Conceived and designed the experiments: JH HF. Performed the experiments: JB LA MS. Analyzed the data: JB LA MS HF. Contributed reagents/materials/analysis tools: JB JH LA JDK HF. Wrote the paper: JB HF.
The authors have declared that no competing interests exist.
Tungiasis, an ectoparasitosis caused by the female sand flea
We assessed the effectiveness of the intermittent application of the plant-based repellent Zanzarin to reduce infestation intensity and tungiasis-associated morbidity in a resource-poor community in Brazil, characterized by a very high attack rate. The study population was randomized into three cohorts. Initially, during a period of four weeks, the repellent was applied twice daily to the feet of all cohort members. This reduced the number of embedded sandfleas to 0 in 98% of the participants. Thereafter members of cohort A applied the repellent every second week twice daily for one week, members of cohort B every fourth week for one week, and members of cohort C served as controls. Infestation intensity and tungiasis-associated morbidity were monitored during five months. The intermittent application of Zanzarin for one week every second week significantly reduced infestation intensity from a median 4 lesions (IQR 1–9) during the whole transmission season. In contrast, in cohort B (application of the repellent every fourth week) the infestation intensity remained twice as high (median 8 lesions, IQR 9–16; p = 0.0035), and in the control cohort C 3.5 times as high (median 14 lesions; IQR 7–26; p = 0.004 during the transmission season). Tungiasis-related acute pathology remained very low in cohort A (median severity score 2; IQR 1–4) as compared to cohort B (median severity score 5; IQR 3–7; p<0.001), and control cohort C (median severity score 6.5; IQR 4–8; p<0.001).
Our study shows that in a setting with intense transmission, tungiasis-associated morbidity can be minimized through the intermittent application of a plant-based repellent.
Tungiasis is a parasitic skin disease caused by the female sand flea
Tungiasis is a common, but neglected health problem in economically disadvantaged communities in tropical and subtropical countries
The ectoparasitosis mainly affects marginalized populations in urban squatter settlements, in villages in the hinterland, and in traditional fishing communities along the littoral
Since it is virtually impossible to eliminate tungiasis as long as the precarious living conditions characteristic for impoverished communities exist, morbidity control remains the only option. There is no effective chemotherapy available to kill embedded sand fleas. Parasites need to be extracted surgically with a sterile instrument. However, this requires a skilled hand and good eyesight. In resource-poor communities surgical removal is inconsistently performed and causes more harm than good if not done correctly
The study was conducted in five neighborhoods (Luxou, Morro das Sandra's, Placas, Morra da Vitória and Novo Rumo) of the shantytown Vincente Prinzón, a typical conglomeration of urban squatter settlements (favela) in Fortaleza, Northeast Brazil. The area is characterized by intense transmission of
A randomized controlled trial was carried out in the five neighborhoods between June and December 2005. This period (dry season) coincides with the high transmission season of
Individuals with tungiasis were identified with the assistance of community health workers. They were included in the study provided they had at least 5 embedded sand fleas in stage 1 to 4 of the Fortaleza Classification, or a similar number of sand flea lesions manipulated with a perforating instrument
The intensity of infestation and the degree of tungiasis-associated morbidity was assessed as described previously
During a period of five months members of Cohort A applied the repellent every second week twice daily for one week, and members of Cohort B every fourth week twice daily for one week. Cohort C served as control group and did not receive any protection.
During the intervention periods Zanzarin was applied by trained community health workers on the skin of the feet (up to the ankle) including the interdigital areas. The average volume applied was 3 ml per person and day (Calculation based on the number of 100 ml bottles used per day, divided by the number of treated individuals). Prophylaxis was performed in the morning between 6 and 8 a.m., and in the evening between 6 and 8 p.m. The exact time of application was recorded for each study participant. The application of the repellent was regularly checked by random visits to the households of the study participants by one of the investigators (J.B.). In addition, at each examination the participants were asked whether the repellent had been applied regularly. This ensured that the repellent was applied exactly as defined in the study protocol, not spilled, given away for money, or stolen. The participants were asked not to wash their feet for at least two hours after application of the repellent. However, they were allowed to take a shower whenever they wanted.
Unexpectedly, staff members were assaulted during the second part of the study. For safety reasons we decided to interrupt the regular follow-ups at calendar week 45. Monitoring was resumed at calendar week 47. Nonetheless, the application of the repellent was continued during this period.
