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Helminthiasis • Helminthiasis is a macroparasiticdisease of humans and animals in which a part of the body is infested with parasitic worms such as pinworm, roundworm, or tapeworm. Typically, the worms reside in the gastrointestinal tract but may also burrow into the liver or other organs. • Helminthiasiscan have immunomodulatory effects on the host,[1] with implications for any coinfectingpathogens.
Hymenolepiasis. Hymenolepiasisis caused by two cestodes (tapeworm) species, Hymenolepisnana (the dwarf tapeworm, adults measuring 15 to 40 mm in length) and Hymenolepisdimnuta (rat tapeworm, adults measuring 20 to 60 cm in length). Hymenolepisdiminuta is a cestode of rodents infrequently seen in humans and frequently found in rodents.
Hymenolepis Nana - Dwarf Tapeworm • Hymenolepis nana is the most common tapeworm in humans. It is also known as the dwarf tapeworm due to its particularly small size (adults are only 15–40 mm long). The disease, hymenolepiasis is found worldwide. In temperate zones children and institutionalized people are infected more often. The disease is somewhat common in the eastern Europe.
Geographic Distribution: Hymenolepis nana is the most common cause of all cestode infections, and is encountered worldwide. In temperate areas its incidence is higher in children and institutionalized groups. Hymenolepisdiminuta, while less frequent, has been reported from various areas of the world.
Egg • H. nanaegg is colourless, almost transparent, oval, 30–50 µm (micrometers) in diameter, has polar filaments. When shed in stool they are immediately infective and survive up to 10 days in the external environment, they are embryonated and have a 6-hooked oncospheres inside the shells. Shell consists of two distinct membranes. On inner membrane there are two small "knobs" or poles from which 4–8 filaments arise and spread out between the two membranes.
Scolex • Scolex is small, 0.3 mm in diameter, globular (rounded), cup-like, situated at the anterior end, has four suckers and retractile rostellum with a single row of 20–30 hooks.
Proglottids. • Gravid (mature, full of eggs) proglottids are 0.2–0.3 mm long and 0.8–0.9 mm wide. Proglottid is filled with eggs, uterus is not visible. Each proglottid has both male and female reproductive organs making Hymenolepisnanahermaphroditic. A proglottid copulates with itself or with other segments of the same individual or nearbyHymenolepis nana tapeworms. Proglottids usually disintegrate in the gastrointestinal tract and are rarely present in the feces.
. • 1.Eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment . • 2.When eggs are ingested by an arthropod intermediate host • 3.(various species of beetles and fleas may serve as intermediate hosts), they develop into cysticercoids, which can infect humans or rodents upon ingestion • 4. and develop into adults in the small intestine. A morphologically identical variant, H. nana var. fraterna, infects rodents and uses arthropods as intermediate hosts. When eggs are ingested • 5.(in contaminated food or water or from hands contaminated with feces), the oncospheres contained in the eggs are released. The oncospheres (hexacanth larvae) penetrate the intestinal villus and develop into cysticercoid larvae . • 6.Upon rupture of the villus, the cysticercoids return to the intestinal lumen, evaginate their scoleces , • 7.attach to the intestinal mucosa and develop into adults that reside in the ileal portion of the small intestine producing gravid proglottids . • 8.Eggs are passed in the stool when released from proglottids through its genital atrium or when proglottids disintegrate in the small intestine . • 9.An alternate mode of infection consists of internal autoinfection, where the eggs release their hexacanth embryo, which penetrates the villus continuing the infective cycle without passage through the external environment . The life span of adult worms is 4 to 6 weeks, but internal autoinfection allows the infection to persist for years.
