A number of cetacean species including southern right whales, use bay area’s to calve, mate and nurse their young. In the southern cape of South Africa, these whales spend a few months between mid-August and November in these coastal regions before travelling to the Southern Ocean again. Disturbingly, increasingly more of these mammals are spotted with a variety of skin lesions. Most studies characterized the lesions specifically, although a number of microbes have been identified to be associated with lesional skin, including species representing Acinetobacter, Bacillus, Corynebacterium, Flavobacterium, Moraxella, Pseudomonas, Staphylococcus, Candida, Cryptococcus, Rhodotorula and others. Beached whales from South Africa, for example, were found to harbour Candida zeylanoides, Chaetomium globosum, Chaetomium murorum and Penicillium coprophilum in skin lesions. Even though many publications point to industrial activities as possible and probable contributing factors to these skin and other pathological conditions, the need for additional studies to provide conclusive evidence, has been expressed. Anthropogenic actions can either govern the course of a disease, or directly lead to trauma or the formation of lesions. Mostly, immuno-suppression is suspected to be one of the most critical factors contributing to the skin lesion phenomenon.

Since the dawning of the industrial revolution in the mid 1940’s, significant amounts and volumes of chemicals including pesticides have been released into the environment. These toxins are now ubiquitous with many of the most persistent ones ending up in the marine ecosystem. Moreover, these compounds are also responsible for altering the composition of the biosphere, since they bio-accumulate and magnify within food chains and therefore pose a serious threat to the health of the top predators in the oceanic environment. Similar to man, cetaceans occupy the top trophic levels of several food chains and are therefore accordingly affected by the presence of these chemicals. It is noteworthy that cetaceans are now regarded as informative indicators of ecosystem status. Immune system deficiencies, impairment of reproductive function and development, disrupted endocrine function, neurological abnormalities, behaviour abnormalities, specific organ dysfunction and cancer to name but a few, can all be attributed to a common factor - exposure to toxic and biological pollutants. For the most part, these include the persistent organic pollutants (POPs), heavy metals (trace elements), butyltins, polynuclear aromatic hydrocarbons (PAHs), plastics, oil and waste water. In addition to the above mentioned chemical pollution of the oceans, several medical studies reported skin infections from bathing in contaminated water caused by bacteria such as Aeromonas, Mycobacterium, Staphylococcus and Vibrio species. Moreover, keratinophilic fungi occur in high concentrations in sewage sludge and therefore also pose an additional risk to all mammals in urban bay areas. Such fungi are representatives of Acremonium, Aspergillus, Chrysosporium, Fusarium, Sporothrix, Trichoderma and many others. These species are known causative agents of a range of skin and systemic infections and their opportunistic nature renders immuno-compromised individuals, whether cetacean or human, at high risk of infection.

It is disquieting to witness the increased incidence of skin lesions among cetaceans which is only one of many negative impacts from anthropogenic activity and economic development on natural ecosystems. Ironically, it is apparent from the above that humans and cetaceans share a common fate regarding chemical and biological pollution. However, without shares in Wall Street and government structures, cetacean wellbeing appears to be on the short end of economic development and welfare. It is therefore evident that escalating observable signs of ecosystem degradation, such as these skin lesions, should motivate global policy makers to find sustainable solutions to counterbalance man’s negative impact on sensitive ecosystems for the benefit of all earth’s inhabitants.

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1. Mouton, M., Reeb, D., Botha, A., & Best, P. (2009). Yeast infection in a beached southern right whale (Eubalaena australis) neonate. Journal of wildlife diseases, 45(3), 692-699.
2. Reeb, D., Best, P. B., Botha, A., Cloete, K. J., Thornton, M., & Mouton, M. (2010). Fungi associated with the skin of a southern right whale (Eubalaena australis) from South Africa. Mycology, 1(3), 155-162.
3. Marnel Mouton and Alfred Botha (2012). Cutaneous Lesions in Cetaceans: An Indicator of Ecosystem Status?, New Approaches to the Study of Marine Mammals, Aldemaro Romero and Edward O. Keith (Ed.), ISBN: 978-953-51-0844-3, InTech.

Authors:
Dr. Marnel Mouton                                   Prof. Alfred Botha

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Department of Microbiology
University of Stellenbosch