Objectives AFTER STUDYING THIS CHAPTER, THE STUDENT WILL BE ABLE TO:
1. Describe environmental and other major factors
3. Discuss the drugs used to treat Pneumocystis
in prevention and recognition of selected para-
carinii pneumonia in clients with acquired
2. Discuss assessment and treatment of pinworm
4. Teach preventive interventions to clients
infestations and pediculosis in school-age
planning travel to a malarious area.
You are the school nurse in an elementary school. There is an outbreak of head lice in one of the fourth gradeclassrooms. Four girls are affected. You are responsible for identifying infested students and developingprevention programs.
Reflect on:ᮣ How infested children feel. ᮣ How the parents feel when they find out their child has head lice. ᮣ Appropriate infection control measures to prevent the spread of head lice to other children in the
ᮣ Teaching about the safe use of topical agents such as Nix.
tions for the mentally retarded, homosexual and bisexual men,and residents or travelers in countries with poor sanitation.
A parasite is a living organism that survives at the expense
Amebiasis is caused by the pathogenic protozoan Enta-
of another organism, called the host. Parasitic infestations
moeba histolytica, which exists in two forms. The cystic form
are common human ailments worldwide. The effects of par-
is inactive and resistant to a number of factors, including
asitic diseases on human hosts vary from minor to major
drugs, heat, cold, and drying. The cystic form can survive
and life threatening. Parasitic diseases in this chapter are
outside the body for long periods. Amebiasis is transmitted
those caused by protozoa, helminths (worms), scabies, and
by the fecal–oral route, such as ingesting food or water con-
pediculi (lice). Protozoa and helminths can infect the di-
taminated with human feces containing amebic cysts. Once
gestive tract and other body tissues; scabies and pediculi
ingested, some cysts open in the ileum to release amebae,
which produce trophozoites. Other cysts remain intact to beexpelled in feces and continue the chain of infection. Tropho-zoites are active amebae that feed, multiply, move about, and
produce clinical manifestations of amebiasis. Trophozoitesproduce an enzyme that allows them to invade body tissues.
They may form erosions and ulcerations in the intestinalwall with resultant diarrhea (this form of the disease is
Amebiasis is a common disease in Africa, Asia, and Latin
called intestinal amebiasis or amebic dysentery), or they
America, but it can occur in any geographic region. In the
may penetrate blood vessels and be carried to other organs,
United States it is most likely to occur in residents of institu-
where they form abscesses. These abscesses are usually
found in the liver (hepatic amebiasis), but also may occur in
the next person, the sporozoites are injected into that person’s
bloodstream. From the bloodstream, the organisms lodge in
Drugs used to treat amebiasis (amebicides) are classified
the liver and other tissues, where they reproduce and form
according to their site of action. For example, iodoquinol is
merozoites. The liver cells containing the parasite eventually
an intestinal amebicide because it acts within the lumen of the
rupture and release the merozoites into the bloodstream,
bowel; chloroquine is a tissue or extraintestinal amebicide
where they invade red blood cells. After a period of growth
because it acts in the bowel wall, liver, and other tissues.
and reproduction, merozoites rupture red blood cells, invade
Metronidazole (Flagyl) is effective in both intestinal and ex-
other erythrocytes, form gametocytes, and continue the cycle.
traintestinal amebiasis. No amebicides are currently recom-
After several cycles, clinical symptoms of malaria manifest
mended for prophylaxis of amebiasis.
secondary to the large parasite burden. The characteristic cy-cles of chills and fever correspond to the release of mero-zoites from erythrocytes.
Antimalarial drugs act at different stages in the life cycle of
plasmodial parasites. Some drugs (eg, chloroquine) are effec-
Giardiasis is caused by Giardia lamblia, a common intestinal
tive against erythrocytic forms and are therefore useful in pre-
parasite. It is spread by food or water contaminated with
venting or treating acute attacks of malaria. These drugs do not
human feces containing encysted forms of the organism or by
prevent infection with the parasite, but they do prevent clinical
contact with infected people or animals. Person-to-person
manifestations. Other drugs (eg, primaquine) act against exo-
spread often occurs among children in day care centers, in-
erythrocytic or tissue forms of the parasite to prevent initial in-
stitutionalized people, and homosexual or bisexual men. The
fection and recurrent attacks or to cure some types of malaria.
organism is also found in people who camp or hike in wilder-
Combination drug therapy, administered concomitantly or
ness areas or who drink untreated well water in areas where
consecutively, is common with antimalarial drugs.
sanitation is poor. Giardiasis may affect children more thanadults and may cause community outbreaks of diarrhea.
Giardial infections occur 1 to 2 weeks after ingestion of the
cysts and may be asymptomatic or produce diarrhea and ab-dominal cramping and distention. If untreated, giardiasis may
Pneumocystosis is caused by Pneumocystis carinii, a para-
resolve spontaneously or progress to a chronic disease with
sitic organism once considered a protozoan but now con-
anorexia, nausea, malaise, weight loss, and continued diarrhea
sidered a fungus. Sources and routes of spread have not
with large, foul-smelling, light-colored, fatty stools. Deficien-
been clearly delineated. It is apparently widespread in
cies of vitamin B12 and fat-soluble vitamins may occur. Adults
the environment, and most people are exposed at an early
and children older than 8 years with symptomatic giardiasis
age. Infections are mild or asymptomatic in immunocom-
should be treated with oral metronidazole.
