Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil: I. Natural history of tungiasis in man

Fleas as parasites of the family Canidae

Historically, flea-borne diseases are among the most important medical diseases of humans. Plague and murine typhus are known for centuries while the last years brought some new flea-transmitted pathogens, like R. felis and Bartonella henselae. Dogs may play an essential or an accidental role in the natural transmission cycle of flea-borne pathogens. They support the growth of some of the pathogens or they serve as transport vehicles for infected fleas between their natural reservoirs and humans. More than 15 different flea species have been described in domestic dogs thus far. Several other species have been found to be associated with wild canids. Fleas found on dogs originate from rodents, birds, insectivores and from other Carnivora. Dogs therefore may serve as ideal bridging hosts for the introduction of flea-borne diseases from nature to home. In addition to their role as ectoparasites they cause nuisance for humans and animals and may be the cause for severe allergic reactions.

Tungiasis: a poorly documented tropical dermatosis

Tungiasis is the parasitic skin disease caused by the sand flea Tunga penetrans, also called the jigger flea, found in most intertropical countries. The contamination occurs when walking barefoot in the sand: adult females actively burrow the foot epidermis leading to self-limited lesions responsible for itching or pain. The diagnosis is made on clinical observation and history of travelling to an endemic country. The simple treatment is surgical extraction of the flea.

Four imported cases of tungiasis in Mallorca

Tungiasis is an endemic disease in many resource-poor communities some of which are in South America, which are visited frequently by Spanish travelers. Its diagnosis can be improved with the knowledge of the typical presentation and the correct management of its injuries. We report the first four cases identified of imported tungiasis in Mallorca. All four patients visited beaches in Brazil and presented the classical black lesions after their return. Two of the patients were diagnosed at primary care level and all were treated by dermatologists with surgical techniques. Dermoscopy was used for the initial approach to the injuries. Tungiasis can be suspected easily by examining carefully the black lesions and asking about previous travel. It can be treated readily by minor surgical techniques.

Occurrence of the off-host life stages of Tunga penetrans (Siphonaptera) in various environments in Brazil

To explore the local transmission dynamics of Tunga penetrans in brazil, 134 soil samples from various environments were collected in three different endemic regions of the country and checked for the presence of the flea's larvae, pupae and adults. the samples, which came from an urban slum in the north-east, a village of xavante indians in the central-west and a community of yanomami indians living in traditional longhouses (malocas) in the north, were categorized as indoor, outdoor or indoor-outdoor (the latter representing samples collected in the malocas). The proportion of samples found positive for T. penetrans was lowest in the slum (9.3%) and highest in the Yanomami village (32.0%; P=0.01). Soil samples collected below bedsteads or hammocks or from the indoor resting places of dogs were significantly more likely to be positive than the indoor samples collected at other sites (65.0% v. 35.0%; P=0.02). There was no evidence indicating that the presence of T. penetrans in a soil sample was markedly affected by soil temperature, air temperature or air humidity. As no life stages of T. penetrans were found in any outdoor sample, it seems likely that, in resource-poor settings in Brazil, most transmission of T. penetrans occurs indoors. Control measures against the off-host life stages of T. penetrans should therefore be targeted at particular indoor micro-environments.

Control of tungiasis through intermittent application of a plant-based repellent: an intervention study in a resource-poor community in Brazil

BACKGROUND

Tungiasis, an ectoparasitosis caused by the female sand flea Tunga penetrans, is an important health problem in many impoverished communities in the tropics. Sand flea disease is associated with a broad spectrum of clinical pathology and severe sequels are frequent. Treatment options are limited.

METHODOLOGY/PRINCIPAL FINDINGS

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).

CONCLUSIONS/SIGNIFICANCE

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.

An ectopic case of Tunga spp. infection in Peru

Tungiasis is a neglected ectoparasitism of impoverished areas in South America and sub-Saharan Africa. The sand flea Tunga spp. preferably infests the soles and the periungueal and interdigital regions of the feet. Ectopic tungiasis is rare, even in highly endemic areas. We describe a case of an indigenous patient in Peru who presented with a nodular lesion in the extensor aspect of the knee and whose biopsy was compatible with Tunga spp. This is the first documented case of knee tungiasis in an endemic country. The historical, clinical, histological, and current epidemiological aspects of tungiasis in Peru are discussed here.

A simple method for rapid community assessment of tungiasis

OBJECTIVE

To evaluate a rapid assessment method to estimate the overall prevalence of tungiasis and severity of disease in endemic communities.

