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Individual exposure to Simulium bites and intensity of Onchocerca volvulus infection
C A Jacobi, P Enyong, A Renz
Parasites & Vectors , 2010, DOI: 10.1186/1756-3305-3-53
Abstract: Using these data obtained by the two vector-collectors, we were able to calculate the Actual Index of Exposure (AIE). While the AIE in the savannah was on average 6,3%, it was 34% in the rainforest. The Effective Annual Transmission Potential (EATP) for individual villagers was about 20 fold higher in the rainforest compared to the savannah.Here we show for the first time that it is possible to determine the EATP. Further studies with more subjects are needed in the future. These data are important for the development of future treatment strategies.In the human population of hyperendemic onchocerciasis villages, a high individual parasite load results from an intense and prolonged exposure to the transmission of infective larvae of Onchocerca volvulus by the black fly Simulium vectors. Assessing heterogeneity in exposure may contribute to the ongoing debate about the processes generating overdispersion of parasite loads among hosts, namely, the fact that a majority of hosts harbour no or light infections while a few are heavily infected. Its quantification is important for the development of mathematical descriptions of parasite transmission dynamics. In West Africa, persons particularly at risk are fishermen, farmers and children who spend much of their daytime near Simulium damnosum s.l. infested rivers. The intensity of transmission is commonly assessed using standardized procedures with a standard fly collector, catching all simuliid female flies which come to feed on his fully exposed legs [1-4]. This number is referred to as the daily biting rate (DBR). Dissecting these flies will give us the number of infective L3 larvae = daily transmission potential (DTP). This method, although useful in providing data on Simulium landing rates and O. volvulus transmission potentials, cannot be used to calculate the actual number of infective larvae transmitted to individual villagers. Heterogeneity in exposure among villagers is likely to result from age- and sex-dependent
Distribution of Simulium species and its infection with Onchocerca volvulus along river Muvur, Mubi, Adamawa State
AH Bich, B Inuwa
Bayero Journal of Pure and Applied Sciences , 2010,
Abstract: A survey of the distribution of Simulium species complex population and its infection rate with Onchocerca volvulus was carried out along River Muvir, Mubi between July and August 2009. Black flies were collected using baits, pooter and hand nets. Out of 310 flies collected, 89 (28.70%) were found to be infected with microflariae. Detection of the parasites in the vector was attained by dissection of flies under dissecting microscope. The result revealed that the prevalence of microfilariae among insects collected in the months July and August was 23.08% and 21.47% respectively. Statistical analysis using t-test and ANOVA revealed that there was no significant difference (p<0.05) in the prevalence between the months of collection. They also showed no significant differences in microfilariae load between the three anatomical parts (the head, thorax and abdomen). These investigations showed that Simulium damnosum is wide spread along the River Muvur and a large population of flies is infected with Onchocerca volvulus.
Biting behaviour of Simulium damnosum complex and Onchocerca volvulus infection along the Osun River, Southwest Nigeria
Monsuru A Adeleke, Chiedu F Mafiana, Sammy O Sam-Wobo, Ganiyu O Olatunde, Uwem F Ekpo, Olaoluwa P Akinwale, Laurent Toe
Parasites & Vectors , 2010, DOI: 10.1186/1756-3305-3-93
Abstract: The results indicated that the majority of the flies collected at the three sampling points were nulliparous as they accounted for 53.90%, 57.86% and 59.58% of the flies dissected at Osun Budepo, Osun Ogbere and Osun Eleja, respectively. The parous rate was higher during the dry season than the wet season but the difference was not statistically significant (p < 0.05). The biting activity of the parous flies showed two peaks at Osun Budepo and three peaks at Osun Eleja and Osun Ogbere. Of the 1,472 flies dissected and 1,235 flies screened by molecular method, none was infected with Onchocerca parasite at the three sampling points however the annual biting rates at the three communities were higher than 1,000 considered as tolerable value for a person living in an onchocerciasis zone by Word Health Organization.The study has provided the baseline data for further study on onchocerciasis transmission dynamics and the need to intercept man- simuliid vector contact at the study area.In West Africa, members of Simulium damnosum complex are the only known vectors of human onchocerciasis [1]. The disease constitutes a serious public health problem of considerable magnitude in many riverine areas of West Africa. The disease is prevalent in 35 countries of the world of which 28 are in Africa and Nigeria accounts for one quarter of the global infection [2]. The current strategy of controlling the disease in Africa relies mostly on the annual chemotherapeutic treatment of the endemic communities through mass distribution of Ivermectin. Ivermectin has been proved to have microfilaricidal properties and substantially reduced the disease burden in many affected communities [3,4].Humans acquire infections after being bitten by black flies of the S. damnosum species complex carrying infective larvae of Onchocerca volvulus [4]. Therefore, surveillance on infectivity status of the Simulium vectors biting along the river systems is a vital component in monitoring the transmission leve