petent people. However, the organism can form cysts in thelungs, persist for long periods, and become activated in im-munocompromised hosts. Activation produces P. carinii
pneumonia (PCP), an acute, life-threatening respiratory in-fection characterized by cough, fever, dyspnea, and pres-
Malaria is a common cause of morbidity and mortality in many
ence of the organism in sputum. Groups at risk include
parts of the world, especially in tropical regions. In the United
human immunodeficiency syndrome (HIV) seropositive
States, malaria is rare and affects travelers or immigrants from
persons; those receiving corticosteroids or antineoplastics
and other immunosuppressive drugs; and caregivers of in-
Malaria is caused by four species of protozoa of the genus
fected people. PCP is a common cause of death in people
Plasmodium. The human being is the only natural reservoir
of these parasites. All types of malaria are transmitted onlyby Anopheles mosquitoes. Plasmodium vivax, Plasmodiummalariae, and Plasmodium ovale cause recurrent malaria by
forming reservoirs in the human host. In these types ofmalaria, signs and symptoms may occur months or years after
Toxoplasmosis is caused by Toxoplasma gondii, a parasite
the initial attack. Plasmodium falciparum causes the most life-
spread by ingesting undercooked meat or other food contain-
threatening type of malaria but does not form a reservoir. This
ing encysted forms of the organism, by contact with feces from
type of malaria may be cured and prevented from recurring.
infected cats, and by congenital spread from mothers with
Plasmodia have a life cycle in which one stage of devel-
acute infection. Once infected, the organism may persist in tis-
opment occurs within the human body. When a mosquito
sue cysts for the life of the host. However, symptoms rarely
bites a person with malaria, it ingests blood that contains ga-
occur unless the immune system is impaired or becomes im-
metocytes (male and female forms of the protozoan parasite).
paired at a later time. Although symptomatic infection may
From these forms, sporozoites are produced and transported
occur in anyone with immunosuppression (eg, people with
to the mosquito’s salivary glands. When the mosquito bites
cancer or organ transplantation), it is especially common and
serious in people with AIDS, in whom it often causes en-
Scabies and pediculosis are parasitic infestations of the skin. Scabies is caused by the itch mite (Sarcoptes scabiei), which
burrows into the skin and lays eggs that hatch in 4 to 8 days. The burrows may produce visible skin lesions, most often be-
The most common form of trichomoniasis is a vaginal in-
tween the fingers and on the wrists.
fection caused by Trichomonas vaginalis. The disease is
Pediculosis may be caused by one of three types of lice.
usually spread by sexual intercourse. Antitrichomonal drugs
Pediculosis capitis (head lice) is the most common type of
may be administered systemically (ie, metronidazole) or ap-
pediculosis in the United States. It is diagnosed by finding
plied locally as douche solutions or vaginal creams.
louse eggs (nits) attached to hair shafts close to the scalp. Pediculosis corporis (body lice) is diagnosed by finding lice
in clothing, especially in seams. Body lice can transmit ty-phus and other diseases. Pediculosis pubis (pubic or crab lice)
Helminthiasis, or infestation with parasitic worms, is a com-
is diagnosed by the presence of nits in the pubic and genital
mon finding in many parts of the world. Helminths are most
areas. Occasionally, pubic lice may infest the axillae, mustache,
often found in the gastrointestinal (GI) tract. However, sev-
or eyelashes. Pediculosis may infect persons of any socio-
eral types of parasitic worms penetrate body tissues or pro-
economic status. Although scabies and pediculosis are caused
duce larvae that migrate to the blood, lymph channels, lungs,
by different parasites, the conditions have several common
liver, and other body tissues. Helminthic infections are de-
• They are more likely to occur in areas of poverty, over-
Drugs used for treatment of helminthiasis are called an-
crowding, and poor sanitation. However, they may
thelmintics. Most anthelmintics act locally to kill or cause
occur in any geographic area and socioeconomic group.
expulsion of parasitic worms from the intestines; some an-
• They are highly communicable and transmitted by direct
thelmintics act systemically against parasites that have pene-
contact with an infected person or the person’s personal
trated various body tissues. The goal of anthelmintic therapy
effects (eg, clothing, combs and hairbrushes, bed linens).
may be to eradicate the parasite completely or to decrease the
• Pruritus is usually the major symptom. It results from an
magnitude of infestation (“worm burden”).
allergic reaction to parasite secretions and excrement. In
BOX 41–1 HELMINTHIC INFECTIONS Hookworm infections are caused by Necator americanus, a Tapeworms attach themselves to the intestinal wall and may
species found in the United States, and Ancylostoma duodenale,
grow as long as several yards. Segments called proglottids, which
a species found in Europe, the Middle East, and North Africa.
contain tapeworm eggs, are expelled in feces. Tapeworms are
Hookworm is spread by ova-containing feces from infected peo-
transmitted by ingestion of contaminated, raw, or improperly
ple. Ova develop into larvae when deposited on the soil. Larvae
cooked beef, pork, or fish. Beef and fish tapeworm infections are
burrow through the skin (eg, if the person walks on the soil with
not usually considered serious illnesses. Pork tapeworm, which is
bare feet), enter blood vessels, and migrate through the lungs to
uncommon in the United States, is more serious because it pro-
the pharynx, where they are swallowed. Larvae develop into adult
duces larvae that enter the bloodstream and migrate to other body
hookworms in the small intestine and attach themselves to the
tissues (ie, muscles, liver, lungs, and brain). Threadworm infections (strongyloidiasis), caused by Strongy- Pinworm infections (enterobiasis), caused by Enterobius ver- loides stercoralis, are potentially serious infections. This worm
micularis, are the most common parasitic worm infections in the
burrows into the mucosa of the small intestine, where the female
United States. They are highly communicable and often involve
lays eggs. The eggs hatch into larvae that can penetrate all body
school children and household contacts. Infection occurs from con-
tact with ova in food or water or on bed linens. The female pinworm
Trichinosis, a parasitic worm infection caused by Trichinella
migrates from the bowel to the perianal area to deposit eggs, espe-
spiralis, occurs worldwide. It is caused by ingestion of inade-
cially at night. Touching or scratching the perianal area deposits
quately cooked meat, especially pork. Encysted larvae are ingested
ova on hands and any objects touched by the contaminated hands.
