The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Hermann Feldmeier - One of the best experts on this subject based on the ideXlab platform.
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Tungiasis-associated morbidity in pigs and dogs in endemic villages of Uganda
Parasites & vectors, 2016Co-Authors: Francis Mutebi, Norbert Mencke, Hermann Feldmeier, Jürgen Krücken, Charles Waiswa, Georg Von Samson-himmelstjernaAbstract:Background Tunga penetrans (Insecta, Siphonaptera, Tungidae) causes severe morbidity among heavily infected humans and animals in Latin America and sub-Saharan Africa. The clinical pathology of tungiasis in animals has never been studied systematically.
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Animal Reservoirs of Zoonotic Tungiasis in Endemic Rural Villages of Uganda.
PLoS neglected tropical diseases, 2015Co-Authors: Francis Mutebi, Norbert Mencke, Hermann Feldmeier, Jürgen Krücken, Charles Waiswa, Elizabeth Sentongo, Georg Von Samson-himmelstjernaAbstract:Background Animal tungiasis is believed to increase the prevalence and parasite burden in humans. Animal reservoirs of Tunga penetrans differ among endemic areas and their role in the epidemiology of tungiasis had never been investigated in Uganda. Methods and Findings To identify the major animal reservoirs of Tunga penetrans and their relative importance in the transmission of tungiasis in Uganda, a cross sectional study was conducted in animal rearing households in 10 endemic villages in Bugiri District. T. penetrans infections were detected in pigs, dogs, goats and a cat. The prevalences of households with tungiasis ranged from 0% to 71.4% (median 22.2) for animals and from 5 to 71.4% (median 27.8%) for humans. The prevalence of human tungiasis also varied among the population of the villages (median 7%, range 1.3–37.3%). Pig infections had the widest distribution (nine out of 10 villages) and highest prevalence (median 16.2%, range 0–64.1%). Pigs also had a higher number of embedded sand fleas than all other species combined (p
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the fate of the embedded virgin sand flea Tunga penetrans hypothesis self experimentation and photographic sequence
Travel Medicine and Infectious Disease, 2013Co-Authors: Marlene Thielecke, Hermann FeldmeierAbstract:Summary We describe the morphological development of a single penetrated female sand flea ( Tunga penetrans ) in a medical expatriate working in Madagascar. The embedded parasite developed abnormally in two aspects. First, it lived twice as long as usually. Second, it did not expel a single egg during a period of two months. We explain these abnormalities by the fact that the female sand flea remained virgin after the penetration into the skin and, therefore, mature eggs did not develop. Our observations are seminal findings in a long dispute between entomologists and suggest that normally the fertilization of a female sand flea takes place on-host when it is already embedded in the epidermis. We conclude that a single sand flea lesion in a traveller may develop in a different way as compared to parasites penetrating into the skin of inhabitants living in endemic areas.
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Topographic distribution of the sand flea Tunga penetrans in Wistar rats and humans in two endemic areas in Brazil.
The American journal of tropical medicine and hygiene, 2012Co-Authors: John Buckendahl, Lars Witt, Stefan Schwalfenberg, Jorg Heukelbach, Claudia M. Lins Calheiros, Hermann FeldmeierAbstract:Abstract. Tungiasis is a zoonosis caused by Tunga penetrans. In Brazil, tungiasis is endemic in many resource-poor communities, in which various domestic and sylvatic animals act as reservoirs. Eighty laboratory-raised Wistar rats were exposed to T. penetrans in areas of intense transmission: a fishing village and an urban shantytown in Ceara State, northeast Brazil. The topographic distribution of lesions in Wistar rats was compared with the distribution of lesions in humans in the same area. Our results show that the topographic distribution of embedded sand fleas was almost identical in Wistar rats and humans and that lesions were confined to the feet. In humans, 76% of all lesions were located periungually, whereas in Wistar rats, 67% of lesions were located at the distal end of the digits (P = 0.73). Both had the majority of lesions at the toes and digits: 70.2% versus 65.7% (P = 0.79). The Wistar rat model mirrors human tungiasis in topographic distribution.
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Occurrence of the off-host life stages of Tunga penetrans (Siphonaptera) in various environments in Brazil.
