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Wright BR, Casteriano A, Muir YSS, Hulse L, Simpson SJ, Legione AR, Vaz PK, Devlin JM, Krockenberger MB, Higgins DP. Expanding the known distribution of phascolartid gammaherpesvirus 1 in koalas to populations across Queensland and New South Wales. Sci Rep 2024; 14:1223. [PMID: 38216613 PMCID: PMC10786818 DOI: 10.1038/s41598-023-50496-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 12/20/2023] [Indexed: 01/14/2024] Open
Abstract
Koala populations across the east coast of Australia are under threat of extinction with little known about the presence or distribution of a potential pathogen, phascolartid gammaherpesvirus 1 (PhaHV-1) across these threatened populations. Co-infections with PhaHV-1 and Chlamydia pecorum may be common and there is currently a limited understanding of the impact of these co-infections on koala health. To address these knowledge gaps, archived clinical and field-collected koala samples were examined by quantitative polymerase chain reaction to determine the distribution of PhaHV-1 in previously untested populations across New South Wales and Queensland. We detected PhaHV-1 in all regions surveyed with differences in detection rate between clinical samples from rescued koalas (26%) and field-collected samples from free-living koalas (8%). This may reflect increased viral shedding in koalas that have been admitted into care. We have corroborated previous work indicating greater detection of PhaHV-1 with increasing age in koalas and an association between PhaHV-1 and C. pecorum detection. Our work highlights the need for continued surveillance of PhaHV-1 in koala populations to inform management interventions, and targeted research to understand the pathogenesis of PhaHV-1 and determine the impact of infection and co-infection with C. pecorum.
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Affiliation(s)
- Belinda R Wright
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia.
| | - Andrea Casteriano
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia
| | - Yasmine S S Muir
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia
| | - Lyndal Hulse
- School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Sarah J Simpson
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia
| | - Alistair R Legione
- Melbourne Veterinary School, Faculty of Science, Asia Pacific Centre for Animal Health, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Paola K Vaz
- Melbourne Veterinary School, Faculty of Science, Asia Pacific Centre for Animal Health, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Joanne M Devlin
- Melbourne Veterinary School, Faculty of Science, Asia Pacific Centre for Animal Health, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Mark B Krockenberger
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia
| | - Damien P Higgins
- Sydney School of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia
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Casteriano A, Van Aggelen AR, Fischer S, Flanagan C, Marschner C, Nugent H, Huston W, Higgins DP. Evaluation of a biosecurity survey approach for contamination by Chlamydia pecorum in koala rehabilitation, field capture, and captive settings. PeerJ 2023; 11:e15842. [PMID: 37601255 PMCID: PMC10437030 DOI: 10.7717/peerj.15842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 07/12/2023] [Indexed: 08/22/2023] Open
Abstract
Transmission of Chlamydia pecorum between koalas is a potential risk in field capture or rehabilitation settings, where koalas are held in proximity to each other, or equipment is shared between animals. Given the impact of C. pecorum on koala welfare and population viability it is surprising that quarantine and disinfection protocols in a koala rehabilitation facility or capture settings have not previously been evaluated. This study aimed to evaluate an approach, based on the detection of chlamydial DNA and cell viability, to determine the degree of environmental contamination within a koala care facility. Various fomite sites associated with koala care at a koala rehabilitation facility in New South Wales, Australia were identified as potential sources of chlamydial contamination, following exposure to koalas known to be infected with C. pecorum. Fomite sites were swabbed following exposure, and again after decontamination procedures were carried out. Samples were tested for the presence of chlamydial DNA using qPCR and viability using both RT-qPCR and cell culture. From a total of 239 sampling events, 30 tested qPCR positive for chlamydial DNA, with 19 and 11 samples corresponding to pre-decontamination and post-decontamination events respectively. Detection of chlamydial DNA appeared to be most common in the examination room, especially on fomite sites in direct contact with koalas. Physical removal of chlamydial DNA, or its degradation by the elements, appeared to be more common on outdoor enclosures, clothing, and hands. Based on the cell culture assay, of the pre-decontamination samples with chlamydial DNA, eight had viable chlamydial cells, two of these at low levels. Of the post-decontamination samples with chlamydial DNA, one had a moderate number, and one had a very low number of viable chlamydial cells. RT-qPCR was unsuccessful in determining cell viability due to low yields of RNA and high levels of contaminants from the environmental samples. The outcomes of this study provide a knowledge base for the design of future biosecurity evaluation guidelines in captive and koala rehabilitation facilities. The higher incidence of chlamydial DNA detection by qPCR than viable organism highlights the need to use viability assays in similar studies. However, further investment is still needed to optimise these methods and improve sensitivity for complex environmental samples.