in infected pork. In the intestine, the larvae excyst, mature, and
Roundworm infections (ascariasis), caused by Ascaris lum-
produce eggs that hatch into new larvae. The larvae enter blood
bricoides, are the most common parasitic worm infections in the
and lymphatic vessels and are transported throughout the body.
world. They occur most often in tropical regions but may occur
They penetrate various body tissues (eg, muscles and brain) and
wherever sanitation is poor. The infection is transmitted by ingest-
evoke inflammatory reactions. Eventually, the larvae are re-
ing food or water contaminated with feces from infected people.
encysted or walled off in the tissues and may remain for 10 years
Ova are swallowed and hatch into larvae in the intestine. The lar-
vae penetrate blood vessels and migrate through the lungs before
Whipworm infections (trichuriasis) are caused by Trichuris
returning to the intestines, where they develop into adult worms. trichiura. Whipworms attach themselves to the wall of the colon.
addition to the intense discomfort associated with pru-
ritus, scratching is likely to cause skin excoriation withsecondary bacterial infection and formation of vesicles,
Chloroquine is a widely used antimalarial agent. It acts
against erythrocytic forms of plasmodial parasites to prevent
• They are treated with many of the same topical med-
or treat malarial attacks. When used for prophylaxis, it is
given before, during, and after travel or residence in endemicareas. When used for treatment of malaria caused by P. vivax,P. malariae, or P. ovale, chloroquine relieves symptoms of
the acute attack. However, the drug does not prevent recur-rence of malarial attacks because it does not act against the
Antiparasitic drugs include amebicides, antimalarials, other
tissue (exoerythrocytic) forms of the parasite. When used for
antiprotozoal agents, anthelmintics, scabicides, and pediculi-
treatment of malaria caused by P. falciparum, chloroquine re-
cides. Their descriptions are in the following text and are also
lieves symptoms of the acute attack and eliminates the para-
listed in Drugs at a Glance: Antiparasitics.
site from the body because P. falciparum does not have tissuereservoirs. Concern about chloroquine-resistant strains of P. falciparum has developed in many areas.
Chloroquine is also used in protozoal infections other than
malaria, including extraintestinal amebiasis and giardiasis. It
Chloroquine (Aralen) is used primarily for its antimalarial ef-
should be used with caution in patients with hepatic disease
fects. When used as an amebicide, the drug is effective in ex-
or severe neurologic, GI, or blood disorders.
traintestinal amebiasis (ie, hepatic amebiasis) but usually
Hydroxychloroquine (Plaquenil) is a derivative of chloro-
ineffective in intestinal amebiasis. The phosphate salt is given
quine with essentially the same actions, uses, and adverse
orally. When the oral route is contraindicated, severe nausea
effects as chloroquine. It has also been used to treat rheuma-
and vomiting occur, or the infection is severe, the hydro-
toid arthritis and lupus erythematosus.
chloride salt can be given intramuscularly. Treatment is usually
Chloroquine with primaquine is a mixture available in
combined with an intestinal amebicide.
tablets containing chloroquine phosphate 500 mg (equiva-
Iodoquinol (Yodoxin) is an iodine compound that acts
lent to 300 mg of chloroquine base) and primaquine phos-
against active amebae (trophozoites) in the intestinal lumen.
phate 79 mg (equivalent to 45 mg of primaquine base). This
It may be used alone in asymptomatic intestinal amebiasis to
combination is effective for prophylaxis of malaria and may
decrease the number of amebic cysts passed in the feces.
be more acceptable to clients. It also may be more conve-
When given for symptomatic intestinal amebiasis (eg, ame-
nient for use in children because no pediatric formulation of
bic dysentery), it is usually given with other amebicides in
concurrent or alternating courses. Iodoquinol is ineffective in
Halofantrine (Halfan) is indicated for treatment of malaria
amebic hepatitis and abscess formation. Its use is contraindi-
caused by P. falciparum or P. vivax, including chloroquine-
cated with iodine allergy and liver disease. Metronidazole (Flagyl) is effective against protozoa that Mefloquine (Lariam) is used to prevent P. falciparum
cause amebiasis, giardiasis, and trichomoniasis and against
malaria, including chloroquine-resistant strains, and to treat
anaerobic bacilli, such as Bacteroides and Clostridia (see
acute malaria caused by P. falciparum or P. vivax.
