Effectiveness of impregnated mosquito bed netting in preventing malaria in Western Kenya

¶ … Impregnated Mosquito Bed Netting in Preventing Malaria in Western Kenya

Malaria in areas such as Western Kenya has become am increasingly serious disease, which is responsible for more deaths than HIV / AIDS. The advent and introduction of impregnated mosquito bed netting in areas of Africa has raised hopes of a new method of combating malaria. Numerous studies attest to the fact that impregnated nets significantly reduce the transmission and infection of malaria in the region; especially among very young children.

However, account must also be taken of the various other concomitant factors that impact on the spread of malaria, including cultural and economic issues. Studies also caution against the expectation that impregnated bed nets are a final solution or panacea to malaria in Kenya. While impregnated bed nets have been shown to be extremely effective in reducing the incidence of malaria, yet the solution to the problem lies in an integrative view, which includes impregnated bed nets as well as a myriad of other related factors.

Introduction

While HIV / AIDS is commonly considered to the most devastating disease in Africa, numerous studies point out that the real killer is malaria. "...malaria is still the leading killer in Africa" (Patel, 1997)

This is particularly the case in Kenya. "In Kenya, malaria remains one of the biggest health problems and 75 per cent of the children born in the malaria-prone areas of the Rift Valley Province get infected with the disease. "(Patel, 1997)

Malaria in this region has both medical as well as social ramifications. This is related to poor urban conditions and to the movement of the population from the rural to the urban areas. "As the urban population continues to swell, poor sanitation, poor sewage facilities and stagnant water are encouraging mosquito breeding." (Patel, 1997)

Another factor that is important in understanding the implications of the impact of malaria on Kenyan society is finance and economics. This relates to the issue of affordable personal protection against malaria and the economic ability to combat and eradicate the causes of malaria.

The introduction of impregnated mosquito bed netting in preventing malaria in Western Kenya has therefore become an important aspect of fighting malaria in this region. In the first instance it has been found to be a more affordable as well as a significant way of dealing with a disease that has devastated this part of Africa. This paper will provide an overview of the various factors related to the fight against malaria in the region and will attempt, through the current literature, to ascertain the effectiveness of impregnated mosquito bed netting in the fight against malaria in the area.

Brief overview

Malaria is a highly infectious disease that is transmitted by mosquitoes. It is estimated that worldwide, about 300 million to 500 million people get malaria each year. (Garner, 2000, p. 54) Of the malaria transmitting mosquitoes the Plasmodium falciparum strain is the cause of most fatalities. (Garner, 2000, p. 54) One of the central reasons why malaria kills so many African children is "...because they lack immunity." (Garner, 2000, p. 54)

Ironically, malaria was almost completely eradicated in the developed world more than half a century ago. (Shell, 1997) While the spread of this disease was suppressed in the less developed regions of the world in the 50's and 60's, it has "...returned in full force to North Africa, India, Southeast Asia, China, South America, and the Caribbean." (Shell, 1997)

The literature estimates that the "...Worldwide incidence of the disease has quadrupled in the past five years, and resistance to available drugs for prevention and treatment is growing rapidly." (Shell, 1997) It is a startling fact that more than 40% of the world's population lives in areas where the disease is endemic.

In terms of the present study it is a significant and alarming fact that in Kenya, physicians report that it is estimated that one in twenty children are extremely anemic. This is a result of the malaria parasites in the blood. (Shell, 1997)

It is also important to consider the overall social and healthcare situation of the people in this region, as this obviously impacts on the issue of the fight against malaria.

In terms of the political and social history of this region, the post - colonial era has seen a backlog in healthcare developments. This is emphasized by studies which indicate that the advent of HIV / AIDS and other disease like malaria have had a profound and detrimental effect on the situation in Kenya and surrounding countries.

As Kenya... struggles with "structural adjustment," dictated by the world's financial and loan markets, the International Monetary Fund and the World Bank, and with consequent reductions in contributions from the public sector for health care, medicine as a profession is reeling from a challenge of a different magnitude." (Good, Mwaikambo, Amayo & Machoki, 1999, p. 167)

This refers to the rapid increase in HIV / AIDS cases in this region. The facts with regard to this disease are significant and must be taken into account within regard to the overall healthcare situation and the way that it impacts on the fight against malaria. "In 1998, the World Health Organization/Joint United Nations Programme on HIV / AIDS (WHO/UNAIDS) estimated that the overall HIV adult prevalence rate in Kenya was 11.6%; 1.6 million people were estimated to be infected with HIV Type I, our of a total population of approximately 30 million." (Good, Mwaikambo, Amayo & Machoki, 1999, p. 167) This factor has obviously exacerbated the situation with regard to malaria and has siphoned off medical and healthcare resources that could have been used in the fight again this disease.

