| Abstract|| |
Background : Disease surveillance identifies prevention targets and provides information to monitor growth. Malaria eradication in Africa was a high priority within the United Nations Millennium Development Goals. This work aimed to accentuate the status of malaria in Dschang amid rigorous interventions. Materials and Methods : In a cross-sectional study, 515 persons, comprising 300 pupils in six primary schools and 215 individuals living around a municipal lake, were screened for malaria using standard parasitological methods. A questionnaire was administered for relevant epidemiological information. Results : Seventy-nine (15.3%) persons positive for Plasmodium were all asymptomatic; 71 (13.8%) cases had Plasmodium falciparum, and 8 (1.5%) Plasmodium malariae; Loa loa and Mansonella perstans (0.2% each) were also identified. There was a significant negative correlation between age and infection (r = -0.82). The parasite density ranged from 60 to 22590 parasites/mm 3 of blood, mean 1014.68 p/mm 3 , with 3 (0.6%) severe cases (> 5000 p/mm 3 ). Children aged 0-4 years were most vulnerable, Plasmodium index (PI)-33.3%. The PI was higher in pupils' resident on the semi-rural swampy outskirts conducive for mosquito development. Distance from the lake had no influence on PI. Parasitemia increased significantly in August. Dschang was established mesoendemic for malaria with a low density. Increasing urbanization, health promotion, good drainage and sanitation, the use of mosquito nets, chemoprophylaxis for pregnant women, treating children up to five years free, and the use of insecticides to kill adult mosquitoes seemed to reduce malaria transmission and its fly vectors. Conclusion : Scaling up, greater efficiency, and equitable delivery of malaria control initiatives would be fruitful.
Keywords: Cameroon, malaria, parasite density, school children, swamps
|How to cite this article:|
Payne VK, Fusi-Ngwa CK, Ndambi E, Mpoame M. Plasmodium index, prevention, and control of malaria in Dschang municipality, Cameroon. Ann Trop Med Public Health 2013;6:166-72
|How to cite this URL:|
Payne VK, Fusi-Ngwa CK, Ndambi E, Mpoame M. Plasmodium index, prevention, and control of malaria in Dschang municipality, Cameroon. Ann Trop Med Public Health [serial online] 2013 [cited 2020 Aug 10];6:166-72. Available from: http://www.atmph.org/text.asp?2013/6/2/166/116496
| Introduction|| |
The control of malaria in Sub-Saharan Africa where over 90% of all malaria deaths in the world occur has been a priority since for ages.  Surveillance is crucial in disease prevention; it enables the planning and execution of more effective and robust evidence-based policies and strategies; advances data for development appraisal; and establishes priority areas for future interventions.
This study was undertaken to highlight the prevalence of malaria in six primary schools and in families living around the municipal lake in Dschang, West Region, Cameroon, to aid amelioration efforts for this disease.
| Materials and Methods|| |
Geographical location and climate
Dschang, the headquarters of Menoua Division, is situated on latitude 05°20' N and longitude 10°03'E with an altitude of 1382-1500 m. The winds have a speed of 1-4 m/s (95.7%). There are two characteristic seasons: A rainy season running from mid-March to mid-November, and a dry season, from mid-November to mid-March. The maximum annual temperature is 25°C and the minimum 15.1°C. The annual precipitation ranges from 14.3 mm to 2288 mm. The relative humidity is 76.8%. The average annual sunshine is 1873 hours. The average daily temperature is 20°C. The climate is of the Sudan - Guinean type.
Vegetation, hydrology, and social characteristics
The vegetation is grassland savannah, interspersed with few trees of various types. There are a few slow-flowing streams that meander around the town and one, which is fast-flowing, forming a waterfall. There is a municipal lake, which is in Foto/Keleng; people live very close to this lake. The soils are the ferrallitic type. According to the statistical annals of Cameroon (1998), Dschang had a population of 67,000 inhabitants in 1997. This population has increased due to the increasing population of students in the University. The natives are of the Bamileke ethnic group with the main religious groups being Christians and Moslems. The principal occupation is business and subsistence farming, but the majority of youths are students or pupils.
This work was carried out from May to August, 2010 in six primary schools randomly selected in the most populated areas of Dschang town namely Government Bilingual Primary School, Ecole Publique (EP) du Centre Groupe IA, EP du Centre Group 1B, EP Group II, EP Group III and EP Group IV, and around the municipal lake in Foto/Keleng.