. Eggs of Hymenolepisdiminuta are passed out in the feces of the infected definitive host (rodents, man) . 2. The mature eggs are ingested by an intermediate host (various arthropod adults or larvae) , 3. and oncospheres are released from the eggs and penetrate the intestinal wall of the host , 4. which develop into cysticercoid larvae. Species from the genus Triboliumare common intermediate hosts for H. diminuta. The cysticercoid larvae persist through the arthropod's morphogenesis to adulthood. H. diminuta infection is acquired by the mammalian host after ingestion of an intermediate host carrying the cysticercoid larvae . 5. Humans can be accidentally infected through the ingestion of insects in precooked cereals, or other food items, and directly from the environment (e.g., oral exploration of the environment by children). After ingestion, the tissue of the infected arthropod is digested releasing the cysticercoid larvae in the stomach and small intestine. Eversion of the scoleces 6. occurs shortly after the cysticercoid larvae are released. Using the four suckers on the scolex, the parasite attaches to the small intestine wall. Maturation of the parasites occurs within 20 days and the adult worms can reach an average of 30 cm in length . 7. Eggs are released in the small intestine from gravid proglottids 8. that disintegrate after breaking off from the adult worms. The eggs are expelled to the environment in the mammalian host's feces .
Symptoms: Hymenolepiasis is usually asymptomatic in adults. But prolonged infection or multiple tapeworms especially in children can cause more severe symptoms. The worms eat your food and cause inflammation of the intestinal mucosa. The inflamed tissue will have a reduced ability to absorb nutrients. People with little food to begin with and those who are weakened by other diseases suffer the most. Hymenolepiasissymptomssometimes include: anal itching diarrhea (can be bloody) headache increased appetite or loss of appetite insomnia muscle spasms nausea nervousness seizures stomach ache vomiting weakness weight loss.
Diagnosis: • Your health care provider makes the diagnosis by identifying tapeworm eggs in stool. Sometimes many stool specimens are needed to make the diagnosis. Hymenolepis nana starts laying eggs within a few weeks of the start of the infection and only after that it is possible to find eggs. Alternatively adult worm can be identified during endoscopic examination. Hymenolepis Nana, adult, stained mount.
Treatment: • Hymenolepiasisis usually treated with a prescription drug called praziquantel which causes the tapeworm (both adults and larvae) to dissolve. A single dose of praziquantel has an efficacy of 96 %. If praziquantel is not available, niclosamideor albendazole can be used instead.
To prevent getting infected: Wash, peel or cook all fruits and vegetables. Wash hands with water and soap after using the toilet and before preparing food or eating. Quit the habit of putting fingers in your nose and mouth. The microscopic parasite eggs are sometimes found under fingernails and can easily be ingested.
Enterobiosis. • Enterobiusvermicularis, a small nematode, is a common cause of helminthic infestation in the United States. The female nematode averages 10 mm X 0.7 mm, whereas males are smaller. All socioeconomic levels are affected. Infestation often occurs in family clusters. Infestation does not equate with poor home sanitary measures (an important point when discussing therapy).
Pathophysiology • E vermicularis is an obligate parasite; humans are the only natural host. Fecal-oral contamination via hand-mouth contact or via fomites (toys, clothes) are common methods of infestation. After ingestion, eggs usually hatch in the duodenum within 6 hours. Worms mature in as little as 2 weeks and have a life span of approximately 2 months. • Adult worms normally inhabit the terminal ileum, cecum, vermiform appendix, and proximal ascending colon. The worms live free in the intestinal lumen. Little evidence supports invasion of healthy tissue under normal conditions. The female worm migrates to the rectum after copulation and, if not expelled during defecation, migrates to the perineum (often at night) where an average of 11,000 eggs are released. Eggs become infectious within 6-8 hours and, under optimum conditions, remain infectious in the environment for as long as 3 weeks. • See the image below.
