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We've Been Wrong All Along

A Net's Tale - Part Two

Kakumbi Rural Health Clinic is in Mfuwe, right on the cusp of South Luangwa National Park.

It is a very basic front line clinic, run entirely by local nurses, with visiting doctors from UK, USA and Australia doing 3-6 months stints.

[If you are a doctor and are interested [DO IT! GO ON!] - contact kapani@normancarrsafaris.com for more details on this scheme. I will also happily intro you to my friends out there and you will get to see lions and everything.] 

The clinic has very limited supplies and services an estimated population of 20,000 people. 

That's a lot. 

And it's growing relatively rapidly, due to the increased employment in the area, and corresponding semblance of financial security, that the tourist economy provides.

Our friends at the Buschcamp Company know the place well and took us there to distribute the nets. 

Our friends at Malarianomore provided the nets - and we have now connected them to the local community there, via the Bushcamp Company

[But - to clarify once again, this is not the usual way they distribute nets! Just us trying to help a little bit.] 

We arrived the day of a maternity clinic - there were people waiting for hours to see the nurse or maternity nurse with their babies.

The nurse presented us with one of the many impossible decisions she faces every day: with only 40 nets in a bail, and many more mothers than that - who do you distribute them to? 

How do you decide?

She also, kindly, thankfully, mercifully, took this burden away from us, sorting them by age, and giving them out to the youngest and most vulnerable. 

And there our net's tale ended, but the tale of the nets continues.

COMPLEX SYSTEMS AND CONSEQUENCES

It was important to us that we get the nets to people alongside the appropriate education about how to use them prophylactically and how to keep them maintained. 

The nets don't just stop you being bitten - they kill mosquitoes. 

Female anopheles mosquitos [for it is indeed the only the females that bite] fly around at night looking for food.

They hit the net.

They die. 

The nets need to be retreated every 6 months or so because the pyrethrum wears off.

When they are treated, the nets cause positive externalities.

The more dead mosquitoes in the area, the less biting, the less transmission and infection.

But when the poison wears off, this no longer happens. 

That's why it's not just nets, but treated nets that are the key. 

Treated nets

Nothing about epidemiology is simple I'm afraid -  it's a massively complex system problem.

I'm incredibly fortunate then that my brother, Dr. Laith Yakob, is an epidemiologist and has done extensive malaria research.

This is what his work looks like.

It's the results of a mathematical model that looks at how different vector management methods - insect treated nets [ITNs] and destroying larval habitats - interact. 

It shows that it is better to focus on wider net distribution, instead of diverting resources into doing both, because that works better, while the nets are fatal to mosquitos [when they aren't, this changes].

ITN model laith

Figure 4. ITNs and habitat source reduction in the integrated control of malaria.

The colors correspond to the basic reproductive number of malaria (R0) as highlighted in the key (the parameter space for local malaria elimination, R0<1, is black). The values in white font at the top-right corner of the plots indicate the killing efficacy of the ITNs: 0.5 (a, b and c); 0.25 (d, e and f); and 0.0 (g, h and i). Three human densities are used: ‘Low’ (100 per sq Km) (a, d and g), ‘Medium’ (333 per sq Km) (b, e and h), and ‘High’ (1,000 per sq Km) (c, f and i). Other parameters used in the simulation are mosquito search ability 1,000 sq m per day, and larval habitat density 1,000 per sq Km.

doi:10.1371/journal.pone.0006921.g004

Laith's work also shows how DDT use in Africa interacts with ITNs, which may be antagonistically rather than synergistically, as is currently believed: 

“When used in the same household as bednets, repellent DDT will reduce mosquitoes contacting the insecticides with which bednets are treated.” 

Current strategy of combining DDT with bednets may actually detract from the community-wide benefits experienced with bednets alone. 

“Treated bednets are highly effective at killing malaria-carrying mosquitoes," Dr Yakob said. 

“Spraying DDT in the same residence will divert the mosquito away from the treated bednets, onto unprotected homes." 

You always have to think about how what you do interacts with, well, EVERYTHING ELSE. 

Everything is part of a system of interoperating systems.

And we think the newly emerging mediascape is difficult to navigate. 

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