METHODS

We analysed data from 10 population-based surveys on tungiasis, performed in five endemic communities in Brazil and Nigeria between 2001 and 2008. To assess the association between occurrence of tungiasis on six defined topographic areas of the feet and the true prevalence/prevalence of severe disease, linear regression analyses were performed. Estimated prevalences were calculated for each of the 10 surveys and compared to true prevalences. We then selected the most useful topographic localization to define a rapid assessment method, based on the strength of association and operational aspects.

RESULTS

In total, 7121 individuals of the five communities were examined. Prevalence of tungiasis varied between 21.1% and 54.4%. The presence of periungual lesions on the toes was identified as the most useful rapid assessment to estimate the prevalence of tungiasis (absolute errors: -4% to +3.6%; R(2 )=96%; P < 0.0001). Prevalence of severe tungiasis (>20 lesions) was also estimated by the method (absolute errors: -3.1% to +2.5%; R(2 )=76%; P = 0.001).

CONCLUSION

Prevalence of tungiasis and prevalence of severe disease can be reliably estimated in communities with distinct cultural and geographical characteristics, by applying a simple and rapid epidemiological method. This approach will help to detect high-risk communities and to monitor control measures aimed at the reduction of tungiasis.

Tunga penetrans as a traveler's disease

Tunga penetrans are ectoparasites distributed widely. The infestations are endemic in some areas. People both from and visiting this region are susceptible to these infestations.

Sand flea (Tunga spp.) infections in humans and domestic animals: state of the art

Tungiasis is a parasitic disease of humans and animals caused by fleas (Siphonaptera) belonging to the genus Tunga. Two species, Tunga penetrans (L.) and Tunga trimamillata, out of 10 described to date, are known to affect man or domestic animals; the other eight are exclusive to a few species of wild mammals. Tunga penetrans and T. trimamillata originated from Latin America, although the first species is also found in sub-Saharan Africa (between 20 degrees N and 25 degrees S). Hundreds of millions of people are at risk of infection in more than 70 nations, mostly in developing countries. The second species has been reported only in Ecuador and Peru. Males and non-fertilized females of Tunga are haematophagous ectoparasites; pregnant females penetrate the skin where, following dilatation of the abdomen, they increase enormously in size (neosomy) and cause inflammatory and ulcerative processes of varying severity. The importance of Tunga infection in humans concerns its frequent localization in the foot, which sometimes causes very serious difficulty in walking, thereby reducing the subject's ability to work and necessitating medical and surgical intervention. Tungiasis in domestic animals can be responsible for economic losses resulting from flea-induced lesions and secondary infections. Because tungiasis represents a serious problem for tropical public health and because of the recent description of a new species (Tunga trimamillata), it seems appropriate to review current knowledge of the morphology, molecular taxonomy, epidemiology, pathology, treatment and control of sand fleas of the genus Tunga.

Tungiasis in schoolchildren in Criciúma, Santa Catarina State, South Brazil

Tungiasis is a common parasitic skin disease in Brazil, caused by the flea Tunga penetrans. We conducted a cross-sectional study to evaluate the occurrence of infestation with T. penetrans in primary schoolchildren in Criciúma, Santa Catarina State (South Brazil). In total, 917 children (6-10 years) of 68 schools were included in the study (11% of target population). Physical examination was followed by residential visits of those infested, to assess housing conditions and to interview the children's guardians. Of the 917, 15 (1.6%) children were infested with the parasite. The prevalence was twice as high in females (10 children--2.2%) as compared to males (five children--1.1%), but due to the low number of infested individuals, the difference was statistically not significant (p = 0.18). The mean number of lesions found was 1.4 per child. One child presented bacterial superinfection. Of the 15 children infested, 10 (66.7%) studied in schools built on pyritiferous soil. The families of 12 children (79.9%) had been living in the area in which the study was conducted for less than eight years and were considered underprivileged families with the head of the household having a low education status. We conclude that in Criciúma tungiasis occurs in primary school children, but prevalence and parasite load are low.

[Tungiasis and myiasis]

Tungiasis (sand flea disease) and myiasis are ectoparasitoses, in which the infectious agent resides temporarily in the skin (myiasis) or dies and is eventually eliminated (tungiasis). Both diseases are zoonoses. Whereas in myiasis humans are only an accidental host, in tungiasis the prevalence in humans is similar to that of their domestic animals. In travellers returning from the tropics tungiasis and myiasis are not rare, however they are frequently misdiagnosed. The diagnosis of both infestations is made clinically, and laboratory investigations are not helpful. In tungiasis the clinical picture depends on the stage of the disease. A heavy local inflammation and bacterial superinfection are frequent. Therapy consists in the complete elimination of the parasite. The repellent Zanzarin effectively protects against sand fleas.

