Fungus that killed dolphins in early 2000s may have come from humans, study finds

A deadly fungus that killed over 40 dolphins and porpoises in the Salish Sea in the late nineties and early 2000s may have come from human activities on land.

Between 1997 and 2016, 42 cases of marine mammals infected with the Cryptococcus gattii fungus were identified in Washington and British Columbia, according to a new study by scientists from the University of California (UC) Davis School of Veterinary Medicine.

C gattii lives in the soil and also in tree dwellings, particularly in tropical and subtropical forests, said the study, published in the journal Diseases of Aquatic Organisms on 21 October.

Breathing in fungal spores of C gattii could lead to lung and brain disease in humans and other animals, said the study, which said the pathogen was not considered to be contagious.

Piecing together the history of the fungal outbreak in marine mammals found that manmade changes on land may have led to the fungal spores spreading to the sea.

Human activities such as construction and deforestation, that disturb the soil, can aerosolise C gattii spores, causing infection in people and animals that live near such disturbed sites, the study noted.

“As we change the environment in unprecedented ways, we could see more diseases that affect people and wildlife,” the study’s lead author Sarah Teman, from the UC Davis School of Veterinary Medicine, said in a statement.

Nearly 60 humans – mostly those with compromised immune systems – were affected by the fungal outbreak in the late nineties and early 2000s as well.

Scientists, however, said the first probable case of C gattii may have occurred in a porpoise in the Pacific Northwest in 1997, two years before the identification of the first human case in the region in 1999.

In the case of the dolphins and porpoises, which died during this period in the Salish Sea, scientists said these marine mammals were found near the fungal outbreak’s terrestrial hotspots.

Researchers suspect the spores may have settled on the surface of the sea, where porpoises and dolphins inhaled them when they reached above surface to breathe.

“Often we study marine mammals because they play important roles in the ecosystem, and they are cool. Too often we forget that they can also alert us to diseases that affect humans,” said study co-author Joe Gaydos, a wildlife veterinarian at UC Davis.