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1.
The impact of refugees on the health status and health services of host communities: Compounding bad with worse? 总被引:1,自引:0,他引:1
Dick B 《Disasters》1985,9(4):259-269
Although there have been a number of recent developments in our understanding of refugee health problems that have influenced policies and action, the effects of refugees on the health status and services of host communities remain relatively neglected. This article sets out to explain why this is an important issue with implications for policy, planning surveillance and evaluation, training and research.
The first sections outline some of the problems facing host governments and communities in Africa and discuss the changing rhetoric between the first and second International Conferences for Assistance to Refugees in Africa. A number of possible ways in which refugees could affect the individual, agent and environmental causes of disease are considered, as are the characteristics of the refugees, the host communities and the response which may all modify this impact.
Policy implications of the impact of the refugees, both negative and positive, are discussed, and detailed consideration is given to the pros and cons of integrated and parallel approaches to health care provision. The need to monitor carefully the health status and services of host communities is emphasized and recommendations are made for this and other essential developments relating to training and research. 相似文献
The first sections outline some of the problems facing host governments and communities in Africa and discuss the changing rhetoric between the first and second International Conferences for Assistance to Refugees in Africa. A number of possible ways in which refugees could affect the individual, agent and environmental causes of disease are considered, as are the characteristics of the refugees, the host communities and the response which may all modify this impact.
Policy implications of the impact of the refugees, both negative and positive, are discussed, and detailed consideration is given to the pros and cons of integrated and parallel approaches to health care provision. The need to monitor carefully the health status and services of host communities is emphasized and recommendations are made for this and other essential developments relating to training and research. 相似文献
2.
Myrmecophily provides various examples of how social structures can be overcome to exploit vast and well-protected resources.
Ant nest beetles (Paussinae) are particularly well suited for ecological and evolutionary considerations in the context of
association with ants because life habits within the subfamily range from free-living and predatory in basal taxa to obligatory
myrmecophily in derived Paussini. Adult Paussini are accepted in the ant society, although parasitising the colony by preying
on ant brood. Host species mainly belong to the ant families Myrmicinae and Formicinae, but at least several paussine genera
are not host-specific. Morphological adaptations, such as special glands and associated tufts of hair (trichomes), characterise
Paussini as typical myrmecophiles and lead to two different strategical types of body shape: while certain Paussini rely on
the protective type with less exposed extremities, other genera access ant colonies using glandular secretions and trichomes
(symphile type). We compare these adaptations with other taxonomic groups of insects by joining contemporary research and
early sources and discuss the possibility of an attracting or appeasing effect of the secretion. Species that are ignored
by their host ants might use chemical mimicry instead. Furthermore, vibrational signals may contribute to ant–beetle communication,
and chemical signals have proven to play a role in host finding. The powerful defense chemistry of paussines as “bombardier
beetles” is not used in contact with host ants. We attempt to trace the evolution of myrmecophily in paussines by reviewing
important aspects of the association between paussine beetles and ants, i.e. morphological and potential chemical adaptations,
life cycle, host specificity, alimentation, parasitism and sound production.
相似文献
Stefanie F. GeiselhardtEmail: |
3.
Learning and natal host influence host preference,handling time and sex allocation behaviour in a pupal parasitoid 总被引:6,自引:0,他引:6
The host choice and sex allocation decisions of a foraging female parasitoid will have an enormous influence on the life-history
characteristics of her offspring. The pteromalid Pachycrepoideus vindemiae is a generalist idiobiont pupal parasitoid of many species of cyclorrhaphous Diptera. Wasps reared in Musca domestica were larger, had higher attack rates and greater male mating success than those reared in Drosophila melanogaster. In no-choice situations, na?ve female P. vindemiae took significantly less time to accept hosts conspecific with their natal host. Parasitoids that emerged from M. domestica pupae spent similar amounts of time ovipositing in both D. melanogaster and M. domestica. Those parasitoids that had emerged from D. melanogaster spent significantly longer attacking M. domestica pupae. The host choice behaviour of female P. vindemiae was influenced by an interaction between natal host and experience. Female P. vindemiae reared in M. domestica only showed a preference among hosts when allowed to gain experience attacking M. domestica, preferentially attacking that species. Similarly, female parasitoids reared on D. melanogaster only showed a preference among hosts when allowed to gain experience attacking D. melanogaster, again preferentially attacking that species. Wasp natal host also influenced sex allocation behaviour. While wasps from
both hosts oviposited more females in the larger host, M. domestica, wasps that emerged from M. domestica had significantly more male-biased offspring sex ratios. These results indicate the importance of learning and natal host
size in determining P. vindemiae attack rates, mating success, host preference and sex allocation behaviour, all critical components of parasitoid fitness.
Electronic Publication 相似文献
4.
