Nematodes Roundworms

Angiostrongyliasis costaricensis (Anisakiasis)

Angiostrongyliasis costaricensis causes an eosinophilic ileo-colitis. Infection occurs following ingestion of larva in the intermediate host (slug, snails) or from food contaminated by larvae from slug or snail mucus. Clinically, it can present as fever, right lower quadrant pain, abdominal mass, leukocytosis, and eosinophilia. Complications such as perforation, bleeding, intestinal obstruction, or infarction can occur. There is no specific treatment; mebendazole, alben-dazole, or thiabendazole can be tried and operative treatment may be necessary.

Ascaris lumbricoides (Ascariasis)

With an estimated 1 billion people infected worldwide, it is among the most common intestinal helminthes. Adult worms can reach up to 20 to 40 cm. Clinically, if the worm burden is small then no symptoms are apparent. With heavy worm burden, peptic ulcer-like symptoms and vague abdominal discomfort can occur. Rarely, the worms migrate to other areas of the abdomen and the respiratory tract. Treatment of choice is albendazole, mebendazole or pyrantel pamoate, with cure rates of 85 to 100% (Bennett and Guyatt, 2000). A word of caution, treatment with anti-helminthics or anasthesia can cause the worms to migrate. In pregnancy, treatment should occur after the first trimester. stools should be rechecked at 2 weeks and patients retreated until all worms are removed.

Enterobius vermicularis (Pinworm)

Children are the most commonly infected. Clinically, many infections are asymptomatic. But, when symptoms occur, perianal pruritis, especially at night, is most notable. Treatment of all symptomatic persons should occur and in some instances it is recommended to treat household contacts. Treatment is highly effective (95 to 100%), can be taken with or without food, and is easy to administer. The drugs of choice include pyrantel pamoate, which is available as self-medication in the United States, a single dose of albendazole, or a single dose of mebendazole, which should be chewed for best effect.

Necator americanus and Ancylostoma duodenale (Hookworm)

Infections with these hookworms are very common worldwide; up to 25% of the world's population are thought to be infected with these parasites. The infection can be asymptomatic or can have skin, pulmonary or intestinal manifestations; in heavy worm burden, iron-deficient anemia is a common consequence of hookworm infection. Mebendazole, pyrantel, and albendazole are all highly efficacious treatments. All 3 drugs can be given for 1 to 3 days depending on worm burden. Ferrous sulfate is also recommended for 1 to 3 months if anemia is present.

Strongyloides stercoralis (Strongyloidiasis)

Approximately 60 million persons are infected worldwide and the disease is most common in immigrants from endemic areas. The parasite has a unique autoinfection cycle that can result in years of self-perpetuating chronic infection. Up to 30% of infections are asymptomatic. However, cutaneous, pulmonary, intestinal and hyperin-fection syndromes can occur and range in severity. Diagnosis can be difficult but ELISA and Western blot have improved detection of this illness. Ivermectin (200 |g/kg/d for 1 to 2 days) is the drug of choice with cure rates of 82 to 95% (Gann et al, 1994). Alternatively, thiabendazole (50 mg/kg/d in 2 doses for 2 to 3 days, taken after meals, and repeated after 2 weeks) can be used with similar efficacy. However, it has greater potential toxicity (eg, Stephens Johnson). Albendazole (400 mg twice daily for 3 to 7 days and repeated in 1 week) can also be used, but it is less effective. Prolonged treatment, repeat therapy or change in therapy may be needed in those with severe infections or immunosuppression.

Trichostrongylus sp

The clinical symptoms of this parasite infection resemble strongyloides and it can cause eosinophilia. Very rare in the United States, the disease generally occurs in Iran, Korea, and Indonesia. Treatment of choice is with pyrantel pamoate or, alternatively, with mebendazole or albendazole.

Trichuris trichiura (Whipworm)

A common parasite worldwide, whipworm is most prevalent and burdensome in children. Persons with aymptomatic, light infections do not require treatment. For heavier (30,000 or more eggs/g of feces) or symptomatic cases as manifested by abdominal cramps, tenesmus, diarrhea, nausea, and other GI symptoms, mebendazole or albendazole can be used.

Available data on safety of these drugs for use in pregnant or lactating women and young children are summarized in Table 52-3. Common side effects of important drugs are shown in Table 52-4.

TABLE 52-2. Drug Therapy for Intestinal Helminths

Parasite

Drug

Adult Dosage

Pediatric Dosage

Ancylostoma duodenale, Necator americansus(Hookworm)

Drug(s) of choice

Albendazole

400 mg once

400 mg once

Or

Mebendazole

100 mg bid x3d or 500 mg once

100 mg bid x 3 d or 500 mg once

Or

Pyrantel pamoate

11 mg/kg once (max 1 g)

11 mg/kg once (max 1 g)

Ascaris lumbricoides (Ascariasis, roundworm)

Drug(s) of choice

Albendazole

400 mg once

400 mg once

Or

Mebendazole

100 mg bid x3d or 500 mg once

100 mg bid x 3 d or 500 mg once

Or

Pyrantel pamoate

11 mg/kg once (max 1 g)

