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Pinworms and bed bugs and lice, oh my! Parasites living in or on the body spell trouble for not only your patient, but also for those with whom your patient comes in contact. We give you information about controlling and preventing the spread of common parasitic infections.
Although the thought of another entity living in or on our bodies is repulsive, it has happened to all of us. If you've had an infection, you've had a parasite-all infectious agents are parasitic. By definition, a parasite is an organism that lives on or in a host and gets its food from that host. In this article, we'll guide you through the world of common parasites and educate you on how to keep you and your patients safe from transmission.
Endoparasites-those that live inside the host-are sometimes referred to as animal parasites to distinguish them from bacteria, fungi, and viruses. Common types of endoparasites include protozoa, pinworms, tapeworms, and roundworms.
Parasitic protozoa are one-celled organisms that can multiply from a single organism to a serious infection. There are two routes of transmission: the fecal-oral route and transference through a vector such as mosquitoes. Common protozoan infections are cryptosporidiosis, giardiasis, toxoplasmosis, and trichomoniasis (the most common infection in humans, with more than 7 million cases of vaginal infection per year).
Giardia and cryptosporidium cause gastrointestinal (GI) symptoms that can range from mild to life-threatening. Cryptosporidium are the leading cause of recreational water-related infection in the United States, with giardia a close second in certain locations. Cryptosporidiosis and giardiasis occur via feces from an infected animal released into a water source, generally a rural stream, lake, or pond.
Another protozoa, toxoplasma, is present in many animals; it's estimated that up to one-half of the world's population is infected. The most common cause of toxoplasmosis in the United States is contact with cat feces. Generally, infection causes mild flulike symptoms, but in immune deficient patients, this infection can be fatal. In pregnant women, the infection can be transferred to the fetus, causing a variety of birth abnormalities. Immunosuppressed patients and women who are pregnant or planning to become pregnant should avoid coming in contact with cat feces (gardening where cats have defecated or cleaning/changing litter boxes.)
Trichomoniasis is a common sexually transmitted disease caused by Trichomonas vaginalis. Most patients aren't aware they're infected, and of the estimated 3.7 million who are infected, only about one-third develop symptoms. Symptoms range from genital itching and pain with sexual activity to foul-smelling discharge. Without treatment, infection can last for years. Trichomoniasis can cause genital inflammation that may contribute to the transmission of HIV or induce low birth weight or preterm birth in pregnant women. To avoid reinfection, both partners must be treated simultaneously.
Medications to treat protozoan infection include metronidazole and tinidazole. Metronidazole can be taken by pregnant women.
The pinworm, or threadworm, is the most common parasitic worm infection in the United States and Western Europe, with an overall incidence of about 10% in all age groups. Children are most commonly affected because of habits such as thumb sucking, playing in soil, and poor hand washing. Persons living in close proximity to each other can spread the infection, and treatment should include all residents of a household.
The entire life cycle (from egg to adult) occurs within the GI tract of the host. Eggs are ingested and hatch in the small intestine, migrating to the colon. The worms mate during this migration and when they reach the colon, they attach to the intestinal mucosa and begin feeding on intestinal content. One pregnant female worm can contain 10,000 to 15,000 eggs. The female releases from the mucosa and migrates out of the anus to deposit the eggs on the skin. These eggs are sticky and can be transferred to other surfaces, such as bed linen, furniture, soil, toys, or pets.
The primary symptom of infection is anal itching, which is usually worse at night. These pesky pinworms may spread to the vagina in women and cause vaginal discharge. Pinworms are treated with medications such as mebendazole, which can also be used to treat other parasitic worm infections. Because some of these infections can cause anemia, iron may also be prescribed.
Tapeworms are parasitic, segmented flatworms. These species of worm live in the digestive tract of mammals, including humans. Transmission is from undercooked meat or exposure to feces from an infected host.
After a worm segment or eggs are ingested, the worm attaches to the wall of the intestine and feeds on the intestinal contents. Each flat segment of this worm is a self-contained digestive and reproductive system. New segments start at the head (attachment end) and the older segments are near the tail. The older segments are eventually shed and excreted, thus the eggs and segments are released and available to infect a new host. Some species of tape worms can reach 30 to 40 ft (9 to 12 m) in length.
Signs and symptoms can include visualization of the worm, eggs, or segments; nutritional deficits; failure to thrive; anal itching; and nausea and vomiting. Tapeworms are treated with medications that are toxic to the worms, such as praziquantel, albendazole, and nitazoxanide.
Some worms, such as trichinella spiralis (a type of round worm), don't remain confined within the digestive tract. Although the incidence of trichinosis, or trichinellosis, has declined in recent decades, infection still occurs in the United States, mostly as a result of eating raw or undercooked pork or wild game.