Ethical clearance was obtained from the Divisional Medical Officer for Menoua. The study population (the pupils of the schools and families living around the municipal lake) was sensitized prior to the start of this work with a health talk explaining the "raison d'être " for the study, presenting the materials to be used and a sample questionnaire form for data collection. Pupils were instructed to seek parental consent before participating in the exercise. Appointments were made on the dates of visits to each primary school.
Sampling and physical examination
Only pupils who were willing to participate and whose parents had consented to the study took part in the screening exercise for malaria. Around the lake, the sampling was done only in houses where the parents accepted and the occupants were interested. A house - to - house blood sample collection was done between 14.00 H and 19.30 H.
The subjects were interviewed and the questionnaire completed accordingly. Information sought included the name, age, sex, religion, division and village of origin, ethnic group, quarter of residence, whether respondent was on drug therapy and drug specifications, occupation and educational level of parents, and whether parents were separated, divorced, or living together. The parents gave information about the very young children who could not answer questions.
All children (0-19 years) included in the study were physically examined for liver/spleen enlargement by a clinician. They were laid on a couch while the abdomen was palpated. The body weight and arm circumference were taken using a balance and a measuring tape.
Collection and processing of blood samples
After the interviews and physical examinations, each respondent was pricked on the pulp of the major or annular finger of the left hand, which was previously cleaned with cotton damped with 95% alcohol using a sterile disposable lancet (blood lancet sterilized UDA 1030 AB Amsterdam). Two to four drops of blood were expressed from the finger unto a clean, labeled, grease-free microscope slide. Using the same lancet, the blood was spread in a circular manner on the slide and made into an even thick smear. The slides were air-dried on a flat surface, arranged on holders, and taken to the Animal Ecology Laboratory of the Department of Animal Biology of the University of Dschang for staining and identification of blood parasites. 
A counter was used to establish the number of ring forms (trophozoites) per 200 white blood cells by moving the slide systematically from one end to the other. The parasite density (PD) and plasmodium index (PI) were calculated and described as follows:  PD:
The chi-square test was used to find out the relationship between epidemiological factors and malaria infection. To evaluate the influence of some epidemiological factors on PI, analysis of variance (ANOVA) was used with level of significance at 0.05. 
| Results|| |
Between May and August 2010, a total of 515 individuals were examined using standard parasitological methods for malaria. Plasmodium trophozoites were observed in the blood smears of 79 (15.3%) persons, all asymptomatic- 71 (89.9%) had Plasmodium falciparum, and 8 (10.1%) Plasmodium malariae. Other Plasmodium species: Ovale, vivax, and knowlesi were not identified in the study population. One case each of Loa loa and Mansonella perstans was recorded.
The 515 persons screened comprised 258 males with 44 (17.1%) positives and 257 females with 35 (13.6%) infected cases, with no statistically significant difference (P = 0.15) between both sexes. There was no correlation between average age and prevalence amongst the males (r = 0.15), while there was a significant negative correlation between average age and prevalence amongst the females (r = -0.71) [Table 1].
The PI was higher (16.5%) in 363 children and individuals between 0 and 19 years compared with the rate (12.5%) obtained for 152 respondents who were ≥ 20 years. There was a significant negative correlation between age and infection (r = -0.82). Among 104 children aged 2 to 9 years, 26 were infected with Plasmodium giving an infection rate of 25%, placing Dschang in a meso-endemic zone.
The monthly distribution of PI in the study population revealed the highest-32.8% (P = 0.0023) during the month of August, [Table 2].
Of 285 children with a normal liver/spleen, 52 (18.3%) were infected with Plasmodium, while 5 (9.3%) of 54 children with an enlarged liver/spleen had Plasmodium infection [Table 3]. For the 0-9 year's age group, the PI was significantly higher (P < 0.001) in children with a normal liver/spleen size (27.8%) than in children with an enlarged liver/spleen (7.1%). Nonetheless, it is worthy to note that more children with a normal liver/spleen were examined than children with an enlarged liver/spleen. The educational level of the children's parents had no influence on PI. On the contrary, the infection rate was significantly lower (P = 0.01) in children whose parents were living together than in children whose parents were separated.
Infection rates obtained in residential areas were not significantly different (P > 0.05), a high PI was recorded for Grand Mission (50.0%) even though only four pupils were screened from that quarter, followed by Madagascar with a relatively lower rate of 16.7% and Foto (16.3%) [Table 4].
The examination of 215 respondents resident at varying distances from the lake indicated that 41 (19.1%) were positive for Plasmodium [Table 5]. Distance from the lake had no significant influence (P > 0.05) on PI.
