Ragweed in Australia

Ragweed (Ambrosia spp.) is awell-recognised cause of fall allergic rhinitisand seasonal asthma in the Northern Hemispherecountries of United States and Canada. InAustralia the appearance of ragweed (Ambrosia artemisiifolia) was first recordedduring the 1930s in Queensland, ragweed hayfeverwas noted in 1959 and ragweed dermatitisdocumented in 1963. Aerobiology studies performedin the capital cities of Eastern and WesternAustralia have not demonstrated ragweed pollen.This study, performed in two towns in theNorthern Rivers area of New South Wales, closeto the Queensland border, documents the ragweedseason between November 1996 and December 1997in one of the towns, by monitoring the air usinga Burkard 7-day spore trap. Two hundred and sixvolunteers were skin tested to a range ofaeroallergens including pollen of ragweed (Ambrosia artemisiifolia) and Tibouchina, a treeflowering at the same time as ragweed. 34% ofvolunteers were skin prick test positive toragweed and 5.4% to Tibouchina. The ragweedseason commenced in the first week of March andextended to early May, with the peak day pollencount, 483/m³, present in the first week ofApril. Although many residents blamed thespectacular purple Tibouchina flowers for latesummer respiratory symptoms, most were sensitiveto ragweed and not Tibouchina.     

Ragweed pollen: The aeroallergen is spreading in Italy

Presently in Europe, ragweed pollen as an aeroallergen is not as important as Poaceae,Parietaria or Betulaceae, even if in some countries the plant is beginning to influence the local composition of the airborne pollen spectra. In northern Italy, the presence of ragweed airborne pollen has only been reported since the beginning of the 1980’s and it is increasingly spreading from year to year. Given this situation, the allergologists have begun to regard the potential risk of sensitisation to ragweed pollen with much attention. Up to now, such pollen has not been included in the routine allergological tests. In 1995 in some sites of northern Italy (Turin, Milan, Trieste), the concentration values of ragweed pollen were remarkable (∼ 20–30 p/m³) and on the increase with respect to the previous years. This investigation aims at focusing the atmospheric concentration trend on this new aeroallergen (Ambrosia sp.) in Italy from 1991 throughout 1995.     

Ragweed and mugwort pollen in Szczecin, Poland

Ragweed (genus Ambrosia) and mugwort (Artemisia vulgaris) pollen grains are known to be very potent aeroallergens, often noted to enter into cross reactions. The aim of the study was to analyse ragweed and mugwort pollen release in Szczecin (western Poland) during the period 2000–2003. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90% of the total catch. Of the 4 years studied, the lowest concentration of ragweed pollen was observed in 2000. In 2000, the annual ragweed pollen count was very high, threefold higher than in 2001. There was a high Ambrosia pollen count in 2003, with the highest daily value of 84 grains/m³. The mugwort pollen season started in the third 10-day period of July and lasted to the end of August in all of the years studied. Analysis of pollen deposition from different Szczecin city’s districts showed that the highest exposure to ragweed pollen allergens occurred in the Majowe district, which is related to the presence of numerous plants of Ambrosia in that district. The mugwort pollen deposition was more abundant in the Żelechowa district, which is an area with villas and gardens. Statistically significant correlations were found between the ragweed pollen count in the air and the maximum wind speed, air temperature and relative humidity and between the mugwort pollen count in the air and air temperature and relative humidity.     

Ragweed in the Czech Republic

During the last years, a well documented expansion ofragweed (Ambrosia artemisiifolia L., Ambrosia trifida L.) over the Mediterranean andtemperate Europe has been in progress. The currentdistribution of ragweed plants in the Czech Republicis summarized and the ragweed pollen concentration asmonitored by 12 pollen stations in the country isdiscussed. The present situation in the ragweed pollensensitization among children and adults with pollenallergy in Brno is described. So far no dangerousexpansion of ragweed plants in our country has beenobserved. Ragweed pollen concentration is occasionallysignificant in the Brno station only, other pollenstations are reporting insignificant amounts ofragweed pollen during August-September periods,although there has been a steady increase in ragweedpollen concentration in the Prague area over the lastfive years. Skin prick tests and/or specific IgEmeasurements with ragweed allergen were performed on94 children with pollen allergy in the Brno region in1995 and on 206, 210 and 229 adult allergic patientsin 1995, 1996 and 1997, respectively. Positive skinreaction or positive specific IgE to ragweed was foundin 22% children and in 25% (1995), 19% (1996) and 25% (1997) adults with pollen allergy. It isconcluded that ragweed does not seem to represent anyimminent major threat to the allergic population inthe Czech Republic until now, however, it remains apotentially very dangerous allergen.     

