Potential for Waterborne and Invertebrate Transmission of West Nile Virus in the Great Salt Lake, Utah

Abstract

In November and December of 2013, a large mortality event involving 15,000 to 20,000 eared grebes (Podiceps nigricollis) occurred at the Great Salt Lake (GSL), UT. The onset of the outbreak in grebes was followed by a mortality event in >86 bald eagles (Haliaeetus leucocephalus). During the die-off, West Nile virus (WNV) was detected by reverse transcription-PCR (RT-PCR) or viral culture in the carcasses of grebes and eagles submitted to the National Wildlife Health Center. However, no activity of mosquitoes, the primary vectors of WNV, was detected by the State of Utah's WNV monitoring program. The transmission of WNV has rarely been reported during the winter in North America in the absence of known mosquito activity; however, the size of this die-off, the habitat in which it occurred, and the species involved are unique. We experimentally investigated whether WNV could survive in water with a high salt content, as found at the GSL, and whether brine shrimp, the primary food of migrating eared grebes on the GSL, could have played a role in the transmission of WNV to feeding birds. We found that WNV can survive up to 72 h at 4°C in water containing 30 to 150 ppt NaCl, and brine shrimp incubated with WNV in 30 ppt NaCl may adsorb WNV to their cuticle and, through feeding, infect epithelial cells of their gut. Both mechanisms may have potentiated the WNV die-off in migrating eared grebes on the GSL. IMPORTANCE Following a major West Nile virus die-off of eared grebes and bald eagles at the Great Salt Lake (GSL), UT, in November to December 2013, this study assessed the survival of West Nile virus (WNV) in water as saline as that of the GSL and whether brine shrimp, the major food for migrating grebes, could have played a role as a vector for the virus. While mosquitoes are the major vector of WNV, under certain circumstances, transmission may occur through contaminated water and invertebrates as food.

West Nile virus is transmitted within mosquito populations through infectious mosquito excreta

“…Multiple flaviviruses such as dengue, Usutu, Murray valley viruses [28,63,64] and alphaviruses such as Ross river virus [29] shed virions in excreta from Aedes and Culex mosquitoes, although excreta infectivity has not been tested. WNV [65] and Zika virus [60] survive in water from potential breeding sites, while all four serotypes of dengue virus remain infectious in cell media [57]. Finally, immature mosquitoes from Aedes and Culex are susceptible to Zika [60], dengue [59] and Rift valley fever viruses [66].…”

West Nile virus in crocodiles and mosquitoes in Zimbabwe

“…Lineage 2 strains are found in Africa and Europe (2). While WNV is an arbovirus, a number of studies have highlighted the potential for both mosquito and water-borne transmission (3,4)…”

Environmental Stability and Transmissibility of Enveloped Viruses at Varied Animate and Inanimate Interfaces

“…Enveloped viruses can be transmitted directly to secondary hosts through close contact with the skin, body fluids, and secretions of carriers. Some enveloped viruses can remain infective in air, − water, , food, , and inanimate surfaces − for hours to days after being released from their hosts, if the conditions are favorable. Consequently, the indirect transmission modes of viruses through the environment are plausible in the era of globalization and industrialization, despite the rarity of case reports compared to direct transmission modes. − The persistence and survivability of enveloped viruses outside the host depend highly on virus characteristics and environmental conditions .…”