Biting on human body parts of Simulium vectors and its implication for the manifestation of Onchocerca nodules along Osun River, southwestern Nigeria  [PDF]
Monsuru Adebayo Adeleke , Sammy Olufemi Sam-Wobo , Olaoluwa Pheabian Akinwale , Ganiyu Olatunji Olatunde & Chiedu Felix Mafiana
Journal of Vector Borne Diseases , 2012,
Abstract: Background: The biting preference of Simulium vectors has been known to influence the distribution ofOnchocerca nodules and microfilariae in human body. There is, however, variation in biting pattern of Simuliumflies in different geographical locations. This study investigates the biting pattern on human parts by Simuliumvectors along Osun river system where Simulium soubrense Beffa form has been implicated as the dominantvector and its possible implication on the distribution of Onchocerca nodules on human body along the river.Methods: Flies were collected by consented fly capturers on exposed human parts namely head/neck region,arms, upper limb and lower limb in Osun Eleja and Osun Budepo along Osun river in the wet season (August–September) and the dry season (November–December) in 2008. The residents of the communities were alsoscreened for palpable Onchocerca nodules.Results: The results showed that number of flies collected below the ankle region was significantly higher thanthe number collected on other exposed parts (p <0.05) while the least was collected on head/neck region in bothseasons. The lower trunk was the most common site (60%) for nodule location at Osun Eleja followed by uppertrunk (40%). Nodules were not found in the head and limb regions. At Osun Budepo, the upper trunk was themost common site of the nodule location (53.8%) followed by the lower trunk (38.5%) and head region (7.7%).Conclusion: Though, most of the flies were caught at the ankle region, the biting of other parts coupled with thepresence of nodules at the head and upper trunk regions showed that Simulium vectors could obtain microfilariaefrom any part of the body, thus increasing the risk of onchocerciasis transmission.
Retarded Onchocerca volvulus L1 to L3 larval development in the Simulium damnosum vector after anti-wolbachial treatment of the human host
Anna Albers, Mathias Esum, Nicholas Tendongfor, Peter Enyong, Ute Klarmann, Samuel Wanji, Achim Hoerauf, Kenneth Pfarr
Parasites & Vectors , 2012, DOI: 10.1186/1756-3305-5-12
Abstract: Infected volunteers in Cameroon were randomly and blindly allocated into doxycycline (200 mg/day for 6 weeks) or placebo treatment groups. After treatment, blackflies were allowed to take a blood meal on the volunteers, captured and dissected for larval counting and DNA extraction for quantitative real-time PCR analysis.PCR results showed a clear reduction in Wolbachia DNA after doxycycline treatment in microfilariae from human skin biopsies with > 50% reduction at one month post-treatment, eventually reaching a reduction of > 80%. Larval stages recovered from the insect vector had similar levels of reduction of endosymbiotic bacteria. Larval recoveries were analysed longitudinally after treatment to follow the kinetics of larval development. Beginning at three months post-treatment, significantly fewer L3 were seen in the blackflies that had fed on doxycycline treated volunteers. Concomitant with this, the proportion of second stage larvae (L2) was significantly increased in this group.Doxycycline treatment and the resulting decline of Wolbachia endobacteria from the microfilaria resulted in retarded development of larvae in the insect vector. Thus, anti-wolbachial treatment could have an additive effect for interrupting transmission by reducing the number of L3 that can be transmitted by blackflies.Onchocerciasis, caused by Onchocerca volvulus, is endemic in many sub-Saharan countries with further foci in Latin America and Yemen [1,2]. The number of infections is estimated to be ~ 37 million [3,4]. The chronic nature and morbidity of onchocerciasis is associated with microfilariae (first stage larvae; Mf) that migrate through the skin and the eye. When the Mf die, the immune response to the dead larvae can result in dermatitis, skin atrophy and inflammation in the eyes. The latter can progress into reduced vision and blindness. Vector control and mass treatment with ivermectin, a strong microfilaricidal drug which can produce temporary sterility [5], have been suc
Primera descripción del hábitat acuático de Simulium guianense s.l. (Diptera: Simuliidae) en el área endémica de oncocercosis, al sur de Venezuela
Villamizar,Nestor; Cortez,José; Noya Alarcón,Oscar; Escalona,Marisela; Botto,Carlos; Grillet,María Eugenia;
Boletín de Malariología y Salud Ambiental , 2011,
Abstract: simulium guianense sensu lato is the main vector of onchocerca volvulus in the amazonian onchocerciasis focus, southern venezuela. here, we present the first report of the pre-adult aquatic habitat spatial distribution as well as the landscape and the habitat ecological characterization of this species complex within the endemic area. larvae and pupae were collected on submerged aquatic plants (podosteamaceas) located in a waterfall (ph = 7, conductivity = 158 umhos/cm, discharge = 0.12 m3/s) of the orinoquito river, in the upper orinoco-casiquiare biosphere reserve. these results will help with the epidemiological stratification and control program of the onchocerciasis in southern venezuela.