The occurrence of Ambrosia pollen in Rzeszów,Kraków and Poznań, Poland: investigation of trends and possible transport of Ambrosia pollen from Ukraine

Previous studies have shown that ragweed pollen arrives in Poland from sources in the south, in Slovakia, the Czech Republic, Hungary and Austria. It is likely that ragweed pollen also arrives from sources in the southeast (e.g. Ukraine). This hypothesis was investigated using 13 years of pollen data and back-trajectory analysis. Ambrosia pollen data were collected at three sites in Poland, Rzeszów, Kraków and Poznań. The amount of ragweed pollen recorded at Rzeszów was significantly higher than in Poznań and Kraków. This can be related to either a higher abundance of local populations of Ambrosia in south-east Poland or the proximity of Rzeszów to foreign sources of ragweed pollen. The combined results of pollen measurements and air mass trajectory calculations identified plumes of Ambrosia pollen that were recorded at Rzeszów, Kraków and Poznań on 4 and 5 September 1999 and 3 September 2002. These plumes arrived at the pollen-monitoring sites from an easterly direction, indicating sources of Ambrosia pollen in eastern Poland or Ukraine. This identifies Ukraine as a possible new source of ragweed pollen for Poland and therefore an important source area of Ambrosia pollen on the European Continent.     

Trend of herbaceous pollen diffusion and allergic sensitisation in Genoa, Italy

In order to investigate the relationship betweenallergenic load and allergic sensitisation prevalenceon a long period, we analysed the annual data ofherbaceous pollen airborne diffusion in Genoa(NW-Italy) for 17 years (1981–1997), with particularregard to the most important allergenic species:Poaceae, Parietaria, Artemisia, Ambrosia. Weevaluated the relative trend and compared it with theprevalence data of patients sensitisation to thesepollens in the same period.The analysis of annual pollen amount revealed asignificant rising trend (r = 0.73, p < 0.05) of Parietaria pollen (average 14.324 grains/m³/year),whereas Poaceae (2048/year) and Artemisia(170/year) pollen count did not show any significantchange. Ambrosia (average 70/year) has been rising since 1989 (r = 0.87, p < 0.05) and reached themaximum pollen count in the last three years.The prevalence of pollen sensitisation resulted to bevery high (about 75%) in our atopic patients withrespiratory symptoms and did not change significantlyin the years: Parietaria pollen allergy waspresent in about 70% of patients with at least oneSPT positive to pollens (and 55% of atopicsubjects), and this frequency, much higher than theone found in North Italy, showed low year-to-year variability.Among pollinotics patients, Poaceae cutaneoussensitisation was found at a quite stable rate in theabove mentioned period (about 51%), as well as thatto Artemisia pollen (8%). Ambrosia skinprick test positivity is very rare (about 0.5%),without any evident increase.The present study shows that, for some of theherbaceous species, we cannot demonstrate astraightforward relationship between the trend ofairborne pollen and the frequency of sensitisation inexposed people. However, in the case of Parietaria, the high level of pollen amount in theair is clearly related with the high rate of cutaneous positivity in patients, but it seems tosuggest a ``plateau' that is not modified by anyfurther increase in airborne pollen (perhaps forgenetic limiting factors). On the other hand, Ambrosia pollen count, even if increasing in Genoa'satmosphere, could still be too low, and it would takesome more time to cause allergic sensitisation in exposed people.This kind of study, pointing out the influence ofairborne allergen exposure on hypersensitivitymechanisms, should be extended in time and world-wideto obtain general conclusions.     

