RESUMO
Upper extremity infections are common. Most infections can be effectively treated with minor surgical procedures and/or oral antibiotics; however, inappropriate or delayed care can result in significant, long-term morbidity. The basic principles of treating hand infections were described more than a century ago and most remain relevant today. Immunosuppressant medications, chronic health conditions such as diabetes and human immunodeficiency virus, and public health problems like intravenous drug use, have changed the landscape of hand infections and provide new challenges in treatment.
Assuntos
Mãos/microbiologia , Osteomielite/epidemiologia , Infecções dos Tecidos Moles/epidemiologia , Antibacterianos/uso terapêutico , Úlcera de Buruli/epidemiologia , Comorbidade , Diabetes Mellitus/epidemiologia , Farmacorresistência Bacteriana , Doenças Endêmicas , Infecções por HIV/epidemiologia , Mãos/parasitologia , Humanos , Hospedeiro Imunocomprometido , Incidência , Leishmaniose/epidemiologia , Traumatismos Ocupacionais/epidemiologia , Osteomielite/terapia , Saúde Pública , Fatores de Risco , Infecções dos Tecidos Moles/terapia , Abuso de Substâncias por Via Intravenosa/epidemiologia , Tuberculose/epidemiologia , Bouba/epidemiologiaRESUMO
A 73-year-old man living in Kawamata-machi, Fukushima Prefecture, Northeastern Honshu, Japan, visited a hospital with complaints of a subcutaneous swelling that had developed on the back of his left hand. The nodule was surgically removed from the vagina fibrosa tendinis of his left forefinger. Based on the histopathological characteristics, the causative agent of this nodule was identified as a female Onchocerca dewittei japonica (Spirurida: Onchocercidae). The species identification was confirmed by cox1 gene sequencing of the worm tissues from paraffin-embedded sections of the nodule. Although 11 cases of zoonotic onchocercosis have previously been recorded in Kyushu and Western Honshu, Japan, the present findings represent the first human case of infection with O. dewittei japonica in Northeastern Honshu, Japan.
Assuntos
Onchocerca/genética , Oncocercose/diagnóstico , Doenças dos Suínos/transmissão , Zoonoses/transmissão , Idoso , Animais , Ciclo-Oxigenase 1/genética , Feminino , Mãos/parasitologia , Mãos/patologia , Humanos , Japão , Masculino , Onchocerca/isolamento & purificação , Sus scrofa/parasitologia , Suínos , Doenças dos Suínos/parasitologia , Zoonoses/parasitologiaRESUMO
BACKGROUND: The treatment of Leishmaniasis caused by Leishmania (Viannia) guyanensis is based on a weak strength of evidence from very few clinical trials and some case series reports. Current treatment guidelines recommend pentamidine isethionate or meglumine antimoniate (Glucantime) as the first-line choices. Both are parenteral drugs with a low therapeutic indexes leading to a high risk of undesired effects. Imidazole derivatives interfere with the production of leishmanial ergosterol, an essential component of their membrane structure. One drug that has been studied in different clinical presentations of Leishmania is fluconazole, a hydrophilic bis-triazole, which is easily absorbed through the oral route with a low toxicity profile and is considered safe for children. This drug is readily available in poor countries with a reasonable cost making it a potential option for treating leishmaniasis. METHODS AND FINDINGS: An adaptive nonrandomized clinical trial with sequential groups with dose escalation of oral fluconazole was designed to treat adult men with localized cutaneous leishmaniasis (LCL) in Manaus, Brazil. Eligible participants were patients with LCL with confirmed Leishmania guyanensis infection. RESULTS: Twenty adult male patients were treated with 450 mg of fluconazole daily for 30 days. One patient (5%) was cured within 30 days of treatment. Of the 19 failures (95%), 13 developed a worsening of ulcers and six evolved lymphatic spreading of the disease. Planned dose escalation was suspended after the disappointing failure rate during the first stage of the trial. CONCLUSION/SIGNIFICANCE: Oral fluconazole, at the dose of 450mg per day, was not efficacious against LCL caused by Leishmania guyanensis in adult men. TRIAL REGISTRATION: Brazilian Clinical Trial Registration (ReBec)-RBR-8w292w; UTN number-1158-2421.
