Abstract
Studying the behaviour and trophic preferences of mosquitoes is an important step in understanding the exposure of vertebrate hosts to vector-borne diseases. In the case of human malaria, ...transmission increases when mosquitoes feed more on humans than on other animals. Therefore, understanding the spatio-temporal dynamics of vectors and their feeding preferences is essential for improving vector control measures. In this study, we investigated the feeding behaviour of
Anopheles
mosquitoes at two sites in the Sudanian areas of Senegal where transmission is low following the implementation of vector control measures. Blood-fed mosquitoes were collected monthly from July to November 2022 by pyrethrum spray catches in sleeping rooms of almost all houses in Dielmo and Ndiop villages, and blood meals were identified as from human, bovine, ovine, equine and chicken by ELISA. Species from the
An. gambiae
complex were identified by PCR. The types and numbers of potential domestic animal hosts were recorded in each village. The Human Blood Index (HBI) and the Manly Selection Ratio (MSR) were calculated to determine whether hosts were selected in proportion to their abundance. Spatio-temporal variation in HBI was examined using the Moran’s index. A total of 1251 endophilic
Anopheles
females were collected in 115 bedrooms, including 864 blood fed females of 6 species.
An. arabiensis
and
An. funestus
were predominant in Dielmo and Ndiop, respectively. Of the 864 blood meals tested, 853 gave a single host positive result mainly on bovine, equine, human, ovine and chicken in decreasing order in both villages. Overall, these hosts were not selected in proportion to their abundance. The human host was under-selected, highlighting a marked zoophily for the vectors. Over time and space, the HBI were low with no obvious trend, with higher and lower values observed in each of the five months at different points in each village. These results highlight the zoophilic and exophagic behaviour of malaria vectors. This behaviour is likely to be a consequence of the distribution and use of LLINs in both villages and may increase risk of residual outdoor transmission. This underlines the need to study the feeding host profile of outdoor resting populations and how domestic animals may influence malaria epidemiology in order to tailor effective malaria vector control strategies in the two villages.
Mechanical transmission of pathogens by biting insects is a non-specific phenomenon in which pathogens are transmitted from the blood of an infected host to another host during interrupted feeding of ...the insects. A large range of pathogens can be mechanically transmitted, e.g. hemoparasites, bacteria and viruses. Some pathogens are almost exclusively mechanically transmitted, while others are also cyclically transmitted. For agents transmitted both cyclically and mechanically (mixed transmission), such as certain African pathogenic trypanosomes, the relative impact of mechanical versus cyclical transmission is essentially unknown. We have developed a mathematical model of pathogen transmission by a defined insect population to evaluate the importance of mechanical transmission. Based on a series of experiments aimed at demonstrating mechanical transmission of African trypanosomes by tabanids, the main parameters of the model were either quantified (host parasitaemia, mean individual insect burden, initial prevalence of infection) or estimated (unknown parameters). This model allows us to simulate the evolution of pathogen prevalence under various predictive circumstances, including control measures and could be used to assess the risk of mechanical transmission under field conditions. If adjustments of parameters are provided, this model could be generalized to other pathogenic agents present in the blood of their hosts (Bovine Leukemia virus,
Anaplasma, etc.) or other biting insects such as biting muscids (stomoxyines) and hippoboscids.
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► Molecular characterization of Fasciola gigantica based on the first (ITS-1), the 5.8S, and second (ITS-2) Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA (rDNA) genes ...and the mitochondrial Cytochrome c Oxidase I (COI) gene. ► ITS sequences identical to the most frequent haplotypes of F. gigantica. ► Flukes scattered in pure F. gigantica clade. ► Close relationship with isolates of F. gigantica from Africa and Asia.
Fasciolosis caused by Fasciola hepatica and Fasciola gigantica (Platyhelminthes: Trematoda: Digenea) is considered the most important helminth infection of ruminants in tropical countries, causing considerable socioeconomic problems. From Africa, F. gigantica has been previously characterized from Burkina Faso, Senegal, Kenya, Zambia and Mali, while F. hepatica has been reported from Morocco and Tunisia, and both species have been observed from Ethiopia and Egypt on the basis of morphometric differences, while the use of molecular markers is necessary to distinguish exactly between species. Samples identified morphologically as F. gigantica (n=60) from sheep and cattle from different geographical localities of Mauritania were genetically characterized by sequences of the first (ITS-1), the 5.8S, and second (ITS-2) Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA (rDNA) genes and the mitochondrial Cytochrome c Oxidase I (COI) gene.
