Longevity of Mycobacterium bovis in brushtail possum (Trichosurus vulpecula) carcasses,and contact rates between possums and carcasses

Abstract

AIM: To determine, for a variety of environmental conditions, how long Mycobacterium bovis might remain viable inside the carcass of a brushtail possum (Trichosurus vulpecula) that died of bovine tuberculosis (Tb), and to measure the rate of contact between free-ranging possums and possum carcasses.

METHODS: Lesions of M. bovis were simulated by inoculating excised spleens weighing 0.5–1 g with 0.2 mL liquid culture containing approximately 5 x 10⁷ cfu M. bovis/mL. Simulated lesions were inserted into possum carcasses (n=48) at the peripheral lymph nodes. Carcasses were placed in the field at two sites (a tussock grassland and a podocarp-broadleaved forest site) and in two seasons (summer and winter) for up to 62 days. Survival rates of M. bovis were estimated by sampling the simulated lesions over time, and culturing the recovered lesion to determine if any viable M. bovis bacteria were present.

The time taken for a free-ranging possum to first encounter a dead possum in its home range was estimated by live-trapping possums and fitting them with proximity loggers (n=13). A ‘contact’ was recorded if these possums came within 40–50 cm of proximity loggers fitted to possum carcasses.

RESULTS: There were strong seasonal and site effects in the survival rate of M. bovis in possum carcasses. In the grassland habitat, no viable bacilli were cultured from any carcass after 3 days in summer, whereas in winter all samples were culture-positive for the first 20 days, and some were still positive after 27 days. The survival rates for forest habitat were intermediate between the results for grassland, and there were no culture-positive carcasses after 9 days in summer or 27 days in winter.

In summer, infected carcasses (n=6) were first encountered by possums a mean 1.9 (range 0.4–6.7) days after placement.

CONCLUSIONS: Possum carcasses were contacted by free-ranging possums within the period that viable M. bovis were shown to survive in a carcass. The risk of such infection is likely to be most significant in winter or in areas with microhabitats where the survival of M. bovis is high. However, the generally low survival rate of M. bovis in possum carcasses and the low frequency of possum-to-carcass contacts indicate this route of transmission alone could not maintain Tb in a possum population.     

Cytologic examination of fine‐needle aspirates from mammary gland tumors in the dog: diagnostic accuracy with comparison to histopathology and association with postoperative outcome

Background: Mammary tumors are the most common neoplasms in female dogs. Malignant tumors may carry a poor prognosis and necessitate surgery. Few data are available on the value of cytologic examination as a diagnostic or prognostic tool for mammary tumors in dogs. Objectives: The objectives of this study were to determine whether cytologic findings in fine‐needle aspirate specimens of canine mammary tumors correlate with histopathologic results and whether the cytologic diagnosis is associated with postoperative outcome. Methods: In this prospective study, fine‐needle aspirate samples were obtained from 50 mammary tumors in 50 dogs. Results of cytologic and histopathologic examination were compared, using the histologic diagnosis as the reference method. Kaplan–Meier log rank analysis was used to evaluate univariate association of the cytologic diagnosis with duration of survival, local control, and metastasis‐free interval. Results: Adequate cytologic samples were obtained in 43/50 (86%) cases. The cytologic diagnosis correlated with the histologic diagnosis for benign and malignant tumors in 40/43 (93%) and 35/43 (81%) cases, respectively. Cytologic examination had a sensitivity of 88% and a specificity of 96% for the diagnosis of malignancy. The cytologic diagnosis had significant univariate association with duration of survival (P=.016), recurrence‐free interval (P=.003), and metastasis‐free interval (P=.014). Conclusions: Cytologic examination of mammary tumors in the dog has satisfactory accuracy, sensitivity, and specificity for the diagnosis of malignancy and is associated with postoperative outcome. Further studies on the diagnostic accuracy of cytology as well as multivariate analysis of its preoperative prognostic value in mammary tumors in the dog are warranted.     

Serum cobalamin concentrations in healthy cats and cats with non-alimentary tract illness in Australia

Objective   To determine a reference range for serum cobalamin concentration in healthy cats in Australia using a chemiluminescent enzyme immunoassay and to prospectively investigate the prevalence of hypocobalaminaemia in cats with non-alimentary tract disease.
Design   Prospective study measuring serum cobalamin concentrations in clinically healthy cats and cats with non-alimentary tract illness.
Procedure   Blood was collected from 50 clinically healthy cats that were owned by staff and associates of Veterinary Specialist Services or were owned animals presented to Creek Road Cat Clinic for routine vaccination. Blood was collected from 47 cats with non-alimentary tract illness presented at either clinic. Serum cobalamin concentration was determined for each group using a chemiluminescent enzyme immunoassay.
Results   A reference range for Australian cats calculated using the central 95th percentile in the 50 clinically healthy cats was 345 to 3668 pg/mL. Median serum cobalamin concentration in 47 cats with non-alimentary tract illness (1186 pg/mL; range 117–3480) was not significantly different to the median serum cobalamin of the 50 healthy cats (1213 pg/mL, range 311–3688). Using the calculated reference range one sick cat with non-alimentary tract illness had a markedly low serum cobalamin concentration.
Conclusion   Although hypocobalaminaemia is uncommon in sick cats with non-alimentary tract illness in Australia, its occurrence in this study warrants further investigation.     

