Invasive potential of bacterial isolates associated with subclinical bovine mastitis

This work describes differences in the invasive ability of bacterial isolates associated with mastitis. Invasion ability was determined by the uptake and survival in a primary culture of bovine mammary epithelial cells (BMEC). BMEC were isolated from a healthy lactating cow and characterized by their morphology, immunostaining for cytokeratin and the detection of beta- and kappa-casein mRNAs. Ten bacterial isolates comprising the staphylococcal species Staphylococcus aureus (3), Staphylococcus epidermidis (1), Staphylococcus haemolyticus (1), Staphylococcus equorum (2), Staphylococcus xylosus (1) and Brevibacterium stationis (2) obtained from raw milk of cows with mastitis from backyard farms were assayed for their ability to invade BMEC. Only two S. aureus and one S. epidermidis isolates were able to invade BMEC, at similar levels to the S. aureus control strain ATCC 27543. In conclusion, using the in vitro model of infection used in this study, differences in bacterial invasion capability may be detected.     

Ecology and epidemiology of anthrax in cattle and humans in Zambia

Anthrax is endemic in Western and North-western Provinces of Zambia. The disease occurs throughout the year and impacts negatively on the economy of the livestock industry and public health in Zambia. During 1989-1995, there were 1626 suspected cases of anthrax in cattle in Western province and of these 51 were confirmed. There were 220 cases of human anthrax cases in 1990 alone and 248 cases during 1991-1998 with 19.1% and 7.7% case fatality rates, respectively. Interplay of the ecology of affected areas and anthropogenic factors seem to trigger anthrax epidemics. Anthrax has drawn considerable attention in recent years due to its potential use as a biological weapon. In this paper, the history, current status and approaches towards the control of the disease in Zambia are discussed. Quarantine measures restrict trade of livestock and exchange of animals for draught power resulting in poor food security at household levels. Challenges of anthrax control are complex and comprise of socio-political, economical, environmental and cultural factors. Inadequate funding, lack of innovative disease control strategies and lack of cooperation from stakeholders are the major constraints to the control of the disease. It is hoped that the information provided here will stimulate continued awareness for the veterinary and medical authorities to maintain their surveillance and capabilities against the disease. This may lead to a culminating positive impact on livestock and human health in the southern African region.     

Pesticide/herbicide pollutants in the Kafue River and a preliminary investigation into their biological effect through catalase levels in fish

The study determined the types of pesticide/herbicide pollutants in water, sediment and fish from the Kafue River. A preliminary investigation of the oxidative stress from these pesticides/herbicides was also assessed by measurement of catalase activity. Water, sediment and fish samples were collected upstream, midstream and downstream the Kafue river in Chingola, Kitwe, Kafue National Park and Kafue Town. Water, sediment and fish muscle were sampled and analysed for pesticides using Gas chromatography. For catalase activity fish liver samples only were examined. The pesticides/herbicides detected in all samples collectively included: Heptachlor, pp'-DDE, Cypermethrin, Chlordane, Toxaphene, Terbufos, Kelthane, Endosulfan, Dieldrin, pp'-DDD, pp'-DDT, Atrazine, Disulfoton, d-trans-Allethrin and Endrin. On the other hand, catalase activity was detected in all fish liver samples from all sites. Its levels increased significantly from Chingola upstream to sites downstream with highest being in Kafue town. This study therefore, demonstrates that there is widespread contamination of the Kafue River with pesticides/ herbicides. It also demonstrates that organochlorides are found throughout the river especially in fish samples. The spectrum of pesticides/herbicides was much wider in fish probably due to bioaccumulation. It was also observed that fish are subjected to oxidative stress as determined by catalase levels. The stress is more pronounced downstream where the catalase levels were significantly higher than Chingola. The observation that more pesticide varieties are also found downstream may suggest a likely causative effect of the pesticides on oxidative stress although this needs further investigation. This study further tentatively highlights the potential dangers of these agro-related substances to dependants of the Kafue River water body and the need to carry out risk assessments and thereafter institute corrective measures to help reduce contamination and adverse effects.     

