The impact of botfly parasitism on the health of the gracile mouse opossum (Gracilinanus agilis) (original) (raw)
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The impact of botfly parasitism on the health of the gracile mouse opossum (Gracilinanus agilis)
Parasitology, 2019
Fragmented habitats generally harbour small populations that are potentially more prone to local extinctions caused by biotic factors such as parasites. We evaluated the effects of botflies (Cuterebra apicalis) on naturally fragmented populations of the gracile mouse opossum (Gracilinanus agilis). We examined how sex, food supplementation experiment, season and daily climatic variables affected body condition and haemoglobin concentration in animals that were parasitized or not by botflies. Although parasitism did not affect body condition, haemoglobin concentrations were lower in parasitized animals. Among the non-parasitized individuals, haemoglobin concentration increased with the increase of maximum temperature and the decrease of relative humidity, a climatic pattern found at the peak of the dry season. However, among parasitized animals, the opposite relationship between haemoglobin concentration and relative humidity occurred, as a consequence of parasite-induced anaemia inte...
Journal of Mammalogy, 2022
Botflies (Diptera: Cuterebra sp.) are widely distributed and seasonally abundant parasites of small mammals in North America. To assess their effect on rodent survival, we studied the demography of botfly parasitism on small mammals in northeastern Kansas during 1995-1999. Additional comparisons on botflies parasitizing small mammals were made to a nearby old-field grid where mark-recapture studies continued from 1975 to 2003. White-footed mice, Peromyscus leucopus, were infected by botfly larvae (Cuterebra fontinella) each year during our study. The period of infection for P. leucopus was June-December, with the highest proportion of mice infected in July and August. A smaller, second peak of infection in October and November indicated that C. fontinella reproduced bimodally at this latitude with distinct summer and autumn population peaks. During the botfly seasons of the 5 years, 140 (23.3%) of 602 P. leucopus captured were infected. The percentages of individuals infected during 1995, 1996, 1997, and 1999 were not significantly different (22.4%, 17.3%, 17.1%, and 22.7%, respectively). However, in 1998, 32.4% individuals were infected with a higher incidence of multiple infections and a greater number of botfly larvae per host. Nearly half (47%) of the infected individuals caught in 1998 had infections in both summer and autumn, compared with 25% during the 1995-1997 seasons. In 1999, 63% of infected mice had at least a 2nd infection during the autumn. For all 5 years, 82%, 14%, and 4% of the infected mice had one, two, or three botflies, respectively. In 1998, 24% of the infected mice carried two or more botflies at one time, compared to 14% from 1995-1997 and 11% in 1999. Overall 94% of the infected mice were adults, with no differences between sexes. The variation seen in the prevalence of botfly parasitism of whitefooted mice correlates to yearly weather fluctuations. Other demographic aspects of the infected mice, such as sex ratio, age, and longevity of those infected, did not change year to year. Our data suggest that infection with Cuterebra has little negative or positive impact upon populations of white-footed mice.
A PRESCRIPTION FOR LONGER LIFE? BOT FLY PARASITISM OF THE WHITE-FOOTED MOUSE
Ecology, 2005
Investigation of host-parasite interactions typically reveals a negative impact of parasitism on the host species. In contrast, mounting evidence indicates that bot fly (Cuterebra sp.) infestation enhances the survival of white-footed mice (Peromyscus leucopus). We propose that life history trade-offs, namely, between reproduction and survival, can explain this counterintuitive observation. By using an extensive data set spanning a decade, 12 sites in two states, and over 30 000 mouse captures, we offer a new perspective on the effects of bot fly parasitism on white-footed mice. Analysis of persistence time corroborated earlier studies that showed significantly higher survival rates of infested mice. Although a higher proportion of infested than uninfested females were in breeding condition, secondary reproductive success appeared to be negatively impacted by parasitism via declines in the number of litters and the total number of offspring produced by infested females. Population growth rates were negatively correlated with infestation prevalence, further indicating a negative effect of parasitism. Based on the negative impact of parasitism on reproduction, we propose that enhanced survival of infested mice can be explained by the diversion of resources from reproduction to body maintenance. Parasite-induced life history shifts in which mice decrease current reproduction to promote future reproduction, such as increasing the age at maturity, may also contribute to the decline in population growth rate observed in years of high infestation prevalence.
Bot flies are common parasites of Peromyscus leucopus, although determination of a cost to the host has been elusive. The goal of this study was to further explore the potential costs of bot fly parasites for a population of P. leucopus. We investigated the effects of parasitism on host condition (mass after controlling for parasite mass and host body length) and survivorship (the number of days animals persisted on trapping grids). Parasitism was quantified by prevalence (proportion of the population infected), intensity (the number of parasites per infected host), and dispersion of parasites within hosts (clumped, regular, or random). In addition, we searched for spatial and temporal patterns in infection. Finally, we analyzed the relationship between population demography and parasitism. Contrary to expectations, we found that infected mice persisted longer on trapping grids and were in better condition than uninfected mice. Also, we discovered that when considering overall infection levels, parasites were clumped within hosts, but when considering the number of simultaneous infections, parasites were randomly distributed among hosts. Although most animals had single infections, there was a high incidence of reinfections, leading to bimodal patterns of parasitism. Prevalence was not correlated with host density, sex ratio, or proportion reproductive, but there were significant relationships between intensity and density and sex ratio in 1 year. In addition, prevalence and proportion of reproductively active animals were asynchronous. These results suggest that bot flies do not impose an obvious cost to their hosts, and hosts may express some degree of tolerance for bot fly parasitism.