Controlling tungiasis in an impoverished community: an intervention study

Background

In Brazil, tungiasis is endemic in some resource-poor communities where various domestic and sylvatic animals act as reservoirs for this zoonosis. To determine the effect of control measures on the prevalence and intensity of infestation of human and animal tungiasis, a repeated cross-sectional survey with intervention was carried out.

Methodology/Principal Findings

In a traditional fishing community in Northeast Brazil, humans and reservoir animals were treated, and premise-spraying using an insecticide was done, while a second fishing community served as a control. Both communities were followed up 10 times during a 12-month period. At baseline, prevalence of tungiasis was 43% (95% confidence interval [CI]: 35%–51%) and 37% (95% CI: 31%–43%) in control and intervention villages, respectively. During the study, prevalence of tungiasis dropped to 10% (95% CI: 8%–13%; p<0.001) in the intervention village, while the prevalence remained at a high level in the control village. However, after one year, at the end of the study, in both communities the prevalence of the infestation had reached pre-intervention levels. Whereas the intensity of infestation was significantly reduced in the intervention community (p<0.001), and remained low at the end of the study (p<0.001), it did not change in the control village.

Conclusion/Significance

Our study shows that a reduction of prevalence and intensity of infestation is possible, but in impoverished communities a long-lasting reduction of disease occurrence can only be achieved by the regular treatment of infested humans, the elimination of animal reservoirs, and, likely, through environmental changes.

Trial Registration

Controlled-Trials.com ISRCTN27670575

Tungiasis is a disease caused by the sand flea Tunga penetrans, a parasite prevalent in many impoverished communities in developing countries. The female sand flea penetrates into the skin of animals and humans where it grows rapidly in size, feeds on the host's blood, produces eggs which are expelled into the environment, and eventually dies in situ. The lesions become frequently superinfected and the infestation is associated with considerable morbidity. Clearly, tungiasis is a neglected disease of neglected populations. We investigated the impact of a package of intervention measures targeted against on-host and off-host stages of T. penetrans in a fishing community in Northeast Brazil. These measures decreased disease occurrence only temporarily, but had a sustained effect on the intensity of the infestation. Since infestation intensity and morbidity are correlated, presumably the intervention also lowered tungiasis-associated morbidity. Control measures similar to the ones used in this study may help to effectively control tungiasis in impoverished communities.

Investigations on the life cycle and morphology of Tunga penetrans in Brazil

In the present study, the life cycle of Tunga penetrans was established in Wistar rats in the laboratory, and the morphology of the resulting developmental stages was studied by means of light and scanning electron microscopy. It was seen that the females enter at a nonfertilized stage through the skin of their hosts. Only there the copulation occurs, while females and males brought together in a Petri dish showed no interest in each other. In any way -- fertilized or not -- the females start about 6 days after penetration and hypertrophy with the ejection of eggs. While fertilized eggs proceed to development, the unfertilized ones remain arrested. The eggs are ovoid and measure about 600 x 320 mum. The larvae hatch from the eggs 1-6 days (mean 3-4) after ejection. Formation of larvae 2 took at least another day, while 4 up to 10 days more were needed until this larva starts pupation (mean 5-7 days). The formation of the adult fleas inside the puparium occurred within 9-15 days (with a maximum hatch at day 12). Adult female fleas having reached the skin of a host start blood sucking within 5 min and prepare to enter the skin. After 24 h, the flea stacked already with two thirds of its body inside the skin. After 40 h, the penetration was completed, and feeding and hypertrophical enlargement started, which was completed on day 6, when eggs became ejected. When studying the morphology of the fleas obtained from different hosts, slight variations were seen, which, however, are not significant for a species separation but may be an indication of the presence of different strains/races or the beginning of such a formation.