Immunopathological effects of porcine circovirus type 2 (PCV2) on swine alveolar macrophages by in vitro inoculation

Porcine circovirus type 2 (PCV2) is the primary causative agent of postweaning multisystemic wasting syndrome (PMWS), a multifactorial disease, in pigs. Monocyte/macrophage lineage cells, including alveolar macrophages (AMs), are the major target cells for PCV2. Swine AMs are essential for the pulmonary defense system against various pathogens. Concurrent infection of lung with opportunistic pathogens in pigs suffered from PMWS is speculated as a feature of immunosuppression. The present study was conducted to characterize the effects of PCV2 inoculation on swine AMs in the in vitro system. The parameters selected for evaluation included PCV2 antigen- and nucleic acid-containing rate, viability, TUNEL-positive rate, phagocytosis, microbicidal capability, and capacity for production of reactive oxygen species (superoxide anion, O₂⁻, and hydrogen peroxide, H₂O₂), cytokines, and chemokines. High intracytoplasmic PCV2 antigen- and nucleic acid-containing rate, absence of intranuclear signals for PCV2 antigen and nucleic acid, and lack of noticeable cell death were seen in PCV2-inoculated AMs. The PCV2-inoculated AMs displayed a transient as well as persistent reduction in the up-take and destruction of Candida albicans, respectively, accompanied by decrease in the production of O₂⁻ and H₂O₂. In PCV2-inoculated AMs, the levels of tumor necrosis- (TNF-) and interleukin-8 (IL-8) were significantly increased; the mRNA expression levels of alveolar macrophage-derived neutrophil chemotactic factors-II (AMCF-II), granulocyte colony-stimulating factor (G-CSF), monocyte chemotactic protein-1 (MCP-1), and IL-8 were strongly up-regulated. The reduced phagocytosis and microbicidal capability in conjunction with decreased production of reactive oxygen species in PCV2-inoculated AMs suggest that PCV2-containing AMs may favor the survival and spread of PCV2. It is speculated that the functional alterations observed in PCV2-containing AMs may be potentially harmful to the lung tissue and local pulmonary defense system, especially in those PCV2-infected pigs conditioned by various PMWS development-dependent co-factors.     

Effects of low concentrations of vapour of the phenoxyalkanoic herbicide 2,4-D-butyl on growth of tomato plants

Tomato plants (5–7 weeks old)were exposed to a range of concentrations of vapour of 2,4-D-butyl (0.12–2.4 ng litre^?;1), for periods of 6 or 24 h, using an air-flow system. Net carbon dioxide exchange of the whole plant was measured for up to 2 days after exposure and was found to decrease in treated plants approximately in proportion to vapour concentration. Six weeks after exposure, shoot dry-weights of plants exposed to herbicide vapour were less than control plants in all cases, by about 20 % or more. All characteristics measured were affected more by a 24-h exposure period than 6 h, at the same vapour concentration. The amount of herbicide vapour, expressed as the product of exposure period and vapour concentration, gave a similar effect at a low range of vapour concentrations (≤1.0 ng litre^?;1)and air-flow rates of about 200 litre min^?;1, but not at higher concentrations at a flow rate of about 120 litre min ^?;1. Better agreement between the experiments carried out at the two concentration ranges was obtained by expressing the herbicide vapour as the total amount to which the plants were exposed (i.e. the product of air-flow rate, vapour concentration and duration of exposure)instead of concentration alone.     

Influence of artificial gaps in tropical forest on survival, growth, and Phytolyma lata attack on Milicia excelsa

Milicia excelsa and M. regia are important timber species in moist tropical areas of Africa. They have not been successfully grown largely because of attacks by gall-forming psyllids in the genus Phytolyma. Our objectives were to evaluate the growth of planted Milicia seedlings and incidence of psyllid attack in small (4.2 m²), medium (18.5 m²) and large (>500 m²) artificial gaps in the Bobiri Forest Reserve in the Moist Semi-Deciduous Forest of Ghana. After 13 months, height and diameter growth of Milicia seedlings were significantly greater in the medium and large gaps than in the small gaps. Insect attacks occurred first and most severely in the large gaps, but spread to gaps of all sizes between the 11th and 13th months after planting. While gap size significantly affected the susceptibility of seedlings to psyllid attack, it is not the only factor important in determining susceptibility of Milicia excelsa under field conditions. We conclude that gap sizes in the range of 10–50 m², where irradiances are from 30–60% of full sunlight, in forests similar to those at the study site, seem to be most suitable for regeneration of Milicia.     

Nutrition of fig (Ficus carica L.) under hydroponics and greenhouse conditions

In this investigation the extraction curve of macronutrients (N, P, K, Ca, Mg) and micronutrients (Fe, Cu, Zn and Mn) were determined in the cultivation of fig. A system of intensive production of fig in greenhouse and hydroponics was established with 1.25 plants m^?2. The determination of the nitrogen content was done by the micro-Kjeldahl method. The P was by the yellow molybdovanadate method throughon a spectrophotometer. The K was determined by flamometry and the Ca, Mg, Fe, Cu, Zn and Mn were determined by atomic absorption spectrophotometry. Of the organs analyzed, the stem was the that accumulated more dry matter, then, the leaves and finally the fruits. The nutrient extraction dynamics presented similar upward behavior in all nutrients. The demand for macronutrients in decreasing order was N?>?K?>?P?>?Ca?>?Mg and for the micronutrients Cu?>?Fe?>?Mn?>?Zn.     

