The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion ; as a result, the food cannot be processed continuously.
Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology, bioinformatics, biochemistry, molecular biology, immunology, genetics, evolution and ecology.
Monogeneans are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they have both male and female reproductive structures.
Praziquantel (PZQ), sold under the brandname Biltricide among others, is a medication used to treat a number of types of parasitic worm infections in mammals, birds, amphibians, reptiles, and fish. In humans specifically, it is used to treat schistosomiasis, clonorchiasis, opisthorchiasis, tapeworm infections, cysticercosis, hydatid disease, and other fluke infections. It should not be used for worm infections of the eye. It is taken by mouth.
Metagonimiasis is a disease caused by an intestinal trematode, most commonly Metagonimus yokagawai, but sometimes by M. takashii or M. miyatai. The metagonimiasis-causing flukes are one of two minute flukes called the heterophyids. Metagonimiasis was described by Katsurasa in 1911–1913 when he first observed eggs of M. yokagawai in feces. M. takahashii was described later first by Suzuki in 1930 and then M. miyatai was described in 1984 by Saito.
Spirometra is a genus of pseudophyllid cestodes that reproduce in canines and felines, but can also cause pathology in humans if infected. As an adult, this tapeworm lives in the small intestine of its definitive host and produces eggs that pass with the animal's feces. When the eggs reach water, the eggs hatch into coracidia which are eaten by copepods. The copepods are eaten by a second intermediate host to continue the life cycle. Humans can become infected if they accidentally eat frog legs or fish with the plerocercoid stage encysted in the muscle. In humans, an infection of Spirometra is termed sparganosis.
Gyrodactylus salaris, commonly known as salmon fluke, is a tiny monogenean ectoparasite which lives on the body surface of freshwater fish. This leech-like parasite has been implicated in the reduction of Atlantic salmon populations in the Norwegian fjords. It also parasitises other species, including rainbow trout. G. salaris requires fresh water, but can survive in brackish water for up to 18 hours.
Nanophyetus salmincola is a food-borne intestinal trematode parasite prevalent on the Pacific Northwest coast. The species may be the most common trematode endemic to the United States.
Dactylogyrus is a genus of monogeneans in the Dactylogyridae family.
Dactylogyrus vastator is a species of hermaphroditic flatworms of class Monogenea. It is an ectoparasite of fish which infests the gills. It is problematic on fish farms. It is otherwise non-hazardous to humans.
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
Heterophyes heterophyes was discovered by Theodor Maximaillian Bilharz in 1851. This parasite was found during an autopsy of an Egyptian mummy. H. heterophyes is found in the Middle East, West Europe and Africa. They use different species to complete their complex lifestyle. Humans and other mammals are the definitive host, first intermediate host are snails, and second intermediate are fish. Mammals that come in contact with the parasite are dogs, humans, and cats. Snails that are affected by this parasite are the Cerithideopsilla conica. Fish that come in contact with this parasite are Mugil cephalus, Tilapia milotica, Aphanius fasciatus, and Acanthgobius sp. Humans and mammals will come in contact with this parasite by the consumption of contaminated or raw fish. This parasite is one of the smallest endoparasite to infect humans. It can cause intestinal infection called heterophyiasis.
Microcotyle is a genus which belongs to the phylum Platyhelminthes and class Monogenea. Species of Microcotyle are ectoparasites that affect their host by attaching themselves as larvae on the gills of the fish and grow into adult stage. This larval stage is called oncomiracidium, and is characterized as free swimming and ciliated.
Protocotyle euzetmaillardi is a species of monogenean of the family Hexabothriidae.
Lee Hong Susan Lim, more commonly known as Susan Lim, was a Malaysian parasitologist who specialised on the Monogenea, a class of parasitic flatworms which are important ectoparasites of fishes. She was the first and only Malaysian commissioner elected to the International Commission on Zoological Nomenclature. Her research was mainly in the fields of taxonomy and faunistics, although in later years, she became involved in a wide range of parasitological disciplines.
Alexandr Vladimirovich Gussev, sometimes spelled Gusev in the literature, was a Russian helminthologist specialist of monogeneans.
Louis Euzet was a French parasitologist.
Gyrodactylus leptorhynchi is a small monogenean obligate ectoparasite which parasitizes freshwater Bay Pipefish. Gyrodactylus leptorhynchi is the seventh Gyrodactylus species known to infect Bay Pipefish and the first characterized along the Pacific coast of North America. The parasite can get into captive fish environments, such as fish farms and aquariums, where it may spread in as little as 10 days. Gyrodactylus species are known to centralize on the brood pouch in male fish, this may allow. for transmission to newly hatched young. However, in Gyrodactylus leptorhynchi the parasite was found mostly found attached to body surfaces such as the dorsal fins.
Delane C. Kritsky is an American parasitologist who specialised on the Monogenea, a class of parasitic flatworms which are important ectoparasites of fishes. His research was mainly in the fields of taxonomy, faunistics, and phylogeny of the Monogenea.
Sparicotyle chrysophrii is a species of monogenean, parasitic on the gills of the marine fish. It belongs to the family Microcotylidae. Its type-host is the gilt-head seabream.