Another aspect that has been mentioned and which is strongly related to an understanding go the overall picture is the lack of finances.

This is an issue that will be dealt with in greater detail with regard to the economic feasibly of impregnated bed netting.

In essence, due to a lack of money, the authorities have been prevented from providing better healthcare services. This in turn has led to "...poor environmental conditions leading to mosquito breeding. In the absence of a vaccine and affordable personal protection devices that lead to total eradication, it is important to stress the need for prevention and control." (Patel, 1997)

All of the above aspects suggest the importance and the significance of insecticide treated or impregnated bed nets. Insecticide treated or impregnated nets, known as ITNs, were developed as a new technology to combat malaria in the 1980's. It is important to realize that before this time nets were already being used by the Kenyan people to protect themselves against the mosquitoes. However, the treated or impregnated nets have only recently been found to be effective. "It was only recently appreciated that a net treated with insecticide offers much greater protection against malaria: not only does the net act as a barrier to prevent mosquitoes biting, but also the insecticide repels, inhibits, or kills any mosquitoes attracted to feed." (The Africa Malaria Report - 2003)

Therefore, the importance of impregnated nets extends beyond only the immediate protection of the individual under the net. It also repels the mosquitoes in the area and therefore provides indirect protection for others in the community.

A number of studies estimate that the importance of these impregnated nets is extremely significant in the fight against Malaria in this region. "The effect is so significant that use of ITNs is considered to be one of the most effective prevention measures for malaria." (The Africa Malaria Report - 2003)

Literature review.

There is a fairly wide range of data and studies on the aspect of impregnated mosquito bed netting in the African and Kenyan context. A concise history of the preventative measures in Kenya and in other related regions is outlined in the short but informative article by Banfield (1998) entitled, Malaria: Africa's Public Enemy No. 1.

Importantly, Banfield notes that, "The challenge of preventing or effectively treating malaria is not new. In the mid-1950s, concerted efforts were made to eradicate the disease through the use of the insecticide DDT. "(Banfield, 1998. p. 35)

However, the use of DDT was found to be dangerous and a long-term health hazard. It was "...found to enter the food chain with detrimental effects extending even to mothers' milk." (Banfield, 1998. p.35) This program came to an official end in 1969.

This informative article also outlines some of the more contemporary measures that have been introduced to combater and prevent malaria; for example, the spraying with pyrethroids which has less harmful results. (Banfield, 1998, p. 35)

However, as Banfield and many other studies point out, these measures are far from an adequate solution to the problem.

Another significant aspect that must be taken into account is the fact that there has been increasing reports in recent years of the evolution of the malaria parasite, which has become more and more resistant to the various agents and drugs previously found to be effective. As Banfleid states;

the malaria parasite, as a living organism, obeys evolution - and in the 1960s, reports of resistance to first line anti-malarial drugs came from SE Asia. The race between new drugs and new resistances has not stopped since then.... And in 1986, WHO's expert panel concluded that a magic solution could not be relied upon, and that furthermore, malaria patterns were determined by a variety of socioeconomic as well as biological, climatic and geographic factors. " (Banfield, 1998. p. 35)

The article refers as well to the impact of malaria on the people of Kenya "... where people in the Bomet district were dying at a rate of three or four a day..." (Banfield, 1998. p.35)

Another general study which includes informative data relative to the topic of this study is The Heavy Cost of Malaria and AIDS by De Giorgio (2000). This article refers to some significant economic aspects and to the way that the high rate of malaria infections is affecting the economy of Kenya, as well as other countries in the region. The cycle of increased infection and the negative financial impact is clearly illustrated in the following quotation.

