Landscape connectivity and predator–prey population dynamics

Landscapes are increasingly fragmented, and conservation programs have started to look at network approaches for maintaining populations at a larger scale. We present an agent-based model of predator–prey dynamics where the agents (i.e. the individuals of either the predator or prey population) are able to move between different patches in a landscaped network. We then analyze population level and coexistence probability given node-centrality measures that characterize specific patches. We show that both predator and prey species benefit from living in globally well-connected patches (i.e. with high closeness centrality). However, the maximum number of prey species is reached, on average, at lower closeness centrality levels than for predator species. Hence, prey species benefit from constraints imposed on species movement in fragmented landscapes since they can reproduce with a lesser risk of predation, and their need for using anti-predatory strategies decreases.     

Study on Blood Cell Immune Response in Water Buffaloes Infected Acutely with F. hepatica

Action mechanism of blood cell immune response in water buffaloes against acute infection with F. Hepatica was studied. The results showed that after water buffaloes were infected, the total levels of WBC surpassed control group during whole infection period; Eosinophiles (%) of DC were higher than control group at the 2nd week until 19th week, and then dropped and was close to control group; Neutrophiles(%)was low or significantly lower than control group within the 5 - 16th weeks; The total levels of lymphocytes (%) was lower than control group during the whole infection period; T-lymphocytes (%) dropped significantly, but B-lymphocytes(%) had opposite changes from the first week of infection, and they were close to the control group after 11 weeks; RBC-CR1 and RBC-IC rosette rates dropped and rose during 2 - 16 and 2- 18 weeks, respectively, and then approached the same between both groups. It was suggested that the violent changes of specific and nonspecific immune responses in water buffaloes with acute F. hepatica infection are related with the mechanism against infection with F. hepatica together.     

Calcitonin Promotes Mouse Pre‐implantation Development: Involvement of Calcium Mobilization and P38 Mitogen‐Activated Protein Kinase Activation

The study was designed to examine the effects of calcitonin (CT) on the development of murine pre‐implantation embryos and possible molecular mechanisms involved in the process. In the present study, the 2‐cell embryos were treated with different concentration of CT in vitro for the indicated time and the results demonstrated that CT promoted the development of the pre‐implantation embryos in a dosage‐dependent manner by increasing the intracellular Ca²⁺ level. Furthermore, the present study showed that CT significantly increased the expression of phospho‐P38MAPK (Mitogen‐Activated Protein Kinase) of the pre‐implantation embryos by Western blots and pre‐treatment of specific P38MAPK inhibitor significantly reduced the promotion effects of CT on the embryonic development in vitro culture. Moreover, the results of intrauterine horn injection showed that the average number of embryos implanted in CT‐antibody or specific P38 MAPK inhibitor‐treated uterus was significantly lower than that of the corresponding control, respectively. And the observation of tissue specimen suggested that some embryos were degenerated in CT‐antibody or specific P38 MAPK inhibitor‐treated uterus, and adipose vacuoles were present in the decidual cells. In conclusion, CT promoted the development of pre‐implantation embryos and the intracellular Ca²⁺‐dependent P38MAPK signal molecule was involved in the process.     

High levels of genetic and genotypic diversity in field populations of the barley pathogen Ramularia collo-cygni

The ascomycete pathogen Ramularia collo-cygni causes Ramularia leaf spot (RLS) on barley. Although R. collo-cygni is considerd an emerging disease of barley, little is known about genetic diversity or population genetic structure of this pathogen. We applied a set of polymorphic AFLP (Amplified Fragment Length Polymorphism) markers to investigate population genetic structure in two Northern European populations of R. collo-cygni. The distribution of AFLP alleles revealed low levels of population subdivision and high levels of genetic diversity at both locations. Our analyses included 87 isolates and of these 84 showed a unique genotype pattern. The genetic structure of populations in Scotland and Denmark is highly similar and we find no evidence of population sub-division. An analysis of molecular variance was used to show that 86 % of the variance is attributable to within field genetic variance. In spite of the high levels of genetic and genotypic diversity in the R. collo-cygni populations, we find significant evidence of linkage disequilibrium among the AFLP alleles using a multilocus analysis. We propose that the high levels of genotypic diversity and the lack of population differentiation result from considerable levels of gene flow between populations most likely mediated by seed borne dispersal of inoculum.     

