A feasibility study to assess Imbrasia belina (mopane worm) sensitisation and related respiratory health outcomes in a rural community in Gwanda district, Zimbabwe

Abstract

Background Allergic diseases are considered to be some of the fastest growing chronic conditions in Africa. Of concern is the paucity of knowledge about the local environment and its role in allergic disease development. In response to this, we explored whether Imbrasia belina, a popular indigenous edible insect commonly known as mopane worm, is a potential allergen of clinical and public health significance in Zimbabwe. This study was intended to assess the plausibility and feasibility of this hypothesis with a view to evaluate the insect’s health impact in a larger study. Methods The study participants included male and female villagers aged 10 years and above in Gwanda district, Zimbabwe. Eligible participants who completed the household questionnaire were referred to the local clinic for skin prick tests and to measure lung function and allergic airway inflammation. Allergen sensitisation patterns were evaluated using 10 different inhalant allergen extracts including an in-house preparation of mopane worm. Lung function was measured with a Koko Legend spirometer, and fractional exhaled nitric oxide levels (FeNO) (NIOX VERO) were measured in participants with at least one abnormal spirometric parameter. Data was analysed using Stata version 13 software. Results Of the 46 eligible participants that completed the household questionnaire, 17 went to the clinic giving a response rate of 37%. The majority who completed the questionnaire were adults (91%) and the children (9%) were all female. The prevalence of sensitisation to Imbrasia belina was 50%, and the prevalence ranged from 22 to 72% for the other allergens including cockroach, mosquito and house dust mites. The data collection tools were safe and well tolerated by participants with no adverse events reported. Self-reported respiratory symptoms, abnormal lung function and elevated FeNO were recorded amongst participants sensitised to mopane worm. Conclusion Pre-defined feasibility criteria were met with the exception of a lower than expected response rate for clinic data collection in this pilot study. For the main study, modifying the sampling strategy and applying more consistent community engagement will improve the response rates.

Sensitisation to Imbrasia belina (mopane worm) and other local allergens in rural Gwanda district of Zimbabwe

“…This cross sectional study was conducted from October 2019 to March 2020 as part of the Gwanda Asthma and Respiratory Allergy Study (GARAS) that was designed to investigate the presence of asthma and respiratory allergy in Gwanda rural community and identify the associated demographic, environmental and socio-cultural factors. All procedures and tools were pre-tested in a feasibility study carried out prior to the main study [ 39 ]. The study was approved by the Medical Research Council of Zimbabwe (Reference number MRCZ/A/2486) and the University of KwaZulu-Natal’s Biomedical Research Ethics Committee (BREC) (Reference number BE 327/19).…”

“…A non-probability, volunteer sampling strategy was used to recruit eligible participants with the assistance of the village leaders from each of the eight villages in Garanyemba. This approach was informed by a low response rate in the feasibility study [ 39 ]. Based on the assumption of a mopane worm sensitization estimate of 50%, a 5% margin of error at 95% confidence interval and an additional 20% to compensate for anticipated non-response, a sample size of 462 participants was calculated [ 40 ].…”

“…All data was collected in a centrally located clinic in Garanyemba [ 39 ]. Informed consent and, in cases of children, parental consent and the child’s assent were obtained from participants presenting at the clinic.…”

“…This panel of allergens was found to be locally relevant based on a previous study in Zimbabwe [ 9 ]. Mopane worm (Imbrasia belina) and mopane tree leaf extracts were prepared in-house using previously detailed procedures [ 39 ]. An extract of mopane tree leaves was included in the panel because mopane worms feed primarily, though not exclusively, on the leaves of the mopane tree, Colophospermum mopane [ 19 ].…”

“…Skin prick testing was performed by trained staff at the clinic as previously described [ 39 ]. Skin-prick test wheal diameters exceeding 3 mm or greater than the saline control was considered positive [ 42 ].…”