Short notes of Uncommon trematodes and Cestodes

Uncommon trematodes

Alaria spp

The genus Alaria has 7 species; only  A. alata is found naturally in Europe. No human illness caused by A. alata mesocercariae (infective larvae) has been reported, but concern remains because the closely related North American species A. americana has caused illnesses among humans, including 1 death. Natural infection of cats with other Alaria spp has been reported in the United States indicating biologic differences among   Alaria spp.

Alariosis is a re-emerging zoonotic disease caused by   infection with larval stages of trematodes of the genus Alaria. Alaria spp. infections are acquired by dogs and cats via ingestion of a wide variety of intermediate or paratenic hosts (particularly frogs and snakes) that harbor immature flukes. The infection possibly was acquired by the eating of inadequately cooked frogs, which are intermediate hosts of the worm. Adult flukes, residing in the intestines of the definitive hosts, pass unembryonated eggs through the feces of the host. After two weeks, these eggs hatch in water, releasing the miracidium. They actively penetrate and develop further in a snail host.

Alaria spp. adults develop in the small intestine and are not usually associated with intestinal illness. However, migration of immature Alaria through the lungs may result in pulmonary hemorrhage and subsequent respiratory compromise. When infection levels are high, pulmonary damage and hemorrhage may lead to clinical disease. Granulomas were present in the stomach wall, lymph nodes and liver, but the worms were not identified in them. A case of fatal disease associated with systemic infection with Alaria larvae and several cases of ocular infection have been reported following ingestion of undercooked frogs legs. The causing dermatitis in humans (“swimmer’s itch”) following skin penetration.

 Diagnosis of infection by fecal examination requires concentrating the ova present in feces by sedimentation rather than flotation. Identification of isolated mesocercariae was confirmed  by PCR . The diagnosis was made by lung biopsy and confirmed at autops. Tetracyclines are considered by many to be the treatment of choice. It may be important in Asia and South America, the awareness needed where cats are occasionally consumed.

Acanthoparyphium spp

The genus  Acanthoparyphium (Digenea: Echinostomatidae) is a group of minute intestinal trematodes which parasitize the small intestine of  aquatic birds in marine areas of the Republic of Korea, Japan, USA, the Philippines, Kuwait, India, Puerto Rico, and Australia. Brackish water gastropods, bivalves, or oysters play the role of a first or second intermediate host, or both.  A. tyosenense  is the only known species belonging to Acanthoparyphium. It has been suggested that human infections with  A. tyosenense were contracted by consumption of the raw flesh of intertidal bivalves, including M. veneriformi. The prevalence of A. tyosenense metacercariae was 99.5% in naturally infected.  

The natural definitive hosts of  Acanthoparyphium are always aquatic birds, and the majority of them are migratory; some of them, like plovers, godwits, knots, and dotterels fly from Siberia to southern Australia. The second intermediate hosts of Acanthoparyphium species have been identified as intertidal mollusks, snails, and oysters. Among the human-infecting echinostomatid flukes,   Adult trematodes are generally parasitic in the digestive tract of aquatic birds. Body elongated, tapering anteriorly, and rather elliptical at the posterior end. Five hours after infection, the cercariae tails began to separate from the bodies, and the cercariae formed cysts. Mature cysts were formed  (14 days) after infection and  identified as the metacercariae of  A. tyosenense.

Adult Acanthoparyphium species attach to the jejunal mucosa and may provoke an  inflammatory response. Symptoms are variable. Some patients are asymptomatic but those with heavy worm burdens may complain vague abdominal pain and diarrhea.

Diagnosis is done by the detection of eggs in the faces, the eggs are similar to that of  F. hepatica and F. buski though smaller in size.The specific diagnosis can be made only on the recovery of adult parasites. The tegumental ultrastructure of juvenile and adult Acanthoparyphium tyosenense was observed by scanning electron microscopy. Single administrations of praziquantel is reported to be effective in small numbers of patients infected . Avoidance of eating raw snails will prevent transmission of infection in man. Dosing definitive hosts with anthelminths is the most effect method for intervening with infection rates.

