Competition,facilitation or mediation via host? Patterns of infestation of small European mammals by two taxa of haematophagous arthropods

1. We studied the effect of flea infestation on the pattern of tick (Ixodes ricinus and Ixodes trianguliceps) infestation on small mammals. 2. We asked (1) whether the probability of an individual host being infested by ticks was affected by its infestation of fleas (number of individuals and species) and (2) whether the abundance and prevalence of ticks in a host population was affected by the abundance, prevalence, level of aggregation, and species richness of fleas. 3. The probability of a host individual being infested by ticks was affected negatively by flea infestation. At the level of host populations, flea abundance and prevalence had a predominantly positive effect on tick infestation, whereas flea species richness had a negative effect on tick infestation. 4. The effect of flea infestation on tick infestation was generally greater in I. ricinus than in I. trianguliceps, but varied among host species. 5. It can be concluded that the effect of fleas on tick infestation of small mammals may be either negative or positive depending on the level of consideration and parameters involved. The results did not provide support for direct interactions between the two ectoparasite taxa, but suggested population and community dynamics and the defence system of the hosts as possible factors.     

稻纵卷叶螟和白背飞虱序列危害及间隔天数对水稻生理生化的影响

【目的】为了解稻纵卷叶螟Cnaphalocrocis medinalis和白背飞虱Sogatella furcifera的复合危害对水稻产量相关因子和相关酶类的影响。【方法】本文设定两种害虫的先后危害顺序,并通过调整两者开始危害的时间,研究了受害后水稻在灌浆期根、茎和叶片中淀粉和蔗糖含量的变化以及蔗糖合成酶(Sucrose synthase,SS)和蔗糖磷酸合成酶(Sucrose phosphate synthase,SPS)活性的变化。【结果】随着接虫量的增加,水稻不同组织内各生理指标与对照相比均显著下降。随着间隔天数的增加,先接白背飞虱为害要重于先接稻纵卷叶螟。比如叶片中蔗糖含量在先接稻纵卷叶螟的处理中随着间隔天数的增加显著增加,相应的SPS活性显著增加,间隔24 d的处理显著高于间隔6 d和12 d;而先接白背飞虱的处理中蔗糖含量与SPS活性均显著降低,间隔24 d的处理显著低于间隔6 d和12 d的处理。茎部淀粉含量在先接稻纵卷叶螟的处理中随着间隔天数的增加逐渐增加,SS活性显著增加,而先接白背飞虱的处理中淀粉含量和SS活性均显著降低;叶片中淀粉含量均随着间隔天数的增加逐渐降低,而相应的SS活性在先接稻纵卷叶螟的处理中显著增加,在先接白背飞虱的处理中相反。另外,接虫量和间隔天数间有显著的交互作用。【结论】本研究对指导水稻生产中的"两迁害虫"防治具有潜在应用价值。     

Nutrient uptake of rice roots in response to infestation of Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

This study investigated the uptake of three macronutrients, including nitrogen (N), phosphorus (P), and potassium (K), by rice roots in response to different infestation levels of Nilaparvata lugens (St?l) (Homoptera: Delphacidae). Hydroponics experiments were conducted on the rice variety 'Zhendao 2' (moderately resistant to Tryporyza incertulas, Lepidoptera: Pyralidae) and the variety 'Xiushui 63' (susceptible to N. lugens). In 'Zhendao 2', N. lugens infestation significantly influenced the uptake of P and K but not N, with P and K uptake decreasing as the duration of N. lugens infestation increased. In 'Xiushui 63', N. lugens infestation influenced N, P, and K uptake to a different degree, depending on the infestation level, in which infestation for 2, 4, 6, and 8 d at a density of 60 nymphs did not affect N uptake, but such infestation levels significantly influenced the uptake of P and K. After the removal of N. lugens from rice plants, the N uptake recovered from infestation faster than that for P and K in the variety 'Zhendao 2', whereas the recovery rate of K uptake was faster than that for N and P in the variety 'Xiushui 63'. The recovery rate of the nutrient uptake was negatively correlated to the density and duration of infestation. The experimental results demonstrated that N, P, and K uptake of rice roots were largely not influenced by N. lugens infestation when the pest density was controlled below 15 nymphs per hill. This infestation level was in agreement with the proposed economic thresholds for control measures against the N. lugens infestation on rice plants.     

