| Parascaris univalens | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Ascaridida |
| Family: | Ascarididae |
| Genus: | Parascaris |
| Species: | P. univalens |
| Binomial name | |
| Parascaris univalens | |
Parascaris univalens is a parasitic ascaridoid nematode that infects the gastrointestinal tracts of equines.
P. univalens is morphologically identical to Parascaris equorum , the only other species in the genus. The species are distinguished by the number of chromosomes. [1] Karyotyping is the only way to differentiate between the two: P. univalens has one pair of chromosomes and P. equorum has two pairs. [2] However, new genomic research suggests that both Parascaris species could be the same species. [3] Both species are model organisms for chromosome organization and cell division. [4]
The species is yellow-white in color, with adults having a long body and a broad anterior end that has three shamrock-like lips. [5] Adult females can reach up to 50 cm in length and be 1–2 cm round. [6] As with other ascarid worms, P. univalens is known to increase in size as it ages. [7]
These worms are host-specific to equines and cannot infect humans or other animals. [5]
P. univalens is a model organism for chromatin diminution. [6]
A protein layer surrounding most of the eggs enables them to stick to vertical surfaces and even to the hair and udder or a mare. Foals are especially susceptible to infection because they like to explore the environment with their mouths, and when they are weaning off their mothers. [6]
Females will lay eggs that are then passed out of the equine through their feces, but those eggs are not infectious yet. Only under the right environmental conditions can the eggs become infectious; which is an egg that contains a coiled, third stage larva. This process can happen within two weeks after being passed out of the equine. [6]
As an infectious egg is ingested it loses its protective coat when passing through the digestive system. The larva will emerge from the egg in the small intestine and proceed to pierce the intestinal lining. The larva will travel through the lymphatic system from the small intestine to the liver, which can usually take 2 to 7 days after the initial infection. The larvae continue moving through the functional tissue, or parenchyma, of the liver, causing inflammatory problems. Around two weeks post-infection stage 3 larva will have reached the lungs. They will live in the lungs for another two weeks before finally erupting out of the alveolar membranes to enter the airways. Four weeks post-infection is where they are coughed up into the pharynx and swallowed, returning to the small intestine to mature and reproduce. Adult P. univalens may live in the small intestine for many months and lay eggs anywhere from 90 –110 days after the initial infection. Eggs are then shed through the equines feces where the process can continue. [6]
Young equines, or foals, are most at risk of being infected whereas adults have built a tolerance to the nematode. Some signs and symptoms that the foals are infected with P. univalens include a lack of energy, coughing and nasal discharge. [2] Some cases include impaired growth of foals and worm impaction can cause the small intestine to rupture. [2] Intestinal impactions usually occur in foals and around four to ten months of age, additionally impactions can be diagnosed with an abdominal ultrasound. [7]
Standard treatment for Parascarsis involves using drugs that induce paralysis in the worms, this makes them detach from the intestines and allow the horse to pass them. In some cases, surgery can be the only option to remove the worms. [7]
Since older foals develop immunity to P. univalens, treatment is advised at two to five months old. [2] A recent study on ascarids in Europe has discovered that P. univalens have started becoming resistant to a standard antihelmintic medication, pyrantel, whereas fenbendazole is still proven to be effective at removing the worms. [2] Other medications frequently used include ivermectin and moxidectin. The use of such medications can cause issues if given to a foal later than suggested. Larger and a higher quantity of worms being treated with paralytic medicine can lead to impaction in the foal. [7]
Trichuris trichiura, Trichocephalus trichiuris or whipworm, is a parasitic roundworm that causes trichuriasis when it infects a human large intestine. It is commonly known as the whipworm which refers to the shape of the worm; it looks like a whip with wider "handles" at the posterior end.
Strongyloides stercoralis is a human pathogenic parasitic roundworm causing the disease strongyloidiasis. Its common name in the US is threadworm. In the UK and Australia, however, the term threadworm can also refer to nematodes of the genus Enterobius, otherwise known as pinworms.
Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever in the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain, and diarrhea. Children are most commonly affected, and in this age group the infection may also cause poor weight gain, malnutrition, and learning problems.
Toxocariasis is an illness of humans caused by the dog roundworm and, less frequently, the cat roundworm. These are the most common intestinal roundworms of dogs, coyotes, wolves and foxes and domestic cats, respectively. Humans are among the many "accidental" or paratenic hosts of these roundworms.
Anisakis (a·nuh·saa·keez) is a genus of parasitic nematodes that have life cycles involving fish and marine mammals. They are infective to humans and cause anisakiasis. People who produce immunoglobulin E in response to this parasite may subsequently have an allergic reaction, including anaphylaxis, after eating fish infected with Anisakis species.
