BO T TOM
DIFFERNT T YPES OF PAPER
THIS SQUARE TES TS FOR
AFLATOXIN, A COMPOUND
PRODUCED BY FUNGI THAT
CONTAMINATE GRAINS AND MILK.
THESE ARE HUMAN LIVER-FUNC TION TES TS DESIGNED
WITH THE SAME BASIC PAPER
AND WAX STRUCTURE OF THE
AGRICULTURAL TES TS THAT
DFA IS DEVELOPING NOW.
Paper diagnostic tests: Coming
soon to Kenyan dairy farms
TESTS FOR MILK ON KEN YAN DAIRY FARMS MAY
SOON BE ULTRA CHEAP, printed onto paper sheets
and delivered to farmers and milk processing plants.
Diagnostics for All (DFA), a US non-profit biotech
firm, is designing tests for milk spoilage and estrus
in cows (to detect when the cow is ovulating).
The tiny coin-sized microfluidic chips are made
mostly from thin strips of paper printed with wax.
They do not require electricity or the storage of liquid
samples. And they are simple enough for farmers to
read, either by sight with a mobile device app.
These tests, and others coming online behind
them, could streamline the dairy industry in Kenya
and other developing regions. They may also boost
profits on family-owned farms.
“I think it will have great impact,” Patrick Beattie,
Director of Operations at DFA, told E4C. “What it's
doing is enabling farmers and veterinary workers
to better manage their herds, and in some cases to
improve their quality and access better markets that
they wouldn't be able to access otherwise. All of that
goes to a bottom line of improved farmer incomes,”
WICKING WI TH PAPER AND WAX
The tests operate under capillary action, the same
principle that allows plants to draw water from their
roots up to their leaves, and the way a paper towel
soaks up water when its edge is dipped in a glass.
A drop of milk or a blood sample from a cow wicks
through the paper along channels bounded by waxen
barriers. It collects in wells that contain a chemical
reactant. If the milk contains a threshold level of
certain bacteria, a spot on the test will change color
to indicate that the milk might be spoiling.
The estrus test works in the same way. The
farmer pricks a cow's ear to draw a blood sample
and applies it to the paper where a chemical reaction
reveals the absence of the hormone progesterone.
( When cows ovulate their progesterone levels drop.)
WH Y SPOILAGE AND ES TRUS?
Small-plot dairy farmers in Kenya gather their milk
and deliver it to central milk chilling plants. The plants
pool the milk from dozens or hundreds of farms so
that even a few gallons of spoiled batches could
contaminate many others. Milk spoilage tests already
exist, but DFA's paper strip, when the design is com-
plete, is likely to be less expensive and more accurate.
Estrus testing is important, also, because of how
domesticated cattle reproduce. Most cows are artificially inseminated. The practice is widespread and
practical because bull semen freezes and ships well.
The best bulls are in demand for breeding worldwide
and it is easier to ship their semen than to ship the
bull. It is also cheaper for farmers to buy semen
rather than raise bulls for breeding.
DFA's estrus test can take guesswork out of the
insemination process and tell the farmer when the
cow is ready. A cheap and widely available test can
save the farmers' time and money.
PAPER MICROFLUIDICS FOR DEVELOPING COUN TRIES
DFA has a grant from the Gates Foundation for $3
million over two years to develop the agricultural
diagnostic tests. The organization is also developing tests for liver damage, which is common in HIV/
AIDS patients, and for malaria, dengue fever and
preeclampsia, a complication of pregnancy.
NEX T STEPS
When the tests are ready for distribution, DFA plans
to seek partners to manufacture and sell them. The
idea is that selling them, rather than giving them
away, could help the tests catch on. DFA's field
research has shown that farmers can make more
money by using the tests, so they have incentive to
buy them. And they will be cheap to manufacture, so
private companies could have incentive to make them.
“The tests are enabling
farmers to better manage
their herds, and in some
cases to improve their
quality and gain access
to better markets."