THE CHANGING NATURE OF UK FISH RETAILING

Resource /Energy Economics and Policy,

LONG-RUN STRIGA CONTROL BY SUBSISTENCE FARMERS IN MALI

A dynamic programming model is developed to identify barriers to the adoption of long-run control programs for the parasitic weed Striga. The model is applied to Sirakorola in northwestern Mali. The ability of national and village-level institutions to overcome the barriers to adoption is explored.Community/Rural/Urban Development, Research and Development/Tech Change/Emerging Technologies,

Characterization of maize producing households in the dry savanna of Mali

Maize is one of the three most important staple foods in Mali. Zones in the country with high potential for producing maize are limited to areas where the probability of drought risk is between 20 and 40%, meaning that recurring droughts have long handicapped maize production. In an attempt to alleviate drought stress on maize production, a household survey was conducted in the two Local Government Areas of Bougouni and Koutiala, both in the Sikasso Region, during the 2007/2008 production period. These two districts were selected following an environmental characterization of drought zones in Mali. The survey was mainly oriented towards maize based farming systems. Six sample villages were selected within each of the two districts. The sample population was defined as maize farming households. A total of 150 households were randomly selected and interviewed with structured questionnaires. Interviews were conducted by trained enumerators using a formal household survey. The purpose of the study is to provide both quantitative and qualitative feedback from farmers to researchers and to the B&MGF on the impact that improved maize varieties developed in the past have had upon the livelihoods of households and to provide a detailed database for the projection of expected outcomes with the deployment of new drought tolerant maize varieties under the B&MGF drought tolerant maize project. Both qualitative and quantitative analyses were used to extract from our set of variables those orthogonal linear combinations of the variables that best captured the common information. Most successful was the one proposed by Filmer and Pritchett (1998; 2001) called the Principal Component Analysis (PCA). To assess the variables affecting the adoption of improved maize varieties, the Tobit model was used. The results show that 99% of household heads are male. The size of a household is 22 persons, on average. About 47% of the household’s members are available for farm work. About 59% of household heads are illiterate, an important factor concerning the adoption of new technology. These household heads make decisions about 84% of farming activities; 86% of the households involved in the study belonged to at least one farmers’ organization in order to have easy access to inputs

Hepatitis C virus cell-cell transmission and resistance to direct-acting antiviral agents

Hepatitis C virus (HCV) is transmitted between hepatocytes via classical cell entry but also uses direct cell-cell transfer to infect neighboring hepatocytes. Viral cell-cell transmission has been shown to play an important role in viral persistence allowing evasion from neutralizing antibodies. In contrast, the role of HCV cell-cell transmission for antiviral resistance is unknown. Aiming to address this question we investigated the phenotype of HCV strains exhibiting resistance to direct-acting antivirals (DAAs) in state-of-the-art model systems for cell-cell transmission and spread. Using HCV genotype 2 as a model virus, we show that cell-cell transmission is the main route of viral spread of DAA-resistant HCV. Cell-cell transmission of DAA-resistant viruses results in viral persistence and thus hampers viral eradication. We also show that blocking cell-cell transmission using host-targeting entry inhibitors (HTEIs) was highly effective in inhibiting viral dissemination of resistant genotype 2 viruses. Combining HTEIs with DAAs prevented antiviral resistance and led to rapid elimination of the virus in cell culture model. In conclusion, our work provides evidence that cell-cell transmission plays an important role in dissemination and maintenance of resistant variants in cell culture models. Blocking virus cell-cell transmission prevents emergence of drug resistance in persistent viral infection including resistance to HCV DAAs

Laboratory study of the biology and behaviour of Diplonychus sp (Belostomatidae) and its vector competence in the transmission to humans of Mycobacterium ulcerans, the pathogen causing Buruli ulcer in Côte d’Ivoire (West Africa).

