The Effects of Toxoplasmosis on Sea Otters

By Erica Baumsteiger

A couple of Sea Otters floating on their backs. Picture found on:
A couple of Sea Otters floating on their backs. Picture found on:

Parasitic toxoplasmosis at a magnification of 20x. Picture found
Parasitic toxoplasmosis at a magnification of 20x. Picture found

Background Information:

Throughout the last decade thousands of marine mammals have unexpectedly started dying off all over the world. These deaths come in unpredictable waves and can take the lives of dozens to thousands of animals. Until recently scientists have had a lot of difficulty trying to solve this mystery. In 2004 they discovered a series of infectious dieseases and oppertunistic pathogens including Toxoplasmosis, an infectious disease that has been dramatically dropping numbers of sea otters around the west coast of the United States. (Microbiology an Introduction)

A Brief History of Discovery:

"Although T. gondii was first observed in rodents by Nicolle and Manceaux in 1908, it was not identified as an agent of infectious disease until 1932. That case occurred in a congenitally infected infant, as did another case of toxoplasma encephalitis reported in 1939 by Wolf et al. T. gondii beause recognized as a severe and potentially fatal disease of adults in 1968 after several cases of toxoplasma encephalitis were found in patients with hematologic cancers. It then became more widely recorded as a cause of morbidity in immunodeficient patients, including AIDS patients beginning in 1983. T. gondii continues to be an important disease in the modern world, especially in pregnant women and immunocompromised patients." - Mandell, Bennett and Dolin (Standford University)

What is Toxoplasmosis?

Toxoplasmosis is a protozoan infection caused by the microscopic parasite toxoplasma gondii. This microscopic spore forming protozoa infects the blood stream and the lymphatic vessels.

Structure of Toxoplasa gondii. Image taken from:
Structure of Toxoplasa gondii. Image taken from:

What populations are being affected?

The two popultaions that are dramatically being affected by Toxoplasmosis are the California sea otter and the Southern sea otter. (Sea Otter Alliance)

How are Sea otters contracting virus?
Picture of the cycle of Toxoplasmosis. Image taken from:
Picture of the cycle of Toxoplasmosis. Image taken from:

Although it is difficult to say for certain, just like anything in the scientific world, scientists believe felines (both domestic and wild) are the only known definative host capable of carrying and shedding the oocytes of toxoplasmosis. A cat is infected by ingesting infected pray or other infected meat, the paracite is then consumed down into the digestive tract. Once in the digestive system of the host the paracite is able to travel down to the small intestine where within the walls the parasite can multiply. The oocytes are then released in large numbers out of the host with feces. The oocytes will start being shed three to ten days after the host has been infected and will continue to be released for up to ten to fourteen days. This cycle can release millions of oocytes into the environment and unfortunalty the oocytes of toxoplsamosis are very resistant to harsh environmental conditions meaning they have a high survival rate and are able to survive for over a year in nature. Once out of the definative host scientists speculate that the infected feces is either washed away into the draining systems, fresh water rivers, water run-offs, storm drains or pet owners flush the feces down the toilet which then contaminates sewage water. These water sources, especial fresh water rivers and run-offs, flow into the ocean therefore infecting the water leaving the otters suseptable to contracting the infection. Also mother otters can transfer their infection to a fetus. (Cornell University of Veterinary Medicine)
A Bobcat with his prey (a rodent) showing how toxoplasmosis infects a Feline. Image taken from:!8CA87
A Bobcat with his prey (a rodent) showing how toxoplasmosis infects a Feline. Image taken from:!8CA87

What are the symptoms of an infected otter?

Of course it is much more difficult to know the symptoms of toxoplasmosis in otters, unfortunatly they are unable to communicate with us but scientists have observed some odd behaviors from infected otters. These syptoms include but are not limted to convulsions/seisures, spontanious abortions, still births, severe brain damage in off-spring, brain inflammation, severe depression, swollen lyphnodes, loss of body movement cotrol and death. (National Oceanic and Atmoshperic Associaltion)

How has Toxoplasmosis spread to affect marine mammals from the Arctic Circle to Australia?

Scientists believe migratory filter fish specifically the Northern anchovy is carrying and spreading the oocytes of Toxoplasmosis to many different area. ( Unraveling The Mystery of the Kitty Litter Parasite in Marine Mammals)

Statistics about how is Toxoplasmosis affecting populations of sea otters?
1. Over 42% of live california sea otters are infected
2. Over 62% over dead California sea otters are infected
3. over 17% over all sea otter deaths are attributed to Toxoplasmosis
( Unraveling the Mystery of the Kitty Liter Parasite in Marine Mammals)

How can we help stop this deadly parasite?
Their are two very important things that can be done to prevent more sea otters; Keep cats indoors so they can not affect fresh running water if they are carrying the toxoplasmosis parasite and do not flush cat feces down the toilet, instead throw the feces away in tightly tied biodegradable plastic bag.


1. "Toxoplasmosis in Cats." Cornell University of Veterinary Medicine. 8 Apr. 2008. 29 Apr. 2009 <>

2. "Whats Killing California Sea Otters?" Sea Otter Alliance. Summer 2009. The Regents of the University of California. 17 Apr. 2009 <>.

3. "Paracites in Cats Killing Sea Otters." National Oceanic and Atmospheric Association. 21 Jan. 2003. NOAA. 1 May 2009 <>.

4.Nguyen, Christopher. Toxoplasmosis. 2007. Standford University. 13 Apr. 2009 <>.

5. Tortora, Gerard J., Berdell R. Funke, and Christine L. Case. Microbiology an Introduction. 9th ed. San Fransisco: Pearson Education Inc. publishing as Benjamin Cummings, 2007.

6. American Society for Microbiology. "Unravelling The Mystery Of The Kitty Litter Parasite In Marine Mammals." ScienceDaily 5 June 2008. 25 May 2009 <­ /releases/2008/06/080602103404.htm>