Factors influencing infection patterns of trophically transmitted parasites among a fish community: host diet, host-parasite compatibility or both?

Parasite infection patterns were compared with the occurrence of their intermediate hosts in the diet of nine sympatric fish species in a New Zealand lake. Stomach contents and infection levels of three gastrointestinal helminth species were examined from the entire fish community. The results highlighted some links between fish host diet and the flow of trophically transmitted helminths. Stomach contents indicated that all but one fish species were exposed to these helminths through their diet. Host feeding behaviour best explained infection patterns of the trematode Coitocaecum parvum among the fish community. Infection levels of the nematode Hedruris spinigera and the acanthocephalan Acanthocephalus galaxii, however, were not correlated with host diets. Host specificity is thus likely to modulate parasite infection patterns. The data indicate that host diet and host-parasite compatibility both contribute to the distribution of helminths in the fish community. Furthermore, the relative influence of encounter (trophic interactions between prey and predator hosts) and compatibility (host suitability) filters on infection levels appeared to vary between host-parasite species associations. Therefore, understanding parasite infection patterns and their potential impacts on fish communities requires determining the relative roles of encounter and compatibility filters within and across all potential host-parasite associations.

Parasite spillback: a neglected concept in invasion ecology?

While there is good evidence linking animal introductions to impacts on native communities via disease emergence, our understanding of how such impacts occur is incomplete. Invasion ecologists have focused on the disease risks to native communities through "spillover" of infectious agents introduced with nonindigenous hosts, while overlooking a potentially more common mechanism of impact, that of "parasite spillback." We hypothesize that parasite spillback could occur when a nonindigenous species is a competent host for a native parasite, with the presence of the additional host increasing disease impacts in native species. Despite its lack of formalization in all recent reviews of the role of parasites in species introductions, aspects of the invasion process actually favor parasite spillback over spillover. We specifically review the animal-parasite literature and show that native species (arthropods, parasitoids, protozoa, and helminths) account for 67% of the parasite fauna of nonindigenous animals from a range of taxonomic groups. We show that nonindigenous species can be highly competent hosts for such parasites and provide evidence that infection by native parasites does spillback from nonindigenous species to native host species, with effects at both the host individual and population scale. We conclude by calling for greater recognition of parasite spillback as a potential threat to native species, discuss possible reasons for its neglect by invasion ecologists, and identify future research directions.

Distribution of putative male sex pheromones among Lutzomyia sandflies (Diptera: Psychodidae).

Male Lutzomyia longipalpis produce terpene sex pheromones in glandular tissue underlying the cuticle. The pheromones are transmitted to the surface via cuticle-lined ducts (measuring 0.25 microm in diameter), each of which reaches the surface in the centre of a papule (measuring 3-3.5 microm in diameter). Similar papules, in a range of shapes but all characterized by the presence of a central pore and absence of macroserae, occur in some other species of sandfly. The aim of the present study was to determine the distribution of sex pheromones in sandflies of the genus Lutzomyia that do and do not have the papules. The results indicate that sex pheromones are not widely distributed amongst male Lutzomyia spp. Male members of the genus can be subdivided into three groups: those that produce terpenes and have cuticular papules; those that do not produce terpenes but still have the associated papules; and those that have neither terpenes nor papules. The papules seen in the species that do not synthesise sex pheromones are presumably vestigial, non-functional structures. Such species may have stopped producing pheromone as the result of changes in the way in which the females found and selected mates or changing feeding preferences. A similar event has occurred in the Lepidoptera, where vestigial pheromone-secreting structures remain in some species which no longer produce pheromone. Lutzomyia lenti collected in southern Brazil produced a novel diterpene whereas male L. lenti from north-eastern Brazil did not, supporting suggestions by others that L. lenti is, like L. longipalpis, a species complex.

Why are some people bitten more than others?

Much progress has been made in describing how it is, in a mechanistic sense, that some vertebrate hosts (species or individuals) are bitten more than others, principally because of their odour or appearance. Little attention has been paid to why, in an evolutionary sense, these particular animals are bitten. Irrespective of the proximate mechanisms of host choice, there must be an intense selection pressure on insects to feed on those hosts that are most amenable to being bitten. We should be better able to predict host choice by understanding the evolutionary processes at work.

