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Habarugira G, Moran J, Colmant AM, Davis SS, O’Brien CA, Hall-Mendelin S, McMahon J, Hewitson G, Nair N, Barcelon J, Suen WW, Melville L, Hobson-Peters J, Hall RA, Isberg SR, Bielefeldt-Ohmann H. Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles ( Crocodylus porosus). Viruses 2020; 12:v12020198. [PMID: 32054016 PMCID: PMC7077242 DOI: 10.3390/v12020198] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 02/10/2020] [Indexed: 12/15/2022] Open
Abstract
West Nile virus, Kunjin strain (WNVKUN) is endemic in Northern Australia, but rarely causes clinical disease in humans and horses. Recently, WNVKUN genomic material was detected in cutaneous lesions of farmed saltwater crocodiles (Crocodylus porosus), but live virus could not be isolated, begging the question of the pathogenesis of these lesions. Crocodile hatchlings were experimentally infected with either 105 (n = 10) or 104 (n = 11) TCID50-doses of WNVKUN and each group co-housed with six uninfected hatchlings in a mosquito-free facility. Seven hatchlings were mock-infected and housed separately. Each crocodile was rotationally examined and blood-sampled every third day over a 3-week period. Eleven animals, including three crocodiles developing typical skin lesions, were culled and sampled 21 days post-infection (dpi). The remaining hatchlings were blood-sampled fortnightly until experimental endpoint 87 dpi. All hatchlings remained free of overt clinical disease, apart from skin lesions, throughout the experiment. Viremia was detected by qRT-PCR in infected animals during 2–17 dpi and in-contact animals 11–21 dpi, indicating horizontal mosquito-independent transmission. Detection of viral genome in tank-water as well as oral and cloacal swabs, collected on multiple days, suggests that shedding into pen-water and subsequent mucosal infection is the most likely route. All inoculated animals and some in-contact animals developed virus-neutralizing antibodies detectable from 17 dpi. Virus-neutralizing antibody titers continued to increase in exposed animals until the experimental endpoint, suggestive of persisting viral antigen. However, no viral antigen was detected by immunohistochemistry in any tissue sample, including from skin and intestine. While this study confirmed that infection of saltwater crocodiles with WNVKUN was associated with the formation of skin lesions, we were unable to elucidate the pathogenesis of these lesions or the nidus of viral persistence. Our results nevertheless suggest that prevention of WNVKUN infection and induction of skin lesions in farmed crocodiles may require management of both mosquito-borne and water-borne viral transmission in addition to vaccination strategies.
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Affiliation(s)
- Gervais Habarugira
- School of Veterinary Science, University of Queensland, Gatton, Qld 4343, Australia;
| | - Jasmin Moran
- Centre for Crocodile Research, Noonamah, NT 0837, Australia;
| | - Agathe M.G. Colmant
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
- Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
| | - Steven S. Davis
- Berrimah Veterinary Laboratories, NT 0828, Australia; (S.S.D.); (L.M.)
| | - Caitlin A. O’Brien
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
- Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
| | - Sonja Hall-Mendelin
- Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia; (S.H.-M.); (J.M.); (G.H.); (N.N.); (J.B.)
| | - Jamie McMahon
- Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia; (S.H.-M.); (J.M.); (G.H.); (N.N.); (J.B.)
| | - Glen Hewitson
- Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia; (S.H.-M.); (J.M.); (G.H.); (N.N.); (J.B.)
| | - Neelima Nair
- Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia; (S.H.-M.); (J.M.); (G.H.); (N.N.); (J.B.)
| | - Jean Barcelon
- Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia; (S.H.-M.); (J.M.); (G.H.); (N.N.); (J.B.)
| | - Willy W. Suen
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
| | - Lorna Melville
- Berrimah Veterinary Laboratories, NT 0828, Australia; (S.S.D.); (L.M.)
| | - Jody Hobson-Peters
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
- Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
| | - Roy A. Hall
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
- Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
- Correspondence: (R.A.H.); (S.R.I.); (H.B.-O.)
| | - Sally R. Isberg
- Centre for Crocodile Research, Noonamah, NT 0837, Australia;
- Correspondence: (R.A.H.); (S.R.I.); (H.B.-O.)
| | - Helle Bielefeldt-Ohmann
- School of Veterinary Science, University of Queensland, Gatton, Qld 4343, Australia;
- School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia (C.A.O.); (W.W.S.); (J.H.-P.)
- Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
- Correspondence: (R.A.H.); (S.R.I.); (H.B.-O.)
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Abstract
Dracunculiasis is the first parasitic disease set for eradication. However, recent events related to the Dracunculus medinensis epidemiology in certain African countries are apparently posing new challenges to its eradication. Two novel facts have emerged: the existence of animal reservoirs (mainly dogs but also cats and baboons), and possibly a new food-borne route of transmission by the ingestion of paratenic (frogs) or transport (fish) hosts. Therefore, instead of being exclusively a water-borne anthroponosis, dracunculiasis would also be a food-borne zoonosis. The existence of a large number of infected dogs, mainly in Chad, and the low number of infected humans, have given rise to this potential food-borne transmission. This novel route would concern not only reservoirs, but also humans. However, only animals seem to be affected. Dracunculus medinensis is on the verge of eradication due to the control measures which, classically, have been exclusively aimed at the water-borne route. Therefore, food-borne transmission is probably of secondary importance, at least in humans. In Chad, reservoirs would become infected through the water-borne route, mainly in the dry season when rivers recede, and smaller accessible ponds, with a lower water level containing the infected copepods, appear, whilst humans drink filtered water and, thus, avoid infection. The total absence of control measures aimed at dogs (or at other potential reservoirs) up until the last years, added to the stimulating reward in cash given to those who find parasitized dogs, have presumably given rise to the current dracunculiasis scenario in Chad.
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