Ectoparasites of rodents of the urban region of Belo Horizonte, MG. II. Variations of the infestation indices in Rattus norvegicus norvegicus

The indices of infestation by the mites Echinolaelaps echidninus and Laelaps nuttalli, the louse Popyplax spinulosa and the flea Xenopsylla cheopis, obtained monthly, from June 1980 to September 1982, on Rattus norvegicus norvegicus in the city of Belo Horizonte, Minas Gerais state, Brazil were related to seasonal period, sex of the host and area of capture. Mites and insects showed different behaviour in relation to these factors. Only the fleas and lice exhibit significant association between the rodents' infestation and the seasonal period, or between the infestation and the rodents' sex or else a variation of the distribution by the three main areas of capture. The fleas showed the highest indices of infestation in the warm-rainy season (October to March) while the infestation by the lice was more prevalent in the dry-cool season. The climatic factors most related with the hosts' infestation were, in decreasing order, rainfall, temperature and relative humidity. Fleas and lice preferentially infested male rodents, being infestation by X. cheopis highly significant.     

Infestation of cassava genotypes by Neosilba perezi (Romero & Ruppell) (Diptera: Lonchaeidae)

The objectives of this work were to assess the infestation of ten genotypes of cassava by the shoot fly Neosilba perezi (Romero & Ruppell) and to investigate effects of plant age, temperature or precipitation on cassava plants infestation by the shoot fly. Thirty-two individuals of each cassava genotype were planted and analyzed every two weeks in order to calculate the percentage of plants infested by shoot fly larvae at each sampling event and per genotype. Infestation by the fly was different across the genotypes. Genotype IAC Caapora 105-66 and genotype IAC Cascuda were resistant to shoot fly infestation, whereas the genotype IAC 15 was the most susceptible to this insect. Plant age may have an influence on infestation by shoot flies. Advanced plant age apparently favors lower or even inexistent infestation rates. However, infestation rate does not seem to be affected by temperature or precipitation.     

Changes in immunity to Ixodes ricinus by rabbits infested at different levels

Abstract. Two groups of rabbits were infested twice with different numbers of Ixodes ricinus adults: one group (high infestation) with twenty-five females and twenty-five males and the other group (low infestation) with five pairs. A third infestation was performed in both groups with fifteen adult pairs. Tick biology was monitored for resistance effects. At the second infestation, the feeding and the egg production were more perturbed in ticks fed on high infestation rabbits. The embryogenesis was only affected in ticks from high infestation rabbits. At the third infestation, resistance was increased only in low infestation rabbits, which became more resistant than high infestation rabbits. The blastogenic response of peripheral blood lymphocytes and antibody production against ticks were assessed. A salivary gland extract and an integumental antigen from Lricinus adult females were able to initiate lymphocyte proliferation. The response was significantly higher in high infestation rabbits, especially at the end of the second infestation, and higher in low infestation rabbits during the third infestation. Non-specific proliferation with concanavalin A was temporarily decreased in both rabbits groups during the first and the second infestations. Specific antibody response to salivary and integument antigens were always the highest in high infestation rabbits. The involvement of tick-induced immunosuppression is discussed.     