Quantitative dynamics of Ambrosia pollen grains in Bulgaria

The aerobiological study of the Ambrosia pollen in Sofia, Bulgaria began in 1991. The quantitative dynamics of Ambrosia pollen grains during the last seven years was determined by Chebishev's method of parabolic interpolation with orthogonal polynoms. Thesensitization to ragweed pollen was investigated in random groups of patients with clinical manifestation of hay fever.This investigation proves the previouslyobserved tendency of an increase in thespreading of Ambrosia pollen in Bulgaria.     

Air and surface soil samples – two different pairs of shoes? Comparing the pollen spectrum on different days of the pollen season

The pollen spectra of air and surface soil samples from a rooftop (at 14 m) and from ground level (at 1.6 m) in the suburbs of Vienna (Austria) were compared. Two soil samples and two air samples were taken on four different days to account for possible differences: in winter when no pollination occurred (reference day), in spring during the main flowering of Betula (birch day), in spring/summer during the main flowering of Poaceae (grass day), and in autumn during the main flowering of Ambrosia (ragweed day). Thirty-five different pollen types were used to describe the pollen spectra. Frequencies of certain pollen types reflect a seasonal impact on both the surface soil and air samples and show a similarity between air and soil samples on most of the days. However, the seasonal impact is higher in the air samples and shows a high consistency for ground and rooftop level. Kendall’s tau correlation coefficients further substantiate the similarities of the samples especially for the pollen season days. Exceptions include the winter day when pollination was low and the air samples recorded nearly no pollen at all, and the ragweed day when Ambrosia pollen was abundant in three of four samples but not in the ground surface soil sample. Thus, (1) air and surface pollen samples record similar signals during the pollen season but not during the ragweed and winter season and (2) air and surface pollen samples show the impact of local vegetation also in pollen traps located at different heights.     

Airborne ragweed (Ambrosia artemisiifolia L.) pollen concentrations in Croatia, 2002–2004

The aim of this study was to determine the onset, length and end of the ragweed pollen season, taking into account diurnal, day-to-day, monthly and annual pollen variations, the effect of some meteorological parameters on atmospheric pollen concentrations and possible differences in the airborne pollen season and concentration due to sampling site. Airborne pollen was collected at three sites in central Croatia (Zagreb, Samobor and Ivanić Grad) during three pollen seasons (2002–2004). Seven-day Hirst-type volumetric pollen traps were used for pollen sampling. Ragweed pollen was the third most abundant pollen type to occur in the atmosphere of central Croatia. Total Ambrosia pollen concentration was the highest in the 2003 pollen season and the lowest in 2004 at all sampling sites. Maximum emissions were restricted to August and September. Intradiurnal periodicity showed a peak from 1000 to 1200 hours. The concentration of ragweed pollen during the pollen season was greatly influenced by temperature and precipitation: on rainy days accompanied by temperature decline, the air pollen concentration decreased abruptly. The results of this study are aimed at helping to alleviate the symptoms of allergic reactions in individuals with ragweed pollen hypersensitivity, thus improving their quality of life.     

Concentration of IgE in children during ragweed pollination season

Genetic and environmental factors are responsible for running allergic diseases. The aim of this study was to compare the values of total- (t-IgE) and allergen-specific IgE (s-IgE) to Ambrosia artemisiifolia L. (Amb a) in children with sensitization to Amb a during ragweed pollination season, who experienced seasonal symptoms of allergic rhinitis (rhinorrhea, post-nasal drip, nasal congestion, itching, sneezing) and asthma (coughing, especially at night, wheezing, shortness of breath, chest tightness). Ragweed pollen grains were collected in Virovitica (rural area) and Zagreb (urban area)—cities with the same geographical width and elevation—during ragweed pollination seasons (July–October in 2006 and 2007), and their count was estimated. Concentration of t-IgE and s-IgE in pollination season was determined in serum of children with symptoms of allergic diseases. The total count of ragweed pollen grains (PG) differed significantly between Virovitica and Zagreb in both years, 2006. and 2007. In Virovitica it was significantly greater than in Zagreb. There was no statistically significant seasonal difference in both, t-IgE and s-IgE, respectively. No correlation was found between pollen grain count and the concentration of IgE’s. To clarify the induction of IgE synthesis in children with sensitization to Amb a, further studies are needed.     