Ascaris suum, also known as the large roundworm of pig, is a parasitic nematode that causes ascariasis in pigs. While roundworms in pigs and humans are today considered as two species with different hosts, cross-infection between humans and pigs is possible; some researchers have thus argued they are the same species. Ascariasis is associated with contact to pigs and pig manure in Denmark.
Ascaris is a genus of parasitic nematode worms known as the "small intestinal roundworms", which is a type of parasitic worm. One species, Ascaris lumbricoides, affects humans and causes the disease ascariasis. Another species, Ascaris suum, typically infects pigs. Parascaris equorum, the equine roundworm, is also commonly called an "ascarid".
Ascaridia galli is a parasitic roundworm belonging to the phylum Nematoda. Nematodes of the genus Ascaridia are essentially intestinal parasites of birds. A. galli is the most prevalent and pathogenic species, especially in domestic fowl, Gallus domesticus. It causes ascaridiasis, a disease of poultry due to heavy worm infection, particularly in chickens and turkeys. It inhabits the small intestine, and can be occasionally seen in commercial eggs.
Spirometra erinaceieuropaei is a parasitic tapeworm that infects domestic animals and humans. The medical term for this infection in humans and other animals is sparganosis. Morphologically, these worms are similar to other worms in the genus Spirometra. They have a long body consisting of three sections: the scolex, the neck, and the strobilia. They have a complex life cycle that consists of three hosts, and can live in varying environments and bodily tissues. Humans can contract this parasite in three main ways. Historically, humans are considered a paratenic host; however, the first case of an adult S. erinaceieuropaei infection in humans was reported in 2017. Spirometra tapeworms exist worldwide and infection is common in animals, but S. erinaceieuropaei infections are rare in humans. Treatment for infection typically includes surgical removal and anti-worm medication.
Ancylostoma duodenale is a species of the roundworm genus Ancylostoma. It is a parasitic nematode worm and commonly known as the Old World hookworm. It lives in the small intestine of hosts such as humans, cats and dogs, where it is able to mate and mature. Ancylostoma duodenale and Necator americanus are the two human hookworm species that are normally discussed together as the cause of hookworm infection. They are dioecious. Ancylostoma duodenale is abundant throughout the world, including Southern Europe, North Africa, India, China, southeast Asia, some areas in the United States, the Caribbean, and South America.
Uncinaria stenocephala is a nematode that parasitizes dogs, cats, and foxes as well as humans. It is rare to find in cats in the United States. Uncinaria stenocephala is the most common canine hookworm in cooler regions, such as Canada and the northern regions of the US, where it can be found primarily in foxes (40%). U. stenocephala is also one of the most common hookworms in the UK, called the northern hookworm, however it has a rather low prevalence. U. stenocephala is also considered to be zoonotic hookworms because they live in animals but can be transmitted to humans.
Toxocara canis is a worldwide-distributed helminth parasite of dogs and other canids. The name is derived from the Greek word "toxon," meaning bow or quiver, and the Latin word "caro," meaning flesh. They live in the small intestine of the definitive host. In adult dogs, the infection is usually asymptomatic but may be characterized by diarrhea. By contrast, massive infection with Toxocara canis can be fatal in puppies, causing diarrhea, vomiting, an enlarged abdomen, flatulence, and poor growth rate.
Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. T. leonina is an ascarid nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts of T. leonina include canids and felines (cats), while the intermediate hosts are usually rodents, such as mice or rats. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.
Ancylostoma braziliense is a species of hookworm belonging to the genus Ancylostoma. It is an intestinal parasite of domestic cats and dogs. Severe infection is often fatal to these pets, especially in puppies and kittens. The infection is particularly endemic in the southern United States. It is most often confused with the zoonotic hookworm species Ancylostoma ceylanicum because of their uncanny resemblance.
Ancylostoma caninum is a species of nematode known as a hookworm, which principally infects the small intestine of dogs. The result of A. caninum infection ranges from asymptomatic cases to death of the dog; better nourishment, increasing age, prior A. caninum exposure, or vaccination are all linked to improved survival. Other hosts include carnivores such as wolves, foxes, and cats, with a small number of cases having been reported in humans.
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Parascaris is a genus of nematodes in the family Ascarididae. It contains two species, Parascaris equorum and Parascaris univalens, which are morphologically identical, but can be distinguished by chromosome number. Both species parasitize horses.
Strongyloides westeri, commonly referred to as intestinal threadworm, is a species of small nematode parasite in the family Strongylidae. Strongyloides are commonly found in the small intestine of mammals, that are characterized by an unusual lifecycle that involves one generations of free-living adult worms.
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