The efficacy of a petroleum spray oil against Aphis gossypii Glover on cotton. Part 1: mortality rates and sources of variation

Petroleum spray oils (PSOs) kill insect pests on contact, and the composition of modern PSOs is substantially different from the ones introduced earlier. The effects of direct application of a new nC24 PSO on the cotton aphid, Aphis gossypii Glover, were therefore determined. This covered not only aphid mortality rates but also the way in which the oils affected aphid behaviour at the time of contact with the oil. Direct application of the nC24 oil proved to be highly effective in controlling A. gossypii at a range of concentrations between 1 and 10% v/v. The oil killed cotton aphids quickly, with most of the mortality occurring within the first 10 min of spraying. The fast killing action of the oils prevented any behavioural responses by the aphids. Aphids killed by the oils became flaccid and their legs and antennae extended horizontally relative to the body axis. With time, their cuticle became very shiny and began to darken. The quick death of the aphids suggested a contact mode of action of the oils, an interpretation supported by the lack of any negative effect on aphids not initially reached by the oils. However, those aphids not hit by the oils, but that subsequently encountered oil-treated areas when they moved elsewhere, also died, indicating that the oil deposits are also toxic to the aphids. The mode of action of the oil thus seems to be versatile, and the means by which it kills the aphids may be more complex than anoxia, which is the widely claimed mechanism attributed to PSOs. This oil now needs to be tested for any possible indirect effects on the cotton aphid (e.g. through its host-plant acceptance behaviour). The implications of the present findings for cotton aphid control and assessment of PSO efficacy in the field are discussed.     

Evaluation of modified vaccinia virus Ankara expressing VP2 protein of infectious bursal disease virus as an immunogen in chickens

A recombinant modified vaccinia Ankara (MVA) virus expressing mature viral protein 2 (VP2) of the infectious bursal disease virus (IBDV) was constructed to develop MVA-based vaccines for poultry. We demonstrated that this recombinant virus was able to induce a specific immune response by observing the production of anti-IBDV-seroneutralizing antibodies in specific pathogen-free chickens. Besides, as the epitopes of VP2 responsible to induce IBDV-neutralizing antibodies are discontinuous, our results suggest that VP2 protein expressed from MVA-VP2 maintained the correct conformational structure. To our knowledge, this is the first report on the usefulness of MVA-based vectors for developing recombinant vaccines for poultry.     

上海富朗特动物保健有限公司专栏——维生素营养(五)维生素缺乏导致家禽的神经性疾病

维生素是不同于脂肪、碳水化合物和蛋白质的有机化合物,以极微的含量自然存在于大多数食物中,以满足正常的生理功能.它们在家禽营养上的重要性被其缺乏时所出现的各种缺乏症所证实.它们扮演了有机体内的一系列角色,如抗氧化分子、基因转录调节器、神经递质和核酸的生物合成、细胞分裂驱动器、器官发育和胚胎形成,所有这些都可促进正常的神经功能.在家禽营养中,一种或多种维生素的缺乏会导致神经系统疾病,如周围神经病变、瘫痪、共济失调、反射消失、脑病、角弓反张、运动失调和抽搐.     

Conservation value of tropical secondary forest: A herpetofaunal perspective

In some areas of the tropics forests are recovering on abandoned cattle pastures. These secondary forests may be important habitats for conserving biodiversity, but we know little about their species composition over the long term. We studied herpetofaunal community changes in a 40 years chronosequence of forest succession on abandoned pastures in Puerto Rico. Twelve submontane sites (100-250 masl) represented four forest recovery stages: pasture, young (1-5 years after abandonment), intermediate (10-20 years), and advanced (40 years). Among these stages we analyzed the relationship of forest structure, microclimate, and herpetofaunal community structure. During succession total forest height increased, new strata of vegetation appeared in the understory, and the forest gained heterogeneity and complexity. Microclimate changed with changes in the physiognomy and structure of the vegetation. Microclimatic shifts were more dramatic in forest <20 years since abandonment. During 1 year we observed 7991 individuals of thirteen reptilian species (60% of observations) and six anuran species. Herpetofaunal richness was similar among stages, but the total abundance increased through succession. Relative abundance of anurans and reptiles was similar between stages, but species dominance changed with succession. Forest >20 years old resembles mature forest in some structural characteristics important to herpetofauna and can provide habitat for forest herpetofauna in disturbed areas.     