Homeopathic pathogenetic trial of Plumbum metallicum: the complete 2000 trial with a synthesis of the original 1828 trial  [cached]
Andrea Maria Signorini,Christa Pichler
International Journal of High Dilution Research , 2011,
Abstract: Background: in a previous paper we reported the statistical analysis and other distribution data of a homeopathic pathogenetic trial (HPT) of Plumbum metallicum 30cH carried out by our group. However, at that time we did not report the resulting pure materia medica, i.e., the totality of symptoms elicited by the tested medicine on healthy volunteers. Aim: to communicate to the homeopathic community the full record of symptoms collected in our HPT of Plb. Methods: methods to collect and select symptoms have been reported in the previous paper. In synthesis were excluded all previous common symptoms of volunteers, even with slight differences, and selected only those that were really unknown, never seen, unusual or very strange for the prover. In this paper special emphasis was given to new symptoms as well as unusual or repeated dreams, while in the previous paper special emphasis was given to repeated and crossed symptoms. Results: symptoms are reported in their chronological order of appearance in each volunteer. 37 new symptoms were found, useful to update Homeopathic Repertories. It is also included a synthesis of the original HPT of Plb carried out in 1828 in order to make available the full experimental materia medica currently existing. Conclusions: the new HPT, besides widening the pathogenetic picture of Plb (skin and mucosae symptoms), also allowed us to give new and deeper meanings to some of the symptoms reported in the original trial, such as Anxiety, Activity, Depression, Slowness, Gastro-oesophageal problems, Colitis. The dreams complete the remedy image, mainly in work, religion and sexual themes. Up to the present time there is no peer-reviewed publication devoted to HPTs. For this reason, researchers are compelled to publish HPTs as private editions. This results in poor control of the quality of publications and a lack of standards on how to present the results of HPTs.
Identification of the forest strain of Onchocerca volvulus using the polymerase chain reaction technique
B Adewale, MA Mafe, JPO Oyerinde
West African Journal of Medicine , 2005,
Abstract: Annual mass treatment with ivermectin for 12 – 15 years in endemic communities is the control strategy adopted by the African Programme for Onchocerciasis Control (APOC) for the control of onchocerciasis in Nigeria. This long-term treatment necessitates the use of Polymerase Chain Reaction (PCR) for the proper identification of the Onchocerca species and strains in endemic areas and also for monitoring recrudescence of infection in areas where infection has been controlled. This study, which forms part of a larger study on transmission of onchocerciasis identifies the Onchocerca volvulus strain in Ondo state using the Polymerase Chain Reaction (PCR) technique. Deoxyribonucleic acid (DNA) was extracted from the adult worm of Onchocerca parasite using the glass bead method of extraction. The repeated sequence family present in the genome of the parasite designated as 0-150bp was amplified by the polymerase chain reaction (PCR). The amplified parasites produced significant products visible as bands in a 2% agarose gel stained with ethidium bromide. Hybridization of the PCR products with specific DNA probe identified the products as forest strain of Onchocerca volvulus. The epidemiological implication of this is that there would be more of the skin lesions and low blindness rate in the area.
