Prevalence and drivers of blood parasitism in African penguins (Spheniscus demersus)
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University of Cape Town
In the past decade African penguin (Spheniscus demersus) populations have experienced declining population sizes of > 60% in some instances. This has primarily been attributed to shifting prey availability and competition with regional purse-seine fisheries; however, possible novel threats exacerbated by diminishing population sizes and increased stress, may also be important contributors to the regional persistence of the species. These threats include the impacts of arthropod-borne blood parasites on the health of penguin populations. While parasitism of wild penguins has been poorly studied, susceptibility to infection with blood protozoa is well established in a wide range of penguin species held in captivity. This thesis assesses the prevalence of blood parasites in wild African penguins throughout the greater Agulhas-Benguela ecosystem. Using PCR-based techniques, 317 individuals were screened for the presence of known haemoparasite species of Plasmodium, Haemoproteus and Babesia across 12 breeding colonies. Babesia infection was confirmed for 60% of wild birds sampled, but methods used did not indicate infection with either Haemoproteus or Plasmodium species. Generalised linear modelling of ecological and life history parameters suggests that Babesia prevalence is primarily driven by a colony’s distance from the mainland, decreasing significantly as distance from the mainland increases. Captive birds held at the SANCOBB rehabilitation facility in Cape Town present with both Plasmodium and Babesia species, providing the positive controls for the study. The relative scarcity of Plasmodium and Haemoproteus infection in the wild may be the result of an absence of suitable vectors and/or high post mortality in the host. Alternatively, the sensitivity of the method used requires further investigation as Plasmodium infection has been confirmed previously in penguin populations using PCR-based approaches. This study provides the first baseline estimate of blood parasitism in African penguins across their breeding range, and raises the need for further research and monitoring. The results suggest that high Babesia prevalence in African penguins may be related to (1) an ecological system of chronicexposure to infection reservoirs, such as the co-occurring cormorant and gannet populations and (2) increasing anthropogenic impacts, especially in mainland colonies. Data on blood parasitism in co-occurring seabird species is required to fully elucidate their role in Babesia infection dynamics in the region. To improve understanding and facilitate timely detection of changes in blood parasite exposure, standardised methodologies are advocated to better inform the conservation management of this iconic species.
Includes bibliographical references.
Naude, V. 2014. Prevalence and drivers of blood parasitism in African penguins (Spheniscus demersus). University of Cape Town.