Assuntos
Antiprotozoários/uso terapêutico , Fluconazol/uso terapêutico , Leishmania guyanensis/efeitos dos fármacos , Leishmaniose Cutânea/tratamento farmacológico , Administração Oral , Adolescente , Adulto , Antiprotozoários/administração & dosagem , Brasil , Fluconazol/administração & dosagem , Mãos/diagnóstico por imagem , Mãos/parasitologia , Humanos , Leishmania guyanensis/patogenicidade , Leishmaniose Cutânea/parasitologia , Leishmaniose Cutânea/patologia , Masculino , Pessoa de Meia-Idade , Ensaios Clínicos Controlados não Aleatórios como Assunto , Falha de Tratamento , Adulto JovemRESUMO
Approximately one-quarter of the world's population is infected with at least one species of soil-transmitted helminth (STH). The role of produce and hands in STH transmission is not well understood. We collected and processed mother hand rinse and garden-grown produce rinse samples from 116 rural households in Kakamega, Kenya, in an area previously identified to have high STH egg contamination in household soil. Ascaris was the only STH species detected; 0.9% of hand rinse, 3.5% of leafy produce, and 1.8% of root produce samples had Ascaris eggs. Our results indicate produce and hands can carry Ascaris eggs. However, due to the low detected prevalence of eggs on hands and produce, and a high prevalence of cooking the produce items tested, these pathways might have a minor contribution to STH exposure in this setting.
Assuntos
Ascaríase/epidemiologia , Ascaríase/transmissão , Mãos/parasitologia , População Rural , Solo/parasitologia , Animais , Ascaris/isolamento & purificação , Produtos Agrícolas/parasitologia , Características da Família , Feminino , Contaminação de Alimentos , Parasitologia de Alimentos , Humanos , Quênia/epidemiologia , Mães , PrevalênciaRESUMO
Hookworm-related cutaneous larva migrans (HrCLM) is a skin disease caused by infection with the larvae of animal hookworms. With conditions for infection more favourable in tropical climates, HrCLM in the UK is classically diagnosed in the returning traveller. We present two cases of clinically diagnosed UK-acquired HrCLM from a district general hospital in the south of England. A 68-year-old woman presented with a pruritic serpiginous tract on the right hand. She was a keen gardener and had been handling compost. A 50-year-old man, a long distance runner, presented with a similar lesion on the dorsum of his foot. Both patients were treated with a single dose of albendazole. These cases may represent an emerging infection in the UK. In the absence of a suggestive travel history, early recognition followed by efficient access to therapy is vital for treating HrCLM transmitted in the UK.
Assuntos
Albendazol/uso terapêutico , Ancylostomatoidea/isolamento & purificação , Anti-Helmínticos/uso terapêutico , Pé/parasitologia , Mãos/parasitologia , Infecções por Uncinaria/diagnóstico , Larva Migrans/diagnóstico , Animais , Doenças Endêmicas , Inglaterra , Feminino , Pé/patologia , Mãos/patologia , Infecções por Uncinaria/tratamento farmacológico , Humanos , Larva Migrans/tratamento farmacológico , Masculino , Pessoa de Meia-Idade , Resultado do TratamentoRESUMO
Enterobius vermicularis is a helminth that is difficult to control, is found globally, especially in crowded conditions, and can be transmitted from person to person by contaminated hands. A newly developed method for the quantification of helminth eggs on hands was tested among schoolchildren in a rural South African region to look at the role hands play in helminth infection, and to determine the risk factors for hand contamination. The study found 16.6% of participants' hands positive for helminth eggs, with E. vermicularis most commonly identified. Egg concentrations on hands ranged from 0 to 57 eggs/2 hands. Gender, toilet type used at home, and not reporting to wash hands with soap before eating were all associated with the presence of eggs on hands. The study highlights the need to improve sanitation facilities, and promote handwashing with soap in schools to prevent transmission of E. vermicularis.
Assuntos
Enterobíase/epidemiologia , Enterobius/isolamento & purificação , Desinfecção das Mãos , Mãos/parasitologia , Adolescente , Animais , Criança , Pré-Escolar , Enterobíase/transmissão , Feminino , Humanos , Masculino , Contagem de Ovos de Parasitas , Fatores de Risco , População Rural , África do Sul/epidemiologiaRESUMO
BACKGROUND: The role that hands play in the transmission of Ascaris is not well understood. METHODS: A newly developed method to quantify the presence helminth eggs on hands was tested among a group of farmers in Vietnam. High turbidity in hand rinse samples meant that the adopted sugar solution had to be replaced by zinc sulphate as a flotation solution. RESULTS: The survey found 34% (31/90) of study participant hands' were positive for helminth eggs, though concentrations were low and ranged from 0-10 eggs/2 hands. The use of fresh excreta in agriculture was the only variable that showed an association with the concentrations of eggs found on hands. CONCLUSIONS: The results highlight the need to promote handwashing with soap to prevent the transmission of soil-transmitted helminth infections.
