The population genetics of clonal and partially clonal diploids.

The consequences of variable rates of clonal reproduction on the population genetics of neutral markers are explored in diploid organisms within a subdivided population (island model). We use both analytical and stochastic simulation approaches. High rates of clonal reproduction will positively affect heterozygosity. As a consequence, nearly twice as many alleles per locus can be maintained and population differentiation estimated as F(ST) value is strongly decreased in purely clonal populations as compared to purely sexual ones. With increasing clonal reproduction, effective population size first slowly increases and then points toward extreme values when the reproductive system tends toward strict clonality. This reflects the fact that polymorphism is protected within individuals due to fixed heterozygosity. Contrarily, genotypic diversity smoothly decreases with increasing rates of clonal reproduction. Asexual populations thus maintain higher genetic diversity at each single locus but a lower number of different genotypes. Mixed clonal/sexual reproduction is nearly indistinguishable from strict sexual reproduction as long as the proportion of clonal reproduction is not strongly predominant for all quantities investigated, except for genotypic diversities (both at individual loci and over multiple loci)

The Alarming Proximity of Parasites

Compte-rendu de l'ouvrage d'Eugene Kaplan What’s Eating You? Princeton, NJ: Princeton University Press. 320p. ISBN 978-0-691-14140-

Initiation

La compréhension de l'épidémiologie d'une maladie infectieuse ou parasitaire passe par une connaissance minimale du fonctionnement des populations vivantes concernées. Ainsi, pour remédier à la difficulté d'obtenir des observations directes sur la biologie des populations naturelles, notamment dans les pays du Sud, l'utilisation de marqueurs génétiques permet d'avoir accès, à travers des méthodes indirectes, à des informations clés sur la biologie des agents pathogènes et de leurs vecteurs : écologie, mode de reproduction, déplacements, taille des populations, etc. Un outil précieux dans le domaine de la santé, où l'analyse de la variation spatio-temporelle des marqueurs génétiques peut ainsi être utilisée pour caractériser la dynamique des populations de parasites et de leurs vecteurs, pour connaître l'évolution d'une maladie infectieuse ou parasitaire, évaluer les risques d'invasions ou d'épidémie, le potentiel de diffusion de gènes résistants, anticiper les stratégies de lutte… Ce manuel didactique présente les principales méthodes de la génétique des populations naturelles et les modèles de base utilisés pour les inférences, avec des cas concrets d'applications à destination des étudiants et personnels de santé. Plusieurs jeux de données sont analysés pas à pas dans un CD-ROM qui accompagne l'ouvrage

Decrease in survival and fecundity of Glossina palpalis gambiensis vanderplank 1949 (Diptera : Glossinidae) fed on cattle treated with single doses of ivermectin

Background: Human and Animal Trypanosomes are major problems for the socio-economic growth of developing countries like Burkina Faso. Ivermectin is currently used to treat humans in mass drug administration programs in Africa, and is also commonly used for veterinary purposes. In this study, we tested the effect of ivermectin injected into cattle on the survival and fecundity of Glossina palpalis gambiensis, the main vector of human and animal trypanosomes in West Africa. Methods: Three cows (local zebu*baoule crossbreds) were used, and received either no ivermectin (for the control), or ivermectin at therapeutic dose (0.2 mg/kg) and 10 times the therapeutic dose (2 mg/kg) respectively. G. palpalis gambiensis were fed on the cattle for their first bloodmeal, and then either on cattle or on membrane for subsequent meals. Results: Our results showed that survival of Glossina palpalis gambiensis was significantly decreased when they were fed on cattle treated with ivermectin. This decrease in survival ranged from 21% to 83.7% for the therapeutic dose (0.2 mg/kg), up to 8 days after treatment. The effects of a dose of 2 mg/kg were higher with a 78.3% to 93.9% decrease in survival, until 14 days after injection. The therapeutic dose of ivermectin also decreased fecundity, and delayed the first larviposition, but there was no significant effect on hatching rate. Conclusion: Ivermectin injected into cattle may constitute an additional potential tool for the control of Glossina palpalis gambiensis and possibly other vector species. Further studies will be needed to assess its effect on trypanosome transmission, and to define more precisely the adequate dose to be used for control purposes

Effects of training on equine muscle physiology and muscle adaptations in response to different training approaches

It is well known that exercise induces chemical, metabolic and structural changes in muscles. However, the effect of the type of exercise on these changes has not been thoroughly studied in horses yet, because of a lack of standardized study methods. In this review, the effect of three different types of exercise on muscle adaptation and metabolic responses is investigated. The requirements for power exercise are not the same as for low intensity exercise. Each type of training induces its own shift in muscle fiber typing, as well as in enzyme concentrations and (an) aerobic capacity. These physiological adaptations in response to training facilitate more efficient exercise and therefore increase performance. Hence, it is important to know the adaptations that muscles undergo in response to each type of exercise to optimize training management of sport horses in function of the needs of the discipline in which they compete

Substrate use in horses during exercise : the 'fasted' compared to the postprandial state

Training in the fasted state has beneficial effects on performance in the human athlete. In the horse, training in the fasted state is associated with an increased mobilization of non-esterified fatty acids (NEFA) as an energy source. This is in contrast with postprandial (grain-fed) training, during which lipolysis is suppressed. A higher NEFA availability is thought to reduce muscle glycogen depletion and muscle acidification. This could aid in delaying muscle fatigue. The equine gastrointestinal tract and roughage rich diet do not allow a real 'fasted' state. Luckily, roughage does not induce high plasma insulin peaks, and therefore does not have the same negative effects as grain feeding. Furthermore, the roughage-containing hindgut serves as a fluid and electrolyte buffer and continuously provides the liver with propionic acid, a precursor used in gluconeogenesis. In horses, unlike in human athletes, there is still a lot to discover when it comes to optimal pre-exercise feeding management throughout competition and training. However, whatever approach is chosen, high quality roughage needs to be the key ingredient of the equine diet. In sport horses with high energy demands, feeding good quality roughage may be combined with fibre rich concentrates, pelleted roughages sources or vegetal oil instead of starch rich concentrates to reach the energy requirements for intensive work. Last but not least, feeding multiple small meals throughout the day is preferred over feeding a larger meal twice a day