It is likely that recent rains and floods have washed away many of the terrestrial parasites in the waterways of the area. How will it affect the animals that live downstream?
With recent rainstorms, floods, and landslides, the primary concern is, rightly, their impact on the safety and health of British Columbia residents.
We also pay attention to damaged transportation routes that impede our ability to provide assistance and access medical care, evacuate people and livestock, move goods, and to homes, businesses and farms that have been flooded or destroyed.
But when the storms of the year fade – and we all hope sooner in March – we’ll be better able to assess the damage downstream.
For example, we already know that this year’s floods may affect salmon stocks for years to come. Raging rivers and streams had washed away their spawning eggs and released young salmon into the sea ahead of their time, clearing or smothering important breeding sites, and hampering salmon struggling upstream to breed.
Other effects will be less noticeable and perhaps more difficult to track. We may not know for a while what all the fertilizers, fuels, litter, manure, and pesticides, and who knows what, as well as all the sediments flowing into the sea, will do to the fish and the fish-supporting bio-habitat of BC coastal waters. We may not know for months how many layers of oysters will choke the plumes of toxic sediment.
In years we may not see traces of bacteria, fungi, and other microbes washed out of the rich, now-flooded soils of the lower mainland, dairy, pig and poultry farms and urban backyards.
But what happens on land can affect the creatures at sea. In one recent study, researchers from Canada and the US Pacific Northwest have compiled a history of an outbreak of the deadly fungus Cryptococcus gattii in marine mammals.
Beginning on the island, and then spreading to mainland BC, Washington, Oregon and California, cases of the fungus infecting humans, pets, and inhabiting wildlife have been reported since 1999. Additionally, porpoises and Pacific white dolphins in the Salish Sea have been known to have died from fungi; In fact, the first case of C. gattii in the Pacific Northwest likely occurred in Dall’s porpoise in 1997—two years before the first known human case in the area.
Cryptococcus gattii is an earth fungus. Live in soil and trees. In order for a person or animal to become infected, they must breathe in the spores of the fungus. Only then can it cause lung and brain diseases.
Construction, logging, and other soil-disturbing activities can spread germs. Floods disturb the soil and can disperse fungal spores, as well as wash them into waterways and out into the sea. Once there, waves and even raindrops hitting the water can release spores into the air, where they can settle above the sea surface, where marine mammals inhale them.
The study showed that marine mammals that died of C. gattii were found near terrestrial hotspots of C. gattii.
Another recent study tracks how a parasite that reproduces like crazy in the guts of cats is affecting wildlife in densely populated urban areas, near and downstream.
The study led by the University of British Columbia examined 45,000 cases of toxoplasmosis in wild mammals, using data from more than 200 global studies. Many species, including sea otters, seals, sea lions, dolphins, and beluga whales, are susceptible to infection with Toxoplasma gondii and can die from them.
A single cat can release up to 500 million parasite eggs (called sac eggs) within two weeks. Eggs can live for years in soil and water. The researchers found that wildlife living near dense urban areas were more susceptible to infection than other animals.
In a 2020 study investigating disease and other factors in stranded orca whales from the Pacific Northwest, researchers noted that the adult female orca they examined had both Toxoplasma and Sarcocystis, another land-borne parasite that typically occurs in Horses and opossums.
The association of the farm animal parasite and marine mammals of eastern Canada has also been confirmed with Neosporum caninum, the canine version of Toxoplasma, where cattle are an important mediating host for the spread of the microbe.
In addition, Cryptosporidium and Giardia, which are well studied in terrestrial ecosystems, have been found infesting otters and seals in rivers in Puget Sound, and seals and whales in eastern and northern Canada.
It is likely that the recent rains and floods have washed away many of the land-spreading parasites in the waterways of the region. How they will affect the vulnerable creatures living in the sea stream, and whether we will see these effects before sick and dying animals sink beneath the waves remains to be seen.