Stage specific mortality and humoral immune responses during pulse and trickle infestations of the common cattle grub, Hypoderma lineatum (Diptera: Oestridae)

Abstract

Stage specific survival of larvae and pupae of the common cattle grub, Hypoderma lineatum de Villers, was compared in cattle artificially infested with larvae delivered by subcutaneous injection as a single infestation of 100 larvae, in trickle infestations of either two doses of 50 larvae, separated by 15 days, or in four doses of 25 larvae, separated by 9, 6, and 6 days, respectively. The duration of the migratory and ‘warble’ phases were also compared between treatments. The kinetics of the antibody response was monitored throughout the larval development by ELISA. No difference was noted in the level of antibodies among the three treatments. Mortality of first-instars differed among the infestation groups with mortality in the single pulse infestation group<two dose trickle infestation<four dose trickle infestation. A similar trend was seen in second and third instar mortality. These data suggest that host immune responses are activated by the first larvae to enter the animal and that this activation negatively affects the later arriving larvae. This may have consequences for the population biology of cattle grubs and suggests that synchronization of the adult stages is important to the survival of larval stages in the hosts.