- Biostatistician with bioinformatic skills with interest in epidemiology and genetic modelsedit
Before interventions to control horizontal transmission of Mycoplasma gallisepticum can be tested, a suitable experimental model should be available. Transmission dynamics in a flock can be quantified by two parameters: the average number... more
Before interventions to control horizontal transmission of Mycoplasma gallisepticum can be tested, a suitable experimental model should be available. Transmission dynamics in a flock can be quantified by two parameters: the average number of secondary cases infected by one typical infectious case (R0) and the number of new infections that occur due to one infectious animal per unit of time (beta). The transmission dynamics of M. gallisepticum have not been studied experimentally, so the aim of this study was to examine the horizontal transmission of M. gallisepticum. The study was carried out using a pairwise design with three different inoculation doses. Every pair consisted of an inoculated chicken and a susceptible in-contact chicken. Five susceptible individually housed chickens were placed in between pairs in order to measure airborne transmission. Infection was detected by serology, quantitative polymerase chain reaction and culture. The inoculated and in-contact chickens were...
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Resistance to coccidiostats and possible future restrictions on their use raise the need for alternative methods of reducing coccidiosis in poultry. The aim of this study was to evaluate the effect of selected phytochemicals on Eimeria... more
Resistance to coccidiostats and possible future restrictions on their use raise the need for alternative methods of reducing coccidiosis in poultry. The aim of this study was to evaluate the effect of selected phytochemicals on Eimeria tenella sporozoite invasion in vitro. Four phytochemicals were selected on the basis that they reduce the virulence of Eimeria spp. and/or provide immune modulatory benefits to host cells: betaine, carvacrol, curcumin and Echinacea purpurea extract (EP). Madin-Darby bovine kidney (MDBK) cells were covered by medium containing phytochemicals at the highest concentration which was non-toxic to the cells. Salinomycin 50 μg/ml was positive control; negative control was medium only. E. tenella (Houghton strain) sporozoites were added to wells and after incubation for 2, 4 or 20 h at 37°C, cells were fixed and stained with hematoxylin-eosin. Ten evenly spaced fields per well were photographed and the percentage of cells invaded by sporozoites was calculated and normalized to the control. At 2h, carvacrol, curcumin and EP showed a significantly lower percentage of sporozoite invasion than the untreated control; in contrast, betaine treatment represented a significantly higher invasion percentage. Combining carvacrol with EP inhibited E. tenella invasion more effectively than applying the compounds individually, but the further addition of curcumin did not reduce invasion further. In conclusion, this study shows that invasion of MDBK epithelial cells by E. tenella sporozoites is inhibited in the presence of carvacrol, curcumin, or EP and enhanced by betaine. There may be potential for developing these phytochemicals as anti-coccidial feed or water additives for poultry.
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Research Interests:
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Research Interests: Microbiology, Industrial Biotechnology, Food Microbiology, Bayesian Analysis, Bayesian Inference, and 16 moreHumans, Campylobacter, Animals, Risk factors, Gold Standard, Chickens, Feces, Latent Class Analysis, Food Contamination, Food Sciences, Risk Factors, Statistical Model, Bayes Theorem, Sensitivity and Specificity, Condition dependence, and False Negative
The aim of this study was to determine the association between farm management factors, including antimicrobial drug usage, and resistance in commensal Escherichia coli isolates from the faeces of white veal calves. Ninety E. coli... more
The aim of this study was to determine the association between farm management factors, including antimicrobial drug usage, and resistance in commensal Escherichia coli isolates from the faeces of white veal calves. Ninety E. coli isolates from one pooled sample per farm (n = 48) were tested for their phenotypical resistance against amoxicillin, tetracycline, cefotaxime, ciprofloxacin and trimethoprim/sulfamethoxazole (TMP/SMX). Logistic regression analysis revealed the following risk factors (P < 0·05); farmer wearing the same work clothes for several days [ciprofloxacin, odds ratio (OR) 2·6; tetracycline, OR 2·4], administration of trimethoprim-sulfonamide combinations (TMP/SMX, OR 3·0; amoxicillin, OR 3·1; tetracycline, OR 2·6), ⩾0·3 animal daily dosage per production cycle (ADD/pc), quinolones (ciprofloxacin, OR 2·8), ⩾1·3 ADD/pc, penicillins (ciprofloxacin, OR 3·3; tetracycline, OR 3·4), 20-40 ADD/pc, tetracyclines (tetracycline, OR 3·2) and >40 ADD/pc, tetracyclines (tetracycline, OR 13·1; amoxicillin, OR 6·5). In this study antimicrobial resistance in commensal E. coli was mainly associated with antimicrobial drug use.
