• Are any populations ‘safe’? Unexpected reproductive decline in a population of Tasmanian devils free of devil facial tumour disease

      Farquharson, Katherine A.; Gooley, Rebecca M.; Fox, S.; Huxtable, Stewart J.; Belov, Katherine; Pemberton, David; Hogg, Carolyn J.; Grueber, Catherine E. (2018)
      Conservation management relies on baseline demographic data of natural populations. For Tasmanian devils (Sarcophilus harrisii), threatened in the wild by two fatal and transmissible cancers (devil facial tumour disease DFTD: DFT1 and DFT2), understanding the characteristics of healthy populations is crucial for developing adaptive management strategies to bolster populations in the wild....
    • Depositional diseases

      Graham, E.A.; Burns, Rachel E.; Ossiboff, R. J.; Garner, Michael M.; Jacobson, Elliott R. (CRC Press, 2021)
      This book accompanies Infectious Diseases and Pathology of Reptiles, Second Edition to cover noninfectious diseases of reptiles, meeting the need for a similar, authoritative single-source reference. The volume features color photos of normal anatomy and histology, as well as gross, light, and electron microscopic imagery of diseases. Subjects range from neoplasia, nutrition, and metabolic disease, and deposition disorders to developmental anomalies, trauma, and physical diseases, and the unique contribution of paleopathology and diseases of bone. Each chapter is supported by numerous figures, many of which are unique and cannot be found in the published literature. Readers will note that some of the chapters are based on organ system, a trend that will continue into the next edition to encompass all of the basic organ systems. This book holds the most information ever accrued into one publication on noninfectious diseases and pathology of this class of animals, providing information on every aspect of the anatomy, pathophysiology, and differential diagnosis. With up-to-the-minute data, a never-before-seen collection of images, and a stellar panel of contributors, Noninfectious Diseases and Pathology of Reptiles is the definitive resource for veterinarians, biologists, and researchers involved in the study of reptile diseases.
    • Does placental invasiveness lead to higher rates of malignant transformation in mammals?Response to: ‘Available data suggests positive relationship between placental invasion an malignancy’

      Boddy, Amy M.; Abegglen, Lisa M.; Aktipis, Athena; Schiffman, Joshua D.; Maley, Carlo C.; Witte, Carmel L. (2020)
      In our study, Lifetime cancer prevalence and life history traits in mammals, we reported the prevalence of neoplasia and malignancy in a select group of mammals housed at San Diego Zoo Global from 1964 to 1978 and 1987 to 2015 [1]. We also used these data to evaluate associations between life history traits and measures of population health. Our analysis showed placental invasiveness could not predict the proportion of animals diagnosed with neoplasia or malignancy. In a response to our article, Drs Wagner and colleagues describe a different calculation to test for a relationship between placental invasiveness and malignancy. They identified and included previously published veterinary neoplasia and malignancy data with our published dataset and suggest a positive relationship between placental invasiveness and development of malignancy (referred to as malignancy rate in Wagner and colleagues’ response). These data provided support for the Evolved Levels of Invasiveness (ELI) hypothesis [2]. We are pleased that other investigators find our data useful, and wholeheartedly agree with Drs Wagner and colleagues in the need to identify more data on cancer in a wide variety of species. Notwithstanding, this updated analysis brings up a number of topics that we would like to address....
    • Koala retrovirus diversity, transmissibility, and disease associations

      Zheng, HaoQiang; Pan, Yi; Tang, Shaohua; Pye, Geoffrey W.; Stadler, Cynthia K; Vogelnest, Larry; Herrin, Kimberly Vinette; Rideout, Bruce; Switzer, William M. (2020)
      Background Koalas are infected with the koala retrovirus (KoRV) that exists as exogenous or endogenous viruses. KoRV is genetically diverse with co-infection with up to ten envelope subtypes (A-J) possible; KoRV-A is the prototype endogenous form. KoRV-B, first found in a small number of koalas with an increased leukemia prevalence at one US zoo, has been associated with other cancers and increased chlamydial disease. To better understand the molecular epidemiology of KoRV variants and the effect of increased viral loads (VLs) on transmissibility and pathogenicity we developed subtype-specific quantitative PCR (qPCR) assays and tested blood and tissue samples from koalas at US zoos (n=78), two Australian zoos (n=27) and wild-caught (n=21) in Australia. We analyzed PCR results with available clinical, demographic, and pedigree data. Results All koalas were KoRV-A-infected. A small number of koalas (10.3%) at one US zoo were also infected with non-A subtypes, while a higher non-A subtype prevalence (59.3%) was found in koalas at Australian zoos. Wild koalas from one location were only infected with KoRV-A. We observed a significant association of infection and plasma VLs of non-A subtypes in koalas that died of leukemia/lymphoma and other neoplasias and report cancer diagnoses in KoRV-A-positive animals. Infection and VLs of non-A subtypes was not associated with age or sex. Transmission of non-A subtypes occurred from dam-to-offspring and likely following adult-to-adult contact, but associations with contact type were not evaluated. Brief antiretroviral treatment of one leukemic koala infected with high plasma levels of KoRV-A, -B, and -F did not affect VL or disease progression. Conclusions Our results show a significant association of non-A KoRV infection and plasma VLs with leukemia and other
    • Lifetime cancer prevalence and life history traits in mammals

