The impact of host species and vector control measures on the fitness of African malaria vectors

Many malaria vector mosquitoes in Africa have an extreme preference for feeding on humans. This specialization allows them to sustain much higher levels of transmission than elsewhere, but there is little understanding of the evolutionary forces that drive this behaviour. In Tanzania, we used a semi-field system to test whether the well-documented preferences of the vectors An. arabiensis and An. gambiae s.s. for cattle and humans respectively are predicted by the fitness they obtain from host-seeking on these species relative to other available hosts. Mosquito fitness was contrasted when humans were fully exposed, and when they were protected by a typical bednet. The fitness of both vectors varied between host species. The predicted relationship between host preference and fitness was confirmed in An. arabiensis, but not in An. gambiae s.s. whose fitness was similar on humans and other mammals. Use of typical, imperfect bednets generated only minor reductions in An. gambiae s.s. feeding success and fitness on humans, but was predicted to generate a significant reduction in the lifetime reproductive success of An. arabiensis on human relative to cows. This supports the hypothesis that such human-protective measures could additionally benefit malaria control by increasing selection for zoophily in vectors

The role of SMAD4 in early-onset colorectal cancer

Objective: Chromosomal loss within the region of 18q and loss of SMAD4 expression have been reported to be frequent somatic events during colorectal cancer tumour progression; however, their associations with age at onset have not been widely studied.\ud \ud Method: We analysed 109 tumours from a population-based case-family study based on colorectal cancers diagnosed before the age of 45 years. These patients with early-onset colorectal cancer had been previously screened for germ-line mismatch repair gene mutations, microsatellite instability (that included the mononucleotide repeat in TGFβRII) and somatic k-ras mutations. We measured SMAD4 protein expression using immunohistochemistry and SMAD4 copy number using quantitative real-time PCR.\ud \ud Results: Loss of SMAD4 protein expression was observed in 27/109 (25%) of cancers tested and was more commonly observed in rectal tumours (15/41, 36%) when compared with tumours arising in the colon (11/66, 17%) (P = 0.04). There was no association between SMAD4 protein expression and TGFβR11 mutation status, SMAD4 copy number, family history, MSI status, tumour stage or grade.\ud \ud Conclusion: Loss of SMAD4 expression is a common feature of early-onset colorectal tumours as it is in colorectal cancers diagnosed in other age-groups. Taken together, the molecular pathways (genetic and epigenetic) now known to be involved in early-onset colorectal cancer only explain a small proportion of the disease and require further exploration

Urban domestic dog populations as a source of canine distemper virus for wild carnivores in the Coquimbo region of Chile

Urban areas can support dog populations dense enough to maintain canine distemper virus (CDV) and can be a source of infection for rural dogs and free-ranging carnivores. The aim of this study was to investigate the relationships between urban and rural domestic dog and wild carnivore populations and their effects on the epidemiology of CDV to explain retrospectively a CD outbreak in wild foxes in 2003. From 2005 to 2007 a cross-sectional household questionnaire survey was conducted in Coquimbo and Ovalle cities, in three towns and in rural sites along two transects from these cities to the Fray Jorge National Park (FJNP) in the Coquimbo region, Chile. Blood samples were collected from unvaccinated dogs at surveyed households and from free-ranging foxes in rural areas along the transects. The seroprevalence of CDV in domestic dogs was higher in urban than in rural areas and in the later was highest in dogs born before 2001-2002. The seroprevalence of CDV in foxes was higher in areas closer to human settlements. A high seroprevalence in dogs born before 2001-2002 further supports a link between CDV patterns in rural dog and fox populations. In our study area, urban dogs are proposed to be the source of CDV infection to wild carnivores. The large dog population size and density detected in Coquimbo and Ovalle provides optimal conditions for maintaining a large and dense susceptible population of dogs, which can act as a reservoir for highly infectious diseases and could have been the source of infection in the CD outbreak in wild foxe

Qualidade da carcaça de suínos em terminação alimentados com diferentes níveis de restrição alimentar e de energia na dieta Carcass quality of pigs in the finishing period fed with different feed restriction levels and energy in the diet

O trabalho objetivou avaliar quatro níveis de restrição alimentar (RA) (0, 5, 10 e 15%) e dois níveis de energia líquida (EL) na dieta (2.083 e 2.252kcal EL/kg de ração) sobre as características de carcaça de suínos na fase de terminação. Foram utilizados 48 suínos Dalland, 24 machos castrados e 24 fêmeas, distribuídos em delineamento experimental de blocos ao acaso em arranjo fatorial 4´ 2´ 2 (nível de restrição x nível de energia ´ sexo). Foram avaliados: peso da carcaça quente, comprimento da carcaça, espessura média do toucinho, rendimentos da carcaça e de cortes e relação carne:gordura na carcaça. Os resultados mostraram melhora na qualidade da carcaça, considerando-se a redução na espessura de toucinho (Y= 2,587 - 0,0186RA) e o aumento no peso (Y= 6,628 + 0,0276RA) e nos rendimentos do lombo (Y= 6,5895 + 0,1389RA - 0,0081RA²) e do pernil (Y= 17,143 + 0,0646RA) com o aumento da restrição alimentar. O aumento da energia líquida da dieta resultou em aumento no rendimento da carcaça (77,4 e 79,1%). As fêmeas apresentaram menor espessura de toucinho do que os machos castrados (2,36 e 2,54 cm).<br>This research aimed to evaluate the effect of feed restriction (FR) and net energy (NE) levels on the carcass quality of pigs in the finishing period. Forty eight animals, 24 barrows and 24 gilts were used in a completely randomized block design with three replicates of each sex. The treatments consisted of a 4 ´ 2 factorial (four levels of feed restriction - 0, 5, 10 and 15% - and two levels of net energy - 2083 and 2252kcal NE/kg of feed). The hot carcass weight, carcass length, backfat thickness, dressing percentage of carcass and of cuts and meat:fat ratio in the carcass were evaluated. The results showed an improvement in carcass quality, considering the reduction in backfat thickness (Y= 2.587 - 0.0186FR) and the increase in weight (Y= 6.628 + 0.0276FR) and in yielding of ham (Y= 6.5895 + 0.1389FR - 0.0081FR²) and loin (Y= 17.1430 + 0.0646FR) with the increase of feed restriction level. The increase in the net energy level of the diet resulted in an increase in carcass dressing percentage (77.4 and 79.1%). Gilts had better backfat tickness than the castrated males (2.36 and 2.54cm)