1DEPARTMENT OF MEDICAL LABORATORY SCIENCES,

FACULTY OF MEDICINE AND HEALTH SCIENCES,

A study was carried out on the prevalence of malaria among pregnant women in Owerri Municipal council area in Imo State, Nigeria between December 2001 and October 2002. Of 250 women examined, 200 women were pregnant. Of the 200 pregnant women examined, 22 (11.0%) had malaria parasitaemia. Prevalence of malaria was significantly higher in pregnant women than in non-pregnant women, in pregnant women from Owerri General Hospital than in Owerri Federal Medical Centre, in women within the second trimester (13.9%) than other gestational periods (P<0.05). Women less than 25 years of age are mostly infected (121%), followed by women within 26-35 years of age. Pregnant women with low packed cell volume (PCV) had higher prevalence than in women with normal PCV. Pregnant women with less than 9.1g/d haemoglobin had highest prevalence than others with higher haemoglobin levels. Other effects of malaria among pregnant women observed were fever, headache, loss of appetite, nausea and body pains.

Malaria is an important parasitic disease estimated to affect 100 to 300 million people globally. The mortality in Africa alone exceeds million people per annum. Human malaria is caused by Plasmodium vivax, P. ovale, P. malariae and P. falciparum. Of these, the latter is the most frequent cause of severe malaria, including cerebral malaria.

Malaria is currently regarded as the most common and potentially the most serious infection occurring in pregnancy in many Sub-Saharan African countries (Okonofua 2001). The majority of malarial infections that occur in pregnancy are due to P. falciparium, and less commonly to other Plasmodium species. The parasite is transmitted by the female anopheline mosquito, which finds a natural habitat in the hot and humid climate of many African countries.

For several decades, malaria has been recognized as a serious public health problem in Africa, especially in children. By contrast, less attention has been given to the severe problems posed by malaria occurring in pregnant women. The prevalence of malaria in pregnancy varies considerably in different parts of Africa. In Ile-Ife, Okonofua and Abejide (2001) reported an incidence of 16% of Plasmodium parasitaemia.

Other studies from various parts of Africa have documented high rates of malarial parasitaemia among pregnant women (Menon 1972; McGregor et al 1983, Mbanugo & Okoroudo 2002; Akanbi et al 2002). To date, few studies have investigated the incidence of clinical malaria fever in pregnant women, probably because many cases of malaria are treated outside the health care system. However, parasite density is an important proxy for malaria in pregnancy since many of the consequences of such malaria are related to the mere presence of the parasite rather than clinical malaria.

There appears to be paucity of report on the prevalence of malaria in pregnant women in Imo State, Nigeria. This report presents our observations on the prevalence of malaria in pregnant women attending ante-natal clinics in Owerri municipality taking cognizance of their age, gestational period, parity, packed cell volume (PCV) as well as their haemoglobin levels.

The study was conducted at Owerri Municipal (urban); Imo State. Owerri Municipal commonly called "Owerri Nchise" is made up of five autonomous communities namely: Umuororonjo, Amawom, Umuonyeche, Umuonyima and Umuodu. There are several villages and clans. The subjects investigated are 130 pregnant women attending ante-natal clinics at Owerri Federal Medical Centre and 70 pregnant women attending ante-natal clinic at Owerri General Hospital between December 2001 and October 2002. The patients sampled are those coming for maternity registration for the first time for that particular pregnancy whether primigravidae or multigravidae, of age between 18 and 45 years. Information on the patient’s age, occupation, gestational period, parity, name and malaria protective measures employed at home were recorded. Another 50 healthy non-pregnant women of the same age bracket mainly students and female workers of Imo State University Owerri were used as controls. Thick and thin blood smears collected by venepuncture from the two groups were sent together to the laboratory for parasitological diagnosis without disclosing the sources of the smears to the laboratory investigator. The slides were stained in the standard way with a 1 in 10 dilution of Giemsa stain for 30 minutes and identification of the species of human malaria parasites in the blood films was carried out according to the WHO (1980) method. Haemoglobin expressed in g/dl was measured while the packed cell volume (P.C.V.) was recorded using a Hawsley haemotocrit reader. In both groups, malaria cases were tested using X²-test. Significant differences were designated at P<0.05.

