Australian pine Pollen
Summary
Australian pine (Casuarina equisetifolia) is a wind pollinated, drought tolerant tree with rapid growth, attaining a height ranging between 8 – 35 m. Its vegetation is usually seen in sub-tropical coastal areas, near the sea level. Its flowering season occurs from February through May. This tree is spread across more than 60 countries like China, Africa, Malaysia, the US, Europe, etc. Exposure to Australian pine pollen may induce allergic reactions such as allergic rhinitis, asthma, and atopic dermatitis in sensitized individuals. A study has identified a 17 kDa allergenic protein from Australian pine pollen, homologous to Bet v 1 (PR-10) birch allergen. Australian pine pollen has exhibited cross-reactivity with pollen from species of Betulaceae and Fagaceae family and unrelated species such as Quercus and Alnus.
Epidemiology
Worldwide distribution
Surveys have shown Australian pine (Casuarina equisetifolian of order Fagles) pollens triggering allergic reactions, particularly in the northern hemisphere's tropical areas
Njokuocha and Osayi (2005) conducted a study in Nsukka (Nigeria) to identify allergic airborne particles in the atmosphere. Out of 2676 total pollen grains counted, 30 plant families and 33 pollen types were identified. Among these 33 types of pollen, 10 belonged to generic level and 23 to specific level. The study observed that pollens and fungal spores dominated the allergenic particles. Moreover, Australian pine pollen was found to be one of the most important causes of allergic rhinitis (AR).
Mandal et al (2008) conducted a study in Calcutta, India, to identify the frequency of airborne pollen and the taxa that cause significant sensitization. Skin prick tests (SPT) were performed for the most common pollen types in patients with pollinosis conditions. Casuarina contributed around 5.76%, among other pollen taxa.
Three hundred eighty children aged 9 to 14 years, with (n =97) or without (n=107) asthma, participated in a study in Brisbane, Australia. The study analyzed SPT results to 15 commercial allergens. Among asthmatic children, 22% showed a positive response to Australian pine.
Route Of Exposure
Main
The main route of exposure to this pollen is through inhalation.
Clinical Relevance
Several potent airborne pollen grains acting as bio-pollutants may trigger or enhance various respiratory and cutaneous allergic diseases such as bronchial asthma, bronchitis, naso-bronchial allergy, AR, conjunctivitis, dermatitis, and upper respiratory tract infection in sensitive individuals. Australian pine is one such source that produces aeroallergens that may be responsible for inducing respiratory symptoms and skin allergies.
Allergic rhinitis
A study compared the relationship between the pollen counts and documented allergy-related cases in Nigeria. The pollen counts were found to influence allergy (43.08%), upper respiratory tract infection (21.84%), AR (19.51%), and bronchitis (18.11%). Moreover, a significant strong positive correlation between the pollen of Australian pine and AR was observed.
Asthma
A study conducted among 142 patients (3 to 55 years old) with AR and asthma in Mexico City analyzed the frequency of sensitization to Australian pine pollen. Among 142 patients, 44 were children and 98 adults. The study concluded that eight children (18.18%) and 35 adults (35.7%) had a positive SPT to Australian pine pollen.
Atopic Dermatitis (AD)
A recent study found that 30% of the population is suffering from one or more allergic diseases such as bronchial asthma, AR, and AD that are increasing worldwide, including India. All India Coordinated Project on Aeroallergens and Human Health discovered the quantitative and qualitative prevalence of aerosols at 18 different country centers. Among other airborne pollen, Australian pine was predominantly present.
Prevention And Therapy
Prevention strategies
Avoidance
One of the main measures to be taken is to cut down the amounts of pollen entering the respiratory system. During pollen season, allergic patients are suggested to stay indoors or wear masks outdoors to keep away from pollen allergens. In worse situations patients may be suggested to move to a non-pollen area.
Cross-Reactivity
Studies have shown strong cross-reactivity between Betulaceae and Fagaceae. Also, a study has shown that children sensitive to tree pollen gave positive responses to skin tests due to cross-reactions from different families, that is, Quercus, Alnus, and Casuarina. The study observed positive reactions even during low pollen concentrations.
References
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