Annals of tropical medicine and parasitology, 2010Co-Authors: Pedro Marcos Linardi, Jorg Heukelbach, Claudia M. Lins Calheiros, E. B. Campelo-junior, E. M. Duarte, Hermann FeldmeierAbstract: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.
Jorg Heukelbach - One of the best experts on this subject based on the ideXlab platform.
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In vitro efficacy of four insecticides against eggs of Tunga penetrans (Siphonaptera)
The Open Dermatology Journal, 2013Co-Authors: Tim Kiesewetter, Liana Ariza, Maria M. Martins, Jean E. Limongi, Juliana Junqueira Da Silva, Julio Mendes, Claudia M. Lins Calheiros, Heiko Becher, Jorg HeukelbachAbstract:Systematic assessments of control measures against the jigger flea Tunga penetrans are scarce, and there are no published data available on the efficacy of environmental insecticides against immature stages. We tested four environmental contact insecticides used by Brazilian authorities for disease control (deltamethrin, bifenthrin, dichlorvos and etofenprox) against T. penetrans eggs. Eggs were reared in vitro. Hatch rates were observed under standardized conditions and compared to a control group (40 eggs in each group). No larvae hatched after treatment with the organophosphate dichlorvos (100% efficacy). The efficacies of the other products tested varied between 17% and 57%. The data show that the organophosphate dichlorvos had a good in vitro efficacy. The use of dichlorvos can be directed to typical spots where early stages of T. penetrans are expected, considering its toxicity. Disease control should also consist of prevention measures concerning housing and environmental conditions, veterinary and human health measures.
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In VitroEfficacy of Four Insecticides Against Eggs of Tunga penetrans (Siphonaptera)
The Open Dermatology Journal, 2013Co-Authors: Tim Kiesewetter, Liana Ariza, Maria M. Martins, Jean E. Limongi, Juliana Junqueira Da Silva, Julio Mendes, Claudia M. Lins Calheiros, Heiko Becher, Jorg HeukelbachAbstract:Systematic assessments of control measures against the jigger flea Tunga penetrans are scarce, and there are no published data available on the efficacy of environmental insecticides against immature stages. We tested four environmental contact insecticides used by Brazilian authorities for disease control (deltamethrin, bifenthrin, dichlorvos and etofenprox) against T. penetrans eggs. Eggs were reared in vitro. Hatch rates were observed under standardized conditions and compared to a control group (40 eggs in each group). No larvae hatched after treatment with the organophosphate dichlorvos (100% efficacy). The efficacies of the other products tested varied between 17% and 57%. The data show that the organophosphate dichlorvos had a good in vitro efficacy. The use of dichlorvos can be directed to typical spots where early stages of T. penetrans are expected, considering its toxicity. Disease control should also consist of prevention measures concerning housing and environmental conditions, veterinary and human health measures.
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Tunga penetrans and further parasites in the giant anteater (Myrmecophaga tridactyla) from Minas Gerais, Brazil
Parasitology research, 2012Co-Authors: Raphael Frank, Jorg Heukelbach, Christian Melaun, Maria Marlene Martins, André Luiz Quagliatto Santos, Sven KlimpelAbstract:The Brazilian savannah-like area, the Cerrado region, covers large areas of the country and provides a habitat for a multitude of different animal species. The giant anteater (Myrmecophaga tridactyla) is geographically widespread and one of the typical inhabitants of the Cerrado. They are listed as vulnerable by the International Union for Conservation of Nature and Natural Resources. A population loss of at least 30 % over the past 10 years has been estimated based on local extinctions, habitat loss and deaths caused by fires, roadkills and hunting. Little is known about ecological and in particular parasitic conditions of this highly specialised insectivore species. During September and November 2010 we examined three roadkilled giant anteater for the presence of metazoan ecto- and endoparasites. Besides the cestode species Oochoristica tetragonocephala and the tick species Amblyomma nodosum, we found for the first time the flea Tunga penetrans. Beside morphological flea species identification, we compared a fragment of the 16S rRNA gene of eggs, a molecular method utilised for the first time in this combination. The identification of T. penetrans in M. tridactyla represents a new host record and expands the host and distribution range of the zoonotic flea species.