Dot-ELISA assessment of guinea pig antibody responses to repeated Dermacentor andersoni infestations

Acquired resistance to ixodid tick infestation is expressed by cattle and laboratory animals. Humoral factors appear to be involved in host acquired resistance to tick bite; however, specific immune responses have yet to be fully characterized. This study examined tick resistance expressed by Hartley guinea pigs upon repeated infestation with Dermacentor andersoni, and describes longitudinal development of antigen specific immunoglobulin over approximately 180 days. Guinea pigs were infested either 4 times with D. andersoni adults, or twice with nymphs. Both infestation groups, adults and nymphs, demonstrated a significant level of resistance to re-infestation, following initial exposure. Dot enzyme-linked immunosorbent assay (Dot-ELISA) was employed to detect antibody reactive with D. andersoni salivary gland antigens (SGA). Animals infested with adults had antibody that increased at a relatively constant rate until the fourth infestation, which was differentiated by a sharp increase in titer, that was maintained for approximately 2 wk. Guinea pigs that received nymph infestations had SGA-specific antibody; however, titers were lower than those in the adult infestation group. Antibody levels continued to increase approximately 80 days beyond the final (second) infestation for this group. A direct correlation between resistance and antibody titer was not evident, since resistance was relatively stable after the second infestation in both infestation groups, and tick-specific immunoglobulin levels continually increased.     

The effect of Pythium oligandrum and chitosan used in control of potato against late blight and the occurrence of fungal diseases on tuber peel

The aim of two year investigation was the valuation the effect of biopreparate Polyversum (B.A.S. Pythium oligandrum) and preparate Biochikol 020 PC (B.A.S. chitosan) used in control of potato against Phytophthora blight on the tuber infestation during storage by Helminthosporium solani and tuber infestation by sclerotia of Rhizoctonia solani. As the standard fungicide Vitavax 200 FS (B.A.S. karboxin and thiuram) was used. After harvesting 100 tubers from each plots was collected and put in storage. The analysis of tuber infestation by Rhizoctonia solani and Helminthosporium solani was made after harvesting (September) and later every 3 months during storage period (December, March). The percent of diseased tubers in tested sample and also infestation degree of bulbs using 5-degree scale was estimated. The received results of investigations ascertained, that all tested preparations during potato vegetation influenced on lower (in comparison with control) degree of bulbs infestation by sclerots of Rhizoctonia solani and the mean degree of infestation by Helminthosporium solani. Moreover the percent of diseased tubers infected by pathogens with tested preparations combination was significant lower than in control.     

Aphids at crossroads: when branch architecture alters aphid infestation patterns in the apple tree

Plant architecture highly constrains pest infestation but is rarely considered in studies on plant–insect interactions. We analysed the relationships between apple tree architectural traits manipulated by tree training and within-branch development of Dysaphis plantaginea (rosy apple aphid, RAA), a major apple pest, during its multiplication wingless phase in spring. We hypothesised that the degree of branching had an effect on RAA within-branch infestation. In an experimental apple orchard, the infestation by aphid wingless forms was surveyed in two consecutive spring seasons within branches manipulated to design contrasted architectures differing in shoot numbers, shoot density and branching orders. Whatever the branch management system, aphid infestation was higher on long versus short, fruiting versus vegetative, and growing versus non-growing shoots. Either less infested shoots or less severe infestation were observed in the most branched system. A pattern of within-branch short-distance infestation was confirmed. Moreover, the number of branching points between two shoots exerted a high constraint on this infestation pattern. Beside possible trophic effects due to plant growth patterns already documented in the literature, a high degree of branching is likely to be a key-architectural trait to constrain within-branch aphid infestation. This opens new perspectives on the manipulation of branch architecture as a mean giving partial control of pests towards sustainable fruit production.     

The prevalence of head louse infestation among urban and rural children in Korea

The prevalence of head louse (Pediculus hamanus var. capitis) infestation in preschool and school children in 9 urban and 8 rural areas of Korea, was investigated. Of 11,865 children who were examined for head lice and nits, 2,900(24.4%) were found infested. The over-all infestation rate of rural children, 58.9%, was higher than that of urban children, 14.4%. There also existed significant differences in the infestation rate among various regions of urban as well as rural areas. Females were more infested than males. But there was no differences in infestation rate in either sex of preschool age. The infestation rate increased gradually from the age of 6, reached a plateau between 9-12 years of age and thereafter slowly decreased. The infestation rate of an orphanage children was higher than that of general childhood population. Health education and mass-delousing attempt are urgently required to lower such a high prevalence of head louse infestation in Korea.     

