![Tilapia galilaea](https://loka.nahovitsyn.com/56.jpg)
Landsberg (1989) claimed that heavy infections by Contracaecum larvae had become a problem for the tilapia sector since 1982. Later on, Landsberg (1989) reported that Contracaecum larval infections are common in the Israeli pond-cultured tilapia hybrids, with observations in tilapia of 200–350 g of up to 12 worms, which could reach a length of 6 cm and 2–3 mm in diameter, inhabited the pericardial cavity, and remained unencysted ( Table 1). In Israel, Paperna (1964) published the earliest report of Contracaecum larvae infecting fish he described morphologically five types of Contracaecum larvae from various fish species in different water bodies ( Table 1).
![tilapia galilaea tilapia galilaea](http://autosoft.com.br/tilapeiro/tilapias/Tilapia17.jpg)
Among others, Moravec (2009) carried out experimental trials to better understand the life cycle of Contracaecum rudolphii, by assessing the possible direct transmission of this parasitic species through the ingestion of eggs and free-living larvae with or without passing through paratenic (metaparatenic) invertebrate and fish hosts. Despite this general information on the life cycle, some researchers have described different patterns based on experimental infection with some Contracaecum species (i.e. Several species of piscivorous birds and mammals inhabiting marine, brackish or freshwater environments act as definitive hosts by ingesting parasitized fish ( Shamsi, 2007).
![tilapia galilaea tilapia galilaea](http://www.reiseberichte-blog.com/wp-content/uploads/2010/07/FrischGefangenerTilapia.jpg)
Either eggs or larvae can be ingested by a wide variety of aquatic invertebrates which act as intermediate hosts ( Mozgovoi et al., 1965 Semenova, 1971, Semenova, 1979 Norris and Overstreet, 1976), although their role in the natural transmission to fish is still unclear ( Anderson, 2000), and a large number of fish species as second intermediate/paratenic hosts. Shamsi (2019) summarized the general life cycle as follows: eggs are shed in water by the definitive hosts, they embryonate into first-stage larvae (L1) inside eggs and then further develop and molt into L2. The life cycle is complex and has yet to be fully clarified for most of the reported species. The genus Contracaecum consists of complexes of sibling species which parasitize piscivorous birds, principally of the family Pelecanidae ( Landsberg, 1989 Mattiucci et al., 2010), Phalacrocoracidae, Ardeidae and others ( Shamsi, 2019). Further analyses combining morphological and molecular approaches are required on adult specimens collected from piscivorous birds living in the same area to support the identification of a potentially new species. multipapillatum complex and was provisionally named C. In this study, molecular and morphological analyses place the possible new species in the C.
![tilapia galilaea tilapia galilaea](http://www.israquarium.co.il/FishPhoto/Sarotherodon%20galilaeus%20galilaeus.jpg)
Genetic analysis of internal transcribed spacer rDNA and cox2 mtDNA showed high similarity to unidentified Contracaecum larvae detected in several fish species in Ethiopia, Egypt and Kenya. A combined (morphological and molecular) approach revealed that both infected fish species were parasitized by the same species of Contracaecum, although larvae in hybrid tilapia were localized in the pericardial cavity whereas in red drum, they were observed in the abdominal cavity. Prevalence of infection in hybrid tilapia and red drum was 53.8% and 40.9%, respectively. In 2019–2020, hybrid tilapia ( Oreochromis aureus x Oreochromis niloticus) and red drum ( Sciaenops ocellatus), farmed in polyculture were found to be heavily infected with nematodes referable to Contracaecum larvae. In Israel, Contracaecum larvae have been described morphologically in several fish species however, none of these descriptions were supported by molecular tools. Contracaecum larvae infecting farmed fish and fishery products are economically important causing market rejection in massive infection and may have zoonotic potential. Nematodes belonging to the genus Contracaecum (family: Anisakidae) are heteroxenous parasites with a complex life cycle.
![Tilapia galilaea](https://loka.nahovitsyn.com/56.jpg)