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Topographic distribution of the sand flea Tunga penetrans in Wistar rats and humans in two endemic areas in Brazil.
The American journal of tropical medicine and hygiene, 2012Co-Authors: John Buckendahl, Lars Witt, Stefan Schwalfenberg, Jorg Heukelbach, Claudia M. Lins Calheiros, Hermann FeldmeierAbstract:Abstract. Tungiasis is a zoonosis caused by Tunga penetrans. In Brazil, tungiasis is endemic in many resource-poor communities, in which various domestic and sylvatic animals act as reservoirs. Eighty laboratory-raised Wistar rats were exposed to T. penetrans in areas of intense transmission: a fishing village and an urban shantytown in Ceara State, northeast Brazil. The topographic distribution of lesions in Wistar rats was compared with the distribution of lesions in humans in the same area. Our results show that the topographic distribution of embedded sand fleas was almost identical in Wistar rats and humans and that lesions were confined to the feet. In humans, 76% of all lesions were located periungually, whereas in Wistar rats, 67% of lesions were located at the distal end of the digits (P = 0.73). Both had the majority of lesions at the toes and digits: 70.2% versus 65.7% (P = 0.79). The Wistar rat model mirrors human tungiasis in topographic distribution.
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Occurrence of the off-host life stages of Tunga penetrans (Siphonaptera) in various environments in Brazil.
Annals of tropical medicine and parasitology, 2010Co-Authors: Pedro Marcos Linardi, Jorg Heukelbach, Claudia M. Lins Calheiros, E. B. Campelo-junior, E. M. Duarte, Hermann FeldmeierAbstract: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.
Norbert Mencke - One of the best experts on this subject based on the ideXlab platform.
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Tungiasis-associated morbidity in pigs and dogs in endemic villages of Uganda
Parasites & vectors, 2016Co-Authors: Francis Mutebi, Norbert Mencke, Hermann Feldmeier, Jürgen Krücken, Charles Waiswa, Georg Von Samson-himmelstjernaAbstract:Background Tunga penetrans (Insecta, Siphonaptera, Tungidae) causes severe morbidity among heavily infected humans and animals in Latin America and sub-Saharan Africa. The clinical pathology of tungiasis in animals has never been studied systematically.
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Animal Reservoirs of Zoonotic Tungiasis in Endemic Rural Villages of Uganda.
PLoS neglected tropical diseases, 2015Co-Authors: Francis Mutebi, Norbert Mencke, Hermann Feldmeier, Jürgen Krücken, Charles Waiswa, Elizabeth Sentongo, Georg Von Samson-himmelstjernaAbstract:Background Animal tungiasis is believed to increase the prevalence and parasite burden in humans. Animal reservoirs of Tunga penetrans differ among endemic areas and their role in the epidemiology of tungiasis had never been investigated in Uganda. Methods and Findings To identify the major animal reservoirs of Tunga penetrans and their relative importance in the transmission of tungiasis in Uganda, a cross sectional study was conducted in animal rearing households in 10 endemic villages in Bugiri District. T. penetrans infections were detected in pigs, dogs, goats and a cat. The prevalences of households with tungiasis ranged from 0% to 71.4% (median 22.2) for animals and from 5 to 71.4% (median 27.8%) for humans. The prevalence of human tungiasis also varied among the population of the villages (median 7%, range 1.3–37.3%). Pig infections had the widest distribution (nine out of 10 villages) and highest prevalence (median 16.2%, range 0–64.1%). Pigs also had a higher number of embedded sand fleas than all other species combined (p
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Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. VI. Natural history of the infestation in laboratory-raised Wistar rats
Parasitology Research, 2007Co-Authors: Hermann Feldmeier, Lars Witt, Raphael A. C. Capaz, Oliver Meckes, Stefan Schwalfenberg, Pedro Marcos Linardi, Ronaldo A. Ribeiro, Eric Van Marck, Heinz Mehlhorn, Norbert MenckeAbstract: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.
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Investigations on the life cycle and morphology of Tunga penetrans in Brazil.
Parasitology Research, 2007Co-Authors: Nadine Nagy, Norbert Mencke, Hermann Feldmeier, Jorg Heukelbach, Claudia M. Lins Calheiros, E. Abari, Jochen D'haese, Heinz MehlhornAbstract: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 × 320 μm. 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.
