''Trichuris suis'' is a whipworm; the variations in thickness of the anterior and posterior segments give the parasite the characteristic "whip-like" appearance. Adult females measure 6 to 8 cm and adult males 3 to 4 cm. ''T. suis'' eggs are oval (60 × 25 μm) and yellow-brown with bipolar plugs.Trichuris suis in finishing pigs: Case report and review
Journal of Swine Health and Production — November and December 2010 ''T. suis'' is also used in helminthic therapy studies.

Lifecycle

The lifecycle of ''T. suis'' is direct and does not require any

intermediate host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include ...

. Eggs are passed in feces from infected animals, but are single-celled and are not initially infectious. Infective J1 stage larvae develop within the shell in 3 weeks to 2 months, depending on environmental temperature. The infective J1 stage within the egg is highly resistant and can remain in this form for several years in favorable conditions. Once the infective J1 egg is ingested, the bipolar plugs are digested and the J1 larvae hatch in the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

and

cecum The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (a ...

. The J1 larvae penetrate the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

via the

crypts of Lieberkühn In histology, an intestinal gland (also crypt of Lieberkühn and intestinal crypt) is a gland found in between villi in the intestinal epithelial lining of the small intestine and large intestine (or colon). The glands and intestinal villi are ...

in the distal ileum,

, and colon. During the next 5 weeks, the larvae undergo four molts (J2, J3, J4, J5) to the adult stage within the mucosal layers. The adult's thicker posterior third then emerges through the mucosal surface into the lumen, while the thin anterior two-thirds remains embedded in the mucosal layers. Adults can be recovered from the distal ileum to the rectum, but most are located in the

and proximal colon. The prepatent period is 6 to 8 weeks and lifespan is 4 to 5 months.

Epidemiology

Pigs are the natural host for ''T. suis'', but it can also affect other species - including people. Humans probably become infected with ''T. suis'' by ingesting contaminated soil or water. ''T. suis'' is found worldwide, but is most prevalent in warm, humid climates. It is rare or nonexistent in arid, very hot, or very cold regions.

Pathology and symptoms

In adult pigs, infections with ''T. suis'' can cause

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

anorexia Anorexia nervosa (AN), often referred to simply as anorexia, is an eating disorder characterized by Calorie restriction, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. Individuals wit ...

anemia Anemia (also spelt anaemia in British English) is a blood disorder in which the blood has a reduced ability to carry oxygen. This can be due to a lower than normal number of red blood cells, a reduction in the amount of hemoglobin availabl ...

, poor growth,

dehydration In physiology, dehydration is a lack of total body water that disrupts metabolic processes. It occurs when free water loss exceeds intake, often resulting from excessive sweating, health conditions, or inadequate consumption of water. Mild deh ...

, and

emaciation Emaciation is defined as the state of extreme thinness from absence of body fat and muscle wasting usually resulting from malnutrition. It is often seen as the opposite of obesity. Characteristics Emaciation manifests physically as thin limbs, pr ...

, but acuteness is usually connected to the infective dose or concurrent bacterial enteritis.

Dysentery Dysentery ( , ), historically known as the bloody flux, is a type of gastroenteritis that results in bloody diarrhea. Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation. Complications may include dehyd ...

, anemia, and death have also been described in infections in younger pigs. Critical infestations of ''T. suis'' may cause acute morbidity and mortality in young female pigs. ''T. suis'' has been shown in trials to colonize humans briefly without triggering infections.

Diagnosis

In pigs ''T. suis'' egg production is sporadic, complicating diagnosis by

fecal flotation Feces (also known as faeces or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relatively small amount of ...

. Necropsy of clinical cases of trichuriasis may be necessary to validate a diagnosis, since clinical signs may develop prior to patency, thus inhibiting diagnosis by fecal examination alone. On gross necropsy, the intestine may be filled with semisolid to watery to bloody mucoid feces, depending on acuteness of the infection and simultaneous bacterial infections. The anterior portion of adult worms may be observable breaching the cecal and colonic mucosa. Inflammatory nodules may be seen adjacent to the adults where they penetrate the mucosa. In earlier infections, the nodules may suggest pre-erupted larvae beneath the mucosa. Depending on the acuteness of infection, there is generalized moderate to severe typhlitis and

colitis Colitis is swelling or inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and ...