Ragweed evidence in Brianza (a hilly area North to Milan)

Summary Since 1982 we have been monitoring allergological pollen, by means of a Lanzoni pollen trap VPPS 2000. In 1988 we detected the ragweed pollen for the first time, and subsequently in 1989 and in 1990.In 1988 it had been monitored from 16/8 to 26/9 (highest concentration 66.5 gr/m³/24 h on 3/9), in 1989 from 7/8 to 23/9 (highest concentration 30.0 gr/m³/24 h on 10/9) and in 1990 from 3/8 to 23/9 (highest concentration 80.9 gr/m³/24 h on 2/9). During the same years the prick test for ragweed pollen turned out to be positive in 27 patients out of 1526 (1.76%) in 1988, in 25 patients out of 1517 (1.64%) in 1989 and in 56 patients out of 1614 (3.41%) in 1990.The presence of specific IgE turned out to be positive in 12 patients out of 189 (6.35%) in 1988, in 17 patients out of 195 (8.71%) in 1989 and in 22 patients out of 230 (9.56%) in 1990.During out 3-years investigation, on the basis of the severity of symptoms and of the possible multi-sensitization, only 2 patients have undergone a specific immunotherapy to ragweed pollen.Our data confirm the presence of ragweed pollen in Lombardy, even if the sensitization is low in our population and the clinical significance of ragweed pollinosis is even lower.Nevertheless the high sensitizing power of this pollen makes a higher incidence of ragweed pollinosis possible in coming years.     

Betulaceae and Corylaceae in Trieste (NE-Italy):Aerobiological and clinical data

Airborne pollen produced by Betulaceae and Corylaceaeis present in the Trieste area for a long period fromJanuary to June, but only in April it does representa considerable proportion (436 p/m³) of the totalpollen count (1193 p/m³). In the years considered (1995–1997), there was a gradual increase in thepollen count of Corylaceae and Betulaceae: frommaximum levels of 580 p/m³ in 1995 to 1218 p/m³ in 1997, and the taxon making the mostsignificant contribution to the pollen concentrationcurve was Ostrya carpinifolia. Sensitization to Betulaceae and Corylaceae wasanalyzed in 2213 subjects visiting our clinic betweenJanuary 1st 1995 and December 31th 1997, withallergic symptoms believed to be IgE mediated. Of thegroup, 1292 (58.4%) were atopic by skin prick testand 328 of them (25.4%) were sensitized to Betulaceaeand Corylaceae. Of the 328 subjects, 72.6% werecosensitized to Gramineae, 56.1% to Oleaceae, 42.1%to Compositae, and just over half to house-dust mites(52.1%). Only ten cases were mono-sensitized (3%).Of the subjects sentitized to Betulaceae andCorylaceae, 163 complained of rhinitis (72%) and 110of asthma (33.6%), often in association withrhinitis; 177 (54%) had only seasonal symptoms.Sensitization to Betulaceae and Corylaceae is high,but its role in inducing allergic respiratorysymptoms is difficult to evaluate because almost allpatients were sensitized to other pollen types. Inconclusion, the role played by this family of trees indetermining allergic respiratory symptoms could becomeincreasingly important in this geographical area inthe future, if pollen levels continue to rise at theirpresent rates. For the moment, sensitivity toBetulaceae-Corylaceae among the population is presentalmost exclusively in subjects sensitized also toother pollen types.     