Distribution of infestation by lentil gall midge Contarinia lentis (Dipt., Cecidomyiidae) in lentil fields: statistical model

The horizontal distribution of infestation by Contarinia lentis in lentil fields, not subjected to chemical control was recorded and analysed in Slovak Republic during outbreaks of this pest in 1986–89. Infestation level was defined as the percentage of galls form the total number of galls, pods, and flowers. The highest level of infestation were found along the edges and the lowest levels in the centres of fields. The distribution of the infestation between the edge and the centre has been described for 18 fields using a nonlinear function containing two parameters. The first parameter represents the infestation level at the edge. The second parameter represents the rate of decreas of infestation from the edge towards the centre of the field. The relationship between the first parameter and the distance to the adult midge emerge site and the relationship between second parameter and the mean velocity of winds caryring females from the emergence site is described using exponential functions. The results indicate that (1) the longer the distance to the midge emergence site, the lower the infestation at the edge; and (2) the gretaer the wind velocity, the weaker the decrese in infestation from the edge towards the centre of a field.     

Negative Feedbacks on Bark Beetle Outbreaks: Widespread and Severe Spruce Beetle Infestation Restricts Subsequent Infestation

Understanding disturbance interactions and their ecological consequences remains a major challenge for research on the response of forests to a changing climate. When, where, and how one disturbance may alter the severity, extent, or occurrence probability of a subsequent disturbance is encapsulated by the concept of linked disturbances. Here, we evaluated 1) how climate and forest habitat variables, including disturbance history, interact to drive 2000s spruce beetle (Dendroctonus rufipennis) infestation of Engelmann spruce (Picea engelmannii) across the Southern Rocky Mountains; and 2) how previous spruce beetle infestation affects subsequent infestation across the Flat Tops Wilderness in northwestern Colorado, which experienced a severe landscape-scale spruce beetle infestation in the 1940s. We hypothesized that drought and warm temperatures would promote infestation, whereas small diameter and non-host trees, which may reflect past disturbance by spruce beetles, would inhibit infestation. Across the Southern Rocky Mountains, we found that climate and forest structure interacted to drive the 2000s infestation. Within the Flat Tops study area we found that stands infested in the 1940s were composed of higher proportions of small diameter and non-host trees ca. 60 years later. In this area, the 2000s infestation was constrained by a paucity of large diameter host trees (> 23 cm at diameter breast height), not climate. This suggests that there has not been sufficient time for trees to grow large enough to become susceptible to infestation. Concordantly, we found no overlap between areas affected by the 1940s infestation and the current infestation. These results show a severe spruce beetle infestation, which results in the depletion of susceptible hosts, can create a landscape template reducing the potential for future infestations.     

Mass treatment of head louse infestation with Sumithrin powder in primary schools in Korea.

A mass treatment of head louse infestation with Sumithrin powder (0.4% phenothrin) in primary school children was implemented during the period of September 1991-May 1992. The infestation rate of total 2,515 children was 38.6% in average (21.2% in boys and 57.2% in girls). The reduction rate of head louse infestation was 93.4% with a single treatment and 94.8% with double consecutive treatments with about 10 days interval, which indicated that a single treatment would be recommended for the mass treatment in the community. Long term follow-up after Sumithrin powder application for head louse control in a primary school showed that the infestation rate dropped from 33.1% before treatment to 5.4% by seven months after treatment, giving a 83.4% reduction rate.     

