The short answer is Asia (Thailand, Vietnam, China) and Africa (Tanzania, and in the past
Malawi).
There are a series of companies that supply nets who are all WHOPES Phase II approved (World Health Organisation Pesticide Evaluation Scheme). This
is the body that evaluates nets and designates individual products safe for use
after appropriate lab and field testing. They publish all testing results.
Vestergaard, who produce PermaNet nets, and Sumitomo Vector Control, who produce
Olyset nets, are two of the bigger manufacturers and they are the two organisations
from whom we have bought the majority of our nets so far. Vestergaard are a Danish company and Sumitomo a Japanese company and they both have offices in a number of locations around the world.
Purchasing decisions are based largely, but not entirely, on price.
Nets are effectively a textile so there are economies of scale in manufacturing.
Global demand means there are a relatively small number of facilities needed to
produce the number of nets required. Scale economies mean it would not be cost effective
to locate a manufacturing facility in all or most countries that have a high net
need. However, Africa-based location could reduce logistics costs, improve the speed of supply (shipping currently takes two months or so) and benefit the local economy.
Vestergaard and Sumitomo supply the majority of their nets from Asia, typically
Vietnam, Thailand and China. There are manufacturing facilities other than in Asia.
For example, there is a facility in Tanzania that is a joint venture between Sumitomo
and a local company. There are/were plans for other facilities in Nigeria and Ethiopia
but we are not current on the situation there.
The majority of the nets we have bought to date have been from Asia but we have
bought significant quantities from the facility in Tanzania and from a supplier
in Malawi. When we required 130,000 nets to protect 130,000 boarding school children
in Tanzania we purchased from the Tanzanian supplier. A further 150,000, 235,000 and 322,500 nets have been supplied from Africa.
Our first obligation is to protect as many people as we can with the funds we have
available. If the lowest price is therefore from Asian supply, that is where we
are likely to buy. However, we are conscious of assisting local economies where we can, so
if the difference between two quotes is marginal, an order can end up with a local
supplier.
See also a
related post from 2011