Randal S. Stahl

A pilot study exploring the use of breath analysis to differentiate healthy cattle from cattle experimentally infected with Mycobacterium bovis.

Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease of international public health importance. Ante-mortem surveillance is essential for control; however, current surveillance tests are hampered by limitations affecting ease of use or quality of results. There is an emerging interest in human and veterinary medicine in diagnosing disease via identification of volatile organic compounds produced by pathogens and host-pathogen interactions. The objective of this pilot study was to explore application of existing human breath collection and analysis methodologies to cattle as a means to identify M. bovis infection through detection of unique volatile organic compounds or changes in the volatile organic compound profiles present in breath. Breath samples from 23 male Holstein calves (7 non-infected and 16 M. bovis-infected) were collected onto commercially available sorbent cartridges using a mask system at 90 days post-inoculation with M. bovis. Samples were analyzed using gas chromatography-mass spectrometry, and chromatographic data were analyzed using standard analytical chemical and metabolomic analyses, principle components analysis, and a linear discriminant algorithm. The findings provide proof of concept that breath-derived volatile organic compound analysis can be used to differentiate between healthy and M. bovis-infected cattle.

Thermal fumigation provides a simple and effective solution for sanitizing cargo from invasive snakes

The Brown Treesnake (Boiga irregularis) is invasive in Guam and threatens to be dispersed by military and civilian transportation activities to other islands in the Pacific, where it could be expected to inflict similar damages. Prevention of inadvertent export of snakes in cargo and vehicles currently relies on trained canine detection teams, which are expensive to use and unable to detect all snakes. Hence, there has long been interest in developing effective and cheaper means of fumigating cargo to remove snakes. A companion study has shown that chemical fumigation is unlikely to be readily developed into a practical tool. Here, we demonstrate that these snakes are readily induced to quit test refugia by application of streams of heated air. Many parameters affect snake response times, but we find that application of relatively low temperatures (48–52xa0°C) at moderate delivery rates (3.4xa0m3/min) is sufficient to induce exit of these snakes within 5xa0min. Development of a portable heat-delivery system based on these findings has great potential to ensure snakes do not unintentionally stow away to other locations in cargo, munitions, vehicles, or airplane wheelwells. Application of such technology can be done on Guam as well as at locations receiving cargo or vehicles from that source, providing an additional layer of security in ensuring these snakes do not colonize additional locations outside their native range.

Development of artificial bait for brown treesnake suppression

The brown treesnake (Boiga irregularis) was accidentally introduced to Guam in the 1940s from the Admiralty Islands. A native of Australia, Papua New Guinea, and the Solomon Islands, the brown treesnake (BTS) continues to threaten the economy and ecology of Guam and is currently the subject of a cooperative program to control snake populations on the island and prevent its spread throughout the Pacific Rim. Delivery of toxic baits is a primary component of population suppression efforts. While many food items tested as baits for toxicant delivery provide relevant food prey cues leading to investigatory behaviors in BTS, only a few items tested in the past two decades have adequately promoted reliable consumption. Chief among them is the dead neonatal mouse (DNM). A series of chemical and bioassays were performed to identify materials with similar sensory qualities as DNM. Among the many items tested in a series of field experiments with free-ranging BTS in Guam, a processed meat product treated with an artificial mouse fat mixture was found to be removed from bait stations at rates greater than previously tested DNM substitutes and approaching removal rates of DNM. Furthermore, the test baits demonstrated excellent durability under field conditions. Further development of this bait offers great potential to satisfy many desirable attributes for BTS baiting operations.

Chemical repellents appear non-useful for eliciting exit of brown tree snakes from cargo

The brown tree snake (Boiga irregularis) is invasive in Guam, has imposed ecological and economic problems there, and threatens to be dispersed via cargo and vehicles to other islands in the Pacific, where it could be expected to inflict similar damages. Prevention of inadvertent snake export currently relies on cargo inspection and suppression of snake populations around ports, which are expensive and incompletely reliable. Hence, there has long been interest in developing additional tools to preclude snakes leaving in cargo, and fumigation with essential oils has been suggested for this role. We tested gaseous or aerosol deliveries of several essential oils and three other candidate irritants. We found none to work reliably in repelling snakes, and we discuss several limitations that make development of an effective fumigation tool from these chemicals improbable. Additional effort to develop an operational tool using essential oils would likely be misdirected, and effective fumigation methods for invasive snakes should be sought elsewhere.