11 mg/kg once (max 1 g)

Clonorchis silensis (Chinese liver fluke)

Drug(s) of choice

Praziquantel

75 mg/kg/d in 3 doses x 1 d

75 mg/kg/d in 3 doses x 1 d

Or

Albendazole

10 mg/kg x 7 d

10 mg/kg x 7 d

Enterobius vermicularis(Pinworm)

Drug(s) of choice

Pyrantel pamoate

11 mg/kg once (max 1 g); repeat in 2 weeks

11 mg/kg once (max 1 g); repeat in 2 weeks

Or

Mebendazole

100 mg once; repeat in 2 weeks

100 mg once; repeat in 2 weeks

Or

Albendazole

400 mg once; repeat in 2 weeks

400 mg once; repeat in 2 weeks

Fasciolopsishepatica (Sheep liver fluke)

Drug(s) of choice

Triclabendazole

10 mg/kg once

10 mg/kg once

Alternative

Bithionol

30-50 mg/kg x 10-15 doses

30-50 mg/kg on alternate days x 10-15 dos

Fasciolopsis buski, Heterophyes heterophyes, Metagonimus yokogawi(Intestinal flukes)

Drug(s) of choice

Praziquantel

75 mg/kg/d in 3 doses x 1 d

75 mg/kg/d in 3 doses x 1 d

Opisthorchis viverrini(Southeast Asian liver fluke)

Drug(s) of choice

Praziquantel

75 mg/kg/d in 3 doses x 1 d

75 mg/kg/d in 3 doses x 1 d

Schistosoma japonicum, Schistosoma mansoni, Schistosoma mekongi(Schistosomiasis) S. japonicum, S. mekongi

Schistosoma japonicum, Schistosoma mansoni, Schistosoma mekongi(Schistosomiasis) S. japonicum, S. mekongi

Praziquantel

Drug(s) of choice S. mansoni Drug(s) of choice Alternative Strongyloides stercoralis (Strongyloidiasis) Drug(s) of choice Alternative Tapeworms

Diphyllobothorium latum (fish), Taenia saginata (beef), Taenia solium (pork), Dipylidium canium (dog)

Praziquantel Oxamniquine

Ivermectin Thiabendazole

60 mg/kg/d in 3 doses x 1 d 20 mg/kg/d in 2 doses x 1 d

Drug(s) of choice

Praziquantel

5-10 mg/kg once

5-10 mg/kg once

Alternative

Niclosamide

2 g once

50 mg/kg once

Hymenolepis nana (dwarf)

Drug(s) of choice

Praziquantel

25 mg/kg once

25 mg/kg once

Trichostrongylus sp

Drug(s) of choice

Pyrantel pamoate

11 mg/kg once (max 1 g)

11 mg/kg once (max 1 g)

Alternative

Mebendazole

100 mg once

100 mg once

Or

Albendazole

400 mg once

400 mg once

Trichuris trichiura (Trichuriasis, whipworm)

Drug(s) of choice

Mebendazole

100 mg bid x3d or 500 mg once

100 mg bid x 3 d or 500 mg once

Alternative

Albendazole

400 mg x 3 d

400 mg x 3 d

Adapted from The Medical Letter on Drugs and Therapeutics, 2002; Gilbert et al, 2003; Goldsmith, 2003. bid = twice daily; max = maximum.

TABLE 52-3. Use of Antiparasitic Drugs in Children and Pregnant Women

Drug

Toxicity in Pregnancy Pregnancy

FDA Category Breastfeeding

Infants

Comments

Albendazole

Teratogenicity in lab animals when given at

C

Controversial

Very little data for

Recommended that pregnancy be delayed

high doses

infants < 12 months

until 1 month after therapy stopped

Bithionol

Safety not established but not recommended

C

Caution

No data

Fumagillin

Safety not established but not recommended

?

Best not to use

No data

Furazolidone

Safety not established but not recommended

C

Unknown but not

Contraindicated

In 132 reports of exposure, no

recommended

in infants

association with malformation

< 1 month

found. Theoretical risk of

hemolytic anemia in newborn.

lodoquinol

Safety not established but not recommended

C

Unknown but not

recommended

Ivermectin

Animal data show risk of teratogenicity

C

Caution

In 203 reports, exposure to ivermectin (85%

during 1st trimester) found no association

with congenital malformations

Mebendazole

Embryotoxic and teratogenic in lab animals

C

Little data but

Very little data

In a prospective study of 192 pregnant

when given at high doses

considered to be

for infants

women using 1 to 3 days of 100 mg dose,

"safe" due to poor

< 12 months

71% in 1st trimester, found mebendazole

absorption from

does not pose a risk; 2nd study of 64

the gastrointestinal

first trimester exposures showed no

tract.

significant teratogenic risk

Metronidazole

Carcinogen in rodents but studies demonstrate

B

Controversial as

No contraindication

The American Academy of Pediatrics

can be used in pregnancy except some

exposure may be

has classified metronidazole as a drug

caution in first trimester

high. With high

"for which the effect on nursing infants

doses consider

is unknown but may be of concern."

expressing and

Discontinue breastfeeding for 12 to

discarding milk

24 h to allow excretion of drug.

