Key points
- Gnathostoma infections are treatable with medication.
- Treatment is safe and effective.
- Consider safety precautions of medications in different populations.
Treatment options
For cutaneous symptoms of Gnathostoma infection, both albendazole and ivermectin have been shown to result in cure in several trials that were too small to firmly establish efficacy and safety of treatment.
Reported cure rates at 6 months after treatment with albendazole are >90% and after treatment with ivermectin range from 76–95.2%. Albendazole may cause outward migration of larvae. Ivermectin may cause a temporary increase of cutaneous symptoms. Two small studies in which patients were followed up for 1 year or longer found cure rates after treatment with albendazole decreased over time. Relapse is not uncommon, however, with either treatment and has been shown to occur up to 26 months after initial therapy. Monitoring for symptom recurrence is needed for all patients regardless of treatment regimen. Relapse does not necessarily require treatment with a different medication, though data on this issue also are limited.
Two different regimens of albendazole (400 mg daily for 21 days and 400 mg twice daily for 21 days) and two different regimens of ivermectin (200 mcg/kg once daily for 1 day and 200 mcg/kg once daily for 2 days) have been studied. Data are insufficient to determine which regimen is the most effective, so it would probably be prudent to use the higher dose regimen of either medication until better data are available.
Whether to treat ocular and central nervous system (CNS) Gnathostoma infection remains controversial, particularly as there are no published studies of the efficacy of albendazole or ivermectin. As albendazole may cause larvae to migrate and ivermectin may cause a disease flare, there is concern that treatment with antihelminthics could worsen a patient's neurologic status and possibly increase the risk for death or permanent neurologic deficit. There has been only one observational study of corticosteroids in patients presenting with probable Gnathostoma infection. No benefit of corticosteroids was demonstrated, possibly because it is thought that much of the damage to the CNS is caused by mechanical destruction of tissue.
At this time it is not possible to give recommendations for the treatment of CNS or ocular disease other than to provide supportive care. As gnathostomiasis has been shown to cause intracranial hemorrhage, patients with neurologic disease should be carefully monitored and plans for prompt intervention should be put into place.
Care precautions
Treatment in Pregnancy
Albendazole is a pregnancy category C drug. There are limited data on the use of albendazole in pregnant women. The available evidence suggests no difference in congenital abnormalities in the children of women accidentally treated with albendazole during mass drug administration (MDA) campaigns compared with those who were not. In MDA campaigns for which the World Health Organization (WHO) has determined that the benefits of treatment outweigh the risks, WHO allows use of albendazole in the 2nd and 3rd trimesters of pregnancy. However, healthcare providers should balance the risks of treatment for the fetus with the risks of disease progression in the woman in the absence of treatment.
Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) plus there are no controlled studies in women, or studies in women and animals are not available. Prescribe albendazole only if the potential benefits to the woman justify the potential risks to the fetus.
Treatment during lactation
Albendazole is minimally excreted in human milk. WHO has concluded that a single oral dose of albendazole can be given to lactating women.
Treatment in pediatric patients
The safety of albendazole in children less than 6 years old is not certain. Studies of the use of albendazole in children as young as one year old suggest that it is safe. According to WHO guidelines for MDA campaigns, children as young as one year of age (able to safely swallow tablets) can take albendazole. These campaigns have treated many children under six years old with albendazole, albeit at a reduced dose.
Treatment in Pregnancy
Ivermectin is a pregnancy category C drug. Data on the use of ivermectin in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated during mass drug administration (MDA) campaigns with ivermectin compared with those who were not. The World Health Organization (WHO) excludes pregnant women from MDA campaigns that use ivermectin. In a pregnant woman infected with a soil-transmitted helminth, balance the risks of treatment for the fetus with the risks of disease progression in the woman in the absence of treatment.
Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) plus there are no controlled studies in women, or studies in women and animals are not available. Prescribe ivermectin only if the potential benefits in the woman justify the potential risks to the fetus.
Treatment during lactation
Ivermectin is excreted in low concentrations in human milk. Treat breastfeeding women with ivermectin only when the risks of disease progression in the untreated mother outweigh the risks to the infant.
Treatment in pediatric patients
The safe use of ivermectin in children weighing less than 15 kg (33 lbs) is unclear. According to the WHO guidelines for MDA campaigns, ivermectin can safely treat children at least 90 cm (35 in) tall. The WHO growth standard curves show that 50% of boys reach this height by age 28 months and 50% of girls by age 30 months. Some MDA campaigns use ivermectin to treat younger children who are able to swallow tablets safely, albeit at a reduced dose.