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Exposure and impacts of lead (Pb) in Scandinavian brown bears (Ursus arctos)
Lead (Pb) is a toxic, non-essential element known for its negative effects on
human, animal and environmental health. Previous studies have shown that free-ranging Scandinavian brown bears (Ursus arctos) have blood Pb at concentrations that would cause concern in humans. However, no studies have been carried out to investigate the health effects of Pb in this population. This thesis determines the gaps of knowledge concerning Pb exposure and its health effects in wild mammals and uses both free-ranging and captive Scandinavian brown bears to investigate 1) Pb exposure and if any commonly used blood variables are correlated with Pb concentration, 2) how Pb is distributed in different tissues and if any potential histopathological changes are present, 3) if Pb concentration is affected by hibernation.
The findings of this thesis show that while many wild mammalian species are exposed to Pb, there are significant knowledge gaps in regard to Pb exposure and its health effects in wild mammals. Two blood variables indicative of chronic kidney disease and two indicative of liver disease were correlated with Pb. Pb was present in all brown bear tissues analysed and the results suggest a body distribution similar to humans (three-compartment model). However, no histopathological changes were identified in liver, kidney or spinal cord tissues, so the definite health effects of Pb in the species are still undetermined. Pb concentration during hibernation is significantly higher than during the active state, potentially posing a higher risk of health effects in hibernating animals. When monitoring Pb exposure, studying wildlife at high trophic levels is desirable, and the Scandinavian brown bear is a good sentinel species given its varied diet and easy access to samples.
In a One Health context, Scandinavian brown bear products pose a risk to human health if consumed. The author advises against eating or selling products from the Swedish annual licensed hunt and supports the need for regulations of Pb in ammunition and in wild/game products to protect the consumers
Herpesvirus skin disease in free-living common frogs Rana temporaria in Great Britain
Infectious disease is a significant driver of global amphibian declines, yet despite this, relatively little is known about the range of pathogens that affect free-living amphibians. Recent detection of the tentatively named Ranid herpesvirus 3 (RHV3), associated with skin disease in free-living common frogs Rana temporaria in Switzerland, helps to address this paucity in knowledge, but the geographic distribution and epidemiology of the pathogen remains unclear. Syndromic surveillance for ranid herpesvirus skin disease was undertaken throughout Great Britain (GB), January 2014 to December 2016. Reports of common frogs with macroscopic skin lesions with a characteristic grey appearance were solicited from members of the public. Post-mortem examination was conducted on one affected frog found dead in 2015 at a site in England. In addition, archived samples from an incident involving common frogs in England in 1997 with similar macroscopic lesions were further investigated. Transmission electron microscopy identified herpes-like virions in skin lesions from both the 1997 and 2015 incidents. RHV3, or RHV3-like virus, was detected in skin lesions from the 2015 case by PCR and sequencing. Our findings indicate that herpesvirus skin disease is endemic in common frogs in GB, with widespread distribution at apparently low prevalence. Further research into the role of host immunity, virus latency and the significance of infection to host survival is required to better understand the epidemiology and impact of cutaneous herpesvirus infections in amphibian populations