Evidence of Parthenium Sensitivity Across All Seasons in Patients from Middle and Lower Gangetic Regions.

Sir,

We read with interest the article by Verma et al. on the seasonal variation in contact hypersensitivity to Parthenium where the lowered mean titer of contact hypersensitivity correlated with increased sensitivity to Parthenium in summer.[1] The study conducted involved patients from Delhi and suburbs which would be in the upper Ganga plain. However, incidence of allergic rhinitis/asthma with pollens has increased in the past two decades in the entire Gangetic region. Studies from the Bose Institute, Calcutta, in early 2000 showed that Cyperaceae and Parthenium pollens were not present in air during winter.[2] Of 102 patients, 27% had Grade 1+ response to Parthenium on skin test while 7.8% had 2+ to 3+ skin test response,[2] which was only 3% in a study concluded in 1997.[3] We sought to understand the trend of total and Parthenium -specific IgE responses across 4 seasons to see if there was a correlation between season and IgE levels among patients in the middle and lower Gangetic plains (Bihar, Jharkhand, West Bengal, and Bangladesh).

A retrospective study was carried out on selected patients who visited the Allergy and Immunology clinic tested for total IgE and ragweed (w1 ImmunoCAP) specific IgE between October 2013 and September 2015 (two winters and two summers). The extensive sequence homology between ragweed and Parthenium makes it a good choice for the ImmunoCAP-based fluoroenzyme immunoassay that provides a quantitative measure of specific IgE response (>0.35 kUA/L is positive).[4] 196 patients (121 males, 75 females; mean age 22.8 years) with clinical symptoms of allergic rhinitis/asthma had mean total IgE at 748.47 kU/L and mean w1 spIgE 0.58 kUA/L. Of these, 50 patients (25.5%) had positive w1 spIgE (overall mean 1.95 kUA/L). The distribution data across the 4 seasons showed similar percentages of sensitized patients among all patients tested [Table 1], with slightly increased median w1 spIgE in the summer of 2015 (nonsignificant). The mean total IgE and w1 spIgE across 4 seasons are shown in Figure 1a and b. A single high value of w1 spIgE at 14 kUA/L may have increased the overall mean but Grubb's test (extreme standardized deviate) of all values did not show this value as an outlier. Figure 1b clearly shows that w1 spIgE (Parthenium equivalent pollen) levels peaked in the summer of 2015 compared to other seasons. This could either be due to increased temperatures in the summers or higher numbers of patients sampled; however, it is evident that w1 spIgE individual levels were higher in the last summer as compared to previous winters.

Table 1

Breakdown of all Parthenium-sensitized patients across the 4 seasons with median total IgE and w1 spIgE levels

Figure 1

(a) High mean total IgE level among parthenium-sensitized patients (with error bars), nonsignificant. (b) Rising mean w1 specific IgE level among sensitized patients (with error bars), nonsignificant

In conclusion, the article by Verma et al. and our specific IgE data thus confirm that Parthenium sensitivity both at the humoral immune system (IgE levels) and at the cellular level (confirmed by patch tests, Type IV hypersensitivity) has increased over the past three decades. Strategic planning is now seriously required to control the spread of Parthenium hysterophorus, especially in the midst of rapid urbanization and increasing spectrum of allergic disorders affecting this region.

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Conflicts of interest

There are no conflicts of interest.