Coccidiosis in the European badger (Meles meles) from England, an epidemiological study.

In total 445 faecal samples were collected from 259 European badgers (Meles meles) in Wytham Woods, Oxfordshire, UK (462080). Microscopical examination revealed infection with 2 species of coccidia Eimeria melis and Isospora melis. From the initial examination of each animal, point prevalence rates of 0.44 and 0.35 were calculated for Eimeria and Isospora respectively. The intensity of infection was significantly greater for Eimeria than Isopora and the distribution of intensities was highly skewed for both species, with a few individuals shedding the majority of oocysts. Incidence and recovery rates for both coccidia species were calculated from longitudinal data collected at 3-monthly intervals from a subset of the adult badger population, and the predicted prevalence rates based on these were similar to the point prevalence rates. This suggests little, if any, parasite-induced mortality in the adult population. In contrast, there was a marked and significant reduction in the point prevalence and intensity of infection with Eimeria from cub to adult badger suggesting a degree of acquired immunity to Eimeria melis on initial exposure and/or that there is significant Eimeria-associated mortality in the cub population. No such relationship was found for Isospora infection. In those adult badgers with co-infections there was a direct relationship between the intensity of Eimeria and Isospora. The taxonomic status of these parasites suggests a heteroxenous life-cycle for I. melis, and direct transmission of E. melis. However, the greater than expected prevalence of co-infection is consistent with a common source of infection, such as communal latrines.

Epidemiology and optimal foraging: modelling the ideal free distribution of insect vectors.

Existing models of the basic case reproduction number (R0) for vector-borne diseases assume (i) that the distribution of vectors over the susceptible host species is homogeneous and (ii) that the biting preference for the susceptible host species rather than other potential hosts is a constant. Empirical evidence contradicts both assumptions, with important consequences for disease transmission. In this paper we develop an Ideal Free Distribution (IFD) model of host choice by blood-sucking insects, predicated on the argument that vectors must have evolved to choose the least defensive hosts in order to maximize their feeding success. From a re-analysis of existing data, we demonstrate that the interference constant, m, of the IFD can vary between host species. As a result, the predicted distribution of insects over hosts has 2 desirable and intuitively plausible behaviours: that it is heterogeneous both within and between host species; and that the intensity of heterogeneity varies with host and vector density. When the IFD model is incorporated into R0, the relationship with the vector:host ratio becomes non-linear. If correct, the IFD could add considerable realism to models which seek to predict the effect of these ecological parameters on disease transmission as they vary naturally (e.g. through seasonality in vector density or host population movement) or as a consequence of artificial manipulation (e.g. zooprophylaxis, vector control). It raises the possibility of targeting transmission hot spots with greater accuracy and concomitant reduction in control effort. The robustness of the model to simplifying assumptions is discussed.

Differential application of lambda-cyhalothrin to control the sandfly Lutzomyia longipalpis.

To study the impact of residual pyrethroid insecticide on the abundance and distribution of peridomestic Lutzomyia longipalpis, the sandfly vector of visceral leishmaniasis in Brazil, lambda-cyhalothrin was applied at 20 mg a.i.m-2 in the following interventions: (i) spraying of all animal pens in a village (blanket coverage); (ii) treatment of a subset of animal pens, either by spraying, or by installation of insecticide-impregnated 1 m2 cotton sheets as 'targets' (focal coverage). By sampling with CDC light traps, and using a novel analytical approach, we detected a 90% reduction in Lu.longipalpis abundance in sprayed sheds of the focal intervention. However, there was no discernible effect on the abundance of other phlebotomines trapped in sheds, or on the abundance of Lu.longipalpis in untreated dining-huts and houses. This differential impact on Lu.longipalpis abundance is explained in terms of the disruption of male pheromone production. Treated targets were approximately half as effective as residual spraying in reducing the abundance of Lu.longipalpis in sheds. Following blanket intervention, the abundance of Lu.longipalpis in traps fell by only 45% (not significant): catches at untreated dining-huts actually increased, possibly because the blanket coverage diverted Lu.longipalpis away from major aggregation sites at animal pens. It is recommended that care be taken during vector control programmes to ensure that all potential aggregation sites are treated. The possible consequences of leaving some sites untreated include poor control of peridomestic sandfly abundance and an increase in the biting rate on dogs and humans.

