Human toxocariasis is a neglected tropical disease, which is actually global in distribution and has a significant impact on global public health. The infection can lead to several serious conditions in humans, including allergic, ophthalmic and neurological disorders such as epilepsy. It is caused by the common roundworm species Toxocara canis and Toxocara cati, with humans becoming accidentally infected via the ingestion of eggs or larvae. Toxocara eggs are deposited on the ground when infected dogs, cats and foxes defecate, with the eggs contaminating crops, grazing pastures, and subsequently food animals. However, transmission of Toxocara to humans via food consumption has received relatively little attention in the literature. To establish the risks that contaminated food poses to the public, a renewed research focus is required. This review discusses what is currently known about food-borne Toxocara transmission, highlighting the gaps in our understanding that require further attention, and outlining some potential preventative strategies which could be employed to safeguard consumer health.

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Background Toxocara canis and Toxocara cati are intestinal parasites of dogs, cats and foxes, with infected animals shedding eggs of the parasite in their faeces. If humans accidentally ingest embryonated Toxocara spp. eggs from the environment, severe clinical consequences, including blindness and brain damage, can occur. Previous work has demonstrated the presence of Toxocara spp. eggs on vegetable produce grown in the UK, but only in small-scale community gardens. The aim of this study was to determine whether Toxocara spp. eggs are also present on vegetables grown on commercial farms in the UK, which supply produce to a greater number of people. Methods A total of 120 samples (300 g each) of spinach (Spinacia oleracea) were collected across four farms in the south of England, UK. The samples were processed using a sieving approach followed by multiplex quantitative polymerase chain reaction analysis. Results Overall, 23.0% of samples were positive for T. canis (28/120; 95% confidence interval 16.7–31.7%) and 1.7% for T. cati (2/120; 95% confidence interval 0.5–5.9%). There was a statistically significant difference in the number of positive samples between farms (P = 0.0064). To our knowledge, this is the first report of the isolation of Toxocara spp. from vegetables grown on commercial farms in the UK. Conclusions The results of this study highlight the requirement for the thorough washing of vegetables prior to their consumption, especially those such as spinach which may be eaten without first peeling or cooking, and effective farm biosecurity measures to minimise access to farmland by definitive host species of Toxocara spp. Graphical Abstract

Commercial poultry rearing systems often house successive flocks of birds with limited between-flock cleaning of the poultry houses. Previous research focused on opportunities for successive flocks to become colonised with pathogenic bacterial species. However, there is a paucity of information regarding the transfer and persistence of commensal bacterial between flocks, and if this might confer health benefits on subsequent flocks. The work presented here utilised 16S community sequencing to characterise the development of the microbial flora of commercially reared broiler chickens and turkeys to determine microbial environmental persistence. DNA was isolated from caecal contents, faeces, and various bedding samples collected from nine sites over a nine month period. Samples were taken from houses used for rearing chickens or turkeys or where alternating chicken and turkey flocks were reared. Measures of alpha diversity for the different samples suggested that both chickens and turkeys had a similar microbiota. Unsurprisingly, members of the microflora could also be found in the environmental samples tested, although survival was dependent on the phyla and bedding material. Further analysis of the samples is currently underway, in order to determine the extent, if any, of microbial transfer between flocks, with a particular focus on potential poultry microbiota species differences. This study demonstrated how commensal microbes are able to persist within poultry rearing sheds and if this transfer impacts on subsequent flock performance. Alongside increasing understanding of microbial environmental persistence, the work also shows how effective current biosecurity methods are in controlling the transfer of all microbes, including pathogens.