Monitoring Cry1Ab susceptibility in Asian corn borer (Lepidoptera: Crambidae) on Bt corn in the Philippines

Between 2002 and 2004, collections of egg masses of Asian corn borer (ACB), Ostrinia furnacalis (Guenée) were made from corn-planting sites on the major Philippine islands of Luzon (Laguna, Pangasinan, Camarines Sur and Isabela provinces) and Mindanao (Bukidnon and South Cotabato provinces). The resulting neonates were bioassayed for susceptibility to Bacillus thuringiensis (Bt) Cry1Ab protein. The median lethal concentrations (LC₅₀s) for the different collections ranged from 0.42 to 2.37 ng/cm². The bioassay results suggest that Philippine corn borer populations were highly susceptible to Cry1Ab protein prior to the widespread deployment of Bt corn. The upper limit of the estimated LC₉₉ (104 ng/cm²) from the pooled bioassay data was selected as a candidate diagnostic concentration and subsequently tested on eleven ACB populations. Results of the validation assays showed that the mortality response of all the tested ACB populations was higher than the expected mortality (99%). Therefore, the concentration of 104 ng/cm² was used to monitor susceptibility in ACB populations in the Philippines. Monitoring of field populations during 2009 in areas where Bt corn had been grown for 3 years found some enhanced survival of neonates at the diagnostic concentration but progeny of the diagnostic-concentration survivors did not survive on Bt corn, indicating that ACB populations in the Philippines remain susceptible to Cry1Ab-containing Bt corn hybrids.     

Fertilization of lodgepole pine trees increased diameter growth but reduced root carbohydrate concentrations

Tree growth variables and more complex derived variables such as vigor index have all been linked to the ability of lodgepole pine (Pinus contorta var latifolia) trees to defend against insect herbivores, particularly mountain pine beetle (Dendroctonus ponderosae Hopkins, Coleoptera: Curculionidae). These variables are considered indirect measures of carbohydrate reserves. Trees with high vigor index values have high growth rates and are assumed to have high carbohydrate reserves. However, this critical assumption was untested for lodgepole pine. In this paper we evaluated the relationship between carbohydrate concentration and tree characteristics. We measured concentrations of root starch in 10 pure lodgepole pine stands of different ages in the Canadian Rockies which had been fertilized, thinned, fertilized and thinned or left untreated in a 2 × 2 factorial design. Both fertilization and thinning increased basal area increment while only fertilization increased lateral branch growth in the crown. Contrary to expectations, fertilization decreased root starch reserves although it increased basal area increment; thinning had no effect on root carbohydrates. Root starch reserves were positively related to basal area increment and vigor index in both fertilized and unfertilized plots, however, the best predictors of starch reserves were height-to-live-crown and cambial surface area below the live crown; starch reserves declined as both of these variables increased. These data suggest that large carbon sinks associated with long boles below the crown, and rapid growth of the crown and stem as a result of fertilization are detrimental to building starch reserves in the roots.     

Carbon isotope discrimination and water stress in trembling aspen following variable retention harvesting

Variable retention harvesting (VRH) has been proposed as a silvicultural practice to maintain biodiversity and ecosystem integrity. No previous study has examined tree carbon isotope discrimination to provide insights into water stress that could lead to dieback and mortality of trees following VRH. We measured and compared the carbon isotope ratios (delta(13)C) in stem wood of trembling aspen (Populus tremuloides Michx.) before and after VRH. Eight trees were sampled from isolated residual, edge and control (interior of unharvested stand) positions from each of seven plots in three regions (Calling Lake and Drayton Valley, Alberta and Lac Duparquet, Québec). After VRH, the general trend in mean delta(13)C was residual > edge > control trees. Although this trend is indicative of water stress in residual trees, it also suggests that edge trees received some sheltering effect, reducing their stress compared with that of residuals. A strong inverse relationship was found between the delta(13)C values and the mean annual precipitation in each region. The trend in mean delta(13)C signature was Calling Lake > Drayton Valley > Lac Duparquet trees. These results suggest that residual or edge trees in drier regions are more likely to suffer water stress following VRH. We also observed a trend of greater delta(13)C in stout trees compared with slender trees, both before and after VRH. The evidence of greater water stress in stout trees likely occurred because of a positive relationship between stem diameter and crown volume per basal area. Our results provide evidence that water stress could be the driving mechanism leading to dieback and mortality of residual trees shortly after VRH. Additionally, the results from edge trees indicate that leaving hardwood residuals in larger patches or more sheltered landscape positions could reduce the water stress to which these trees are subjected, thereby reducing dieback and mortality.