Comparison of the sequences of the Mauritanian samples with sequences of Fasciola spp. from GenBank confirmed that all samples belong to the species F. gigantica. The nucleotide sequencing of ITS rDNA of F. gigantica showed no nucleotide variation in the ITS-1, 5.8S, and ITS-2 rDNA sequences among all samples examined and those from Burkina Faso, Kenya, Egypt and Iran. The phylogenetic trees based on the ITS-1 and ITS-2 sequences showed a close relationship of the Mauritanian samples with isolates of F. gigantica from different localities of Africa and Asia. The COI genotypes of the Mauritanian specimens of F. gigantica had a high level of diversity, and they belonged to the F. gigantica phylogenically distinguishable clade. The present study is the first molecular characterization of F. gigantica in sheep and cattle from Mauritania, allowing a reliable approach for the genetic differentiation of Fasciola spp. and providing basis for further studies on liver flukes in the African countries.
An epidemiological study of Trypanosoma evansi (T. evansi) infection in dromedaries was conducted in four wilayate (localities) of Southern Algeria: Béchar, El Bayadh, Ouargla, Tamanrasset. Between ...February 2014 and April 2016, 1056 camels of different ages and both sexes from 84 herds were sampled. The prevalence was determined through parasitological examination (Giemsa stained thin smear, GST), serological tests (CATT/T. evansi, ELISA/VSG RoTat 1.2, immune trypanolysis), and molecular tests (T. evansi type A specific RoTat 1.2 PCR and T. evansi type B specific EVAB PCR).
The overall prevalence was 2.4 % with GST, 32.4% with CATT/T. evansi, 23.1% with ELISA/VSG RoTat 1.2, 21.0% with immune trypanolysis (TL), 11.2 % with RoTat 1.2 PCR and 0% with EVAB PCR.
El Bayadh was the most affected wilaya with 11.8% positives in GST, 74.9% in CATT/T. evansi, 70.1% in ELISA/VSG RoTat 1.2 and 62.2% in immune trypanolysis. Only in Béchar, a non-significantly higher prevalence (13.6%) was observed with RoTat1.2 PCR than in El Bayadh (13.0%). We didn't find any evidence of the presence of T. evansi type B in the study area.
L’hépatite virale B constitue un problème majeur de santé publique en Afrique subsaharienne avec environ 65 millions de porteurs chroniques et 56.000 décès par an. Notre étude avait pour but ...d’étudier les aspects épidémiologiques, paracliniques, thérapeutiques, évolutifs des patients atteints d’hépatite virale B suivis dans notre service et de décrire leurs profils sérologiques. Nous avons réalisé une étude rétrospective, longitudinale de 2010 à 2014 dans le service d’hépato gastroentérologie de l’hôpital Aristide Le Dantec de Dakar. Nous avons inclus tous les patients suivis en ambulatoire ou hospitalisés qui avaient une positivité de l’AgHBs. Nous avons colligé 728 cas de patients infectés par le virus de l’hépatite B. Ils étaient constitués de 7 cas d’hépatite aiguë, de 442 cas d’infections chroniques, de 161 cirrhotiques et de 118 cas de carcinome hépatocellulaire. L’âge moyen était de 33 ans 14 - 83 ans avec un sex-ratio de 2,2. Les circonstances de découverte étaient représentées par le dépistage systématique (26,2%), les douleurs de l’hypochondre droit (23%) et le don de sang (18,6%). Il y avait 59 patients monoinfectés par le virus de l’hépatite B qui étaient au stade d’hépatite chronique active. Les porteurs inactifs étaient au nombre de 118. Par insuffisance d’exploration liée à des contraintes économiques, le statut sérologique était indéterminé chez 252 patients. Un traitement antiviral B n’a pu être institué que chez 58 patients. Sous Ténofovir, la réponse virologique et biochimique était respectivement de 85% et 100% après 120 semaines de traitement. Le virus de l’hépatite B est une cause majeure d’hépatopathie au Sénégal.
