This paper has not been previously submitted for publication. However, the abstract was published in the ASTMH 67(2) p210 as a supplement to the ASTMH AGM in Denver, Colorado, 2002.

THE INCIDENCE OF MALARIA IN LAGOS

Aderounmu A Omotayo

ABSTRACT

Statistical analysis using the chi-square concept was used to determine the prevalence pattern of malaria in metropolitan Lagos. Data used for the analysis were collated from the parasitology laboratory of the Lagos University Teaching Hospital from 1991 to 1999. Over 6 500 blood samples were examined during the period. Malaria remains one of the greatest scourge of Lagos, Nigeria with a relatively high infection rate which shows an increase from 27.8% in 1992 to 68.9% in 1999. There were significant differences in the prevalence of Plasmodium falciparum infection in all the years following 1991. The general overview of the incidence of P.falciparum infection in urban Lagos between 1991 and 1999 shows that the prevalent pattern is imperturbable over the years. Lagos residents have a high level of predisposition to the dreaded malaria parasite inspite of being a modern city. This study sheds an unhappy perspective on the socioeconomic development in Nigeria and calls for uegent implementation of intervention procedures against malari and other prevalent diseases.

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Malaria caused by Plasmodium falciparum remains a major cause of human mortality in the world especially in the tropics and outstanding in sub-Saharan Africa affecting mainly children and pregnant women1. Malaria remains arguably the greatest menace of our society in terms of morbidity and mortality and the occurrence of malaria in our part of the world correlates with poverty, ignorance and social deprivations in the community. An accurate knowledge of the incidence of malaria in endemic areas would be necessary towards the planning and development of effective preventive measures against the deadly scourge of malaria.

Our aim in this study was to determine the prevalence of malaria in urban Lagos from 1991 to 1999. We attempt to check for significant differences in the pattern of infection by examining the available data from 1991 to March 1999. The data between 1994 to 1996 were not available for analyses when this study was conducted. Records of clinical blood samples examined at the parasitology laboratory of the Lagos University Teaching Hospital from 1991 to 1993 and 1997 to 1999 were studied. Usually the blood samples are examined immediately they are brought to the laboratory. Thick and thin films are employed for the examination of blood for malaria parasites.

The prevalence of P.falciparum from in this study shows a wide range as shown in Table 1. Chi square analysis revealed that the prevalence from 1992 to 1999 were statistically significantly different from the test level of 40.2% in 1991 (P0.05)

Table 1. The spectrum of malaria parasite infection at the Lagos University Teaching Hospital, 1991-1999

Year Number of samples examined Number of positive samples Percentage(%)

1991(Oct -Dec)58223440.2

1992(Jan-Dec)166146127.8

1993(Jan-Oct)53315929.8

1997(Jan-Dec)1968111256.5

1998(Jan-Dec)1861107957.9

1999(Jan-Mar)15810968.9


I found in this study that the number of people (children and adults) reporting with malaria at the Lagos University Teaching Hospital increased steadily from 1992 to 1999. It is not clear what factors lead to the decline of reported cases between 1991 and 1992 but the number of cases covered for 1991 were for 3 months only. Similarly in 1999, the first three months of the year gave a 68.9% of positive cases. Since this study was carried out with available data, we cannot predict for sure what the influence of the overall reported clinical cases may have had on the observed prevalence at the end of the 1999. Nevertheless the complete data used for 1992, 1997 and 1998 would suggest that the prevalence of malaria is on the increase.

Lagos is a modern city with a population assumed to be over 10 million people. The results shown in this study showed that the control of malaria is rather difficult. It is of interest to note that Lagos has developed rapidly over the years (compared to other cities in Nigeria and other parts of West Africa) with inappropriate urban planning in terms of human population growth and natural system interactions. Consequently, Lagos residents still have high level of predisposition to malaria over the past many years.

A number of factors may contribute to the maintenance of the malaria disease vector and the high level of transmission in Lagos. Identifiable among these are: ditches, gutters and other man-made temporary pools of water, some of which results from broken pipes and improper or blocked drainage systems. Poverty is a bane of developing countries and along with ignorance, urban farming, deteriorating infrastructures and overcrowding (very common in Lagos), a vicious cycle is formed that makes it extremely difficult to control malaria and perhaps other diseases. Other key factors still contributing to this unfortunate situation are social attitude including occupations such as car washing in major areas of the city (I stand by this factor even though it was one major reason this paper was never published!) , poor water delivery systems, lack of sanitation service development, inadequate knowledge of mosquito-human interaction and haphazard urbanization. Some of these factors have been identified in other countries such as Central Africa and Kenya 2-4.

This study sheds an unhappy perspective on the socioeconomic development of Nigeria. Rather than witnessing an improvement in malaria control, we are experiencing a decrease in standard. We are of the opinion that sanitation should be a daily exercise and not fixed to certain periods. We also think that adequate health education and proper developmental planning may help to check the menace of malaria. In addition, poverty alleviation and socioeconomic empowerment may help to alleviate the vicious cycle of disease-poverty interaction.

Finally, the National Malaria Control Program in Nigeria and other endemic countries should be intensified to reduce the devastating effects of the disease on both the economy and human lives. The development of an effective vaccine along with other malaria control measures is needed for reducing the burden of malaria in sub-Saharan Africa and worldwide. However, in the absence of a licensed vaccine and in the face of increasing levels of resistance to recently available drugs, I suggest here that since Insecticides Treated Materials have not been proven to prevent the acquisition of malaria immunity in children, they should be introduced to all and sundry.

ACKNOWLEDGEMENTS

My appreciation to Mrs T.I Osinubi, Mrs D.O Opedun, Messrs J. Okpe and T. Oloye, all of the parasitology laboratory, College of Medicine of the University of Lagos, Nigeria for making available the raw data of parasitological examinations.

REFERENCES

1. Roche J, Guerra-Neira A, Raso J, Benito A, 2003. Surveillance of in vivo resistance to Plasmodium falciparum to antimalarial drugs from 1992 t0 1999 in Malabo (Equatorial Guinea). Am J Trop Med Hyg 68(5): 598-601.

2. Keating J, Macintyre K, Mbogo C, Githeko A, Regen JL, Swalm C, Ndenga B, Steinberg LJ, Kibe L, Githure JI, Beier JC, 2003. A geographic sampling strategy for studying relationships between human activity and malaria vectors in urban Africa. Am J Trop Med Hyg 68(3): 357-365.

3. Robert V, Awono-Ambene H.P, Thioulouse J, 1998. Ecology of larval mosquito, with special refernce to Anopheles arabiensis (Diptera: Culicidae) habitats in western Kenyan. J Med Entomol 38: 282-288.

4. Trape JF, Zoulani A, 1987. Malaria and urbanization in central Africa: the example of Brazzaville. Part II: Results of entomological surveys and epidemiological analysis. Tran R Soc Trop Med Hyg 81: 10-18.

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This thesis was carried out under the supervision of Prof. Adetayo Fagbenro-Beyioku of the College of Medicine of the University of Lagos.

The re-writing / shortening of the thesis as it appears here is entirely my decision.

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