Prevalence and potential risk factors for amitraz resistance in Boophilus microplus ticks in cattle farms in the State of Yucatan, Mexico

Southern cattle tick, Boophilus microplus, control in the Mexican tropics is based on the application by spray, dip or pour-on of acaricides. In Mexico the first report of ticks resistant to amitraz was reported in 2002. Amitraz resistance affecting the cattle industry of Yucatan State, Mexico, has not been investigated. A cross-sectional study was carried out in order to investigate the possible association between management risk factors and the prevalence of B. microplus ticks resistant to amitraz in Yucatan, Mexico. Ninety-eight cattle farms were randomly selected and a sample of 20–30 engorged B. microplus females was collected from at least 10 cattle from each farm. Collected ticks were taken to the laboratory where the larval progeny were obtained. The modified larval immersion test was used to detect ticks resistant to amitraz. A discriminating dose of 0.0002% amitraz was used. A questionnaire was applied on each collaborating farm. For the statistical analysis a 2 × 2 contingency table was used to identify potential risk factors. The prevalence of farms with B. microplus resistant to amitraz was 19.40%. However, even though tick resistance to amitraz is a present problem there was no evidence that it was associated with the risk factors analyzed in this survey.     

Antileishmanial antibody profile in dogs naturally infected with Leishmania chagasi

Visceral leishmaniasis (VL) presents vigorous Th2 immune response, which is mainly characterized in human by augmented expression of Il-4, polyclonal B cell activation, intense hypergammaglobulinemia and production of antileishmanial IgE antibodies. However, few aspects of this type of immune response have been demonstrated in studies of canine visceral leishmaniasis (CVL). This work investigated by ELISA and western immunoblotting the production of antileishmanial IgE antibodies (IgE Ab) in symptomatic and asymptomatic dogs naturally infected by Leishmania chagasi, and also compared this IgE immune response with those of IgG, IgG1 and IgG2 antibodies. Three groups of dogs were evaluated: 12 VL dogs with positive Leishmania biopsies (GI), 44 dogs with a positive leishmanial indirect fluorescent antibody test (IFAT), 30 of them presenting clinical signs of VL and 14 asymptomatic (GII) and 21 healthy dogs living in kennels located in leishmaniasis endemic areas (GIII), which were seronegative in the IFAT. Eighteen dogs from an area free of CVL were used as controls (GIV). Antileishmanial IgE antibodies were detected in 4 of 12 VL dogs from group I (33%) and 14 of 30 symptomatic dogs from group II (47%). While all asymptomatic dogs from group II (100%) were seronegative for antileishmanial IgE Ab, 7 of 21 healthy animals from group III (33%) had these immunoglobulins. A strong correlation was verified between antileishmanial IgG and IgG2 antibody titers in all symptomatic dogs, but only 15 of these 42 animals (36%) produced simultaneously IgE, IgG, IgG1 and IgG2 antibodies to Leishmania. IgE antibodies recognized leishmanial antigens of 12, 36, 61, 81 and 118 KDD, while a more complex pattern of immunoblotting was verified mainly for IgG and IgG2 antibodies from symptomatic animals. IgG1 and IgG2 antibodies shared the recognition of L. chagasi polypeptides of 118, 81, 61, 36, 18, 14 and 12 KDD, being more intense the immune reactions between IgG1 Ab and the leishmanial polypeptides of 61 and 36 KDD, and also between IgG2 antibodies and the antigens of 26, 21, 18, 14 and 12 KDD. Our results suggest that the polyclonal production of antileishmanial antibodies that includes IgE Ab could characterize a Th2 immune response in CVL and can help the laboratory diagnosis of this disease.     

Identification of recombination hotspots and quantitative trait loci for recombination rate in layer chickens

Background: The frequency of recombination events varies across the genome and between individuals, which may be related to some genomic features. The objective of this study was to assess the frequency of recombination events and to identify QTL(quantitative trait loci) for recombination rate in two purebred layer chicken lines.Methods: A total of 1200 white-egg layers(WL) were genotyped with 580 K SNPs and 5108 brown-egg layers(BL)were genotyped with 42 K SNPs(single nucleotide polymorphisms). Recombination events were identified within half-sib families and both the number of recombination events and the recombination rate was calculated within each0.5 Mb window of the genome. The 10% of windows with the highest recombination rate on each chromosome were considered to be recombination hotspots. A BayesB model was used separately for each line to identify genomic regions associated with the genome-wide number of recombination event per meiosis. Regions that explained more than 0.8% of genetic variance of recombination rate were considered to harbor QTL.Results: Heritability of recombination rate was estimated at 0.17 in WL and 0.16 in BL. On average, 11.3 and 23.2 recombination events were detected per individual across the genome in 1301 and 9292 meioses in the WL and BL,respectively. The estimated recombination rates differed significantly between the lines, which could be due to differences in inbreeding levels, and haplotype structures. Dams had about 5% to 20% higher recombination rates per meiosis than sires in both lines. Recombination rate per 0.5 Mb window had a strong negative correlation with chromosome size and a strong positive correlation with GC content and with CpG island density across the genome in both lines. Different QTL for recombination rate were identified in the two lines. There were 190 and 199 non-overlapping recombination hotspots detected in WL and BL respectively, 28 of which were common to both lines.Conclusions: Differences in the recombination rates, hotspot locations, and QTL regions associated with genomewide recombination were observed between lines, indicating the breed-specific feature of detected recombination events and the control of recombination events is a complex polygenic trait.     