L’objectif de cette étude est d’évaluer les anomalies électrocardiographiques et échocardiographiques chez les patients atteints de cirrhose virale B et identifier leurs déterminants. Il s’agissait ...d’une étude prospective sur 8 mois aux services de d’Hépato-Gastroentérologie et de Cardiologie de l’hôpital Aristide Le Dantec de Dakar. Tous les patients atteints de cirrhose B virale et n’ayant pas de cardiopathie pré existante connue ont été inclus. Nous avons collecté et analysé les données épidémiologiques, cliniques, biologiques, échographiques, endoscopiques, électrocardiographiques et échocardiographiques (2D et Doppler) de tous les patients. Les données ont été saisies sur tableau Excel 2007 et analysées à l’aide du logiciel Sphinx version 5. La comparaison des variables a été faite par les tests de Chi 2 standard et Fisher. Le seuil de significativité a été arrêté à p< 0,05 pour ces 2 tests statistiques. Soixante patients ont été inclus. La prévalence de la cirrhose virale B était de 3,4%. L’âge moyen était de 41 ans et le sex ratio de 1,6 (37 hommes). La cirrhose était classée Child-Pugh B chez 29 patients (49%), Child-Pugh C et Child Pugh A respectivement chez 20 patients (33%) et 11 patients (18%). Les anomalies électrocardiographiques les plus fréquentes étaient l’hypertrophie ventriculaire gauche et l’allongement de l’intervalle QTc objectivés respectivement chez 27 patients (45%) et 24 patients (40%). L’analyse statistique a montré une association entre l’intervalle QTc prolongé et la gravité de la cirrhose (p = 0,01, RR = 2, IC = 0,24 à 0,341). Les anomalies échocardiographiques étaient dominées par la dilatation ventriculaire gauche (58,3%) et l’hyperdébit cardiaque (43,3%) avec un débit moyen de 6,05 l/min. L’analyse stastistique mettait en évidence une association significative entre la gravité de la cirrhose et l’hyperdébit cardiaque (p = 0,003; IC: 95% (de 2,883 à 38,58; RR = 2). Au total, 14 patients (23,3%) avaient une cardiomyopathie cirrhotique latente. La cirrhose virale B peut induire des anomalies cardiaques diverses et variées. Ces anomalies sont morphologiques et/ou électrophysiologiques et leur gravité semble corrélée à la sévérité de la cirrhose.
Une cause inhabituelle d’ictère Diallo Salamata; Boundia, Djiba; Bassène, Marie Louise ...
The Pan African medical journal,
2018, Letnik:
31, Številka:
72
Journal Article
Recenzirano
Odprti dostop
L'atteinte hépatique est fréquente au cours de l'hyperthyroïdie. Elle est le plus souvent asymptomatique. Une hyperthyroïdie révélée par un ictère est rarement décrite dans littérature. Nous vous ...rapportons une observation à Dakar (Sénégal). Il s'agissait d'un patient de 52 ans qui avait consulté notre service pour un ictère associé à un prurit. Les explorations biologiques montraient une augmentation des alanine aminotranférases (1,1 N), des aspartate aminotranférases (1,5 N), des phosphatases alcalines (3 N), des gamma glutamyl transférases (1,3 N) et de la bilirubinémie (22 N). L'échographie abdominale était normale. Une cause toxique ou médicamenteuse, un obstacle sur les voies biliaires, une hépatite virale ou auto immune ainsi qu'une cholangite biliaire primitive ont été exclu. Le dosage des hormones thyroïdiennes montrait une élévation de la T4 libre à 24 ng/dL (9-20 ng/dL) et un taux plasmatique indétectable de TSH inférieure à 0,01μUI/mL (0,35-4,94 UI/mL). Les anticorps anti récepteurs de la TSH étaient positifs à 7,04 UI/L (N < 1,75 UI/L). L'échographie thyroïdienne objectivait un goitre diffus homogène hypervasculaire. Le diagnostic d'une atteinte hépatique secondaire à une maladie de Basedow sans dysfonction cardiaque était retenu. L'évolution clinique et biologique était favorable sous carbimazole. L'ictère peut être révélatrice d'une hyperthyroïdie. La recherche des signes cliniques et biologiques d'une hyperthyroïdie est obligatoire devant un ictère inexpliqué.
The role of mechanical vectors in the transmission of African livestock trypanosomes has always been controversial relative to tsetse flies, their cyclical vectors. An experiment was carried out in ...Burkina Faso to demonstrate mechanical transmission of
Trypanosoma vivax by one of the most common tabanids in Africa:
Atylotus agrestis. Eight heifers (crossbred zebu
×
Baoulé), free of trypanosome infection, were kept in a corral covered by a mosquito net, together with two heifers infected experimentally with a local stock of
T. vivax. On average, 324
A. agrestis, freshly captured with Nzi traps, were introduced daily over 20 days. Parasitological, PCR and serological examinations were carried out regularly to assess infections and levels of parasitaemia. Microscopic examination of buffy-coats indicated that five of the eight receiver-heifers were infected on days 8, 13, 32, 41, and 48. PCR results indicated that these five heifers were already infected by day 13. Mechanical transmission of
T. vivax by
A. agrestis was demonstrated unequivocally, at a high rate (63% in 13–20 days). Conditions of transmission in this experiment are discussed in terms of natural rates of challenge. The importance of tabanids as mechanical vectors of
T. vivax should be re-considered, in light of these results. Creation of tsetse free zones in Africa will generally lead to the disappearance of
T. congolense,
T. brucei, and most often
T. vivax as well; however, in areas where
T. vivax can be mechanically transmitted, clearance of tsetse may not be sufficient to eradicate livestock trypanosomosis.