Chap. 37). In amebiasis, metronidazole is amebicidal at in-
Primaquine is used to prevent the initial occurrence of
testinal and extraintestinal sites of infection. It is a drug of
malaria; to prevent recurrent attacks of malaria caused by
choice for all forms of amebiasis except asymptomatic in-
P. vivax, P. malariae, and P. ovale; and to achieve “radical
testinal amebiasis (in which amebic cysts are expelled in the
cure” of these three types of malaria. (Radical cure involves
feces). In trichomoniasis, metronidazole is the only systemic
eradicating the exoerythrocytic forms of the plasmodium and
trichomonacide available and it is more effective than any lo-
preventing the survival of the blood forms.) The clinical use-
cally active agent. Because trichomoniasis is transmitted by
fulness of primaquine stems primarily from its ability to destroy
sexual intercourse, partners should be treated simultaneously
tissue (exoerythrocytic) forms of the malarial parasite. Pri-
maquine is especially effective in P. vivax malaria. Thus far,
Metronidazole is usually contraindicated during the first
plasmodial strains causing the three relapsing types of malaria
trimester of pregnancy and must be used with caution in patients
have not developed resistance to primaquine. When used to
with central nervous system (CNS) or blood disorders. Patients
prevent initial occurrence of malaria (causal prophylaxis),
should also avoid all forms of ethanol while on this medication.
primaquine is given concurrently with a suppressive agent
Tetracycline and doxycycline are antibacterial drugs (see
(eg, chloroquine or hydroxychloroquine) after the patient has
Chap. 36) that act against amebae in the intestinal lumen by
returned from a malarious area. Primaquine is not effective
altering the bacterial flora required for amebic viability. One
for treatment of acute attacks of malaria.
of these drugs may be used with other amebicides in the treat-
Pyrimethamine (Daraprim) is a folic acid antagonist used
ment of all forms of amebiasis except asymptomatic intesti-
to prevent malaria caused by susceptible strains of plasmodia.
meals for 20 d; repeat after 2 to 3 wk if necessary
times daily for 7 d, 1 g twice dailyfor 1 d, or 2 g in a single dose. Re-peat after 4 to 6 wk, if necessary. Gardnerella vaginalis vaginitis, PO
initially, then 500 mg (300 mg ofbase) after 6 to 8 h, then 500 mgdaily for 2 d (total of 2.5 g in four doses)
weighing 25–45 kg. For youngerchildren, a suspension is prepared(eg, 40 mg of chloroquine and 6 mgof primaquine in 5 mL). Dosagesare then 2.5 mL for children weigh-ing 5 to 7 kg, 5 mL for 8 to 11 kg,7.5 mL for 12 to 15 kg, 10 mL for16 to 20 kg, and 12.5 mL for 21 to24 kg. Dosages are given weeklyfor 2 wk before entering and 8 wkafter leaving malarious areas.
Drugs at a Glance: Antiparasitic Drugs (continued )
11–40 kg: Prophylaxis, 1 to 3 pedi-
<40 kg: PO 8 mg/kg according to the
a malarious area, or 79 mg (45 mgof base) once a week for 8 wk. Toprevent relapse, the same dose isgiven with chloroquine or a relateddrug daily for 14 d. Anti–Pneumocystis carinii Agents
(based on trimethoprim) q6–8 h,for up to 14 d; PO 15–20 mg/kgTMP/100 mg/kg SMX per day, individed doses, q6h, for 14–21 d
Drugs at a Glance: Antiparasitic Drugs (continued )
as a single dose; for hookworms,the same dose is given daily for 3 consecutive days.
2 d for other infections, excepttrichinosis, which requires approxi-mately 5 d
≥5 years: 150 mcg/kg as a single dose
skin over the entire body except theface, leave on for 8–14 h, wash off.
ing, rinsing, and towel drying hair.
leave in place for 24 h, then removeby shower
affected area, leave in place for12 h, then wash or shampoo (rubinto the affected area for 4 minand rinse thoroughly)
comb hair with a fine-toothed combto remove dead lice and eggs. Ifnecessary, treatment can be re-peated in 7–9 d.
It is sometimes used with a sulfonamide and quinine to treat
used in the treatment of chloroquine-resistant P. falciparum
chloroquine-resistant strains of P. falciparum. Folic acid an-
malaria, usually in conjunction with pyrimethamine and a
tagonists and sulfonamides act synergistically against plas-
sulfonamide. Quinine also relaxes skeletal muscles and has
modia because they block different steps in the synthesis of
been used for prevention and treatment of nocturnal leg
folic acid, a nutrient required by the parasites. Quinine (Quinamm) is derived from the bark of the cin- Malarone is a new combination antimalarial medication
chona tree. Quinine was the primary antimalarial drug for
containing 250 mg of atovaquone and 100 mg of proguanil
many years but has been largely replaced by synthetic agents
per tablet. This product may be used for both the prevention
that cause fewer adverse reactions. However, it may still be
and treatment of malarial infections, particularly those caused
by P. falciparum. The drug also seems to be effective in
creatinine, blood urea nitrogen, blood glucose, serum cal-
chloroquine-resistant areas and is devoid of many of the side
effects of mefloquine. Two drugs are combined to inhibit sep-arate pathways involved in the synthesis of nucleic acids bythe offending parasite. The drug should be taken daily with
food or milk starting 1 to 2 days before entering an endemicarea and for 7 days upon return. Mebendazole (Vermox) is a broad-spectrum anthelmintic used in the treatment of parasitic infections by hookworms, pinworms, roundworms, and whipworms. It is also useful
but less effective in tapeworm infection. Mebendazole killshelminths by preventing uptake of the glucose necessary for
Trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim,
parasitic metabolism. The helminths become immobilized
others) (see Chap. 36) is the drug of choice for prevention
and die slowly, so they may be expelled from the GI tract up
and treatment of PCP. Prophylaxis is indicated for adults
to 3 days after drug therapy is completed. Mebendazole acts
and adolescents with HIV and CD4+ cell counts <200;
locally in the GI tract, and less than 10% of the drug is ab-
organ transplant recipients; patients with leukemia or lym-
phoma who are receiving cytotoxic chemotherapy; and for
Mebendazole is usually the drug of choice for single or
patients receiving high doses of corticosteroids (equivalent
mixed infections caused by the aforementioned parasitic
to 20 mg or more daily of prednisone) for prolonged periods
worms. The drug is contraindicated during pregnancy be-
cause of teratogenic effects in rats; it is relatively con-
Common adverse effects include nausea, vomiting, and
traindicated in children younger than 2 years of age because
skin rash. These effects are more common in patients who are
it has not been extensively investigated for use in this age
Atovaquone (Mepron) is used for both prophylaxis and Pyrantel (Antiminth) is effective in infestations of round-
treatment of PCP in people who are unable to take TMP-SMX.
