A Multi-Institutional Collaboration to Understand Neoplasia, Treatment and Survival of Snakes

Abstract

This multi-institutional collaborative study of neoplasia in snakes reviewed medical records of snakes at each facility to determine species prevalence, survival, and methods of treatment. Complete species numbers of snakes were also collected at each facility. In total, 65 species, 133 snakes, and 149 unique neoplasias were included in this study. Affected species, age, sex, and their tumor prevalence, tumor type and location, metastasis, treatment, and survival data are reported. The highest species-specific tumor prevalence was in Common or Northern Watersnakes (Nerodia sipedon) (30.8%, n = 4 of 13), Eastern Diamond-Backed Rattlesnakes (Crotalus adamanteus) (26.3%, n = 5 of 19), and Timber rattlesnakes (Crotalus horridus) (22.7%, n = 5 of 22). Malignant tumors predominated (86.6%, n = 129 of 149) with soft tissue sarcomas being the most common (30.2%, n = 45 of 149). Snakes with malignant neoplasia, metastases, or indeterminate presence of metastases were statistically more likely to die from their neoplasms than snakes having either benign neoplasia or no diagnosed metastases (p < 0.05). Gender, taxonomic family, and species of those evaluated did not significantly affect the outcome of snakes with neoplasia. Only 27.1% (n = 36 of 133) of snakes received a reported form of treatment and, for those treated, surgical excision was the most common treatment modality. There was not a significant difference in outcome based on treatment; however, surgery and chemotherapy were associated with death from a cause other than their tumor.

Cancer prevalence is related to body mass and lifespan in tetrapods and remarkably low in turtles

“…Since species with fewer necropsies may be less reliable, we also calculated the percentage of species with ≥5 and ≥10 necropsies. Out of the total dataset, species with ≥5 necropsies comprised 44% of amphibians, 51% of birds, 29% of crocodilians, 63% of mammals, 38% of squamates (57% with Duke et al (2022) data), and 20% of turtles in our dataset ( Appendix Table 2 ). Species with ≥10 necropsies comprised 34% of birds, 39% of mammals, and 31% of squamates (14% without Duke et al (2022) data) ( Appendix Table 8 ).…”

“…The databases for Allwetter, ZOOM Erlebniswelt, and Birmingham Zoo were all local databases while Rotterdam Zoo data was obtained through local paper reports and the Species360 Zoological Information Management System (ZIMS) with Rotterdam Zoo’s authorization. We also incorporated the mammalian necropsy reports from Boddy et al (2020a) and a dataset of neoplasia (benign or malignant) in snakes from Duke et al (2022). The dataset of Duke et al (2022) is based on cancer prevalence calculated from the number of biopsies and necropsies on the total number of individuals (live and dead) of each species housed at a given time at participating institutions in the study.…”

“…We also incorporated the mammalian necropsy reports from Boddy et al (2020a) and a dataset of neoplasia (benign or malignant) in snakes from Duke et al (2022). The dataset of Duke et al (2022) is based on cancer prevalence calculated from the number of biopsies and necropsies on the total number of individuals (live and dead) of each species housed at a given time at participating institutions in the study. Since this prevalence was partly based on live individuals and not strictly on necropsy reports, as was the rest of our data, we performed subsequent analyses both with and without the data from Duke et al (2022).…”

“…The data were further curated to include only species that could be matched with a published phylogeny for their group (see below) and those species for which at least one life history trait (lifespan and/or body mass) could be found. Finally, two species, Rousettus aegyptiacus (mammal) and Thamnophis radix (squamate from Duke et al (2022)) had more than 500 necropsies and were removed from the dataset as they prevent convergence in downstream comparative phylogenetic statistical analysis (see below).…”

“…Here we present the first study comparing cancer prevalence within and between tetrapods, which comprises all the extant major vertebrate groups except fish. We obtain necropsy data, including cancer incidence, from mammals, birds, amphibians, turtles, crocodilians, and squamates (lizards and snakes) from multiple zoos as well as from previous publications (Boddy et al, 2020a; Duke et al, 2022). Using the largest dataset to date for most tetrapod groups, we then analyze cancer prevalence within each group in relation to phylogeny, variation in body mass and lifespan among species, and intrinsic cancer risk estimated from species life history traits.…”