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Affiliation(s)
- Andrea Casteriano
- Faculty of Science/Sydney School of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia
| | - Astrid Robin Van Aggelen
- Koala Hospital Port Macquarie, Koala Conservation Australia, Port Macquarie, New South Wales, Australia
| | - Shali Fischer
- Koala Hospital Port Macquarie, Koala Conservation Australia, Port Macquarie, New South Wales, Australia
| | - Cheyne Flanagan
- Koala Hospital Port Macquarie, Koala Conservation Australia, Port Macquarie, New South Wales, Australia
| | - Caroline Marschner
- Faculty of Science/Sydney School of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia
| | - Hannah Nugent
- Faculty of Science/School of Life Sciences, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Wilhelmina Huston
- Faculty of Science, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Damien P. Higgins
- Faculty of Science/Sydney School of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia
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Chen CJ, Casteriano A, Green AC, Govendir M. A retrospective study on antibacterial treatments for koalas infected with Chlamydia pecorum. Sci Rep 2023; 13:12670. [PMID: 37542093 PMCID: PMC10403558 DOI: 10.1038/s41598-023-39832-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 07/31/2023] [Indexed: 08/06/2023] Open
Abstract
Chlamydiosis remains the leading infectious disease and is one of the key factors responsible for the dramatic reduction of koala populations in South-East Queensland (SEQ) and New South Wales (NSW) regions of Australia. Possible infection outcomes include blindness, infertility, painful cystitis, and death if left untreated. Studies have reported the treatment efficacy of chloramphenicol and doxycycline, which are the two most commonly administered treatments in diseased koalas, in clinical settings. However, none have directly compared the treatment efficacy of these antibacterials on koala survival. A retrospective study was essential to identify any relationships between the demographical information, and the animals' responses to the current treatment regimens. Associations were explored between six explanatory (sex; maturity; location; clinical signs, treatment; treatment duration) and two outcome variables (survival; post-treatment PCR). Results showed that female koalas had a statistical trend of lower odds of surviving when compared to males (OR = 0.36, p = 0.05). Koalas treated with chloramphenicol for ≥ 28 days had greater odds of surviving than when treated for < 28 days (OR = 8.8, p = 0.02), and those koalas administered doxycycline had greater odds of testing PCR negative when compared to chloramphenicol treatments (OR = 5.45, p = 0.008). There was no difference between the antibacterial treatments (chloramphenicol, doxycycline, and mixed/other) and the survival of koalas. Female koalas had greater odds of exhibiting UGT signs only (OR = 4.86, p < 0.001), and also greater odds of having both ocular and UGT clinical signs (OR = 5.29, p < 0.001) when compared to males. Of the koalas, 28.5% initially had no clinical signs but were PCR positive for C. pecorum. This study enables further understanding of the complex nature between chlamydial infection and response to antibacterial treatment.
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Affiliation(s)
- Chien-Jung Chen
- Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia.
| | - Andrea Casteriano
- Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Alexandra Clare Green
- Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Merran Govendir
- Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
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Wright BR, Jelocnik M, Casteriano A, Muir YSS, Legione AR, Vaz PK, Devlin JM, Higgins DP. Development of diagnostic and point of care assays for a gammaherpesvirus infecting koalas. PLoS One 2023; 18:e0286407. [PMID: 37262062 DOI: 10.1371/journal.pone.0286407] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/14/2023] [Indexed: 06/03/2023] Open
Abstract
The recent listing of koala populations as endangered across much of their range has highlighted the need for better management interventions. Disease is a key threat to koala populations but currently there is no information across the threatened populations on the distribution or impact of a gammaherpesvirus, phascolarctid gammaherpesvirus 1 (PhaHV-1). PhaHV-1 is known to infect koalas in southern populations which are, at present, not threatened. Current testing for PhaHV-1 involves lengthy laboratory techniques that do not permit quantification of viral load. In order to better understand distribution, prevalence and impacts of PhaHV-1 infections across koala populations, diagnostic and rapid point of care tests are required. We have developed two novel assays, a qPCR assay and an isothermal assay, that will enable researchers, clinicians and wildlife managers to reliably and rapidly test for PhaHV-1 in koalas. The ability to rapidly diagnose and quantify viral load will aid quarantine practices, inform translocation management and guide research into the clinical significance and impacts of PhaHV-1 infection in koalas.
