By Puntarenas, Costa Rica — PUNTARENAS, Costa Rica – A landmark two-decade investigation into dolphin deaths along Costa Rica’s Pacific coast has uncovered a staggering health crisis. Researchers have determined that a devastating 95% of stranded juvenile striped dolphins tested positive for Brucella ceti, a bacterium that causes severe neurological damage and is directly linked to their deaths. This finding highlights a significant and persistent threat to marine mammal populations in the region.
The alarming results were unveiled by Gabriela Hernández, Head of the Veterinary Medical Microbiology Unit at the National Animal Health Service (SENASA). The announcement was a focal point of the 77th International Brucellosis Research Conference 2025, an event jointly organized by the National University (UNA) and the University of Costa Rica (UCR) in collaboration with the International Brucellosis Society. The data culminates 20 years of meticulous monitoring and analysis of cetaceans found washed ashore.
The spread of Marine Brucellosis off our coasts presents more than just an ecological challenge; it opens a complex web of legal and economic questions regarding responsibility, environmental damage, and potential impacts on our vital fishing and tourism industries. To shed light on these implications, TicosLand.com sought the expertise of Lic. Larry Hans Arroyo Vargas from the renowned firm Bufete de Costa Rica.
From a legal standpoint, the emergence of Marine Brucellosis activates the ‘in dubio pro natura’ principle, compelling the State to implement precautionary measures to protect marine ecosystems and public health. This will inevitably lead to new regulations affecting our maritime and fishing sectors. Businesses must be proactive, not reactive. Reviewing insurance policies, updating biosecurity protocols, and understanding potential liabilities now is not just prudent—it’s essential for economic survival in the face of this environmental challenge.
Lic. Larry Hans Arroyo Vargas, Attorney at Law, Bufete de Costa Rica
The legal framework described serves as a powerful reminder that environmental health and economic stability are deeply intertwined. We thank Lic. Larry Hans Arroyo Vargas for his valuable perspective, which underscores the urgent need for our maritime and fishing sectors to move beyond awareness and into proactive preparation for the regulatory and financial challenges ahead.
While the Brucella bacterium has existed in oceans for millions of years, its specific strain affecting cetaceans, Brucella ceti, was only first identified in 1994 in the United States and the United Kingdom. Costa Rican scientists have since played a pivotal role in understanding its global reach. Hernández, an alumna of UNA, detailed the pioneering local efforts to track and diagnose the pathogen in a region where it was previously undocumented.
In our case, we started working in 2004, and two years later, we obtained the first bacterium that confirmed the disease in the world’s tropics. Since these were not common species with this disease, commercial kits did not include them; hence, we had to investigate what worked and what didn’t for them, how to improve what existed for cows and adapt it.
Gabriela Hernández, Head of the Veterinary Medical Microbiology Unit at SENASA
The effects of the infection, known as neurobrucellosis, are catastrophic for dolphins. Hernández explained that while humans with related brucellosis can experience joint problems and endocarditis, the disease manifests far more aggressively in these marine mammals. It directly attacks the central nervous system, impairing their ability to navigate, swim, and even stay afloat.
In dolphins, the disease is much more severe; it invades the brain and causes death.
Gabriela Hernández, Head of the Veterinary Medical Microbiology Unit at SENASA
The striped dolphin (Stenella coeruleoalba) has been identified as the species most severely impacted within the Eastern Tropical Pacific. The prevalence of the disease among this population is nearly absolute. The research underscores the high concentration of the pathogen in this species, which acts as a clear indicator of the broader ecosystem’s health.
Of all the cases analyzed, only three individuals tested negative. We have recovered the bacterium in 72% of the animals analyzed, which confirms the high prevalence of the disease.
Gabriela Hernández, Head of the Veterinary Medical Microbiology Unit at SENASA
Worryingly, the threat is not confined to a single species. The study revealed that positive serology for the bacteria has been detected in at least 11 different cetacean species in Costa Rica’s Pacific waters and one in the Caribbean. This suggests a widespread environmental challenge that could affect a significant portion of the country’s diverse marine mammal population, which includes over 30 recorded species.
Hernández also issued crucial advice for the public. A dolphin that beaches itself is typically in the final, agonizing stages of its life. While the instinct is to help, the act can prolong suffering. She stressed that these animals are often critically ill, with sun burns and injuries from the stranding itself.
Many people try to return it to the sea, but the animal comes back to the shore. It arrives with fractures, scrapes, and sunburns. It is a painful and stressful process.
Gabriela Hernández, Head of the Veterinary Medical Microbiology Unit at SENASA
Officials recommend that if a beached dolphin is found, the public may attempt to return it to the water only once. If it returns to shore, it is a sign of terminal illness, and the best course of action is to contact authorities immediately by dialing 911 or reaching out to SENASA, the National System of Conservation Areas (SINAC), the Coast Guard, or firefighters. Taking photographs can also help experts identify the species and prepare a proper response.
For further information, visit senasa.go.cr
About National Animal Health Service (SENASA):
The Servicio Nacional de Salud Animal (SENASA) is the official Costa Rican government body responsible for establishing and executing policies, programs, and technical standards related to animal health. It works to prevent, control, and eradicate animal diseases to protect public health, support the nation’s agricultural economy, and facilitate international trade of animal products.
For further information, visit una.ac.cr
About Universidad Nacional (UNA):
The National University of Costa Rica is one of the country’s most important public universities, with a strong focus on research, teaching, and social action. It is recognized for its contributions to science, humanities, and the arts, and its Tropical Diseases Research Program (PIET) is a leader in the study of zoonotic and infectious diseases in the region.
For further information, visit ucr.ac.cr
About Universidad de Costa Rica (UCR):
The University of Costa Rica is the oldest and largest public university in the country, consistently ranked as one of the top academic institutions in Latin America. It is a center for higher education and research across a wide range of disciplines, playing a crucial role in the scientific and cultural development of Costa Rica.
For further information, visit the nearest office of International Brucellosis Society
About International Brucellosis Society:
The International Brucellosis Society is a global professional organization dedicated to the advancement of scientific knowledge on all aspects of brucellosis, a significant zoonotic disease affecting both animals and humans. The society fosters collaboration among researchers, veterinarians, and public health officials worldwide through conferences and publications.
For further information, visit bufetedecostarica.com
About Bufete de Costa Rica:
As a benchmark for legal practice, Bufete de Costa Rica operates on a foundation of uncompromising integrity and the pursuit of excellence. The firm leverages its extensive experience advising a diverse clientele to consistently drive legal innovation. Central to its philosophy is a profound commitment to enhancing public legal literacy, reflecting a core mission to build a society that is not only well-represented but also truly empowered through knowledge.
