Trichuris vulpis, or the canine whipworm, is found worldwide where its hosts are present. This worm ranges from subtropical to arctic latitutdes. Definitive hosts are dogs and foxes, although T. vulpis has been reported to infect humans. Trichuriasis is associated with poor hygiene as well as proximity to shaded, moist soil, or food that may have been fecally contaminated. Therefore, Trichuris vulpis is not found in area of extreme dryness or direct sun, such as deserts. (Chandler, 1930; Dunn, et al., 2002; Otto, 1932; Spindler, 1929)
Trichuris vulpis has two distinct habitats for the different life stages of its development. Eggs released into the environment are intolerant to desiccation and therefore need a moist environment such as dirt or sand to survive. They can also survive in water such as puddles, lakes, or ponds. The eggs must be ingested by an appropriate host, which will serve as the second habitat of Trichuris vulpis. As the larvae mature inside their host, they will migrate from the small intestine to the cecum of the large intestine, where they will feed and reproduce as adults. (Anderson, 1992; Burrows, 1950; Roberts, et al., 2009)
Trichuris vulpis is a relatively small nematode with a longer, thin anterior end and a thicker posterior end, which gives it the appearance of a whip. The esophagus is located anteriorly and the reproductive and digestive processes are found posteriorly. Glandular cells called stichocytes line the esophagus of the worm and secrete juices that help it digest its food. Adult whipworms are about 6 to over 20 mm long. Whipworms do not have an excretory system, and waste materials diffuse through pores in the epithelium into the host's intestine. The whipworm's bacillary bands, a shared morphology of the genus Trichuria, are modified lateral and median hypo-dermal cords which give the appearance of bands on the anterior portion of the whipworm. Females are generally larger than males, and males have a slightly more curled tail. Males also possess a spicule, which is used in copulation. (Anderson, 1992; Burrows, 1950; Chandler, 1930; Chitwood, 1930; Gibbons, 1986; Lee and Atkinson, 1977; Roberts, et al., 2009; Sheffield, 1963)
The life cycle of the whipworm is monoxenous (living on only one kind of parasite), and it has only a definitive host. Female worms in the large intestine shed between 1,000 and 5,000 eggs per day. The unembryonated eggs are passed with the host's feces into the external environment. In soil the eggs embryonate and become infective in 15 to 30 days. Eggs are infective for about 2–3 weeks after they are deposited in the soil under proper conditions of warmth and moisture. Eggs are resistant to freezing, but do not withstand arid conditions. They may live for up to five years in the soil. After accidental ingestion by a host, the eggs hatch in the small intestine and release larvae. The larvae mature and move to the ascending colon where they become fixed with their anterior portions threaded into the mucosa of the large intestine. Females begin to oviposit 60 to 70 days after the initial infection. (Georgi, 1985; Otto, 1932)
After a male and a female whipworm have found each other, thigmotactic responses trigger copulation. The spicule of the male is inserted into the vulva of the female during copulation in order to hold the vulva open to allow ejaculatory muscles to inject sperm into the reproductive tract of the female. To find the vulva, neurons on the spicule allow the male to feel the female without damaging any of her tissue. (Gibbons, 1986)
Trichuris vulpis is dioecious. This means that there are both female and male worms, and that two indicivuals, one of each sex, must mate in order for offspring to be produced. (Roberts, et al., 2009)
Since fertilized eggs pass through the mammal host immediately upon being laid, there is no parental involvement of the female or male whipworm in the raising of their offspring.
Because their life cycle involves different environments and is dependent on host acquisition, many Trichuris vulpis eggs never reach reproductive maturity. For those that become adults, the average life expectancy is about 10 months. (Spindler, 1929)
There is no interaction between parents and offspring, since eggs that are shed are immediately excreted with the host's feces. Because the adult Trichuris vulpis lives solely inside its host, there is limited interaction with other species. Behavior of the canine whipworm is not as well known as the human whipworm, Trichuris trichuria. (Roberts, et al., 2009)
For copulation and reproduction to occur, a male and a female Trichuris vulpis must first find each other. Organisms exhibit thigmotactic behavior and may move toward or away from an object that provides a mechanical stimulus, such as a whipworm of the opposite sex. Pheromones are given off by females and serve to attract male whipworms. Species in the phylum Nematoda use sense organs, or sensilla, called papillae, amphids, and setae. Amphids are located on each side of the head and are commonly used as chemoreceptors that detect chemicals. Papillae and setae detect mechanical sensations and can therefore be described as mechanoreceptors. (Roberts, et al., 2009)
Trichuris vulpis feeds on the blood from the cecum, or large intestine, of its mammal host. A whipworm feeds with a spear-like stylet. The anterior-posterior movement of this spear is caused by the contraction of its muscular esophagus. The muscular esophagus leads to a long stichocyte esophagus and into the worm's intestine. Secretions from the stichocyte play a role in the digestion of food. (Burrows, 1950; Lee and Atkinson, 1977)
Trichuris vulpis does not have any known predators. Mortality is caused by an environment which may dry out its eggs, and the immune system of its potential host, which may kill the worm.
There are no known economic benefits of T. vulpis.
Trichuris vulpis has been known to infect humans after its eggs are accidentally ingested. Symptoms of the endoparasite range from mild to severe and include diarrhea, iron-deficiency anemia, and rectal prolapse. There have been studies that indicate a suppressed immune response to antirabies vaccination in infected puppies, suggesting that more vaccines are needed for the individual to achieve the desired level of resistance. This phenomenon might also be applicable for young children infected with Trichuris vulpis, but this effect has not been tested in humans. (Dunn, et al., 2002; Mojzisova, et al., 2007)
Trichuris vulpis is not described as having any special status.
Exposure to helminth worms can result in some acquired protection against immunological disorders. Asthma has become a growing concern for millions of people in developed nations, and it is speculated to have resulted from improved hygiene in the past hundred years. The introduction of parasites as a potential alternative therapy has gained attention. It has been hypothesized that various other immunological disorders observed in humans, such as Crohn's Disease, inflammatory bowel disease, food allergies, multiple sclerosis, and ulcerative colitis may be treated with intentional infection with helminths, including whipworms. (Falcone and Pritchard, 2005)
Alexandra DePorre (author), University of Michigan-Ann Arbor, Heidi Liere (editor), University of Michigan-Ann Arbor, John Marino (editor), University of Michigan-Ann Arbor, Barry OConnor (editor), University of Michigan-Ann Arbor, Renee Mulcrone (editor), Special Projects.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).
either directly causes, or indirectly transmits, a disease to a domestic animal
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
chemicals released into air or water that are detected by and responded to by other animals of the same species
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
an animal that mainly eats blood
scrub forests develop in areas that experience dry seasons.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
living in cities and large towns, landscapes dominated by human structures and activity.
breeding takes place throughout the year
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