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Affiliation(s)
- Belinda R Wright
- Koala Health Hub, Sydney School of Veterinary Science, University of Sydney, Camperdown, New South Wales, Australia
| | - Martina Jelocnik
- Centre for Bioinnovation, University of The Sunshine Coast, Sippy Downs, Queensland, Australia
| | - Andrea Casteriano
- Koala Health Hub, Sydney School of Veterinary Science, University of Sydney, Camperdown, New South Wales, Australia
| | - Yasmine S S Muir
- Koala Health Hub, Sydney School of Veterinary Science, University of Sydney, Camperdown, New South Wales, Australia
| | - Alistair R Legione
- Asia Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Parkville, Victoria, Australia
| | - Paola K Vaz
- Asia Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Parkville, Victoria, Australia
| | - Joanne M Devlin
- Asia Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Parkville, Victoria, Australia
| | - Damien P Higgins
- Koala Health Hub, Sydney School of Veterinary Science, University of Sydney, Camperdown, New South Wales, Australia
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Tsangaras K, Mayer J, Mirza O, Dayaram A, Higgins DP, Bryant B, Campbell-Ward M, Sangster C, Casteriano A, Höper D, Beer M, Greenwood AD. Evolutionarily Young African Rhinoceros Gammaretroviruses. J Virol 2023; 97:e0193222. [PMID: 37022231 PMCID: PMC10134878 DOI: 10.1128/jvi.01932-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/17/2023] [Indexed: 04/07/2023] Open
Abstract
High-throughput sequences were generated from DNA and cDNA from four Southern white rhinoceros (Ceratotherium simum simum) located in the Taronga Western Plain Zoo in Australia. Virome analysis identified reads that were similar to Mus caroli endogenous gammaretrovirus (McERV). Previous analysis of perissodactyl genomes did not recover gammaretroviruses. Our analysis, including the screening of the updated white rhinoceros (Ceratotherium simum) and black rhinoceros (Diceros bicornis) draft genomes identified high-copy orthologous gammaretroviral ERVs. Screening of Asian rhinoceros, extinct rhinoceros, domestic horse, and tapir genomes did not identify related gammaretroviral sequences in these species. The newly identified proviral sequences were designated SimumERV and DicerosERV for the white and black rhinoceros retroviruses, respectively. Two long terminal repeat (LTR) variants (LTR-A and LTR-B) were identified in the black rhinoceros, with different copy numbers associated with each (n = 101 and 373, respectively). Only the LTR-A lineage (n = 467) was found in the white rhinoceros. The African and Asian rhinoceros lineages diverged approximately 16 million years ago. Divergence age estimation of the identified proviruses suggests that the exogenous retroviral ancestor of the African rhinoceros ERVs colonized their genomes within the last 8 million years, a result consistent with the absence of these gammaretroviruses from Asian rhinoceros and other perissodactyls. The black rhinoceros germ line was colonized by two lineages of closely related retroviruses and white rhinoceros by one. Phylogenetic analysis indicates a close evolutionary relationship with ERVs of rodents including sympatric African rats, suggesting a possible African origin of the identified rhinoceros gammaretroviruses. IMPORTANCE Rhinoceros genomes were thought to be devoid of gammaretroviruses, as has been determined for other perissodactyls (horses, tapirs, and rhinoceros). While this may be true of most rhinoceros, the African white and black rhinoceros genomes have been colonized by evolutionarily young gammaretroviruses (SimumERV and DicerosERV for the white and black rhinoceros, respectively). These high-copy endogenous retroviruses (ERVs) may have expanded in multiple waves. The closest relative of SimumERV and DicerosERV is found in rodents, including African endemic species. Restriction of the ERVs to African rhinoceros suggests an African origin for the rhinoceros gammaretroviruses.