Assuntos
Doenças dos Trabalhadores Agrícolas/parasitologia , Mãos/parasitologia , Helmintíase/transmissão , Helmintos/isolamento & purificação , Óvulo , Adulto , Animais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Contagem de Ovos de Parasitas , Características de Residência , Fatores de Risco , População Rural , VietnãRESUMO
The importance of hands in the transmission of soil transmitted helminths, especially Ascaris and Trichuris infections, is under-researched. This is partly because of the absence of a reliable method to quantify the number of eggs on hands. Therefore, the aim of this study was to develop a method to assess the number of Ascaris eggs on hands and determine the egg recovery rate of the method. Under laboratory conditions, hands were seeded with a known number of Ascaris eggs, air dried and washed in a plastic bag retaining the washing water, in order to determine recovery rates of eggs for four different detergents (cationic [benzethonium chloride 0.1% and cetylpyridinium chloride CPC 0.1%], anionic [7X 1% - quadrafos, glycol ether, and dioctyl sulfoccinate sodium salt] and non-ionic [Tween80 0.1% -polyethylene glycol sorbitan monooleate]) and two egg detection methods (McMaster technique and FLOTAC). A modified concentration McMaster technique showed the highest egg recovery rate from bags. Two of the four diluted detergents (benzethonium chloride 0.1% and 7X 1%) also showed a higher egg recovery rate and were then compared with de-ionized water for recovery of helminth eggs from hands. The highest recovery rate (95.6%) was achieved with a hand rinse performed with 7X 1%. Washing hands with de-ionized water resulted in an egg recovery rate of 82.7%. This washing method performed with a low concentration of detergent offers potential for quantitative investigation of contamination of hands with Ascaris eggs and of their role in human infection. Follow-up studies are needed that validate the hand washing method under field conditions, e.g. including people of different age, lower levels of contamination and various levels of hand cleanliness.
Assuntos
Ascaris/fisiologia , Mãos/parasitologia , Contagem de Ovos de Parasitas , Animais , Ascaríase/prevenção & controle , Ascaris/crescimento & desenvolvimento , Ascaris/isolamento & purificação , Benzetônio/química , Detergentes/química , Desinfecção das Mãos , Humanos , Água/químicaRESUMO
AIMS: This study aimed to determine if the children's leisure activities impact the presence of pathogens on their hands and toys. METHODS & RESULTS: To assess the microbiological hazard in playground areas, a pilot study that included 12 children was conducted. We then conducted an intervention study; children's hands and toys were washed before playing. Faecal coliforms, pathogenic bacteria and Giardia lamblia were quantified by membrane filtration, selective media and flotation techniques, respectively; rotavirus, hepatitis A and rhinovirus by RT-PCR. Pilot study results revealed faecal contamination on children's hands and toys after playing on sidewalks and in public parks. Pathogenic bacteria, hepatitis A and G. lamblia on children's hands were also found. In the intervention study, Staphylococcus aureus and Klebsiella pneumoniae were found on children's hands at concentrations up to 2·5 × 10(4) and 1 × 10(4) CFU hands(-1), respectively. E. coli and Kl. pneumoniae were detected on toys (2·4 × 10(3) and 2·7 × 10(4) CFU toy(-1), respectively). Salmonella spp, Serratia spp and G. lamblia cysts were also present on toys. CONCLUSION: Children's play activities influence microbial presence on hands and toys; the transfer seems to occur in both ways. SIGNIFICANCE AND IMPACT OF THE STUDY: Control strategy needs to be implemented to protect children from infectious diseases.