Infection occurs in the intestines, but these worms are also able to pierce through the intestine, allowing access to the rest of the body. The larvae can continue to migrate through muscle tissue and vessels until large areas of the body are involved. Damage done to these structures can cause inflammatory responses, avenues of infection, and vasculitis. Central nervous system damage can mimic stroke, and death can occur as lung or myocardial tissues are invaded and destroyed.
Patients with trichinosis may be asymptomatic, but common complaints in the first few days of infection, such as nausea, vomiting, diarrhea, or abdominal discomfort, can easily be mistaken for other illnesses. At about 2 to 8 weeks following infection, patients may experience muscle pain, fever, swelling of the face, headache, chills, itching, cough, diarrhea, and constipation.
It's important to begin treatment as soon as possible with albendazole or mebendazole because after the larvae have invaded the striated muscle, medications may not be completely effective. To prevent trichinosis, all wild game and pork should be cooked to an internal temperature of 165[degrees] F (73.8[degrees] C).
Care for patients with endoparasitic infections includes:
* teaching the patient about the parasite and how it's transmitted to prevent reinfection and spread to new hosts
* ensuring that the patient understands the medication regimen and potential adverse reactions
* monitoring the patient's nutritional status, along with results from treatment.
Ectoparasites-those that live on the surface of the host-have been a pest to mankind for centuries. Common types of ectoparasites include bed bugs and lice.
Bed bugs are broad, oval-shaped, flat, wingless insects. Adult bed bugs are 4 to 7 mm long (about the size of an apple seed), have six legs, and are reddish brown in color. Their eggs hatch into white nymphs that darken with each molt. The length of time for maturity from egg to adult depends on ambient temperature and available food, making these insects viable for weeks or months.
Although bed bugs have been eradicated in most developed countries with the use of pesticides, they've made a comeback. The reason for their resurgence may be linked to increased international travel, changes in pest control practices, and insecticide resistance. Bed bugs aren't picky about their environment and can be found in five-star hotels or the most pristine homes. High turnover areas, such as hotels, dormitories, or homeless shelters, are ideal targets for infestation.
Bed bugs are rarely seen during the day, taking refuge in cracks and crevices in bedding, headboards, or box springs. You can usually see their excrement along mattress seams; appearing as dark specks. Over time, bed bugs can spread to other areas, such as carpeting, along baseboards, behind pictures, or any crevice or protected location. Bed bugs can crawl about as fast as a lady bug and, because of their size, can easily spread from room to room or floor to floor of a hotel. They can also migrate on clothing or belongings.
Bed bugs feed solely on blood and normally do their feeding at night while you're sleeping. They feed by piercing the skin and withdrawing blood through an elongated beak. A bed bug will feed on its host for about 10 to 15 minutes and swell from the blood; appearing dark brown and dropping off the host. However, bed bugs can survive for up to 1 year without taking one drop of blood.
Patients generally present with bed bug bites as the first indication of infection; the most common signs are small clusters of extremely pruritic, erythematous papules or wheals that represent repeated feedings by a single bed bug. The most common bite areas are the arms, legs, ankles, back, neck, and face, but bed bugs will bite in any area of skin to which they're exposed. They don't like to remain or crawl on the skin, preferring to move and hide following a blood meal. Bites are usually a red oval to oblong wheal, but may be as large as 3 cm (1.18 in) or may present as a bulla (blister). You may even see blood on the sheets from where a blood engorged bedbug has been crushed.
Patients are treated symptomatically with topical steroids and, possibly, oral antihistamines. When there's secondary bacterial infection, a topical antimicrobial may be indicated. The eradication of bed bugs from a building must include a thorough vacuuming of cracks and crevices; washing clothing and other items in hot water at least 120[degrees] F (48.8[degrees] C); and placing items, wet or dry, in a dryer on medium to high heat for at least 20 minutes. Mattresses and pillows should be sealed in plastic to prevent bed bugs from feeding, killing them over time. Pesticides shouldn't be used on bedding unless specified for such use, but a combination of pesticides and environmental treatment is necessary to rid the area of insects.
Lice are tiny, wingless ectoparasites that live on the body. They can be found on the head, body, or pubic area.
In general, the life cycle of lice has three stages: egg, nymph, and adult. A mature female louse lays 3 to 6 eggs per day, called nits. With head lice, the eggs are usually laid at the base of the hair shaft and take about a week to hatch, releasing a nymph. The nymph will molt, shedding its exoskeleton three times before reaching maturity in 12 to 15 days. Adult lice live for approximately 10 days and will die within 24 to 48 hours off of the host.
Head lice are the most common of the three species and can be seen with the naked eye. An adult louse is approximately 2 to 3 mm in length, tan to grayish-white, and is commonly mistaken for dandruff. Head lice affect all socioeconomic groups, but are most common in young school-age children, especially ages 3 to 12 and girls more often than boys. Infestations occur at the head, nape of the neck, and behind the ears. Lice don't hop or fly, but rather move by crawling. Although contagious, they aren't dangerous and don't spread disease.
