RESUMEN
Snake antivenom is the only specific treatment for snakebite envenoming, but life-threatening anaphylaxis is a severe side effect and drawback for the use of these typically mammalian serum products. The present study investigates the hypotheses whether serum IgE antibodies against the epitope galactose-alpha-1,3-galactose (α-gal) located on the heavy chain of non-primate mammalian antibodies are a possible cause for hypersensitivity reactions to snake antivenom. Serum samples from 55 patients with snakebite envenoming were obtained before administration of snake antivenom and tested for serum IgE (sIgE) against α-gal and total IgE. Early anaphylactic reactions (EARs) during the first 3 h after antivenom administration were classified into mild, moderate or severe and correlated with the presence of sIgE against α-gal. Fifteen (27%) out of 55 patients (37 male, 18 female, median 34 years, range 9-90 years) developed EARs after antivenom administration. Eleven, three and one patients had mild, moderate and severe EARs, respectively. Serum IgE against α-gal was detected in 17 patients (31%); in five (33%) out of 15 patients with EARs and in 12 (30%) out of 40 patients without EAR (Odds Ratio = 1.2; 95%-confidence interval: 0.3-4.2) with no correlation to severity. Although the prevalence of serum IgE against α-gal was high in the study population, very high levels of total IgE in the majority of patients question their clinical relevance and rather indicate unspecific sIgE binding instead of allergy. Lack of correlation between α-gal sIgE and EARs together with significantly increased total IgE levels suggest that sIgE against α-gal is not the major trigger for hypersensitivity reactions against snake antivenom.
RESUMEN
Snakebites are a seriously neglected public health problem in Lao PDR. Community-based cross-sectional surveys in two districts of Savannakhet province in Southern Laos revealed an incidence of up to 1105 snakebites per 100,000 persons per year. In contrast the number of snakebite patients treated in district and provincial hospitals are low. In order to improve health care for snakebite victims, antivenom was introduced to Savannakhet provincial hospital in July 2013 and medical staff has been trained in management of venomous snakebites at the same time. After the intervention the number of snakebite patients treated at the provincial hospital increased significantly from 4 patients in 2012 to 158 snakebite patients between July 2013 and November 2015. They were included into a prospective, consecutive case series. Median age was 32 years (range 1.5-70 years) and male-to-female ratio 2.2:1. Forty patients were bitten by Malayan pit vipers, 26 by green pit vipers, 24 by cobras, including 3 cases of venom ophthalmia, 5 by kraits, 8 by non-venomous species and in 55 cases the snake could not be identified. Forty-three out of 158 patients received horse derived F(ab')2 antivenom from Queen Saovabha Memorial Institute (QSMI) in Bangkok. Twenty-three patients (53%) developed early adverse reactions (EARs) within one hour after antivenom administration, including 13 patients (30%) with severe anaphylaxis. This extremely high rate of severe EARs turns the use of antivenom into a risky intervention. In contrast a retrospective chart review from Chulalongkorn University in Bangkok found only 3.5% early reactions including 1.2% severe anaphylactic reactions using the same antivenom from QSMI between 1997 and 2006. The reason for this enormous difference remains unclear. A better understanding of the aetiology and pathophysiology behind antivenom induced anaphylaxis is crucial in order to identify patients at risk and to improve safety of antivenom administration.