A model of spine, ribcage and pelvic responses to a specific lumbar manipulative force in relaxed subjects.

One class of manipulative techniques commonly used during assessment and treatment of spinal disorders involves the patient lying face down while the therapist slowly applies a posteroanterior force to a selected vertebra. The aim of this investigation was to develop a model which was capable of predicting the vertebral displacements resulting from such a manipulative force, applied to the lumbar spine. A linear three-dimensional finite element model was generated using both previously published and original data to define the geometry and material properties. The complete model included the ribcage, thoraco-lumbar spine and pelvis with their associated soft tissues. The model simulated the relaxed state in a normal subject so the muscle forces were assumed to be negligible. Sensitivity analysis suggested that if the model was to be used to simulate the behaviour of individual subjects, then the model dimensions and pelvic constraints should be matched to the particular subject. The model validity was studied by comparing the predicted responses with those that have been observed in living human subjects. The model predictions were found to be in good agreement with the mean observed human responses, with predicted displacements being within one standard deviation of the mean observed values. This agreement suggests that the model is useful for predicting the linear region responses to slowly applied lumbar posteroanterior forces. The simulations predicted that appreciable global vertebral displacements (up to 1.5 mm) and rotations (up to 1 degree) occurred as far away as the middle and lower thoracic spine during low lumbar loading. Intervertebral translations were predicted to be 1 mm or more at up to four intervertebral joints away from the point of load application.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of methapyrilene by Fischer-344 rat and B6C3F1 mouse hepatocytes.

1. Suspension cultures of freshly isolated F344 rat and B6C3F1 mouse hepatocytes were compared for their ability to transform various concentrations of methapyrilene (MP). 2. MP metabolites were isolated and purified by h.p.l.c., and were identified by comparing their chromatographic and mass spectral properties with those of authentic standards. 3. Both rat and mouse hepatocytes transformed MP to tentatively identified 2-thiophenecarboxylic acid (I), and definitively identified mono-N-desmethyl methapyrilene glucuronide (II), methapyrilene glucuronide (III), methapyrilene N-oxide (V), and mono-N-desmethyl methapyrilene (VII).

Regulation of prostaglandin E2 production by vitamin D metabolites in growth zone and resting zone chondrocyte cultures is dependent on cell maturation.

The production of PGE2 by chondrocytes and its regulation by vitamin D metabolites was examined in this study as a function of cell maturation. Costochondral chondrocytes, derived from the resting zone and growth zone cartilage, were grown in culture to fourth passage. At confluence, they were exposed to 10(-8)-10(-11)M 1,25-(OH)2D3 or to 10(-7)-10(-10)M 24,25-(OH)2D3 for either five minutes or 3, 6, 12, or 24 hours. Indomethacin (10(-7)M) was added to one-half of the cultures to block the production of PGE2. The amount of PGE2 released into the media was determined by radioimmunoassay. Both growth zone and resting zone cells produced PGE2 in a time-dependent manner; PGE2 concentration was greater in the resting zone cell cultures. 1,25-(OH)2D3 stimulated PGE2 production by growth zone cells in a dose-dependent manner, significant at 10(-8)-10(-10)M. This effect was observed at 3 hours and remained elevated during the 24 hours of culture. 1,25-(OH)2D3 had no effect on PGE2 production by resting zone cells. However, 24,25-(OH)2D3 (10(-7)-10(-8)M) inhibited PGE2 production from 3-24 hours. No effect was noted when 24,25-(OH)2D3 was added to growth zone cells. Indomethacin reduced PGE2 production to baseline values in all groups examined. The results indicate that chondrocytes in culture produce PGE2. Production is regulated by vitamin D3 metabolites and is cell maturation-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma elimination and urinary excretion of methapyrilene in the rat.