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The effect of an inactivated vaccine on the horizontal transmission of Mycoplasma gallisepticum was quantified in a transmission model. Twenty non-vaccinated and 20 vaccinated 23-week-old specific pathogen free hens were housed in pairs,... more
The effect of an inactivated vaccine on the horizontal transmission of Mycoplasma gallisepticum was quantified in a transmission model. Twenty non-vaccinated and 20 vaccinated 23-week-old specific pathogen free hens were housed in pairs, while five individually housed hens acted as a negative control group. Each pair consisted of a challenged chicken (10(4) colony forming units intratracheally) and a non-challenged susceptible contact bird. Infection was monitored by serology, quantitative polymerase chain reaction and culture. All non-vaccinated and vaccinated in-contact chickens became infected with M. gallisepticum. The 95% confidence interval of the reproduction ratio, R (a measure of transmission defined as the average number of secondary cases caused by one infectious individual) was 4.48 to infinity in both groups. However, the logarithm of the area under the curve in the vaccinated group was 0.51 lower (P = 0.02) than in the non-vaccinated group, indicating that there was an effect of vaccination on the levels of potential shedding of M. gallisepticum. Nevertheless, the results of this study indicate that the use of an inactivated M. gallisepticum vaccine will not reduce the horizontal transmission of M. gallisepticum between laying hens.
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The effect of a live Mycoplasma gallisepticum vaccine on the horizontal transmission of this Mycoplasma species was quantified in an experimental animal transmission model in specific pathogen free White Layers. Two identical trials were... more
The effect of a live Mycoplasma gallisepticum vaccine on the horizontal transmission of this Mycoplasma species was quantified in an experimental animal transmission model in specific pathogen free White Layers. Two identical trials were performed, each consisting of two experimental groups and one control group. The experimental groups each consisted of 20 birds 21 weeks of age, which were housed following a pair-wise design. One group was vaccinated twice with a commercially available live attenuated M. gallisepticum vaccine, while the other group was not vaccinated. Each pair of the experimental group consisted of a challenged chicken (10(4) colony-forming units intratracheally) and a susceptible in-contact bird. The control group consisted of 10 twice-vaccinated birds housed in pairs and five individually housed non-vaccinated birds. The infection was monitored by serology, culture and quantitative polymerase chain reaction. The vaccine strain and the challenge strain were distinguished by a specific polymerase chain reaction and by random amplified polymorphic DNA analysis. In both experiments, all non-vaccinated challenged chickens and their in-contact 'partners' became infected with M. gallisepticum. In the vaccinated challenged and corresponding in-contact birds, a total of 19 and 13 chickens, respectively, became infected with M. gallisepticum. Analysis of the M. gallisepticum shedding patterns showed a significant effect of vaccination on the shedding levels of the vaccinated in-contact chickens. Moreover, the Cox Proportional Hazard analysis indicated that the rate of M. gallisepticum transmission from challenged to in-contact birds in the vaccinated group was 0.356 times that of the non-vaccinated group. In addition, the overall estimate of R (the average number of secondary cases infected by one typical infectious case) of the vaccinated group (R = 4.3, 95% confidence interval = 1.6 to 49.9) was significantly lower than that of the non-vaccinated group (R = infinity, 95% confidence interval = 9.9 to infinity). However, the overall estimate of R in the vaccinated group still exceeded 1, which indicates that the effect of the vaccination on the horizontal transmission M. gallisepticum is insufficient to stop its spread under these experimental conditions.