Larvicidal and oviposition‐altering activity of monoterpenoids,trans‐anithole and rosemary oil to the yellow fever mosquito Aedes aegypti (Diptera: Culicidae)

BACKGROUND: Aedes aegypti L. is the major vector of dengue fever and dengue hemorrhagic fever. In an effort to find effective tools for control programs to reduce mosquito populations, the authors assessed the acute toxicities of 14 monoterpenoids, trans‐anithole and the essential oil of rosemary against different larval stages of Ae. aegypti. The potential for piperonyl butoxide (PBO) to act as a synergist for these compounds to increase larvicidal activity was also examined, and the oviposition response of gravid Ae. aegypti females to substrates containing these compounds was evaluated in behavioral bioassays. RESULTS: Pulegone, thymol, eugenol, trans‐anithole, rosemary oil and citronellal showed high larvicidal activity against all larval stages of Ae. aegypti (LC₅₀ values 10.3–40.8 mg L^?1). The addition of PBO significantly increased the larvicidal activity of all test compounds (3–250‐fold). Eugenol, citronellal, thymol, pulegone, rosemary oil and cymene showed oviposition deterrent and/or repellent activities, while the presence of borneol, camphor and β‐pinene increased the number of eggs laid in test containers. CONCLUSIONS: This study quantified the lethal and sublethal effects of several phytochemical compounds against all larval stages of Aedes aegypti, providing information that ultimately may have potential in mosquito control programs through acute toxicity and/or the ability to alter reproductive behaviors. Copyright © 2008 Society of Chemical Industry     

Feline leucocyte antigen class II polymorphism and susceptibility to feline infectious peritonitis

There are four outcomes to feline coronavirus (FCoV) infection: the development of feline infectious peritonitis (FIP, which is immune-mediated), subclinical infection, development of healthy lifelong carriers and a small minority of cats who resist infection (Addie and Jarrett, Veterinary Record 148 (2001) 649). Examination of the FCoV genome has shown that the same strain of virus can produce different clinical manifestations, suggesting that host genetic factors may also play a role in the outcome of infection. FIP is most prevalent amongst pedigree cats, although how much of this is due to them living in large groups (leading to higher virus challenge and stress which predisposes to FIP) and how much is due to genetic susceptibility is not known. If host genetics could be shown to play a role in disease, it may allow the detection of cats with a susceptibility to FIP and the development of increased population resistance through selective breeding. The feline leucocyte antigen (FLA) complex contains many genes that are central to the control of the immune response. In this preliminary study, we used clonal sequence analysis or reference strand conformational analysis (RSCA) to analyse the class II FLA-DRB of 25 cats for which the outcome of FCoV exposure was known. Individual cats were shown to have between two and six FLA-DRB alleles. There was no statistically significant association between the number of alleles and the outcome of FCoV infection. No particular allele appeared to be associated with either the development of FIP, resistance to FCoV, or the carrier status. However, the analysis was complicated by apparent breed variation in FLA-DRB and the small number of individuals in this study.     

大豆斑疹病疱斑形成过程的电镜观察

 由(Xanthomonas campestris pv.glycines)所致大豆斑疹病病斑隆起成疱。盆栽大豆感病品种(Chippewa和Horosoy)和它们的抗病品系在二片真叶展开2/3时,用高压喷雾接种(Xanthomonas campestris pv.glycines),接种后的第3、6、9天分别取样;样本分二种处理分别在扫描电镜、透射电镜和普通光学显微镜下观察病斑形成过程.接种后3天,肉眼可见褪绿斑时,病斑部分的表皮细胞和薄壁细胞组织已开始膨大,病斑部分稍有隆起.第6天,肉眼能见疱斑时,表皮细胞和薄壁细胞膨大明显,少数细胞开始破裂.第9天病斑开始变褐,电镜下可见疱斑完全破裂,表皮细胞和薄壁细胞膨大数倍于正常细胞,且细胞破裂,大量细菌溢出。同时可以看到大豆斑疹病细菌在发病初期是在细胞间隙中存活和繁殖的,在表皮细胞和薄壁细胞破裂后进入细胞内,最后完全破坏细胞.从电镜切片中也可以看到疱斑形成主要是由于细胞体积增大所致.抗病品种只有褪绿斑,渐变褐,肉眼看不见疱斑,但在电镜下可见得下表皮稍隆起,有少数细菌存在于细胞间隙,未见有细菌溢出现象。     

