Restoration of the sensitivity of Eimeria acervulina to anticoccidial drugs in the chicken following use of a live coccidiosis vaccine.

The efficacy of the anticoccidial drugs amprolium, clopidol, diclazuril, monensin, monensin + nicarbazin, narasin, narasin + nicarbazin, and salinomycin against field isolates of Eimeria acervulina obtained from a commercial broiler enterprise before and after immunization with a coccidiosis vaccine was investigated. Evaluated by weight gain, feed conversion, and lesion score following challenge, the isolate obtained before vaccination was resistant to all the drugs tested. By contrast, after vaccination the isolate was sensitive to all drugs evaluated by weight gain, and to most drugs judged by feed conversion and lesion score. It is concluded that vaccination had resulted in the restoration of sensitivity to these drugs.

Synergistic effect of a combination of nicarbazin and monensin against coccidiosis in the chicken caused by Eimeria spp.

A clinical study was made into the abilities of nicarbazin and monensin and a nicarbazin + monensin combination to control Eimeria acervulina, E. maxima, and E. tenella in chickens. When included in the feed, at concentrations of 40 ppm nicarbazin or 40 ppm monensin, these products showed partial efficacy evaluated by daily weight gain (DWG) but no activity judged by daily feed intake (DFI) or feed conversion ratio (FCR). By contrast, the combination of 40 ppm nicarbazin + 40 ppm monensin provided complete control of infection judged by greater DWG and DFI, and lower FCR. Monensin at a concentration of 40 ppm was ineffective in preventing lesions caused by all three species. Nicarbazin at a concentration of 40 ppm was unable to suppress lesions of E. acervulina and E. maxima but was able to suppress lesions caused by E. tenella. Nicarbazin 40 ppm + monensin 40 ppm suppressed lesions of all three species. RESEARCH HIGHLIGHTS Nicarbazin or monensin at 40 ppm gave only partial control of Eimeria spp. A combination of 40 ppm nicarbazin + 40 ppm monensin controlled DWG, DFI and FCR. Nicarbazin or monensin at 40 ppm did not suppress all Eimeria spp. lesions. Nicarbazin 40 ppm + monensin 40 ppm suppressed lesions of all three species.

Efficacy of Tylosin and Tilmicosin Against Experimental Mycoplasma gallisepticum Infection in Chickens.

Mycoplasma gallisepticum, the cause of chronic respiratory disease, remains one of the most important pathogens in the poultry industry. Controlling the impact of this disease is done by eradication of positive breeder flocks or by vaccination and medication. Tylosin and tilmicosin are often used in medication programs. However, recent data on the in vivo efficacy of these macrolide antibiotics are scarce. Therefore, two dose titration studies were conducted using a recently isolated M. gallisepticum strain belonging to the wild-type population with regard to its tilmicosin and tylosin minimal inhibitory concentration. In a first trial, broilers were infected with M. gallisepticum and treated with 10 or 20 mg tilmicosin/kg body weight (BW) in the drinking water for five successive days. In a second trial, broilers were infected with M. gallisepticum and treated with 35 or 100 mg tylosin/ kg BW in the drinking water for five successive days. Clinical scoring of respiratory signs, macroscopic scoring of respiratory tract lesions, M. gallisepticum isolation from the respiratory organs, weight gain, and mortality were monitored for efficacy evaluation. All tylosin and tilmicosin treatments significantly reduced the course of clinical respiratory disease, macroscopic lesions in the respiratory organs, and M. gallisepticum numbers in the respiratory tract and obtained higher weight gains compared with the Mycoplasma-infected untreated control group. A treatment of 100 mg tylosin/kg daily for 5 days was not more clinically efficacious than the dosage of 35 mg tylosin/kg daily for 5 days. At final necropsy, in animals treated with 20 mg/kg BW tilmicosin, significantly fewer respiratory tract lesions were present than in the animals treated with 10 mg/kg BW tilmicosin. Therefore, when tilmicosin is used to treat clinical outbreaks of M. gallisepticum in broilers, a dosing scheme of 20 mg tilmicosin/kg BW for five successive days seems to be the most recommended scheme.

