INCREASEDCONTRACAECUM OSCULATUMINFECTION IN BALTIC COD (GADUS MORHUA) LIVERS (1982–2012) ASSOCIATED WITH INCREASING GREY SEAL (HALICHOERUS GRYPHUS) POPULATIONS

Abstract

ABSTRACT:Grey seals (Halichoerus gryphus), the main final host of the gastric parasitic nematode Contracaecum osculatum in the Baltic, have recently recolonized the southwestern Baltic Sea. This colonization could lead to an increase in prevalence and intensity of third-stage larvae of C. osculatum in livers of Baltic cod (Gadus morhua), which serve as transport host for this helminth. We performed a parasitologic study of cod in spring 2012 and compared the results with previously unpublished data from 1982/1983. Additionally, grey seals were counted annually from 2000 to 2011 at three haul-out sites in the southwestern Baltic. Of 97 cod livers examined in the 1982/1983 survey, 22% harbored C. osculatum larvae, whereas 55.1% of the examined cod livers (n5185) were infected in 2012; the mean intensity and mean abundance increased from 4.3 and 0.9 to 20.2 and 11.1, respectively. Molecular identification (PCR) confirmed the identity of the larvae. The grey seal population increased markedly during the 12-yr period. We suggest that the elevated parasitism of cod livers is associated with the successful re-establishment of grey seals in the southwestern Baltic.

Host size-dependent anisakid infection in Baltic cod Gadus morhua associated with differential food preferences

“…These crustaceans become infected when they feed on nematode larvae released from the parasite eggs delivered by seal. A dominance of adult C. osculatum in Baltic grey seal stomachs was previously documented by Skrzypczak et al (2014) and Lunneryd et al (2015), and the increase of fish infections during the last decades may be caused by the rapidly expanding grey seal population (Haarder et al 2014). Several fish species are able to obtain infection when ingesting the first intermediate hosts, and the present field study documented that more than 10% of the Baltic sprat investigated was infected by up to 8 parasite larvae per fish, which is a higher infection level than previously reported.…”

“…During recent years a marked increase in the infection level of third-stage larvae of Contracaecum osculatum and Pseudoterranova decipiens in Baltic cod has been observed (Perdiguero-Alonso et al 2008, Buchmann & Kania 2012, Haarder et al 2014, Mehrdana et al 2014, Nadolna & Podolska 2014. This development has been noted during a period with a marked increase of the grey seal Halichoerus grypus population (Haarder et al 2014). These pinnipeds are final hosts for both C. osculatum and P. decipiens (Marcogliese et al 1996, McClelland 2002, Mattiucci & Nascetti 2008, Skrzypczak et al 2014, Lunneryd et al 2015.…”

“…It is divided into an eastern and western stock with a mixing zone around the island of Bornholm (Bagge et al 1994, Hüssy et al 2016. During recent years a marked increase in the infection level of third-stage larvae of Contracaecum osculatum and Pseudoterranova decipiens in Baltic cod has been observed (Perdiguero-Alonso et al 2008, Buchmann & Kania 2012, Haarder et al 2014, Mehrdana et al 2014, Nadolna & Podolska 2014. This development has been noted during a period with a marked increase of the grey seal Halichoerus grypus population (Haarder et al 2014).…”

Environmental variables and definitive host distribution: a habitat suitability modelling for endohelminth parasites in the marine realm

“…host specificity) and human zoonotic hazardous potential923242526. The results of various studies indicate that there is a direct relationship between the prevalence and abundance of anisakid nematodes in their (paratenic) intermediate hosts and the occurrence and population size of their vertebrate definitive hosts (see McClelland27 and references therein) suggesting their host specificity to be the main external ecological attribute that determines both their range size and local abundance, and thus, influencing the epidemiology of human anisakiasis infections272829.…”

Anthropogenics: Human Influence on Global and Genetic Homogenization of Parasite Populations

“…Recently, it was noted that the reduction of Contracaecum in cod that was observed 20 yr ago because of a decrease in the host population in the Baltic Sea, has been reversed. Haarder et al (2014) documented an increase in Contracaecum osculatum infections in Baltic cod (Gadus morhua) livers , but this was in association with a notable increase in the grey seal (Halichoerusgrypus) population.…”