Seasonal Transmission of Opisthorchis viverrini sensu lato and a Lecithodendriid Trematode Species in Bithynia siamensis goniomphalos Snails in Northeast Thailand

Abstract

Abstract. Seasonal changes play roles in the transmission success of fish-borne zoonotic trematodes (FZT). This study examined the seasonal transmission patterns of Opisthorchis viverrini sensu lato (s.l.) and a virgulate cercaria (family Lecithodendriidae) in the snail intermediate host, Bithynia siamensis goniomphalos in northeast Thailand. Snail samples were collected monthly during the rainy, cool, and hot seasons during 2012-2013 to determine the prevalence and intensity of larval trematode infections. The prevalence of O. viverrini s.l. varied significantly with season, being 0.31%, 1.05%, and 0.37% in the rainy, cool, and hot seasons, respectively (P 0.05). Similarly, the prevalence of virgulate cercariae was 3.11%, 6.80%, and 1.64% in the rainy, cool, and hot seasons, respectively (P 0.05). The intensity of larval trematode infections also varied between seasons and peaked in the hot season (P 0.05) in both species. The snails infected with O. viverrini s.l. were significantly smaller (P 0.05) and those infected with virgulate cercariae were significantly larger (P 0.05) than uninfected snails. Seasonal variation and the different sizes of B. s. goniomphalos parasitized by O. viverrini s.l. and virgulate trematodes indicate complex host-parasite interactions with important implications for the epidemiology of O. viverrini s.l.

Very low prevalence of Opisthorchis viverrini s.l. cercariae in Bithynia siamensis siamensis snails from the canal network system in the Bangkok Metropolitan Region, Thailand

“…infections in Bithynia spp. from various standing-water habitats in northeastern Thailand, Cambodia, Lao PDR, and southern Vietnam were 1.39–3.04%, 0.0–6.8%, and 0.11–1.73%, respectively [ 7 , 9 , 17 , 27 , 28 , 30 , 32 , 35 , 59 ]. With respect to the populations living in these opisthorchiasis endemic areas, their lifestyles may be associated with higher-prevalence causes than in the present study.…”

Phylogenetic relationships within the Opisthorchis viverrini species complex with specific analysis of O. viverrini sensu lato from Sakon Nakhon, Thailand by mitochondrial and nuclear DNA sequencing

“…The irrigated water from Nam Un dam finally joins with Songkram River before it drains into the Mekong River in Nakorn Phanon province. The rice paddy environment in SK is known to allow active transmission from human and animal reservoir hosts to Bithynia goniomphalos siamensis (Kiatsopit et al, 2012;Kopolrat et al, 2016;Namsanor et al, 2015). Whether different habitat types and/or other environmental attributes such as snail (Kiatsopit et al, 2013), fish and human hosts are responsible to the occurrence of this cryptic species in Sakon Nakhon is not clear.…”

“…In conclusion, by using a multi-gene sequence approach (phylogenetic and (Kiatsopit et al, 2012;Namsanor et al, 2015). Currently it is not clear whether habitat ecology, connectivity and/or land use that encourages snail host population growth or a history of chemotherapeutic control by praziquantel has affected the genetic difference of the new SK isolate.…”

Prospects and Challenges towards Sustainable Liver Fluke Control

“…Subsequent simulations incorporating these experimental data, as well as regional temperature and precipitation records, snail abundance and egg availability in the environment, provided a useful modeling framework to assess and predict seasonal transmission risk [24]. The model outputs suggested that transmission risk varies greatly over the year (see also [25,26]), with very low transmission risk during the dry season and increasing transmission risk at the onset of the rainy season (i.e. June–July) with a peak in September.…”