Body lice are larger than head lice; approximately 2 to 4 mm long. They live in clothing and bedding, moving onto the skin to feed (mostly at night). Body lice are more often found on homeless or transient individuals.
Pubic lice get their nickname, "crabs," from their crablike appearance: broad bodies and large front claws, which allow them to grasp coarse pubic hair. They're hard to see and often confused with dandruff. Rarely are these lice found on other hairy areas of the body, such as the chest in men or eyebrows. Pubic lice are transmitted from person to person, most commonly via sexual contact (considered a sexually transmitted disease).
Lice can be spread through head-to-head contact; body-to-body contact; storing belongings in close proximity to infected items; and shared items, such as clothing, combs, brushed, towels, blankets, and pillows. Risk factors include poor hygiene, overcrowding, sexual promiscuity, and malnutrition. However, any population is vulnerable and occurrences are rarely isolated.
Signs and symptoms usually include, but aren't limited to, itching; tickling; feeling hair movement; and small, red bumps or sores from scratching.
Currently, pediculicides are the cornerstone of treatment for head, body, and pubic lice. Over-the-counter (OTC) shampoos, such as pyrethrin or permethrin, are usually first-line treatments. These products come with a special comb, which should be used to comb the nits out of the hair. If OTC medications don't work, prescription medications, such as malathion, are available. In January 2011, the FDA approved spinosad topical suspension 0.9% for the treatment of head lice infestation in people age 4 and older with just one treatment.
Eradication of lice requires all members of the family to be treated at the same time. Clothing, bedding, and combs/brushes should be washed in hot, soapy water of at least 130[degrees] F (54.4[degrees] C) and dried at high heat for at least 20 minutes. Unwashable items need to be sealed in airtight containers for at least 2 weeks. Furniture and flooring should be vacuumed thoroughly. If a child has head lice, the school should be notified so that other children can be checked. Children should be kept home from school until the morning after treatment is given.
When bedbugs or lice are suspected on a patient, immediate action must be taken to prevent spread. The patient should be placed in isolation, the patient's clothes and belongings must be sealed in an airtight container, and the patient should be bathed (and treated, if ordered). When admitted to the hospital, the patient's family and visitors must be instructed not to bring any personal belongings from the patient's home to the hospital.
Testing and other treatments are postponed until after the patient is bathed and treated. Patients with lice are maintained in isolation until medically cleared. For diagnostic studies or procedures, notify pertinent departments of the patient's status so that proper precautions can be observed.
Humans have always been plagued by parasites. The resurgence of bed bugs is a perfect example of a parasitic threat that was reasonably well controlled in the United States in the past, but has recently spread like wildfire. These pests are just waiting for an opportunity to infect you or your patient.
Remember, the keys to controlling parasites are prevention by understanding how and when they attack, containment by preventing their spread to other hosts, and treatment by eradicating the parasite from the host. Armed with information about a variety of parasites, you can help your patients avoid infection and understand control and treatment for those parasites that they can't avoid.
* Roundworms (trichinosis)
* Bed bugs
* Teach the patient about the parasite and how it's transmitted to prevent reinfection and spread to new hosts.
* Ensure that the patient understands the medication regimen and potential adverse reactions.
* Monitor the patient's nutritional status, along with results from treatment.
* Place the patient in isolation. (Patients with lice are maintained in isolation until they're medically cleared.)
* Seal the patient's clothes and belongings in an airtight container.
* Bathe the patient and treat as prescribed. (Postpone testing until after the patient is bathed and treated.)
* Instruct the patient's family and visitors not to bring any personal belongings from the patient's home to the hospital.
* Notify pertinent departments of the patient's status so that proper precautions can be observed.
CDC. Parasites. http://www.cdc.gov/parasites/.
Fallen RS, Gooderham M. Bedbugs: an update on recognition and management. Skin Therapy Lett. 2011;16(6):5-7.
Goddard J, deShazo R. Bed bugs (Cimex lectularius) and clinical consequences of their bites. JAMA. 2009;301(13):1358-1366.
Gottstein B, Pozio E, Nockler K. Epidemiology, diagnosis, treatment, and control of trichinellosis. Clin Microbiol Rev. 2009;22(1):127-145.
Guenther L. Pediculosis (lice). http://emedicine.medscape.com/article/225013-overview.
Heymann WR. Head lice treatments: searching for the path of least resistance. J Am Acad Dermatol. 2009;61(2):323-324.
United States Department of Agriculture. Foodborne illness and disease. http://www.fsis.usda.gov/factsheets/Parasites_and_Foodborne_Illness/index.asp.
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