Prevalence of head lice (Pediculus humanus capitis) infestation among schools workers in the Eastern Region,Saudi Arabia

In a cross-sectional survey in February-May 2019, the prevalence of Pediculosis capitis with demographic data and the behavioral practices were investigated among 750 participants in the Eastern region of Saudi Arabia. Female participation was highly remarked with a percentage of 94.08% compared to that of male one about 5.91%. A deficiency of knowledge about lice infestation was noted especially among illiterate participants raised from their socio-economic levels (p-value = 0.001). Lice infestation reached higher rates in children aged less than 20 years with itching of the hair scalp. The obtained results revealed that 59.33% of the respondents believed that frequency of personal hygiene and washing of hair were the best methods for preventing the lice infestation. However, the treatment of lice infestation using anti-lice agents (p-value = 0.020) was preferred by 14.26% of participants. Although knowledge about the preventive tools for lice infestation (p-value 0.089) was not significantly associated with the experience of infestation but knowledge about the appropriate treatment to kill lice (p-value 0.020) and the wrong practices in the treatment of a head lice infestation were (p-value 0.005) significantly associated with the experience of infestation. Health programs and campaigns preventions are highly advised to increase the awareness of Pediculosis capitis with an effective strategic plan to control, manage, and prevent this disease.     

Seasonality and infestation pattern of epibiosis in the beach mysid Archaeomysis articulata

Seasonal variation and the infestation pattern of epibiosis in the beach mysid Archaeomysis articulata Hanamura, 1997, were studied based on intertidal samples over 1 year on a sandy beach in Ishikari Bay, northern Japan. The mysid-peritrich ciliate association was a year-round phenomenon in Ishikari Bay and the prevalence of infestation varied from 49 to 100% (average: 92%) during the investigation; no significant seasonal trend was noted. Incidence of infestation in smaller mysids (<5 mm) was significantly lower than in larger mysids (>5 mm). The number of ciliates carried by adult, mostly ovigerous, females was greater than that by adult males. Last stage embryonic larvae were occasionally infested by ciliates, but early stage larvae were absolutely free from epibionts. Dense infestation of epibionts was not correlated with the abundance of mysids, hence the impact of ciliates on natural populations of mysids is assumed to be insignificant.     

Spatial pattern of reinfestation by Triatoma infestans in Chancanif, Argentina.

We examined the environmental correlates and the spatial pattern of infestation by Triatoma infestans, a vector of Chagas disease, in a rural area of Argentina five years following an insecticidal campaign. Patterns of infestation were identified in an entomological survey, as mapped with high-resolution satellite imagery and analyzed in a geographic information system. Logistic regression was used to relate infestation to observed household characteristics as well as the location and density of households. Location was the most significant predictor of infestation for domiciles. For peridomestic structures surrounding the domiciles, the combination of location and the presence/absence of goat pens was most significant. In considering any infestation, whether domiciliary or peridomestic, the combination of location, presence/absence of animal pens, and the type of household construction were found to be most significant. Using these statistical relationships to back-classify the field data resulted in accuracies between 85% and 87%. A map of infestation probability for the town of Chancaní was developed from the logistic regression.     

厦门市入侵害虫芒果壮铗普瘿蚊（双翅目：瘿蚊科）为害情况调查

【背景】芒果壮铗普瘿蚊是厦门市2000年发现为害芒果树的一种入侵害虫,并呈现逐年扩散趋势。【方法】本文于2009～2010年针对厦门市7个代表性地点（集美大学周边、同安小西门、思明湖滨南路、东渡周边、鼓浪屿、海沧沧虹路、杏林镇）的芒果壮铗普瘿蚊的为害率、为害程度及羽化率情况进行调查。将叶片上的虫瘿密度划分为3个等级,分别为1～50、51～100、〉100个·片-1。【结果】2009年春梢叶片受害率最高的为海沧区（95.46%）,但与思明区（94.00%）、同安区（80.09%）没有显著差异,集美（22.50%）被害率显著低于其他区域;2009年秋梢海沧区叶片受害率达到97.05%,显著高于其他区域,集美受害率最低（18.00%）;2010年春梢叶片受害率较低,均在3%以下,各区域差异不显著。2009～2010年的为害程度主要集中在1～50个·片-1,2009年春各区域的为害率普遍高于2009年秋和2010年春。羽化率比较结果表明,各区域瘿蚊的羽化率相当,2009年春均在80%左右波动,2009年秋为60%～94%,2010年春各区域瘿蚊的羽化率明显低于2009年。【结论与意义】由于厦门市2010年春气温明显低于2009年,造成调查时为害情况较轻。但从总体上看,芒果壮铗普瘿蚊在厦门市的发生情况较为严重。本研究可以为明确该虫的扩散趋势及制定防治措施提供依据。     