worms, pinworms, and hookworms. The drug acts locally to
Adverse effects include nausea, vomiting, diarrhea, fever, in-
paralyze worms in the intestinal tract. Pyrantel is poorly ab-
somnia, and elevated hepatic enzymes.
sorbed from the GI tract, and most of an administered dose
Dapsone may be used for the prophylaxis of PCP infec-
may be recovered in feces. Pyrantel is contraindicated in
tion in HIV-seropositive patients who are unable to tolerate
pregnancy and is not recommended for children younger than
TMP-SMX. Patients who are glucose-6-phosphate dehydro-
genase (G6PD) deficient will develop hemolytic anemia and
Thiabendazole (Mintezol) is most effective against thread-
therefore this laboratory parameter should be assessed before
worms and pinworms. It is useful but less effective against
initiating therapy. Common side effects include nausea/
hookworms, roundworms, and whipworms. Because of the
broad spectrum of anthelmintic activity, thiabendazole may be
Trimetrexate (Neutrexin) is a folate antagonist (which
especially useful in mixed parasitic infestations. In trichinosis,
must be used with leucovorin rescue) approved only for treat-
thiabendazole decreases symptoms and eosinophilia but does
ment of moderate to severe PCP in immunocompromised pa-
not eliminate larvae from muscle tissues. The mechanism of
tients, including those with advanced HIV infection who are
anthelmintic action is uncertain but probably involves inter-
unable to take TMP-SMX. Hematologic toxicity is the main
ference with parasitic metabolism. The drug is relatively toxic
dose-limiting adverse effect. To minimize hematologic ef-
compared with other anthelmintic agents.
fects, leucovorin should be given daily during trimetrexate
Thiabendazole is a drug of choice for threadworm infes-
therapy and for 72 hours after the last trimetrexate dose.
tations. For other types of helminthiasis, it is usually consid-
Dosage of trimetrexate must be reduced, and dosage of leu-
ered an alternative drug. It is rapidly absorbed after oral
covorin must be increased with significant neutropenia or
administration and most of the drug is excreted in urine
within 24 hours. It should be used with caution in clients with
Pentamidine (Pentam 300, NebuPent) may be used both
for prophylaxis and treatment of PCP infection. Pentamidine
Ivermectin (Stromectol) is used for numerous parasitic
interferes with production of ribonucleic acid (RNA) and de-
infections and is most active against strongyloidiasis. Iver-
oxyribonucleic acid (DNA) by the organism. The drug is
mectin has also been used for the oral treatment of resistant
given parenterally for treatment of PCP and by inhalation for
lice. The drug has relatively few side effects but may cause
prophylaxis. It is excreted by the kidneys and accumulates in
the presence of renal failure, so dosage should be reduced inpatients with renal impairment. Clinicians should also beaware that the intravenous (IV) form of pentamidine is par-
ticularly pancreotoxic. With parenteral pentamidine, appro-priate tests should be performed before, during, and after
Permethrin is the drug of choice for both pediculosis and sca-
treatment (eg, complete blood count, platelet count, serum
bies. Although a single application eliminates parasites and
ova, two applications are generally recommended. For pedicu-
sexual partners need simultaneous treatment to prevent
losis, permethrin is available as a 1% over-the-counter liquid
(Nix). For scabies, a 5% cream permethrin cream (Elimite) is
• With pubic (crab) lice, assess sexual activity. Lice may
available by prescription. For scabies, a single application of
be transmitted by sexual and other close contact and by
5% permethrin cream is considered curative. Permethrin is
safer than other scabicides and pediculicides, especially for
• Assess for signs and symptoms. These vary greatly, de-
pending on the type and extent of parasitic infestation.
Permethrin is derived from a chrysanthemum plant, and
• Amebiasis. The person may be asymptomatic, have
people with a history of allergy to ragweed or chrysanthemum
nausea, vomiting, diarrhea, abdominal cramping, and
flowers should use it cautiously. The most frequent adverse
weakness, or experience symptoms from ulcerations of
the colon or abscesses of the liver (amebic hepatitis) if
To avoid reinfection, close contacts should be treated
the disease is severe, prolonged, and untreated. Ame-
simultaneously. With pediculosis, clothing and bedding
biasis is diagnosed by identifying cysts or trophozoites
should be sterilized by boiling or steaming and seams
of E. histolytica in stool specimens.
