Eggs are again excreted with fecaes and enter fresh water courses where they are ingested by fresh water snails. In contrast, the definitive host for flatworms or flukes are land mammals like foxes, dogs and cats. Fish can also harbour live worms that penetrate the gut and these are often visible in the flesh. The larvae then bore through the intestinal wall and enter the muscle tissue where they are encapsulated and can survive for long periods. The larvae are eaten by small crustaceans like prawn, crabs and shrimp and in turn these are eaten by squid and fish. These hosts shed eggs in their faeces which hatch into larvae in the water. The definitive host for fish roundworms are marine mammals like seals and dolphins and birds that feed on fish like cormorants and seagulls. How do fish get infected?ДЇish get infected with parasites when they feed on intermediate hosts. Fish flatworms or flukes, on the other hand, are normally associated with fresh water fish in temperate and warm waters. Fish roundworms are associated with salt water fish from all areas of the seas, whereas fish tapeworm, tends to come from fresh water fish in cold waters. Are fresh water and salt water fish involved?Д«oth fresh water and salt water fish are a potential source of human infection with parasites. Human infections caused by fish tapeworm are most commonly caused by the genus Diphylloborothrium. The most common flatworms or flukes involved in human infection are liver fluke worms belonging to the family Opisthorchiidae and some species of intestinal fluke worms belonging to the Heterophyidae and Echinostomatidae families. There are three types of fish parasites of public health importance roundworms (nematodes), flatworms or flukes (trematodes) and tapeworms (cestodes).ДЇrom a human infection perspective, the most common roundworms are from the family of Anisakidae and include AnisakisВ spp., Pseudoterranova spp., PhocascarisВ spp., and ContracaecumВ spp. Which parasites can humans catch from fish? Their presence may or may not cause health effects in the host animal. Generally they cannot survive outside of their host.

Parasites are small animals that require one or more host animals in order to complete their life-cycle.

Roundworms and hookworms in humans