Schistosoma hippopotami

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Schistosoma hippopotami
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Trematoda
Order: Diplostomida
Family: Schistosomatidae
Species:
S. hippopotami
Binomial name
Schistosomatidae hippopotami
Thurston 1961

Schistosoma hippopotami is a species of digenetic trematode that belongs to the genus of blood flukes (Schistosoma) that is found in sub-Saharan Africa. [1] It primarily infects African hippopotamuses (Hippopotamus anphibius) and has a more limited host range compared to other Schistosoma species.

Contents

Adult parasites have only been found in the heart, aorta, and multiple veins and arteries of the hippopotamuses. [2] It has been suggested that the hippopotamus is the definitive host of S. hippopotami. [3]

S. hippopotami was found in hippopotamuses in the Queen Elizabeth National Park in Western Uganda, along with S. edwardiense . These two species make up the S. hippopotami clade due to the fact that they are the only two Schistosoma species that infect hippopotamuses. The understanding of the existence of this clade brings the thought that this clade could be basal to all African and several Asian species of Schistosoma. [4]

Taxonomy

Schistosoma hippopotami is part of the S. hippopotami clade, along with S. edwardiense. This clade belongs to the taxonomic group of S. mansoni .

Many scientists [5] first believed that S. hippopotami was not its own species. These researchers believed that S. hippopotami was a version of S. masoni or S. rohaini. However, further studies [6] [7] [8] have helped prove that S. hippopotami was its own species

Something that was not fully understood was where the S. hippopotami clade fit on Schistosoma's phylogenic tree. It was discovered that there was a reason why this clade did not fit well with the other species. This was because of how this clade belonged at the base of most Schistosoma species. This new location implies that there could be a connection between Schistosoma and hippos. This discovery shows the importance of revisiting the standard group-based classification of schistosomes. [4]

Morphology

Schistosomes, unlike other trematodes, have separate sexes, often with significant differences between male and female worms. [8]

Schistosoma hippopotami pair (Thurston, 1961) Schistosoma hippopotami pair JPThurston.png
Schistosoma hippopotami pair (Thurston, 1961)

The adult worms are typically 1–2 cm long with a cylindrical body that features two suckers, one at either end, a tegument as a body covering, a blind-ending digestive tract, and male-female-specific reproductive organs. [9] Males are significantly larger than females and typically have a ventral groove called the gynaecophoric canal. This canal holds the longer and thinner females. [10] The process in which the adult male worm holds the adult female worm is called in copula and is when they are paired. [11]

When first identifying S. hippopotami as a species, Thurston made some simple identifications about the female and male morphologies of S. hippopotami. The female is typically shorter than the male; she has an ovary that is shaped in an oval and situated in the anterior third of her body; the eggs have a subterminal spine; and there is typically a single egg found in the uterus. The male has an indistinct number of testes but is believed to be about four, and the intestinal caeca does not reunite to form a common caecum but instead anastomoses for very short distances posteriorly. [1]

Physiology

Movement

The muscular system of schistosomes primarily consists of non-striated muscles. This movement is made possible through coordinated activities involving the suckers, which are the key attachment organs. Schistosomes have two cup-shaped suckers, one oral and one ventral. Both suckers are characterized by having a uniform structure and often being equipped with sensory feelers called papillae. [12]

Sensory

The nervous system consists of paired cerebral ganglia, which are located posterodorsal to the pharynx area. The cerebral ganglia are interconnected by a broad transverse commissure. The longitudinal nerve cords extend anteriorly and posteriorly. These nerve cords typically have three anterior and three posterior pairs. [12] These nerves play a crucial role in transmitting sensory information, which includes two distinct sensory organ types. The first type features a bulb-like nerve ending that is projected from a pit. The second type comprises nonciliated curved papillae overlying a neuronal bulb in the tegument. [12]

Digestion

The digestive system lacks a pharynx but has two ceca that combine to form a single tube connected to an esophagus. It also has a bifid intestinal ceca and a foregut with a mouth for eating and excreting. [12] Their osmoregulatory system depends on protonephridial mechanisms with flame cells located between parenchymal cells. These cells form fine tubules that connect and create the excretory bladder, which is located in the posterior part of the body. The bladder opens by way of a terminal excretory pore. [12]

