Investigation of mortalities associated with Salmonella spp. infection in wildlife on Tiritiri Matangi Island in the Hauraki Gulf of New Zealand

Prevalence of Salmonella spp. in translocated wild reptiles and effect of duration of quarantine on their body condition

AIMS

To assess the prevalence of carriage of Salmonella spp. in wild reptiles translocated from multiple locations to a single island, and determine changes in their body condition (BC) during quarantine.

METHODS

Between 2007 and 2009, six endemic reptile species (Oligosoma aeneum, O. moco, O. ornatum, O. smithi, Dactylocnemis pacificus, and Woodworthia maculata) were caught from several locations in the northern North Island of New Zealand. Reptiles were held in quarantine for 14-41 days while being tested for carriage of Salmonella spp. Morphometric data were collected, and scaled body mass index for each species was calculated to determine changes in BC during the quarantine.

RESULTS

Of 221 individuals tested 12 (5%) were positive for Salmonella spp. All 12 were shore skinks (O. smithi; n = 30), with a test prevalence of 0.4 (95% CI = 0.25-0.58). Eleven were carrying Salmonella enterica Warragul and one S. enterica Mississipi. There was no difference in BC at the start of quarantine of shore skinks between those that tested negative and those that tested positive for Salmonella spp. (p = 0.184). Reptiles that were quarantined for 15-20 days (three species) lost 3-5% of BC (mean proportional change 0.03-0.05), while those quarantined for >30 days increased BC by 3-13% (mean proportional change 0.03-0.13). All animals except the one individual positive for S. Mississippi were translocated to the recipient island, while the latter was returned to the source site.

CONCLUSIONS AND CLINICAL RELEVANCE

The prevalence of Salmonella spp. carriage in the translocated reptiles was low overall and consistent with other records of Salmonella spp. in wild New Zealand reptiles. However, the prevalence of 0.4 in shore skinks is the highest recorded in this species. In addition to time required for health-screening, we recommend that duration of quarantine should include time to allow animals to recover from captive stress and to provide an opportunity to increase their BC before release.

Evidence of the role of free-living birds as disseminators of Salmonella spp

ABSTRACT This study aimed to review aspects of Salmonella spp. in free-living birds and their potential as disseminators for domestic animals, man, and the environment. Isolation of Salmonella spp. have been reported in several species of wild birds from Passeridae and Fringillidae, among other avian families, captured in countries of North America and Europe, where Salmonella ser. Typhimurium is the most frequently reported serotype. The presence of pathogens, including Salmonella, may be influenced by several factors, such as diet, environment, exposure to antibiotics, infection by pathogenic organisms and migration patterns. Researches with wild birds that live in urbanized environment are important, considering that birds may participate in the transmission of zoonotic pathogens, which are more prevalent in cities due to the human activity. Based on the information collected, this article concludes that wild birds are still important disseminators of pathogens in several geographic regions and may affect man, domestic animals, and other birds.

Wildlife diseases in New Zealand: recent findings and future challenges

Our knowledge of diseases in New Zealand wildlife has expanded rapidly in the last two decades. Much of this is due to a greater awareness of disease as a cause of mortality in some of our highly threatened species or as a limiting factor to the successful captive rearing of intensely managed species such as hihi (Notiomystis cincta), kiwi (Apteryx spp.) and kakapo (Strigops habroptilus). An important factor contributing to the increase of our knowledge has been the development of new diagnostic techniques in the fields of molecular biology and immunohistochemistry, particularly for the diagnosis and epidemiology of viral and protozoan diseases. Although New Zealand remains free of serious exotic viruses there has been much work on understanding the taxonomy and epidemiology of local strains of avipox virus and circoviruses. Bacterial diseases such as salmonellosis, erysipelas and tuberculosis have also been closely investigated in wildlife and opportunist mycotic infections such as aspergillosis remain a major problem in many species. Nutritional diseases such as hyperplastic goitre due to iodine deficiency and metabolic bone disease due to Ca:P imbalance have made significant impacts on some captive reared birds, while lead poisoning is a problem in some localities. The increasing use of wildlife translocations to avoid the extinction of threatened species has highlighted the need for improved methods to assess the disease risks inherent in these operations and other intensive conservation management strategies such as creching young animals. We have also become more aware of the likelihood of inbreeding suppression as populations of many species decrease or pass through a genetic bottleneck. Climate change and habitat loss, however, remain the greatest threats to biodiversity and wildlife health worldwide. Temperature changes will affect our wildlife habitats, alter the distribution of disease vectors and wildlife predators, or directly harm threatened species in vulnerable localities.

Genomic Epidemiology and Management of Salmonella in Island Ecosystems Used for Takahe Conservation

Translocation and isolation of threatened wildlife in new environments may have unforeseen consequences on pathogen transmission and evolution in host populations. Disease threats associated with intensive conservation management of wildlife remain speculative without gaining an understanding of pathogen dynamics in meta-populations and how location attributes may determine pathogen prevalence. We determined the prevalence and population structure of an opportunistic pathogen, Salmonella, in geographically isolated translocated sub-populations of an endangered New Zealand flightless bird, the takahe (Porphyrio hochstetteri). Out of the nine sub-populations tested, Salmonella was only isolated from takahe living on one private island. The apparent prevalence of Salmonella in takahe on the private island was 32% (95% CI 13-57%), with two serotypes, Salmonella Mississippi and Salmonella houtenae 40:gt-, identified. Epidemiological investigation of reservoirs on the private island and another island occupied by takahe identified environmental and reptile sources of S. Mississippi and S. houtenae 40:gt- on the private island. Single nucleotide polymorphism analysis of core genomes revealed low-level diversity among isolates belonging to the same serotype and little differentiation according to host and environmental source. The pattern observed may be representative of transmission between sympatric hosts and environmental sources, the presence of a common unsampled source, and/or evidence of a recent introduction into the ecosystem. This study highlights how genomic epidemiology can be used to ascertain and understand disease dynamics to inform the management of disease threats in endangered wildlife populations.

A Comparison of Disease Risk Analysis Tools for Conservation Translocations

Conservation translocations are increasingly used to manage threatened species and restore ecosystems. Translocations increase the risk of disease outbreaks in the translocated and recipient populations. Qualitative disease risk analyses have been used as a means of assessing the magnitude of any effect of disease and the probability of the disease occurring associated with a translocation. Currently multiple alternative qualitative disease risk analysis packages are available to practitioners. Here we compare the ease of use, expertise required, transparency, and results from, three different qualitative disease risk analyses using a translocation of the endangered New Zealand passerine, the hihi (Notiomystis cincta), as a model. We show that the three methods use fundamentally different approaches to define hazards. Different methods are used to produce estimations of the risk from disease, and the estimations are different for the same hazards. Transparency of the process varies between methods from no referencing, or explanations of evidence to justify decisions, through to full documentation of resources, decisions and assumptions made. Evidence to support decisions on estimation of risk from disease is important, to enable knowledge acquired in the future, for example, from translocation outcome, to be used to improve the risk estimation for future translocations. Information documenting each disease risk analysis differs along with variation in emphasis of the questions asked within each package. The expertise required to commence a disease risk analysis varies and an action flow chart tailored for the non-wildlife health specialist are included in one method but completion of the disease risk analysis requires wildlife health specialists with epidemiological and pathological knowledge in all three methods. We show that disease risk analysis package choice may play a greater role in the overall risk estimation of the effect of disease on animal populations involved in a translocation than might previously have been realised.