The metabolism and elimination of methapyrilene (2-[(2-dimethylaminoethyl)-2-thenylamino]pyridine) were characterized after the iv administration of 0.7 mg/kg or 3.5 mg/kg methapyrilene HCl plus [14C]methapyrilene HCl to adult male Fischer-344 rats. Approximately 40% and 35% of the administered dose was excreted in the urine in the first 24 hr in the low and high dose groups, respectively, as determined by liquid scintillation spectrophotometry. Fecal excretion accounted for 38% and 44% of the administered dose in the first 24 hr in the low and high dose groups, respectively, as confirmed via combustion analysis. The 24-hr urinary metabolic products consisted of one major and five minor radiolabeled compounds. The major metabolite was isolated with reversed-phase HPLC and identified as methapyrilene N-oxide. This was accomplished by comparison of the chromatographic and mass spectral characteristics of this metabolite with that of authentic methapyrilene N-oxide. Methapyrilene and mono-N-desmethyl methapyrilene also were identified after isolation with reversed-phase HPLC and comparison of their mass spectral and/or chromatographic properties with those of authentic compounds. The plasma metabolic profile was essentially the same as the urinary profile. The elimination of methapyrilene from plasma occurred through a first-order process. The terminal plasma elimination t1/2 of methapyrilene did not increase with increasing doses (2.75 hr, 0.7 mg/kg; 2.81 hr, 3.5 mg/kg); thus, methapyrilene does not exhibit dose-dependent elimination over this 5-fold dose range.

Fast-atom bombardment and thermospray mass spectrometry for the characterization of two glucuronide metabolites of methapyrilene.

Two conjugated metabolites of methapyrilene hydrochloride isolated from mouse-hepatocytes were examined by mass spectrometry using fast-atom bombardment (FAB) and thermospray ionization. The major metabolite, methapyrilene glucuronide, was identified based on a prominent peak due to the protonated molecule as well as the loss of the dimethylamine and sugar moieties. Identification of the second metabolite was complicated by large signals associated with the biological sample matrix. The complementary nature of the fragmentation observed in the mass spectra using FAB and thermospray ionization allowed this metabolite to be identified as the desmethylmethapyrilene glucuronide. The fragmentation observed using FAB ionization was not greatly affected by the presence of the glucuronide moiety. While loss of the sugar moiety indicated a glucuronide, additional fragmentation confirmed the presence of the underlying ethylenediamine substructure which is characteristic of this class of antihistamines.

The metabolism and elimination of pyrilamine maleate in the rat.

The metabolism and elimination of pyrilamine (2-[(2-dimethylamino-ethyl)(p-methoxybenzyl)amino]pyridine) were characterized after the iv administration of 7.0 mg/kg or 0.7 mg/kg pyrilamine maleate plus [14C]pyrilamine maleate to adult male Fischer-344 rats. Approximately 29% and 38% of the administered dose was excreted in the urine in the first 24 hr in the high and low dose groups, respectively, as determined by liquid scintillation spectrometry. Fecal excretion accounted for 27% and 30% of the administered dose in the first 24 hr in the high and low dose groups, respectively, as confirmed via combustion analysis. The 24-hr urinary metabolic products consisted of one major and four minor radiolabeled compounds. The major metabolite was isolated by reversed-phase high performance liquid chromatography and identified as the O-glucuronic acid conjugate of O-demethyl pyrilamine. This was accomplished by comparison of the chromatographic characteristics of this metabolite's aglycon with that of an authentic standard of O-demethyl pyrilamine and fast atom bombardment mass spectrometry of the unhydrolyzed conjugate. Pyrilamine and its N-oxide and O-demethyl derivatives were also identified after isolation by reversed-phase high performance liquid chromatography and comparison of their mass spectral and/or chromatographic properties with those of authentic compounds. The plasma metabolic profile was essentially the same as the urinary profile except for the absence of O-demethyl pyrilamine. The plasma elimination of pyrilamine fit a one-compartment open model and was first order. The terminal plasma elimination half-life of pyrilamine did not increase with increasing doses (2.3 hr, 0.7 mg/kg; 1.5 hr, 7.0 mg/kg) and thus pyrilamine does not exhibit dose-dependent elimination.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbial metabolism of pyrene.

