The histological lesions of Trichophyton mentagrophytes var erinacei infection in dogs

A retrospective study of the histological features of four cases of canine Trichophyton menta-grophytes var erinacei infection is reported. In all four dogs the initial lesions affected the dorsal muzzle and in two dogs the lesions spread to more distant sites on the body. Clinically, the lesions were characterized by scaling, crusting and hair loss. Histologically, the main lesions were characterized by acanthosis, epidermal, ostial and infundibular hyperkeratosis, serocellular crusting, mural folliculitis and furunculosis. Fungal hyphae were usually sparse and often difficult to see in haematoxylin and eosin stained sections. When visible they were seen in the epidermal, ostial and infundibular scale and, less frequently, within hair shafts.     

Photosensitive dermatitis in two Collie working dogs

Two Collie working dogs were examined because of the sudden appearance of a skin condition. Both dogs were depressed and anorectic with an acute exudative dermatitis confined to areas of non-pigmented skin. Antibacterial treatment was instituted initially followed by long-term use of a sun-protective cream. A diagnosis of photosensitive dermatitis was made but the cause of the photosensitivity was not determined.     

Rhodococcus equi infection of cats

Six cases of Rhodococcus equi infection in cats are described. One cat had pneumonia and died. The remaining five cats had cutaneous lesions affecting the feet in four of the cats and the metacarpus in one cat, and all these cats recovered with the aid of antibiotics. All the Rhodococcus equi isolates were sensitive to amoxycillin/clavulanic acid and, where used, at least 14–16 days of treatment was needed to help eliminate the infection. Histologically and cytologically the reaction was pyogranulomatous and many macrophages in the lesions contained large numbers of Gram-positive bacteria.     

Interrelationships between plant functional types and soil moisture heterogeneity for semiarid landscapes within the grassland/forest continuum: a unified conceptual model

In semiarid landscapes, the ratio of herbaceous to woody plant biomass is a major determinant of ecosystem properties. This ratio depends to a large extent on the amount and spatial distribution of soil moisture that is available to plants, and these variables, in turn, are determined primarily by climate and land use. Current conceptual models for determining the ratio of herbaceous to woody plant biomass in semiarid plant communities are based either on differences in soil moisture with depth (vertical heterogeneity) from one site to another (Walter's two-layer model) or on differences in soil moisture between canopy and intercanopy patches at the same site (horizontal heterogeneity) that result from disturbances associated with land use (Schlesinger et al.'s model of desertification). We developed a model that unifies these two perspectives by relaxing two assumptions of Walter's two-layer model. First, our model recognizes that soil moisture varies horizontally between canopy and intercanopy patches, not only due to land-use disturbance, a general assumption of the Schlesinger et al. model, but also due to the physical nature of the canopy itself. Second, while retaining the general assumption of Walter that woody plants obtain moisture from deeper soil layers than do herbaceous plants, our model recognizes the existence of two types of woody plants: those that extract a substantial proportion of their moisture from deeper layers and those that extract mainly from shallower layers. By modifying the two-layer hypothesis to include four soil compartments and distinguishing between shallow- and deeper-rooted woody species, our model integrates three key concepts in semiarid ecology: (1) the proportion of woody cover increases as moisture in the deeper soil layers increases (Walter's two-layer hypothesis for coexistence of herbaceous and woody plants); (2) land use practices that cause a reduction in herbaceous vegetation and compaction of intercanopy soils lead to a long-term increase in the proportion of woody plants (Schlesinger et al.'s concept, or more generally, that at a given site multiple variations in the proportions of herbaceous and woody plant biomass are possible); and (3) changes in the ratios of herbaceous to woody plant biomass exhibit complex behavior (changes can happen quickly and are not directly reversible without intensive management). This integration of concepts results because rather than assuming a simple, one-way dependence of plant functional types on soil moisture heterogeneity, our model assumes an interdependence between the two: soil moisture heterogeneity constrains the composition of the plant community, which in turn modifies soil moisture heterogeneity. The four-compartment model that we propose enables, for the first time, an integrated picture of both dimensions of soil moisture heterogeneity – horizontal and vertical – and of the interdependence between soil moisture heterogeneity and the proportions of the plant functional types that make up a given plant community. This unified conceptual model can be applied to provide insight into the individual and the combined effects of climate and land use on semiarid plant communities within the grassland/forest continuum, which vary in the proportions of canopy and intercanopy patches.     

Photosensitive dermatitis in two Collie working dogs

Two Collie working dogs were examined because of the sudden appearance of a skin condition. Both dogs were depressed and anorectic with an acute exudative dermatitis confined to areas of non-pigmented skin. Antibacterial treatment was instituted initially followed by long-term use of a sun-protective cream.

A diagnosis of photosensitive dermatitis was made but the cause of the photosensitivity was not determined.     

Lesions in the brains of three cattle resembling the lesions of enterotoxaemia in lambs

CASE HISTORY: A 3-month-old female Angus calf was found dead, and two adult Friesian dairy cows died soon after developing nervous signs.

PATHOLOGICAL FINDINGS: Grossly, bilateral and mostly symmetrical areas of haemorrhage were evident that mainly involved areas of grey matter in the brainstem from the level of the caudal colliculi to the thalamus and, in one, the internal capsule and caudate nucleus. In the occipital and caudal parietal cortex, there was extensive oedema of white matter. Histologically, in addition to haemorrhage, there was protein-rich oedema around arterioles and venules in the cerebrum, hippocampus, internal capsule, thalamus, midbrain, dorsal medulla, and central cerebellar and cerebellar folial white matter. The calf's brain had bilateral and symmetrical oedema and necrosis affecting several brainstem nuclei and the occipital grey matter overlying areas of oedema of the corona radiata.

DIAGNOSIS: Although the cause was not established, the perivascular lesions resembled those produced in calves by the intravenous administration of epsilon toxin.

CLINICAL RELEVANCE: It is possible that epsilon toxin-induced enterotoxaemia occurs naturally in cattle, and where bilateral haemorrhage is recognised in the brains of cattle, small intestinal contents should be collected for analysis of epsilon toxin.     

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.