Long-term epidemiology, effect on body condition and interspecific interactions of concomitant infection by nasopharyngeal bot fly larvae (Cephenemyia auribarbis and Pharyngomyia picta, Oestridae) in a population of Iberian red deer (Cervus elaphus hispanicus).

We studied the pattern of infection and the inter-annual variation and individual factors affecting the infection of 2 species of nasopharyngeal bot flies, Cephenemyia auribarbis and Pharyngomyia picta (Diptera: Oestridae), in a population of Iberian red deer (Cervus elaphus hispanicus) from south central Spain (10 annual periods between 1990 and 2003). Mean prevalence+/-S.E.95%CI of infection was 35.19+/-4.24% (n=486). The frequency distribution of the parasites was markedly aggregated (K: 0.213, mean abundance+/-S.D.: 5.49+/-12.12). Parasite load of Oestridae peaked at calf and subadult age groups and declined thereafter, which suggests that acquired immunity may be acting. In common with other host-parasite relationships, male hosts were found to have higher prevalence and abundance levels than females. The prevalence of P. picta was positively affected by the presence of C. auribarbis whereas the intensity of infection of P. picta was negatively affected by the presence of C. auribarbis. Intensity of P. picta in concomitant infections with C. auribarbis was lower than in pure P. picta infections, whilst the intensity of C. auribarbis infections did not change. This provides good evidence of interspecific competence, which could be dealt with by parasites by means of asynchronous life-cycles and different maturation periods. Weather also affects the dynamics and transmission rates of these parasites. Previous annual rainfalls positively affected the level of infection with oestrids. Yearly autumn rainfalls affected positively P. picta, possibly due to an effect on the pupal stage survival. Infection of Oestridae affected body condition in calves and subadults, suggesting that oestrids could have sublethal effects on Iberian red deer. Future research is needed to investigate the effect of parasites on the dynamics of the Iberian red deer.