Elimination of Onchocerca volvulus Transmission in the Huehuetenango Focus of Guatemala  [PDF]
Nancy Cruz-Ortiz,Rodrigo J. Gonzalez,Kim A. Lindblade,Frank O. Richards Jr.,Mauricio Sauerbrey,Guillermo Zea-Flores,Alfredo Dominguez,Orlando Oliva,Eduardo Catú,Nidia Rizzo
Journal of Parasitology Research , 2012, DOI: 10.1155/2012/638429
Abstract: In Latin America, onchocerciasis is targeted for elimination by 2012 through twice-yearly mass treatment of the eligible population with ivermectin. In Guatemala, two of the four historical endemic foci have demonstrated elimination of transmission, following World Health Organization guidelines. Using established guidelines ophthalmological, serological, and entomological evaluations were conducted in 2007-8 to determine the transmission status of onchocerciasis in the Huehuetenango focus. The prevalence of Onchocerca volvulus microfilariae in the anterior segment of the eye in 365 residents was 0% (95% confidence interval [CI] 0–0.8%), the prevalence of infection of O. volvulus in Simulium ochraceum among 8252 flies collected between November 2007 and April 2008 was 0% (95% CI 0–0.02%), and the prevalence of antibodies to a recombinant O. volvulus antigen in 3118 school age children was 0% (95% CI 0–0.1%). These results showed transmission interruption; thus, in 2009 mass treatment was halted and posttreatment surveillance began. To verify for potential recrudescence an entomological evaluation (from December 2010 to April 2011) was conducted during the 2nd and 3rd year of posttreatment surveillance. A total of 4587 S. ochraceum were collected, and the prevalence of infection of O. volvulus was 0% (95% CI 0–0.04%). Transmission of onchocerciasis in the Huehuetenango focus has been eliminated. 1. Introduction Onchocerciasis is a vector-borne parasitic disease caused by infection with the filarial nematode Onchocerca volvulus and can result in eye or skin lesions. The parasite is transmitted to humans by certain black flies of the genus Simulium. Although adult worms can live for years under the skin in fibrous nodules that are often palpable, morbidity is caused by the body’s immune reaction to the microfilariae (mf) that leave the nodules and migrate through the skin and sometimes enter the eye [1]. In 2007, The World Health Organization (WHO) estimated 37 million persons were infected with onchocerciasis in 37 endemic countries (30 in Africa, six in the Americas, and one in the Arabian Peninsula) [2]. In the Americas there are 13 geographically isolated endemic foci found within Mexico, Guatemala, Colombia, Venezuela, Brazil, and Ecuador [3, 4] where 470,222 persons were at risk of infection in 2011 [5]. The Onchocerciasis Elimination Program of the Americas (OEPA) was established in 1992 in response to a resolution of the Directing Council of the Pan American Health Organization (PAHO) calling for the elimination of onchocerciasis ocular morbidity
Simukunin from the Salivary Glands of the Black Fly Simulium vittatum Inhibits Enzymes That Regulate Clotting and Inflammatory Responses  [PDF]
Hitoshi Tsujimoto, Michail Kotsyfakis, Ivo M. B. Francischetti, Jai Hoon Eum, Michael R. Strand, Donald E. Champagne
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029964
Abstract: Background Black flies (Diptera: Simuliidae) feed on blood, and are important vectors of Onchocerca volvulus, the etiolytic agent of River Blindness. Blood feeding depends on pharmacological properties of saliva, including anticoagulation, but the molecules responsible for this activity have not been well characterized. Methodology/Principal Findings Two Kunitz family proteins, SV-66 and SV-170, were identified in the sialome of the black fly Simulium vittatum. As Kunitz proteins are inhibitors of serine proteases, we hypothesized that SV-66 and/or ?170 were involved in the anticoagulant activity of black fly saliva. Our results indicated that recombinant (r) SV-66 but not rSV-170 inhibited plasma coagulation. Mutational analysis suggested that SV-66 is a canonical BPTI-like inhibitor. Functional assays indicated that rSV66 reduced the activity of ten serine proteases, including several involved in mammalian coagulation. rSV-66 most strongly inhibited the activity of Factor Xa, elastase, and cathepsin G, exhibited lesser inhibitory activity against Factor IXa, Factor XIa, and plasmin, and exhibited no activity against Factor XIIa and thrombin. Surface plasmon resonance studies indicated that rSV-66 bound with highest affinity to elastase (KD = 0.4 nM) and to the active site of FXa (KD = 3.07 nM). We propose the name “Simukunin” for this novel protein. Conclusions We conclude that Simukunin preferentially inhibits Factor Xa. The inhibition of elastase and cathepsin G further suggests this protein may modulate inflammation, which could potentially affect pathogen transmission.
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