      Boddy, Amy M.; Abegglen, Lisa M.; Pessier, Allan P.; Schiffman, Joshua D.; Maley, Carlo C.; Witte, Carmel L. (2020)
      Background Cancer is a common diagnosis in many mammalian species, yet they vary in their vulnerability to cancer. The factors driving this variation are unknown, but life history theory offers potential explanations to why cancer defense mechanisms are not equal across species. Methodology Here we report the prevalence of neoplasia and malignancy in 37 mammalian species, representing 11 mammalian orders, using 42 years of well curated necropsy data from the San Diego Zoo and San Diego Zoo Safari Park. We collected data on life history components of these species and tested for associations between life history traits and both neoplasia and malignancy, while controlling for phylogenetic history. Results These results support Peto’s paradox, in that we find no association between lifespan and/or body mass and the prevalence of neoplasia or malignancy. However, a positive relationship exists between litter size and prevalence of malignancy (P = 0.005, Adj. R2 = 0.212), suggesting that a species’ life history strategy may influence cancer vulnerabilities. Lastly, we tested for the relationship between placental invasiveness and malignancy. We find no evidence for an association between placental depth and malignancy prevalence (P = 0.618, Adj. R2 = 0.068). Conclusions Life history theory offers a powerful framework to understand variation in cancer defenses across the tree of life. These findings provide insight into the relationship between life history traits and cancer vulnerabilities, which suggest a trade-off between reproduction and cancer defenses. Lay summary Why are some mammals more vulnerable to cancer than others? We test whether life history trade-offs may explain this variation in cancer risk. Bigger, longer-lived animals do not develop more cancer compared to smaller, shorter-lived animals. However, we find a positive association between litter size and cancer prevalence in mammals.
    • Pedigree reconstruction using molecular data reveals an early warning sign of gene diversity loss in an island population of Tasmanian devils (Sarcophilus harrisii)

      McLennan, Elspeth A.; Gooley, Rebecca M.; Wise, Phil; Belov, Katherine; Hogg, Carolyn J.; Grueber, Catherine E. (2018)
      Tasmanian devils have experienced an 85% population decline since the emergence of an infectious cancer. In response, a captive insurance population was established in 2006 with a subpopulation later introduced onto Maria Island, Tasmania. We aimed to (1) examine the genetic parameters of the Maria Island population as a stand-alone site and within its broader metapopulation context, (2) assess the efficacy of assisted colonisations, and (3) inform future translocations. This study reconstructs the pedigree of 86 island-born devils using 31 polymorphic microsatellite loci. Combined molecular and pedigree analysis was used to monitor change in population genetic parameters in 4 years since colonisation. Molecular analysis alone revealed no significant change in genetic diversity, while DNA-reconstructed pedigree analysis revealed a statistically significant increase in inbreeding due to skewed founder representation. Pedigree modelling predicted that gene diversity would only be maintained above the threshold of 95% for a further 2 years, dropping to 77.1% after 40 years. Modelling alternative supplementation strategies revealed introducing eight new founders every 3 years will enable the population to retain 95% gene diversity until 2056, provided the translocated animals breed; to ensure this we recommend introducing ten new females every 3 years. We highlight the value of combining pedigree analyses with molecular data, from both a single-site and metapopulation viewpoint, for analysing changes in genetic parameters within populations of conservation concern. The importance of post-release genetic monitoring in an established population is emphasised, given how quickly inbreeding can accumulate and gene diversity be lost.