Clinical and serological aspects of visceral leishmaniasis in northeast Brazilian dogs naturally infected with Leishmania chagasi

Human visceral leishmaniasis is endemic in the northeast of Brazil, where the domestic dog is an important parasite reservoir in the infectious cycle of Leishmania chagasi. In this study, we evaluated the clinical signs of canine visceral leishmaniasis (CVL), serum protein profile and the antileishmanial IgG antibody production in 86 dogs living in northeast endemic areas of leishmaniasis. Thirty dogs from a leishmaniasis-free area were used as a control group. The major clinical signs of CVL seen were emaciation and skin ulcers (80%), followed by onychogryphosis and conjunctivitis (73%). Depilation was observed in 60% of animals while lymphadenomegaly, splenomegaly, liver enlargement or kidney involvement was less frequent (< or =20%). VL seropositive dogs presented with serum hyperproteinemia, hypoalbuminemia, hypergammaglobulinemia and decreased albumin/globulin ratio. A lower sensitivity and higher specificity was observed for promastigote indirect fluorescent antibody test (IFAT) (83 and 100%, respectively) compared with enzyme-linked immunosorbent assay (ELISA) (94 and 90%), which uses a crude extract of Leishmania. There was a positive correlation between IFAT and ELISA titers of antileishmanial IgG antibodies (Spearman test, P < 0.05), which was augmented in CVL dogs. This study found that the determination of serum protein, A/G ratio and the use of two different leishmanial serological tests like IFAT and ELISA are essential in CVL screening.     

Analysis of water application cost with permanent set sprinkler irrigation systems

In order to identify the subunit design incurring the lowest costs, it is necessary to consider various factors, thereby assuring the correct hydraulic performance of the subunit. Water application costs with a sprinkler irrigation system comprise: investment cost (pumps plant, pipes, sprinklers, ditches), energy, manpower, maintenance and water costs. This work analyses the influence of different design and performance factors, such as subunit arrangement, spacing, working pressure, average application rate, and application efficiency on water application costs in a permanent set sprinkler irrigation subunit. The results show that the most important factor is the spacing between sprinklers. The next most important factor is the shape of the subunit (number of laterals and number of sprinklers per lateral). Working pressure is important too, since a decrease in pressure will result in a decrease in energy costs, although pipe diameter will need to increase. The higher the average application rate of the system, the higher the water application cost. The influence of irrigation efficiency is higher as water price increases. The water application cost can be reduced by 40% when application efficiency increases from 60% to 90%.Communicated by A. Kassam     

Pseudopestalotiopsis elaeidis associated with leaf spots on Cycas revoluta in Brazil

Cycas revoluta (Cycadaceae) is commonly cultivated as an ornamental tree in several countries. In April 2015, C. revoluta leaves showing brownish spots with a yellow halo that progressed to leaflet necrosis were observed in Belém, Pará state, Brazil. This study aimed to determine the aetiology of this disease on sago palm in Brazil. Based on DNA sequence-based phylogeny, morphology, and colony characterization, the fungus was identified as Pseudopestalotiopsis elaeidis. To the best of our knowledge, this is the first report of P. elaeidis associated with leaf spots on C. revoluta worldwide.     

Characterization of antibiosis to the silverleaf whitefly Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) in cowpea entries

The silverleaf whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), is considered one of the most important pests of cowpea (Vigna unguiculata L. Walp.), limiting the productivity of this crop worldwide. Chemical control is still the main strategy for the management of populations of this insect. However, due to the harmful effects of pesticides on the environment and to humans, less injurious alternatives have been investigated. Along this line, the use of resistant genotypes can be a valuable tool for the control of the silverleaf whitefly. In this paper, we investigate some biological aspects of B. tabaci biotype B confined on 14 genotypes of cowpea. We evaluated the incubation period, egg viability, duration of nymphal stages, total duration of the juvenile phase, instar mortality and total mortality of the immature stage. The genotype MNC 99-541 F21 exhibited antibiosis against the whitefly, prolonging the lifecycle of the insect. The genotypes Canapu, BRS-Urubuquara and TE97-304 G-4 also exhibited antibiosis, causing high nymphal mortality. These results may help in breeding programmes to develop cowpea lines with resistance to B. tabaci biotype B.     

Secondary succession in a fragmented Atlantic Forest landscape: evidence of structural and diversity convergence along a chronosequence

Changes in physiognomy, species composition and structure, and dispersal mechanisms of canopy and subcanopy plant assemblages were investigated along a chronosequence of three ages: 12, 20, and 50+ years old (=old-growth), three replications in each, in an Atlantic Forest landscape in Northeastern Brazil. Our objective was to investigate whether there is floristic and structural convergence along secondary succession. There were significant differences between secondary and old-growth forests in density and basal area only for the subcanopy. Differences in density between forest ages were noted when the assemblage was analyzed per diameter and height classes. Richness of canopy species of both secondary ages differed from those of old-growth forests. Some dominant species in the canopy of secondary forests showed a significant decrease in density with increasing age, which indicates an ongoing process of floristic changes. The low level of shared species between secondary and old-growth forests supports the idea that species composition is one of the last components to recover during successional process. Zoochory was the most important dispersal guild in species percentage and number, irrespective of stand age. Although regenerating areas can take alternative pathways, our results indicate that secondary Atlantic Forest sites have a high potential for natural regeneration. This recovery is recorded as a physiognomic convergence of the canopy layer in as little as 12 years, and progressive introductions of later successional species into the plant assemblage that lead to convergence in terms of the diversity and richness of the subcanopy and of dispersal guilds just 20 years after abandonment.     

Comparative transcriptional analyzes of Xanthomonas citri subsp. citri reveal mechanisms of adaptation and bacterial virulence in the early stage of citrus canker disease

European Journal of Plant Pathology - The Allium cepa L. (onion) crop is affected by leaf blight disease caused by Stemphylium vesicarium; the shifts that S. vesicarium infection causes in the...