THE EPIDEMIOLOGY OF EQUINE STRONGYLOSIS IN SOUTHERN QUEENSLAND 2. The Survival and Migration of Infective Larvae on Herbage

The seasonal changes in longevity on herbage of the infective larvae of strongylid nematodes of the horse were studied. During the summer months, 1% of the larvae survived on herbage for 2-3 weeks, with 0.2% still viable for a further 2-3 weeks. Equivalent survival periods in winter were 7-11 weeks and over 11 weeks respectively. During spring and autumn, larvae survived for periods varying from 3-8 weeks. On Rhodes grass (Chloris gayana) growing vigorously in the summer of 1976, the majority of larvae remained in the lowest layers of the pasture, within 10 cm of the soil surface. Very few reached the highest fraction of grass sampled, above 40 cm from the soil. More larvae were recovered higher on the pasture in a period when less torrential rain had occurred. It was concluded that the parasitological benefits to be gained from short-term mixed grazing with horses and cattle may be minimal, in view of the tendency of cattle to eat only the upper layers of the pasture initially, with a consequent increase in the number of infective larvae per unit weight of herbage remaining.     

Genomic signatures predict migration and spawning failure in wild Canadian salmon

Long-term population viability of Fraser River sockeye salmon (Oncorhynchus nerka) is threatened by unusually high levels of mortality as they swim to their spawning areas before they spawn. Functional genomic studies on biopsied gill tissue from tagged wild adults that were tracked through ocean and river environments revealed physiological profiles predictive of successful migration and spawning. We identified a common genomic profile that was correlated with survival in each study. In ocean-tagged fish, a mortality-related genomic signature was associated with a 13.5-fold greater chance of dying en route. In river-tagged fish, the same genomic signature was associated with a 50% increase in mortality before reaching the spawning grounds in one of three stocks tested. At the spawning grounds, the same signature was associated with 3.7-fold greater odds of dying without spawning. Functional analysis raises the possibility that the mortality-related signature reflects a viral infection.     

Experimental Ehrlichia canis infection in the dog does not cause immunosuppression

A carrier state develops in some Ehrlichia canis-infected dogs due to ineffective host defenses. The subsequent development of immune-mediated diseases or opportunistic infections in chronic ehrlichiosis suggests dysregulation of immunity; however, the immunobiology of this infection has not been well characterized. In this study, eight dogs were infected with E. canis, and changes in seroreactivity, serum immunoglobulin (Ig) concentrations, peripheral blood T cell subsets, lymphocyte blastogenesis (LBT), and lymphokine-activated killer (LAK) activity were evaluated over 4 months. Infection, which was documented by seroconversion, polymerase chain reaction, and blood culture, caused self-limiting fever and thrombocytopenia. Infected dogs developed an anti-E. canis antibody response but were not immune to re-infection. Serum IgM, IgG, and IgA concentrations were unaffected by E. canis. The percentage of circulating CD4(+) T cells was similar in uninfected and infected dogs at all points. Infected dogs developed a CD8(+) lymphocytosis 6 weeks after inoculation that subsequently subsided, despite organism persistence. Functional defects of cell-mediated immunity, measured as suppression of LAK activity or mitogen-driven LBT, were not observed. These results suggest that immune responses are not grossly impaired in young dogs during the first several months following experimental E. canis infection.     

Intra-annual variability in the contribution of tile drains to basin discharge and phosphorus export in a first-order agricultural catchment

This study examines spatiotemporal variability (event-based, seasonal) in the contribution of drainage tiles within a basin to basin hydrologic discharge and soluble reactive phosphorus (SRP) and total phosphorus (TP) export over a period of 1 year. Tile discharge was highly variable at both moderate (wet versus dry periods) and smaller (within-event) temporal scales, accounting for 0-90% of basin discharge at any given time. An estimated 42% of basin annual discharge originated from drainage tiles, the majority of which occurred during the winter and spring months. Concentrations of SRP and TP in drainage tile effluent were also highly variable in space and time (1-2850 μg SRP L⁻¹, 5-8275 μg TP L⁻¹). Higher concentrations of SRP and TP were linked to fields receiving manure compared to fields receiving inorganic fertilizers. SRP export from tiles accounted for 118% of basin SRP export on average, although their contribution to basin SRP export ranged from 4 to 344% on 32 discrete dates during which all tiles in the basin were sampled for hydrochemistry. On the same 32 dates, tiles accounted for an average of 43% of basin TP export, although this ranged from 0 to 200%. Management options such as tile plugs and optimizing the timing and application rates of fertilizer should be explored to minimize nutrient export from tiles.     

