Olfactory responses of Amblyomma maculatum to rumen fluid and other odourants that attract blood-seeking arthropods

Amblyomma maculatum Koch (Ixodida: Ixodidae) has emerged as a significant vector of human and companion animal diseases in the U.S.A. When expanding in range, A. maculatum can be difficult to collect in the field and control on livestock. A novel method is needed to improve the field collection of A. maculatum, as well as to control their effects as ectoparasites of livestock and companion animals. The present study aimed to test the effects of known volatiles on the activation and selection choices of A. maculatum in a laboratory-based Y-tube assay and field-based assays. Although the majority of adult A. maculatum were activated to move by five of the seven semiochemicals tested, only rumen fluid significantly attracted ticks to make a selection in the Y-tube apparatus. Rumen fluid attracted the most A. maculatum in the laboratory, with 56% (84/150) making it to the rumen Y-tube arm, although the results were not replicated in semi-field experiments. These studies highlight the need for continued work to identify attractants for tick vectors that will assist field collections. These attractants could also be incorporated into management strategies that lead to prevention technologies to reduce tick burdens on cattle or in risk areas of humans.

Filth Fly Activity Associated With Composted and Noncomposted Beef Cadavers and Laboratory Studies on Volatile Organic Compounds

Commercial livestock facilities are faced with the challenge of managing large amounts of waste including manure and animal mortalities. One method of disposing of dead animals is composting. The cadavers are enveloped in carbon material that creates a barrier between the dead tissue and the surrounding environment. Dead tissue can release materials that not only contaminate the soil but also the groundwater and nearby surface water. Animal cadaver composting is designed to facilitate decomposition without the aid of carrion-feeding insects and reduce the presence of common pathogens associated with animal waste and dead tissue. The aim of this study was to evaluate insect activity associated with composted and exposed beef cadavers, specifically filth flies that can serve as mechanical vectors of important human pathogens such as E. coli 0157:H7. Greater numbers of all types of arthropods were trapped overall at the exposed animal site than the composted animal site. Most importantly, the number of filth flies was significantly lower at the composted site (P = 0.0009). Laboratory analysis of volatile organic compounds from composted and noncomposted rats indicated that known fly attractants such as dimethyl disulfide may be inhibited by the composting process. Implementing composting programs at livestock facilities could reduce the risk of flies spreading harmful pathogens to surrounding areas, including farms that grow fresh produce.

Association of Escherichia coli O157:H7 with filth flies (Muscidae and Calliphoridae) captured in leafy greens fields and experimental transmission of E. coli O157:H7 to spinach leaves by house flies (Diptera: Muscidae)

The recent outbreak of Escherichia coli O157:H7 infection associated with contaminated spinach led to an investigation of the role of insects, which frequent fields of leafy greens and neighboring rangeland habitats, in produce contamination. Four leafy greens fields adjacent to cattle-occupied rangeland habitats were sampled using sweep nets and sticky traps. Agromyzid flies, anthomyiid flies, and leafhoppers were caught consistently in both rangeland and leafy greens production fields at all sites. An unexpected number of flies (n = 34) in the Muscidae and Calliphoridae families (known as filth flies because of their development in animal feces) were caught in one leafy greens field. A subset of these filth flies were positive (11 of 18 flies) for E. coli O157:H7 by PCR amplification using primers for the E. coli O157:H7-specific eae gene. Under laboratory conditions, house flies were confined on manure or agar medium containing E. coli O157:H7 tagged with green fluorescent protein (GFP) and then tested for their capacity to transfer the microbes to spinach plants. GFP-tagged bacteria were detected on surfaces of 50 to 100% of leaves examined by fluorescence microscopy and in 100% of samples tested by PCR. These results indicate that flies are capable of contaminating leafy greens under experimental conditions and confirm the importance of further investigation of the role of insects in contamination of fresh produce.

Memory in learning disabled children: digit span and the Rey Auditory Verbal Learning Test

Scores on the Rey Auditory Verbal Learning Test (RAVLT) were compared to WISC-R digit span results in a sample of 153 learning disabled students. With statistical controls for age and IQ, regression analyses indicated no significant relationships between the RAVLT and longest forward span, longest backward span and total digit span raw score. Factor analysis of the RAVLT variables, forward span, backward span and total digit span raw score yielded three factors that were interpreted to represent a long term memory factor, a short-term memory factor with high coding demands and a short-term memory factor with low coding demands. Conclusions were made regarding the inadequacy of using only digit span when making diagnostic statements about the auditory memory functioning of learning disabled students.