Parasite Groups

Monogenetic Flukes

These fascinating parasites can be found on large numbers of fresh and saline fish species, but their favourable host is the Atlantic salmon. They can be up too 2mm in length and are commonly located on the skin and in gill chambers and more rarely in the mouth and body cavities. They use hook attachments to grip the epidermis whilst feeding on the skin and gill tissue; this causes only superficial damage. More importantly they can cause epidermal ulceration after heavy feeding thus in numerous quantities can in fact cause heavy damage. They are also thought to transmit other pathogens.

Gyrodactylus salaries
The only category 1 (notifiable) monogenetic fluke recognized by UK authorities is Gyrodactylus salaries - this parasite has yet to be found in the UK. Some interesting points about this parasite is it's capability to produce via a single life cycle on one host. They are viviparous, producing live off spring, that are fully sexually mature before birth. Transmission of this parasite is usually by full contact. Although a very important parasite it is of little threat to UK coarse fish stocks at the present time.

Cestoda (Tapeworms)

There are approximately 3400 known species of tapeworm of which 800 can be found using fish as hosts. The life cycle of most cestoda does require two or three hosts, but the fish is not necessarily the definitive host; it can commonly be the intermediate or transport host. The worms are transmitted when their eggs are passed via the host's faeces then up taken by an unsuspecting individual.

The head of the worm is used to adhere the parasite within the host, usually in the intestine. To aid adherence the head of the worm consists of tentacles, hooks or suckers. The remainder of the worm consists of a series of segments that all contain their very own complete set of female and male reproductive systems. The worm gains its nutrition by directly absorbing across the cavity wall. Cestodas can cause alterations in enzyme and hormonal levels and disrupt reproduction. Additionally nutritional deficiencies are common in fish hosting tapeworms that commonly results in suppressed growth.
Four types of worm are of interst to the freshwater fisheries manager:

Atractolytocestus huronensis (hosts - carp) Bothriocephalus acheilognathi (host - carp)
Monobothrium wageneri (host - tench) Ligula intestinalis (host - cyprinid sp.)