Buruli ulcer is a skin infection caused by a mycobacterium occurring in the environment, Mycobacterium ulcerans.  Ranked third in terms of number of mycobacterial infections after leprosy and tuberculosis, its epidemiology is the most poorly understood of the three. Humans are infected through the skin while performing daily living activities (e.g. rice cultivation, fish farming, fishing, laundry, fetching water, agricultural work) or leisure activities (e.g. bathing) in endemic areas. The disease is particularly prevalent in West Africa, where the number of cases is increasing annually (2442 cases in 2008). Côte d’Ivoire is the most severely affected country in the world with more than 25 000 cases since 1978. The numerous endemic foci for Buruli ulcer are scattered throughout the country. Over the past four years impressive progress has been made in researching the mode of transmission of M. ulcerans infection. Yet despite this, many questions remain unanswered. In Central and West Africa aquatic insects of the order Hemiptera appear to be involved in the transmission of Buruli ulcer.  It is likely that aquatic Hemiptera play a role.  Studies of the salivary glands of insects that have been experimentally infected and allowed to bite white mice demonstrate the probable role of water bugs as hosts or possible vectors of M. ulcerans. In addition, at least 10% of environmental biological specimens tested positive using PCR in Cameroon and Côte d’Ivoire. These pterygot insects are also able to fly from one body of water to another over varying distances, attracted by lights in houses near marshy areas. This method of displacement could account for the current progression of the disease in West Africa and particularly in Côte d’Ivoire, where it is spreading northwards from the south, west, east and centre of the country.   Buruli ulcer is not a contagious disease.  It is, however, terrifying and severely disabling.  Patients must spend long periods in hospital, treatment is costly and burdensome, and can lead to social marginalization or even total exclusion; above all, the mode of transmission is still poorly understood.  Local people must therefore be familiarized with preventive measures focusing on identification of the probable vectors of the disease in order to break the chain of transmission of M. ulcerans. This presupposes a sound knowledge of the biology, ecology and behaviour of these potential vectors. Accordingly, we have proceeded to laboratory farm the bug most commonly encountered in the environment that shows the highest rates of infection by M. ulcerans (more than 10%), namely Diplonychus sp of the family Belostomatidae. Adult specimens were collected in the vicinity of fishponds at an experimental station situated between Abidjan and Dabou (a non-endemic site) and subsequently farmed in the laboratory at the Côte d’Ivoire National Institute of Public Health. The parameters used to farm this water bug were standardized in the laboratory (water quality, depth, turbidity, pH, temperature, luminosity, suitable vegetable environment). The insects were fed regularly with mosquito larvae. The embryonic lifespan, the hatching time, the larval period and the number of larval stages prior to adulthood were studied. The adult lifespan was also estimated. Five successive generations of Diplonychus sp were obtained. From egg to adulthood, the larval lifespan is 41 days on average, with deviations from the mean of 29 to 54 days.  Hatching generally took place 7 days after egg laying.  Five larval stages are distinguishable, separated by five metamorphoses.  The lifespan of certain adults obtained in the laboratory varied between 16 and 150 days.  The last original parental specimens survived for 11 months.  Proficiency in the laboratory farming of Diplonychus sp could enable us to decode its genome and collect saliva samples, while also allowing us to perform experimental infections using human strains of M. ulcerans in order to confirm or rule out the involvement of this insect in the transmission of Buruli ulcer in Central and West Africa

Species-Specific Activity of HIV-1 Vpu and Positive Selection of Tetherin Transmembrane Domain Variants

Tetherin/BST-2/CD317 is a recently identified antiviral protein that blocks the release of nascent retrovirus, and other virus, particles from infected cells. An HIV-1 accessory protein, Vpu, acts as an antagonist of tetherin. Here, we show that positive selection is evident in primate tetherin sequences and that HIV-1 Vpu appears to have specifically adapted to antagonize variants of tetherin found in humans and chimpanzees. Tetherin variants found in rhesus macaques (rh), African green monkeys (agm) and mice were able to inhibit HIV-1 particle release, but were resistant to antagonism by HIV-1 Vpu. Notably, reciprocal exchange of transmembrane domains between human and monkey tetherins conferred sensitivity and resistance to Vpu, identifying this protein domain as a critical determinant of Vpu function. Indeed, differences between hu-tetherin and rh-tetherin at several positions in the transmembrane domain affected sensitivity to antagonism by Vpu. Two alterations in the hu-tetherin transmembrane domain, that correspond to differences found in rh- and agm-tetherin proteins, were sufficient to render hu-tetherin completely resistant to HIV-1 Vpu. Interestingly, transmembrane and cytoplasmic domain sequences in primate tetherins exhibit variation at numerous codons that is likely the result of positive selection, and some of these changes coincide with determinants of HIV-1 Vpu sensitivity. Overall, these data indicate that tetherin could impose a barrier to viral zoonosis as a consequence of positive selection that has been driven by ancient viral antagonists, and that the HIV-1 Vpu protein has specialized to target the transmembrane domains found in human/chimpanzee tetherin proteins

Entomological investigations carried out from 2002 to 2010 into the involvement of water bugs (Heteroptera - Hemiptera) in transmission of Mycobacterium ulcerans to humans in Côte d’Ivoire (West Africa)

