Clinical reaction to hymenoptera venom
Systemic reaction
Large local reaction
SYSTEMIC REACTIONS (ADULTS)
Epidemiology
Studies have shown that up to 94% of population are stung at least once by an insect belonging to hymenoptera family. The prevalence of sensitisation varies between 9.3 – 38.7% in adult population, large local reaction occur in 2.4 – 26.3%, systemic reaction in 0.3 – 7.5%, anaphylaxis in 0.6 – 42.8% and fatalities in 0.03 – 0.48 per 100,000 population per year.
Systemic reactions are usually of rapid onset and occur within minutes of the sting. They vary in intensity.
Mueller scale of clinical severity of venom reaction
Grade 0 local reaction only
Grade I generalised urticaria/ anxiety/ malaise
Grade II angioedema, chest tightness, vomiting, diarrhoea, abdominal pain, dizziness
Grade III shortness of breath, stridor, dysphonia, confusion
Grade !V hypotension, loss of consciousness, incontinence, seizures, feeling of impending doom
High risk factors for systemic reaction to venom
- Cardiovascular and respiratory disease (therefore age related)
- Preceding symptomatic or non-symptomatic sting within 2 months
- Bee venom more than wasp venom
- Stings in vascular areas – head and neck
- Baseline mast cell levels (including mastocytotsis)
Clinical assessment of a patient with systemic allergy to venom
Detail allergy orientated history should be obtained from the patient and any bystanders who have observed the reaction. Assessment should also include whether the type of hymenoptera insect (bee, wasp, etc) can be indentified.
Detail medical history should be obtained with particular emphasis on co-morbid diseases such as cardio-respiratory disease, immunodeficiency, pregnancy and drug therapy (beta blocker, ACE inhibitor and tricyclic antidepressants).
If the patient was admitted to an accident and emergency department for the sting reaction written information should be sought from accident and emergency or admission summery.
Explore by contacting laboratory whether the patient was admitted whether mast cell tryptase was carried out at the time of reaction.
Information about co-morbid condition should be obtained from the general practitioner or hospital notes.
Measurement of Blood pressure, resting pulse rate and peak flow should be recorded.
Investigations for a patient with systemic allergy to venom
Full blood count, renal function, total serum IgE, allergen specific IgE to bee venom & wasp venom and baseline mast cell tryptase. (additional tests allergen specific IgE to common aeroallergen may be carried out to establish atopic tendency).
Skin prick test for the suspected insect venom should be carried out with 10 mg/mL, 100 mg/mL and 300mg/mL. (additional sklin prick test for common aeroallergen may be carried out to establish atopic tendency)
Intradermal test should be carried out with 1 mg/mL of suspected insect venom.
If the identity of the suspected hymenoptera insect is not known, skin prick test and intradermal tests for both bee venom and wasp venom will be required.
Management of a patient with systemic allergy to venom
Advice should be given regarding avoidance of further stings.
Advice on wearing medical information bracelet.
Anyone with systemic reaction and has been sensitised to venom should be prescribed antihistamine, self-injectable Adrenaline to keep with them at all times.
If there is a further sting, the patient should take an antihistamine immediately, alert a friend or relative regarding the location of person and get prepared with Adrenaline.
Should patient develop choking sensation, shortness of breath, chest pain, faint – Adrenaline should be administered and to telephone for emergency ambulance to go to an Accident and Emergency department.
Patient should be reviewed regularly (6-12 monthly intervals) to monitor further sting reactions and knowledge of indications and technique for using self-kept drugs.
Venom immunotherapy (VIT) for a patient with systemic allergy
Venom immunotherapy is strongly recommended to patients who has a systemic anaphylactic reaction (Mueller Grade IV) and found to have IgE antibodies to venom (assessed by specific IgE, skin prick test and intradermal test).
Venom immunotherapy is recommended for patients who have a systemic reaction (Mueller Grade I, II and III) who have a high risk of future stings, high baseline mast cell tryptase level or may experience difficulty getting immediate help medical help for future stings.
