Treatment of cutaneous larva migrans

Abstract

Dear Editors,

Among travel-associated skin infections, cutaneous larva migrans (cLM) is the most common parasitic disease.^1-3 It is caused by hookworms such as Ancylostoma braziliense, Ancylostoma caninum, and Uncinaria stenocephala that reside in the intestines of cats and dogs.⁴ As the larvae lack certain zinc-dependent metalloproteases for penetration beyond the skin, humans are aberrant hosts. CLM infestations are self-limiting after 1 to 3 months with the death and resorption of the larva. However, antihelminthic treatment is recommended because of persistent pruritus, mental stress due to parasitic infestation and risk of superinfection. There are few studies on the treatment. In fact, most recommendations are based on retrospective evaluations and case reports. According to the German S1-guideline,⁴ a single dose of oral ivermectin 200 µg per kg body weight (BW) is the treatment of choice. Alternatively, oral albendazole 800 mg per day for 3 days or topical albendazole 10% three times per day for 7–10 days is recommended. However, studies addressing such topical treatment options are lacking.

We herein present a retrospective study on cLM infestations in travelers returning to Germany. Data were collected in dermatology and tropical medicine departments of 20 German universities between 2000–2011³ and based on the clinical documentation in the patient files. Alongside patient, demographic, travel, and clinical information, our analysis also incorporated data on therapeutic approaches and responses.

A total of 246 cases of cLM were identified, with 140 patients (57.3%) being female. The highest prevalence occurred in the age group from 20–30 years. CLM was mainly diagnosed in travelers returning from Thailand (27%), Brazil (12%), Mexico (8%), and Jamaica (6%) (Figure 1). In 13 cases (6%), cLM was acquired in countries in Continental Europe (Figure 1). Three patients reported no travel history. The main risk factor was walking barefoot or unclothed exposure to sand in 81.5% (n = 75/92). The foot (57%, n = 172/303 from 240 cases) and the trunk (22%) were the most frequently affected sites. The main symptom was pruritus, followed by pain, in 85.6% (n = 149/174) and 12.1% (n = 21/174) of cases, respectively. In most cases, diagnosis was made based on the clinical symptoms only (72.3%, 185/256), followed by laboratory analyses (20.7%), histology (6.2%), and dermatoscopy (0.8%). Complications occurred in 11.8% with superinfection being the main complication in 70%.

Data on therapeutic approaches were collected in 233 cases (n = 378 from 233 cases, multiple entries allowed). Most cases were treated with systemic (n = 127) or local (n = 125) antihelminthica. Other additional topical treatments included antiseptics (n = 21), antibiotics (n = 20), antifungals (n = 13), as well as topical glucocorticoids (n = 22) and cryotherapy (n = 17).

Among antihelminthic therapies, topical and oral agents were prescribed with nearly equal frequency as first-line treatments, in 110 and 105 out of 224 cases, respectively. Topical and systemic therapy was concomitantly started in nine cases. In 26 cases, systemic therapy and in eleven cases, a topical therapy was subsequently indicated. Oral antihelminthica prescribed were ivermectin (54.9%, n = 79/144), albendazole (33.3%, n = 48/144), and mebendazole (11.8%, n = 17/144), while for topical therapy thiabendazole was used in 95.4% (n = 124/130). Both oral ivermectin and albendazole had cure rates of >90% (Table 1). Topical thiabendazole showed a cure rate of 89.6%, systemic mebendazole one of 50%. The cure rate of oral mebendazole was significantly lower than that of oral ivermectin, albendazole, and topical thiabendazole (p = 0.0004, p = 0.0004, and p < 0.0001, respectively, calculated using two-tailed chi-square tests) (Table 1). One adverse event was reported (urticaria after oral albendazole).

In sum, our study provides data on a large cohort of 246 returning travelers with cLM. Our findings on patient, demographic, travel, and clinical data are in line with previous studies.^4-6 Our study has limitations given its retrospective design and the investigation of a spontaneously resolving disease. Nevertheless, we provide data on therapeutic responses of distinct topical/systemic antihelminthica prescribed in an era before the current guideline was published. Among the currently recommended systemic antihelminthica, ivermectin and albendazole resulted in high cure rates similar to previous studies.⁴ Oral mebendazole and cryotherapy are explicitly not recommended due to poor efficacy which is consistent with our findings.

Particularly in cases where systemic treatment is not possible or desired, topical therapy becomes more important. Thiabendazole, one of the most effective therapies in our study, has been unavailable for years. Albendazole, the currently recommended topical agent, was given only in one patient in our study showing a complete response. Topical ivermectin, approved for the treatment of rosacea in Germany since 2015, was successfully used in two cases in our study. This is in line with several more recent case reports on the effective and well-tolerated therapy of cLM with topical ivermectin.^7-10 Despite a potential bias (often only successfully treated cases are published), these observations suggest that topical ivermectin may not be inferior to systemic treatment and should encourage larger controlled studies to evaluate the efficacy of topical ivermectin in cLM.

None.