent years, particularly in the Morro do Baú area, where residents describe keeping doors and windows shut even during summer months when temperatures reach 34°C. Josiane Richart, a resident of over 40 years, noted that whereas maruins have long been present in the region, their numbers became unbearable after the 2008 floods that devastated the municipality, burying 32 people under mudslides. “My late father used to say they were always around in the countryside, but barely noticeable. After 2008, they multiplied, and though it was still tolerable, today no one can endure it,” she told local media.
Researchers point to agricultural practices as a key driver behind the surge. Caio Cezar Dias Corrêa, a zoology researcher with a doctorate from the Museu Nacional/UFRJ and postdoctoral work at UFSC, explained that while population dynamics were already unfavourable before 2008, inadequate management in banana plantations—common in the region—has significantly contributed to the insect’s proliferation. “The combination of environmental disruption from the floods and poor plantation oversight created ideal breeding conditions,” he stated.
Maruins thrive in decomposing organic matter, particularly in and around banana crops where fallen leaves and fruit husks provide ideal larval habitats. Adults feed on plant nectar, but only females bite humans and animals to obtain protein for egg development. Their bites cause intense itching, skin irritation, and discomfort, though the greater concern lies in their potential to transmit Oropouche virus.
Oropouche fever presents symptoms similar to dengue, including sudden high fever, severe headache, muscle and joint pain, nausea, and vomiting. While most cases are self-limiting, rare instances can lead to meningitis or other neurological complications. The Instituto Oswaldo Cruz (Fiocruz) confirms that Culicoides paraensis is the main vector of this virus in Brazil, with transmission occurring primarily in forested and rural areas where humans come into contact with infected insects.
Local authorities acknowledge the severity of the situation. The Ilhota municipal government stated in an official notice that the infestation is concentrated in the Braço do Baú neighborhood but emphasized it is not a recent or isolated issue, describing it as a long-standing problem worsening over time and affecting neighboring municipalities. “This constitutes a regional challenge requiring responsible, technical, and integrated solutions,” the notice read.
The municipality likewise highlighted a critical obstacle: no products are currently registered with Brazil’s National Health Surveillance Agency (Anvisa) for effective control of Culicoides paraensis. Despite this limitation, officials pledged to continue efforts to address the infestation through available means, including public education on eliminating breeding sites.
Residents are advised to avoid leaving organic debris such as fruit peels and leaves on the ground, especially near banana plantations, as this reduces larval development. For properties adjacent to cultivated areas, seeking professional assistance for integrated plantation management is recommended. While fumigants and repellents offer limited relief, source reduction remains the most effective strategy.
As of mid-April 2026, no official case count of Oropouche fever linked to the current maruim outbreak in Ilhota has been released by state or federal health agencies. Surveillance efforts continue, with the Santa Catarina State Health Department monitoring vector activity and encouraging prompt reporting of symptomatic cases.
The situation in Ilhota underscores the intersection of environmental change, agricultural practices, and public health vulnerability. As climate patterns shift and land use evolves, communities in similar ecological zones may face comparable challenges with biting midges and the diseases they carry.
For updates on vector-borne disease risks and prevention guidelines in Brazil, consult the Ministry of Health’s arbovirus surveillance portal or contact local health posts.
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