Investigations on the biology, epidemiology, pathology, and control of Tunga penetrans in Brazil: VII. The importance of animal reservoirs for human infestation

In Brazil tungiasis is endemic in many resource-poor communities, where various domestic and sylvatic animals act as reservoirs for this zoonosis. To determine the role of animal reservoirs in human tungiasis, a cross-sectional study was performed in a traditional fishing community in northeast Brazil. The human and the animal populations were examined for the presence of embedded sand fleas and the prevalence and the intensity of infestation were correlated. The overall prevalence of tungiasis in humans was 39% (95% CI 34-43%). Of six mammal species present in the village, only cats and dogs were found infested. The prevalence in these animals was 59% (95% CI 50-68%). In households, where infested pet animals were present, a higher percentage of household members had tungiasis (42% [95% CI 30-53%] versus 27% [20-33%], p=0.02), and the intensity of the infestation was higher (six lesions versus two lesions, p=0.01). The intensity of infestation in animals correlated with the intensity of infestation in humans (rho=0.3, p=0.02). Living in a household with an infested dog or cat led to a 1.6-fold (95% CI 1.1-2.3, p=0.015) increase in the odds for the presence of tungiasis in household members in the bivariate analysis and remained a significant risk factor in the multivariate regression analysis. The study shows that in this impoverished community tungiasis is highly prevalent in humans and domestic animals. In particular, it underlines the importance to include animals in control operation aiming at the reduction of disease occurrence in the human population.

Imported tungiasis: a report of 19 cases and review of the literature

Tungiasis is an infestation caused by penetration in the skin of the gravid female of the flea Tunga penetrans. In the period 1991-2006, 19 patients with imported tungiasis were observed at our Institute. All patients were subjected to general and dermatological examination, laboratory tests (including bacteriological examinations) and surgical excision of the lesions with histopathological examination. In all patients tetanus prophylaxis was made. All patients were followed up for at least six weeks. Thirteen patients were males (68.4%) and 6 females (31.6%). The age ranged from 3 to 71 years (average age: 37.8 years). Eleven patients (57.9%) contracted the infestation in Central and South America and 8 (42.1%) in Africa. In 17 patients (89.5%) tungiasis was localized to the feet, in one to the hands and in one to a thigh. In 13 patients (68.4%) the infestation was characterized by a single lesion; in the other 6 patients (31.6%) the lesions were two. In 15 patients (78.9%) tungiasis was characterized by a papular or nodular lesion. Crusted (2 patients), pustular (2 patients) and bullous (1 patient) lesions were also observed; furthermore, one patient presented with a plantar wart-like lesion. In only one patient bacteriological examinations showed the growth of Staphylococcus aureus and Escherichia coli. All patients healed without complications.

Risk factors for tungiasis in Nigeria: identification of targets for effective intervention

BACKGROUND

The parasitic skin disease tungiasis (caused by the flea Tunga penetrans) affects resource-poor communities in Latin America, the Caribbean and sub-Saharan Africa. Prevalences in endemic areas are high, and severe pathology occurs commonly. However, risk factors for infestation have never been assessed in Africa.

METHODS AND FINDINGS

A cross-sectional study was conducted in Erekiti, a rural community in Lagos State (Nigeria), where tungiasis is endemic. Individuals were examined clinically for the presence of tungiasis, and a questionnaire was applied. Data from 643 individuals (86.6% of the target population) were analyzed; 252 (42.5%) were infested with T. penetrans. In the multivariate logistic regression analysis, presence of pigs on the compounds (adjusted odds ratio = 17.98; 95% confidence interval: 5.55-58.23), sand or clay floor inside houses (9.33; 5.06-17.19), and having the common resting place outside the house (7.14; 4.0-14.29) were the most important risk factors identified. The regular use of closed footwear (0.34; 0.18-0.62) and the use of insecticides indoors (0.2; 0.05-0.83) were protective against infestation. The population attributable fractions associated with tungiasis were: sand or clay floor inside the house (73.7%), resting usually outside the house (65.5%), no regular use of closed footwear (51.1%), and pigs on the compound (37.9%).

CONCLUSION

The presence of tungiasis in Erekiti is determined to an important extent by a limited number of modifiable variables. Effective and sustainable intervention measures addressing these factors need to be implemented in this and other West African communities with high disease burden.

Upper eyelid localisation of Tunga penetrans

PURPOSE

This report describes two cases of palpebral localisation of Tunga penetrans.

METHODS

Two Congolese patients (a 17-year-old black man and a 12-year-old black girl) presented with a history of itching and oedema of the left upper eyelid.

RESULTS

On inspection and slit lamp examination, the patients manifested the characteristic lesion of a white translucent papule with a central black pit. Scraping of the lesion revealed a gravid adult female flea, allowing the diagnosis of infection with the flea T. penetrans. After removal of the parasite, a complete local recovery occurred over a 1-week period with local application of tetracycline.

CONCLUSION

With the increase in international travelling, it is useful to know that eyelid localisation of T. penetrans is possible.

Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. VI. Natural history of the infestation in laboratory-raised Wistar rats

Tungiasis is endemic in many countries in Latin America, the Caribbean and sub-Saharan Africa, and it is associated with severe morbidity. The pathophysiological and immunological characteristics of the ectoparasitosis are not well understood, and no effective therapy is currently available. The aim of this study was to describe the natural history of tungiasis in laboratory-raised Wistar rats. The rats were exposed in the laboratory to the parasite or were kept in a natural environment with an intense transmission of Tunga penetrans. The time course of the infestation was determined, and lesions were photographed, described clinically in detail and biopsied. Biopsies were examined histopathologically and by light and scanning electron microscopy. Based on these findings, the natural history of tungiasis in Wistar rats was described and divided in five stages. Our data show that the natural history of tungiasis in Wistar rats and humans is almost identical, except that in the animals, the basement membrane disrupts 5 days after penetration and provokes an intense infiltration of the dermis, while in humans, the basement membrane remains intact. The study indicates that the Wistar rat is an appropriate model for the study of clinical and pathological aspects of tungiasis. Using this model should enable a better understanding of the pathophysiology and immunology of the ectoparasitosis.

[Tungiasis: a neglected disease causing severe morbidity in a shantytown in Fortaleza, State of Ceará]

The parasitic skin disease tungiasis, caused by the jigger flea Tunga penetrans, is endemic in low-income communities in Brazil. In this study, inhabitants of a shantytown in Fortaleza, northeastern Brazil, who had an elevated parasite load, were identified. The number of lesions, localization, staging and associated diseases were recorded. The 142 individuals identified were living in extremely precarious housing conditions. A total of 3,445 lesions located on the feet were counted (median = 17 lesions; maximum = 98 lesions). Almost without exception, the individuals had nail deformation and edema, and more than 70% presented with pain and fissures. There was nail loss in 46%; deformation of the digits in 25%; abscesses in 42%; and complaints of walking difficulty in 59%. Our data show that tungiasis in this low-income urban community typical of northeastern Brazil was associated with severe morbidity. Tungiasis needs to be recognized as a public health problem in this study area and other similar endemic areas.

Tungiasis: high prevalence, parasite load, and morbidity in a rural community in Lagos State, Nigeria

BACKGROUND

Tungiasis is common in resource-poor populations throughout Latin America, the Caribbean, and sub-Saharan Africa, but epidemiologic data from Africa on this ectoparasitosis are scarce.

METHODS

A cross-sectional study was carried out in a representative sample of a rural community in Lagos State, 54 km west of Lagos (Nigeria). In the dry season, 142 households of the community were randomly selected and visited. Family members were examined for the presence of tungiasis. The localization, number, and stage of penetrated fleas, as well as the associated morbidity, were documented.

RESULTS

Five hundred and fifty-seven individuals were examined, 299 (53.7%) males and 258 (46.3%) females. In total, 252 (45.2%; 95% confidence interval, 41.1-49.5) were infested with Tunga penetrans. The prevalence was highest between the ages of 5 and 14 years, decreased in adults, and increased again in the elderly. There was no statistically significant difference between the prevalence in males and females (47.2% vs. 43.0%; P = 0.3). Almost 95% of lesions were localized on the feet. Ten per cent of individuals presented with sand fleas on the hands and elbows. The median parasite load was six (interquartile range, 3-16). Individuals aged 60 years or over had significantly more lesions (median of 41 lesions; P < 0.01). About one-third of the study participants found it difficult to walk; in 10% of cases, fissures were present. Superinfection was common.

CONCLUSIONS

The prevalence of tungiasis and the parasite load were high, and the severity of the disease was considerable. The prevalence and parasite burden showed a characteristic distribution. In western Nigeria, tungiasis needs to be regarded as an important public health problem.

Tunga penetrans: a stowaway from around the world

Tungiasis is a cutaneous ectoparasitic infestation by the female sand flea Tunga penetrans. It is predominantly a health problem in sub-Saharan Africa, the Caribbean, Latin America and South America. However, increasing numbers of returning travellers, immigrants, and adopted children are also affected in non-tropical countries. It is a cause of substantial morbidity, with prevalence rates as high as 76% in certain endemic areas. To date, the early extraction of the flea is still the first line therapy.

Tungiasis and myiasis

Tungiasis and myiasis are common ectoparasitic infestations that occur in developing countries in the tropics, particularly where poverty and poor standards of basic hygiene exist. The growth in international travel to and from these regions has led to an increase in the presentation of these conditions in nonendemic countries. Despite recent progress in the treatment and prevention of tungiasis and myiasis, diagnosis can present a challenge to those unfamiliar with these conditions, especially when they present in nonendemic countries. Tungiasis is caused by the penetration of the female sand flea, Tunga penetrans, into the epidermis of the host. Myiasis is a parasitic infection of the skin and mucous membranes in which the larvae of Diptera insects penetrate healthy or altered skin depending on the species. Infestations are usually self-limited and present few complications. Social neglect and inadequate health behavior in economically depressed urban neighborhoods, however, may lead to secondary infections and complications.