Both phytophagous and parasitic insects deposit oviposition-marking pheromones (OMPs) following oviposition that function
to inform conspecifics of a previously utilized host of reduced suitability. The blueberry maggot fly, Rhagoletis mendax Curran (Diptera: Tephritidae), deposits eggs individually into blueberries and then marks the fruit surface with an OMP which
reduces acceptance of fruit for oviposition by conspecifics. Diachasma alloeum (Muesebeck) (Hymenoptera: Braconidae) is a parasitic wasp attacking larval R. mendax which also deposits an OMP, signaling conspecifics of a wasp-occupied host. Behavioral studies were conducted testing the
hypothesis that the OMP of the parasitic wasp modifies the oviposition behavior of its host fly. In this study, we show that
the OMP of D. alloeum is recognized by R. mendax, and female flies will reject wasp-marked fruit for oviposition. Thus, we present a rare demonstration of pheromonal recognition
between animals occupying different taxonomic orders and trophic levels. This chemical eavesdropping may enhance the ability
of the fly to avoid fruit unsuitable for larval development. 相似文献
5.
The host size model, an adaptive model for maternal manipulation of offspring sex ratio, was examined for the parasitoid
wasp Spalangia endius. In a Florida strain, as the model predicts, daughters emerged from larger hosts than sons, but only when mothers received
both small and large hosts simultaneously. The pattern appeared to result from the mother's ovipositional choice and not from
differential mortality of the sexes during development. If sex ratio manipulation is adaptive in the Florida strain, it appears
to be through a benefit to daughters of developing on large hosts rather than through a benefit to sons of developing on small
hosts. Both female and male parasitoids were larger when they developed on larger hosts. For females, developing on a larger
host (1) increased offspring production, except for the largest hosts, (2) increased longevity, (3) lengthened development,
and (4) had no effect on wing loading. For males, development on a larger host had no effect on any measure of male fitness
– mating success, longevity, development duration, or wing loading. In contrast, a strain from India showed no difference
in the size of hosts from which daughters versus sons emerged, although both female and male parasitoids were larger when
they developed on larger hosts. These results together with previous studies of Spalangia reveal no consistent connection between host-size-dependent sex ratio and host-size-dependent parasitoid size among strains
of S. endius or among species of Spalangia.
Received: 28 October 1998 / Received in revised form: 20 May 1999 / Accepted: 30 May 1999 相似文献
6.
The plant surface is the substrate upon which herbivorous insects and natural enemies meet and thus represents the stage for
interactions between the three trophic levels. Plant surfaces are covered by an epicuticular wax layer which is highly variable
depending on species, cultivar or plant part. Differences in wax chemistry may modulate ecological interactions. We explored
whether caterpillars of Spodoptera frugiperda, when walking over a plant surface, leave a chemical trail (kairomones) that can be detected by the parasitoid Cotesia marginiventris. Chemistry and micromorphology of cuticular waxes of two barley eceriferum wax mutants (cer-za.126, cer-yp.949) and wild-type cv. Bonus (wt) were assessed. The plants were then used to investigate potential surface effects on
the detectability of caterpillar kairomones. Here we provide evidence that C. marginiventris responds to chemical footprints of its host. Parasitoids were able to detect the kairomone on wild-type plants and on both
cer mutants but the response to cer-yp.949 (reduced wax, high aldehyde fraction) was less pronounced. Experiments with caterpillar-treated wt and mutant leaves
offered simultaneously, confirmed this observation: no difference in wasp response was found when wt was tested against cer-za.126 (reduced wax, wt-like chemical composition) but wt was significantly more attractive than cer-yp.949. This demonstrates for the first time that the wax layer can modulate the detectability of host kairomones. 相似文献
7.
Nina H. Fefferman James F. A. Traniello Rebeca B. Rosengaus Daniel V. CalleriII 《Behavioral ecology and sociobiology》2007,61(4):565-577
Understanding the origin of disease resistance in social insects is difficult due to the lack of well-established phylogenies
of presocial and eusocial species and the absence of extant basal and intermediate forms. Moreover, comprehensive accounts
of infection-control traits in social insect lineages are not available. Therefore, to explore the evolution of pathogen control
in social insects we used cellular automata models to analyze the efficacy of immunity and nest hygiene, which we assumed
were basal traits, and allogrooming, which likely followed the transition to eusociality, and their interactions with colony
demography and patterns of worker spatial distribution. Models showed that nest hygiene provided an immediate survival benefit
and that immunity lowered overall disease susceptibility under both constant and periodic exposure scenarios. Allogrooming
increased survivorship in chronically challenged colonies but also increased pathogen transmission rates under conditions
of periodic exposure. Colonies having demographies biased towards young or old individuals had slightly higher mortality than
those with heterogeneous demographies. The distribution of older individuals relative to the nest center had no significant
effect on susceptibility and provided only a minor survival advantage. Models indicated that nest hygiene and immunity function
on different temporal scales and can interact with demography to lower disease risks. Our results suggest how infection control
systems in social insects could have been built upon the inducible immune defenses and nest hygienic behaviors of solitary
and presocial ancestors and served as important preadaptations to manage disease exposure and transmission in colonies of
eusocial species. 相似文献
8.