Assuntos
Bactérias/isolamento & purificação , Microbiologia Ambiental , Mãos/microbiologia , Mãos/virologia , Jogos e Brinquedos , Vírus/isolamento & purificação , Criança , Pré-Escolar , Fezes/microbiologia , Fezes/parasitologia , Fezes/virologia , Feminino , Giardia lamblia/isolamento & purificação , Mãos/parasitologia , Humanos , Masculino , Projetos PilotoRESUMO
Flies of the genus Sarcophaga are known to cause myiasis in necrotic wounds and in anatomical cavities where fluids have collected. We present here the first case of external cutaneous myiasis by Sarcophaga larvae in the absence of skin ulcerations or necrosis. The host in this case was a geriatric patient with limited motor and neurological capacity who lives in a nursing home. Of particular importance is that Sarcophaga is capable of causing myiasis even in the absence of cutaneous infections or significant stasis of fluids or secretions and that the larvae can cause damage in otherwise healthy tissue.
Assuntos
Infecção Hospitalar/parasitologia , Mãos/parasitologia , Miíase/diagnóstico , Sarcofagídeos , Idoso , Animais , Vetores de Doenças , Feminino , Humanos , Miíase/fisiopatologiaRESUMO
Females of the African malaria vector, Anopheles gambiae Giles sensu stricto, use human volatiles to find their blood-host. Previous work has shown that ammonia, lactic acid, and aliphatic carboxylic acids significantly affect host orientation and attraction of this species. In the current study, these compounds were tested for their attractiveness relative to human emanations in vivo and in vitro. Emanations from a human hand, incubated sweat, and foot skin residues on a nylon sock were significantly attractive when tested against clean air. In a dual-choice test, foot skin residues were significantly more attractive than emanations from a human hand in vivo. Ammonia alone attracted more mosquitoes than fresh or incubated sweat. However, the odor of a human hand or of foot skin residues were more attractive than ammonia. A known attractive blend of ammonia with lactic acid and carboxylic acids was less effective than natural foot odorants. The results demonstrate that the synthetic blend based on skin odor is attractive for An. gambiae, but that in a choice situation in vitro natural skin odors are still preferred by the mosquito. Differences in volatile organic compound abundances between a worn sock and the synthetic blend may have resulted in stronger attraction to the sock. This suggests that candidate attractants should be evaluated with consideration of the strength of natural odorant sources. The data furthermore suggest that additional unidentified compounds from the human foot are involved in the host-seeking behavior of this mosquito species.
Assuntos
Anopheles/fisiologia , Odorantes , Feromônios/farmacologia , Olfato/fisiologia , Compostos Orgânicos Voláteis/farmacologia , Animais , Anopheles/efeitos dos fármacos , Ácidos Carboxílicos , Feminino , Pé/parasitologia , Mãos/parasitologia , Humanos , Ácido Láctico , Pele/parasitologia , SuorRESUMO
Tungiasis is caused by the jigger flea Tunga penetrans. We describe a case of severe infestation from Kigoma region, Western Tanzania. A 19-year-old male with epilepsy and mental disability presented with ulcerated and inflamed toes. Clinical examination revealed the presence of approximately 810 embedded jigger fleas on the feet, and another 60 lesions on the hands. The patient presented with fissures on the feet, hands and soles. He had difficulty walking and erythematous, oedematous, ulcerated and inflamed skin around the feet. Living conditions were precarious. The patient was assisted to extract the embedded fleas and his feet were washed with disinfectants. Oral antibiotics were given. The case shows that the disease may reach high parasite loads in Tanzanian individuals, with consequently severe pathology. There have been single reports of returning tourists from Tanzania with tungiasis, but the epidemiological situation and the geographic occurrence of the disease in this country are not known. Systematic studies are needed to increase knowledge on the epidemiological situation of tungasis in Tanzania and to identify endemic areas.