An experimental infection model for reproduction of calf pneumonia with bovine respiratory syncytial virus (BRSV) based on one combined exposure of calves

Bovine respiratory syncytial virus (BRSV) has been recognised as an important pathogen in calf pneumonia for 30 years, but surprisingly few effective infection models for studies of the immune response and the pathogenesis in the natural host have been established. We present a reproducible experimental infection model for BRSV in 2-5-month-old, conventionally reared Jersey calves. Thirty-four colostrum-fed calves were inoculated once by aerosol and intratracheal injection with BRSV. Respiratory disease was recorded in 91% of the BRSV-inoculated calves, 72% had an accompanying rise in rectal temperature and 83% exhibited >5% consolidation of the lung tissue. The disease closely resembled natural outbreaks of BRSV-related pneumonia, and detection of BRSV in nasal secretions and lung tissues confirmed the primary role of BRSV. Nine mock-inoculated control calves failed to develop respiratory disease. This model is a valuable tool for the study of the pathogenesis of BRSV and for vaccine efficacy studies.     

Seroprevalence Estimation and Risk Factors for <Emphasis Type="Italic">A. marginale</Emphasis> on Smallholder Dairy Farms in Tanzania

A cross-sectional serological survey of A. marginale was conducted on 200 randomly selected smallholder farms in each of the Tanga and Iringa Regions of Tanzania between January and April 1999. Sera, from dairy cattle of all ages, sexes and breeds were tested for antibodies against A. marginale using an indirect enzyme-linked immunosorbent assay. Antibodies to A. marginale were present in cattle throughout the study areas and the overall prevalence was 20% for Tanga and 37% for Iringa. The forces of infection based on the age seroprevalence profile were estimated at 8 for Tanga and 15 for Iringa per 100 cattle years-risk, respectively. In both regions, seroprevalence increased with age (β = 0.01 and 0.017 per year of age, p < 0.005, in Tanga and Iringa, respectively). Older animals in Iringa were significantly and negatively associated with decreased seropositivity (β = −0.002, p = 0.0029). Further results of logistic regression models reveal that geographic location of animals in Tanga was associated with seropositivity (odds ratio (OR) = 2.94, p = 0.005, for Tanga Rural and OR = 2.38, p = 0.066, for Muheza). Animals acquired as a gift in Iringa had higher odds for seropositivity than brought-in cattle (OR = 2.44, p = 0.005). Our study has identified and quantified some key risk factors that can guide planners devising disease control strategies.     

Some Factors Affecting Reproductive Success in Crossbred Dairy Cows on Smallholder Farms in Coastal North-East Tanzania

A 2-year longitudinal survey was carried out to investigate factors affecting reproduction in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of reproductive traits and body condition score (BCS) were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in reproductive traits were investigated using a general linear model (GLM) by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), type of insemination, calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. The effects of the independent variables identified were then investigated using a non-parametric survival technique. The number of days to first oestrus was increased on the U site (p = 0.045) and when family labour was used (p = 0.02). The non-parametric test confirmed the effect of site (p = 0.059), but effect of labour was not significant. The number of days from calving to conception was reduced by hiring labour (p = 0.003) and using natural service (p = 0.028). The non-parametric test confirmed the effects of type of insemination (p = 0.0001) while also identifying extended calving intervals on U and SU sites (p = 0.014). Labour source was again non-significant. Calving interval was prolonged on U and SU sites (p = 0.021), by the use of AI (p = 0.031) and by the use of family labour (p = 0.001). The non-parametric test confirmed the effect of site (p = 0.008) and insemination type (p > 0.0001) but not of labour source. It was concluded that under favourable conditions (PU site, hired labour and natural service) calving intervals of around 440 days could be achieved.     

Spill-over of European bat lyssavirus type 1 into a stone marten (Martes foina) in Germany

European bat lyssavirus type 1 (EBLV-1, genotype 5) is known to endemically circulate in insectivorous bat populations in Germany. In August 2001, a rabies suspect stone marten (Martes foina) was found in the city of Burg (Saxony-Anhalt, Germany) and was sent to the regional veterinary laboratory for routine rabies diagnosis. Whereas brain samples repeatedly tested negative in the fluorescent antibody test for classical rabies virus (genotype 1), the mouse inoculation test and the rabies tissue culture inoculation test yielded positive results. Rabies viral RNA was also detected in the stone marten brain sample both by nested and heminested RT-PCR specific for the nucleoprotein gene and for the nucleoprotein phosphoprotein junction of rabies virus. The amplification products were sequenced to genotype the isolate. Sequence data obtained from the first-round RT-PCR products were analysed and the suspect stone marten isolate was confirmed as a rabies related virus (EBLV-1a). Phylogenetic comparison with sequences from recent genotype five isolates from Germany and Denmark showed that it was closely related to a previous isolate of EBLV-1 from a serotine bat in Saxony-Anhalt obtained in the same year in an area adjacent to the place where the EBLV-1 infected stone marten was found. Both EBLV-1 isolates share a 99.5% identity. This is the first report of an EBLV-1a spill-over from an insectivorous bat into wildlife in Europe.