Cascade of ecological consequences for West Nile virus transmission when aquatic macrophytes invade stormwater habitats

Abstract

Artificial aquatic habitats are ubiquitous in anthropogenic landscapes and highly susceptible to colonization by invasive plant species. Recent research into the ecology of infectious diseases indicates that the establishment of invasive plant species can trigger ecological cascades which alter the transmission dynamics of vector-borne pathogens that imperil human health. Here, we examined whether the presence or management of two invasive, emergent plants, cattails (Typha spp.) and phragmites (Phragmites australis), in stormwater dry detention basins (DDBs) alter the local distribution of vectors, avian hosts, or West Nile virus (WNV) transmission risk in an urban residential setting. Mosquitoes and birds were surveyed at 14 DDBs and paired adjacent residential sites. During the study period, emergent vegetation was mowed by site managers in three DDBs. In the absence of vegetation management, the overall abundance and species composition of both adult vectors and avian hosts differed between residential and DDB habitats; however, WNV entomological risk indices were equivalent. Communal bird roosts composed primarily of three species, European Starlings (Sturnus vulgaris), Red-winged Blackbirds (Agelaius phoeniceus), and Common Grackles (Quiscalus quiscula), representing a broad range of WNV reservoir competence, were observed at half (three out of six) of the DDBs containing unmanaged stands of phragmites; however, their presence was associated with a lower seasonal increase in vector infection rate. Conversely, mowing of emergent vegetation resulted in a significant and sustained increase in the abundance of WNV-infected vectors in DDBs and the increase in risk extended to adjacent residential sites. These findings indicate that management of invasive plants in DDBs during the growing season can increase, while presence of communal bird roosts can decrease, WNV transmission risk.

Effects of Detritus on the Mosquito Culex pipiens: Phragmites and Schedonorus (Festuca) Invasion Affect Population Performance

“…Larger adults that emerged from microcosms with S. arundinaceus were likely exposed to much greater microbial food, while the higher nutrient concentrations fouled the water, as indicated by a thick microbial film that coated the water surface ( personal observation ), presumably causing lethally toxic conditions for a proportion of the larvae. These results are consistent with previous laboratory and field studies of the effects of detritus species and resultant food resources on mosquito performance (e.g., [10,11,15,73]), including those that have demonstrated increased survival and abundances from fresh compared to senescent detritus [14,36]. S. arundinaceus also leached higher tannin-lignin concentrations than other detritus species, reaching a maximum of 40 mg/L over the study duration.…”

“…Fewer studies have examined the effects of detritus type on larval mosquito performance in ground pool habitats, but at least one study has shown that the mowing of invasive Phragmites australis and Typha spp. around the perimeters of stormwater detention ditches dramatically increased abundances of larval mosquitoes in the ditches and adults infected with West Nile virus (WNV) in adjacent resident areas [36].…”

Invasive alien plant species: Their impact on environment, ecosystem services and human health

“…IAPS in the aquatic environments also have human health implications (Plaza et al, 2018;Stone et al, 2018). The prominent aquatic IAPS like Phragmites australis and Typha assist in the colonization and multiplication of vector-borne pathogens, particularly West Nile virus (MacKay et al, 2016) (Table 2). Eichhornia crassipes (water hyacinth) is also a high risk IAPS, helping in the spread of schistosomiasis (Mazza et al, 2014;Gezie et al, 2018;Stone et al, 2018).…”

Review: Toward management of urban ponds for freshwater biodiversity

“…Plant communities in urban ponds include a large proportion of non-native species, including invasive species (Magee et al 1999, Ehrenfeld 2008, and this has consequences for native biodiversity. These non-native plant species can trigger a cascade of altered species interactions (Mackay et al 2016). Such ecosystem changes can even lead to the changes of the transmission dynamics of vector-borne pathogens that imperil human health, such as West Nile virus in mosquitoes (Mackay et al 2016).…”

“…These non-native plant species can trigger a cascade of altered species interactions (Mackay et al 2016). Such ecosystem changes can even lead to the changes of the transmission dynamics of vector-borne pathogens that imperil human health, such as West Nile virus in mosquitoes (Mackay et al 2016). Non-native vegetation can also negatively impact vertebrate presence.…”