A survey on the prevalence of malaria in non-pregnant and pregnant women was carried out in Owerri Municipal council area of Imo State, Nigeria. A total of 250 women were sampled. Of these, 200 (80.0%) and 50(20.0%), were pregnant and non-pregnant respectively. Of the non-pregnant women examined, 2 (4.0%) had malaria parasitaemia while 22 (11.0%) of the pregnant women also had malaria parasite in their blood. Table 1 summarizes the prevalence data. A Chi-square analysis revealed that malaria infection and pregnancy are dependent (P<0.05).

The prevalence of malaria in pregnant women attending ante-natal clinics in Owerri is shown in table 2. Two hospitals:- Owerri Medical Center and General Hospital were used for this study. Of the 200 pregnant women examined, 130 and 70 were from Owerri Federal Medical center and Owerri General Hospital respectively. Infection was significantly higher in Owerri General hospital than in Owerri Federal Medical Centre (P<0.05). Also, the prevalence of malaria in relation to gestational periods was analyzed. Women within the second trimester had the highest infection rate (13.9%) followed by women within the third trimester (8.0%) while there was no infection amongst the 10 women within the first trimester examined. Malaria infection was significantly higher in women within the second trimester (P<0.05) than in the other gestational periods. Details are shown in table 3.

Table 4 depicts the prevalence of malaria in relation to parity. Of the 200 pregnant women examined, 49 and 151 are primigravidae and multigravidae respectively. Majority of the infected pregnant women (18) were multigravidae. However, there was no significant variation amongst parity (P>0.05). The age-related prevalence of malaria is shown in table 5. There was a slight variation in the prevalence rate amongst various age groups. The highest prevalence of 12.1% was recorded in women less than 25years of age, followed by women within the 26-35years of age (10.7%) while women older than 36years had no cases of malaria.

Table 6 shows the prevalence of malaria in relation to packed cell volume (PCV) of the pregnant women. It revealed that women with less than normal packed cell volume had higher prevalence than those with normal packed cell volume, although it was not statistically significant (P>0.05). Pregnant women with less than 9.0g/ld haemoglobin had the highest prevalence of 16.7%, followed by women of Hb from 9.1-12.0g/gl (19.7%), while women with haemoglobin level above 12.0 g/dl had no malaria parasite (Table 7a). The mean haemoglobin level of the infected pregnant women were lower than that of the non infected pregnant women. However, this was not statistically significant (P>0.05).

Most of the pregnant women with malaria complained of fever, headache, loss of appetite, body pains among other signs. Maria is indeed a major problem of most pregnant women in the area.

The present study has shown that malaria is a serious problem seen in pregnant women sampled in Owerri. However, the prevalence rate of 11.0% observed herein is very low compared to either the 60% observed in pregnant women in Anambra (Mbanugo and Okoroudo 2002), 17.5% in Enugu Urban (Eneanya, 1996) or 18.5% reported in Western Nigeria (Akanbi et al 2002). For several decades, malaria has been recognized in Africa, especially in children. Conversely, less attention has been given to the severe problems posed by malaria occurring in pregnant women. In many African countries where malaria is holo-endemic, non-pregnant female adults eventually achieve a significant level of immunity against malaria. It is interesting to note that during pregnancy, these women experience considerable decline in their levels of immunity to malaria infection. (Sholapurker³ et al 1990, Gilles¹ et al 1969; Brabin² 1983; Morondo⁴ et al 1992 and Read⁵ 1997). Thus, as compared to non-pregnant women, pregnant women of the same age and parity have lower levels of both cell-mediated and humoral immunity to malaria (Okonofua 2001). Consequently, pregnant women tends to have more episodes of malaria fever. Moreso, malaria has substantial devastating effects on the developing feotus and makes substantial contributions to the large burden of perinatal and neonatal morbidity and mortality in holo-endemic areas. This therefore could explain why more pregnant women than non-pregnant women had infections in the present study.

