Strongyloidiasis
Strongyloidiasis is a gastrointestinal helminthic infection that occurs in most tropical and subtropical regions of the world (see Map). Most patients will be asymptomatic but some can experience vague gastrointestinal symptoms (usually upper GI symptoms) or cutaneous manifestations such as urticaria or pruritus. It can also cause eosinophilia.
However, in patients who become immunosuppressed, a potentially deadly hyperinfection syndrome can happen where the strongyloides larvae disseminate throughout the host’s body. This can happen even with a very short immunosuppression period such as a course of corticosteroids for 1 or 2 weeks. Strongyloidiasis can last for multiple decades in a single host because of the parasite’s special autoinfection life cycle. This is why it is very important to screen refugee patients and treat them adequately.
TREATMENT
In patients with a positive strongyloides serology, the treatment of choice is ivermectin:
| Ivermectin 200 mcg/kg/dose 2 single doses given on 2 consecutive days |
Ivermectin is available in 3 mg tablets.
While ivermectin used to be only available through the federal Special Access Programme, it has recently been approved by Health Canada and is covered by the Interim Federal Health Program since November 2018. It is however still not available in most regular pharmacies and physicians should contact their local pharmacies to inquire about its availability.
Albendazole (400 mg twice daily x 7 days) is an alternative treatment for strongyloidiasis, but it is currently only accessible through the Special Access Programme in Canada.
CONTRAINDICATIONS TO IVERMECTIN
Ivermectin is very safe and usually well tolerated, but there is one major contraindication: a concomitant loa loa infection.
Loiasis (also known as the “eye worm”) is a filarial helminthic infection that is endemic in many central African countries. While the infection in itself usually does not cause severe complications, if a patient with loiasis is treated with ivermectin, it can cause a significant inflammatory reaction leading to encephalitis. This is why any strongyloidiasis patient from a loa loa endemic country (see Map) should be tested for loiasis before being treated with ivermectin. Since testing for loiasis requires a special blood smear done at a specific time of the day, this should be done by an Infectious Diseases specialist.
In addition, ivermectin should not be used during pregnancy or lactation and in children <15 kg since safety has not been well established in these cases (The Medical Letter, 2013).
TEST-OF-CURE
Since anti-strongyloides antibodies titers usually fall a few months after treatment, it is possible to repeat the serology 6 months post-treatment to monitor the adequacy of treatment. However, because of the high cure rates of ivermectin in immunocompetent patients, we do not recommend to routinely perform a test-of-cure. We do however recommend a test-of-cure for patients who are or will be immunosuppressed.
In patients with persistent symptoms or eosinophilia following treatment (wait at least 6 months before repeating the CBC), a second course of ivermectin can be tried first before repeating the serology.
EQUIVOCAL SEROLOGY
In patients with an equivocal strongyloides serology, a repeat serology can be ordered. On the second serology, a positive or a second equivocal result warrants treatment. However, considering the simplicity of the treatment, in patients with an equivocal serology who are not from a loa loa endemic region, it is reasonable to offer ivermectin right away without repeating the serology.
>> Refer to the Centers for Disease Control and Prevention (CDC) website for more information on strongyloidiasis.