Wipfelkrankheit : modification of host behaviour during baculoviral infection

Abstract

Infection with an endoparasite frequently alters host behaviour. This study provides the first quantification of larval behaviour in a baculovirus/ Lepidoptera system, and attempts to assess the ecological consequences of behavioural modification during infection. Larvae of the moth Mamestra brassicae (Lepidoptera: Noctuidae) exhibited higher rates of dispersal in the laboratory and field when infected with Mamestra brassicae nuclear polyhedrosis virus (MbNPV) than did uninfected larvae. They adopted positions at death which were not characteristic of healthy larvae, climbing higher on the foodplant and onto the top and edge of leaves. The horizontal and vertical distribution of virus following larval lysis and the effects of rainfall on this distribution were assessed for comparison with the distributions of healthy and infected larvae. Exposure to rainfall increased the infectivity of vegetation in bioassays. Alternative explanations for the evolutionary origins of behavioural modification are considered. I suggest that the behavioural changes observed are most likely to benefit the virus. In particular, climbing prior to death is likely to result in contamination of more foliage with virus particles than would otherwise occur by increasing exposure of cadavers to rainfall. Thus it may profoundly influence horizontal transmission and the dynamics of the host-virus interaction.

Comparative electrophoretic profile of proteins and esterases in healthy silkworm larvae ( Bombyx mori Lineu, 1758) and infected with nucleopolyhedrovirus

“…These authors proposed that the modern baculovirus may have acquired ptp gene from an ancestral host and that this gene was selectively maintained because it increases virus transmission. These results support the Goulson (1997) hypothesis.…”

“…The baculovirus life cycle is peculiar because it produces two types of infectious progenies with different functions, but essential to natural propagation. The occluded form of the virus (PDV) is responsible for the transmission from insect to insect, while the nonoccluded form (BV) is responsible for transmission from cell to cell, in a same individual (systemic infection) (GRANADOS;FEDERICI, 1986 According to Castro et al (1999) after 80 to 100 hours of infection, there is the discoloration of insect's tegument in several hosts. After death, the insect usually breaks up easily, releasing great amount of polyhedrons into the atmosphere, which in turn will infect new larval populations of the host insect.…”

Baculovirus infection triggers a positive phototactic response in caterpillars: a response to Dobson et al . (2015)

“…Since first described by Hofmann [2], many studies have demonstrated that baculovirus-infected larvae (i) disperse over larger areas than uninfected larvae (hyperactivity) and (ii) die at elevated positions, typically the tops of trees or plants (tree-top disease) [2][3][4][5][6][7][8][9][10][11][12][13]. These behavioural manipulations have been described for several baculovirus-larvae systems and may increase viral spread, as virus will rain down plant foliage.…”

Baculovirus-Encoded Protein BV/ODV-E26 Determines Tissue Tropism and Virulence in Lepidopteran Insects

“…Occlusion-derived viruses (ODVs), which are occluded in occlusion bodies (OBs), transmit virus from insect to insect via oral infection, whereas budded viruses (BVs) spread infection to neighboring cells (16,37). At the late stage of infection, a markedly enhanced locomotion behavior of infected larvae is observed (15,25), which is followed by a dramatic degradation of the host cadaver (11).…”