Effects of sediment and contaminated sediment on structural and functional components of experimental stream ecosystems

Three experimental stream ecosystems were used to determine the effects of sediment and contaminated sediment: one stream received 1.7 g L^?1 uncontaminated sediment for 2 hr each week for 6 wk; one stream received 1.7 g L^?1 contaminated sediment (50 to 1600 ppm triphenyl phosphate applied in increasing doses each week) for 2 hr each week for 6 wk; and the third stream was maintained as a control. Each stream was monitored for changes in nutrient dynamics, leaf decomposition, primary production, and invertebrate dynamics. Both sediment and sediment/triphenyl phosphate altered the drift dynamics of benthic invertebrates. Invertebrates in the sediment treatment exhibited delayed nocturnal drift, while those in the sediment/triphenyl phosphate treatment drifted immediately once a threshold of toxicity was reached. Both sediment and sediment/triphenyl phosphate decreased the percent similarity of benthic invertebrates, reduced the drift of filamentous algae, increased the production of rooted flora, and increased net nutrient retention. However, neither treatment altered leaf decomposition rates, nor affected benthic invertebrate dynamics (total number, number of species, or diversity) or insect emergence.     

Community level physiological profile response to plant residue additions in Antarctic soils

Changes in microbial community-level physiological profiles (CLPP) were investigated during decomposition of plant materials in maritime Antarctic soils from Alexander Island and Signy Island. For each soil, a series of microcosms were established and half of them amended with Deschampsia antarctica residues and the other half left unamended (controls). Microcosms were destructively sampled at regular intervals and a soil suspension from each microcosm was used to inoculate BIOLOG EcoPlates. The results showed differences between samples due to the treatment (amendment) but no systematic changes due to incubation period. Microbial response in terms of the overall BIOLOG activity in FB soils was greater than in JC and increased in the former during plant decomposition whilst the overall activity of the JC soils remained relatively unchanged. The differences in the microbial community response to plant amendment between FB and JC may be related to the C:N ratio of these soils and to differences in the way in which the different microbial communities respond to sporadic resource inputs.     

Detection of Follicular Apoptosis in Water Buffalo (Bubalus bubalis) Ovary by Histology and Nick End Labelling Technique

The objective of this experiment was to assess the features and extent of follicular apoptosis in the water buffalo (Bubalus bubalis) ovary using classical histology and nick end labelling technique. Ovaries (n = 40) procured from the slaughterhouse were used for the study. The sections (5 μm) were used for detection of terminal deoxynucleotidyl transferase‐mediated dUTP‐biotin nick end labelling (TUNEL) and classical histology (H&E). Those follicles showing ≥ 5% TUNEL positivity (TUNEL assay) and pyknotic nuclei (histology) in granulosa cells were classified as atretic. Based on histology, the atretic primary and secondary follicles (%) were 93.82 and 95.62 respectively. The histology study reveals that the rates (%) of atresia in <1, 1–3, 3–5 mm and >5 mm were 36.90, 40.50, 62.84 and 74.5 respectively. Further the atretic tertiary follicles (%) were significantly lower than the primary and secondary classes of follicles. TUNEL assay reveals that the atretic rate (%) of tertiary follicles in <1, 1–3, 3–5 and ≥ 5 mm class follicles were 50.88, 53.84, 81.81 and 36.36 respectively. The percentage of atresia in >5 mm diameter follicles were significantly lower in TUNEL than histology. Percentages of granulosa and thecal cells positive for atresia by TUNEL were 30.7 ± 0.53 and 13.82 ± 0.18 respectively per follicle. The initial structural changes in atretic follicles were seen primarily in the granulosa cells. In severely atretic follicles TUNEL positive granulosa cells along with theca cells have to be considered in assessing the rate and extent of atresia.     

Hepatotoxic and nephrotoxic principles in Terminalia oblongata

A study was conducted to identify and characterise the toxic principle in Terminalia oblongata, commonly known as yellow-wood. Crude aqueous extracts of yellow-wood leaf were found to produce the same liver lesion in mice as has been reported in ruminants. The hepatotoxic fraction was isolated and identified as a hydrolysable vegetable tannin called punicalagin. When given orally, the dose required to produce toxicity was at least 20 times greater than when given intraperitoneally. Following a given dose of punicalagin, the onset and severity of liver necrosis was found to be related to the time interval after dosing. In addition to punicalagin, an unidentified nephrotoxic substance was found which was capable of producing avascular renal necrosis without liver necrosis.