Epidemiology • Frequency • United States • Prevalence is approximately 5-15% in the general population; however, this rate has declined in recent years. Prevalence rates are probably higher in institutionalized individuals. Humans are the only known host. • International • E vermicularis infestation occurs worldwide. Prevalence data vary by country. • Mortality/Morbidity • Secondary bacterial skin infection may develop from vigorous scratching to relieve pruritus. Reinfestation is common. Infection can develop as long as female pinworms continue to lay eggs on the skin. Restless sleeping may be due to pruritus ani. Infestation has been reported to cause enuresis. • Immunocompromised • Although other helminthic infection rates are shown to be higher in patients with HIV, studies to date have not shown a statistically significant difference forEvermicularis.[1] • Race • All races are subject to infestation. • Sex • Infestation can occur in males and females. • Age • The prevalence is greatest in children aged 5-9 years, but all ages can be affected
Symptoms • Patients with enterobiasis are often asymptomatic. Worms may be incidentally discovered when they are seen in the perineal region. • If patients are symptomatic, pruritus ani and pruritus vulvae are common presenting symptoms. However, one study failed to find an increase of these symptoms in infested children compared with matched control subjects. • Restlessness during sleep is noted by the parents of many patients. • Enuresis may be a symptom in children with pinworms. • Patients often have excoriation or erythema of the perineum, vulvae, or both, but infestation can occur without these signs. • Visual sighting of a worm by a reliable source (eg, a parent) is usually accepted as evidence of infestation and grounds for treatment. • Worms can be found in stools or on the patient's perineum before bathing in the morning. • Occasionally, the gravid female worm may aberrantly migrate into the female genitalia and produce vaginitis.[2] Incidental recovery at necropsy or surgery of small granulomatous lesions surrounding the worm, larvae, or eggs in the salpinx and peritoneum demonstrates the worm's ability to ascend the female genital tract. • Abdominal pain may sometimes be severe and can mimic acute appendicitis.
Differentials • Appendicitis • Ascariasis • Cervicitis • Contact Dermatitis • Giardiasis
Laboratory Studies • Without a visual report, diagnosis of enterobiasis can be confirmed using the knowledge that eggs are normally deposited in great quantities on the perineum at night. • Wide (2 inch) transparent tape is pressed against the perineum at night or in the morning before the patient bathes to capture eggs.[4] Three such specimens are usually consecutively collected. • Diagnosis is made by identifying eggs under the low-power lens of microscope. Dilute sodium hydroxide or toluene should be added to the slide.
Medical Care • Fear, disgust, and guilt are common parental reactions to a parasitic worm infestation, such as enterobiasis. Many families present to the emergency department or their pediatrician with misconceptions about pinworms. In addition to prescribing medications, educating families about pinworms (see Patient Education) is helpful. • Thorough and regular handwashing is effective in preventing disease transmission.
Medication Summary • Mebendazole or albendazole are recommended as first-line treatment of pinworms. A second dose given 2 weeks after the initial dose helps prevent reoccurrences from reinfection. • Because asymptomatic infestation of other members in a household is frequent, simultaneously treating all household members may be reasonable. Families should be informed that repeat infestations are common. Reinfestation is treated with the same medications as the initial infestation. • Symptomatic relief of pruritus can be obtained by applying an antipruritic ointment or cream topically to the affected (usually perianal) region. • Anal albendazole may help with symptoms of pruritus ani. A recent letter to the editor stated a “local application of albendazole using an ear bud soaked with the residual albendazole suspension in the vial” in addition to the recommended oral dose of albendazole provided dramatic relief of pruritus ani.[5] • Ivermectin has been shown to have decreased efficacy as a single agent, compared with albendazole.[6] However, it may possess efficacy when given as an adjunct.
Anthelmintics • Class Summary • Parasite biochemical pathways are different from the human host, thus toxicity is directed to the parasite, egg, or larvae. Mechanism of action varies within the drug class. • Pyrantelpamoate (Antiminth, Pin-Rid, Pin-X) • Depolarizing neuromuscular blocking agent and inhibits cholinesterases, resulting in spastic paralysis of the worm. Purging not necessary. May be taken with milk or fruit juices. • Mebendazole(Vermox) • Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell. • Albendazole(Albenza) • A benzimidazolecarbamate drug that inhibits tubulin polymerization, resulting in degeneration of cytoplasmic microtubules. Decreases ATP production in worm, causing energy depletion, immobilization, and finally death. Converted in the liver to its primary metabolite, albendazolesulfoxide. Less than 1% of the primary metabolite is excreted in the urine. Plasma level is noted to rise significantly (as much as 5-fold) when ingested after high-fat meal. Experience with patients < 6 y is limited. • To avoid inflammatory response in CNS, patient must also be started on anticonvulsants and high-dose glucocorticoids.