An atmospheric pollen survey conducted during the winter in Minneapolis,Minnesota, USA

Few atmospheric pollen surveys have been conducted during the winter months in cities located in the midlatitudes. The purpose of this present investigation was to study pollen conditions during the winter in Minneapolis, Minnesota, a city that experiences cold temperatures and develops substantial snow cover. One hundred thirty‐three atmospheric samples were collected with a Rotorod Sampler between 11 October 1995 and 1 May 1996. Pollen was recovered in 109 samples, including 27 of the 40 samples collected in December and January. Twenty‐five types of pollen were observed during the study period; Cupressaceae (cedar/juniper), Ambrosia (ragweed) and Artemisia (sage/sagebrush) grains were most abundant during the period when local plants were not flowering. The weed pollen was most likely contributed by local sources, perhaps by dried flowers on dead plants. In contrast, the Cupressaceae pollen recovered in October and the early winter months is thought to have originated in the southern United States where several species of Juniperus flower late in the year. This study demonstrated that low but measurable concentrations of pollen occurred in the atmosphere throughout the winter.     

Nasal Sensitization with Ragweed Pollen Induces Local-Allergic-Rhinitis-Like Symptoms in Mice

Recently, the concept of local allergic rhinitis (LAR) was established, namely rhinitis symptoms with local IgE production and negative serum antigen-specific IgE. However, the natural course of LAR development and the disease pathogenesis is poorly understood. This study investigated the pathophysiology of mice with allergic rhinitis that initially sensitized with ragweed pollen through the nasal route. Mice were nasally administrated ragweed pollen over consecutive days without prior systemic immunization of the allergen. Serial nasal sensitization of ragweed pollen induced an allergen-specific increase in sneezing, eosinophilic infiltration, and the production of local IgE by day 7, but serum antigen-specific IgE was not detected. Th2 cells accumulated in nose and cervical lymph nodes as early as day 3. These symptoms are characteristic of human LAR. Continual nasal exposure of ragweed pollen for 3 weeks resulted in the onset of classical AR with systemic atopy and adversely affected lung inflammation when the allergen was instilled into the lung. Fcer1a ^−/− mice were defective in sneezing but developed normal eosinophilic infiltration. Contrary, Rag2 ^−/− mice were defective in both sneezing and eosinophilic infiltration, suggesting that T cells play a central role in the pathogenesis of the disease. These observations demonstrate nasal allergen sensitization to non-atopic individuals can induce LAR. Because local Th2 cell accumulation is the first sign and Th2 cells have a central role in the disease, a T-cell-based approach may aid the diagnosis and treatment of LAR.     

Ragweed – An allergy risk in Sweden?

Ragweed pollen, which is a major cause of allergic rhinitis in North America and during the last decades, also in parts of the European continent, has not been regarded as a risk in Sweden, since occurrences of Ambrosia have been rare and with two exceptions, ephemeral. During the last four years, however, long-distance transported pollen has been registered in South Sweden. Moreover, seeds are dispersed by man with birdseed and reports on ragweed plants growing at birdtables are becoming more and more common. In warm years, the fruits of these plants mature and are germinative. We argue that there is a risk that ragweed pollen may be a problem in the future in Sweden. Long-distance transport from the continent is likely to be increasingly more common, and in larger amounts, as ragweed is rapidly spreading in Europe. Among the plants now appearing within Sweden, selection is likely to favour phenotypes which are able to fulfil their life-cycle during the indigenous vegetation period, especially in a scenario of global warming.     

Ambrosia pollen in the air of Lublin, Poland

Studies on Ambrosia pollen concentrations were carried out in Lublin in the period 1995–2004. The effects of a number of meteorological factors were analysed. In the first period of the study, the gravimetric method was used (1995–1999), while in the second period, the volumetric method was applied. The results show an increasing trend in the amount of airborne pollen. The Ambrosia pollen season in Lublin lasts from August to October. Over a period of 5 years, the highest number of pollen grains was recorded in September (53%), followed by August (44%) and October (3%). There were wide variations in annual totals. The annual total pollen counts was 167–1180 grains, with the peak value in 2002. Maximum daily pollen concentrations (56–312 pollen grains m⁻³) were recorded in the first half of August and in the first half of September. On the days when high Ambrosia pollen concentrations occurred, the temperature was above 21°C and the winds were mainly from the southeast, south and east. Maximum intradiurnal concentrations of pollen grains occurred in the afternoon hours. These results indicate, to some degree, that Ambrosia pollen is transported for long distances before descent.     

