Control of Tungiasis through Intermittent Application of a Plant-Based Repellent: An Intervention Study in a Resource-Poor Community in Brazil

Tungiasis is a parasitic skin disease caused by the female sand flea Tunga penetrans. The disease is frequent in resource-poor communities in South America and sub-Saharan Africa and affects the poorest of the poor. Sand flea disease is associated with a considerable morbidity and may lead to tetanus in non-vaccinated individuals. The degree of morbidity depends on the intensity of infestation, i.e., the number of embedded sand fleas a person has. Since tungiasis is a zoonosis involving a host of animal reservoirs, and because an effective treatment is not at hand, in resource-poor settings elimination is not feasible. Preventing morbidity to develop is therefore the only means to protect exposed individuals from sand flea disease. Similar to other arthropods, sand fleas can be repelled before they penetrate into the skin. In this study we show that the intermittent application of a plant-based repellent, of which the major component is coconut oil, reduces the intensity of infestation dramatically during the whole transmission season and prevents tungiasis-associated morbidity from developing. The prevention can be performed at the household level by the affected individuals themselves with minimal input from the health sector

Morbidity and Prevention of Tungiasis in a Shantytown in Northeast Brazil

GesamtdissertationDie Tungiasis ist eine Ektoparasitose, die in zahlreichen Ländern Südamerikas, der Karibik und Afrikas endemisch ist. Die Prävalenz kann 50% und mehr in der generellen Bevölkerung betragen. Sie ist mit erheblicher Morbidität assoziiert. Präventivmaßnahmen wurden bislang noch nie systematisch eingesetzt. In zwei Armensiedlungen der Stadt Fortaleza, Nordost-Brasilien, wurden 79 Personen rekrutiert, die mindestens zehn penetrierte Sandflöhe aufwiesen, und zwei Kohorten zugewiesen. Vor Beginn der Intervention wurden die Patienten über einen Zeitraum von 25 Tagen zweimal wöchentlich untersucht, um die Ausgangswerte zu bestimmen. Eine Intervention mit dem pflanzlichen Repellent Zanzarin® erfolgte in einem Cross-over-Design. Vor, während und nach der Intervention wurden folgende Zielvariablen erfasst: Infestationsrate, Infestationsintensität, Anteil der viablen Läsionen und klinische Pathologie, letztere mit Hilfe von zwei semiquantitativen Schweregradindices. Anhand von im Studiengebiet ausgesetzten Wistar-Ratten wurden Änderungen in der Transmissionsdynamik erfasst. Während der Intervention sank die Infestationsrate um 90% von 2,0 auf 0,2 neue Läsionen pro Individuum und Tag (p<0,001) und die Infestationsintensität um 87% von 26,5 auf 3 Läsionen pro Individuum (p<0,001). Der Schweregradindex für akute Tungiasis betrug nach Intervention 0,0 Punkte (Ausgangswert: 5,8; p<0,001). Der Schweregradindex für chronische Pathologie änderte sich durch die vierwöchige Unterbrechung der Transmission nicht. Nageldeformationen bestanden unverändert bei 98% der Patienten, wohingegen die Zeichen akuter Entzündung stark zurückgegangen waren: Ödem und Erythem von 90% auf 11%, Superinfektion von 35% auf 6%. Eine schmerzbedingte Einschränkung des Gehens bestand vor Intervention bei 15, danach noch bei drei Patienten. Eine multivariate Analyse zeigte einen hochgradig signifikanten Effekt der Intervention auf die Änderung der Zielvariablen. Die Studie belegt, dass durch den Einsatz eines Repellents die Infestationsrate, die Infestationsintensität und die Tungiasis-assoziierte Morbidität im Endemiegebiet drastisch reduziert werden kann.Tungiasis is a tropical ectoparasitosis caused by infestation with the sandflea Tunga Pentrans. The disease is endemic in many South American countries, the Caribbean and subsaharian Africa. The prevalence can reach 50% and more in the general population. It is associated with severe morbidity. Preventive measures have never been applied systematically. In two shantytowns in Fortaleza, northeast Brazil, 79 persons with at least ten embedded sandfleas were identified and two cohorts were formed. Every study member was examined twice a week. After 25 days of mere observation, an intervention with the plant-based repellent Zanzarin® was carried out in a cross-over-design. Cohort A received the repellent during four weeks while cohort B served as untreated control. After a wash-out-phase of ten days, the repellent was applied to cohort B, while cohort A served as untreated control. The following outcome-measures were assessed throughout the study: infestation-rate, intensity of infestation, ratio of viable lesions and clinical pathology. The latest was documented using two semiquantitative severity scores. Sentinel rats were used to assess local transmission dynamics. During intervention the infestation rate fell by 90% from 2,0 to 0,2 new lesions per individual and day (p<0,001) and the intensity of infestation by 87% from 26,5 to 3 lesions per individual (p<0,001). The severity score for acute tungiasis took the value of 0,0 points (before intervention: 5,8; p<0,001). The severity score for chronic tungiasis did not change after interrupting the transmission for four weeks. Deformation of toenails remained present in 98% of the patients, while signs of acute inflammation regressed from 90% to 11% and bacterial superinfection from 35% to 6%. Difficulties in walking due to pain was found in 15 patients before intervention and only persisted in three patients after intervention. A multivariate analysis showed a highly significant effect of the intervention on the outcome measures. The study showed, that the use of Zanzarin® remarkably reduced the infestation-rate, the intensity of infestation and the tungiasis-associated morbidity

High exposure to Tunga penetrans (Linnaeus, 1758) correlates with intensity of infestation

Tungiasis is a parasitic skin disease widespread in resource-poor urban and rural communities in Brazil. Inhabitants of an urban slum in Northeast Brazil were examined for the presence of tungiasis lesions and followed-up twice a week for a period of three weeks. Each time the number, stages, and topographic localization of lesions were recorded on a documentation sheet. The infestation rate (number of newly embedded sand fleas per individual and day) remained stable during the observation period. The infestation rate was significantly related to the intensity of infestation (total number of lesions present) (rho = 0.70, p < 0.0001) and the proportion of viable lesions (rho = 0.28, p < 0.0001). The results indicate that in an endemic area the infestation intensity and the proportion of viable lesions can be used as a proxy to assess the exposure of individuals at risk for tungiasis. Persistently high infestation rates during the transmission season favour the use of prevention measures against invading sand fleas (such as a repellent) rather than a drug to kill already embedded parasites