Prevalence, Intensity, and Abundance of Infection and Pathogenesis Caused by Diphyllobothriosis in Vulnerable, Native Fish and Introduced Trout in Lake Panguipulli, Chile

Abstract

ABSTRACT:Diphyllobothriosis in fish from freshwater ecosystems in southern Chile was first reported in 1949. Infection by plerocercoids of Diphyllobothrium latum and Diphyllobothrium dendriticum occurs in introduced trout (Oncorhynchus mykiss) and native fish. We determined the prevalence, mean intensity, and mean abundance of seasonal infection and tissue damage produced by Diphyllobothrium spp. in native fish (Percichthys trucha, Odontesthes mauleanum, and Basilichthys australis) and introduced trout (O. mykiss) from Lake Panguipulli, Chile. Prevalence, mean intensity, and mean abundance of D. latum infection were significantly greater in trout than they were in native fish. Prevalence and mean abundance were similar in O. mauleanum and P. trucha, but they were greater than those in B. australis. Prevalence and abundance were similar among seasons between sexes for the four hosts. For all host species, except P. trucha, there was a statistically significant positive correlation between host length and the abundance of plerocercoids. Infections in muscle tissue were present in 61% of trout compared with 23% in O. mauleanum and 12% in P. trucha, suggesting a greater risk for human infection when consuming trout. In general, prevalence of infection by D. dendriticum was lower than was D. latum prevalence. Encapsulation of plerocercoids was common and severe in 71% of the trout examined. Only slight encapsulation of plerocercoids was found in the native O. mauleanum, and no encapsulation was observed in P. trucha or B. australis. The greater concentration of plerocercoids in the walls of the digestive tract of trout suggests a more-rapid immune response in trout than in native fish. The low frequency of encapsulation of plerocercoids in native fish would mean greater tissue damage in the natives than that observed in the trout because they are free to migrate among the viscera, potentially endangering these native fish populations in regions where Diphyllobothrium spp. are endemic.

Gastrointestinal Parasites and Bacteria in Free-Living South American Sea Lions (Otaria flavescens) in Chilean Comau Fjord and New Host Record of a Diphyllobothrium scoticum-Like Cestode

“…Based on present analyses of cestode strobilas, these eggs most probably belong to "Diphyllobothrium" sp. 1 and A. pacificus -the latter being quite abundant in South American sea lions (Torres et al, 2012;Hernández-Orts et al, 2013, 2015 Enterobacter aerogenes/amnigenus/asburiae/cloacae/spp.…”

“…scoticum was collected from a Southern elephant seal (M. leonina) of sub-antarctic Macquarie island (Tasmania, Australia) (Johnston, 1937). More importantly, diphyllobothriasis still represents a neglected fish-borne zoonosis not only in Chile (Mercado et al, 2010;Torres et al, 2012) but also worldwide (Curtis and Bylund, 1991;Chai et al, 2005;Scholz et al, 2009;Kuchta et al, 2015). Humans become infected by ingestion of raw or undercooked fish carrying plerocercoid-stages of Diphyllobothrium.…”

Diphyllobothriidae

“…Dibothriocephalus latus was introduced in 20th century in Chile and Argentina where it is endemic in the southern freshwater ecosystems (Neghme et al, 1950;Torres et al, 2004aTorres et al, , 2012Semenas and Úbeda, 1997;Semenas et al, 2001;Semenas, 2014;Mercado et al, 2010). In Chile, first human autochthonous case was reported in 1950 by Neghme et al Around 90 cases of dibothriocephalosis attributed to D. latus have been published of patients who have consumed trouts, Oncorhynchus mykiss or Salmo trutta, both hosts of D. latus and D. dendriticus in lakes from southern Chile (Torres et al, 1993(Torres et al, , 1998(Torres et al, , 2004aTorres et al, 2001;Mercado et al, 2010: Rosas andWeitzel, 2014).…”

“…Dibothriocephalus latus present about 17 fish host species distributed in 6 orders (Table 4). Infection in native fish from Chile, such as Galaxias spp., Percichthys trucha, Odontesthes mauleanum, and Basilichthys australis have only been observed in 2 lakes with a low intensity of infection in contrast to the high parasitic load of introduced rainbow trout (Torres et al, 1989b(Torres et al, , 1998(Torres et al, , 2004a(Torres et al, , 2012. Andersen and Gibson, 1989;De Vos and Dick, 1989;Halvorsen and Wissler, 1973;Janicki and Rosen, 1917;Kuchta et al, 2015a;Mercado et al, 2010;Revenga, 1993;Scholz et al, 2009;Thanchomnang et al, 2016;Torres et al, 1989b, 1998, 2004ab Bylund, 1972Chubb, 1980;De Vos and Dick, 1989;Gustafsson and Vaihela, 1981;Henricson, 1977;Kuchta et al, 2013;Moravec, 2004;Revenga, 1993;Thanchomnang et al, 2016;Torres, 1990;Torres et al, 1981bTorres et al, , 1989bTorres et al, , 1998Torres et al, , 2004aTorres et al, , 2012Vik, 1957 c Ando et al, 2001;Fang et al, 2015;Jeon et al, 2009;Kuchta et al, 2017;Suzuki et al, 2010;Yamane et al,1986;Yanagida et al, 2010…”

A simplified method to estimate Diphyllobothrium spp. infection in salmonids

“…When a salmonid fish eats an infected host (i.e. copepod or fish), the parasite larva penetrates the stomach of the predatory host and become encysted primarily on the stomach and intestine (Torres, Ley an & Puga 2012). In large piscivorous fish, these parasites can accumulate and reach very high intensities as infected fish may function as paratenic hosts (Curtis 1984;Knudsen & Klemetsen 1994;Kuhn et al 2016;Siwertsson et al 2016).…”