Malaria is also devastating, accounting for 10% to 30% of all hospital admissions in Africa and causing 15% to 25% of all deaths of children under the age of five. The cost of prevention and treatment depletes private savings and far exceeds the financial reach of health budgets. Sick individuals produce less and earn less. Foreign investment and tourism are negatively affected. (De Giorgio, 2000, p. 23)

The above study also presents some important statistics with regard to estimated costs of the disease. "According to UNICEF, the total cost of malaria in sub-Saharan Africa exceeded $2bn in 1997. And a study by John Gallup and Jeffrey Sachs reckons that malaria wiped out $74bn from the economies of 31 African countries between 1980 and 1995." (De Giorgio, 2000, p. 23) The estimated cost to Kenya was$200 per person.

The implications of malaria also have variable effects on different sectors of the population. An article that investigates the issue of healthcare, as well as the effect of malaria on women in Kenya is Women's Health Issues in Kenya by Patel (1997).

As in other developing countries, the health status of women in Kenya is unacceptably low. Widespread mortality and morbidity among women from causes all of which have one thing in common - they are largely avoidable. Since women form slightly over 50 per cent of Kenya's total population, of almost 30 million people, it makes demographic sense to address the needs of their share of the population. (Patel, 1997)

The significance of the above lies in the fact that malaria is this region is rife as well as the increasing prevalence of HIV / AIDS, both of which have a profound effect on women's health issues.

The literature also provides a wide range of studies that show that previous conventional methods of fighting malaria have proven in general to be ineffective. This aspect is concisely outlined in an article entitled, When Disease Resists; Malaria's Toll Rises in Tropical Regions As Effectiveness of Chloroquine Falls Off by David Brown (1994.) This article refers to an aspect that has already been touched on; namely that the malaria parasite has become resistant to many previously effective agents. "...the microorganism that causes malaria had become resistant to chloroquine, the standard medicine used to prevent and treat the disease for the previous 40 years." (Brown,1994) The study also refers particularly to the Kenyan situation."... researchers in Kenya - where chloroquine has been useless for a decade - reported that more than 25% of malaria cases in a recent study were resistant to the two more modern and expensive antimalarial drugs, mefloquine and doxycycline." (Brown,1994) This again raises the central concern that modern drugs are proving to be less and less effective in the fight against malaria.

As can be deduced for the studies mentioned above, there is a desperate need for a method that will be more effective in the fight against malaria in the region - particularly in the light of the fact that modern drugs are proving to be less effective. In this regard there are a number of research studies which indicate that insecticide impregnated or treated nets can provide a possible solution.

A source that provides an extensive range of data on his aspect is The Africa Malaria Report - 2003.

This study provides relevant and insightful statistics that show the effectiveness of impregnated netting. For example, "Randomized controlled trials in African settings of different transmission intensities have shown that ITNs can reduce the number of under-5 deaths by around one-fifth...saving about 6 lives for every 1000 children aged 1-59 months protected each year. (The Africa Malaria Report - 2003)

Furthermore, the report also states that, " The incidence of clinical episodes of Plasmodium falciparum infection is reduced by 50% on average. When used by pregnant women, ITNs are also efficacious in reducing maternal anaemia, placental infection, and low birth weight "(The Africa Malaria Report - 2003)

The study presents statistical evidence of the reduction of deaths and mortality rates, particularly among young children as a result of the use of the impregnated nets.

Randomized controlled trials showed an overall under-5 mortality reduction of 17% in communities provided with ITNs compared with communities not provided with ITNs. The impact was similar across a range of malaria endemicities. Impact derives not only from a reduction in malaria deaths, but also from reductions in child deaths due to other causes that are associated with, or exacerbated by, malaria, such as acute respiratory infection, low birth weight, and malnutrition. " (The Africa Malaria Report - 2003)

There is also evidence that these statistics may be conservative. This is due to the fact that impregnated nets have an indirect impact on the prevalence of infection. This in effect means that even households without nets are protected to a certain extent.

The efficacy of ITNs, because the impact of reduced mosquito burden extends to households and communities without nets, which reduces the apparent difference between study areas with nets and study areas without nets. The protection afforded to non-users in the vicinity is difficult to quantify, but it appears to extend over several hundred metres. From observed reductions in parasite prevalences, it has recently been estimated that, in the long-term, widespread use of ITNs - if regularly retreated - will massively reduce malaria transmission. (The Africa Malaria Report - 2003)

Another valuable study which expands on the above findings with particular reference to Western Kenya, is EFFECT OF SUSTAINED INSECTICIDE-TREATED BED NET USE ON ALL-CAUSE CHILD MORTALITY IN AN AREA OF INTENSE PERENNIAL MALARIA TRANSMISSION IN WESTERN KENYA, by Eisele et al. (2005).

