Biology Reference
In-Depth Information
Insecticide residual spraying (IRS) of house walls was the basis of the
GMEP and noted many successes in areas of seasonal transmission. Once
adopted, IRS became a grand logistics problem, but not a conceptual one.
If one could just deliver adequate amounts of insecticide (DDT in the case
of GMEP) to all the houses in a defined area, malaria transmission would go
down to levels that the parasite could no longer reproduce itself (R
0
< 1).
Malaria elimination then became another organizational problem of how to
maintain an IRS program long enough for the malaria to go away. Given
the usually stated limit on malaria relapses of 3 years post infection, 3-5-year
intensive programs offered certainly malaria control and possibly elimination.
It is very difficult to outwait the parasite especially vivax as it can reappear
years later from hypnozoites to restart transmission. Practical problems dogged
all malaria control programs, but in both China and India, countries with
immense human and parasite (both falciparum and vivax) populations, a very
high degree of control was achieved with IRS, resulting in the prevention of
many deaths and associated disease (
Cui et al., 2011
;
Kidson and Indaratna,
1998
). The perception of failure only appeared later after malaria resurged
once control measures were abandoned prior to achieving elimination.
Turning control into elimination depends on both achieving a high
degree of control and then maintaining it for years with a good surveillance
system to detect the few remaining cases. Falciparum was removed before
vivax, thus one of the first positive signs of malaria control was elimination
of malaria mortality. Removal of malaria from a population had multiple
positive health effects indicating the parasite's role in combination with many
other non-malarial infections. Once mortality and much malaria morbidity
were removed, however, the motivation to continue the program markedly
decreased. This lack of interest may have been aided by discounting vivax
malaria as being of a less serious nature than falciparum malaria, a misunder-
standing of the morbidity caused by vivax as described in chapter 3 of volume
80. As resources migrated to other more pressing health problems, malaria
control programs gradually lost community support and then disintegrated.
Health concerns about the long-acting insecticide DDT, which was the basis
of the GMEP, removed critical community acceptance and left the program
without any fall-back options. Over a period of years, sometimes with inter-
mittent epidemics, malaria returned to previous endemic levels.
2.2. Insecticide Impregnated Bed Nets
The evolution of an alternative to IRS took time, but eventually giving the
householders control over the insecticide by placing it into a portable bed