. In severe infections, the walls of the intestine may be thickened and a necrotic membrane may be located on the surface of the mucosa.

Treatment

The pathogenicity and symptoms are generally mild in human and it can be treated with medicines such as

doramectin Doramectin, sold under the brand name Dectomax among others, is a veterinary medication approved by the US Food and Drug Administration (FDA) for the treatment of parasites such as gastrointestinal roundworms, lungworms, eyeworms, Larva, grubs, s ...

ivermectin Ivermectin is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, it is used to treat infestations including head lice ...

, and febantel. Although no treatment is initiated for pigs that are infected with ''T. suis'' due to the lack of clinical impact,

piperazine Piperazine () is an organic compound with the formula . In term of its structure, it can be described as cyclohexane with the 1- and 4-CH2 groups replaced by NH. Piperazine exists as deliquescent solid with a saline taste. Piperazine is freely sol ...

can be applied to minimize the negative impact that the parasite reflects on the host.

Helminthic therapy

''T. suis'' ova therapy may produce significant and long-lasting improvements in active

Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea, fever, abdominal distension, and weight loss. Complications outside of the ...

. In a study conducted at the

University of Iowa The University of Iowa (U of I, UIowa, or Iowa) is a public university, public research university in Iowa City, Iowa, United States. Founded in 1847, it is the oldest and largest university in the state. The University of Iowa is organized int ...

, patients who had been administered with ''T. suis'' ova for 24 weeks had a response rate of nearly 80% and a remission rate of nearly 73%.

involves over reactive Th1 pathways and colonization with parasitic worms expands several immunoregulatory pathways that limit Th1-type inflammation. Parasitic worms generate production of

interleukin 4 The interleukin 4 (IL4, IL-4) is a cytokine that induces differentiation of naive helper T cells ( Th0 cells) to Th2 cells. Upon activation by IL-4, Th2 cells subsequently produce additional IL-4 in a positive feedback loop. IL-4 ...

and interleukin 13, which are Th2

cytokine Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

s. This Th2 response restrains production of Th1 cytokines, thereby reducing colitis severity. Parasitic worms also generate regulatory T cells and immune regulatory substances such as transforming growth factor β,

interleukin 10 Interleukin 10 (IL-10), also known as human cytokine synthesis inhibitory factor (CSIF), is an anti- inflammatory cytokine. In humans, interleukin 10 is encoded by the ''IL10'' gene. IL-10 signals through a receptor complex consisting of two IL- ...

, and

prostaglandin E2 Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnanc ...

that assist in sustaining host mucosal

homeostasis In biology, homeostasis (British English, British also homoeostasis; ) is the state of steady internal physics, physical and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning fo ...

. However, a recent larger RCT has shown no effect on Crohn's disease in comparison to

placebo A placebo ( ) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures. Placebos are used in randomized clinical trials ...

. The U.S. Food and Drug Administration has granted pig whipworm (''Trichuris suis'') the status of

Investigational New Drug The United States Food and Drug Administration's Investigational New Drug (IND) program is the means by which a pharmaceutical industry, pharmaceutical company obtains permission to start human clinical trials and to ship an experimental drug inte ...

, allowing clinical trials in humans.

Allergic rhinitis

In a 2010 randomized double-blind placebo clinical trial, ''T. suis'' induced immune response, but did nothing for the allergic symptoms.

Prevention and control

Prevention of ''T. suis'' depends on the treatment and prevention of infections in animals, the removal of feces before the eggs can become embryonated, good hygiene, and public education.

References

*The Scientist, Feb. 2011, pp. 42–47. {{Taxonbar, from=Q150987 Trichocephalida Nematodes described in 1789