2.00 - 2.05 Welcome/Chair's introduction
2.05 - 2.30 Dr Jennifer Lord (Liverpool School of Tropical Medicine) – Identifying sources of transmission for zoonotic mosquito-borne viruses
2.30 - 2.55 Dr Jack Pilgrim (University of Liverpool) – Usutu virus: a new vector-borne threat to the UK?
2.55 - 3.05 Refreshment break
3.05 - 3.30 Dr Olatunji Johnson (University of Manchester) – Geostatistical methods for efficient safety assessment of Ivermectin in Loa loa endemic areas
3.30 - 3.55 Dr Claudio Fronterre (Lancaster University) – Joint geostatistical modelling of lymphatic filariasis antigenaemia and microfilariae prevalence
3.55 - 4.00 Close
Dr Jennifer Lord – ‘Identifying sources of transmission for zoonotic mosquito-borne viruses’
Many mosquito-borne pathogens that cause disease in humans, like dengue, are transmitted between humans. However, there are at least 12 mosquito-borne viruses that are transmitted between other animals, for which humans are incidentally infected. These viruses are difficult to control; human vaccination alone cannot eliminate them. Furthermore, because zoonotic mosquito-borne viruses are usually transmitted by multiple host and vector species, they can be present across a range of ecological contexts. In turn, ecological context influences transmission dynamics and risk to humans. The ability to target control within ecological contexts that present sources of onward transmission should increase impact. I will discuss three broad themes of importance for identifying sources of transmission for this group of viruses: heterogeneity, scale, and noise. With respect to these themes, I will highlight current research gaps in the modelling literature and give specific examples from two new projects which aim to address these gaps by integrating empirical studies and modelling for Japanese encephalitis and Rift Valley fever.
Dr Jack Pilgrim – ‘Usutu virus: a new vector-borne threat to the UK?’
Usutu virus infects and causes large scale mortality in certain species of wild bird (such as blackbird and crows); but in recent years it has been recognised as zoonotic, infecting people, and causing fever and, in some cases, neuro-invasive disease such as encephalitis and meningoencephalitis. Usutu virus is spread by mosquitoes and is emerging throughout Europe. During the warm summer of 2020, zoonotic mosquito-borne Usutu virus was detected in two species of wild birds in Greater London. Furthermore, Usutu virus was detected over a long time period and in the non-migrating house sparrow, strongly suggesting that the virus has established in the UK and local British mosquitoes are transmitting it.
The primary mosquito vector of Usutu virus in Europe, the Northern House mosquito, is present in the UK where it feeds predominantly on birds. Recent studies have shown that a laboratory colony of this species is competent to transmit the virus at warm temperatures. Therefore, our native mosquitoes may therefore be capable of transmitting it. In addition, other species of mosquito present in the UK feed on both birds and humans and may therefore be capable of spreading the virus from the bird reservoir to humans. The ability of these species to transmit Usutu virus in the wild is not known.
The overall aim of this project is to assess the risk to the UK of local and invasive mosquitoes transmitting Usutu virus to birds and humans, at realistic UK temperatures. Using these results, I will mathematically model the suitability of the UK climate for the spread of Usutu virus, in conjunction with data on the geographical range of local mosquitoes and reservoir bird species. This will yield risk maps, showing where and when Usutu virus is capable of being transmitted in the UK.
Dr Olatunji Johnson – ‘Geostatistical methods for efficient safety assessment of Ivermectin in Loa loa endemic areas.’
The elimination of onchocerciasis through community-based mass drug administration (MDA) of ivermectin (Mectizan) is hampered by co-endemicity of
Loa loa, as individuals who are highly co-infected with
Loa loa parasites can suffer serious and occasionally fatal neurological reactions from the drug. Testing all individuals participating in MDA is impractical due to cost and limited availability of diagnostic tools. Therefore, there is a need for a way to establish whether an area is safe for MDA using the prevalence of loiasis derived from multiple diagnostic tools. Existing statistical methods only focus on using data from one diagnostic tool and ignore the potential information that could be derived from other datasets. In this talk, I will discuss how we address this issue by developing a joint geostatistical model that combines data from multiple
Loa loa diagnostic tools. We applied this model to
Loa loa data from Gabon and propose a two-stage strategy to identify areas that are safe for MDA. Lastly, I will discuss how this work contributes to the global effort towards the elimination of onchocerciasis as a public health problem by potentially reducing the time and cost required to establish whether an area is safe for MDA.
Dr Claudio Fronterre – ‘Joint geostatistical modelling of lymphatic filariasis antigenaemia and microfilariae prevalence’
Lymphatic filariasis (LF) is a mosquito-borne neglected tropical disease targeted for global elimination. In recent years, the mapping of LF has been greatly facilitated by the use of simple and rapid detection tests based on the immuno-chromatographic test (ICT), which avoids the need to collect blood at night and the time-consuming preparation and examination of blood slides. Even if the scientific output of interest is the prevalence of microfilaraemia (MF), the number of mapping surveys that measure MF is low, and it is decreasing due to the diffusion and cost-effectiveness of ICT tests. We develop a geostatistical model that exploits the abundance of ICT prevalence surveys and the relationship between ICT and MF prevalence to predict microfilaraemia prevalence at unobserved locations. We use LF data from West-Africa to show how this modelling framework can be used to produce relevant output for control and elimination programmes.