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Article

Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles (Crocodylus porosus)

1
School of Veterinary Science, University of Queensland, Gatton, Qld 4343, Australia
2
Centre for Crocodile Research, Noonamah, NT 0837, Australia
3
School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Qld 4072, Australia
4
Australian Infectious Diseases Centre, University of Queensland, St Lucia, Qld 4072, Australia
5
Berrimah Veterinary Laboratories, NT 0828, Australia
6
Queensland Health, Forensic and Scientific Services, Public Health Virology, Coopers Plains, Qld 4108, Australia
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Present address: Australian Animal Health Laboratories (CSIRO), Geelong, VIC, Australia.
Viruses 2020, 12(2), 198; https://doi.org/10.3390/v12020198
Received: 27 December 2019 / Accepted: 10 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue West Nile Virus 2019)
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. View Full-Text
Keywords: West Nile virus; saltwater crocodile; water-borne transmission West Nile virus; saltwater crocodile; water-borne transmission
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MDPI and ACS Style

Habarugira, G.; Moran, J.; Colmant, A.M.G.; Davis, S.S.; O’Brien, C.A.; Hall-Mendelin, S.; McMahon, J.; Hewitson, G.; Nair, N.; Barcelon, J.; Suen, W.W.; Melville, L.; Hobson-Peters, J.; Hall, R.A.; Isberg, S.R.; Bielefeldt-Ohmann, H. Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles (Crocodylus porosus). Viruses 2020, 12, 198. https://doi.org/10.3390/v12020198

AMA Style

Habarugira G, Moran J, Colmant AMG, 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(2):198. https://doi.org/10.3390/v12020198

Chicago/Turabian Style

Habarugira, Gervais; Moran, Jasmin; Colmant, Agathe M.G.; Davis, Steven S.; O’Brien, Caitlin A.; Hall-Mendelin, Sonja; McMahon, Jamie; Hewitson, Glen; Nair, Neelima; Barcelon, Jean; Suen, Willy W.; Melville, Lorna; Hobson-Peters, Jody; Hall, Roy A.; Isberg, Sally R.; Bielefeldt-Ohmann, Helle. 2020. "Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles (Crocodylus porosus)" Viruses 12, no. 2: 198. https://doi.org/10.3390/v12020198

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