A significant threat to Hector’s and Māui dolphins
Toxoplasmosis is an infection caused by the Toxoplasma gondii parasite. The parasite is common and capable of infecting many animals, including humans. Up to one third of people worldwide carry T. gondii, although most never develop symptoms.
Toxoplasmosis is, however, a confirmed cause of death in Hector’s and Māui dolphins and is likely to be a significant human-caused threat to the dolphins’ populations. This is especially the case for the critically endangered Māui dolphin.
Toxoplasmosis is a cause of death in marine mammals elsewhere, including southern sea otters and Hawaiian monk seals, and is also known to cause behavioural changes, still births and reduced reproductive rates.
How are dolphins exposed to the parasite?
Cats, both domestic and feral, are the only animal in which the toxoplasma parasite can reproduce. The ocysts (eggs) are spread via cat faeces and can survive for many months in the environment. Rainwater and run-off transport the oocysts into the marine ecosystem through streams, rivers and stormwater drains. Hector’s and Māui dolphins can then become infected by consuming contaminated water or prey (eg fish).
Wastewater treatment plants may also be a source of contamination (if cat faeces/kitty litter have been flushed down the toilet). Unfortunately, toxoplasma oocysts cannot be treated by standard wastewater disinfection methods such as UV radiation.
There is no vaccination available for dolphins, and addressing this threat requires multiple approaches to reduce the amount of cat faeces entering rivers, estuaries and the sea.
How you can help
To help prevent the parasite from reaching Hector’s and Māui dolphin:
- keep cats indoors
- dispose of cat faeces in the rubbish bin not the toilet
- spay or neuter your cat
- do not abandon unwanted cats or feed feral cats
- support wetland conservation, which helps stop eggs reaching the ocean
- include green spaces in your garden or barkyard to help filter rainwater and reduce stormwater runoff.
Download this information with images in a factsheet: Is your cat making dolphins sick? (PDF, 3,640K)