Journal of mammalogy, 1997
I tested the hypothesis that infestation by botflies (Cuterebra) is male-biased and related to increased movement in the rock mouse (Peromyscus difficUis) during 2 full-annual cycles. During both years, adult females were more heavily infested in autumn, but adult males were more heavily infested in winter. Rates of infestation were negatively related to movements of animals. Females had higher infestation in the breeding season when they move less, whereas males had higher infestation in the non-breeding season. In grids with supplemental feod, higher rates of infestation occurred among individuals, especially females, that used traps near food stations.
Infestation of Rock Mice (Peromyscus difficilis) by Botflies: Ecological Consequences of Differences Between Sexes., 1997
I tested the hypothesis that infestation by botflies (Cuterebra) is male-biased and related to increased movement in the rock mouse (Peromyscus difficUis) during 2 full-annual cycles. During both years, adult females were more heavily infested in autumn, but adult males were more heavily infested in winter. Rates of infestation were negatively related to movements of animals. Females had higher infestation in the breeding season when they move less, whereas males had higher infestation in the non-breeding season. In grids with supplemental feod, higher rates of infestation occurred among individuals, especially females, that used traps near food stations.
Mammalia, 2000
Myiases by cuterebrid botflies can compromise the reproductive activities and survival of the infected hosts. We examined the effects of parasitism by cuterebrid botflies (Metacuterebra apicalis) on the reproduction, survival and general health of the rice-rat, Oryzomys russatus. This study was carried out in an Atlantic forest of southeastern Brazil from February, 1993 through January, 1995. The prevalence of botfly myiases in O. russatus was highly seasonal, increasing during the warm, humid months and decreasing during the cold, dry months. Male hosts were infected significantly more often than females, but our results suggests that the survival, general health and reproduction of O. russatus were not altered by the parasitism of M. apicalis. Resume.-Les myiases dues ä des Dipteres Cuterebrides peuvent compromettre la reproduction et la survie des hötes infestes. Nous examinons l'effet du parasitisme par ces mouches (Metacuterebra apicalis) sur la bonne sante generale & Oryzomys russatus. Cette etude a ete entreprise dans les forets atlantiques du sud-est du Bresil, de fevrier 1993 ä Janvier 1995. La prevalence de cette myiase chez O. russatus a ete nettement saisonniere, augmentant au cours des mois chauds et humides, et diminuant au cours des mois froids et sees. Les notes males ont ete infectes, de maniere significative, plus souvent que les femelies, mais nos resultats suggerent que la survie, la bonne sante generale et la reproduction de O. russatus n Ont pas ete alterees par ce parasitisme.
Does the host matter? Variable influence of host traits on parasitism rates
Parasitism of mammals is ubiquitous, but the processes driving parasite aggregation on hosts are poorly understood, as each system seems to show unique correlations between parasitism and host traits such as sex, age, size and body mass. Genetic diversity is also posited to influence susceptibility to parasitism, and provides a quantifiable measure of an intrinsic unchanging host property, but this link has not been well established. A lack of consistency in host traits predicting parasite heterogeneity may derive from the contribution of environmental factors to parasite aggregation. To evaluate this question, a large data- set was leveraged to explore the relationship between unchanging, intrinsic host traits (heterozygosity and sex), variable host traits (age, length and body mass), and extrinsic factors (sampling date/year and population) and flea presence/absence, abundance and intensity on two species of social burrowing mammal, the black-tailed prairie dog (Cynomys ludovicianus) and the Gunnison’s prairie dog (Cynomys gunnisoni). Prairie dogs experience frequent parasitism by fleas, but the distribution of fleas among indi- viduals is highly skewed. In these systems, intrinsic host traits were nuanced in how they predicted flea aggregation on individual prairie dogs, with sex unimportant to parasitism rates and heterozygosity increasing the probability of infection and influencing the number of fleas in divergent ways. Variable host traits interacted with each other and with environmental or geographic stochasticity to influence flea aggregation. Length and age tended to increase parasitism, whereas the effects of body mass and con- dition were mediated by date and other host traits to produce both positive and negative effects on par- asitism. This finding suggests that the factors affecting ectoparasite infection on individuals are complex, even within species. Importantly, there was no correlation between the number of fleas on an individual in one year and the number of fleas on the same individual the next year, supporting the idea that flea aggregation is not driven by unchanging, intrinsic characteristics of the host. Rather, these findings indi- cate that host traits influence parasitism in nuanced ways, including interactions with environmental characteristics and stochastic factors.
Naturwissenschaften, 2009
Deviance partitioning can provide new insights into the ecology of host-parasite interactions. We studied the host-related factors influencing parasite prevalence, abundance, and species richness in European brown hares (Lepus europaeus) from northern Spain. We defined three groups of explanatory variables: host environment, host population, and individual factors. We hypothesised that parasite infection rates and species richness were determined by different host-related factors depending on the nature of the parasite (endo-or ectoparasite, direct or indirect life cycle). To assess the relative importance of these components, we used deviance partitioning, an innovative approach. The explained deviance (ED) was higher for parasite abundance models, followed by those of prevalence and then by species richness, suggesting that parasite abundance models may best describe the host factors influencing parasitization. Models for parasites with a direct life cycle yielded higher ED values than those for indirect life cycle ones. As a general trend, host individual factors explained the largest proportion of the ED, followed by host environmental factors and, finally, the interaction between host environmental and individual factors. Similar hierarchies were found for parasite prevalence, abundance, and species richness. Individual factors comprised the most relevant group of explanatory variables for both types of parasites. However, host environmental factors were also relevant in models for indirect life-cycle parasites. These findings are consistent with the idea of the host as the main habitat of the parasite; whereas, for indirect life-cycle parasites, transmission would be also modulated by environmental conditions. We suggest that parasitization can be used not only as an indicator of individual fitness but also as an indicator of environmental quality for the host. This research underlines the importance of monitoring parasite rates together with environmental, population, and host factors.