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Field trial of the efficacy of a combination of imidacloprid and permethrin against Tunga penetrans (sand flea, jigger flea) in dogs in Brazil
Parasitology Research, 2005Co-Authors: Sven Klimpel, Jorg Heukelbach, Hermann Feldmeier, Heinz Mehlhorn, Norbert MenckeAbstract:In a field trial in Brazil 17 dogs penetrated by females of the jigger flea, Tunga penetrans, were topically treated with a combination of 10% imidacloprid and 50% permethrin (Advantix®), while 17 dogs remained untreated. The follow–up controls on days 7, 14, 21 and 28 post–treatment clearly showed that, beginning from day 7, the flea load in treated dogs decreased, so that most of the dogs became free of tungiasis lesions, while in the untreated group the flea load remained high. Since the dogs distribute the flea eggs throughout the village, leading to a high incidence of tungiasis in humans, treatment of dogs probably also decreases the number of cases of tungiasis in the latter.
Lars Witt - One of the best experts on this subject based on the ideXlab platform.
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Topographic distribution of the sand flea Tunga penetrans in Wistar rats and humans in two endemic areas in Brazil.
The American journal of tropical medicine and hygiene, 2012Co-Authors: John Buckendahl, Lars Witt, Stefan Schwalfenberg, Jorg Heukelbach, Claudia M. Lins Calheiros, Hermann FeldmeierAbstract:Abstract. Tungiasis is a zoonosis caused by Tunga penetrans. In Brazil, tungiasis is endemic in many resource-poor communities, in which various domestic and sylvatic animals act as reservoirs. Eighty laboratory-raised Wistar rats were exposed to T. penetrans in areas of intense transmission: a fishing village and an urban shantytown in Ceara State, northeast Brazil. The topographic distribution of lesions in Wistar rats was compared with the distribution of lesions in humans in the same area. Our results show that the topographic distribution of embedded sand fleas was almost identical in Wistar rats and humans and that lesions were confined to the feet. In humans, 76% of all lesions were located periungually, whereas in Wistar rats, 67% of lesions were located at the distal end of the digits (P = 0.73). Both had the majority of lesions at the toes and digits: 70.2% versus 65.7% (P = 0.79). The Wistar rat model mirrors human tungiasis in topographic distribution.
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Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. VI. Natural history of the infestation in laboratory-raised Wistar rats
Parasitology Research, 2007Co-Authors: Hermann Feldmeier, Lars Witt, Raphael A. C. Capaz, Oliver Meckes, Stefan Schwalfenberg, Pedro Marcos Linardi, Ronaldo A. Ribeiro, Eric Van Marck, Heinz Mehlhorn, Norbert MenckeAbstract: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.
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INFESTATION OF WISTAR RATS WITH Tunga penetrans IN DIFFERENT MICROENVIRONMENTS
The American journal of tropical medicine and hygiene, 2007Co-Authors: Lars Witt, Stefan Schwalfenberg, Ronaldo A. Ribeiro, Jorg Heukelbach, Gundel Harms, Hermann FeldmeierAbstract:Tungiasis is a zoonotic ectoparasitosis that causes considerable morbidity in affected populations. The type of microenvironment that facilitates infestation of hosts by Tunga penetrans has not been investigated. In this study, we exposed 30 laboratory-raised Wistar rats, a suitable model for the infestation, at six different places characterized by different microenvironments in a hyperendemic fishing village in northeastern Brazil. During a period of two weeks, the animals were monitored and the number of embedded fleas was documented. The number of lesions varied considerably according to the microenvironment and was highest in a cage placed at the far end of a compound of a household affected by tungiasis. No penetration was observed inside houses. Results indicate that in this endemic area transmission of T. penetrans seems to occur mainly outdoors.
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Blood-feeding of Tunga penetrans males.
Medical and veterinary entomology, 2004Co-Authors: Lars Witt, Oliver Meckes, Stefan Schwalfenberg, Pedro Marcos Linardi, Ronaldo A. Ribeiro, Hermann Feldmeier, Jorg HeukelbachAbstract:. 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.
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High infection rate of Wolbachia endobacteria in the sand flea Tunga penetrans from Brazil.