Life cycle

Schistosome life has two hosts: intermediate freshwater snails and primary mammals. The life cycle begins with parasitic eggs growing in freshwater. Larvae called miracidia hatch from the parasitic eggs and go seek out the intermediate host, the freshwater snail. [13] For each of the different species of Schistosoma, the intermediate and primary hosts are different. For example, the intermediate host for S. edwardiense, which shares a clade and primary host with S. hippopotami, is the Biomphalaria species. However, the intermediate host of S. hippopotami is still under discussion. [10]

Once inside the freshwater snail, the miracidia rapidly multiplies asexually and produces larvae called cercariae. These cercariae are released into the water in order to penetrate the permanent host, the mammal. [13] Each species has a different permanent host and can have multiple options for permanent hosts. It is interesting to note that S. hippopotami has only one permanent host. This specialization makes S. hippopotami one of the few species of Schistosoma to do that.

Once inside the mammal, the parasites grow to mature, mate sexually, and produce eggs. These eggs develop with a spiral cleavage. [14] These eggs will then be released back into the water to restart the cycle. [13]

Ecology

S. hippopotami is a parasite found in hippopotami in the Queen Elizabeth National Park in Western Uganda and in hippopotami from the Letaba River in the Kruger National Park in South Africa. [2]

Adult S. hippopotami have only been encountered in the hippopotamus cardiovascular system. There are numerous locations within the hippopotamus vascular system where they have been encountered. Examples of these locations include the heart, the aorta, the pulmonary arteries, and the posterior vena cava. [2]

Unlike other Schistosoma species that infect humans and cause schistosomiasis, S. hippopotami infections in humans have never been reported. The primary host for this parasite is the hippopotamus.

Related Research Articles

<span class="mw-page-title-main">Schistosomiasis</span> Human disease caused by parasitic worms called schistosomes

Schistosomiasis, also known as snail fever, bilharzia, and Katayama fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected. Symptoms include abdominal pain, diarrhea, bloody stool, or blood in the urine. Those who have been infected for a long time may experience liver damage, kidney failure, infertility, or bladder cancer. In children, schistosomiasis may cause poor growth and learning difficulties.

<span class="mw-page-title-main">Trematoda</span> Class of parasitic flatworms

Trematoda is a class of flatworms known as flukes or trematodes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host, where the flukes sexually reproduce, is a vertebrate. Infection by trematodes can cause disease in all five traditional vertebrate classes: mammals, birds, amphibians, reptiles, and fish.

<i>Schistosoma</i> Genus of flukes

Schistosoma is a genus of trematodes, commonly known as blood flukes. They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis, which is considered by the World Health Organization to be the second-most socioeconomically devastating parasitic disease, with hundreds of millions infected worldwide.

<span class="mw-page-title-main">Digenea</span> Class of flukes

Digenea is a class of trematodes in the Platyhelminthes phylum, consisting of parasitic flatworms with a syncytial tegument and, usually, two suckers, one ventral and one oral. Adults commonly live within the digestive tract, but occur throughout the organ systems of all classes of vertebrates. Once thought to be related to the Monogenea, it is now recognised that they are closest to the Aspidogastrea and that the Monogenea are more closely allied with the Cestoda. Around 6,000 species have been described to date.

<span class="mw-page-title-main">Monogenea</span> Class of ectoparasitic flatworms

Monogeneans, members of the class Monogenea, 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.

<i>Fasciola hepatica</i> Species of fluke

Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans, and is transmitted by sheep and cattle to humans all over the world. The disease caused by the fluke is called fasciolosis or fascioliasis, which is a type of helminthiasis and has been classified as a neglected tropical disease. Fasciolosis is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite's metacercariae encysted on plants. F. hepatica, which is distributed worldwide, has been known as an important parasite of sheep and cattle for decades and causes significant economic losses in these livestock species, up to £23 million in the UK alone. Because of its relatively large size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species. The closest relative of Fasciola hepatica is F. gigantica. These two flukes are sister species; they share many morphological features and can mate with each other.

<span class="mw-page-title-main">Schistosomatidae</span> Family of flukes

Schistosomatidae is a family of digenetic trematodes with complex parasitic life cycles. Immature developmental stages of schistosomes are found in molluscs and adults occur in vertebrates. The best studied group, the blood flukes of the genus Schistosoma, infect and cause disease in humans. Other genera which are infective to non-human vertebrates can cause mild rashes in humans.