of clothes should be examined to verify that all lice are
• Malaria. Initial symptoms may resemble those produced
by influenza (eg, headache, myalgia). Characteristic
Gamma benzene hexachloride (Lindane) is a second-
paroxysms of chills, fever, and copious perspiration may
line drug for scabies and pediculosis. It may be used for
not be present in early malaria. During acute malarial at-
people who have hypersensitivity reactions or resistance to
tacks, the cycles occur every 36 to 72 hours. Additional
treatment with permethrin. It is applied topically, and sub-
symptoms include nausea and vomiting, splenomegaly,
stantial amounts are absorbed through intact skin. CNS toxi-
hepatomegaly, anemia, leukopenia, thrombocytopenia,
city has been reported with excessive use, especially in infants
and hyperbilirubinemia. Malaria is diagnosed by identi-
and children. The drug is available in a 1% concentration in
fying the plasmodial parasite in peripheral blood smears
Malathion (Ovide) is a pediculicide particularly used
• Trichomoniasis. Women usually have vaginal burning,
in the treatment of head lice, and Pyrethrin preparations
itching, and yellowish discharge; men may be asympto-
(eg, Barc, RID) are available over the counter as gels, sham-
matic or have symptoms of urethritis. The condition is
poos, and liquid suspensions for treatment of pediculosis.
diagnosed by finding T. vaginalis organisms in a wet
Crotamiton (Eurax) is sometimes used as a 10% cream or
smear of vaginal exudate, semen, prostatic fluid, or uri-
nary sediment (by microscopic examination). Culturesmay be necessary.
• Helminthiasis. Light infestations may be asymptomatic.
Heavy infestations produce symptoms according to theparticular parasitic worm. Hookworm, roundworm,
and threadworm larvae migrate through the lungs andmay cause symptoms of pulmonary congestion. The
hookworm may cause anemia by feeding on blood fromthe intestinal mucosa; the fish tapeworm may cause
Assess for conditions in which antiparasitic drugs are used.
megaloblastic or pernicious anemia by absorbing folic
• Assess for exposure to parasites. Although exposure is in-
acid and vitamin B12. Large masses of roundworms or
fluenced by many variables (eg, geographic location, per-
tape-worms may cause intestinal obstruction. The major
sonal hygiene, environmental sanitation), some useful
symptom usually associated with pinworms is intense
itching in the perianal area (pruritus ani). Helminthi-
• Does the person live in an institution, an area of poor
asis is diagnosed by microscopic identification of par-
sanitation, an underdeveloped country, a tropical re-
asites or ova in stool specimens. Pinworm infestation
gion, or an area of overcrowded housing? These con-
is diagnosed by identifying ova on anal swabs, ob-
ditions predispose to parasitic infestations with lice,
tained by touching the sticky side of cellophane tape
to the anal area. (Early-morning swabs are best be-
• Are parasitic diseases present in the person’s environ-
cause the female pinworm deposits eggs during sleep-
ment? For example, head lice, scabies, and pinworm in-
festations often affect school children and their families.
• Scabies and pediculosis. Pruritus is usually the primary
• Has the person recently traveled (within the previous
symptom. Secondary symptoms result from scratching
1 to 3 weeks) in malarious regions? If so, were pro-
and often include skin excoriation and infection (ie, vesi-
cles, pustules, and crusts). Pediculosis is diagnosed by
• With vaginal trichomoniasis, assess in relation to sexual
visual identification of lice or ova (nits) on the client’s
activity. The disease is spread by sexual intercourse, and
and brushes should be cleaned and disinfected; carpetsand upholstered furniture should be vacuumed.
• Deficient Knowledge: Management of disease process
• With pinworms, clothing, bed linens, and towels should
be washed daily on hot cycles. Toilet seats should be dis-
• Deficient Knowledge: Accurate drug administration
• Imbalanced Nutrition: Less Than Body Requirements
• Ensure follow-up measures, such as stool specimens,
related to parasitic disease or drug therapy
vaginal examinations, anal swabs, smears, and cul-
• Self-Esteem Disturbance related to a medical diagnosis
• With vaginal infections, avoid sexual intercourse, or
• Noncompliance related to need for hygienic and other
measures to prevent and treat parasitic infestations
• Interview and observe for relief of symptoms.
• Interview outpatients regarding compliance with instruc-
• Experience relief of symptoms for which antiparasitic
tions for taking antiparasitic drugs and measures to prevent
• Interview and observe for adverse drug effects.
• Interview and observe regarding food intake or changes
Use measures to avoid exposure to or prevent transmissionof parasitic diseases.
• Environmental health measures include the following:
• Sanitary sewers to prevent deposition of feces on surface
1. Antiparasitic drugs should be used along with personal
soil and the resultant exposure to helminths
and public health control measures to prevent the
• Monitoring of community water supplies, food-handling
spread of parasitic infestations. Specific measures vary
establishments, and food-handling personnel
according to the type of organism, the environment,
• Follow-up examination and possibly treatment of
household and other close contacts of people with
2. Many of the drugs described in this chapter are quite
helminthiasis, amebiasis, trichomoniasis, scabies, and
toxic; they should be used only when clearly indicated
(ie, laboratory documentation of parasitic infection).
• Mosquito control in malarious areas and prophylactic
drug therapy for travelers to malarious areas. In addition,teach travelers to decrease exposure to mosquito bites
(eg, wear long-sleeved, dark clothing; use an effectiveinsect repellent such as DEET; and sleep in well-
Children often receive an antiparasitic drug for head lice or
screened rooms or under mosquito netting). These
worm infestations. These products should be used exactly
measures are especially needed at dusk and dawn, the
as directed and with appropriate precautions to prevent re-
maximal feeding times for mosquitoes.
infection. Malaria is usually more severe in children than in
• Personal and other health measures include the following:
adults, and children should be protected from exposure
• Maintain personal hygiene (ie, regular bathing and
when possible. When chemoprophylaxis or treatment for
shampooing, handwashing before eating or handling
malaria is indicated, the same drugs are used for children as
food and after defecation or urination).