Severe complication after administration of formalin for treatment of progressive ethmoidal hematoma in a horse

Formalin was injected into an ethmoidal hematoma in an 18-year-old Arabian gelding. Abnormal neurologic signs were observed within minutes of the injection. The horse did not respond favorably to medical treatment of the neurologic signs and was euthanatized. Postmortem examination revealed erosion and necrosis of the ventral cribriform plate, which appeared to have allowed the injected formalin to reach the rostral portion of the frontal lobe of the brain. Endoscopy and radiography had been performed prior to euthanasia, but neither delineated the cribriform lesion. Before treating large progressive ethmoidal hematomas with formalin, it may be beneficial to perform computed tomography to assess the extent of damage caused by the lesion.     

Colonisation and extinction in relation to competition and resource partitioning in acanthocephalans of freshwater fishes of the British Isles

This paper challenges two paradigms long held in relation to the ecology of parasites in freshwater systems: (1) autogenic species are poorer colonisers than allogenic ones; and (2) parasites with direct life cycles are more successful colonisers than those with complex life cycles. Using new and existing data for Acanthocephala in freshwater fish from the British Isles, it is suggested that all six species present have been able to colonise and persist successfully, in spite of the supposed limitations of their autogenic life-style. It is proposed that these parasites have overcome these limitations by a variety of means, which apply equally to all species considered. Foremost among these is the utilisation of a migratory fish host as either a preferred or a suitable host in their life cycle, allowing colonisation of new areas and rescue effects in established areas, whilst equally important is the use of a common and widespread crustacean as the intermediate host. In addition, all six species appear to exhibit resource partitioning by host at either or both the larval and adult stages, thus reducing the potential for competition and further facilitating colonisation and survival. This hypothesis is supported by data from previous studies both on acanthocephalans from Europe and North America and on other autogenic parasites. It also provides an explanation for the apparently atypical host utilisation patterns of some acanthocephalan species in areas on the edge of their distributions, notably in Ireland.     

Inheritance of fenvalerate and carbofuran resistance in colorado beetles—Leptinotarsa decemlineata (Say)—from North Carolina

Progeny from reciprocal F1 crosses and F1 backcrosses between fenvalerate-resistant and fenvalerate-susceptible Colorado beetles, Leptinotarsa decemlineata (Say), and between carbofuran-resistant and carbofuran-susceptible Colorado beetles were bioassayed to investigate the mode of inheritance of resistance to these chemicals. Bioassays of progeny from these crosses indicate that resistance to fenvalerate is inherited in a semi-recessive, sex-linked manner and carbofuran resistance is inherited in a partially dominant autosomal fashion. Log concentration/probit mortality lines and chi-square tests, however, indicate that multiple genes may be involved in resistance to both insecticides.     

Insecticide resistance patterns among colorado potato beetle,leptinotarsa decemlineata (Say) (Coleoptera: chrysomelidae), populations in north carolina

A residual bioassay was used to determine insecticide susceptibility in populations of Colarado potato beetle, Leptinotarsa decemlineata (Say), in eastern North Carolina. Mean bioassay mortalities were subjected to correlation analysis to assess patterns of resistance among tested insecticides. Within insecticide classes, cross-resistance patterns were observed between carbaryl and carbofuran (carbamates), fenvalerate and permethrin (pyrethroids), and among azinphosmethyl, methamidophos, and phosmet (organophosphates). Significant associations between insecticides from different insecticide classes were concluded to be due to multiple resistance. Knowledge of multiple and cross-resistance patterns are discussed in relation to the bioassay as a tool for monitoring insecticide resistance.