Diversity among agrobacteria isolated from diseased plants of blueberry (Vaccinium corymbosum) in Argentina

The aim of this study was to isolate, identify and analyze the diversity of the causative agents of crown galls and hairy roots from symptomatic plants of Vaccinium corymbossum by means of biological, biochemical and molecular tools. All the bacteria isolated from blueberries (n?=?78) were found to be Agrobacterium since they grew on three differential media, provoked cell and/or root proliferation on Kalanchoe, and contained a 730?bp partial sequence that codes for virulence genes within the virC operon found on Ti and/or Ri plasmids. Isolates were highly variable considering the ERIC-PCR patterns as well as biochemical reactions and were all represented by 7 different restriction patterns of the 16SrDNA. While most of the isolates belonged to Agrobacterium bv. 1 (n?=?33) or Agrobacterium bv. 2 (n?=?31) only fourteen were Agrobacterium rubi. A representative isolate of each of these three groups was further identified by sequencing the approximately 400?bp 16SrDNA. We concluded that Vaccinium plants are particularly susceptible to Agrobacterium bv. 1, Agrobacterium bv. 2, and also to Agrobacterium rubi. To our knowledge this is the first survey of Agrobacterium affecting blueberries in Argentina.     

Elevated α-esterase levels associated with permethrin tolerance in Aedes aegypti (L.) from Baja California, Mexico

A discriminating dose for permethrin for Aedes aegypti from Baja California, Mexico was determined, and was used to select individuals. Mosquitoes were collected from four different municipalities located in the north and south end of the Baja California Peninsula. Individuals were chosen for further study based on their similar response to the insecticide. We exposed 10 groups of 90 Ae. aegypti females to the discriminating dose (172 μg/ml) and after producing 50% mortality, individuals were divided into two categories: killed and survivors. Each of these groups was dissected to separate the head, thorax, and abdomen. Biochemical tests were performed on the head and thorax to determine resistance-related enzyme activities including: α- and β-esterases, glutathione S-transferase, acetyl cholinesterase, insensitive acetyl cholinesterase, and mixed-function oxidases. The results were compared with those for the susceptible New Orleans strain of Ae. aegypti. All the populations studied showed the consistent presence of α-esterases, with elevated levels in permethrin-selected populations. Although β-esterases and GST levels were present in high proportions, they did not reveal a clear pattern in relation to resistance.     

Characterization of langerhans cells in epidermal sheets along the body of Armadillo (Dasypus novemcinctus)

Armadillos are apparently important reservoirs of Mycobacterium leprae and an animal model for human leprosy, whose immune system has been poorly studied. We aimed at characterizing the armadillo's langerhans cells (LC) using epidermal sheets instead of tissue sections, since the latter restrict analysis only to cut-traversed cells. Epidermal sheets by providing an en face view, are particularly convenient to evaluate dendritic morphology (cells are complete), spatial distribution (regular vs. clustered), and frequency (cell number/tissue area). Lack of anti-armadillo antibodies was overcome using LC-restricted ATPase staining, allowing assessment of cell frequency, cell size, and dendrites extension. Average LC frequency in four animals was 528 LC/mm(2), showing a rather uniform non-clustered distribution, which increased towards the animal's head, while cell size increased towards the tail; without overt differences between sexes. The screening of antibodies to human DC (MHC-II, CD 1a, langerin, CD86) in armadillo epidermal sheets, revealed positive cells with prominent dendritic morphology only with MHC-II and CD86. This allowed us to test DC mobilization from epidermis into dermis under topical oxazolone stimulation, a finding that was corroborated using whole skin conventional sections. We hope that the characterization of armadillo's LC will incite studies of leprosy and immunity in this animal model.     

Molecular diversity of Brazilian strains of porcine circovirus type 2 (PCV-2)

Porcine circovirus 2 (PCV-2) is associated with a broad range of syndromes. In this study, eight pig tissue samples from two Brazilian states were analyzed using six PCR primer pairs amplifying a 1705-bp fragment of the PCV-2 genome. The NJ distance-based method was used for the phylogenetic analysis with the eight field strains herein, 15 GenBank sequences and using PCV-1 as an out-group. This yielded two major clusters (A and B) for this viral species, with the Brazilian strains segregating with European and Asian sequences. Nucleotide identity was 99.7 to 100% among the sequences. This information can be used in further studies of pathogenesis related to PCV-2 in Brazil.