Inpatient & Outpatient Medications • An antihelminthic medication should be prescribed to patients with enterobiasis . • Application of an antipruritic ointment or albendazole may help control scratching.[5]
Complications • Beware of skin infection from vigorous scratching to relieve pruritus. • Pinworms have been associated with appendicitis.[7, 8] However, small and large intestine ulcerations, perianal abscesses, intestinal pain, transient synovitis, or enuresis is believed to be coincidental and not causal.[9] • If a patient with enterobiasis is refractory to treatment, consider the possibility of an infestation with Dipylidiumcaninum, which is a common tapeworm that infects domestic cats and dogs.[10]
Patient Education • Inform families that dogs and cats do not harbor E vermicularis. • Inform families that infestation may occur in spite of proper child and household hygiene. • Counsel families to avoid overreaction through aggressive sanitary measures. Because infectious eggs may be in bedclothes and dust and remain infectious for 20 days, wet-mopping floors or vacuuming carpets and washing bedclothes are prudent precautions. • Reassuring families that pinworms are not a sexually transmitted disease and are not evidence of child abuse may be helpful. • Keeping the patient's fingernails trimmed to prevent excoriations is helpful. • Avoid scratching the area and nail biting because this is a cause of autoinfection. • Encourage the patient to bathe in the morning, this significantly reduces the number of eggs. • Children may return to school once they have received a dose of medication, bathed, and have nails trimmed. • Bed linens should be washed in hot, soapy water.
Enterobiasis and child • Enterobiasis is a disease caused by tiny parasitic worms - pinworms or Enterobiusvermicularis. Pinworms do not exceed 1 cm at length. Usually one end of this worm is pointed (hence comes the name) and the other rounded. Parasites may have different color: from thewhitish or yellow to dark or even black. Living pinworms may crawl or squirm. Pinworms are nocturnal animals: it is at night when the females of pinworms go into the rectum and skin around the anus, causing discomfort and itching. They lay eggs in the folds of the skin and die. • Infection is transmitted through dirty hands or contaminated objects. Child, combing or touching the skin of the perineum, contaminate hands with the worm eggs. After contaminated hands contact the bed or underwear eggs come from the body of a patient. The role of fliesandcockroaches in the transference of pinworm eggs is proven. A re-infection when mature pinworm moves from the skin into the anus is not very rare. Enterobiasis is very common human parasitic disease and it is considered to be the most common infections worldwide. In some baby groups up to 100% of children are infected with pinworms.
Syptoms • The period from contamination to onset of symptoms at enterobiasis is 12 - 14 days. This is the time when pinworms reach maturity age. The main symptoms of the disease is itchingordiscomfort in the anus, redness around the anus or perineum especially after defecation, the increased interest of the child to his genitals, masturbation. In girls, in addition, pinworms can creep in genital tract, causing inflammation and infections (vulvovaginitis, urethritis, thrush). Also the child becomes an excitable in the evening and very moody. For a long time a child can not fall asleep, sleeping restlessly - often wakes up and screams during sleep, crying, tossing on the bed. Simultaneously a daytime sleep may be normal. These symptoms may occur not every day, if there's a bit worms in the gut. But when the number of parasites increases - the described discomfort may become permanent. In addition, pinworms, like any other focus of chronic infection can cause a malfunction in the bowel (abdominal pain, excessive flatulence, constipationordiarrhea, food maldigestion, etc.), allergic reactions, intoxication (lethargy, fatigue, irritability, teeth grinding or bruxism), lead to intestinal dysbacteriosis.
Diagnosis • The diagnosis of enterobiasis isn't very difficult, especially if pinworms are found. They can be seen in the evening or at night near the anus or on the skin folds or on the bedclothes. Sometimes you can see the worms in the excrements. A special study for the detection of pinworm eggs - scraping on enterobiasis - (smearing of skin folds around the anus, or sticking this area with adhesive tape) sometimes can not reveal the disease if a pinworm had not laid eggs before. Hence, scraping on enterobiasis should be conducted in the morning after a night when a child could not sleep or slept restless. An important moment - you shouldn't wash a child before scraping. If you receive a negative result, repeat the scraping for several times during 1 - 2 weeks.With a strong suspicion about enterobiasis a treating should be started even if pinworms or their eggs are not found!