Morbidity assessment in sand flea disease (tungiasis)

Tungiasis, caused by the sand flea Tunga penetrans, is a health problem in many impoverished communities in Latin America, the Caribbean, and sub-Saharan Africa. Sand flea disease is associated with a broad spectrum of clinical and histological pathology. The factors determining the disease burden in endemic communities are not well understood, and severity of clinical pathology has never been assessed quantitatively. Thus, two severity scores were developed: one for acute disease and one for chronic sequels. These scores were evaluated in a cohort of 70 severely infested patients living in a shantytown in Fortaleza, a capital city in Northeast Brazil. Patients were examined during a period of 25 days and followed-up after a twice daily application of a plant-based repellent to prevent reinfestation. The severity score for acute disease symptoms significantly correlated with the infestation rate and the number of embedded fleas. It turned zero when reinfestation was prevented. The score for chronic disease also significantly correlated with the infestation rate. Tungiasis is associated with considerable acute and chronic morbidity. The degree of acute morbidity is directly related to the number of embedded sand fleas. When transmission is interrupted, the chronic morbidity reflects the infestation rates individuals have experienced in the past.

A plant-based repellent protects against Tunga penetrans infestation and sand flea disease

Tungiasis is a parasitic skin disease prevalent in impoverished populations in the tropics and associated with considerable morbidity. Treatment options are limited and prophylaxis has never been attempted. We assessed the effectiveness of a plant-based repellent to prevent infestation with Tunga penetrans and sand flea disease in an urban squatter settlement in Fortaleza, Northeast Brazil. Two cohorts were formed. One cohort started with the intervention while another served as control. The plant-based repellent Zanzarin was applied twice daily on the skin of the feet. After 4 weeks and a wash-out-phase of another 2 weeks, cross-over was performed. Study members were examined twice per week for the presence of newly embedded sand fleas. The number of viable and dead sand fleas and the total number of sand flea lesions were determined. Sentinel rats were used to assess local transmission dynamics. Outcome measures were the number of newly embedded sand fleas per individual per day, number of sand flea lesions per individual according to the stage, as well as type and degree of clinical pathology. Zanzarin applied twice daily on the feet reduced the number of newly embedded fleas by 92% (interquartile range 81-100%), the total number of lesions by 87% (81-98%) and reversed tungiasis-associated clinical pathology almost completely. In conclusion, in a setting in which tungiasis is an important health threat, the daily application of a plant-based repellent prevented the infestation with T. penetrans and sand flea disease.

Tungiasis

Tungiasis is a neglected parasitic skin disease caused by the permanent penetration of the female sand flea (also called jigger flea) Tunga penetrans into the skin of its host. After penetration, most commonly on the feet, the flea undergoes an impressing hypertrophy, and some days later the abdominal segments of the flea have enlarged up to the size of about 1 cm. The flea infestation is associated with poverty and occurs in many resource-poor communities in the Caribbean, South America and Africa. In this review, a historical overview on tungiasis is given. The natural history, pathology, epidemiology, diagnosis, therapy and control of the parasitic skin disease are discussed. It is concluded that tungiasis is an important parasitosis causing considerable morbidity in affected populations. Future studies are needed to increase the knowledge on the biology, pathophysiology, epidemiology, therapy and control of the ectoparasite.

Tungiasis in rural Haiti: a community-based response

Tungiasis is a disease endemic to poor communities in Latin America, the Caribbean and Africa. It is caused by the female flea, Tunga penetrans, which burrows into the skin of its host to feed while producing and extruding eggs. Consequent lesions may be painful and even crippling with damage ranging from mild erythema and swelling to necrosis. Superinfection of lesions can be serious and may result in auto-amputation or death from tetanus. We describe an outbreak of tungiasis in rural Haiti and a community-based intervention used to address it. Of 177 patients assessed, 132 (47 female, 85 male, 23 children) had tungiasis lesions. Forty-four patients had clinical signs of superinfection; 15 had ectopic lesions. Community health workers cleaned and disinfected patients' feet and any parts of the body with ectopic lesions, and then extracted fleas from existing lesions. Patients with superinfections were treated with appropriate antibiotics. Over 1000 pairs of shoes were distributed in the villages. Over 400 adults were given tetanus vaccinations during follow-up visits. Patients who had been treated reported feeling better and those who had received shoes indicated they had not developed new lesions. All superinfections were resolved. We concluded that community-based care can treat tungiasis effectively.