Uncommon cestodes

Bertiella spp

Bertiella is a genus of tapeworm in the family Anoplocephalidae, many species of which exist as parasites of nonhuman primates. Two species of the genus, Bertiella studeri and B. mucronata, can infect humans. More than 50 cases of human infection have been recorded, and the geographic distribution of cases shows that the tapeworm exists in countries in Asia, Africa, and the Americas. Animal infection has been recorded in some provinces in China, and human bertiellosis has been recorded in Sri Lanka, Saudi Arabia, Vietnam, Japan, India , Thailand, Malaysia, and other Asian countries.  

The lifecycle of the cestode requires 2 hosts; nonhuman primates are generally the final host, while oribatid mites are the intermediate host, in which the infective cysticercoid of the cestode develops. Orbatid mites may exist in soil to maintain natural infection, and the definitive host is infected by eating or otherwise coming into contact with contaminated soil or food. Eggs and proglottids are passed in the feces of the definitive host. Oncospheres are ingested by the arthropod intermediate host. This host in nature is believed to be one or several species of oribatid mites. In the arthropod intermediate host, the oncospheres develop into cysticercoid. The definitive hosts become infected after ingesting arthropod intermediate hosts infected with cysticercoids. Adults reside in the small intestine of the definitive host where they attach to the mucosa with the aid of an unarmed scolex. Although rare, humans may also serve as definitive hosts for Bertiella spp., usually after accidentally ingesting infected mites.

Humans are infected by unconsciously swallowing infected mites, and in Mauritius, children were infected by eating guavas that had fallen on the soil. Patients are usually asymptomatic but nausea, diarrhoea, anorexia and abdominal pain sometimes occur.

Diagnosis is made by the finding of motile proglottids or, less-commonly, eggs in stool. Ova can be seen in the deposit of a formol ether/acetate concentration of the stool. praziquantel,* which is commonly used to treat infections with other intestinal tapeworms. To prevent human bertiellosis, the relationship between human cases and the natural host must be investigated.

Diplogonoporus grandis

Diplogonoporus grandis is one of human broad tapeworms residing in intestinal track. Normally this tapeworm is a parasite of sea animals such as whales, but reported from more than 200 Japanese patients in Japan, no patient is reported from the outside of Japan.

A 55-year-old man was admitted to the Nara Medical University Hospital in Japan, with the complaints of abdominal distension, tenesmus and discharging a cestode strobila. On his stool examination, eggs in oval-shape were found. Under the diagnosis of cestode infection, anthelmintic treatment with Gastrografin was performed. When 400 ml of Gastrografin was introduced into duodenal lumen through a tube, roentgenography revealed that a tape-like worm moved rapidly downwards toward descending colon

Diarrhoea,  abdominal distension, loss of weight and fatigue are the common symptoms.Under the diagnosis of cestode infection, anthelmintic treatment with Gastrografin was performed. When 400 ml of Gastrografin is introduced into duodenal lumen through a tube, roentgenography revealed that a tape-like worm can   be moved rapidly downwards toward descending colon.

To prevent Diplogonoporus grandis infection, the marine fishes particularly fish raw like butter fish and sunfish should be avoided.

Hymenolepis microstoma

Hymenolepis microstoma is an obligate parasite. It belongs to the genus Hymenolepis; tapeworms that cause hymenolepiasis. Hymenolepis microstoma, also known as the rodent tapeworm, is an intestinal dwelling parasite. H. microstoma is prevalent in rodents worldwide, but rarely infects humans.  Adult worms live in the bile duct and small intestines of mice and rats, and larvae metamorphose in the haemocoel of beetles.Worms vary from 4 to 30 cm in length, depending on the age and number of worms within the host.