Assuntos
Ectoparasitoses/patologia , Sifonápteros , Animais , Antibacterianos/administração & dosagem , Cloxacilina/administração & dosagem , Ectoparasitoses/epidemiologia , Ectoparasitoses/parasitologia , Ectoparasitoses/terapia , Doenças Endêmicas , Mãos/parasitologia , Mãos/patologia , Humanos , Masculino , Tanzânia/epidemiologia , Dedos do Pé/parasitologia , Dedos do Pé/patologia , Úlcera/etiologia , Adulto JovemRESUMO
Approximately 15% of overall Australian household water usage is in the laundry; hence, a significant reduction in household drinking water demand could be achieved if potable-quality water used for clothes washing is replaced with recycled water. To investigate the microbiological safety of using recycled water in washing machines, bacteriophages MS-2 and PRD-1, Escherichia coli, and Cryptosporidium parvum oocysts were used in a series of experiments to investigate the transfer efficiency of enteric microorganisms from washing machine water to objects including hands, environmental surfaces, air, and fabric swatches. By determining the transference efficiency, it is possible to estimate the numbers of microorganisms that the user will be exposed to if recycled water with various levels of residual microorganisms is used in washing machines. Results, expressed as transfer rates to a given surface area per object, showed that the mean transfer efficiency of E. coli, bacteriophages MS-2 and PRD-1, and C. parvum oocysts from seeded water to fabric swatches ranged from 0.001% to 0.090%. Greatest exposure to microorganisms occurred through direct contact of hands with seeded water and via hand contact with contaminated fabric swatches. No microorganisms were detected in the air samples during the washing machine spin cycle, and transfer rates of bacteriophages from water to environmental surfaces were 100-fold less than from water directly to hands. Findings from this study provide relevant information that can be used to refine regulations governing recycled water and to allay public concerns about the use of recycled water.
Assuntos
Colífagos/isolamento & purificação , Cryptosporidium parvum/isolamento & purificação , Exposição Ambiental , Microbiologia Ambiental , Escherichia coli/isolamento & purificação , Animais , Contagem de Colônia Microbiana , Conservação dos Recursos Naturais/métodos , Mãos/microbiologia , Mãos/parasitologia , Mãos/virologia , Humanos , Lavanderia/métodos , Têxteis/microbiologia , Têxteis/parasitologia , Têxteis/virologiaAssuntos
Ascaríase/epidemiologia , Ascaris/isolamento & purificação , Mãos/parasitologia , Vigilância de Evento Sentinela , Adolescente , Adulto , Animais , Ascaríase/prevenção & controle , Criança , Pré-Escolar , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Lactente , Contagem de Ovos de Parasitas , Fatores de Risco , Condições Sociais , Tadjiquistão/epidemiologiaRESUMO
This study examined hand preference in baboons in a sample of 94 subjects for a unimanual task and in a sample of 104 subjects for a bimanual task. For the unimanual task, handedness was assessed by observing simple reaching for grains. For the bimanual task, tubes lined with peanut butter inside were presented to the baboons. The hand and the finger used to remove peanut butter were recorded. Population-level right-handedness was found for the bimanual but not the unimanual task. In addition, test-retest correlations showed consistency in hand use across time for the coordinated bimanual task but not the simple reaching task. No significant effects of age and sex on the direction and strength of hand preferences were found for either task. These are the first evidences of population-level handedness in baboons and the results are discussed in the context of evolutionary theories of cerebral dominance.
Assuntos
Lateralidade Funcional/fisiologia , Força da Mão/fisiologia , Mãos/parasitologia , Papio anubis/fisiologia , Desempenho Psicomotor/fisiologia , Análise de Variância , Animais , Comportamento Animal , Comportamento Alimentar/fisiologia , Primatas/fisiologiaRESUMO
Tungiasis is an important health problem in poor communities in Brazil and is associated with severe morbidity, particularly in children. The causative agent, the female flea Tunga penetrans, burrows into the skin of its host, where it develops, produces eggs and eventually dies. From the beginning of the penetration to the elimination of the carcass of the ectoparasite by skin repair mechanisms, the whole process takes 4-6 weeks. The present study is based on specimens from 86 patients, for some of whom the exact time of penetration was known. Lesions were photographed, described in detail and biopsied. Biopsies were examined histologically and by means of scanning electron microscopy (SEM). Based on clinical, SEM and histological findings, the "Fortaleza classification" was elaborated. This allows the natural history of tungiasis to be divided into five stages: (1) the penetration phase, (2) the phase of beginning hypertrophy, (3) the white halo phase, (4) the involution phase and (5) residues in the host's skin. Based on morphological and functional criteria, stages 3 and 4 are divided into further substages. The proposed Fortaleza classification can be used for clinical and epidemiological purposes. It allows a more precise diagnosis, enables the assessment of chemotherapeutic approaches and helps to evaluate control measures at the community level.
