Malaria in Quarry Mining Communities*

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1 Malaria in Quarry Mining Communities* Juan M. Lopez, Robert A. Sadang, Mario B. Brizuela, Nicolas B. Bautista, Mark E. White and Manuel M. Dayrit (*From the Field Epidemiology Training Program, Philippines) ABSTRACT A case-control study was done to determine the risk factors of malaria in San lldefonso Bulacan. A nonrandom survey was employed for case finding. A case was defined as a person with positive blood smear for malaria. A control was defined as a person from the same neighborhood with negative malaria smear. A matched case-control analysis was performed. Three hundred seventy nine people were examined from Sitios Bangka-bangka, Sinambalan and Vega Quarry (50% of the total combined population). Fifty five were positive for malarial parasite (Slide Positivity Rate (SPR) 15%). Plasmodiurn falciparum was identified in 38 (69%) cases and P. vivax in 17 (31%). The age range was from 0.6 to 46 years (mean 21 years). Forty (73%) were males. Twenty seven (49%) were quarry workers. Two risk factors were associated with malaria, sleeping in the job site (OR = 6, PO.03) and the number of household members (T-test P-value 0.03). All cases were treated with chloroquine phosphate and primaquin using the standard regimen of the Department of Health. Residual spraying of houses with insecticide was done. Coordination and support from the local officials, teachers and quarry managers was obtained in the control of malaria in the areas [Phil J Microbiol Infect Dis 1991; 20(1):6-12] Key Words: malaria, epidemiology, treatment, prevention INTRODUCTION On November 29, 1989, the San Lazaro Surveillance Site reported six cases of malaria from Narra, San Ildefonso, Bulacan. A case-control study was carried out to determine the risk factors associated with malaria in San Ildefonso. San Ildefonso was one of the 5 malaria endemic municipalities of Bulacan. It had 6 reported hypoendemic localities with a total population of 2,646 and an annual parasitic incidence of 19.8 per 1,000 population. The study areas were located in rolling hills surrounded by shrubs and vegetations in the southernmost part of Bulacan. These were 18 kilometers from the Rural Health Unit and were accessible through a rough road. Regular transportation was not available in these areas. The houses were within 500 meters from a clean, slow-flowing and shady stream. The total population of the three sitios was 728. Majority of the residents were migrants and employed as laborers of the nine marble mining companies. METHODOLOGY Records review: We reviewed the records of the Malaria Control Service of Bulacan, San Miguel District Hospital and the Pinaod Rural Health Unit. Case finding We set up our examination stations at Sitio Bangka-bangka, a newly established sitio, Sitio Sinambalan and Sitio Vega Quarry. Sinambalan and Bangka-bangka are sitios of Barangay Narra while Vega Quarry is a sitio of Barangay Alagao. (See Figure 2) They were under the catchment of Pinaod Rural Health Unit. A non-random survey was used for case finding. The

2 team examined blood smears for malaria parasite from those people who came for blood examination. The case and controls were interviewed using the same prepared open and closed ended questionnaire. For young children, the questions were answered by their mothers or fathers. Questions were asked about: occupation, duration of residence, type of house, presence of animals, use of bed nets, travel in the forest and knowledge and practice on the cause, transmission and prevention of malaria. This questionnaire is available upon request. A matched case-control study was designed and conducted from December 11-16, The eases and controls were matched by same age ( years), same sex and same sitio. A case was defined as person with positive blood smear for malaria. A control was defined as person from the same neighbor-hood with negative malarial smear. RESULT Survey Malaria cases began increasing in November 1989 (Figure 1). In the survey, 379 people were examined (50% of the population). Fifty-five were found positive, giving a Slide Positivity Rate of 58% (Table 1). Plasmodium falciparum was identified in 38 (69%) cases and P. vivax in 17 (31%). Bangka-bangka, the newly established sitio had the highest slide positivity rate (81%) (Table 1). Malaria San Ildefonso, B ulacan Nov Dec. 14, 1989 ( N = 32 )* *Excludes 23 Afebrile Cases November December

3 Table 1. Malaria Positivity Rate by Sitio, San Ildefonso, Bulacan, December 11-16, 1989 Sitio Population No. Examined No. (+) % (+) Bangka-bangka Sinambalan Vega Quarry Total The age of cases ranged from 6 months to 46 years. The mean age was 21 years. All ages were affected with the highest attack rate (19%) noted in ages between years (Table 2). Forty (73%) were males and 15 (27%) were females. Twenty seven (49%) were quarry workers. Table 2. Prevalence of Malaria by Age, San Ildefonso, Bulacan, December 11-16, 1989 Age Population* No. Cases Attack Rate/ and above *Based from the calculated age distribution of Barangay Pinaod, Rural Health Center Record Records review Review of 1988 Malaria Control Programs records of San Ildefonso revealed a total malaria case finding of 553. Thirty five were positive giving a slide positivity rate of 6.3%. Case-control study Table 3 shows the variables associated with the occurrence and transmission of malaria. Two risk factors were associated with malaria: sleeping in the site of job and the number of household members. Two factors, travel in the forest and presence of animal were protective. The majority (75 or 68%) of the respondents did not know the cause of malaria, however, 37 (34%) knew how it was transmitted. Ninety-seven (88%) believed that malaria can be prevented and 92 (84%) said it can be cured. Only 16 (14%) were using bed nets as their personal prevention. Sixteen (14%) of the respondents got their information on malaria from the Rural Health Unit (RHU). Fifty-four (49%) sought consultation and treatment at private practitioners and only 16 (14%) at the RHU. Everyone claimed that no DDT house spraying was done in the past 6 months. Geographical reconnaissance Environmental survey revealed a clean, slow-flowing shady stream with stone and lush vegetations along the banks. However, no entomological survey was done by the team. Interviews with RHU personnel The rural health unit claimed that they had not been covering Sitio Bangka-bangka and minimal services were rendered to other sitios because of refusal of the quarry managers. There

