Temporal niche overlap among insectivorous small mammals

Being active in the same environment at different times exposes animals to the effects of very different environmental factors, both biotic and abiotic. In the present study, we used live traps equipped with timing devices to evaluate the potential role of biotic factors (competition and food abundance) on overall overlap in the temporal niche axis of 4 insectivorous small mammals in high‐elevation grassland fields (‘campos de altitude’) of southern Brazil. Based on resources availability (invertebrates), data on animal captures were pooled in 2 seasons: ‘scarcity’ (June 2001–September 2001) and ‘abundance’ (November 2001–May 2002) seasons. We tested for non‐random structure in temporal niche overlap among the species in each season. These species were the rodents Oxymycterus nasutus (Waterhouse, 1837), Deltamys sp., Akodon azarae (Fischer, 1829), and the marsupial Monodelphis brevicaudis Olfers, 1818. The studied community was mainly diurnal with crepuscular peaks. Simulations using the Pianka index of niche overlap indicated that the empirical assemblage‐wide overlap was not significantly different from randomly generated patterns in the abundance season but significantly greater than expected by chance alone in the scarcity season. All the species showed an increase in temporal niche breadth during the abundance season, which appears to be related to longer daylength and high nocturnal temperatures. Patterns on both temporal niche overlap and temporal niche breadth were the opposite to those that we were expecting in the case of diel activity patterns determined by competition for dietary resources. Therefore, we conclude that competition did not seem to be preponderant for determining patterns of temporal niche overlap by the studied community.     

Chronic cervical compressive myelopathy in horses: clinical correlations with spinal cord alterations

Histological examination was performed on the cervical spinal cord from 13 horses with chronic cervical compressive myelopathy of 4 to 29 months duration. Structural alterations were correlated with clinical features. At the level of compression, the spinal cord was grossly deformed. Histological alterations included nerve fibre swelling and degeneration, occasional spheroids, astrocytic gliosis, increased macrophage activity and increased perivascular collagen. Myelin degeneration or loss at the level of the compressive lesion was greatest in the ventral and lateral funiculi and less consistently present in the dorsal funiculi. Asymmetry of lesions in the dorsal funiculi was associated with asymmetry of clinical signs in 5 horses. Histological alterations in areas of Wallerian degeneration were similar to that at the level of spinal cord compression, except that perivascular collagen was not increased. Wallerian degeneration was present cranial to the compressed site in the superficial portions of the lateral funiculi and in the middle of the dorsal funiculi. Caudal to the compressed site it was present in the ventral funiculi adjacent to the ventral median fissure and in the middle of the lateral funiculi. Deformation of the spinal cord did not correlate with the severity or duration of clinical signs but was positively correlated with the amount of perivascular collagen increase. The amount of nerve fibre swelling was not correlated with the severity of clinical signs but was negatively correlated with their duration. A rapid loss of nerve fibres apparently occurred early in the course of compression, since there was a marked decrease in the amount of nerve fibre swelling and Marchi stained degenerating myelin with increasing clinical duration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacterial flagella: polarity of elongation

Newly synthesized regions of Bacillus subtilis flagella were labeled with fluorophenylalanine or [(3)H]leucine. The flagella were then examined for altered gross morphology or by radioautography. Results of both experiments indicate that flagella elongate in vivo by polymerization of flagellin subunits onto the distal end of the filament.     

Shedding and Seroprevalence of Pathogenic Leptospira spp. in Sheep and Cattle at a New Zealand Abattoir

A cross‐sectional study was carried out on sheep and cattle slaughtered at a New Zealand abattoir from September to November 2010 to investigate the supplier‐specific shedding rate, renal carriage rate and seroprevalence of leptospires. In the 2008/2009 season, this abattoir experienced three human leptospirosis cases from 20 staff, of which two were hospitalized. Urine, kidney and blood samples were collected from carcasses of 399 sheep (six suppliers, 17 slaughter lines) and 146 cattle (three suppliers, 22 slaughter lines). The urine and kidney samples were tested by quantitative real‐time PCR (qPCR), while serum samples (from coagulated blood samples) were tested by microscopic agglutination test (MAT). In total, 27% (73/274; 95% CI: 18–37) of urine samples tested positive by qPCR. Species‐specific shedding rates (prevalence of positive urine qPCR) were 31% (95% CI: 17–48) for sheep and 21% (95% CI: 14–30) for cattle. For 545 kidney samples tested, 145 were qPCR positive (27%; 95% CI: 17–39). The average prevalence of kidney qPCR positivity was 29% (95% CI: 17–45) for sheep and 21% (95% CI: 15–28) for cattle. Three hundred and thirty of 542 sampled sheep and cattle had antibodies against Leptospira borgpetersenii serovar Hardjobovis (Hardjobovis) and/or Leptospira interrogans serovar Pomona (Pomona), based on reciprocal MAT titre ≥1 : 48 (overall seroprevalence of 61%; 95% CI: 48–73). Seroprevalence was 57% (95% CI: 40–72) for sheep and 73% (95% CI: 59–83) for cattle. Among the seropositive animals, 41% (70/170; 95% CI: 30–54) were shedding (tested positive by urine qPCR) and 42% (137/330; 95% CI: 30–54) had renal carriage (tested positive by kidney qPCR). Some risk management options for abattoirs or farms to prevent human leptospirosis infections include vaccination of maintenance hosts, the use of personal protective equipment, and the application of urine qPCR to detect shedding status of stock as surveillance and as an alert.     

An outbreak of avian malaria in captive yellowheads/mohua (Mohoua ochrocephala)

CASE HISTORY: Eight mohua, or yellowheads (Mohoua ochrocephala), were held in a large open aviary over the summer months of 2003–2004, following their capture for captivebreeding purposes. Two birds died of transportation trauma shortly after arrival, one became ill and died a month later, and another four died within a 2-week period in February 2004. The eighth bird also became ill at this time but survived for a year following treatment with chloroquine and doxycycline.

CLINICAL AND PATHOLOGICAL FINDINGS: The affected birds were depressed, lethargic and dyspnoeic. Necropsy of three birds showed a slightly pale and swollen liver and spleen. Impression smears of the liver of one bird revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes, which was confirmed histopathologically. Similar protozoal organisms were seen within splenic histiocytes and pulmonary endothelial cells of 5/6 birds. Electron microscopy identified these as protozoal schizonts containing merozoites of similar size and structure to those of Plasmodium spp.

DIAGNOSIS: The birds were infected with a protozoal haemoparasite resembling Plasmodium spp.; asexual stages within hepatocytes and endothelial cells of the lung and spleen were typical of this organism.

CONCLUSIONS AND CLINICAL RELEVANCE: The mohua captured from west Otago were highly susceptible to avian malaria as they came from an isolated population that was likely to be naïve and have had no previous contact with this organism. The birds were probably infected by bites from mosquitoes feeding off local populations of blackbirds subsequently found to be infected with Plasmodium spp.