<span class="mw-page-title-main">Trematode life cycle stages</span>

Trematodes are parasitic flatworms of the class Trematoda, specifically parasitic flukes with two suckers: one ventral and the other oral. Trematodes are covered by a tegument, that protects the organism from the environment by providing secretory and absorptive functions.

Schistosoma japonicum is an important parasite and one of the major infectious agents of schistosomiasis. This parasite has a very wide host range, infecting at least 31 species of wild mammals, including nine carnivores, 16 rodents, one primate (human), two insectivores and three artiodactyls and therefore it can be considered a true zoonosis. Travelers should be well-aware of where this parasite might be a problem and how to prevent the infection. S. japonicum occurs in the Far East, such as China, the Philippines, Indonesia and Southeast Asia.

<i>Schistosoma mansoni</i> Species of fluke

Schistosoma mansoni is a water-borne parasite of humans, and belongs to the group of blood flukes (Schistosoma). The adult lives in the blood vessels near the human intestine. It causes intestinal schistosomiasis. Clinical symptoms are caused by the eggs. As the leading cause of schistosomiasis in the world, it is the most prevalent parasite in humans. It is classified as a neglected tropical disease. As of 2021, the World Health Organization reports that 251.4 million people have schistosomiasis and most of it is due to S. mansoni. It is found in Africa, the Middle East, the Caribbean, Brazil, Venezuela and Suriname.

<span class="mw-page-title-main">Swimmer's itch</span> Itchy skin lesions due to infection by water-borne parasitic flatworms

Swimmer's itch, cercarial dermatitis or schistosome dermatitis is a short-term allergic contact dermatitis occurring in the skin of humans that have been infected by water-borne schistosomes, a type of flatworm. It is common in freshwater, brackish and marine habitats worldwide. The incidence of this condition may be increasing, although this may be attributed to better monitoring and reporting. Nevertheless, the condition is considered to be an emerging infectious disease.

<i>Schistosoma intercalatum</i> Species of fluke

Schistosoma intercalatum is a parasitic worm found in parts of western and central Africa. There are two strains: the Lower Guinea strain and the Zaire strain. S. intercalatum is one of the major agents of the rectal form of schistosomiasis, also called bilharzia. It is a trematode, and being part of the genus Schistosoma, it is commonly referred to as a blood-fluke since the adult resides in blood vessels.

<i>Schistosoma haematobium</i> Species of fluke

Schistosoma haematobium is a species of digenetic trematode, belonging to a group (genus) of blood flukes (Schistosoma). It is found in Africa and the Middle East. It is the major agent of schistosomiasis, the most prevalent parasitic infection in humans. It is the only blood fluke that infects the urinary tract, causing urinary schistosomiasis, and is the leading cause of bladder cancer. The diseases are caused by the eggs.

<i>Schistosoma malayensis</i> Species of fluke

Schistosoma malayensis is a schistosome parasite. It was first described in 1988 in Peninsular Malaysia and appears to be a zooenotic infection. The species is named after the country of Malaysia. The natural vertebrate host is van Müller's rat. The intermediate hosts are aquatic snails, Robertsiella kaporenisis. Among Robertsiella kaporenisis are two other Roberstiella species.

Schistosoma indicum is a species of digenetic trematode in the family Schistosomatidae. The parasite is widespread in domestic animals in India and other Asian countries.

<span class="mw-page-title-main">Cestoda</span> Class of flatworms

Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, known as tapeworms. Their bodies consist of many similar units known as proglottids—essentially packages of eggs which are regularly shed into the environment to infect other organisms. Species of the other subclass, Cestodaria, are mainly fish infecting parasites.

Schistosoma mekongi is a species of trematodes, also known as flukes. It is one of the five major schistosomes that account for all human infections, the other four being S. haematobium, S. mansoni, S. japonicum, and S. intercalatum. This trematode causes schistosomiasis in humans.

<i>Schistosoma spindale</i> Species of fluke

Schistosoma spindale is a species of digenetic trematode in the family Schistosomatidae. It causes intestinal schistosomiasis in the ruminants.