Acta tropica, 2004Co-Authors: Jorg Heukelbach, Lars Witt, Hermann Feldmeier, Insa Bonow, Peter U. FischerAbstract: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.
Heinz Mehlhorn - One of the best experts on this subject based on the ideXlab platform.
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Repetitive sequences in the ITS1 region of the ribosomal DNA of Tunga penetrans and other flea species (Insecta, Siphonaptera)
Parasitology Research, 2008Co-Authors: Sara Gamerschlag, Hermann Feldmeier, Jorg Heukelbach, Heinz Mehlhorn, Jochen D’haeseAbstract:Different Tunga penetrans isolates from various hosts obtained from South America (Fortaleza. Brazil) have been studied by nucleotide sequence comparison of the first and the second internal transcribed spacer (ITS1, ITS2) of the ribosomal deoxyribonucleic acid (rDNA) and part of the mitochondrial 16S rDNA. Results show no significant host-dependent sequence differences. No indication for intraindividual and intraspecific polymorphisms could be detected. Comparing the ITS1 spacer region of T. penetrans from South America with that from Africa (Togo, Cameroon), distinct length variations have been observed caused by a repetitive sequence motif of 99 bp. The ITS1 from the South American T. penetrans contain two tandemly repeated copies, whereas four of these units are present in the spacer of the African T. penetrans . The absence of homogenization of these units indicates a recent separation of both populations. However, the different number of repetitions together with two base substitutions put the evolutionary distance of only 135 years as postulated for the transfer of T. penetrans from South America to Africa into question. Repetitive sequences could also be detected within the ITS1 rDNA region of other flea species Ctenocephalides felis , Echidnophaga gallinacea , Pulex irritans, Spilopsyllus cuniculi , and Xenopsylla cheopis . The repeat units with lengths from 10 to 99 bp are arranged in pure tandem or interspersed. The repetitive elements observed in the ITS1 of various flea species may serve as a valuable tool for phylogeographic studies.
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Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. VI. Natural history of the infestation in laboratory-raised Wistar rats
Parasitology Research, 2007Co-Authors: Hermann Feldmeier, Lars Witt, Raphael A. C. Capaz, Oliver Meckes, Stefan Schwalfenberg, Pedro Marcos Linardi, Ronaldo A. Ribeiro, Eric Van Marck, Heinz Mehlhorn, Norbert MenckeAbstract: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.
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Investigations on the life cycle and morphology of Tunga penetrans in Brazil.
Parasitology Research, 2007Co-Authors: Nadine Nagy, Norbert Mencke, Hermann Feldmeier, Jorg Heukelbach, Claudia M. Lins Calheiros, E. Abari, Jochen D'haese, Heinz MehlhornAbstract: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 × 320 μm. 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.
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Field trial of the efficacy of a combination of imidacloprid and permethrin against Tunga penetrans (sand flea, jigger flea) in dogs in Brazil
Parasitology Research, 2005Co-Authors: Sven Klimpel, Jorg Heukelbach, Hermann Feldmeier, Heinz Mehlhorn, Norbert MenckeAbstract:In a field trial in Brazil 17 dogs penetrated by females of the jigger flea, Tunga penetrans, were topically treated with a combination of 10% imidacloprid and 50% permethrin (Advantix®), while 17 dogs remained untreated. The follow–up controls on days 7, 14, 21 and 28 post–treatment clearly showed that, beginning from day 7, the flea load in treated dogs decreased, so that most of the dogs became free of tungiasis lesions, while in the untreated group the flea load remained high. Since the dogs distribute the flea eggs throughout the village, leading to a high incidence of tungiasis in humans, treatment of dogs probably also decreases the number of cases of tungiasis in the latter.
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Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. V. Cytokine concentrations in experimentally infected Wistar rats
Parasitology Research, 2004Co-Authors: Hermann Feldmeier, Oliver Liesenfeld, Lars-henrik Witt, Stefan Schwalfenberg, Ronaldo Albuquerque Ribeiro, Fernando Queiroz Cunha, Gundel Harms, Heinz Mehlhorn, Jorg HeukelbachAbstract: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-α, IL-1β, IFN-γ, 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-α and IL-1β 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-α 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.