• Avoid raw fish and undercooked meat. This is espe-
cially important for anyone with immunosuppression.
• Avoid contaminating streams or other water sources
Nursing Notes: Apply Your Knowledge
• Control flies and avoid foods exposed to flies. • With scabies and pediculosis infestations, drug therapy
You are a nurse in a travel clinic. Sally and Bill, college stu-
must be accompanied by adjunctive measures to avoid
dents, plan to spend part of their summer vacation traveling in
reinfection or transmission to others. For example, close
Africa. You update their immunizations and then talk with
contacts should be examined carefully and treated if
them about malaria prevention. The physician has written
indicated. Clothes, bed linens, and towels should be
a prescription for chloroquine phosphate and primaquine,
washed and dried on hot cycles. Clothes that cannot be
1 tablet every week. What information would you include in
washed should be dry cleaned. With head lice, combs
CLIENT TEACHING GUIDELINESAntiparasitic Drugs
✔ Take atovaquone, chloroquine and related drugs, iodo-
quinol, and oral metronidazole with or after meals. Food
✔ Use measures to prevent parasitic infection or reinfection:
increases absorption of atovaquone and decreases
✔ Support public health measures to maintain a clean
gastrointestinal irritation of the other drugs.
environment (ie, sanitary sewers, clean water, regula-
✔ To use pentamidine by inhalation, dissolve the contents of
tion of food-handling establishments and food-handling
one vial in 6 mL of sterile water, place the solution in the
nebulizer chamber of a Respirgard II device, and deliver by
✔ When traveling to wilderness areas or to tropical or
way of oxygen or compressed air flow until the nebulizer
underdeveloped countries, check with the local health
chamber is empty (approximately 30 to 45 minutes).
department about precautions needed to avoid para-
✔ Take or give most anthelmintics without regard to meal-
times or food ingestion. Mebendazole tablets should be
✔ Practice good hand washing and other personal
chewed or crushed and mixed with food; thiabendazole
should be taken with food to decrease stomach upset.
✔ When a family member or other close contact con-
Chew chewable tablets thoroughly before swallowing.
tracts a parasitic infection, be sure appropriate treat-
✔ Use pediculicides and scabicides as directed on the label
ment and follow-up care are completed.
or product insert. Instructions vary among preparations.
✔ Avoid raw fish and undercooked meat. ✔ With vaginal infections, avoid sexual intercourse, or
✔ Use antiparasitic drugs as prescribed; their effectiveness
for adults, with appropriate dosage adjustments. An excep-
tion is that tetracyclines should not be given to childrenyounger than 8 years of age.
Most antiparasitic drugs are given primarily in the home set-ting. The home care nurse may need to examine close contactsof the infected person and assess his or her need for treatment,
assist parents and clients so that drugs are used appropriately,and teach personal and environmental hygiene measures to
Older adults are more likely to experience adverse effects of
prevent reinfection. When children have parasitic infestations,
antiparasitic drugs because they often have impaired renal
the home care nurse may need to collaborate with day care cen-
ters and schools to prevent or control outbreaks. NURSING ACTIONS RATIONALE/EXPLANATION 1. Administer accurately a. Give atovaquone, chloroquine and related drugs, iodoquinol,
Food improves absorption of atovaquone and decreases gastro-
and oral metronidazole with or after meals.
intestinal (GI) irritation of the other drugs. b. With pentamidine:
(1) For intravenous administration, dissolve the calculateddose in 3–5 mL of sterile water or 5% dextrose in water. Dilute further with 50–250 mL of 5% dextrose solutionand infuse over 60 min. c. Give anthelmintics without regard to mealtimes or food
Food in the GI tract does not decrease effectiveness of most
ingestion. Mebendazole tablets may be chewed, swallowed,
NURSING ACTIONS RATIONALE/EXPLANATION d. For pediculicides and scabicides, follow the label or manu-
Instructions vary among preparations. 2. Observe for therapeutic effects a. With chloroquine for acute malaria, observe for relief of
Fever and chills usually subside within 24–48 h, and blood smears
are negative for plasmodia within 24 –72 h. b. With amebicides, observe for relief of symptoms and neg-
Relief of symptoms does not indicate cure of amebiasis; laboratory
evidence is required. Stool specimens should be examined for ame-bic cysts and trophozoites periodically for approximately 6 mo. c. With anti–Pneumocystis carinii agents for prophylaxis, observe for absence of symptoms; when used for treatment, observe for decreased fever, cough, and respiratory distress. d. With anthelmintics, observe for relief of symptoms, ab-
The goal of anthelmintic drug therapy may be complete eradica-
sence of the parasite in blood or stool for three consecutive
tion of the parasite or reduction of the “worm burden.”
examinations, or a reduction in the number of parasitic ova inthe feces. e. With pediculicides, inspect affected areas for lice or nits.
For most clients, one treatment is effective. For others, a secondtreatment may be necessary. 3. Observe for adverse effects a. With amebicides, observe for anorexia, nausea, vomiting,
GI effects may occur with all amebicides.
(1) With iodoquinol, observe for agitation, amnesia,
These effects are most likely to occur with large doses or long-
peripheral neuropathy, and optic neuropathy. b. With antimalarial agents, observe for nausea, vomiting,
These effects may occur with most antimalarial agents. However,
diarrhea, pruritus, skin rash, headache, central nervous system
adverse effects are usually mild because small doses are used for
prophylaxis, and the larger doses required for treatment of acutemalarial attacks are given only for short periods.
