By Professor Sarah Cleaveland
Arusha street scene. Photo: N Feans/Flickr

Arusha street scene. Photo: N. Feans/Flickr

I have just arrived in Arusha, in northern Tanzania. All over town, as across the whole of Tanzania, people are gearing up for elections that will be held at the weekend. Massive posters of the two presidential candidates tower over roundabouts and streets, flags on cars and motorbikes proclaim rival allegiances, and the political exhortations conveyed from loudhailers mingle with chants and cheers of election rallies convened in every corner of town.

So far the atmosphere is calm, but the election is likely to be close and, below the surface, passions are running high. We are all hoping for an untarnished election process with a clear and uncontroversial result that will allow the country to move forward constructively after the distractions of the past months.

El Niño predictions

It is still very dry in Arusha. Unprecedented El Niño rains are forecast for East Africa this year – off the chart it seems – but today there is still no inkling of the deluge that is due to come.

Mosquito trappers: From left: James Nyarobi (University of Glasgow/NM-AIST), Amos Mlwale (IFAKARA Health Institute), Rigobert Tarimo (NM-AIST), Felician Meza (IFAKARA Health Institute), Will de Glanville (University of Glasgow).

Mosquito trappers. From left: James Nyarobi (University of Glasgow/NM-AIST), Amos Mlwale (IFAKARA Health Institute), Rigobert Tarimo (NM-AIST), Felician Meza (IFAKARA Health Institute), Will de Glanville (University of Glasgow).

We are preparing, of course, for the epidemics that come with the rains, particularly Rift Valley fever (RVF). This is a viral disease that is sometimes described as one of the haemorrhagic fevers. But in reality the disease more commonly causes a flu-like fever, with death from haemorrhagic symptoms a tragic, but rather rare outcome. The RVF virus is transmitted from mosquitoes, and epidemics are typically associated with torrential El Niño rains that trigger large mosquito swarms that allow the virus to multiply and spread.

RVF can also cause devastating problems for livestock, with disease, abortion and death all reported during outbreaks. People can easily acquire RVF when handling infected animals or meat, and so are advised to avoid slaughter or consumption of livestock products during outbreaks, which invariably results in food shortages.

For the many rural households in Tanzania that are heavily reliant on livestock, food is already in short supply as a result of the prolonged dry season. It is a terribly irony that the onset of the rains may exacerbate these problems.

Mosquito sampling

In preparation for setting up a research platform for RVF, Will de Glanville (field epidemiologist), Tito Kibona (veterinary coordinator) and James Nyarobi (PhD student) have been out in the field training in techniques of mosquito capture and sampling with researchers from the Ifakara Health Institute. This team has extensive experience of mosquito ecology, particularly in relation to malarial mosquitoes. For Livestock, Livelihood and Health’s project looking at the Social, Economic and Environmental Drivers of Zoonoses in Tanzania, we are focusing on different species of mosquito, Aedes and Culex, which are likely to be important in the transmission of RVF.

We know very little about these mosquitoes in the wildlife-rich ecosystems of northern Tanzania, but James Nyarobi’s MSc research has generated some intriguing results that demonstrate RVF virus infection in Aedes and Culex mosquitoes in the period between outbreaks, which hints at unexpected patterns of virus circulation.

Over the coming weeks and months, we hope to set up sampling points across the ecosystem to monitor patterns of RVF infection in mosquitoes – spanning the RVF epidemic if this does come as predicted – and looking at how infection patterns change in relation to rainfall, mosquito abundance and mammalian host distributions.

After a busy year that has focused on setting up the infrastructural, administrative and institutional platforms for our research, it is exciting to be getting out into the field for data collection. It is my hope that, as we set up our traps out in the bush, far from the hue and cry of the election, the only storm clouds we see will be those that signal the coming rains.

Professor Sarah Cleaveland is co-Principal Investigator of the disease drivers project of LLH.

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