In birds, host experience can modify response to parasites but nothing similar is known for insects. We studied two desert tenebrionid beetles, the subsocial host Parastizopus armaticeps and its obligate and ubiquitous brood-(clepto)parasite Eremostibes opacus, which mimics the hosts odour spectrum. Nearly 10% of host burrows in the field (n=214) remain unparasitised even after introducing E. opacus experimentally (n=22). In discrimination tests, 7% of naive host beetles eject the parasite, showing individual variation in olfactory discrimination ability. To test for effects of prior breeding experience, naive (first time) or experienced (second time) breeders with or without prior parasite contact were confined with E. opacus at breeding onset, their behaviour recorded and parasite number counted on breeding completion. More first- than second-time breeding pairs completely excluded the parasite and second-time breeders with no prior contact with E. opacus had fewer parasites than any others. These pairs increased burrow-guarding dramatically, mostly during early reproduction, this being the best predictor of parasite number. Prolonged guarding, however, must be traded-off against other brood-care behaviours. Hence, it might pay breeding pairs to take the risk of accepting some parasites breeding within their burrow, and we expect this effect will be more pronounced if poor feeding and digging conditions are taken into account. This might explain why apparently 90% of the P. armaticeps breeding burrows in the field contain at least one parasitic E. opacus.Communicated by D. Gwynne 相似文献
9.
In insect parasitoids, offspring fitness is strongly influenced by the adult females choice of host, particularly in ectoparasitoids that attack non-growing host stages. We quantified the fitness consequences of size-dependent host species selection in Dirhinus giffardii, a solitary ectoparasitoid of tephritid fruit fly pupae. We first showed a positive correlation between the size of emerged D. giffardii wasps and the size of their host fruit fly species (in order of decreasing size): Bactrocera latifrons, B. cucurbitae, B. dorsalis or Ceratitis capitata. We then manipulated individual wasps to show that the parasitoid preferred to attack the largest (B. latifrons) to the smallest (C. capitata) host species when provided with a choice, and laid a greater proportion of female eggs in B. latifrons than in C. capitata. There were no differences in developmental time or offspring survival between individuals reared from these two host species. Finally, we compared the foraging efficiency of large versus small wasps (reared from B. latifrons vs C. capitata) under two different laboratory conditions: high versus low host habitat quality, given that realized fecundity in parasitoids may be influenced by either egg-limited or time-limited factors. Under both conditions, large wasps parasitized more hosts than did small ones as a consequence of high searching efficiency in the host-poor habitat, and high capacity for adjusting egg maturation in response to host availability in the host-rich habitat. Considering the flexibility of body growth, the apparent lack of cost of achieving large body size in either development or survival, and the strong dependence of realized reproductive success on a females size, we argue that body size may be a key to understanding evolution of host species selection in ectoparasitoids. We also discuss constraints upon the evolution of size-dependent host species selection in parasitoids.Communicated by D. Gwynne 相似文献
10.
Summary. Host selection in tree-killing bark beetles
(Coleoptera: Scolytidae) is mediated by a complex of semiochemical
cues. Using gas chromatographic-electroantennographic
detection (GC-EAD) and GC-mass spectrometric
analyses, we conducted a comparative study of the electrophysiological
responses of four species of tree-killing bark
beetles, the Douglas-fir beetle, Dendroctonus pseudotsugae,
Hopkins, the mountain pine beetle, D. ponderosae Hopkins,
the spruce beetle, D. rufipennis Kirby, and the western balsam
bark beetle, Dryocoetes confusus Swaine, to volatiles
captured by aeration of 1) bole and foliage of four sympatric
species of conifers, Douglas-fir, Pseudotsuga menziesii
(Mirb.) Franco, lodgepole pine, Pinus contorta var. latifolia
Engelm., interior spruce, Picea engelmannii x glauca, and
interior fir, Abies lasiocarpa x bifolia, and 2) con- and
heterospecific beetles at three stages of attack. We identified
13 monoterpenes in the conifers and nine compounds in the
volatiles of beetles that elicited antennal responses. There
was no qualitative difference in the terpene constitution of
the four species of conifers and very little difference across
beetle species in their antennal response to compounds from
conifers or beetles. The lack of species-specific major or
minor components in conifers suggests that beetles would
need to detect differences in the ratios of different compounds
in conifers to discriminate among them. Attraction to
hosts and avoidance of nonhost conifers may be accentuated
by perception of compounds emitted by con- and heterospecific
beetles, respectively. The 22 compounds identified
are candidate semiochemicals with potential behavioural
roles in host location and discrimination. 相似文献