Assuntos
Ectoparasitoses/patologia , Sifonápteros , Idoso , Animais , Brasil/epidemiologia , Ectoparasitoses/epidemiologia , Ectoparasitoses/parasitologia , Ectoparasitoses/prevenção & controle , Feminino , Pé/parasitologia , Dermatoses do Pé/parasitologia , Dermatoses do Pé/patologia , Mãos/parasitologia , Humanos , Lactente , Estágios do Ciclo de Vida , Masculino , Sifonápteros/citologia , Sifonápteros/crescimento & desenvolvimento , Sifonápteros/patogenicidadeRESUMO
Tungiasis is caused by the penetration of the female sand flea Tunga penetrans into the epidermis. It is generally assumed that lesions are confined to the feet. To determine to what degree tungiasis occurs at other topographic sites, 1,184 inhabitants of a poor neighborhood in northeastern Brazil were examined; 33.6% were found to have tungiasis (95% confidence interval = 30.9-36.4%). Six percent presented lesions at locations other than the feet, with the hands being the most common ectopic site (5.5%). Other sites were the elbows, thighs, and gluteal region. Ectopic tungiasis was significantly associated with the total number of lesions (P < 0.001) and an age less than 15 years old (P = 0.02). In 86 patients actively recruited with lesions on their feet, ectopic localizations were observed in 25.6%. Since untreated sand flea lesions are prone to become superinfected, clinicians should be aware of not missing any ectopic localization of tungiasis.
Assuntos
Ectoparasitoses/parasitologia , Pé/parasitologia , Mãos/parasitologia , Sifonápteros/fisiologia , Adulto , Animais , Brasil/epidemiologia , Criança , Ectoparasitoses/epidemiologia , Feminino , Humanos , MasculinoRESUMO
Anthroponotic cutaneous leishmaniasis (ACL.) is known to cause single, self-healing and uncomplicated lesion mainly on the face. This paper presents a son and his mother with positive leishmaniasis IHAT (1/128 and 1/1924 respectively). The two isolates by enzymatic electrophoresis characterization proved to be Leishmania tropica that causes ACL. The son had two large ulcerative ACL on his left hand. The mother had a large ulceration and progressive erosion of the soft tissue (the right cheek and right eye) and the cartilage of the nose disfiguring and debilitating her face. The histpathological examination of the biopsy material obtained from the mother but not the material from her son, showed typical pathological picture of the basal cell carcinoma. No doubt, there are progressive changes in the pathogenesis of L. tropica and that it is one of the predisposing factor of the skin cell carcinoma.
Assuntos
Carcinoma Basocelular/complicações , Leishmania tropica/isolamento & purificação , Leishmaniose Cutânea/complicações , Leishmaniose Cutânea/patologia , Neoplasias Cutâneas/complicações , Adolescente , Adulto , Animais , Biópsia , Egito , Face/parasitologia , Face/patologia , Feminino , Mãos/parasitologia , Mãos/patologia , Humanos , Leishmania tropica/enzimologia , Masculino , Pele/parasitologia , Pele/patologiaRESUMO
The compatibility between sympatric and allopatric combinations of Onchocerca volvulus-anthropophilic species of Simulium was studied in the north-eastern focus of human onchocerciasis as well as in a densely populated locality of the Amazonas State in Venezuela. The objectives were to test the conjecture that local adaptation exists between the parasite and its vectors (the Onchocerca-Simulium complex hypothesis), and assess the possibility of the infection spreading from its present distributional range. For the homologous combination, O. volvulus-S. metallicum cytospecies E in Anzoátegui State (north-eastern focus), parasite yield was 45% in contrast to 1% for the heterologous, southern parasite-S. metallicum infection. This was significantly lower than the parasite yield (4-10%) expected after allowing for the effect of density-dependent limitation of infective larval output described in this paper for S. metallicum. The population of S. exiguum s.l. from southern Venezuela allowed no larval development beyond the L1 stage of either northern or southern parasites. Mechanisms for such refractoriness probably operate at the level of the thoracic muscles, not affecting microfilarial uptake or migration out of the bloodmeal. The parasite yield of southern O. volvulus in S. oyapockense s.l. flies biting man at Puerto Ayacucho (Amazonas) was about 1%, in agreement with the figures recorded for highly compatible sympatric combinations such as O. volvulus-S. ochraceum s.l. in Guatemala. No infective larval development of the northern parasite was observed in southern S. oyapockense. These results, together with considerations of typical worm burdens in the human host, presence/absence of armed cibaria in the simuliids, parasite-induced vector mortality, and fly biting rates, suggest a lower potential for onchocerciasis to spread between the northern and southern endemic areas of Venezuela than that between Amazonian hyperendemic locations and settlements outside this focus with high densities of S. oyapockense s.l.