Successful Treatment of Severe Tungiasis in Pigs Using a Topical Aerosol Containing Chlorfenvinphos, Dichlorphos and Gentian Violet

Abstract

Background: In endemic communities, zoonotic tungiasis, a severe skin disease caused by penetrating female sand fleas, is a public health hazard causing significant human and animal morbidity. No validated drugs are currently available for treatment of animal tungiasis. Due to the reservoir in domestic animals, integrated management of human and animal tungiasis is required to avert its negative effects.

Methods and principal findings: A topical aerosol containing chlorfenvinphos 4.8%, dichlorphos 0.75% and gentian violet 0.145% licensed to treat tick infestations, myiasis and wound sepsis in animals in the study area, was tested for its potential tungicidal effects in a randomized controlled field trial against pig tungiasis in rural Uganda. Animals with at least one embedded flea were randomized in a treatment (n = 29) and a control (n = 26) group. One week after treatment, 58.6% of the treated pigs did not show any viable flea lesion whereas all control pigs had at least one viable lesion. After treatment the number of viable lesions (treated median = 0, overall range = 0-18 vs. control median = 11.5, range = 1-180) and the severity score for estimating acute pathology in pig tungiasis (treated median = 1, range = 0-3.5 vs. control median = 7, range = 0-25) were significantly lower in treated than in control pigs (p < 0.001). In the treatment group the median number of viable flea lesions decreased from 8.5 to 0 (p < 0.001). Similarly, the median acute severity score dropped from 6 to 1 (p < 0.001). Every pig in the treatment group showed a decrease in the number of viable fleas and tungiasis-associated acute morbidity while medians for both increased in the control group.

Conclusions: The study demonstrates that a topical treatment based on chlorfenvinphos, dichlorphos and gentian violet is highly effective against pig tungiasis. Due to its simplicity, the new approach can be used for the treatment of individual animals as well as in mass campaigns.

Fig 1

Left hind leg digits of a pig before (A) and after (B) treatment. This pig had 297 lesions before treatment (208 viable and 89 dead) of which 6 were ectopic on metacarpal and metatarsal skin. Only three viable lesions were detectable after treatment. Selected viable lesions are marked with black arrows while some dead lesions are marked with white arrows.

Fig 2

Digits of a pig in the control group at baseline (A) and after seven days (B). This pig had 29 lesions of which 21 were viable (black arrows) and eight were dead at baseline but one week later there were 17 viable lesions and more than 28 dead lesions many of which were mutilated (white arrows).

Fig 3

Number of viable lesions (A) and morbidity scores (B) in control and treatment groups of pigs at base line and 7 days treatment. Data belonging to the same animal in day 0 and day 7 are connected by a line. Medians are shown as blue lines.