Leukocytosis and blood eosinophilia in a polyparasitised population in north-eastern Brazil

It has long been known that leukocytosis and blood eosinophilia are common in the tropical environment, but data derived from population-based studies are scarce. A study was undertaken in a fishing village in north-east Brazil where both intestinal helminthiases and parasitic skin diseases are common. Of 409 individuals studied, 128 (31.3%) were infected with one intestinal helminth or ectoparasite species, 93 (22.7%) with two, 61 (14.9%) with three, 25 (6.1%) with four and 11 (2.7%) with more than four species; no parasites were found in 91 (22.2%) individuals. Leukocyte counts ranged between 3,300 cells/microl and 16,100 cells/microl (median, 7,200 cells/microl) and eosinophil counts between 40 cells/microl and 5,460 cells/microl (median, 455 cells/microl). Eosinophilia (>500/microl) was detected in 44.7% of the individuals, and hypereosinophilia (>1,000/microl) in 12.9%. Thirty-six (8.8%) individuals showed leukocytosis. While 75% of individuals with normal eosinophil counts were considered parasite-free, only 14% with eosinophilia and 11% with hypereosinophilia did not have enteroparasites or ectoparasites. Multivariate regression showed that the probability of eosinophilia and hypereosinophilia, but not of leukocytosis, increased with the number of parasite species present. The data show that eosinophilia occurs in almost one-half of the individuals from a resource-poor setting and that it is significantly associated with the presence of intestinal helminths, but not with the presence of ectoparasites.

Ectoparasitic infestations

Ectoparasitic infestations are highly prevalent in resource-poor populations throughout the world and are associated with considerable morbidity. Reliable data on the epidemiology, immunology, and therapy of ectoparasitic infestations and on the biology of the parasites remain scarce. The control of parasitic skin diseases, such as scabies, pediculosis, tungiasis, myiasis, and cutaneous larva migrans in endemic areas remains a challenge. Using appropriate study designs, it is imperative to increase further the knowledge on the various aspects of the parasites and the infestations they cause.

The animal reservoir of Tunga penetrans in severely affected communities of north-east Brazil

Tungiasis is a zoonotic ectoparasitosis caused by the sand flea Tunga penetrans L. (Siphonaptera: Tungidae). This disease is hyperendemic in poor communities of north-east Brazil, causing considerable morbidity in affected human populations, but the animal reservoirs have not been investigated previously in Brazil. To assess the prevalence and intensity of T. penetrans infection in domestic and peri-domestic animals, as well as in the human population, we surveyed two typical communities of north-east Brazil: an urban slum and a traditional fishing village. In the slum we examined 849 humans, 121 cats, 82 dogs, 2 pigs, 2 rabbits, 1 monkey and 56 rodents, comprising 34 rats (Rattus rattus L.) and 22 mice (Mus domesticus L). In the fishing village we examined 505 humans, 68 dogs, 37 cats, 7 donkeys, 4 cattle, 3 pigs and 1 monkey. Tungiasis was common among dogs and cats of both communities, with respective prevalence rates of 67.1% (95% CI: 55.8-77.1) and 30.9% (95% CI: 20.2-43.3) in dogs, 49.6% (95% CI: 40.4-58.8) and 32.4% (95% CI: 18.0-49.8) in cats. Slum rats were 41.2% (95% CI: 24.6-59.3) infested, but the other animals were not. Human prevalence rates were 54.4% (95% CI: 51.0-57.8) in the slum and 52.1% (95% CI: 47.6-56.5) in the fishing village. High prevalence rates (range 31-67%) of tungiasis in humans, pets and rats (but apparently not other animals) indicate the need for an eco-epidemiological approach to control of this anthropo-zoonotic problem.

Therapy of tungiasis: a double-blinded randomized controlled trial with oral ivermectin

Tungiasis is an ectoparasitosis causing considerable pathology in endemic areas. Standard therapy consists of removing the embedded parasite with a sterile needle. There is no effective chemotherapy at hand. To fill this gap, a double-blinded randomized controlled trial with oral ivermectin was conducted. A total of 54 individuals (27 in the placebo group, 27 in the ivermectin group) was followed up for seven days. They presented a total of 192 lesions. Patients received either ivermectin (300 microg/kg body weight at a single dose, repeated after 24 h) or placebo. Outcome measures included the clinical stage of lesion, presence of erythema, pain, itching, signs of viability of the parasite, and total lysis of flea. The ratio of fleas with total lysis per total number of fleas was slightly higher in the ivermectin group; however, this difference was not statistically significant. There was no significant difference in any of the other outcome measures between the treatment and the placebo group. The results show that oral ivermectin is without any clinically significant efficacy against embedded sand fleas at the dose given.

