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The Role of Ecological Linkage Mechanisms in Plasmodium knowlesi Transmission and Spread

Davidson G, Chua TH, Cook A, Speldewinde P, Weinstein P

Ecohealth, 2019 12;16(4):594-610.
PMID: 30675676 DOI: 10.1007/s10393-019-01395-6

Defining the linkages between landscape change, disease ecology and human health is essential to explain and predict the emergence of Plasmodium knowlesi malaria, a zoonotic parasite residing in Southeast Asian macaques, and transmitted by species of Anopheles mosquitos. Changing patterns of land use throughout Southeast Asia, particularly deforestation, are suggested to be the primary drivers behind the recent spread of this zoonotic parasite in humans. Local ecological changes at the landscape scale appear to be increasing the risk of disease in humans by altering the dynamics of transmission between the parasite and its primary hosts. This paper will focus on the emergence of P. knowlesi in humans in Malaysian Borneo and the ecological linkage mechanisms suggested to be playing an important role.
Fulltext Defining the ecological and evolutionary drivers of Plasmodium knowlesi transmission within a multi-scale framework

Davidson G, Chua TH, Cook A, Speldewinde P, Weinstein P

Malar J, 2019 Mar 08;18(1):66.
PMID: 30849978 DOI: 10.1186/s12936-019-2693-2

Plasmodium knowlesi is a zoonotic malaria parasite normally residing in long-tailed and pig-tailed macaques (Macaca fascicularis and Macaca nemestrina, respectively) found throughout Southeast Asia. Recently, knowlesi malaria has become the predominant malaria affecting humans in Malaysian Borneo, being responsible for approximately 70% of reported cases. Largely as a result of anthropogenic land use changes in Borneo, vectors which transmit the parasite, along with macaque hosts, are both now frequently found in disturbed forest habitats, or at the forest fringes, thus having more frequent contact with humans. Having access to human hosts provides the parasite with the opportunity to further its adaption to the human immune system. The ecological drivers of the transmission and spread of P. knowlesi are operating over many different spatial (and, therefore, temporal) scales, from the molecular to the continental. Strategies to prevent and manage zoonoses, such as P. knowlesi malaria require interdisciplinary research exploring the impact of land use change and biodiversity loss on the evolving relationship between parasite, reservoir hosts, vectors, and humans over multiple spatial scales.
Forest Restoration and the Zoonotic Vector Anopheles balabacensis in Sabah, Malaysia

Davidson G, Speldewinde P, Manin BO, Cook A, Weinstein P, Chua TH

Ecohealth, 2024 Feb 27.
PMID: 38411846 DOI: 10.1007/s10393-024-01675-w

Anthropogenic changes to forest cover have been linked to an increase in zoonotic diseases. In many areas, natural forests are being replaced with monoculture plantations, such as oil palm, which reduce biodiversity and create a mosaic of landscapes with increased forest edge habitat and an altered micro-climate. These altered conditions may be facilitating the spread of the zoonotic malaria parasite Plasmodium knowlesi in Sabah, on the island of Borneo, through changes to mosquito vector habitat. We conducted a study on mosquito abundance and diversity in four different land uses comprising restored native forest, degraded native forest, an oil palm estate and a eucalyptus plantation, these land uses varying in their vegetation types and structure. The main mosquito vector, Anopheles balabacensis, has adapted its habitat preference from closed canopy rainforest to more open logged forest and plantations. The eucalyptus plantations (Eucalyptus pellita) assessed in this study contained significantly higher abundance of many mosquito species compared with the other land uses, whereas the restored dipterocarp forest had a low abundance of all mosquitos, in particular, An. balabacensis. No P. knowlesi was detected by PCR assay in any of the vectors collected during the study; however, P. inui, P. fieldi and P. vivax were detected in An. balabacensis. These findings indicate that restoring degraded natural forests with native species to closed canopy conditions reduces abundance of this zoonotic malarial mosquito vector and therefore should be incorporated into future restoration research and potentially contribute to the control strategies against simian malaria.
Current rates of purchasing of antibiotics without a prescription across sub-Saharan Africa; rationale and potential programmes to reduce inappropriate dispensing and resistance

Sono TM, Yeika E, Cook A, Kalungia A, Opanga SA, Acolatse JEE, et al.

Expert Rev Anti Infect Ther, 2023;21(10):1025-1055.
PMID: 37740561 DOI: 10.1080/14787210.2023.2259106

INTRODUCTION: Antimicrobial resistance (AMR) is a global concern. Currently, the greatest mortality due to AMR is in Africa. A key driver continues to be high levels of dispensing of antibiotics without a prescription.
AREAS COVERED: A need to document current rates of dispensing, their rationale and potential ways forward including antimicrobial stewardship programmes (ASPs). A narrative review was undertaken. The highest rates of antibiotic purchasing were in Eritrea (up to 89.2% of antibiotics dispensed), Ethiopia (up to 87.9%), Nigeria (up to 86.5%), Tanzania (up to 92.3%) and Zambia (up to 100% of pharmacies dispensing antibiotics without a prescription). However, considerable variation was seen with no dispensing in a minority of countries and situations. Key drivers of self-purchasing included high co-payment levels for physician consultations and antibiotic costs, travel costs, convenience of pharmacies, patient requests, limited knowledge of antibiotics and AMR and weak enforcement. ASPs have been introduced in some African countries along with quality targets to reduce inappropriate dispensing, centering on educating pharmacists and patients.
EXPERT OPINION: ASP activities need accelerating among community pharmacies alongside quality targets, with greater monitoring of pharmacists' activities to reduce inappropriate dispensing. Such activities, alongside educating patients and healthcare professionals, should enhance appropriate dispensing of antibiotics and reduce AMR.