Development of diets for the intensive culture of Pacific lamprey

The Pacific lamprey Entosphenus tridentatus is an ancestral species of critical importance to the ecosystem and indigenous cultures in the Pacific Northwest. Conservation aquaculture has been proposed as a potential technique to restore Pacific lamprey populations. Intensive culture methods and diets for this species have not been developed. A sixteen week feeding trial tested the effects of seven diet treatments on the survival, growth, fatty acid profile and whole body lipid content of Pacific lamprey ammocoetes. Dietary treatments were: active dry yeast, yeast plus fish oil emulsion, micro‐algae, micro‐algae plus fish oil emulsion, yeast with micro‐algae, yeast with micro‐algae plus fish oil emulsion and yeast with larval fish diet. Each diet was offered to five replicate tanks stocked with 20 ammocoetes that were 51 days post hatch. Survival during the trial was not affected by diet. The greatest length and weight increases were in fish fed diets containing yeast. Growth decreased as the amount of algae in the diet was increased. Lipid retention was significantly higher in fish fed yeast with larval fish diet relative to the other treatments. Feed conversion ratio was lowest in fish fed diets containing yeast. Whole body fatty acid profiles tended to reflect the fatty acid profile of the diet. Percentages of 20:5n‐3 and 22:6n‐3 were significantly higher in fish fed diets containing fish oil emulsion. Overall, yeast with larval fish diet provided the best growth performance in larval Pacific lamprey.     

Relative amounts of tissues in mature wheat (Triticum aestivum L.) grain and their carbohydrate and phenolic acid composition

Hand dissection of mature grains from two common wheats (Triticum aestivum L., cv. Caphorn and cv. Crousty) were performed to quantitatively assess their tissue composition and to obtain homogeneous samples of embryonic axis, scutellum, starchy endosperm, aleurone layer, hyaline layer, outer pericarp and a composite layer made up of testa+hyaline layer+inner pericarp. Polymeric neutral sugar and phenolic acid contents of the samples were determined and used to identify specific composition patterns in each tissue irrespective of the cultivar. The scutellum and embryonic axis showed the lowest amount of carbohydrates with similar relative amounts of arabinose and xylose (Ara+Xyl), but the scutellum differed from the embryonic axis in its high phenolic acid, in particular ferulate dehydrodimer, content. The peripheral layers of the grains were mainly composed of cell wall polysaccharides, chiefly arabinoxylans but with differing structures. The hyaline layer was mostly composed of arabinoxylan with extremely low Ara/Xyl ratio (0.1), with high amounts of ferulic acid monomers and hence very weakly crosslinked. The aleurone layer differed from the outer pericarp by its much lower Ara/Xyl ratio and lower amounts of ferulic acid dimers and trimers. High proportions of ether-linked phenolic acids (released by alkali at 170 °C) were detected specifically in the seed coat and tissues in the crease region. The possible application of biochemical markers found in the various tissues to monitor wheat grain fractionation processes is discussed.     

Microscopical Study of the Destructuring of Waxy Maize and Smooth Pea Starches by Shear and Heat at Low Hydration

Smooth pea and waxy maize starches were processed under controlled temperature (<160 °C) conditions at low moisture content (30%) using a rheometer with pre-shearing, to simulate extrusion. Specific mechanical energy was measured and remained lower than 10³J/g. Starch modification was analysed at different structural levels by differential scanning calorimetry (DSC), X-ray diffractometry, light microscopy and at the granular level by transmission electron microscopy (TEM). Thermal inputs induced crystallite melting and internal disorganisation of granular structure, whereas mechanical input (SME>10²J/g) induced granule fragmentation. Under shearing and heating, the concomitant destructuring mechanisms led to a higher rate of modification. Fragmentation itself induced only partial loss of crystallinity (<50%). Small fragments finally melted due to a local temperature increase contributed by interparticular friction. Susceptibility to fragmentation was related to the mechanical properties of starch granules associated with their architecture and botanical origin.     

Pulsed laser ablation: A new approach to reveal wheat outer layer properties

A new methodology based on pulsed lasers has been developed in order to estimate wheat outer layer mechanical properties without sample preparation. Laser experiments were carried out with an Argon Fluoride (λ = 193 nm) excimer laser source delivering pulses of 15 ns duration. Wheat grains from two cultivars were irradiated by single laser pulses with a quasi-uniform irradiation and two fluences (2.5 and 5 J cm⁻²). The ablation flux was characterized by environmental scanning electron microscopy before measuring the removed material on cross-sections observed by confocal scanning laser microscopy. Specific image treatment was carried out to obtain the ablation flux (amount of removed matter per pulse). Pericarp, seed coat and aleurone layer were gradually ablated under the laser conditions used in this work. Their ablation thresholds were different and could be related to tissue cohesion. Specific behaviour of seed coat layer (8 μm) could be emphasised with this technique. Pulsed laser ablation could be a potential methodology to reveal indirectly wheat grain layer cohesion.     

Susceptibility of male white-tailed deer (Odocoileus virginianus) to Brucella ovis infection

Infection with Brucella ovis was established by conjunctival instillation in 8 male white-tailed deer (Odocoileus virginianus). Infection was transient in young bucks, but persisted in bucks that were mature when inoculated. The deer were euthanatized and necropsied at various intervals after inoculation. Brucella ovis was recovered from a mature buck at necropsy on postinoculation day 429. Four deer had gross lesions and histopathologic changes of the epididymides. A mature noninfected buck confined for 7 months with an infected buck acquired infection and developed epididymal lesions.