The isolation and identification of pyrene metabolites formed from pyrene by the fungus Cunninghamella elegans is described. C. elegans was incubated with pyrene for 24 h. Six metabolites were isolated by reversed-phase high-performance liquid (HPLC) and thin-layer chromatography (TLC) and characterized by the application of UV absorption, 1H-NMR and mass spectral techniques. C. elegans hydroxylated pyrene predominantly at the 1,6- and 1,8-positions with subsequent glucosylation to form glucoside conjugates of 1-hydroxypyrene, 1,6- and 1,8-dihydroxypyrene. In addition, 1,6- and 1,8-pyrenequinones and 1-hydroxypyrene were identified as metabolites. Experiments with [4-14C]pyrene indicated that over a 24-h period, 41% of pyrene was metabolized to ethyl acetate-soluble metabolites. The glucoside conjugates of 1-hydroxypyrene, 1,6- and 1,8-dihydroxypyrene accounted for 26%, 7% and 14% of the pyrene metabolized, respectively. Pyrenequinones accounted for 22%. The results indicate that the fungus C. elegans metabolized pyrene to non-toxic metabolites (glucoside conjugates) as well as to compounds (pyrenequinones) which have been suggested to be biologically active in higher organisms. In addition, there was no metabolism at the K-region of the molecule which is a major site of enzymatic attack in mammalian systems.

Patellar and quadriceps tendon ruptures--jumper's knee.

We reviewed 13 patients with end stage jumper's knee, 10 with patellar tendon ruptures, and 3 with ruptures of the quadriceps tendon to evaluate our long-term results in treating these tendon ruptures in an athletic population. The focus was on the natural history, the time until return, and the level of return, to athletic activity. Jumper's knee affected all patients to a varying degree prior to rupture. Basketball was the most common sport involved. At followup, averaging 4 1/2 years, patients underwent functional and clinical, as well as Cybex and roentgenographic, evaluations. Results indicated patellar tendon ruptures, where the ruptures are complete, have a more favorable prognosis than those of the quadriceps tendon which are incomplete. All of the latter patients continued to have quadriceps tendinitis following repair. In both groups, the poor results were obtained in patients with chondromalacia and/or patella alta. Cybex testing yielded results of greater than 100% strength in three patients with patellar tendon ruptures, but no patient with quadriceps rupture had comparable test results. There was no apparent relationship between ruptures and cortisone injections. Patellar and quadriceps tendon ruptures from indirect injury in athletes represent the end stage of jumper's knee and result from repetitive microtrauma. Excellent function usually follows repair of patellar tendon ruptures when surgery is performed early and care is taken to restore normal patellar tendon length. Results of quadriceps ruptures are less satisfactory since these ruptures are usually incomplete and all degenerative tissue may not be involved in the healing response.

Congenital dislocation of the radial head: spectrum and natural history.

A retrospective review of 24 patients with congenital radial head dislocation and three patients with congenital elbow dysplasias was performed. Eight patients had only congenital radial head dislocations and no other anomalies. In these eight patients, a noted limitation of elbow and forearm motion was greatest in those with anterior dislocations. Limitation of wrist motion also was noted in all affected extremities. Unilateral congenital radial head dislocation as well as progressive subluxation to dislocation were documented. There was no increased loss of motion as growth occurred. Significant pain was noted only in adults. Radial head excision after age 15 relieved pain and improved cosmesis but failed to significantly affect motion. Excision performed prior to this age showed regrowth of the proximal radius. A finding of increased ulnar length in relation to the radius in wrist roentgenograms of affected extremities was a significant diagnostic sign.

Quadriceps rupture in association with the roentgenographic "tooth" sign: a case report.

This article reports a case of quadriceps tendon rupture in association with the roentgenographic "tooth" sign. This sign has not been reported previously in association with quadriceps tendon rupture, but may be helpful in assisting in the early diagnosis of this injury.