Effects of the Herbicide Atrazine's Metabolites on Host Snail Mortality and Production of Trematode Cercariae

Abstract

Environmental stressors have the potential to greatly impact the transmission of parasites with complex, multi-host life cycles such as those of trematodes. The commonly used herbicide atrazine has been shown to affect the susceptibility of second intermediate hosts (such as larval amphibians) to trematode infection, as well as the longevity and infectivity of the free-swimming cercariae, but not eggs or the free-swimming miracidia that infect the gastropod first intermediate hosts. However, we do not know if this pesticide influences the survival of infected snails or whether it affects cercariae production within, or emergence from, these hosts. In addition, previous studies of host-parasite dynamics have only examined the parent atrazine compound, not any of the long-lasting metabolites commonly present in water bodies. Here, we report that a concentration of 0.33 µg/L of an atrazine metabolite, desethyl atrazine, increased the mortality of freshwater gastropods ( Stagnicola elodes ) infected with a gymnocephalus type of cercaria but not that of uninfected snails or those harboring a mature or dormant infection of Echinoparyphium sp. In contrast, 2 wk of exposure to desethyl atrazine did not affect the emergence of gymnocephalus cercariae from snails, although a trend for a decrease in the emergence of Echinoparyphium sp. cercariae was observed. We suggest that simultaneous trematode infection and exposure to contaminants may represent a significant combined stress to gastropods, but this is likely parasite species-specific as well as dependent on whether cercariae are being actively produced.

Noxious newts and their natural enemies: Experimental effects of tetrodotoxin exposure on trematode parasites and aquatic macroinvertebrates

“…The effects of toxic pollutants on the functional biology of aquatic parasites has been a subject of increasing interest in recent years (Koprivnikar and Walker, 2011; Marcogliese, 2005). Notably, studies of contaminants have found a reduction in the production of trematode cercariae from molluscan hosts as well as their capacity to infect downstream hosts (Cross et al, 2001; Morley et al, 2003).…”

Environmental and ecological factors driving trematode parasite community assembly in central Alberta lakes

“…Anoxic conditions have been reported as having differential effects on snail mortality in infected snails in salt marsh ecosystems ( Sousa and Gleason, 1989 ). Related to this, a given snail host species can react very differently to stress depending on the trematode that it is infected with ( Bates et al, 2011 ; Koprivnikar and Walker, 2011 ). In freshwater ecosystems, it has been noted that most gastropods are unable to withstand anaerobic conditions for more than 48 h ( Pennak, 1978 ).…”

Trematode Parasite Infection Affects Temperature Selection in Aquatic Host Snails

“…After testing, the snails were patted dry to accurately measure their weight (g) and shell diameter (cm) and then individually frozen in labeled bags for later dissections to confirm their infection status. Thawed snails were dissected to confirm infection (or not) by E. trivolvis by gently cracking the shell and carefully teasing apart the body tissue under a dissecting microscope to check for presence of rediae (Koprivnikar and Walker 2011).…”