The prevalence of malaria in pregnancy varies considerably in different parts of Africa. A prevalence of 11.0% was recorded herein. Similar studies from other parts of Africa has reported high rates of malarial parasitaemia among pregnant women. Menon 1972; McGregor et al 1983; Okonofua and Abejide 1996; Morley et al 1964; Watkinson and Rushton 1983). This could be attributed to several factors including exposure rate to infective female mosquito bites, environmental factors, socio-economic factors among others. Observations showed that the highest infection rate of 13.9% occurred during the second trimester. This observation is in line with those of Pingong (1969) and Bray et al (1979) in other areas. In contrast, Maclead (1988) and Amadi et al (1994) opposed this observation. They noted that malaria parasitaemia was significantly higher in pregnant women in the first trimester. Generally, it is now well known that young women in their first and second pregnancies are more susceptible to malaria. Indeed, several studies have reported significantly high rates of parasitaemia in primigravidae and secondigravidae (McGregopr et al 1983). This is due to the substantial reduction in levels of immunity associated with first and second pregnancies. According to Okonofua (2001), at higher parities there appear to be a boosting of immunity level due to the initial exposure to malaria parasites in the first and second pregnancies.

Pregnant women 25 years of age and below have higher prevalence rate of 12.1% and most primigravidae belong to this group. While pregnant women in the age 26 – 35 years have lower rate of infection and those of the group 36 – 45 years have the least prevalence rate. Normally, primigravidae have a higher prevalence rate of parasitaemia (Menedez 1995) since their immune system is still building up as compared to the multigravidae. A partial explanation to this observation in this study could be that apart from immunological status, resistance to malaria may also be influenced by other factors such as haemoglobin type, erthrocyte glucose -6- phosphate dehydrogenase activity and well-balanced nutritional status (Monif, 1974).

The effect of parity on infection is highest in multigravidae. This is because increase prevalence rate may occur when the immunological state of the host changes as in pregnancy allowing an increase in the degree of parasitaemia. In this study, the PVC value of pregnant women below normal value (20-29%) showed a higher prevalence rate of (11.4%) as against those with normal range (30.38%) with prevalence rate of 10.9%. This may however be related to the lowered haemoglobin in pregnancy (Anosike in preparation).

By contrast, chemoprophylaxis is currently thought to be the most effective method for preventing the maternal and fetal effects associated with malaria in pregnancy. The world Health Organization has recommended the routine administration of anti-malarial drugs to all pregnant women on holo-endemic areas as an important strategy to prevent malaria and that such drugs be given in pregnancy as early as possible. Indeed, the routine administration of anti-malaria drugs is one of the six elements in the current roll back malaria initiative being propagated by the World Health Organization and has been endorsed by several countries across Africa, including Nigeria.

To date, there is still no agreement on the best drug combinations to use for the prevention of malaria in pregnancy. Initially, oral primethamine and chloroquine administered weekly were used in various parts of Africa as chemoprophylatic agents. However, recent reports indicate that these are no longer effective in reducing parasitaemia in pregnancy as a result of the high incidence of chloroquine resistance (Ezedinachi et al 1998). Other agents that have been used for chemoprophylaxis in pregnant women include proquanil, dexcycline, primaquine, doxycycline, metloquine, halofantrine and quinine but none has proven to be completely effective (Salako, 1993, Ezedinachi et al 1996).

Therefore, efforts aimed at controlling and preventing malaria in pregnancy should include among others, avoidance of mosquito bites, preventing the breeding of mosquito larvae, destroying adult mosquitoes by regular spraying of all houses with residual insecticides as well as planned health talks on the disease transmission to pregnant women during ante-natal clinic. These would be very useful as a preventive rather than curative approach.