• Home
  • »
  • Themes
  • »
  • Integrated Control Strategy 1: Macro & Vector (1)

Integrating Complimentary Strategies

The integrating complimentary strategies theme recognises that the scale-up of MDA for NTDs alone is not enough to achieve the London Declaration 2020 targets. This theme will examine how additional strategies such as vector control, the provision of sanitation and hygiene, new tools, capacity building and better health awareness might accelerate progress toward these goals.

Onchocerciasis

Onchocerciasis is a vector-borne disease caused by the parasite Onchocerca volvulus. It manifests as troublesome itching, skin rash, visual impairment and irreversible blindness. It is common and widespread in Cameroon. The current strategy for control is using mass drug administration with ivermectin, a drug that kills the immature form of the parasite found in the skin. The WHO recommends that annual mass drug administration for 15-17 years with high population coverage should be sufficient to interrupt transmission.

Mass drug administration has been conducted in the South West Province of Cameroon for twelve years in a strategy known as Community-Directed Treatment with ivermectin (CDTi), yet higher than expected prevalence and intensity of onchocerciasis persists. The persistence of onchocerciasis highlights that control of this disease in Cameroon is complicated by a number of factors, namely geographical overlap with Loa loa, hampering community directed treatment with ivermectin (CDTi) due to adverse effects; poor perception and uptake of CDTi due to fear of adverse effects, even in areas free from Loa loa; and high prevalence of skin microfilariae even after more than ten years of drug treatment. Therefore an urgent need exists to validate and implement alternative strategies for the control and elimination of onchocerciasis, as well as to fully understand potential reasons for sub-optimal success of the CDTi strategy so that these may be avoided in the future.

The central aim for this section of research is to implement a test-and-treat strategy for onchocerciasis control using doxycycline, a potential alternative to ivermectin. Doxycycline differs from ivermectin as it targets symbiotic bacteria, Wolbachia, living within the worms. Depleting the symbionts sterilises adult worms residing in human tissues, preventing the production of skin infecting micofilariae, and significantly reduces adult lifespan. Offering an alternative treatment to ivermectin will help counter the poor community perception of the current strategy. Biological monitoring will be undertaken to determine the impact of this alternative strategy on the prevalence of onchocerciasis microfilariae in the skin, using traditional parasitological techniques. Alongside these traditional techniques, which have some limitations of sensitivity and acceptability, several innovative field-friendly alternative diagnostic techniques will be implemented in tandem. These alternative diagnostic strategies will be assessed against the current parasitological techniques to determine their sensitivity, specificity and overall applicability to the low resource setting.

Social science approaches will be used to help identify risk factors for the poor efficacy of the current CDTi strategy, alongside the capture of societal and health economic data to assess the acceptability and feasibility of the test and treat strategy. 

Lymphatic filariasis

Lymphatic filariasis is a mosquito-borne infection caused by the parasitic worm Wuchereria bancrofti. It causes significant illness, disability and disfigurement to the affected individuals, and is endemic in Ghana. Currently, the national Lymphatic filariasis Elimination Programme is distributing mass drug administration (MDA)using a combination of ivermectin and albendazole to interrupt the transmission of the disease. The World Health Organization recommends distribution of drugs annually for 5-7 years, which is the estimated life span of adult worms.

The Lymphatic filariasis elimination programme in Ghana has achieved tremendous success through the MDA campaign and many regions have met the criteria to scale down distribution. In these regions it will be crucial to sustain the gains made by the programme and prevent resurgence. However, although MDA for Lymphatic filariasis has been conducted in an increasing number of communities for over 10 years in Ghana, the infection prevalence is highly heterogeneous and hotspots (areas with ongoing parasite transmission) still persist in some parts of the country. It is likely that these heterogeneities are driven by differences in access to drugs, drug uptake, vector characteristics such as biting density, vector competence, host-seeking behaviours and possibly host and vector genetic factors. In order to achieve effective elimination of Lymphatic filariasis, it is pivotal to address the underlying social, epidemiological, parasitological and entomological causes allowing the disease to persist despite long periods of intervention.  There is evidence that integration of vector control and MDA can accelerate elimination, but  long lasting insecticide treated nets  (LLINs) are not distributed along with MDA and there is no coordination between National Malaria Control Programme and Lymphatic filariasis elimination programmes to ensure LLIN coverage can meet Lymphatic filariasis elimination targets. Although vector control is a part of many national malaria control programmes, coverage and compliance are sub-optimal.

The major aim of the Lymphatic filariasis research in Ghana is to provide evidence to support rapid and sustainable scale up of complementary intervention strategies to eliminate Lymphatic filariasis in the country. This will be achieved through evaluating the social, entomological and epidemiological characteristics of hotspot communities to identify the causes of persistent transmission, alongside evaluating the impacts of an integrated MDA and vector control programme on service delivery, community participation and Lymphatic filariasis transmission.

The collected information will be then used to identify opportunities for better planning and co-implementation of the interventions at the district and community level. We are also working to develop tools and methods to inform scale-down of interventions, including the application of disease transmission models to predict the impacts of interventions on Lymphatic filariasis to help setting locally relevant targets for elimination, and the evaluation and optimisation of available and emerging tools for the sensitive detection of the parasite in the mosquito vectors for post-MDA surveillance.