Feline lymphoma in the post-feline leukemia virus era

Lymphoma (lymphosarcoma or malignant lymphoma) is the most common neoplasm of the hematopoietic system of cats and reportedly the cat has the highest incidence for lymphoma of any species. A 21-year retrospective survey of feline lymphoma covering the period 1983-2003 was conducted with the patient database at the Veterinary Medicine Teaching Hospital (VMTH) at the University of California, Davis, School of Veterinary Medicine. This period comprises the post-feline leukemia virus (FeLV) era. Feline lymphoma historically has been highly associated with retrovirus infection. Mass testing and elimination and quarantine programs beginning in the 1970s and vaccination programs in the 1980s dramatically reduced the subsequent FeLV infection rate among pet cats. The results of this survey confirm a significant decrease in the importance of FeLV-associated types of lymphoma in cats. In spite of this decrease in FeLV infection, the incidence of lymphoma in cats treated at the VMTH actually increased from 1982 to 2003. This increase was due largely to a rise in the incidence of intestinal lymphoma, and to a lesser degree, of atypical lymphoma. A high incidence of mediastinal lymphomas in young Siamese or Oriental breeds also was observed, supporting previous studies. Associations of intestinal lymphoma and inflammatory bowel disease and diet should be further considered.     

Anthropogenic factors and the risk of highly pathogenic avian influenza H5N1: prospects from a spatial-based model

Beginning in 2003, highly pathogenic avian influenza (HPAI) H5N1 virus spread across Southeast Asia, causing unprecedented epidemics. Thailand was massively infected in 2004 and 2005 and continues today to experience sporadic outbreaks. While research findings suggest that the spread of HPAI H5N1 is influenced primarily by trade patterns, identifying the anthropogenic risk factors involved remains a challenge. In this study, we investigated which anthropogenic factors played a role in the risk of HPAI in Thailand using outbreak data from the “second wave” of the epidemic (3 July 2004 to 5 May 2005) in the country. We first performed a spatial analysis of the relative risk of HPAI H5N1 at the subdistrict level based on a hierarchical Bayesian model. We observed a strong spatial heterogeneity of the relative risk. We then tested a set of potential risk factors in a multivariable linear model. The results confirmed the role of free-grazing ducks and rice-cropping intensity but showed a weak association with fighting cock density. The results also revealed a set of anthropogenic factors significantly linked with the risk of HPAI. High risk was associated strongly with densely populated areas, short distances to a highway junction, and short distances to large cities. These findings highlight a new explanatory pattern for the risk of HPAI and indicate that, in addition to agro-environmental factors, anthropogenic factors play an important role in the spread of H5N1. To limit the spread of future outbreaks, efforts to control the movement of poultry products must be sustained.     

Modeling the dynamics of backyard chicken flows in traditional trade networks in Thailand: implications for surveillance and control of avian influenza

In Southeast Asia, traditional poultry marketing chains have been threatened by epidemics caused by the highly pathogenic avian influenza H5N1 (HPAI H5N1) virus. In Thailand, the trade of live backyard chickens is based on the activities of traders buying chickens from villages and supplying urban markets with chicken meat. This study aims to quantify the flows of chickens traded during a 1-year period in a province of Thailand. A compartmental stochastic dynamic model was constructed to illustrate trade flows of live chickens from villages to slaughterhouses. Live poultry movements present important temporal variations with increased activities during the 15 days preceding the Chinese New Year and, to a lesser extent, other festivals (Qingming Festival, Thai New Year, Hungry Ghost Festival, and International New Year). The average distance of poultry movements ranges from 4 to 25 km, defining a spatial scale for the risk of avian influenza that spread through traditional poultry marketing chains. Some characteristics of traditional poultry networks in Thailand, such as overlapping chicken supply zones, may facilitate disease diffusion over longer distances through combined expansion and relocation processes. This information may be of use in tailoring avian influenza and other emerging infectious poultry disease surveillance and control programs provided that the cost-effectiveness of such scenarios is also evaluated in further studies.     

