Salmonella enterica is an important food borne pathogen that is frequently carried by swine. Carrier animals pose a food safety risk because they can transmit S. enterica to finished food products in the processing plant or by contamination of the environment. Environmental contamination has become increasingly important as non-animal foods (plant-based) have been implicated as sources of S. enterica. The prevalence of S. enterica in swine is high and yet carrier animals remain healthy. S. enterica has developed a highly sophisticated set of virulence factors that allow it to adapt to host environments and to cause disease. It is assumed that S. enterica also has developed unique ways to maintain itself in animals and yet not cause disease. Here we describe our research to understand persistence. Specifically, data are presented that demonstrates that detection of most carrier animals requires specific stresses that cause S. enterica to be shed from pigs. As well, we describe a phenotypic phase variation process that appears to be linked to the carrier state and a complex set of factors that control phenotypic phase variation. Finally, we describe how the composition of the gut bacterial microbiome may contribute to persistence and at the least how S. enterica might alter the composition of the gut bacterial microbiome.

The effects of larval population density and food quality on the velvetbean caterpillar, Anticarsia gemmatalis Hübner, were compared with investigations of other migratory noctuids. Crowded larvae of the velvetbean caterpillar responded with: (1) an increase in the degree of dark pigmentation; (2) a decrease in larval, pupal and adult size; (3) a prolongation of the larval stage and a decrease in weight gain in the ultimate stadium; and (4) low juvenile hormone and juvenile hormone esterase haemolymph titres.

The effects of flight, throughout a 4 hr flight period, on the haemolymph titres and whole body contents of carbohydrate and lipid are presented for the velvetbean caterpillar and discussed relative to other noctuid moths. Total carbohydrate concentration decreased during the first 30–45 min of flight, and total fatty acid concentration increased during the first 30–60 min of flight, after which it declined and stabilized at preflight levels. Lipid reserves and the small amount of lipid depletion after long periods of flight indicated that velvetbean caterpillar adults are capable of making long distance movements in which lipid is the principal flight fuel.

Juvenile hormone regulated the effect of density on larval colour, size and growth rate. Applications of juvenile hormone to crowded larvae increased the proportion of the lighter (green), larger and faster developing phase. This hormone action suggests that the juvenile hormone titre of crowded larvae is lower than that of uncrowded larvae.

Genetic differentiation among populations of velvetbean caterpillars suggests that south-central United States populations originate from overwintering populations in Mexico or south Texas. A system has been developed, using pheromone-baited bucket-type traps, to investigate the population dynamics and migration of the velvetbean caterpillar in Louisiana and Texas.