Virulence of two entomopathogenic nematode species, Steinernema sp. (strain PQ16) and Heterorhabditis indica (strain KT3987), to nymphs of the coffee cicada Dundubia nagarasingna

Summary The virulence and efficacy of two species of entomopathogenic nematodes, Steinernema sp. (strain PQ16) and Heterorhabditis indica (strain KT3987), against nymphs of the coffee cicada, Dundubia nagarasingna, was evaluated under laboratory and glasshouse conditions. The highest mortality rates of coffee cicada nymphs caused by these two nematode strains were 93.5 and 100%, respectively, at an inoculation dose of 600 infective juveniles (IJ) nymph−1. The virulence (LC50) was established as 137.5 IJ and 149.1 IJ for strains S-PQ16 and H-KT3987, respectively. The highest IJ yields of these nematode strains were 66 × 103 IJ (for S-PQ16) and 134.4 × 103 IJ (for H-KT3987) at a dose of 500 IJ nymph−1. The efficacies of the two nematode strains to coffee cicadas at treated dose of 60 × 103 IJ pot−1 were 84.4 and 88.9% after 30 days, higher than the efficacies at treated dose of 40 × 103 IJ pot−1. The number of IJ in 250 ml of soil at 10, 20 and 30 days after treatment, increased from 0.38 × 103 to 4.80 × 103 IJ in soil treated with a dose of 40 × 103 IJ and from 0.66 × 103 to 5.02 × 103 IJ in soil treated with a dose of 60 × 103 IJ (for S-PQ16). Similarly, for H-KT3987 the number of IJ increased from 0.43 × 103 to 8.99 × 103 IJ and from 0.62 × 103 to 9.64 × 103 IJ, at the respective doses. Based on results of a pot trial from glasshouse modelling, an IJ application dosage for biological control of coffee cicada nymphs in coffee plantations was proposed.

Swabs as a Tool for Monitoring the Presence of Norovirus on Environmental Surfaces in the Food Industry

Human norovirus (HuNoV), which causes gastroenteritis, can be transmitted to food and food contact surfaces via virus-contaminated hands. To investigate this transmission in food processing environments, we developed a swabbing protocol for environmental samples, evaluated the stability of HuNoV in the swabs, and applied the method in the food industry. Swabs made of polyester, flocked nylon, cotton wool, and microfiber were moistened in either phosphate-buffered saline (PBS) or glycine buffer (pH 9.5) and used to swab four surfaces (latex, plastic, stainless steel, and cucumber) inoculated with HuNoV. HuNoV was eluted with either PBS or glycine buffer and detected with quantitative reverse transcription PCR. HuNoV recoveries were generally higher with an inoculation dose of 100 PCR units than 1,000 PCR units. The highest recoveries were obtained when surfaces were swabbed with microfiber cloth moistened in and eluted with glycine buffer after a HuNoV inoculation dose of 100 PCR units: 66% ± 18% on latex, 89% ± 2% on plastic, and 79% ± 10% on stainless steel. The highest recovery for cucumber, 45% ± 5%, was obtained when swabbing the surface with microfiber cloth and PBS. The stability of HuNoV was tested in microfiber cloths moistened in PBS or glycine buffer. HuNoV RNA was detected from swabs after 3 days at 4 and 22°C, although the RNA levels decreased more rapidly in swabs moistened with glycine buffer than in those moistened with PBS at 22°C. In the field study, 172 microfiber and 45 cotton wool swab samples were taken from environmental surfaces at three food processing companies. Five (5.6%) of 90 swabs collected in 2010 and 7 (8.5%) of 82 swabs collected in 2012 were positive for HuNoV genogroup II; all positive samples were collected with microfiber swabs. Three positive results were obtained from the production line and nine were obtained from the food workers' break room and restroom areas. Swabbing is a powerful tool for HuNoV RNA detection from environmental surfaces and enables investigation of virus transmission during food processing.