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Affiliation(s)
- Kyriakos Tsangaras
- Department of Life and Health Sciences, University of Nicosia, Nicosia, Cyprus
| | - Jens Mayer
- Institute of Human Genetics, Medical Faculty, University of Saarland, Homburg, Germany
| | - Omar Mirza
- Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin, Germany
| | - Anisha Dayaram
- Institute of Neurophysiology, Charité—Universitätsmedizin Berlin, Berlin, Germany
| | - Damien P. Higgins
- Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Benn Bryant
- Taronga Western Plains Zoo, Dubbo, New South Wales, Australia
| | | | - Cheryl Sangster
- Taronga Conservation Society Australia, Mosman, New South Wales, Australia
| | - Andrea Casteriano
- Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Dirk Höper
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald, Germany
| | - Martin Beer
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Greifswald, Germany
| | - Alex D. Greenwood
- Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research (IZW), Berlin, Germany
- School of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
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Nguyen C, Koh WL, Casteriano A, Beijerink N, Godfrey C, Brown G, Emery D, Šlapeta J. Correction to: Mosquito-borne heartworm Dirofilaria immitis in dogs from Australia. Parasit Vectors 2019; 12:85. [PMID: 30782195 PMCID: PMC6380001 DOI: 10.1186/s13071-019-3338-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Affiliation(s)
- Chloe Nguyen
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia
| | - Wei Ling Koh
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia
| | - Andrea Casteriano
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia
| | - Niek Beijerink
- University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, NSW, 2006, Australia
| | - Christopher Godfrey
- University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, NSW, 2006, Australia
| | - Graeme Brown
- School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia
| | - David Emery
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia
| | - Jan Šlapeta
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, NSW, 2006, Australia.
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Fernandez CM, Schmertmann LJ, Higgins DP, Casteriano A, Irinyi L, Mella VSA, Crowther MS, Meyer W, Krockenberger MB. Genetic differences in Chlamydia pecorum between neighbouring sub-populations of koalas (Phascolarctos cinereus). Vet Microbiol 2019; 231:264-270. [PMID: 30853132 DOI: 10.1016/j.vetmic.2019.02.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 02/04/2019] [Accepted: 02/11/2019] [Indexed: 01/09/2023]
Abstract
Chlamydiosis, caused by Chlamydia pecorum, is regarded as an important threat to koala populations. Across the koala's geographical range, disease severity associated with C. pecorum infection varies, with pathogen diversity and strain pathogenicity being likely important factors. To examine C. pecorum diversity on a sub-population level a Multi-Locus Sequence Typing (MLST) scheme, containing the housekeeping genes; gatA, oppA_3, hflX, gidA, enoA, hemN and fumC, was used to type strains from two sub-populations of koalas from the Liverpool Plains, NSW, Australia, with different disease expressions. Typing of samples from 2015 to 2017, revealed a significant association between sequence type ST 69 and clinical disease and a significant difference in sequence type frequencies between sub-populations. Sequence type ST 69 has previously been identified in both subclinical and clinically diseased koalas indicating that these markers alone are not illustrative of pathogenicity. However, recent emergence of this sequence type in a naïve population may explain the differing disease expressions. Sequence types ST 73 and ST 69 have been described in koalas across a broad geographic range, indicating multiple introduction events and/or a limited veracity of the MLST loci to explore fine scale epidemiological investigations, particularly those examining the interface between pathogenic strain and disease outcome.
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Affiliation(s)
- Cristina M Fernandez
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Hospital, Faculty of Medicine and Health, Westmead Clinical School, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia; The Westmead Institute for Medical Research, 176 Hawkesbury Road, 2145, Westmead, NSW, Australia; Sydney School of Veterinary Science, The University of Sydney, Sydney, 2006, NSW, Australia
| | - Laura J Schmertmann
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Hospital, Faculty of Medicine and Health, Westmead Clinical School, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia; The Westmead Institute for Medical Research, 176 Hawkesbury Road, 2145, Westmead, NSW, Australia; Sydney School of Veterinary Science, The University of Sydney, Sydney, 2006, NSW, Australia
| | - Damien P Higgins
- Sydney School of Veterinary Science, The University of Sydney, Sydney, 2006, NSW, Australia; Marie Bashir Institute for Emerging Infectious diseases and Biosecurity, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia
| | - Andrea Casteriano
- Sydney School of Veterinary Science, The University of Sydney, Sydney, 2006, NSW, Australia
| | - Laszlo Irinyi
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Hospital, Faculty of Medicine and Health, Westmead Clinical School, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia; The Westmead Institute for Medical Research, 176 Hawkesbury Road, 2145, Westmead, NSW, Australia
| | - Valentina S A Mella
- School of Life and Environmental Sciences, The University of Sydney, Sydney, 2006, NSW, Australia
| | - Mathew S Crowther
- School of Life and Environmental Sciences, The University of Sydney, Sydney, 2006, NSW, Australia
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Hospital, Faculty of Medicine and Health, Westmead Clinical School, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia; The Westmead Institute for Medical Research, 176 Hawkesbury Road, 2145, Westmead, NSW, Australia; Marie Bashir Institute for Emerging Infectious diseases and Biosecurity, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia
| | - Mark B Krockenberger
- Sydney School of Veterinary Science, The University of Sydney, Sydney, 2006, NSW, Australia; Marie Bashir Institute for Emerging Infectious diseases and Biosecurity, The University of Sydney, 176 Hawkesbury road, 2145, Westmead, NSW, Australia.