Manufacturers of venom immunotherapy have stated the following conditions to be contraindicated – immunodeficiency, chronic heart and lung disease, on beta blockers and severe eczema. However, only T cell mediated immunodeficiency would be an absolute contraindication and in mild cardio-pulmonary disease the therapy related morbidity would be likely to less serious than morbidity due to a wild insect sting reaction.
Preston Scoring System for immunotherapy decision making
Mueller Grade III 2 point
Mueller Grade II 1 point
High frequency of previous stings 1 point
Future frequency of stings (occupation) 1 point
Living in remote area/travelling to remote areas/ countries 1 point
High baseline mast cell tryptase 1 point
Unable to commit for 3 year treatment -1 point
Previous VIT -1 point
Pregnancy -1 point
Immunodeficiency including active cancer treatment -1 point
Any score greater than 4 consider VIT
Venom immunotherapy regime
Follow ALK-Abello Pharmalgen regime
Modified Rush immunotherapy should be considered for those who needs rapid induction of tolerance. E.g. occupational exposure, travel to an area, etc.
Venom immunotherapy should be carried out under condition which applies to other specific immunotherapy
Should only be carried out in a hospital environment with intensive therapy facilities.
The day case unit where the treatment is offered should have resuscitation facilities.
Pre-medication with modern antihistamine is recommended. Enquiry about general health and previous injection reactions should be checked before every injection. Peak flow measurement must be carried out before and an hour after injection.
Local management plan for immediate and late reactions should be available for the doctor/nurse administering injection.
Duration of immunotherapy is usually 3 years and 3 months. In patients who have high levels of baseline mast cell tryptase, longer and even lifelong treatment may be required.
Patients who have completed the course of venom immunotharpy (usually 3 years and 3 months) must be continued to be offered emergency treatment pack (antihistamines, self-injectable Adrenaline) and followed up at least every 12 months to monitor future venom reactions.
SYSTEMIC REACTIONS (CHILDREN)
Systemic reaction to hymenoptera venom is less common in children and atopic children are not at a higher risk for venom allergy.
Some children who have manifested with systemic allergic reaction may outgrow their allergy in their third decade of life; hence venom immunotherapy should only be reserved for those with Mueller Grade IV with a high risk for further stings.
LARGE LOCAL REACTIONS (ADULTS)
Most individuals who receive a hymenoptera insect sting do not develop any reactions. However, some develop a large local reaction lasting up to a week. The pathophysiology of these reactions are not fully understood but a combination of toxicity of venom, secondary infection and T lymphocyte mediated hypersensitivity are thought to be responsible for these reactions. There is no scientific evidence that large local reaction would progress to systemic reaction with further stings. There is also no evidence that they do not progress to systemic reactions. Hence, allergen sensitisation is the best marker to decide on management.
Investigations for a patient with large local reaction to venom
Full blood count, renal function, total serum IgE, allergen specific IgE to bee venom & wasp venom and baseline mast cell tryptase.
Skin prick test for the suspected insect venom should be carried out with 10 mg/mL, 100 mg/mL and 300mg/mL.
Intradermal test should be carried out with 1 mg/mL of suspected insect venom.
If the identity of the suspected hymenoptera insect in not known skin prick test and intradermal tests with both bee venom and wasp venom will be required.
Management of a patient with a large local reaction to venom
Advice should be given to the patient regarding avoidance of further stings.
Advice should be given to the general practitioner to offer antibiotics if secondary infection is suspected following a future sting leading to a large local reaction.
A patient with systemic reaction and has been sensitised to venom should receive antihistamine, self-injectable Adrenaline to keep.
There is NO place for venom immunotherapy on individual who have experience large local reactions.
LARGE LOCAL REACTIONS (CHILDREN)
Investigations and treatment for children under 10 years of age who have experienced a large local reaction is generally not necessary. If the parents are anxious about future sting related anaphylaxis, it is advisable to investigate for allergen sensitisations and offer antihistamine and self-injectable Adrenaline if sensitised.