An assessment of radiative heating as a thermal treatment for invasive snakes in cargo

ABSTRACT The brown tree snake (Boiga irregularis) is invasive in Guam and presents a continuous threat of accidental export to new islands in outbound cargo. Current attempts to avoid that scenario rely primarily on canine teams to inspect outbound cargo and vehicles. In prior work, we showed that thermal fumigation could effectively elicit snake exit of cargo under conditions when free flow of air streams is feasible, but this method cannot work with tightly packed cargo. Here we show radiative heating can effectively induce snake exit from cargo refuges at temperatures of 44–48 °C; however, we find passive solar heating of cargo to be unreliable in attaining sufficiently high temperatures for cargo sterilization. Although passive solar radiant heating proved unreliable, an active radiant-heating system has promise as a reliable means of treating tightly packed cargo. Times needed for treatment in a closed, controlled setting are sufficiently short that routine application of the method should provide no serious interruption of normal cargo-handling procedures.

An evaluation of the use of pentosidine as a biomarker for ageing turtles

Concentrations of the chemical pentosidine in the bodies of endotherms are highly correlated with age, providing a useful biomarker for ageing individuals and potentially for assessing demographic structure in endangered populations. In this first study of pentosidine in an ectotherm, we found only a weak correlation in a turtle.

Comparing a bioenergetics model with feeding rates of caged European starlings

ABSTRACT n We tested a bioenergetics model integrated within a mortality model that estimates numbers of European starlings (Sturnus vulgaris) poisoned with the avicide, Compound DRC-1339 Concentrate. The bioenergetics model predicted daily metabolic rate. Accuracy and reliability of this variable is critical because other algorithms (e.g., toxicity regressions, feeding behavior) in the mortality model depend on metabolic rate to calculate the amount of DRC-1339 ingested per bird. We tested the bioenergetics model by comparing its estimates of metabolic rate with those generated from measuring feeding rates of caged starlings during a feeding trial conducted outdoors during January 2008. Over the 12-day feeding trial, daily feeding rates of caged starlings indicated that metabolic rates ranged from 157 kJ/bird per day to 305 kJ/bird per day. The bioenergetics model predicted metabolic rates ranging from 208 kJ/bird per day to 274 kJ/bird per day. There was no difference between these 2 independently derived estimates of daily metabolic rate (paired t-test: t (11) = 1.4, P = 0.18). Using 95% confidence intervals calculated from variation of feeding rates among cages (n = 4, 6 birds/cage), the bioenergetics models estimates were within 95% confidence intervals on 9 of 12 days and greater than the upper 95% confidence interval on 3 days. Daily estimates of metabolic rate were directly correlated between the bioenergetics model and the feeding-rate model (r 12 = 0.57, P = 0.05). A broad range of temperatures (-17°C to 14°C), wind speeds (0–40 km/hr), and percent cloud cover (0–100%) were encountered during the feeding trial. The bioenergetics models predictions appeared robust to varying meteorological conditions typical of winters in middle latitudes of the interior United States. Compound DRC-1339 Concentrate is used by USDA Wildlife Services to manage chronic infestations of starlings at livestock facilities, which occur mainly during fall and winter. Compared to other methods used for estimating DRC-1339 mortality (e.g., counting birds pre- and posttreatment), bioenergetics modeling should improve the mortality models overall accuracy and precision.

Using pentosidine and hydroxyproline to predict age and sex in an avian species

Abstract All living organisms are subject to senescence accompanied by progressive and irreversible physiological changes. The error damage and cross‐linking theories suggest that cells and tissues are damaged by an accumulation of cross‐linked proteins, slowing down bodily processes and resulting in aging. A major category of these cross‐linked proteins are compounds called advanced glycation end products (AGEs). We investigated the relationship between accumulation of the AGE, pentosidine (Ps), and hydroxyproline (HYP) a post‐translationally modified amino acid, with age, sex, and breeding status (breeder/nonbreeder) from skin samples of known age (i.e., banded as fledglings), free‐ranging Double‐crested Cormorants (Phalacrocorax auritus, Lesson 1831). We developed multivariate models and evaluated the predictive capability of our models for determining age and breeding versus nonbreeding birds. We found significant relationships with Ps and HYP concentration and age, and Ps concentration and sex. Based on our two‐class model using Ps and HYP as explanatory variables, we were able to accurately determine whether a cormorant was a breeder or nonbreeder in 83.5% of modeled classifications. Our data indicate that Ps and HYP concentrations can be used to determine breeding status of cormorants and potentially age of cormorants although sex‐specific models may be necessary. Although the accumulation of Ps explained the greatest amount of variance in breeding status and age, importantly, Ps covaried with HYP and combined improved prediction of these demographics in cormorants. Our data support the error damage and cross‐linking theories of aging. Both Ps and HYP increase predictably in cormorants and are predictive of age and breeding status. Given the ubiquity of these biomarkers across taxa, their use in estimating demographic characteristics of animals could provide a powerful tool in animal ecology, conservation, and management.