4 were no Barangay Health Workers (BHW) in Sitio Bangka-bangka and Vega Quarry. In Sinambalan the BHW's were inactive. Table 3a. Risk Factors Associated with Malaria Number** Variables Cases Control O.R. 95%CI p-value Use of Bed nets Never Regular Irregular Travel in the forest Yes No * Sleep in the site of job Yes 10 2 No * Home construction Semi-permanent 4 1 Temporary *** Presence of animals Yes No *Statistically significant **Chi-Square Test Yates corrected ***Fischer's Exact Test Table 3b. Risk Factors of Malaria Mean** Variable Cases Controls p-value Number of household members * Duration of residence *Statistically significant. **ANOVA (T-Test) The variances are homogenous with 95% confidence. Data are normally distributed. DISCUSSION There was a malaria epidemic in the three sitios involving majority of the marble laborers and their families, Bangka-bangka, a sitio existing only for 2 years had the highest number of cases. It was the area where the 6 cases admitted at San Lazaro Hospital came from. Factors which might have potentiated the abrupt rise of cases in this area included being near the hypoendemic localities about one kilometer away from Sinambalan, the oldest existing hypoendemic sitio; the presence of the stream, a potential breeding place for Anopheles vector; the introduction of non-immunes, the migrant workers; and the continuous movement and transfer of the old residents from one quarry to the others, the probable infective reservoirs. 1 There was a higher infection rate in the ages between years as represented by majority of the quarry workers. However, 29% of the cases were children below 10 years. Therefore, it is likely that indoor and outdoor transmission occurred in these 3 sitios. Workers who slept on the job site were more likely to acquire malaria than those who did not. The reason might be that workers did not use bed nets when they slept at night. The number of household members in the family was also found to be significant. Those coming from a bigger household were more likely to acquire malaria. The presence of an infective reservoir is important in the genesis of malaria. More family members therefore increased the infective reservoir resulting in a higher risk of acquiring malaria. 2 Travel in the forest was a protective factor. This study however failed to ask other information regarding travel in the forest such as: time of travel, duration of

5 stay in the forest, and. the use of bed nets and other protective devices while staying in the forest so it was difficult to evaluate why forest travel was protective. 3 Zooprophylaxis is a technique in which animals are used to divert mosquitoes seeking a blood meat away from man. 4 Inquiry on the presence of big animals such as pigs, carabaos and cows were done in this study. It was found out that their presence was a protective factor. However, man and animal bait experiments were not done to compare the preference host the mosquito present.

6 The use of bed nets was not a protective factor. However, important factors affecting mosquito nets were not examined in this study, such as crowded housing conditions resulting in some person sleeping out of doors, condition of the nets and number of persons using one net. 5 The outcome of other risk factors were not significant probably due to small sample size. The respondents' knowledge in the epidemiology of malaria was wanting. The majority did not know the cause of malaria, how it was transmitted and how it was prevented. Of concern in this study was the lack of cooperation by the quarry managers with the local RHU authorities. It was claimed that company physicians were in charge of their employees. Workers however stated that no malarial smears were done. CONCLUSIONS 1. There was a malaria outbreak in the 3 sitios involving the marble laborers and their families. 2. There was poor knowledge, attitude and practice of the respondents on malaria. 3. Minimal malaria control program service was rendered to the 3 sitios because of unavailability of transport vehicles, lack of barangay health workers and the refusal of the quarry managers to cooperate with the DOH personnel.

7 Actions Taken 1. Residual spraying of the houses with insecticides was done by the team from the malaria control service. 2. Health education about the cause, transmission and prevention of malaria was done. 3. Coordination and support from the local officials, teachers, and quarry managers in the control of malaria in the areas, were sought for. Recommendations 1. A representative from each quarry should be trained on blood smearing and communication skill. 2. Strengthening health education with emphasis on the cause, transmission and prevention of malaria. 3. Training of BHW's to assist the District Health Office in malaria surveillance. 4. Continuous surveillance of migrant workers in the areas in coordination with the quarry managers. 5. Entomological survey must be done by the regional entomologist to identify specific malaria vector. 6. Follow-up of the cases after 6 months to assess the impact of the control measures done. REFERENCES 1. Renald AS. Population movement, socio-economic behavio r and the transmission of malaria. SEA J Trop Med 1986; 17(3): Bruce-Cwatt LJ. Essential Malariology, Second Edition, William Heinemann Medical Books, London, Prothero RM. Disease and mobility: A neglected factor in epidemiology. Int J Epidemiol 1977; 6: Schultz GW. Animal influence on man-biting rats at a malarious site in Palawan, Philippines. SEA J Trop Med 1989; 20(1): Butraporn P. Social, behavioral, housing factors and their interactive effects associated with malaria occurrence in East Thailand. SEA J Trop Med 1986; 17(3):