The repellent used was Zanzarin, a lotion based on coconut oil (
Since tungiasis can occur at any area of the body
– Flea in
– A dark and itching spot in the epidermis with a diameter of 1 to 2 mm, with or without local pain and itching (early lesion, stage II)
– Lesions presenting as a white halo with a diameter of 3 to 10 mm with a central black dot (mature egg producing flea, stage III)
– A brownish–black circular crust with or without surrounding necrosis of the epidermis (dead parasite, stage IV).
During monitoring the number of viable (stage I to III), and dead (stage IV) sand fleas, and the total number of sand flea lesions were determined. Clinical pathology was documented every four weeks. Lesions manipulated by the patient (such as partially or totally eliminated fleas leaving a characteristic crater-like sore in the skin), and suppurative lesions caused by the use of non-sterile perforating instruments, such as needles, and thorns, were documented as well. The exact topographic localization of each lesion, its stage, and appearance were documented on a visual record sheet.
Clinical pathology was assessed in a semi-quantitative manner using a previously elaborated severity score for acute tungiasis (SSAT), and a severity score for chronic tungiasis (SSCT)
The SSCT ranges from 0 to 33 points and comprises the presence of nail deformation, nail loss, brilliant skin (an indicator of chronic edema), deformation of toes; hypertrophic nail rim, and perilesional desquamation; the latter two characteristics are indicators of repeated tungiasis experienced in the past
Households were randomized using a permuted block design (block size six, allocation ratio 1∶1). An investigator not involved in the follow-up visits created the randomization code. A computer generated random list was used.
All data were entered into an Epi-Info database (CDC, Atlanta, Ver. 6.04d) and checked for errors, which might have occurred during data entry. The database was exported into SigmaStat and SigmaPlot (Systat Software GmbH, San José, Version 2007). The main outcome measure was the intensity of infestation, i.e. the number of sand flea lesions present at the time of examination. Secondary outcome measures were the severity score of acute, and the severity score of chronic pathology. As the variables assessed were not normally distributed and variances varied considerably, the median and the interquartile ranges were used to indicate the average and dispersion of data. To compare results between the cohorts, the Wilcoxon Signed Rank Test was used; for correlation analysis, Spearman’s Rho was calculated. In order to detect a difference of 50% in infestation intensity between cohorts A and C, a sample size of 42 individuals for each cohort was calculated (level of significance 95%, power of the test 80%). In order to compensate for drop-outs it was decided to recruit 140 individuals to the study.
The study was approved by the Ethical Committee of the Federal University of Ceará, Brazil (43/05, SINESP) and was registered at Controlled-trials.com (ISRCTN16910507). Informed written consent was obtained from all participants and in the case of minors from the parents or legal guardians. At the end of the study, all participants as well as their household members were carefully examined for the presence of embedded sand fleas. Individuals with tungiasis were treated with Zanzarin twice daily for a period of three weeks, a measure effectively reducing the number of embedded sand fleas and the degree of clinical pathology to almost zero
The flow diagram of the study is depicted in
Variable | Cohort A(n = 45) | Cohort B(n = 34) | Cohort C(n = 43) |
Age (median/range) | 8 (4–12) | 9 (5–16) | 7 (5–10) |
Sex ratio (females/males) | 1.6 | 1 | 1.1 |
Total number of embedded sand fleas (median/IQR) | 18 (9–31) | 16 (12–34) | 17 (10–25) |
Viable lesions (median/IQR) | 4 (2–14) | 6 (3–12) | 6 (4–10) |
Total number lesions (median/IQR) | 0 (0–2) | 0 (0–1) | 0 (0–1) |
Viable lesions (median/IQR) | 0 (0–1) | 0 (0–1) | 0 (0–1) |
After the initial intervention (application of Zanzarin twice daily in all cohort members during a period of four weeks) the infestation intensity decreased from a median of 17 (IQR 11–30), to a median of 0 (IQR: 0–1; p<0.001). Only two participants showed more than one embedded sand flea. This was paralleled by a drastic reduction of the SSAT: median before intervention 8.5 (IQR: 6–11), versus 0 (IQR: 0–1; p<0.001). The SSCT score was also reduced: median before intervention 12 (IQR: 9–15), versus 7 (IQR: 5–10; p<0.001). No adverse reactions to the repellent were reported.
