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Introduction: Echinococcus (E.) equinus is a cestode with a 2-host life cycle, with carnivores as definitive
hosts, shedding eggs with the feces, and equines as intermediate hosts with hydatid cysts
forming mainly in the liver and lung.
Materials and Methods: A 17-year old Connemara horse with an oromaxillary sinus fistula and
chronic colitis was euthanized with poor prognosis. The horse had a history of long-term corticosteroid-
therapy. Necropsy identified several well-demarcated, grey-white cysts of up to 5 cm in
diameter in the liver parenchyma, filled with clear, amber-colored liquid containing particles of less
than 1 mm in diameter (hydatid sand). These cysts were further investigated by histopathology and
polymerase chain reaction (PCR).
Results: At necropsy, additional smaller cysts of up to 1 cm in diameter were visible in the liver
and also in the lung. Histopathology revealed a tri-layered appearance of the cysts with an outer
connective tissue capsule followed by a PAS-positive, hyaline acellular layer and an inner germinal
membrane. The cysts contained few free protoscolices indicating the presence of Echinococcus
spp. PCR product sequencing revealed complete identity with E. equinus 12S rRNA and Cytochromoxidase
Conclusion: The present case indicates that although E. equinus infections are still considered rare,
they have emerged to our previously unaffected latitude. They pose a potential risk with dogs being
fed with raw horse-meat or –liver in terms of the BARF (Biologically Appropriate Raw Foods)-diet
which has gained increasing popularity. These dogs may potentially become reservoirs for E. equinus,
a risk which should be considered.