<span class="mw-page-title-main">Bivitellobilharzia nairi</span> Species of fluke

Bivitellobilharzia nairi is a species of trematodes, part of the family Schistosomatidae. This is a fairly new identified endoparasite that was found in 1945 by Mudaliar and Ramanujachari, who first recorded the parasite in India. Researchers collected fecal samples of the Indian rhinoceros and were startled to find B. nairi eggs.

Schistosoma bovis is a two-host blood fluke, that causes intestinal schistosomiasis in ruminants in North Africa, Mediterranean Europe and the Middle East. S. bovis is mostly transmitted by Bulinus freshwater snail species. It is one of nine haematobium group species and exists in the same geographical areas as Schistosoma haematobium, with which it can hybridise. S. bovis-haematobium hybrids can infect humans, and have been reported in Senegal since 2009, and a 2013 outbreak in Corsica.

References

  1. 1 2 Thurston, J. P (1961). "Schistosomes from Hippopotamus amphibius L. I. The morphology of Schistosoma hippopotami sp.nov". Parasitology . 53: 49–54.
  2. 1 2 3 Kruger, F. J.; Hamilton-Attwell, V. L.; Joubert, P. H.; Visser, P. S. (1988). "The Tegument of Schistosoma Hippopotami from Hippopotamus amphibius in the Kruger National Park". Onderstepoort Journal of Veterinary Research . 55: 153–155.
  3. ↑ Standley, C. J.; Mugisha, L.; Dobson, A. P.; Stothard, J. R (2012). "Zoonotic schistosomiasis in non-human primates: past, present and future activities at the human–wildlife interface in Africa". Journal of Helminthology . 86: 131–140.
  4. 1 2 Morgan, J. A. T.; Randall, J.; Kazibwe, F.; Mkoji, G. M.; Loker, E. S. (2003). "A newly-identified lineage of Schistosoma". International Journal for Parasitology . 33: 977–985.
  5. ↑ Pitchford, R. J.; Visser, P. S. (1981). "Schistosoma Weinland, 1858 From Hippopotamus amphibius Linnaeus, 1758 in the Kruger National Park". Onderstepoort Journal of Veterinary Research . 48: 181–184.
  6. ↑ Fripp, P. J. (1981). "Non-specific esterase isoenzymes of adult schistosomes from the hippopotamus (Hippopotamus amphibius)". Onderstepoort Journal of Veterinary Research . 48: 257.
  7. ↑ Després, L.; Kruger, F. J.; Imbert-Establet, D.; Adamson, M. L. (1995). "ITS2 Ribosomal RNA Indicates Schistosoma hippopotami is a Distinct Species". International Journal for Parasitology . 25: 1509–1514.
  8. 1 2 Loker, E. S.; Brant, S. V. (2006). "Diversification, dioecy and dimorphism in schistosomes". Trends in Parasitology . 22: 521–528.
  9. ↑ Lyon (2012). "IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Volume 100B: A Review of Human Carcinogens". International Agency for Research on Cancer : 371–384. doi: 10.1093/occmed/kqs011 . ISSN   0962-7480.
  10. 1 2 Rollinson, D.; Southgate, V. R. (1987). "The genus Schistosoma: A Taxonomic Appraisal". The Biology of Schistosomes: From Genes to Latrines : 1–49.
  11. ↑ Erasmus, D. A. (1987). "The Adult Schistosome: Structure and Reproductive Biology". The Biology of Schistosomes: From Genes to Latrines : 51–82.
  12. 1 2 3 4 5 Fried, B.; Haseeb, M. A. (1991). "Platyhelminthes: Aspidogastrea, Monogenea, and Digenea". Microscopic Anatomy of Invertebrates. Vol. 3. pp. 141–209.
  13. 1 2 3 Newlan, M. L. (2019). "Schistosomiasis: Life Cycle, Diagnosis, and Control". Current Therapeutic Research . 91: 5–9.
  14. ↑ Jurberg, A. D.; Gonçalves, T.; Costa, T. A>; Mattos, A. C. A.; Pascarelli, B. M.; Manso, P. P. A.; Ribeiro-Alves, M.; Pelajo-Machado, M.; Peralta, J. M.; Coeloho, P. M. Z.; Lenzi, H. L. (2009). "The embryonic development of Schistosoma mansoni eggs: proposal for a new staging system". Development Genes and Evolution . 219: 219–234.
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