The data indicate the number of median lesions per individual. No follow-ups were carried out between calendar weeks 45–47 (see
In contrast, in the control cohort the intensity of infestation almost constantly increased during the transmission season, and reached a maximum of 19 sand flea lesions (IQR 10–34) at calendar week 50. Intensity of infestation between calendar week 31 and 52 was significantly higher in cohort C, as compared to cohort A (p = 0.004), and between cohort C and cohort B (p = 0.04). During this period intensity of infestation was also significantly higher in cohort B, as compared to cohort A (p = 0.03) (
As seen in
No follow-ups were carried out between calendar weeks 45–47 (see
The proportion of manipulated lesions during the observation period is depicted in
No observations were carried out between calendar weeks 45–47 (see
In cohort B and C the number of manipulated lesions correlated with the total number of lesions during this period: Cohort B rho = 0.67; p = 0.002, cohort C rho = 0.9, p<0.001. In cohort A no such correlation was observed.
The degree of clinical pathology was measured by the severity score for acute tungiasis (SSAT), and the severity score for chronic tungiasis (SSCT).
During the first round of application of Zanzarin (twice daily for 4 weeks) the SSAT decreased in an identical manner in the three cohorts. For sake of clarity the data points of cohort B and C were shifted +/−0.1 calendar weeks on the x-axis, although the assessment of the SSAT was done simultaneously in the three cohorts.
The pattern of the SSCT is shown in
During the first round of application of Zanzarin (twice daily for 4 weeks) the SSCT decreased in an identical manner in the three cohorts. For sake of clarity the data points of cohort B and C were shifted +/−0.1 calendar weeks on the x-axis, although the assessment of the SSCT was done simultaneously in the three cohorts.
In this study we investigated, whether the intermittent application of Zanzarin keeps the infestation rate at an acceptable low level, and prevents severe clinical pathology to develop during the transmission season, which coincides with the dry season of the year in most endemic areas
Since infestation rate and infestation intensity are closely related
If sand fleas are effectively repelled, only a few new parasites will penetrate per unit of time. This is reflected by a low number of viable lesions (stage I to III of the Fortaleza classification). In fact, the median number of viable sand flea lesions per individual showed different patterns in each of the cohorts. Whereas in cohort A the median number of viable sand fleas was 1, in cohort B – and even more so in cohort C - the number of viable sand flea lesions increased in a step-wise manner during the intermittent application of the repellent (
The irritation and pain caused by embedded sand fleas is the reason why affected individuals try to get rid of the parasites with sharp instruments. Supposedly, the more sand fleas penetrate and embed per unit of time, the higher is the proportion of lesions manipulated with instruments. Hence, an effective repellent will be reflected by a low percentage of manipulated lesions. Indeed, the effectiveness of Zanzarin to prevent a high intensity of infestation to build up, is mirrored by the pattern of manipulated lesions in the three cohorts. In cohort A, manipulated lesions were completely absent until almost the end of the transmission season, whereas in cohort C the number of manipulated lesions started to increase almost constantly after the end of the initial intervention, and with a certain delay also in cohort B (
As expected, the almost complete interruption of transmission in cohort A prevented severe pathology to develop. This is mirrored by a decrease between 64% and 88% of the SSAT score during the transmission season, as compared to the degree of acute pathology at admission (
The interval application of Zanzarin was less effective in reducing the presence of chronic pathology (
Based on an average of 3 ml of Zanzarin applied per individual per day, a member of Cohort A needed a total of 210 ml of the repellent for the whole transmission season. If Zanzarin is bought in bulk quantity, 10–12 US$ would be sufficient to protect one person against the debilitating sequels of tungiasis during the whole transmission season. Since children and the elderly are particularly affected by severe manifestations of sand flea disease
CONSORT checklist.
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Clinical trial protocol.
(0.19 MB DOC)
Compounds of Zanzarin.
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We are grateful to the Associação dos Moradores do Sandra's for supporting the study, and to Valéria Santos, Marilene da Silva Paulo, Marvel, Jose Maria Lourenco, and Maria de Fátima Cavalcante for skillful assistance. We cordially thank the community members Maria Rosima Mendonca da Silva, Maria José Vieira, Daniele Mendonca da Silva, Francisco Jose Vieira, and Aurilene da Silva Paulo, without whose help this study would not have been possible. The data are part of a medical thesis by JB.