(1) With pyrimethamine, observe for anemia, thrombocy-
This drug interferes with folic acid metabolism.
(2) With quinine, observe for signs of cinchonism (headache,
These effects occur with usual therapeutic doses of quinine. They
tinnitus, decreased auditory acuity, blurred vision).
do not usually necessitate discontinuance of quinine therapy. c. With metronidazole, observe for convulsions, peripheral
CNS effects are most serious; GI effects are most common.
paresthesias, nausea, diarrhea, unpleasant taste, vertigo,headache, and vaginal and urethral burning sensation. d. With parenteral pentamidine, observe for leukopenia, throm-
Severe hypotension may occur after a single parenteral dose.
bocytopenia, hypoglycemia, hyperglycemia, hypocalcemia,
Deaths from hypotension, hypoglycemia, and cardiac arrhythmias
hypokalemia, hypotension, acute renal failure. e. With aerosolized pentamidine, observe for fatigue, short-
These are the most common adverse effects.
ness of breath, bronchospasm, cough, dizziness, rash, anorexia,nausea, vomiting, chest pain. f. With atovaquone, observe for nausea, vomiting, diarrhea, fever, headache, skin rash. g. With trimetrexate, observe for anemia, neutropenia, throm- bocytopenia, increased bilirubin and liver enzymes (aspartate and alanine aminotransferases, alkaline phosphatase), fever, skin rash, pruritus, nausea, vomiting, hyponatremia, hypocalcemia. h. With topical antitrichomonal agents, observe for hypersensi-
Hypersensitivity reactions are the major adverse effects. Other
tivity reactions (eg, rash, inflammation), burning, and pruritus.
effects are minor and rarely require that drug therapy be dis-continued. NURSING ACTIONS RATIONALE/EXPLANATION i. With permethrin, observe for pruritus, burning, or tingling;
Antihistamines or topical corticosteroids may be used to decrease
with Lindane, observe for CNS stimulation (nervousness,
itching. CNS toxicity is more likely to occur with excessive use of
Lindane (ie, increased amounts, leaving in place longer than pre-scribed, or applying more frequently than prescribed). 4. Observe for drug interactions
Few clinically significant drug interactions occur because manyantiparasitic agents are administered for local effects in the GI tractor on the skin. Most of the drugs also are given for short periods. a. Drugs that alter effects of chloroquine:
(1) Acidifying agents (eg, ascorbic acid)
Inhibit chloroquine by increasing the rate of urinary excretion
(2) Alkalinizing agents (eg, sodium bicarbonate)
Potentiate chloroquine by decreasing the rate of urinary excretion
Increase risk of toxicity and retinal damage by inhibiting metab-olism. b. Drugs that alter effects of metronidazole:
These drugs induce hepatic enzymes and decrease effects ofmetronidazole by accelerating its rate of hepatic metabolism.
May increase effects by inhibiting hepatic metabolism of metro-nidazole. c. Drugs that decrease effects of atovaquone and trimetrexate:
Although few interactions have been reported, any enzyme-
Rifampin and other drugs that induce CYP450 drug-metabo-
inducing drug can potentially decrease effects of atovaquone and
trimetrexate by accelerating their metabolism in the liver. 4. How can you assess a client’s personal hygiene practices Nursing Notes: Apply Your Knowledge 5. How would you instruct a mother regarding treatment Answer: Explain that malaria is transmitted by mosquito bites,
and prevention of reinfection with head lice or pin-
and thus it is important to limit exposure to mosquitoes (by
using insect repellent, wearing long pants and long-sleeve
6. What are adverse effects of commonly used antipara-
shirts, sleeping in screened or well-netted areas). Mosquitoes
sitic drugs, and how might they be prevented or mini-
are most active at dusk and dawn, so prevention is especially
important at these times. Prophylactic medications must bestarted 2 weeks before entering infested areas and continued for8 weeks after return. The medication should be taken on the sameday of the week at approximately the same time. If acute symp-
toms appear (headache, malaise, fever, chills), additional medica-tion can be taken to treat the infection. Clear, written instructions
Bartels, C. L, Peterson, K. E., & Taylor, K. L. (2001). Head lice resis-
regarding the dosage should be provided.
tance: Itching that just won’t stop. Annals of Pharmacotherapy, 35,109–112.
Burkhart, C. N. & Burkhart, C. G. (1999). Another look at ivermectin in the
treatment of scabies and head lice. International Journal of Dermatology,38: 235.
Drugs for head lice. (1999). Medical Letters on Drugs and Therapeutics,1. What groups are at risk for development of parasitic infec-
Greenwood, B. & Mutabingwa, T. (2002). Malaria in 2002. Nature, 415,
tions (eg, amebiasis, malaria, pediculosis, helminthiasis)?
Schachner, L. A. (1997). Treatment resistant head lice: Alternative thera-
2. What interventions are needed to prevent parasitic
peutic approaches. Pediatric Dermatology, 14, 409–410.
Sepkowitz, K. A. (2002). Opportunistic infections in patients with and pa-
tients without acquired immunodeficiency syndrome. Clinical Infectious3. How would you assess for a parasitic infection in a client
who has been in an environment associated with a partic-
Winstanley, P. (2001). Modern chemotherapeutic options for malaria. Lancet Infectious Diseases, 1, 242–250.
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