The cycle begins as arthropods become intermediate hosts by ingesting the parasite eggs. Oncospheral larvae are released from the eggs and use hooks and secreted enzymes to penetrate the gut of the beetles and enter the haemocoel. In the haemocoel the larvae undergo complete cellular reorganization (i.e. metamorphosis), transforming into cysticercoid larvae in approximately 7–10 days. The larvae can remain in the cysticercoid stage in the beetle as long as the lifespan of the adult beetle (up to 3 years). Rodents can become infected when they eat arthropods, such as flour beetles (Tribolium ssp). Humans, especially children, can ingest the arthropods as well and therefore become infected via the same mechanism. Rodents, especially rats, are definitive hosts and natural reservoirs of H. microstoma. As the definitive host (rats) eats an infected arthropod, cysticercoids present in the body cavity transform into the adult worm. Juvenile worms establish in the bile duct of mice after approximately 3 days movement within the upper gastrointestinal tract. Once established in the bile duct, the worms then mature sexually and begin producing eggs within approximately 1 week. Eggs are released with mouse faeces and thus dispersal is passive - through the movement and defecation of mice. Adult worm infections in mice held under laboratory conditions persist for 6–12 months.

. Human H. microstoma infection is often asymptomatic, but abdominal pain, irritability, itching, and eosinophilia are among the existing symptoms in a few of the reported cases. Since data regarding praziquantel treatment of H. microstoma is sparse, scientists have recommended that every case and treatment of H. microstoma be reported for development of protocols and parasitological purposes.

Mathevotaenia spp.

The genus Mathevotaenia includes species that have been found parasitizing mainly mammals throughout  the world (rodents, insectivores, edentates, carnivores, marsupials, bats, and primates), with isolated reports in reptiles and birds. One case of human infection by Mathevotaenia sp. in Bangkok, Thailand. The life cycles of the species of Mathevotaenia involve insects, such as cockroaches and butterflies, as intermediate hosts in which amphicyst develop to larval cestodes or metacestodes and considered that larvacyst of amphicyst type is a synonymous of precysticercus.

Mathevotaenia chaquensisn  (Cestoda, Anoplocephalidae, Linstowiinae) from a Spiny Lava Lizard, Tropidurus spinulosus, collected in Chaco Province, Argentina, is described. The second species of Mathevotaenia described from Neotropical reptiles. The new species is mainly characterized by having a relatively small strobila, 24 mm in total length, with about 100 craspedote proglottids, and 19-24 testes per proglottid. Among the South American species of Mathevotaenia, M. argentinensis is most similar to the new species by having similar body length and number of testes, but the major differences between both species include the size of suckers, neck, proglottids, testes and egg capsules, and the shape of the genital atrium and ovary.

Bettle is used in Thailand and Malaysia for medicinal purposes through which  the Mathevotaenia species is acquired. So, humen is the only accidental host.The laboratory diagnosis can be done by identification of adult, proglottids and egg (microscopic identification of eggs in the stool). The disease can be treated with praziquantel and new case should be reported to the parasitology laboratory. Awareness to the zoonosis parasitic disease is important step to control the infection like Mathevotaenia species infection in the world

Mesocestoides spp

Mesocestoides is a parasitic tapeworm which occasionally infects dogs and cats worldwide. So, it is a genus of parasitic flatworms that has dogs, cats and some wild canids (e.g. foxes, coyotes, wolves, etc.) as final hosts. Some species affect also birds, and very seldom humans. Incidence depends on the species and the region. In some European countries more than 70% of the fox population can be infected. As a general rule it is not very frequent in dogs and cats.

Species which are known to infect dogs and cats include:

• Mesocestoides lineatus and Mesocestoides litteratus, found in Europe, Africa and Asia.
• Mesocestoides vogae (= Mesocestoides corti) and Mesocestoides variabilis, found in America.