Blood-feeding of Tunga penetrans males

The jigger Tunga penetrans (Linnaeus, 1758: type-species of the family Tungidae) is the smallest known species of flea (Siphonaptera), causing serious ectoparasitosis of humans and domestic animals. The adult female Tunga lodges in the epidermis of the mammalian host, grows by neosomy, becomes gravid and expels eggs. Relatively little is known about the free-living male Tunga adults. Among impoverished communities of Fortaleza in north-east Brazil, we observed T. penetrans males as well as females penetrating the skin of human hosts. After penetrating the epidermis for a few hours, evidently for capillary feeding from the dermis, males withdrew their mouthparts and crawled away, whereas the females remained completely embedded, hypertrophying to become gravid, eventually dying in situ after oviposition. Caged rats were placed on the sandy soil and examined periodically for Tunga infestation. On five rats we obtained 140 females embedded and we detected 75 males biting, with rat erythrocytes observed in the proventriculus and midgut of all five males dissected and examined microscopically. This confirms that T. penetrans males are hamatophagous ectoparasites of mammals.

High infection rate of Wolbachia endobacteria in the sand flea Tunga penetrans from Brazil

Tunga penetrans is an ectoparasite causing considerable morbidity in endemic communities. Recently, endobacteria of the genus Wolbachia were identified also in T. penetrans. Since Wolbachia were suggested as targets for intervention of insect pests and human filariasis, sand fleas were collected from infested humans, dogs and rats in a hyperendemic area in northeastern Brazil, and screened for Wolbachia infections. Twenty-one adult fleas and four batches of flea eggs were examined by PCR using primers targeting the 16S rDNA, the DNA coding for FtsZ cell-cycle protein or a Wolbachia surface protein (WSP-1). Wolbachia were detected in all examined samples from eggs, free-living male and female fleas and from neosomic female fleas. No Wolbachia DNA was detected in two samples containing flea faeces. In addition, Wolbachia were labelled by immunohistology in the ovaries of 37 female fleas using antisera raised against WSP-1 of Wolbachia the filarial parasite Dirofilaria immitis. In the vicinity of the embedded fleas containing the Wolbachia, infiltrations of neutrophils and macrophages were observed. This study showed that Wolbachia endobacteria are abundant in T. penetrans and that all examined fleas were infected by these endobacteria. Our findings may have important implications for the future development of control strategies for human tungiasis.

Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. V. Cytokine concentrations in experimentally infected Wistar rats

Tungiasis is caused by the penetration of the female sand flea Tunga penetrans into the skin of its host. This parasitic skin disease is almost invariably associated with an intense inflammation around embedded fleas, the underlying mechanisms being unknown. A study was undertaken to determine whether Wistar rats can be used as an animal model to assess cytokine kinetics during the natural course of the infection. Laboratory-raised Wistar rats were exposed in cages put on the soil in an area with high human attack rates. Rats were examined daily and blood samples were taken before exposure and at 2, 6, 10, 13, 16 and 20 days after flea penetration. TNF-alpha, IL-1 beta, IFN-gamma, IL-4, IL-10 and CINC (a rat cytokine- induced neutrophil chemoattractant and member of the IL-8 family) were determined by enzyme immunoassay. The results showed an increasing serum concentration of TNF-alpha and IL-1 beta 10-13 days after penetration and a rapid increase in IL-4 2 days after fleas became embedded. During the natural course of the infection, the ratio of the serum concentration of TNF-alpha to that of IL-10 decreased, indicating a relative increase in the secretion of the anti-inflammatory cytokine. The treatment of lesions with silicone oil abrogated the natural disease course and changed the pattern of cytokine secretion. We conclude that the Wistar rat is an appropriate model to study immune responses in tungiasis.

High attack rate of Tunga penetrans (Linnaeus 1758) infestation in an impoverished Brazilian community

Tungiasis (jigger) is endemic in many impoverished communities in many parts of Brazil. Forty-seven individuals entering an endemic area were followed up for a period of six weeks and regularly examined for the presence of newly embedded sand fleas. At the end of the third week, the attack rate of Tunga penetrans infestation had already approached 100%.