The strobilurin fungicides

Strobilurins are one of the most important classes of agricultural fungicide. Their invention was inspired by a group of fungicidally active natural products. The outstanding benefits they deliver are currently being utilised in a wide range of crops throughout the world. First launched in 1996, the strobilurins now include the world's biggest selling fungicide, azoxystrobin. By 2002 there will be six strobilurin active ingredients commercially available for agricultural use. This review describes in detail the properties of these active ingredients--their synthesis, biochemical mode of action, biokinetics, fungicidal activity, yield and quality benefits, resistance risk and human and environmental safety. It also describes the clear technical differences that exist between these active ingredients, particularly in the areas of fungicidal activity and biokinetics.     

Inhibition of resistance plasmid transfer in Escherichia coli by ionophores, chlortetracycline, bacitracin, and ionophore/antimicrobial combinations

Medicinal feed additives bacitracin, chlortetracycline (CTC), laidlomycin, lasalocid, and salinomycin inhibited the transfer of multiresistance-conferring plasmid pBR325 (Tet(r) Amp(r) Cp(r), 6.0 kb) into selected gram-negative strains with the use of an in vitro model. High concentrations of ampicillin-sensitive competence-pretreated Escherichia coli HB 101 cells were exposed to 10% (v/v) of 1:10 dimethyl sulfoxide/agent : water containing test mixtures for 0.5 hr prior to plasmid addition and transforming conditions. Transformation was inhibited for all antimicrobials and showed a positive association wich higher concentration. Additional testing of ionophore compounds separately and in combination with bacitracin, chlortetracycline, lincomycin, roxarsone, tylosin, and virginiamycin at representative feed concentrations demonstrated 80.6% to >99.9% inhibition (P < 0.001) of resistance transfer. Bacitracin alone inhibited transformation within the range of 50-500 ppm. No increase in resistance transfer was observed when poultry-derived and reference gram-negative isolates having low or no transformation efficiency were additionally tested. The results suggest that these compounds, at relevant concentrations used in animal feed, may interfere with cell envelope-associated DNA uptake channels or other transformation competence mechanisms. Through these mechanisms, ionophores and cell membrane-interactive feed agents such as CTC and bacitracin may act to inhibit resistance transfer mechanisms within poultry and livestock.     

Emergency presentations of 4 dogs with suspected neurologic toxoplasmosis

Objective: To review the signalment, clinical signs, abnormal laboratory data, therapeutics, and response to therapy of dogs with clinical signs consistent with toxoplasmosis infection. Series summary: A retrospective review was performed on the records of 4 dogs presented to the Animal Emergency Center between January 1998 and February 2000 exhibiting neurologic signs and having elevated titers for Toxoplasma gondii. A tentative diagnosis of toxoplasmosis was based upon one of the following criteria: (1) a serial 4‐fold or greater change in serum T. gondii IgG titers; 2) serially decreasing serum T. gondii IgM titers with concurrent increasing serum T. gondii IgG titers; or 3) positive cerebrospinal fluid (CSF) T. gondii titers. In addition, inclusion of cases was limited to dogs that showed improvement of neurologic signs following treatment with antiprotozoal drugs. Trimethoprim–sulfamethoxazole treatment was associated with successful elimination of clinical signs in all of the dogs. Two of the dogs developed side effects potentially attributed to the trimethoprim–sulfamethoxazole (TMS), and antiprotozoal treatment was continued using clindamycin. Unique information presented: Toxoplasmosis is an important differential diagnosis in any dog that presents as an emergency with central or peripheral neurologic signs. Affected dogs need not be immunocompromised for clinical signs of toxoplasmosis to occur. Appropriate treatment with TMS or clindamycin can lead to resolution of clinical signs.     

Assessing landscape health by scaling with remote sensing: when is it not enough?

Assessment of the health of landscapes, by monitoring their condition over space and time, is needed to better understand the processes for sustaining or, in many cases, repairing them. Remote sensing is a tool that can efficiently identify and assess areas of landscape damage at different scales and help land managers solve specific problems. Remote sensing may appear to be a panacea for all monitoring situations but sometimes the information it provides is not enough by itself. In this paper we give examples of both scenarios—when remote sensing alone is adequate and when it is not. When remotely sensed data alone is not sufficient, monitoring problems can be solved by incorporating additional finer scale data. We use a five-step procedure based on scaling to help land managers answer the question: when is remote sensing data alone not sufficient to underpin the information needs required to achieve a specific management goal?     

The involvement of mast cells and mast cell proteinases in the intestinal response to equine cyathostomin infection

Cyathostomins (Cyathostominae) are regarded as the most pathogenic equine nematode worldwide. These nematodes are difficult to control in equine populations due to emerging anthelmintic resistance and evasion of encysted larval cyathostomins to regular modern anthelmintics. Mast cells and their proteinases have been shown to play a role in the mammalian immune response to nematode infections. Involvement of mast cells and mast cell proteinases in the equine immune response to cyathostomin infection is proposed. A technique was established to perform immunohistochemical staining using polyclonal rabbit anti-equine mast cell proteinase-1 (eqMCP-1) and anti-equine tryptase on formalin-fixed large intestinal sections, from horses classified as cyathostomin positive and negative at the time of death based upon larval enumeration. Quantitative analysis of antibody labelled mast cells was used to detect mast cell proteinases in equine large intestinal sections positive and negative for cyathostomin larvae. This demonstrated an increase in equine tryptase labelled mucosal and submucosal mast cells in cyathostomin positive horses. This study has established an immunohistochemical technique to demonstrate mast cell proteinases in formalin-fixed large intestinal sections. This technique may be used to determine possible involvement of mast cells and their proteinases in the equine immune response to cyathostomin larvae. Further studies are required to define a specific role.     

Reducing Catfish Farm Losses Due to Dockages Assessed by Processing Plants

Dockages can have a significant effect on catfish, Ictalurus punctatus, farm revenues. This study was conducted to quantify common dockages, examine seasonal and yearly variations in dockages assessed, and determine optimal production practices given various dockage scenarios. A convenience survey of invoice records from 30 commercial catfish farms and 10 processing plants provided 3686 daily catfish load records that were used to quantify dockages. A linear programming model was developed to examine optimal production practices given 11 alternative production scenarios with five size‐grading technologies subject to 24 types and levels of dockages. The survey revealed that 95% of catfish loads delivered to processing plants between 1997 and 2002 were assessed dockages that resulted in average losses of 2.45% per load or $0.066/kg of catfish marketed over the study period. Out‐of‐size discounts constituted the greatest losses. Dockage losses can be reduced by shifting either to longer‐term single‐batch production or more intensive grading. Longer‐term production results in fewer smaller fish that would incur dockage losses. However, cash flow constraints require more intensive early‐season grading. The grader choice depended on the dockage tolerance level and rate, the frequency distribution of sizes of catfish in the population, the efficiency of the grading technology, and the cost of the grading method. Larger farms minimize losses with intensive active grading (University of Arkansas at Pine Bluff grader).