Oleaceae in Trieste (NE Italy): aerobiological and clinical data

Oleaceae pollen concentrations in the Trieste area are low (<10%) compared to the total number of airborne pollen grains, with only one pollination peak at the beginning of June when the Oleaceae concentration reached 62% of the total pollen count in 1992. This peak was due to an exceptionally high pollination of olive trees in 1992, when airborne pollen concentration rose to 1357 pollen grains/m³ on June 3. Sensitization toOlea increased from 1989 to 1993, when it was present in 23.4% of symptomatic patients, but the role ofOlea in inducing allergic respiratory symptoms is difficult to evaluate because almost all patients were sensitized to other pollens, and in particular to Gramineae: only four subjects were sensitized toOlea alone (1.4%). Despite the low Oleaceae pollen counts, this pollinosis is increasing, probably because of increased cultivation ofOlea in recent years. However, although skin prick test positivity is common in polysensitized patients, its role in inducing sensitization and symptoms is presently less important than that of other pollens.     

Interannual variability of pollen productivity and transport in mid-North America from 1997 to 2009

Understanding the causes of interannual variability in atmospheric pollen concentration is an important but elusive goal for public health and environmental change. We analyzed long-term daily records of pollen counts from urban Kansas City, Missouri, USA collected from 1997 to 2009 for three pollen groups: Ambrosia, Poaceae, and a third group which is mostly composed of arboreal pollen types. The annual pollen index varied from 8,368 to 80,822 over the thirteen-year period. Although Ambrosia pollen is often thought to be associated with droughts and disturbance, years with high Ambrosia pollen were associated with high summer precipitation to the south of Kansas City. Years with high Poaceae pollen were associated with high spring precipitation to the south of the city. In support of the southern influence to Kansas City pollen, Ambrosia and Poaceae pollen mostly arrived on southern winds. In contrast to the other two pollen groups, the arboreal pollen was most associated with growing season precipitation to the east of Kansas City, although it was still highest on days with southern winds. Based on the correlations with climate, the severity of an upcoming allergy season may be predicted with early-season precipitation data, while short-term severity can be forecast from local weather patterns.     

Ambrosia elatior (L.) in Hungary (1989–1990)

Summary Weeds and among themAmbrosia are probably the most important vascular plants related to pollinosis in Hungary. Sampling was carried out in central (Budapest) and in southern (Paks, Szeged) Hungary. The results of two years (1989–1990) of aerobiological study onAmbrosia airborne pollen are reported. The highest percentage of airborne pollen was found in the mid-August to mid-September period, having a good correlation with clinical data on pollinosis. The implications of these results are considered in the context of forecasting and prevention of seasonal ragweed pollinosis.     

Levels of Ambrosia pollen in the atmospheric spectra of Catalan aerobiological stations

Ambrosia pollen is known as an importantallergen in North America, and more recently in someEuropean countries. From 1989 to 1995, the Ambrosia pollen levels detected at the stationsmonitored by the Aerobiological Network of Catalonia(Xarxa Aerobiològica de Catalunya, XAC) wereinsignificant. In 1996, a considerable althoughtemporary increase in the concentration of this pollenwas detected in the atmosphere over Girona, Barcelona,Bellaterra, Manresa, and Tarragona. Most of the Ambrosia pollen collected in 1996 was concentrated ina single day. Its appearance on that day wasattributed to long range transportation, caused byunusual conditions of atmospheric circulation, fromthe Lyon region in France where the species isabundant. This is the only day where concentrations ofAmbrosia pollen that may be dangerous to humanhealth have been reached. Ambrosia coronopifolia is the most abundantspecies of the genus in Catalonia, and although rare,its expansion is favoured by the fact that it growsthrough rhizomes and sprouts easily. It is, therefore,important to monitor the growth of its population andthe release of its pollen in order to predict theappearance of pollen levels that may precipitateallergic symptoms.