Prevention of Toxoplasma gondii abortion in goats by vaccination with oocysts of Hammondia hammondi

Nineteen does (female goats) were dosed with 500,000 oocytes of Hammondia hammondi prior to breeding. At about 90 days of gestation these, and 18 uninoculated does were challenged with 25,000 Toxoplasma gondii oocysts. The 19 H. hammondi--inoculated does produced 26 live and one dead kid (newborn goat). The 18 does not given H. hammondi produced 12 live and 19 dead kids. However, examination of all of the kids by isolation of T. gondii in mice, serology and histology revealed that they were all infected with T. gondii. Thus, while H. hammondi "vaccination" is protective against the deleterious effects of T. gondii on pregnant does, perhaps by reducing the severity of placental lesions, it does not prevent foetal infection.     

Vegetation,Hydrologic, and Erosion Responses of Sagebrush Steppe 9 Yr Following Mechanical Tree Removal

Land managers across the western United States are faced with selecting and applying tree-removal treatments on pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland-encroached sagebrush (Artemisia spp.) rangelands, but current understanding of long-term vegetation and hydrological responses of sagebrush sites to tree removal is inadequate for guiding management. This study applied a suite of vegetation and soil measures (0.5 ? 990 m²), small-plot rainfall simulations (0.5 m²), and overland flow experiments (9 m²) to quantify the effects of mechanical tree removal (tree cutting and mastication) on vegetation, runoff, and erosion at two mid- to late-succession woodland-encroached sagebrush sites in the Great Basin, United States, 9 yr after treatment. Low amounts of hillslope-scale shrub (3 ? 15%) and grass (7 ? 12%) canopy cover and extensive intercanopy (area between tree canopies) bare ground (69 ? 88% bare, 75% of area) in untreated areas at both sites facilitated high levels of runoff and sediment from high-intensity (102 mm ? h^? 1, 45 min) rainfall simulations in interspaces (~ 45 mm runoff, 59 ? 381 g ? m^? 2 sediment) between trees and shrubs and from concentrated overland flow experiments (15, 30, and 45 L ? min^? 1, 8 min each) in the intercanopy (371 ? 501 L runoff, 2 342 ? 3 015 g sediment). Tree cutting increased hillslope-scale density of sagebrush by 5% and perennial grass cover by twofold at one site while tree cutting and mastication increased hillslope-scale sagebrush density by 36% and 16%, respectively, and perennial grass cover by threefold at a second more-degraded (initially more sparsely vegetated) site over nine growing seasons. Cover of cheatgrass (Bromus tectorum L.) was < 1% at the sites pretreatment and 1 ? 7% 9 yr after treatment. Bare ground remained high across both sites 9 yr after tree removal and was reduced by treatments solely at the more degraded site. Increases in hillslope-scale vegetation following tree removal had limited impact on runoff and erosion for rainfall simulations and concentrated flow experiments at both sites due to persistent high bare ground. The one exception was reduced runoff and erosion within the cut treatments for intercanopy plots with cut-downed-trees. The cut-downed-trees provided ample litter cover and tree debris at the ground surface to reduce the amount and erosive energy of concentrated overland flow. Trends in hillslope-scale vegetation responses to tree removal in this study demonstrate the effectiveness of mechanical treatments to reestablish sagebrush steppe vegetation without increasing cheatgrass for mid- to late-succession woodland-encroached sites along the warm-dry to cool-moist soil temperature ? moisture threshold in the Great Basin. Our results indicate improved hydrologic function through sagebrush steppe vegetation recruitment after mechanical tree removal on mid- to late-succession woodlands can require more than 9 yr. We anticipate intercanopy runoff and erosion rates will decrease over time at both sites as shrub and grass cover continue to increase, but follow-up tree removal will be needed to prevent pinyon and juniper recolonization. The low intercanopy runoff and erosion measured underneath isolated cut-downed-trees in this study clearly demonstrate that tree debris following mechanical treatments can effectively limit microsite-scale runoff and erosion over time where tree debris settles in good contact with the soil surface.     

Different drivers create spatial vegetation cover and vertical structure in semi-arid African savannas

Important drivers of woody cover in African savannas are rainfall, soil and nutrients, and disturbance factors, such as fire and herbivory. However, very little is known about how these drivers influence woody cover at specific height classes. The main aim of this study was to identify which of these drivers are the best predictors of woody cover at three height classes: shrub (0.75–2.5 m), brush (2.5–5.5 m) and tree (>5.5 m). Percent woody cover estimates were collected using a rapid monitoring technique over 1 700 sites in Kruger National Park, South Africa. Geology (basalt and granite), mean annual rainfall, fire frequency and elephant density were analysed as potential drivers of woody cover. Results indicate that mean annual rainfall was negatively associated with shrub cover, fire frequency was negatively associated with brush cover, and elephant density was negatively associated with tree cover. Patterns of woody cover show that while geology influences the spatial distribution of horizontal woody cover, variation in vertical vegetation structure is created and maintained by top-down disturbance. This provides the first documentation of drivers associated with structurally differentiated woody cover at regional scales. Future studies on woody cover in disturbance-driven environments should not ignore vegetation structure.     

Osteochondrosis dissecans in a juvenile roan antelope (Hippotragus equinus).

A 4-mo-old, juvenile roan antelope (Hippotragus equinus) presented for an acute and progressive lameness of the left hind limb, which was non-responsive to anti-inflammatory medication. The antelope was anesthetized for examination, radiography, and lab work. The left stifle joint had limited range of motion and was markedly swollen on physical examination. Radiography revealed thin cortices of the left distal femur and proximal tibia, as well as multiple lytic areas in the condyles. Euthanasia was performed due to the severity of the lesions and the animal's overall physical condition. Postmortem findings included a parasitic infection of the gastrointestinal tract. Cartilaginous erosions, associated with fibrotic connective tissue and viscous joint fluid, were identified in all appendicular joints. Perimortem lab work demonstrated anemia and hypoproteinemia. Joint fluid was inflammatory but non-infectious, and aerobic culture of the joint was negative for pathogens. Histologic examination identified focal, transmural necrosis of the articular cartilage with clefting. Osteochondrosis dissecans was diagnosed, which initiated an evaluation of the nutritional status and management of the herd. This is the first documented case of osteochondrosis dissecans in a roan antelope.