Poison-based commensal rodent control strategies in urban ecosystems: some evidence against sewer-baiting

Sewers are historically considered the main reservoir for commensal rodents, posing threats to urban ecosystem health. Aboveground rodent signs are often assumed to give clues to high sewer infestation, which can chronically restock surface areas. Thus, current sewer-baiting programmes are mostly reactive, responding to increased surface infestation. Conversely, proactive sewer-baiting (regardless of infestation levels) is often disregarded because cost-effectiveness is not always addressed. We explored the extent to which the surface infestation is related to rodent feeding activity on sewer and surface baits by analysing a set of proactive bait records in Bologna city, Italy. Sewer bait intakes were significantly lower than surface ones, suggesting that proactive sewer-baiting is generally less effective. As surface infestation increased, probability of recording surface bait intake increased significantly but this was not reflected by increased sewer bait intake, suggesting that surface infestation is not always a reliable indicator of sewer infestation. This should discourage the use of reactive sewer-baiting as a routine strategy. Poison-based control programmes by themselves are scarcely predictable and strategically limited, and ideally they should be handled within an ecologically based integrated pest management approach for achieving satisfactory results.     

The response of cattle vaccinated with hypodermin A to a natural infestation of Hypoderma bovis and Hypoderma lineatum.

In this study, we have determined whether immunization with hypodermin A (HA), associated with various adjuvants, could provide protective immunity for calves when challenged with a natural hypoderma infestation. Groups of naive calves were vaccinated with HA antigen alone or with adjuvants [Freund's incomplete adjuvant (FIA) or alumina phosphate (AP)]. Subcutaneous injection with HA antigen with or without adjuvant did not significantly protect calves against a natural hypodermosis infestation. The humoral response during the infestation period was evaluated by ELISA. A significant earlier and greater response was induced in groups vaccinated with HA alone and HA combined with FIA. These results indicate that HA, in this vaccination protocol, induces a very incomplete protection in calves exposed to a natural infestation.     

Role of hydroperoxide lyase in white-backed planthopper (Sogatella furcifera Horváth)-induced resistance to bacterial blight in rice, Oryza sativa L.

A pre-infestation of the white-backed planthopper (WBPH), Sogatella furcifera Horváth, conferred resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae ( Xoo ) in rice ( Oryza sativa  L.) under both laboratory and field conditions. The infestation of another planthopper species, the brown planthopper (BPH) Nilaparvata lugens Stål, did not significantly reduce the incidence of bacterial blight symptoms. A large-scale screening using a rice DNA microarray and quantitative RT-PCR revealed that WBPH infestation caused the upregulation of more defence-related genes than did BPH infestation. Hydroperoxide lyase 2 ( OsHPL2 ), an enzyme for producing C₆ volatiles, was upregulated by WBPH infestation, but not by BPH infestation. One C₆ volatile, ( E )-2-hexenal, accumulated in rice after WBPH infestation, but not after BPH infestation. A direct application of ( E )-2-hexenal to a liquid culture of Xoo inhibited the growth of the bacterium. Furthermore, a vapour treatment of rice plants with ( E )-2-hexenal induced resistance to bacterial blight. OsHPL2 -overexpressing transgenic rice plants exhibited increased resistance to bacterial blight. Based on these data, we conclude that OsHPL2 and its derived ( E )-2-hexenal play some role in WBPH-induced resistance in rice.