Generally, parasite density (PD ) i.e. parasites/mm3 of blood was low [Table 6] More than one third of the infected population had a PD within the range of 201 to 400 p/mm 3 of blood. Only 3(0.6%) cases were severe (PD > 5000 p/mm 3 ) but were, however, asymptomatic. The highest PD was 22,590 p/mm 3 of blood.
There was no significant difference (P > 0.05) in the mean PD in the residential areas under study, with only one quarter (Grand Mission) having one severe case of parasitemia. Of the 41 respondents who were infected with Plasmodium around the lake, their average PD was 1261.46 p/mm 3 with a minimum PD of 60 p/mm 3 and a maximum PD of 22590 p/mm 3 . There was no significant difference (P > 0.05) in the mean PD for the various distances from the lake, and only two cases (0.4%) living at a distance of 101 to 200 m from the lake had severe Plasmodium infection.
There was no correlation between sex and PD (r = 0.2) and no significant difference in the mean PD for the various age groups (P > 0.05) and for the months for the study. The highest mean PD (1990 p/mm 3 ) was in August, while the lowest (424 p/mm3) was in June. The three severely infected cases recorded consisted of one female in the 5-9 years age group (infected in May) and two males in the 10-14 years age group (infected in August).
| Discussion|| |
For decades, malaria has been Africa's biggest killer, continually ravaging the African continent due to inadequate healthcare systems and insufficient finances to adequately tackle the disease in most countries. This disease is the major cause of morbidity and mortality among children under five, pregnant women, people living with HIV/AIDS, victims of disasters, and the poor in Sub-Saharan Africa. ,, It is a major obstacle to socio-economic development, reportedly related to school absenteeism and ill-health exemption from work.  Low concentration or low performance at work or school, enormous financial burden arising from the purchase of drugs, and payment of hospital bills are other socio-economic consequences of malaria.  Malaria can retard development by rendering some regions inhabitable, thereby exerting a dissuasive effect on international commerce, foreign investments, and obstructing the development of sectors such as tourism. The ills related to malaria actually led to the reference of Africa as a dark continent.  In the nineties, malaria was selected by the World Health Organization's special program for research and training in tropical diseases as one of the parasitic diseases that threatened international health.  Until now, morbidity and mortality rates for malaria top the chart of common infectious diseases in Africa rivaled only by HIV/AIDS in the 20 th century. , As a matter of fact, malaria constituted about 10% of Africa's disease burden in the seventies.  It slows down economic growth by up to 1.3% each year  and costs African countries U.S. $ 12 billion.  In 2006, statistics from the Ministry of Public Health (MPH), Cameroon, showed that malaria accounted for 40-45% of medical consultations, 36.5% of the total number of deaths in health facilities, 42.1% of morbidity in children below the age of five, 20% of sick leaves, and 46% of annual household health expenditure. More so, still in 2006 in Cameroon, malaria was only closely followed by HIV/AIDS in the extent of mortality.  Recently, the disease is responsible for 49% of consultations and 59% of hospitalizations during pregnancy leading to abortions, premature labor and deliveries, and low-birth weight, thereby exposing babies and mothers to early deaths. 
The last ten years have seen a resurgence of interest in malaria as a disease of major public health importance. The Roll Back Malaria partnership -RBM  was launched in 1998 as a partner between the WHO, UNICEF, UNDP, and the World Bank to co-ordinate global action against the disease. This partnership targeted malaria mainly through prevention and treatment, especially in pregnant women, HIV/AIDS patients, non-immune travelers in high endemic zones, and children under five who are highly susceptible to the disease. It had the goal of halving the burden of malaria by 2010 by equitably scaling up interventions such as insecticide-treated nets (ITNs), effective treatment of malaria cases, indoor residual spraying, taking care of malaria in under-fives, intermittent preventive treatment of pregnant women in areas of stable transmission, and epidemic detection and response. ,, Under the auspices of the RBM, Heads of State from across Africa met in Abuja, Nigeria in 2000 to express their commitment to combating malaria. The UN declared 2001-2010 the decade to roll back malaria in developing countries, particularly in Africa, and set malaria amongst other diseases as a high priority within the internationally agreed development goals and within the UN Millennium Development goals. , Many epidemiological studies are documented on malaria in several parts of Cameroon with regards to vectors/treatment dynamics. ,,,,
The PI of 15.3% obtained in this study is much lower than the 37% reported by Couprie et al.  in 1990 from Bamendjin, which is almost in the same latitude as Dschang. This could be explained by the fact that Dschang is relatively urban, while Bamendjin is a rural area. With increasing urbanization, especially marked by a gradual increase in the population of students in Dschang, there is a general problem of wastewater management. Environmental changes bring about important entomological change, used water containing organic matter disfavors the development of the Anopheles vector. Thus, the transmission of malaria is generally less in urban areas than in the corresponding rural areas.  A higher PI of 30.2% is documented in Efok,  17.5% in Djohong,  and 22.1% in two villages in Adamawa namely M'bang Boum and N'Déna, North Region of the country.  The results of the questionnaire administered indicated that self-medication particularly against malaria is commonplace in Dschang, and this might have also contributed to the low Plasmodium rate recorded in this study. Good drainage channels especially around homes, the use of mosquito nets alongside chemoprophylaxis for pregnant women, moving from a weekly or bi-monthly chemoprophylaxis with chloroquine to sulfadoxine-pyrimethamine, and the use of insecticides to kill adult mosquitoes and keeping all surroundings clean and clear of grass have been in practice to minimize malaria in Dschang and Cameroon at large. Frequent health talks or campaigns in schools, markets, and hospitals have gone a long way in educating the masses on protective methods against malaria and its fly vectors. Other strategies currently employed against malaria in Cameroon include updating existing treatment policies, treating children up to five years free, and distribution of mosquito nets to communities, not just to children and pregnant women. Testing new drug combinations and re-evaluating drug combinations that are currently available to extend their therapeutic life are in the pipeline. Thus, the relatively low rate documented herein compared to previous rates in the country is understood.
