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.

With only 63 Māui dolphins (over the age of one) left, the most immediate risk is to this subspecies.

How are dolphins exposed to the parasite?

Cats are the only animal in which the toxoplasma parasite can sexually reproduce. The parasite creates oocysts (eggs) in the guts of cats that are spread into the environment via cat faeces where they can survive for many months.

Rainwater and run-off transport the oocysts into streams, rivers and stormwater drains, as well as waste water when cat faeces or kitty litter have been flushed down the toilet. Hector’s and Māui dolphins can then become infected when they ingest contaminated water or prey (fish).

There is no vaccine available for cats or dolphins.

Unfortunately, toxoplasma oocysts cannot be treated by standard wastewater treatment methods, such as UV radiation.

Addressing this threat requires multiple approaches to reduce the amount of the parasite entering rivers, estuaries and flowing out to 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.

Toxoplasmosis action plan

This plan addresses the threat of toxoplasmosis to Hector’s and Māui dolphins.

Toxoplasmosis action plan.

Factsheet

Download the information on this page with images in a factsheet (PDF, 903K)