Ulcer is a disease caused by a mycobacterium present in the environment: Mycobacterium ulcerans.This communicable disease occurs essentially in wet tropical regions, and in particular in west Africa where it is endemic. It is the third most common mycobacterial disease affecting humans after leprosy and tuberculosis, although it is more prevalent than either leprosy or tuberculosis in some rural areas of several countries (Benin, Côte d’Ivoire and Ghana). This has led WHO to act, and in 1998 to declare Buruli ulcer an « emerging disease » and to recognize it as a neglected tropical disease. Its development is a source of concern in Côte d’Ivoire, the country most affected in the world, with an aggregate number of 30 000 cases and more than 2000 cases detected each year. It particularly affects children living in isolated rural areas around bodies of stagnant or slowly flowing water.  In order to control the disease, it is essential fully to understand its epidemiology. In this connection, there are several hypotheses on the mode of transmission of M. ulcerans to humans. Since 1999, the involvement of water bugs belonging to the order of the hemiptera has been invoked by Portaels. In 2002, this hypothesis was confirmed by Marsollier et al. for water bugs of the genus Naucoris taken from the region of Daloa in Côte d’Ivoire, where the disease is endemic. In 2008, Portaels also found M. ulcerans in samples taken from the environment (Gerridae) in Ghana. In 2007, studies began in Côte d’Ivoire into the specific diversity, biology, ecology, ethology and role of aquatic heteroptera in the transmission of M. ulcerans to humans. Samples of aquatic heteroptera were collected each month from different aquatic environments in endemic areas of Côte d’Ivoire. The insects were identified by family, genus and occasionally species. Their distribution, population dynamics and ecological distribution in the water points investigated were correlated with human activities. Monospecific batches of water bugs were regularly composed in order to identify the molecular signatures of M. ulcerans using PCR at the bacteriology laboratory of the Institut Pasteur in Côte d’Ivoire and at the bacteriology laboratory of the Groupe d’Etudes des Interactions Hôtes-Pathogènes (Host-Pathogen Study Group) at the University Teaching hospital in Angers, France. Eighteen (18) species belonging to 8 families were identified. After the aquatic insects collected had been identified, 283 monospecific batches were composed and sent to the Institut Pasteur in Côte d’Ivoire (IPCI) for PCR. Twenty four (24) of the 283 batches i.e. 8,5% containing the following, 14 Diplonychus sp, 2 Naucoris sp, 3 Micronecta sp, 2 Ranatra fusca, 2 Anisops sp and 1 Laccotrephes ater, respectively belonging to the families Belostomatidae, Naucoridae, Corixidae, Ranatridae and Nepidae tested positive under PCR. Thirty five (35) samples of saliva were collected from specimens of the genus Diplonychus. Six of the samples (i.e. 17%) tested positive under PCR. Out of 109 other monospecific batches sent to the laboratory in Angers, France, 33 (i.e. 30%) tested positive under PCR. They comprised 11 batches of Diplonychus sp (Belostomatidae), 8 batches of Micronecta sp (Corixidae), 2 batches of Laccocoris sp (Naucoridae), 4 batches of Ranatra fusca (Ranatridae), 3 batches of Anisops sp, 1 lot de Anisops sardea et 1 lot de Enithares sp (Notonectidae), 2 batches of Plea pullula (Pleidae) and 1 batch of de Laccotrephes sp (Nepidae). Clearly, not only is Diplonychus sp the genus most commonly found, it is also that most affected by M. ulcerans. This justifies the decision to breed this genus in the laboratory since 2008, in order to improve our understanding of its biology and ethology and to standardize physical and chemical parameters so as to determine the best conditions for breeding the insect which would provide an animal model for experimental infections. We have now bred six successive generations in the laboratory. To conclude, although some aquatic heteroptera that host M. ulcerans are strictly phytophagous, (e.g. the Corixidae), the great majority of water bugs are carnivorous predators that are hosts and vectors of M. ulcerans. The absence of a reliable key for determining the family, genus and species in central and west Africa has led us to draw up an iconographic catalogue to determine the taxonomy of these insects

Yield loss of Oryza glaberrima caused by grain shattering under rainfed upland conditions

The general perception of Oryza glaberrima as low yielding is a potential drawback to intraspecific breeding of this species. Yields of 21 O. glaberrima accessions were evaluated alongside four O. sativa check varieties under two conditions in which panicles were both covered by paper sacks to avoid grain shattering (potential yield plot) and also not covered (control plot) in a rainfed upland field of Benin in 2010 and 2011. Average potential yields of O. glaberrima with panicles covered were 2.42 and 3.65 t ha-1 in 2010 and 2011, respectively, while those of O. sativa were respectively 2.99 and 3.49 t ha-1. Although there was no significant difference between potential yield and control yield in O. sativa, 19 O. glaberrima accessions showed significant yield reduction by grain shattering — the average percentages of lost yield by shattering were 57.88% in 2010 and 66.76% in 2011. These results suggest that low yield of O. glaberrima is due to grain shattering and that its potential yield would not be inferior to O. sativa if the grain shattering problems were overcome. Two O. glaberrima accessions, TOG 12303 and TOG 9300, possessing strong resistance to grain shattering comparable to O. sativa checks, were identified.Keywords: Panicles, paper sacks, potential yield, yield reduction