[MARMAM] New publications of Toxoplasma in pinnipeds in Antarctica

Silje-Kristin Jensen skj3 at st-andrews.ac.uk
Wed Aug 22 13:10:44 PDT 2012

Dear MARMAM readers

We are pleased to announce two publications regarding the parasite *Toxoplasma
gondii* in pinnipeds in Antarctica.

Short summary of the two papers:

*Toxoplasma: a Cat-parasite in seals from Antarctica*


*Toxoplasma gondii* is a protozoan parasite that causes the disease
toxoplasmosis which is considered dangerous for pregnant women who have not
had the disease before, or people with weakened immune systems. *Toxoplasma
*is known worldwide and has also been part of the reason for increased
mortality among sea otters in the United States. Members of the cat family
are definitive hosts for this parasite, and play a key role in the
epidemiology. *Toxoplasma *may be transmitted through food or water
contaminated with oocysts (the resistant form of the parasite) from cat
faeces, or via ingestion of infected meat with resting parasites in tissue

Despite extensive worldwide surveillance in populations of both people and
wildlife, little is known about *Toxoplasma gondii* ecology in the
Antarctic region. Two recent studies, performed by scientists at the Norwegian
School of Veterinary Science, The Sea Mammal Research Unit, the British
Antarctic Survey and at the SALUVET group from Complutense University of
Madrid in Spain, have investigated the presence of this parasite in
Antarctic marine mammals. Different animal species, true seals and eared
seals, from different locations were examined. In both studies, antibodies
against *T. gondii* were found mainly in Weddell seals and Southern
elephant seals whereas a small percentage of Antarctic fur seals were
positive. Although antibodies have been found in seals in several studies
from the arctic and worldwide, these studies are the first to document the
presence of antibodies in seals from Antarctica.

The study led by Pedraza-Díaz concluded that the differences observed
between the animal species could be due to their different distribution and
migratory ranges as well as their feeding habits. There is no wild felid
fauna in Antarctica and in 1991 the Madrid Protocol on Environmental
Protection to the Antarctic banned all introduced species, including cats,
from the Antarctic to protect the native wildlife from introduced
diseases. However, felids are present in the sub-Antarctic regions, areas
within the normal distribution range of the animal species analysed here.
High seroprevalence values have been reported in feral cats in the
Kerguelen archipelago in the Sub-Antarctic region. Therefore exposure to *
Toxoplasma* might have occurred outside Antarctica. This agrees with the
higher detection rates in Southern elephant seals and Weddell seals found
here, which show wider distribution and migratory ranges.

Survival of infectious *Toxoplasma *oocysts in seawater has previously been
demonstrated, suggesting that the oocysts can survive in the marine
ecosystem of Antarctica. Since seal don’t drink water, contact through diet
is the best way of explaining the exposure. When oocysts of the parasite
come in contact with water, molluscs like shellfish, can filter these
oocysts and possibly infect the animals that eat them. At least that was
the conclusion from scientists in the United States who worked with sea
otter mortality due to toxoplasmosis. In addition, recent studies in which
anchovies were experimentally exposed to *Toxoplasma* oocysts have
indicated that migratory filter feeder fish may play a role in the
transmission of *T. gondii* in the marine environment.

Macquarie Island is an island known for sealing, science and tourism. Feral
cats have been known to inhabit the island since 1820s and have been
eradicated since the late 1990s. Little is known about the marine pathway
of Toxoplasma, and Jensen and her team suggest a marine pathway of *
Toxoplasma* oocysts. Although the presence of *Toxoplasma* has not been
investigated in the feral cats on Macquarie Island there is a possibility
that oocysts have found their way from the island across the Antarctic
conveyor belt and to Hutton Cliff where Weddell seals forage. Jensen has
suggested a similar transmission for the Arctic ecosystem in a previous
study where she found polar bear, ringed and bearded seals to be exposed to

These findings are very interesting and show how little we know about the
presence and transmission of *T. gondii *in the marine ecosystem. Further
studies are needed to provide additional information regarding how *T
gondii *may affect the Antarctic fauna.


*Jensen, S.K*., Nymo, I.H., Forcada, J., Godfroid, J., Hall, A. (2012).
Prevalence of *Toxoplasma gondii* antibodies in pinnipeds from
Antarctica.Veterinary Record doi:10.1136/vr.100848


*Rengifo-Herrera, C*., Ortega-Mora, L.M., Álvarez-García, G.,
Gómez-Bautista, M., García-Párraga, D., García-Peña, F.J., Pedraza-Díaz, S.
(2012), Detection of T*oxoplasma gondii* antibodies in Antarctic pinnipeds.
Veterinary Parasitology doi: 10.1016/j.vetpar.2012.05.020


For any questions or pdf requests please email:
Silje-Kristin Jensen: skj3 at st-andrews.ac.uk
Susana Pedraza Díaz: spedraza at vet.ucm.es

Silje-Kristin Jensen and Susana Pedraza Díaz
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