Mesocestoides tapeworm have an unusal three-host, first intermediate hosts are arthopods, second intermediate hosts are small vertebrates and final definative hosts are cat and dog. Dogs are usually infected with the tetrathyridium larval stages acquire from ingestion of birds and other small mammals. Adults Mesocestoides develop from the tetrathyridiums within the dog's intestine and have four suckers but no hooks. Once outside the gravid segments release the proglottids or oncospheres , which are supposed to be ingested by arthropods. In the intestine of these intermediate hosts and the young larvae penetrate into their cavity (hemocoel), where they develop to cysticercoides. Small vertebrates (snakes, lizards, frogs, birds, rats, mice etc) ingest the infected arthropods and the cysticercoides are released in their gut. They migrate through the gut's wall and into various organs (mainly the lungs and the liver) and develop further to an infective larvae can reproduce asexually. The definitive host ultimately becomes infected after eating meat contaminated with tetrathyridia. Humans are not usual definitive hosts, but can serve as such after eating undercooked meat containing tetrathyridia.

Larval tetrathyridia migrated from the gut and proliferate within the peritoneal cavity, parasitizing abdominal organs and migrating as far as the inguinal canal, vaginal tunic and testis in some dogs. Clinical signs of tetrathyridiosis in dogs include peritonitis (due to intestinal perforation), ascites, anorexia, vomiting, diarrhea and tachypnea. Mesocestoides species usually parasitize humans in low numbers, causing mild gastrointestinal symptoms: nausea, diarrhea, abdominal discomfort, vomiting. Diagnosis is based on coprological identification of Mesocestoides eggs. Co-infections with other intestinal parasites is extremely common. In peritoneal tetrathyridiosis, paracentesis and ultrasonography help identify the small white cyst-like larval stages as well as the occasional intact acephalic pre-adults. PCR assays are also available to assist speciation of the parasite. Praziquantel, emodepside and fenbendazole may be used effectively for intestinal infections.There are so for no vaccines against mesocestoides tapeworm.

Raillietina celebensis

Raillietina is a genus of tapeworms that includes helminth parasites of vertebrates, mostly of birds. The genus was named in 1920 in honour of a French veterinarian and helminthologist, Louis-Joseph Alcide Railliet. Of the 37 species recorded under the genus, Raillietina celebensis is  the most important species in terms of prevalence and pathogenicity among wild and domestic birds.

Raillietina require two different hosts for a complete life cycle. The definitive hosts are mostly wild and domestic birds, and sometimes humans. The intermediate hosts are insects, such as ants and beetles. Mature eggs are released from the avian host through feaces by detaching the last gravid proglottid. The number of egg cell in each egg capsule is an identifying feature of each species. Eggs develop into larval forms called oncospheres, which are ingested by ants, and enters the alimentary canal, from where they migrates into the abdominal cavity of the insect and develops into mature cysticercoids. A cysticercoid is an inflated sphere with distinct rostellar hooks, and each species has characteristic number and size of the hooks, which correspond to those of adult worms. When the insect with infective larvae is ingested by birds, the cysticercoid is released in host by the action of digestive juices. New segments begin to form and within 3 weeks of ingestion of the host, a mature tapeworm develops. The body of an adult Raillietina is a typical tapeworm structure, composed of a series of ribbon-like body segments, gradually enlarging from the anterior end towards the posterior.

They are intestinal parasites in the definitive host. The level of their infection and clinical pathogenicity is characteristic of each species. R. cesticillus is quite harmless in terms of symptoms; whereas R. echinobothrida is highly pathogenic, and causes nodular tapeworm disease under heavy infection..Chronic infection results in diarrhoea, emaciation and anaemia, indicated by haemorrhage in the intestine. Infection is directly diagnosed by identifying proglottids in the faeces, or adult worms in the intestine upon autopsy. Broad-spectrum anthelmintics such as albendazole, fenbendazole, praziquantel, oxfendazole and niclosamide are all effective against the different species. The most effective control measure is disruption of the habitat of intermediate hosts near poultry farms.