Common Ragweed
Summary
Common ragweed (Ambrosia artemisiifolia) is an aggressive plant with its origin most probably from the regions of Northern America. It is recognized as a potential trigger for type I allergic reaction which generally occurs in the later parts of the summer and autumn seasons. It is recognized as a serious health issue in America and various countries in Europe. Allergic rhinitis (AR) due to hypersensitivity reaction to inhaled ragweed allergens, is a prevalent medical problem in all age groups including children, adolescents and adults. Numerous allergens of A. artemisiifolia are found out of which, 22 of them are already well recognized and 6 are tagged as major. Of all the allergens, Amb a 1 is considered as the allergen of paramount importance as 95% of ragweed sensitive individuals have increased levels of IgE and show positive findings to the skin tests. Allergen-specific immunotherapy (AIT), symptomatic medications and allergen avoidance are the main strategies for the prevention and treatment of allergic rhinitis and asthma due to A. artemisiifolia. Significant cross-reactivity exists between common ragweed and mugwort, marshelder or other grass pollens.
Epidemiology
Worldwide distribution
The wide penetration of ragweed into European countries has been found documented in the evidences. The Hungarian region of Carpathian Basin is the part with the maximum air pollution with common ragweed pollen in Europe, which ranges from 77 to 87% of the total pollen count. The air pollution due to this pollen is also a burgeoning issue in the countries like Italy and France. In the northern parts of Italy, there is an increasing trend of sensitization towards this particular aeroallergen. In Switzerland also, there is an increasing trend towards measured ragweed pollen counts in Geneva since starting of sampling in 1979. An interesting finding from a survey conducted by National Health and Nutrition Examination, about 26% of the individuals were sensitized to the pollen from ragweed in the US. It is also a principal allergen found in the Canada. In another study done in atopic patients, 44.9% of the individuals were found to be sensitized to the ragweed pollen.
Route Of Exposure
Main
The ragweed pollens are the airborne and the main route of exposure is through inhalation.
Clinical Relevance
Allergic rhinitis with or without conjunctivitis
The pollen from short ragweed is a major reason behind severe type I respiratory allergies, with the incidence of IgE sensitization continuously increasing. It is one of the major reasons for seasonal allergic rhinitis (AR) and associated conjunctivitis (AR/C) in the Northern parts of America. In the year 1989, around 45 percent of the sensitized patients to common ragweed developed respiratory symptoms in the form of rhinitis and bronchial asthma in late summer. After a few years, an increase in the percentage was observed up to 90 percent. Exposure to ragweed pollen majorly results in allergic diseases such as allergic rhinitis, asthma and allergic skin reactions.
Asthma
AR and asthma are some of the leading allergic conditions which are commonly found to be related to sensitization to the common ragweed pollen. This pollen was recognized well in the early 19th century as the major factor responsible for AR and asthma. Soon after that, the first eradication program was started in the 1940s by using herbicide. The asthma occurrence was observed in about 30 percent of the sensitized individuals which increased up to 40 percent in a short period of time.
Prevention And Therapy
There are main preventive strategies for asthma as well as rhinitis (allergic) such as allergen-specific immunotherapy (AIT), symptomatic medications and allergen avoidance.
Avoidance
This strategy effectively controls symptoms of allergy. However, it is extremely difficult to achieve complete prevention. There are various strategies such as the use of air conditioners, closing windows particularly during the day-time, as well as avoidance of outdoor activities amid pollen season at its peak.
Allergen immunotherapy
In one randomized controlled trial, adult patients with allergic rhinitis with or without conjunctivitis (AR/C) were included. They were randomized to receive either daily self-administration of 1.5, 6, or 12 units of ragweed AIT or placebo for a period of 52 weeks. Patients who received AIT of 12 units were able to tolerate it without any side effects.
Cross-Reactivity
The 4 major ragweeds including short, giant, western, and false strongly cross-react. Due to strong cross-reactivity between short, giant, western, and false ragweed species, it is not required to do skin tests or treat with multiple members instead a single choice suffices. A strong cross-reactivity is seen with ragweed and mugwort, marshelder or cocklebur.
Cross-reactive allergens (major) are identified in the short as well as giant ragweed. These allergens are not considered identical as their major differences in allergenicity are amongst Amb a 1-2 and Amb t 1-2 and other minor allergens.
References
- Chen KW, Marusciac L, Tamas PT, Valenta R, Panaitescu C. Ragweed Pollen Allergy: Burden, Characteristics, and Management of an Imported Allergen Source in Europe. Int Arch Allergy Immunol. 2018;176(3-4):163-80.
- Makra L, Matyasovszky I, Hufnagel L, Tusnády G. The history of ragweed in the world. Applied Ecology and Environmental Research. 2015;13:489-512.
- Oswalt ML, Marshall GD. Ragweed as an example of worldwide allergen expansion. Allergy Asthma Clin Immunol. 2008;4(3):130-5.
- Makra L, Juhász M, Borsos E, Béczi R. Meteorological variables connected with airborne ragweed pollen in Southern Hungary. International Journal of Biometeorology. 2004;49(1):37-47.
- Mandrioli P, Di Cecco M, Andina G. Ragweed pollen: The aeroallergen is spreading in Italy. Aerobiologia. 1998;14(1):13.
- Asero R, Weber B, Mistrello G, Amato S, Madonini E, Cromwell O. Giant ragweed specific immunotherapy is not effective in a proportion of patients sensitized to short ragweed: Analysis of the allergenic differences between short and giant ragweed. Journal of Allergy and Clinical Immunology. 2005;116(5):1036-41.
- Tosi A, Wüthrich B, Bonini M, Pietragalla-Köhler B. Time lag between Ambrosia sensitisation and Ambrosia allergy: A 20-year study (1989-2008) in Legnano, northern Italy. Swiss medical weekly. 2011;141:w13253.
- Turkalj M, Banic I, Anzic SA. A review of clinical efficacy, safety, new developments and adherence to allergen-specific immunotherapy in patients with allergic rhinitis caused by allergy to ragweed pollen (Ambrosia artemisiifolia). Patient Prefer Adherence. 2017;11:247-57.
- Creticos PS, Adkinson NF, Jr., Kagey-Sobotka A, Proud D, Meier HL, Naclerio RM, et al. Nasal challenge with ragweed pollen in hay fever patients. Effect of immunotherapy. J Clin Invest. 1985;76(6):2247-53.
- Bordas-Le Floch V, Groeme R, Chabre H, Baron-Bodo V, Nony E, Mascarell L, et al. New insights into ragweed pollen allergens. Curr Allergy Asthma Rep. 2015;15(11):63.
- Nolte H, Hébert J, Berman G, Gawchik S, White M, Kaur A, et al. Randomized controlled trial of ragweed allergy immunotherapy tablet efficacy and safety in North American adults. Ann Allergy Asthma Immunol. 2013;110(6):450-6.e4.
- Creticos PS, Maloney J, Bernstein DI, Casale T, Kaur A, Fisher R, et al. Randomized controlled trial of a ragweed allergy immunotherapy tablet in North American and European adults. Journal of Allergy and Clinical Immunology. 2013;131(5):1342-9.e6.
- Gadermaier G, Hauser M, Ferreira F. Allergens of weed pollen: an overview on recombinant and natural molecules. Methods. 2014;66(1):55-66.
- Weber RW. Patterns of pollen cross-allergenicity. J Allergy Clin Immunol. 2003;112(2):229-39; quiz 40.