From quantification to control
: a population-based study to measure the secondary impact of ivermectin-based mass drug administration aimed to control onchocerciasis on the prevalence of scabies in northern Ethiopia

  • Robel Belachew

Student thesis: Doctoral Thesis


Scabies is a parasitic skin infestation endemic to both high-income and low-income settings but with a varying epidemiologic presentation. Despite its high burden and global distribution, it had been neglected as a public health problem and there is limited data about the nature of the disease in global health settings. In Ethiopia, a large-scale scabies outbreak was reported in 2015 mainly involving the northern part of the country. However, lack of data on the disease epidemiology and the effectiveness of a variety of control strategies was a barrier to the required swift response. This study aimed to determine scabies epidemiology and measure the secondary impact of ivermectin onchocerciasis Mass Drug Administration (MDA) on the prevalence of scabies in outbreak affected Ayu Guagusa district, Amhara regional state, northern Ethiopia. The study also aimed to synthesize the published knowledge of scabies in Ethiopia and measure the effect of the infestation on life quality of patients.

A systematic review was conducted targeting articles published on scabies in Ethiopia in the past 25 years. This provided the basis for the main study by identifying the local evidence gap in community-based scabies control interventions. A quasi-experimental approach was employed to measure the impact of ivermectin onchocerciasis MDA on the prevalence of scabies by conducting three successive surveys (baseline, 6-month, and 12-months) where the MDA was between the first two rounds. Randomly selected households (n=381) and the respective consenting members participated in the study. The impact of the MDA on scabies was determined by estimating the prevalence before and after the MDA. Multilevel logistic regression models were fitted to identify the determinants of scabies infestation in the study community. The effect of scabies on life quality of patients was measured using the Cardiff Dermatologic Life Quality Index (DLQI).

In the systematic review, high scabies prevalence and skewed geographic distribution of publications was identified. Scabies prevalence across the three surveys was high: baseline 13.4% (11.7%-15.2%), 6-month 11.7% (10.1%-13.2%), and 12-months 22.1% (20.1%-24.1%). Living in households of size > 5 increased the odds of scabies infestation and female sex had lower odds. Scabies had moderate impact on life quality of patients and symptoms and feelings was the most affected life quality domain.

Onchocerciasis MDA did not impact scabies prevalence, at least in the study period. Increasing the number of doses in each round of MDA, distributing topical scabicides to people ineligible to take ivermectin can help optimize onchocerciasis MDA for the control of scabies. Demographic characteristics and host density were important determinants of scabies. Though these characteristics are not amenable for change, modifying circumstances associated with them may help reduce odds of the infestation.
Date of AwardFeb 2023
Original languageEnglish
Awarding Institution
  • University of Brighton
SupervisorJackie A. Cassell (Supervisor), Gail Davey (Supervisor), Jo Middleton (Supervisor), Abebaw Fekadu (Supervisor) & Dr Abraham Tesfaye (Supervisor)

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