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Introduction (additions)

Researchers are currently facing difficulties completely differentiating the numerous species under the Trichuris genus. When different whipworm species were discovered, the main factor used to differentiate species was the length of the spicule sheath. However, it was eventually discovered that many species had similar spicule sheath lengths. Therefore, researchers began to compare other morphologies, such as the structure or orientation surrounding female sex organs of species suspected to be similar but different. Relatively recently, studies have been conducted to differentiate similar Trichuris species based on mitochondrial DNA differences, a much more accurate method of distinction. However, there is currently a paucity of research devoted to encoding the DNA of each and every species. As a result, Trichuris species distinction is still largely based on morphological differences.

General Life Cycle:

All whipworm species have a similar general life cycle. Whipworm eggs are first ingested by the host. They eventually reach the duodenum of the small intestine, where the eggs ultimately hatch. The larva from these eggs travel into the large intestine’s cecum. For approximately four weeks, the whipworms feed on blood vessels located within the cecum. Eventually, the whipworms leave the cecum and begin to lay thousands of eggs. These unembryonated eggs are then released out of the host through feces. The process from egg ingestion to release takes approximately twelve weeks. The released eggs become embryonated and are eventually ingested by another host.

General Egg Development:

Whipworm eggs have thick, lemon-shaped, light yellow shells. Located on opposite ends of the shells are plugs that protect the eggs in unfavorable conditions such as rugged dirt and the acidic environment of the small intestine. The actual egg is covered by a vitelline membrane.

When the egg first exits the uterus of their mother, they are composed solely of yolk granules. Over a period of 72 hours, the egg undergoes mitotic division into two blastomeres that are separated by a transverse cleavage. Two additional cleavages occur within at least 96 hours so that the egg is now composed of four cells. Cellular division continues in this manner and the morula stage is reached within the next week. After a total of 21-22 days, the larva becomes fully developed and will not hatch until ingested by a host. The larva can be alive for a total of 6 months without the assistance of a host. The timeline of egg development can vary depending on the species.

Whipworms in Cats

Trichuris serrata and T. campanula are nematode parasites first discovered in domestic Brazilian cats by Dr. Otto Friedrich Bernhard von Linstow in 1879 and 1889 respectively. Since then, there have been reports of these two species in North and South America, Cuba, Australia, and the Caribbean islands.

During the early 1900’s, many considered the only legitimate feline whipworm species to be T. serrata. However, there are distinct differences between the sizes of these two species. T. serrata are slightly bigger and lay smaller eggs than T. campanula. The egg morphologies of both species are identical and have a light brown color and a lemon shape, both of which are Trichoroid characteristics. Despite this difference, studies have discovered that the best form of differentiation can be seen in the anatomy of their females. In 1975, it was discovered that female T. serrata have a fingerlike projection from the vulva while T. serrata have a longitudinal lips on that sex organ. T. serrata also have bacillary bands whereas T. campanula do not.

There are currently no clinical symptoms associated with whipworm infections in felines. Diagnosis of cats with these infections is usually through fecal flotation. To treat them, veterinarians recommend feeding the cats 50 mg/kg of fenbendazole once a day for three days. Although they are very infectious between cats, there are no recorded cases of T. serrata and T. campanula infecting humans.

Trichuris ovis

T. ovis was first discovered in 1795 and is known to infect sheep and goats. This species of whipworm can be located in any region that has the aforementioned hosts, as can be attested by the numerous reports of T. Ovis findings throughout North and South America, Australia, Europe, and Asia.

This species of whipworm is white and is known to have a long, thin neck that composes two thirds of its body, and a short, thick posterior. The male T. Orvis usually range from 53.04mm-75.08mm in length, while their female counterparts are approximately 32.03-70.19mm in length. The spicule length is 4.18-5.62mm for both genders. Both genders also have bacillary bands. T. orvis that inhabit different species of sheep or goats can have slightly different morphologies.

Like all ringworms, T. ovis primarily inhabit the host’s cecum. However, sheep and goats are rather resistant to the parasite infection and often do not experience many symptoms. If the host is heavily infected, a large portion of the blood vessels located in the cecal wall will be consumed. This eventually results in the thickening of the wall, thus preventing the portion of the large intestine from absorbing fluids causing the host to have diarrhea. This can be extremely detrimental for the host during a drought. Although sheep and goats are relatively resistant to them, T. orvis is one of the most common nematode parasites, and many of the aforementioned hosts are infected by this species of whipworm. As a result, farmers began treating infected livestock with anthelmintics, an internal pesticide, in hopes of eradicating the T. orvis. Unfortunately, there have been cases reported where the parasites are resistant to these treatments, thus prompting researchers to develop potential vaccines to combat such resistant whipworms.

Trichuris discolor

T. discolor, a species of whipworm discovered in 1906 by Dr. Otto Friedrich Bernhard von Linstow, primarily infect bovines. However, they can also infect sheep and goats. Like T. ovis, T. discolor is known to be located in any region that their hosts are located. There have been specific reports of this species being found in Japan, Indo-Pakistan, North America, etc.

Despite inhabiting the same hosts, T. discolor and T. ovis are distinct species. The size of both species are approximately the same. However, the spicule length of T. discolor is significantly shorter and ranges from 1.7-2.3mm.