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Nguyen C, Koh WL, Casteriano A, Beijerink N, Godfrey C, Brown G, Emery D, Šlapeta J. Mosquito-borne heartworm Dirofilaria immitis in dogs from Australia. Parasit Vectors 2016; 9:535. [PMID: 27717406 PMCID: PMC5055658 DOI: 10.1186/s13071-016-1821-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/28/2016] [Indexed: 01/27/2023] Open
Abstract
Background Heartworm (Dirofilaria immitis) in dogs is considered endemic in Australia, but the clinical heartworm disease caused by the heartworm is rare and prevalence is low. The mainstream prevention of the heartworm is based on macrocyclic lactone (ML) administration. The aim of this study was to confirm endemism of the heartworm under current Australian conditions using a cohort of recent microfilaria-positive dogs which were on variable heartworm prevention. Methods A hotspot of canine heartworm antigen-positive and microfilaria-positive dogs has been detected recently in Queensland, Australia. Blood samples from 39 dogs from Queensland and two dogs from New South Wales were investigated for canine filarioids. Rapid antigen diagnostic tests capable of detection of D. immitis and real-time PCR for quantification and differentiation between D. immitis from Acanthocheilonema reconditum with quantification of microfilariae in canine blood samples, together with D. immitis specific real-time PCR assay, were applied to microfilaria-positive dogs. The P-glycoprotein genotype was determined to test whether Australian-sourced heartworm shared the same genetic markers as those suspected of ML-resistance in North America. Results Only D. immitis was detected in the samples from Queensland and New South Wales, Australia. Using high resolution melt real-time PCR and D. immitis specific real-time PCR, the calculated microfilaria concentration ranged from 1 to 44,957 microfilariae/ml and from 7 to 60,526 microfilariae/ml, respectively. DNA sequencing of the PCR products confirmed D. immitis. Fifteen of the examined dogs were on putative, rigorous ML prevention. For the remaining dogs, compliance with heartworm prevention was unknown or reported as inconsistent. Wild-type genotype AA-GG of the P-glycoprotein locus of D. immitis sequence has been obtained for three blood samples. Due to the incomplete history, any suggestion of a loss of efficacy of MLs must be treated as ‘remotely possible’. In the immediate future, records of preventative administration and annual antigen testing would be required to determine any problems with the efficacy of preventatives. Conclusions The prevalence of canine heartworm in Australia remains poorly understood. It is generally assumed to be low by veterinary practitioners. The localised increase in the study area confirms endemism of canine heartworm and a requirement for ongoing vigilance through annual heartworm testing to better understand the changing distribution of canine heartworm, client compliance, as well as to detect any change in ML-susceptibility. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1821-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chloe Nguyen
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia
| | - Wei Ling Koh
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia
| | - Andrea Casteriano
- Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia
| | - Niek Beijerink
- University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, 2006, New South Wales, Australia
| | - Christopher Godfrey
- University Veterinary Teaching Hospital, Sydney (UVTHS), Faculty of Veterinary Science, The University of Sydney, Evelyn Williams Building B10, Sydney, 2006, New South Wales, Australia
| | - Graeme Brown
- School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia
| | - David Emery
- School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia
| | - Jan Šlapeta
- School of Life and Environmental Sciences, Faculty of Veterinary Science, The University of Sydney, McMaster Building B14, Sydney, 2006, New South Wales, Australia.
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