Niclosamide

Animal data show no risk

B

No data

Children < 2 years

No human data available

Oxamniquine

Mutagenic and embryotoxic effects in animal

C

Recommend no

unknown

No reports of abnormailites in humans

studies at 10 times human dose

breastfeeding at least

4 hours postdose

Paromomycin

Poorly absorbed, therefore thought to be safe

C

Probably safe

No contraindication

Limited information is available

regarding the teratogenic potential of

paromomycin. Following oral

administration, minimal systemic

absorption occurs, which therefore

minimizes any potential teratogenic

effect (Briggs et al, 1998). Paromoycin

has been recommended for the

treatment of infections with Giardia

lamblia and Entamoeba histolytica and

tapeworm infestations during pregnancy

(D'Alauro et al, 1985).

Praziquantal

Animal data show no teratogenic risk

B

Probably safe

Safety in children

WHO informal consultation

< 2 years not well

2002 concludes that likely to be

established

safe during pregancny and lactation

Pyrantel pamoate Animal data shows no teratogenic risk

C

Controversial

Use with caution in

No human data available

children < 2 years

Quinacrine

Animal data show no risk of teratogenicity

C

No data

No contraindication

no human data

Thiabendazole

Teratogenic in some animal species

C

No data

Safety in children < 15

Case reports in humans show

kg not established

no fetal adverse effects.

Tinidazole

Safety not established

Unknown but not

Unknown but not

recommended

recommended

Trimethoprim-

sulfamethoxazole May interfere with folic acid metabolism

C

Contraindicated

Contraindicated in

infants < 1 month and infants with hyper-bilirubinaemia and G6PD deficiency.

Adapted from Savioli et al, 2003;Briggs et al (ed), 2001

FDA = Food and Drug Administration; WHO = World Health Organization.

TABLE 52-4. Common Adverse Effects of Antiparasitic Drugs

Generic Name

Trade Name

Common

Serious

Albendazole

Albenza

Headache, nausea, vomiting, abdominal pain

Rare: acute renal failure, blood dyscrasias, elevated LFTs, leukopenia,alopecia

Bithionol

Bitin

Photosensitivity, vomiting, diarrhea, abdominal pain, urticaria

Fumagillin

Thrombocytopenia, neutropenia, mild GI symptoms

Furazolidone

Furoxone

Common: GI symptoms, yellow to brown discoloration of urine;occassional: fever, headache, rash, disulfiram-like reaction with alcohol, mild hemolysis in G6PD-deficient persons

Iodoquinol

Yodoxin

Nausea, vomiting, diarrhea, cramps, acne, urticaria, pruritus, fever, headache

Rare: optic neuritis, neuropathy with long-term use

Ivermectin

Stromectol

Occasional: mild headache, pruritus, leukopenia, transient tachycardia

Rare: Mazotti reaction (hypotension, fever, pruritis, bone and joint pain)

Mebendazole

Vermox

Headache, nausea, vomiting, abdominal pain, diarrhea, constipation

Rare: hepatitis, seizures

Metronidazole

Flagyl

Nausea, vomiting, headache, metallic taste;disulfiram-like reaction in alcohol users, vaginitis,candidal overgrowth

Rare:leukopenia, thrombocytopenia, ototoxicity

Niclosamide

Yomesan; Niclocide

Occasional: nausea, vomiting, anorexia, abdominal pain, diarrhea

Oxamniquine

Vansil

Occassional:dizziness, drowsiness, headache, febrile reaction, urine color change, EEG and EKG changes, hallucination

Seizure

Paromomycin

Humatin

Nausea, vomiting, epigastric burning pain, abdominal cramps, diarrhea

Praziquantel

Biltricide

Frequent:headache, malaise, dizziness; occasional: sedation, GI intolerance, abdominal pain,fever, sweating, fatigue

Pyrantel pamoate

Antiminth; Reese's pinworm med

Occasional: nausea, vomiting, abdominal discomfort

Quinacrine

Atabrine

Frequent: bitter taste. GI symptoms, headache, dizziness. occasional: toxic psychosis,insomina, blood dyscrasias, harmless yellowing of skin, exfoliative dermatitis. Contraindicated in persons with psychosis or psoriasis.

Rare: toxic psychosis, exfoliative dermatitis

Thiabendazole

Mintezol

Dizziness, drowsiness, headache, febrile reaction, urine color change

Tinidazole

Fasigyn

Mild GI symptoms; headache, vertigo less common

Triclabendazole

Egaten

Dizziness, headache, abdominal pain; less common cough, fever

Trimethoprim

Septra, Bactrim,

Anorexia, nausea, vomiting, rash, urticaria

Rare: allergic reaction, fulminant hepatic necrosis,

sulfamethoxazole

Sulfatrim

blood dyscrasias

EEG = electroencephalogram; EKG = electrocardiogram; GI = gastrointestinal.

EEG = electroencephalogram; EKG = electrocardiogram; GI = gastrointestinal.

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