Dataset Information

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

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.

SUBMITTER: Habarugira G

PROVIDER: S-EPMC7077242 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Publications

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

Habarugira Gervais G Moran Jasmin J Colmant Agathe M G AMG Davis Steven S SS O'Brien Caitlin A CA Hall-Mendelin Sonja S McMahon Jamie J Hewitson Glen G Nair Neelima N Barcelon Jean J Suen Willy W WW Melville Lorna L Hobson-Peters Jody J Hall Roy A RA Isberg Sally R SR Bielefeldt-Ohmann Helle H

Viruses 20200211 2

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 = ...[more]

PMID: 32054016

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Project description:Abstract Effective management of protected species requires information on appropriate evolutionary and geographic population boundaries and knowledge of how the physical environment and life‐history traits combine to shape the population structure and connectivity. Saltwater crocodiles (Crocodylus porosus) are the largest and most widely distributed of living crocodilians, extending from Sri Lanka to Southeast Asia and down to northern Australia. Given the long‐distance movement capabilities reported for C. porosus, management units are hypothesised to be highly connected by migration. However, the magnitude, scale, and consistency of connection across managed populations are not fully understood. Here we used an efficient genotyping method that combines DArTseq and sequence capture to survey ≈3000 high‐quality genome‐wide single nucleotide polymorphisms from 1176 C. porosus sampled across nearly the entire range of the species in Queensland, Australia. We investigated historical and present‐day connectivity patterns using fixation and diversity indices coupled with clustering methods and the spatial distribution of kin pairs. We inferred kinship using forward simulation coupled with a kinship estimation method that is robust to unspecified population structure. The results demonstrated that the C. porosus population has substantial genetic structure with six broad populations correlated with geographical location. The rate of gene flow was highly correlated with spatial distance, with greater differentiation along the east coast compared to the west. Kinship analyses revealed evidence of reproductive philopatry and limited dispersal, with approximately 90% of reported first and second‐degree relatives showing a pairwise distance of <50 km between sampling locations. Given the limited dispersal, lack of suitable habitat, low densities of crocodiles and the high proportion of immature animals in the population, future management and conservation interventions should be considered at regional and state‐wide scales.

Dataset Information

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

Publications

Mosquito-Independent Transmission of West Nile virus in Farmed Saltwater Crocodiles (<i>Crocodylus porosus</i>).

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