Prevalence and diagnosis of insect allergy and its therapeutic considerations

Insect sting can cause allergic response which results in pain, itching, redness and swelling. Furthermore, people allergic to stinging venom can face a more serious reaction i.e. anaphylaxis (Bernstein et al., 2011; Department of Health, 2016). Insect Allergy is also known as Hymenoptera Venom Allergy (HVA). This  induces large local reaction (LLR) or systemic allergic responses which affect a local area of more than 10cm within 24 hours at the sting site. Hymenoptera belongs to sub-order Aculeate category and includes super-families of Apoidea, Vespidae, and Formicidae (Jutel et al 2013).

The common names of insects in these families include:

• Yellow Jackets,
• Honeybees,
• Paper wasps,
• Hornets and
• Fireants (Jutel et al 2013).

The allergens which instigates allergic response with honeybee sting are phospholipase A2 (Api m 1) and hyaluronidase (Api m 2). Allergens in yellow jacket’s venom include:

• phospholipase A1 (Ves v 1),
• hyaluronidase (Ves v 2) and
• antigen 5 (Ves v 5).

Allergens in Fireants include:

• Sol r 2 (a phospholipase),
• Sol i 2 and
• Sol i 3 (Jutel et al 2013).

Prevalence of insect allergy

The global prevalence of insect allergy is approx. 1-7% (Heddle & Golden, 2015) with more prevalence found among middle and older-aged patients (Decker et al., 2008; Patel et al., 2011). The average prevalence of large local reaction is 2.4% -24.6% in the general population and up to 38% in beekeepers.

In the US, the common insect allergies are caused by Paper wasp, Yellow Jacket, Hornet and European Hornet, with a prevalence of 0.5- 3.3%. According to the records from world allergy organisation, at least 40 deaths per year in the US occur due to insect allergy.

In comparison, the prevalence percentage of UK is higher as the allergy has been reported by 11.5% people (Turner et al., 2015). The most common among all the key allergies include bee-wasp which is found prevalent in 2% of the population. Other than that only hornet is found to have an allergic reaction to the UK population (Jutel et al 2013). Furthermore, in the case of Australia, nearly 15-25% of the population is diagnosed with different insect allergies. The major cause of allergy being from ant stings i.e. Australian Jack Jumper Ant (Heddle & Brown, 2004).

On the other hand, in Japan, more than half of the sample population is affected by insect allergy affecting 61.5% of the total population, leading to high fatality rate as well (Tang, Osborne, & Allen, 2009).

The percentage further increases in the case of Africa, where prevalence was found to be 28%. Among the common allergies, the most common allergic reactions are caused by black flies, which are responsible for the transmission of onchocerciasis (Burns, 2016).

This is followed by prevalence in Indian sub-continent wherein 30% of Indians are suffering from insect allergies mainly because of huge diversity, however lack of basic prevention strategies. The most common insect allergy prevalent in India is due to honeybee stings. The common allergies prevalent across the case countries are summarised in the table below:

Diagnosis of insect allergy

In the case of a sting, the diagnosis is done through limited swelling in the local area. However, only in a minority of cases, the swelling can prolong by 24-48 hours. Furthermore, only a small percentage of individuals develop systemic reaction beyond the area of sting leading to IgE mediated reaction. Thus, diagnosis in case of insect allergy is imperative for the treatment of individuals. Among the common diagnostic tests, a skin test is the most common (90-95% accuracy) (Bernstein et al., 2011).  However, it needs specialist evidence since the availability of venom-specific IgE is difficult. Thus, in this case, sensitivity for types of insects should be carried.

Consequently, another test which is common in the diagnosis of the disease is the measurement of Mast Cell Tryptase. This needs to be measured within 30- 38 hours of the sting bite in order to conclude an allergic reaction (Hamilton, Wisenauer, Golden, Valentine, & Adkinson, 1993). Lastly, another diagnostic tool is the stinging challenge but applicability in clinical practice is not wide. In India, blood test and skin test are most commonly used to determine insect-specific allergic reactions.

Therapeutic considerations

In mild cases of insect allergy, antihistamines are given with oral prednisolone. Further, H1, and H2 antihistamines are used to enhance the effect of diphenhydramine (“Insect sting allergy | Health24,” n.d.). However, in case of severe infection, venom immunotherapy is given as a treatment procedure. Epinephrine injection is also considered as management for the allergy (Demain, Minaei, & Tracy, 2010). A local reaction such as cold compresses, elevation of the affected limb, anti-inflammatory and oral corticosteroids can also be used (Karabus, 2012).

In India, Japan and UK, several medicinal plants are used for the treatment of insect bite. They take the extract from the plant such as terpenoids, flavonoids, tannins and cardiac glycosides. These plants have a triple effect of anti-bacterial, anti-inflammatory and anti-viral reaction (Lalrinzuali & Chandra, 2015).

Improving knowledge and avoidance of insect 

In the past decade, the number of patients of insect allergy has increased. However on the other hand mortalities have decreased mainly due to improved diagnosis and treatment procedures. Currently, the socio-economic burden of insect-related allergies is unknown. However it is mostly a result of an occupational hazard thus, avoidance can only reduce the exposure. Currently, there is a need to increase knowledge about the natural history, risks and treatment mechanisms of insect allergy. Therefore, improving knowledge will reduce adverse and socio-economic consequences.

References

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