This study "...present results from a study conducted in western Kenya where all-cause child mortality was assessed among a population with high levels of sustained insecticide-treated bed net (ITN) use for up to six years.." (Eisele et al. 2005)

The study found that in Western Kenya the introduction of impregnated netting was correlated with a "...significant reductions in all-cause mortality among infants 1-11 months old..." (Eisele et al. 2005)

However it is also important to note that "...there was no difference in the rate of all-cause mortality among children 12-59 months old with ITNs for 2-4 years, compared historically with children from villages without ITNs, after controlling for seasonality and underlying child mortality across calendar years..." (Eisele et al. 2005) main finding of the study is that impregnated nets are very effective in the reduction of mortality rates due it malaria.

Insecticide-treated bed nets (ITNs) have been associated with substantial reductions in malaria transmission. Accordingly, community-randomized controlled trials conducted across a range of malaria transmission settings in sub-Saharan Africa have shown ITNs and insecticide-treated curtains (ITCs) to be associated with up to a 30% reduction in all-cause child mortality over the first 1-2 years of the trials. (Eisele et al. 2005)

At the same time the study also found that that there a number of concomitant and complex issues which should be taken into account in ascertaining the effectiveness of impregnated bed netting. One of these is the issue that impregnated nets may adversely affect the immunity levels in older children. "However, there has been some concern that sustained use of ITNs may increase mortality rates in older children as a result of a delayed acquisition of natural immunity to malaria, especially within areas of intense, perennial malaria transmission." (Eisele et al. 2005)

The statistical findings of the study tend to confirm that assertion.

There was no increase in the proportion of child deaths at older ages (12-59 months old) of all child deaths within villages with ITNs for 5-6 years (48.1%) compared historically with villages without ITNs (47.9%), after controlling for seasonality (AHR = 1.03, P = 0.834). We find no evidence that sustained ITN use increased the risk of mortality in older children in this area of intense perennial malaria transmission. (Eisele et al. 2005)

In spite of this aspect the most important result of the study, which relates to the present paper, is that the use of impregnated nets did show a significant decrease in the rate of malaria infection and transmission in the very young in Western Kenya. "The ITNs were shown to substantially reduced malaria transmission in our study area and this dramatic decrease was sustained for more than four years." (Eisele et al. 2005) A further important aspect of this study was that:

The benefit of ITNs for preventing all-cause mortality was concentrated among post-neonatal infants and remained significant throughout the four-year ITN study. Based on the number of children saved per 1,000 protected during the four-year ITN study, we estimate that ITNs saved the lives of approximately 345 post-neonatal infants. Moreover, these children experienced no increase in mortality rates after reaching their second year of life.

(Eisele et al., 2005)

Therefore, the above data tends to suggest that impregnated nets have a very positive impact on malaria transmion and deaths. Notwithstanding the contrary statistics that tend to indicate that the immunity to malaria may be adversely affected by the use of impregnated nets at a later stage of development, the study concludes that, "... young children protected by ITNs may still garner significant immunologic protection from severe malaria." (Eisele et al. 2005) These results reflect positively on the question of the effectiveness of impregnated nets.

Results from this study demonstrate that ITNs continue to save the lives of young children, even with sustained use. Moreover, these results confirm that sustained ITN use is not associated with rebound mortality among older children. The global initiative to promote ITNs for combating early childhood deaths in malarious areas will undoubtedly result in more children surviving into adolescence and adulthood.

(Eisele et al. 2005)

As stated in the introduction, one of the factors affecting the issue of the effectiveness of impregnated nets is related to the financial and economic aspects as they relate to the affordability and implementation of the nets. An article that covers many of the aspects related to this issue is THE COST-EFFECTIVENESS OF PERMETHRIN-TREATED BED NETS IN AN AREA OF INTENSE MALARIA TRANSMISSION IN WESTERN KENYA. This study compared "...the costs and effects of insecticide (permethrin)-treated bed net (ITN) use in children less than five years of age in an area of intense, perennial malaria transmission in western Kenya." (Wiseman et al., 2003)

The results of the study were that impregnated nets were "...highly cost effective" (Wiseman et al., 2003)

The annual net cost per life-year gained was U.S. $34 and the net annual cost per all-cause sick child clinic visit averted was U.S. $49. After taking into account a community effect (protection from malaria afforded to non-ITN users who lived within 300 meters from users) these estimates decreased to U.S. $25 and U.S. $38, respectively. This study provides further evidence that ITNs are a highly cost-effective use of scarce health care resources.