Eficacia de la tilosina y la tilmicosina contra la infección experimental por Mycoplasma gallisepticum en pollos. Mycoplasma gallisepticum, la etiología de la enfermedad respiratoria crónica, sigue siendo uno de los patógenos más importantes en la industria avícola. El control del impacto de esta enfermedad se realiza mediante la erradicación de parvadas reproductoras positivas o mediante la vacunación y medicación. La tilosina y la tilmicosina se usan a menudo en programas de medicación. Sin embargo, los datos recientes sobre la eficacia in vivo de estos antibióticos macrólidos son escasos. Por lo tanto, se realizaron dos estudios de titulación de dosis utilizando una cepa de M. gallisepticum recientemente aislada que pertenece a una población de tipo silvestre con respecto a la concentración mínima inhibitoria de tilmicosina y tilosina. En un primer ensayo, los pollos de engorde se infectaron con M. gallisepticum y se trataron con 10 o 20 mg de tilmicosina por kg de peso corporal (BW) en el agua potable durante cinco días sucesivos. En un segundo ensayo, los pollos de engorde se infectaron con M. gallisepticum y se trataron con 35 o 100 mg de tilosina por kg de peso corporal en el agua potable durante cinco días consecutivos. Se registraron las puntuaciones clínicas de los signos respiratorios, las puntuaciones macroscópicas de las lesiones del tracto respiratorio, el aislamiento de M. gallisepticum de los órganos respiratorios, el aumento de peso y la mortalidad para evaluar la eficacia. Todos los tratamientos con tilosina y tilmicosina redujeron significativamente el curso de la enfermedad respiratoria clínica, las lesiones macroscópicas en los órganos respiratorios y los números de M. gallisepticum en el tracto respiratorio y obtuvieron mayores ganancias de peso en comparación con el grupo control no tratado e infectado con Mycoplasma. Un tratamiento de 100 mg de tilosina por kg al día por 5 días no fue más eficaz clínicamente que la dosis de 35 mg de tilosina por kg al día por 5 días. Al final de la necropsia, en animales tratados con 20 mg por kg de peso de tilmicosina, hubo significativamente menos lesiones en el tracto respiratorio que en los animales tratados con 10 mg por kg de peso de tilmicosina. Por lo tanto, cuando la tilmicosina se usa para tratar los brotes clínicos de M. gallisepticum en pollos de engorde, un esquema de dosificación de 20 mg de tilmicosina por kg de peso corporal durante cinco días sucesivos parece ser el esquema más recomendado. Abbreviations: BW = body weight; ccu = color changing units; dpi = days postinoculation; GE = genomic equivalent; MIC = minimal inhibitory concentration; qPCR = quantitative PCR; tylo = tylosin; tilm = tilmicosin.

Predicting wastewater temperatures in sewer pipes using abductive network models.

A predictive modelling technique was employed to estimate wastewater temperatures in sewer pipes. The simplicity of abductive predictive models attracts large numbers of users due to their minimal computation time and limited number of measurable input parameters. Data measured from five sewer pipes over a period of 12 months provide 33,900 training entries and 39,000 evaluation entries to support the models' development. Two simple predictive models for urban upstream combined sewers and large downstream collector sewers were developed. They delivered good correlation between measured and predicted wastewater temperatures proven by their R(2) values of up to 0.98 and root mean square error (RMSE) of the temperature change along the sewer pipe ranging from 0.15 °C to 0.33 °C. Analysis of a number of potential input parameters indicated that upstream wastewater temperature and downstream in-sewer air temperature were the only input parameters that are needed in the developed models to deliver this level of accuracy.

Modelling the viability of heat recovery from combined sewers.

Modelling of wastewater temperatures along a sewer pipe using energy balance equations and assuming steady-state conditions was achieved. Modelling error was calculated, by comparing the predicted temperature drop to measured ones in three combined sewers, and was found to have an overall root mean squared error of 0.37 K. Downstream measured wastewater temperature was plotted against modelled values; their line gradients were found to be within the range of 0.9995-1.0012. The ultimate aim of the modelling is to assess the viability of recovering heat from sewer pipes. This is done by evaluating an appropriate location for a heat exchanger within a sewer network that can recover heat without impacting negatively on the downstream wastewater treatment plant (WWTP). Long sewers may prove to be more viable for heat recovery, as heat lost can be reclaimed before wastewater reaching the WWTP.

Cost optimisation and minimisation of the environmental impact through life cycle analysis of the waste water treatment plant of Bree (Belgium).

An ASM2da model of the full-scale waste water plant of Bree (Belgium) has been made. It showed very good correlation with reference operational data. This basic model has been extended to include an accurate calculation of environmental footprint and operational costs (energy consumption, dosing of chemicals and sludge treatment). Two optimisation strategies were compared: lowest cost meeting the effluent consent versus lowest environmental footprint. Six optimisation scenarios have been studied, namely (i) implementation of an online control system based on ammonium and nitrate sensors, (ii) implementation of a control on MLSS concentration, (iii) evaluation of internal recirculation flow, (iv) oxygen set point, (v) installation of mixing in the aeration tank, and (vi) evaluation of nitrate setpoint for post denitrification. Both an environmental impact or Life Cycle Assessment (LCA) based approach for optimisation are able to significantly lower the cost and environmental footprint. However, the LCA approach has some advantages over cost minimisation of an existing full-scale plant. LCA tends to chose control settings that are more logic: it results in a safer operation of the plant with less risks regarding the consents. It results in a better effluent at a slightly increased cost.

Susceptibility of Clostridium perfringens strains from broiler chickens to antibiotics and anticoccidials.

Clostridium perfringens strains isolated in 2002 from the intestines of broiler chickens from 31 different farms located in Belgium were tested for susceptibility to 12 antibiotics used for therapy, growth promotion or prevention of coccidiosis. All strains were uniformly sensitive to the ionophore antibiotics monensin, lasalocid, salinomycin, maduramycin and narasin. All were sensitive to avilamycin, tylosin and amoxicillin, while flavomycin (bambermycin) showed low or no activity. Chlortetracycline and oxytetracycline were active at very low concentrations, but low-level acquired resistance was detected in 66% of the strains investigated. Fifty percent of these strains carried the tetP(B) resistance gene, while the tet(Q) gene was detected in only one strain. One strain with high-level resistance against tetracyclines carried the tet(M) gene. Sixty-three percent of the strains showed low-level resistance to lincomycin. The lnu(A) and lnu(B) genes were each only found in one strain. Compared with a similar investigation carried out in 1980, an increase was seen in resistance percentages with lincomycin (63% against 49%) and a slight decrease with tetracycline (66% against 74%).