In this study, infection rates for malaria were slightly higher (14-16.7%) for quarters on the outskirts of Dschang town (Foto, Madagascar, Ngui, Tchaulé, Camp Gendarme, Keleng and Mingu), which are definitely semi-rural, and thus mosquito development is favorable.  Also, Ngui and Madagascar have two species of malaria vectors (Anopheles gambiae and Anopheles funestus), while Grand Mission, with an infection rate of 50%, has eight species of the vector (A gambiae, A. funestus, Anopheles moucheti, Anopheles nili Anopheles A paludis, A ziemanni A. hancocki; A. wellcomei) with many swampy areas and pools of water, which are potentially favorable sites for the development of the Anopheles larvae.  The finding that distance from the municipal lake had no significant influence on PI was not surprising, as entomological studies in Keleng around the lake have revealed a very low count of Anopheles mosquitoes. 
The highest PI (33.3%) recorded in this study was in children between 0-4 years. This finding is similar to a report by Messi  in Efok with the highest PI of 57.7% in children between 1 and 4 years. Goff et al.  in Edea (Bilalang) also reported the highest PI of 30.2% in children in the 0-15 year's age group, and Ripert et al.  reported a PI of 45.5% for children of 2-9 years old in Bini (Adamawa). These results confirm the fact that children are more susceptible to malaria or suffer more serious infections than adults. The situation is aggravated in babies who are not breastfed or malnourished children since this increases vulnerability to infections. Protein energy malnutrition and under nutrition, which are common in developing countries, greatly weaken immune responses in children.  The gradual decrease of PI during the later stages of life as observed in this study may be due to immunity. Even though this immunity may exist, there is still continuous infection till death probably resulting from the presence of trophozoites causing relapses or recrudescence or the continuous susceptibility to the anopheline bite leading to re-infection.
The very high PI recorded in August during this study corresponds to the favorable absolute temperature of 28°C and 97% humidity, which favors the development of the parasite in the mosquito, and thus, increases the lifespan of the mosquito and further increases its potentials to transmit the Plasmodium parasite.
A few infected cases (0.6%) in this study had a PD of > 5000 p/mm 3 but showed no symptoms of malaria. Such individuals had lived in highly endemic malaria zones and tended to withstand high parasitemia.
P. falciparum was the dominant species in the subjects studied, and this finding is in conformity with studies throughout Africa.  The absence of P. vivax in the study population was not surprising since black Africans lack the Duffy blood antigen with surface receptors for P. vivax.
Dschang is mesoendemic for malaria. Scaling up, more effective and equitable access to malaria interventions is necessary to achieve the target goal.
| Acknowledgement|| |
The authors are very grateful to participants who accepted to be part of the study and to the technical staff of the Animal Ecology Laboratory for their co-operation to make this work successful.
Mpoame designed and supervised the work, and corrected the manuscript for publication. Payne co-supervised the study, gave lectures in schools and in the lake community to get their consent to partake in the study, also involved in the laboratory processing of specimens. Fusi-Ngwa participated in study design and wrote the manuscript for publication. Ndambi spent 100% of her time on the work, which formed part of her research to obtain a M.Sc. degree in Animal Biology. All authors approved the final manuscript.
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Catherine K Fusi-Ngwa
Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 67 Dschang, West Region
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]