(Wiseman et al., 2003)

However the study also makes it clear that there is more research needed in this area. "While there is a small but growing literature on the cost-effectiveness of ITNs, no information on cost-effectiveness in areas of intense, perennial malaria transmission is available. In addition, we know little about the extent to which the impact of ITNs on community members lacking ITNs...." (Wiseman et al., 2003)

Another report which supports the view that impregnated nets have a significant impact on the prevention of malaria is Antimalarial 'Bednets' Greatly Reduce Child Mortality in Africa, Studies Show. This report by David Brown (1996) refers to experiments in the journal Tropical Medicine & International Health, which suggest that impregnated nets "...can greatly improve a child's chance of surviving the first years of life." (Brown D. 1996) The report refers to the fact that the nets are effective because they are "low-tech" and cheap.

The report also refers to studies that confirm that the reduction of malaria can be related to the use of impregnated nets. "The chemical both repels mosquitoes and kills more than 90% of those that land on the netting. In Kenya, mortality among children between the age of 1 month and 6 years decreased 30% in villages using the bednets." (Brown D. 1996) study by Mcginn, (2002) asserts that "Instead of spraying, the most promising African programs rely primarily on "bednets" -- mosquito netting that is treated with an insecticide, usually a pyrethroid, and that is suspended over a person's bed. Bednets can't eliminate malaria, but they can "deflect" much of the burden." (Mcginn, 2002)

This article makes the important point that while impregnated nets are effective in control they are not a panacea of final solution to there problem of malaria in this region. But they can have a decidedly positive effect. "In effect, therefore, bednets can substantially reduce the disease. Trials in the use of bednets for children have shown a decline in malaria-induced mortality by 25 to 40%. Infection levels and the incidence of severe anemia also declined." (Mcginn, 2002)

The study also refers to a finding of particular relevance to the situation in Kenya. "... pregnant women who use bednets tend to give birth to healthier babies." (Mcginn, 2002) Furthermore, "... bednets can help transform malaria from a chronic disaster to a manageable public health problem -- something a healthcare system can cope with." (Mcginn, 2002)

Additional concerns and aspects

The literature deals with many areas of related concern with regard to the issue of the effectiveness of impregnated nets. These aspects are essential in order to ascertain the effectiveness of this mode of defense and protection.

An important aspect that has already been dealt with is the economic and financial implications. There is a concern which is reiterated in the literature that the small budgets and poor economies of countries like Kenya can inhibit the application of this preventative measure. "The average cost for the implementation of malaria control plans related to disease management/treatment is estimated to be $300,000 per country per year. In addition, $1m per year per country is required for vector control and control of epidemic outbreaks." (Banfield, 1998) The high rate of malaria in the region can also have the effect of retarding normal economic growth and financial development. As one study states; "The cost of ITNs is a barrier to their widespread use." (The Africa Malaria Report - 2003) further aspect of this concern is that it has been found that in Kenya household members are willing to pay for ITNs, "...but typically less than the current cost. "(The Africa Malaria Report - 2003) Another finding of significance is that; "Poor households are less likely to have ITNs or any net. The disparity contrasts with a probably higher burden of malaria in poorer households, who live in houses and areas that typically allow for more exposure to mosquitoes, and who are less able to afford treatment once infection has occurred." (The Africa Malaria Report - 2003)

An aspect, on which there has been relatively little research, is the reaction and response of the affected community to the use of impregnated nets. An article entitled COMMUNITY REACTIONS TO THE INTRODUCTION OF PERMETHRIN-TREATED BED NETS FOR MALARIA CONTROL DURING A RANDOMIZED CONTROLLED TRIAL IN WESTERN KENYA, states that in order for impregnated bed nets to be successful there should be a greater acceptance in the community.

Among the aspects that cause problems in this regard are the following: " Concerns expressed included fear of the insecticide, thought by some to be a toxic family planning aid, the taking of blood during clinical studies, and the mixing up of family ITNs during net re-treatment, which would violate cultural taboos..." (ALAII J. et al. 2003) The study goes on to state that; "Questions remain, however, on how best to promote correct and sustained use of ITNs, particularly in areas without a tradition of bed net use." (ALAII J. et al. 2003)