Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

3.4.2 Epizootology
In past studies of causes of death in Wolfhounds, OS was found to be responsible for
between 21% (Bernardi 1986) and 24% (Prokopenko 1998) of deaths. In Bernardi’s
data, sex distribution of OS was almost equal, with 49.2% males and 50.8% females,
while mean age at death was 6.6 years.
There are two numbers on odds ratios available: One study found Irish Wolfhounds
to have an OR of 27.5 as compared to the overall dog population (Dorn 2002),
whereas another found an OR of 20.7 as compared to German Shepherd dogs (Ru,
Terracini et al. 1998).
Castration has been described as a risk factor for developing OS (Priester and
McKay 1980; Ru, Terracini et al. 1998; Cooley, Beranek et al. 2002). In this study,
this could be reproduced in males only during re-evaluation of the
Bernardi/Prokopenko data, in which information on castration status was available
(see chapter 5.1.5.2). In the latter two quoted studies, it was hypothesised that the
underlying mechanism may be associated with a longer bone growth period in
castrated animals, whose growth plates close at a later age than those of intact
animals.
3.4.3 Heredity and Control Measures
Despite the fact that the incidence of OS varies strongly between different dog
breeds, and although familial predispositions have been reported in the species
(Bech-Nielsen, Haskins et al. 1978), relatively little is known about its underlying
hereditary mechanisms. Involvement of mutations of the p53 tumour suppressor
gene has been described, as have changes in several proto-oncogenes (van
Leeuwen, Cornelisse et al. 1997; Johnson, Couto et al. 1998; Mendoza, Konishi et al.
1998; Ferracini, Angelini et al. 2000; Meyer, Murua Escobar et al. 2004).
Furthermore, a strong familial OS predisposition has recently been discovered in the
Scottish Deerhound (Hauck, personal communication).
Hereditary cancers are unlikely to be mediated by defective proto-oncogenes, since
their expression would interfere with the development of the embryo. On the other
hand, a hereditary cancer caused by a germ line mutation of a tumour suppressor
gene can be expected to follow a dominant pattern of inheritance, combined with
incomplete penetrance (environmental interaction and other modulating factors) and
embryonic death (lethal factor) in homozygotous individuals. However, there are
other possible mechanisms of hereditary cancer transmission as well, which can be
transmitted through mutations in different modulator genes (Ruttemann 2005).
Initial research on Osteosarcoma in Scottish Deerhounds (a breed closely related to
the Irish Wolfhound) at the universities of North Carolina and Tennessee indicated a
simple autosomal recessive mode of inheritance, but this has been shown to be too
simple an approach in the meantime (Hauck, personal communication).
Given the currently available literature, it is realistic to assume a hereditary
component of the disease, the exact nature of which remains unknown for the time
being. It therefore seems reasonable not to breed individuals diagnosed with the
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