Index Descriptor and Abbreviations: Trypanosoma vivax (Trypanosomatidae) is a pathogenic trypanosome found in wild and domestic herbivores, principally in cattle (
Bos taurus,
Bos indicus, and crossbreeds), in South America and Africa. In Africa it is principally cyclically transmitted by tsetse flies (
Diptera). In America it is only mechanically transmitted by tabanids (Tabanidae). The present paper describes the mechanical transmission of
T. vivax in cattle by one of the most common African tabanids:
A. agrestis. The main conclusion is that not only tsetse can transmit
T. vivax in Africa, consequently the epidemiology of trypanosomosis in cattle is also tabanid dependant, and, the eradication of tsetse flies will not necessarily lead to eradication of
T. vivax. ADT, Apparent density of insects per trap per day (mean number of insects caught in one type of trap per 24
h of trapping); PATTEC, Pan African Tsetse and Trypanosomiasis Eradication Campaign; RHD, rate of hematocrit decrease; D, day; ELISA, enzyme linked immunosorbent assay; NS, not significant (in terms of statistics); PCR, polymerase chain reaction
The inventory of tabanids of Ivory Coast includes both a review of historical datasets as well as the results of recent targeted field investigations in the North of Ivory Coast from 2000 to 2002 and ...Banco forest in 2012. The family Tabanidae known as horse flies has been estimated to consist of 4,500 existing species throughout the world. Four genera are known to be of medico-veterinary importance and include: Haematopota, Tabanus, Atylotus and Chrysops. The documented results of 28 sites provide significant information to update on the Tabanidae list of Ivory Coast. 70 species and 14 genera have been identified till date such as genus Tabanus with 40 species (57.14 %), genus Haematopota with 10 species (14.29 %), genera Atylotus, Chrysops and Hippocentrum with three species (4.29 %), genera Ancala, Rhigioglossa with two species (2.86%). Seven genera with only one species identified. T. taeniola, T. besti, T. secedens, T. thoracinus, H. decora, H. griseicoxa and H. torquens were captured in at least five regions.
The trypanosomes pathogenic to livestock in Africa (
Trypanosoma congolense,
Trypanosoma vivax, and
Trypanosoma brucei) are mainly cyclically transmitted by tsetse (
Glossina). However,
T. vivax, can ...also be mechanically transmitted by haematophagous insects. Laboratory studies have demonstrated the mechanical transmission of
T. congolense, but confirmation of this under natural conditions was necessary. An experiment was therefore carried out in Lahirasso, Burkina Faso, in a corral completely covered by mosquito net, to avoid exposure to tsetse. Eight receiver heifers, free of trypanosome infection, were kept together with two donor heifers, experimentally infected with local stocks of
T. congolense. On average, 291
Atylotus agrestis, freshly captured in Nzi traps, were introduced into the mosquito net daily for a period of 20 days to initiate mechanical transmission among cattle. Daily microscopical observation of their blood indicated that two of the eight receiver heifers became infected with
T. congolense from days 42 and 53. Mechanical transmission of
T. congolense by
A. agrestis was demonstrated unequivocally with a 25% incidence over a 20-day period of exposure under a mean challenge of 29 insects/animal/day. These results, in addition to previous reports, demonstrate the ability of
A. agrestis to transmit
T. vivax and
T. congolense to cattle in Africa by mechanical means. Efforts to eliminate cattle trypanosomosis should therefore consider the eventual persistence of disease as a result of mechanical transmission of trypanosomes by tabanids.
Index descriptor and abbreviations: Trypanosoma congolense (
Trypanosomatidae) is a pathogenic trypanosome found in wild and domestic herbivores, principally in cattle (
Bos taurus,
Bos indicus, and cross-breds), in Africa. It is cyclically transmitted by tsetse (
Glossina, Diptera); however, mechanical transmission by biting insects may also occur. The present study demonstrates unequivocally the mechanical transmission of
T. congolense to cattle by one of the most common African tabanids,
A. agrestis. The main conclusion is that tabanids are able to transmit
T. congolense; however, the incidence of transmission was lower than in studies carried out under the same conditions with
T. vivax. Better models of mechanical transmission are required to understand why, on the one hand, epidemiological studies support the mechanical transmission of
T. vivax but not
T. congolense, and, on the other hand, experimental studies confirm that both species can be mechanically transmitted. Our studies suggest that the epidemiology of trypanosomosis in cattle involves tabanids, and hence, the eradication of tsetse-flies in Africa will not necessarily lead to the eradication of trypanosomosis in domestic livestock. ADT, apparent density of insects per trap per day (mean number of insects caught in one type of trap per 24
h of trapping); D, day; NS, not statistically significant
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