Is generalisation of uneven-aged management in mountain forests the key to improve biodiversity conservation within forest landscape mosaics?

Context

Uneven-aged management systems based on selection silviculture have become popular in European mountain forests and progressively replace other silvicultural practices. In time, this trend could lead to a homogenisation of the forest mosaic with consequences on structural indices recognised as beneficial to forest biodiversity.

Aims

This study was conducted to investigate the potential effects of a generalisation of the selection silvicultural system on structural diversity in the forest landscape with consequences for forest biodiversity conservation.

Methods

We compared four structural indices (tree species richness, diameter heterogeneity, deadwood volume and basal area of mature trees) in five different stand types typical of the northern French Alps, using forest plot data in the Vercors mountain range. Through virtual landscape simulations, we then calculated predicted mean proportions of stand types under two different conservation strategies: (i) maximising mean index values at the landscape level and (ii) maximising the number of plots in the landscape with index values above given thresholds.

Results

Multi-staged forests did not maximise all indices, the best solution being to combine the five stand types in uneven proportions to improve biodiversity conservation.

Conclusion

The expansion of selection silviculture in European heterogeneous forest landscapes could enhance biodiversity conservation if other stand types with complementary structural characteristics are maintained.     

Gel formation mechanism and gel properties controlled by Ca2+ in chia seed mucilage and model substances

Polygalacturonic acid (PGA) is considered as a model substance for mucilage to study mucilage–soil interactions, assuming that the gel formation mechanism of mucilage is comparable to the one of PGA. However, some studies question the accepted hypothesis, which states that, like for PGA, this mechanism relies on cross‐links between uronic acid and calcium for mucilage. The aim of this study was therefore to understand the influence of the abundance and degree of esterification of uronic acids and the influence of calcium on the gel formation mechanism in mucilage as compared to model substances. The mucilage used was from chia seeds, as it is easily available in great quantity and has gel properties shared by root mucilage. Results reported here demonstrate that, while the gel formation mechanism of PGA relied on specific cross‐links with calcium and led to heterogeneous gels, low‐methoxy pectin (LMP) formed homogeneous calcium gels also characterized by nonspecific ionic interactions with calcium. On the contrary, despite similar uronic acid content to LMP, chia seed mucilage was mostly governed by weak electrostatic interactions between entangled polymer chains, which conferred the gel poor water retention. Addition of calcium reduced repulsion and molecular expansion, resulting in a reduction of the water content in chia seed mucilage. Finally, the discrepancies between PGA, LMP and chia seed mucilage discredit the use of PGA as model for chia seed mucilage. Comparison with root mucilage is still needed. This study offers the keys for further mechanistic understanding on the influence of mucilage on soil properties.     

Does reproductive plasticity in Lumbricus rubellus improve the recovery of populations in frequently inundated river floodplains?

Flooding events often eradicate all of the individuals of the earthworm species Lumbricus rubellus living in river floodplains, although earthworm cocoons usually survive immersion, permitting populations to recover after the flood waters recede. Yet, if the area is flooded again before earthworms hatching from cocoons or migrating from adjacent areas reach reproductive maturity, it is unlikely that their populations will recover. The objective of this study is to determine the importance of the length of the dry period for population recovery in L. rubellus. Earthworms were collected at three floodplain sites along the Rhine River that were frequently, moderately or seldom flooded. Reproductively mature L. rubellus from the frequent flooded site were half the weight and probably younger than those from the other sites. A mechanistic population model was used to estimate the time for earthworm development from hatching to reproductive maturity, and to calculate the probability of population recovery after flooding. The model results show that the probability of extinction increases when the dry period is not long enough for individuals to reach reproductive maturity. When this condition is met population extinction is virtually absent resulting from the high lifetime reproductive output of L. rubellus. Parameterization of the model with site-specific data indicate that population survival on the site with the shortest dry period drastically decreases if worms mature at the weight measured at the other sites. The results therefore strongly suggest that the dry period is critical for population recovery in river floodplains and that earthworm populations have adapted to local (site-specific) conditions.