[Emergency immunotherapy: snake and scorpion antivenoms]

Neutralization Capacity of Tissue Alterations Caused by the Venoms of the Most Dangerous Scorpions in North Africa Using a Selective Antivenom

In North Africa, scorpion stings pose an urgent public health problem, particularly for children with high morbidity and mortality rates. The main species implicated are the Androctonus mauretanicus (Am), Androctonus australis hector (Aah), and Buthus occitanus (Bo). Immunotherapy is the specific therapeutic approach aimed at directly neutralizing toxins, despite their severity and rapid diffusion. In the present study, we evaluate, histologically and immunohistologically, the neutralization potency of the selective antivenom produced against, among other species, the Am, Aah, and Bo at the level of the tissue alterations in Swiss mice, as experimental subjects. Firstly, the lethal doses 50 test was conducted to assess the venom's toxic activity, and then the median effective dose of the antivenom was determined against each venom. The histological and immunohistological analyses were performed by injecting the sublethal dose of venom, the complex venom and antivenom, or the antivenom 2 h following inoculation of venom. Our study revealed the highest toxicity of the Am, followed by the Aah and then the Bo venom. The neutralizing ability and effectiveness of the antivenom to completely or partially neutralize the tissular damages were demonstrated in all organs studied: brain, heart, lungs, liver, and kidneys. Our results highlighted the important cytoplasmic and membranous staining in the heart compared to the brain tissue for the three scorpion venoms. Therefore, the scorpionic antivenoms are able to reach their target even at the tissue level. Immunotherapy represents the specific and recommended treatment against the scorpionic stings in North Africa.

European viper envenomings: Assessment of Viperfav™ and other symptomatic treatments

The treatment of European viper envenomings is based on IV antivenom infusions. Viperfav™ contains purified F(ab')(2) fragments of equine antibodies, and a 4 ml vial can neutralize 500-1000 mouse LD50 of Vipera aspis, V. ammodytes and V. berus venoms and is known to be safe and efficient. Assessments of Viperfav™ (dosage and timing of infusions) and of symptomatic treatments such as low-molecular-weight heparin (LWHM), corticosteroids and the routine use of antibiotic therapy have not as yet been reported.

OBJECTIVES

The objective was to compare the efficacy and safety of Viperfav™ as a function of the time to infusion and to assess other symptomatic treatments given for European viper bites such as antibiotics, corticosteroids and LWMH.

METHODS

A prospective case review study of viper envenomings treated with Viperfav™ was compiled by the Angers Poisons Centre. The endpoints chosen were as follows: duration of hospital stay, complications (haematoma, infection) and persistent functional discomfort on day 15. Statistical studies were based on multivariate data analysis (MVA).

RESULTS

268 moderate or severe envenomings (Grades II and III) recorded in adults and children between 1999 and 2009 were included in the study. A time to the Viperfav™ infusion < 10 h after the bite (179 patients vs. 72) significantly reduced the incidence of haematomas (OR 2.3; p < 0.006), functional discomfort (OR 3.7; p < 10 - 4) and length of hospital stay (OR 2.1; p < 0.03). Multiple doses of Viperfav™ (2 or 3 vials in 22 patients vs. 246 treated with 1 vial) did not improve the selected endpoints. Routine antibiotic therapy was prescribed in 102 patients (vs. 166 patients without) and no significant difference was seen with respect to the endpoints. Moreover, no local or systemic infections were recorded in the non-antibiotic group. Corticosteroids were prescribed in 36 patients (vs. 232 without) but they did not significantly improve the endpoints or oedema. LMWH in 32 patients (vs. 236 without) increased the length of hospital stay (OR 3.2; p < 0.009 and the level of significantly persistent functional discomfort at day 15 (OR 3.7; p < 0.003).

CONCLUSIONS

A single infusion of Viperfav™ (one vial) was effective whatever the grade of envenomation, and multiple doses did not improve the outcome. Viperfav™ was most effective when given soon (< 10 h) after envenoming. The routine use of antibiotic therapy was not necessary. Corticosteroids did not improve the endpoints selected, and we do not recommend the use of LMWH as this increased persistent functional discomfort and the length of hospital stay.

Epidemiology of snakebites in Europe: a systematic review of the literature

Snakebites are rare medical emergency cases in Europe but may sometimes be severe and lead to complications. A better knowledge of snakebite epidemiology may help health authorities to better understand therapeutic requirements, especially concerning antivenoms, and thus improve treatment of snakebite. An extensive literature search for studies and articles published between 1970 and 2010 was performed. Both indexed and non-indexed articles were examined, the analysis of which took into account the heterogeneity between the studies and weighted the studies according to size of the study population covered. Most of the articles involved hospitalized patients who represented more than 90% of snakebites. Incidence, mortality and population at risk were estimated after stratification into three regions (northern, central and southern Europe) based both on viper species distribution and climatic characteristics. There was no significant variation in incidence from the north to the south of Europe. In the whole of Europe, including European Russia and Turkey, the annual number of snakebite cases was estimated at 7992 [CI 95% = 6860-9178] bites, out of which approximately 15% were considered severe (grade 3). These bites usually occurred between May and September, with a more dispersed distribution in southern Europe. The average number of deaths per annum was 4 [0.7-7.7]. Children and male victims are more affected, contrary to what one would expect given their respective proportion in the entire population. Both upper and lower limb bites were recorded at an equal frequency while the bites in other parts of the body were very rare. Immunotherapy was prescribed in one out of three snakebites in Europe, with a very high geographical variability, in spite of excellent tolerance, at least considering highly-purified immunoglobulin fragments. Snakebites are uncommon in Europe but can cause life-threatening envenomation. Fragments of highly-purified immunoglobulins are now very well tolerated and dramatically reduce both severity and mortality of snakebites when used in treatment.

[Guidelines for the production, control and regulation of snake antivenom immunoglobulins]

Although frequent and severe, envenomations represent a neglected public health problem in most of the developing countries. Access to antivenoms is poor, mainly in Sub-Saharan Africa, and remains a major concern to World Health Organization (WHO). Since 2007, WHO committed international experts to propose guidelines aiming to improve the manufacture, quality control, registration and use of antivenoms. These guidelines, which will published soon, should promote access to antivenoms, and their use by health services, leading in the short term to a significant decrease of snakebite morbidity and mortality.