malaria in afghan refugees in pakistan

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TRANSACT~NS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE (1988) 82, 44-47

Malaria in Afghan refugees in Pakistan

Mohanmad Suleman Zoology Department, University of Peshawar, Pakistan

Abstract Prevalence of malaria in Afghan refugees in Pakis-

tan is higher than in the local population. Malaria control officials in Pakistan hypothesized that Afghan refugees have brought a heavy load of malaria infections with them from Afghanistan, causing a serious setback to the malaria control programme in Pakistan. The purpose of this study was to test this hypothesis, because it is important regarding the selection of appropriate strategy for malaria control. The proposed hypothesis is rejected because of the following evidence against it: (i) a comparison of age-specific parasite rates of malaria in Afghan refugees and a nearby local population at Karachi indicated that Afghan refugees were susceptible to malaria even in later age-groups, while infections in the local population were limited to younger age- SZOUDS: (ii) a comnarison of enidemiological trends of &&a ih ‘Afghan-refugees and the local-population in the North-West Frontier Province from 1979 to 1986 demonstrated that the rate of increase in the prevalence of malaria over the years was much higher in Afghan refugees than in the local population, a manifestation of low herd immunity in Afghan refugees. The most plausible alternate hypothesis is that Afghan refugees, being more susceptible, were at high risk of malaria infection in Pakistan rather than that they brought a high infection load with them from Afghanistan. Therefore, malaria control in Afghan refugee camps in Pakistan should be primarily based on preventive, rather than curative, measures.

About 3 million Afghans have migrated to Pakistan since 1978. nearlv one-fifth of Afghan’s oonulation (UNICEF,’ 1984): A mass infkut of<efugees began in 1979 as a result of th Russian invasion of Afghanistan, and thousands are still coming into Pakistan each month. The refugees are lodged in 317 camps in the North-West Frontier Province (NWFP) and its adja- cent tribal areas, Baluchistan and Punjab. There are 245 camps in NWFP, 60 in Baluchistan and 12 in Punjab with refugee populations of 2-2 million, 580 000 and 125 000, respectively. This is the reg- istered population; about 300 000 refugees over and above these are estimated to be living in different parts of Pakistan. Most of their shelters are huts built by the refugees themselves and the rest are tents. They are free to come and go from camps, find employment, graze their animals, and operate a variety of business.

Almost all camps are provided with basic health units or sub-health units which tend to be understaf- fed and can hardly cope with the high incidence of everything from diarrhoeal diseases to tuberculosis (UNICEF, 1984). A number of national and intema- tional agencies, both governmental and voluntary, are

trying to provide health services to the refugees, but they are working individually without any effective coordination, and practically all are focusing on short-term emergency-type curative medicine.

Malaria, a major health problem in Pakistan, is more prevalent in Afghan refugees than in the local population. It is important to understand how refugees have affected the epidemiology of malaria and vice versa; and more specifically why malaria is more prevalent amongst the refugees than in the local population, before considering the selection of anpropriate control measures. ^ SI~~MONDS & HUSSAIN (1986) proposed that the

hieh malaria rate in the refugees is “because of(i) the -- endemic areas from which they come and (ii) disease prevalence in areas where they are accommodated”. Such a generalized conclusion does not help in understanding the dynamics of the problem. Malaria control officials in Pakistan hypothesized that Afghan refugees have brought a heavy load of malaria infections with them (DMC, X985), which would indicate heavy reliance on therapeutic treatment of malaria cases as a strategy for malaria control in Afghan refugees.

The objective of this study was to test this hypothesis, with the help of appropriate epidemiological data, against the alternative hypothesis that Afghan refugees, being more susceptible at the time of migration, were at a high risk of malaria infection in Pakistan. If the alternate hypothesis is true, then the current strategy for malaria control has to be revised with top priority given to preventive measures.

Materials and Methods Comparison of age specific prevalence

Comparative data on age-specific prevalence of malaria in Afghan refugees and the local population were obtained by a cross-sectional sample survey in the two population groups living side by side in a peri-urban community at Karachi in September, 1981. The survey was conducted in the area of Hassan Colony (Bara Market) located along the super-high- way near the Liyari River Bridge in the north-east of old Karachi city. The local District Health and Malaria Control officials indicated the area to be highly malarious with no vector control activity for a long time. A year-old Afghan refugee tent village was situated close to the Hassan Colony where a Pathan population had been living in semilpucka houses for about 10 years.

Households of refugees and local people were enumerated with the help of local guides. There were 194 families of refugees from different parts of Afghanistan (98 Persian speaking; 96 Turkish speaking) and 281 local families in the study area. Systematic sampling was followed in the local popula-

tion, surveying every 9th or 10th household on the list. Cluster sampling was relied on for Afghan refugees, since a simple random or systematic sampling design was difhcult to follow partly due to the cultural/lingual problem and partly due to the fact that closely related families were clustered within a common hedge around their tents. Each family in the sample was censused by age and sex, and finger-prick blood smears (thick and thin) were taken from all the consenting members. The sample included 35 families of refugees (228 oersons) and 31 families of the local populition (298 -persons), of whom 183 refugees and 213 locals gave blood smears. Blood smears were stained with Giemsa followina standard nrocedures. Screening was done by expe;enced technicians, at least 100 microsconic fields from a thick film beine checked before a &de was declared negative; those found to have malaria were given standard chloro- quine treatment.

Compa?ison of trends Secondary data from the North-West Frontier

Province (where most of the Afghan refugees are settled) were used for comparison of malaria trends in Afghan refugees and the local population. Annual estimates of malaria prevalence in the two population groups for.the period 1979-1986 were obtained from She provincial offices of the Malaria Control Depart- ment and the Project Directorate of Health for Afghan refugees. For analysis of trends, secondary data pertaining to crude prevalence of malaria were relied on since age-specific records were not available. Prevalence estimates for 1986 for both the populations are based on data for the first 7 months (January to July) only; all the remaining estimates are based on data pooled over all 12 months of a year.

Prevalence data for the local population throughout the period 1979-1986 and for Afghan reugees from 1979 through 1982 are primarily based on active case detection (where a malaria worker goes into a community and takes blood smears from suspected malaria cases) with minor contributions from passive case detection (where blood smears are made from suspected malaria cases among patients visiting a health centre or a hospital). Prevalence estimates for Afghan refugees from 1983 onwards are exclusively based on passive case detection. This change in

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surveillance procedure among Afghan refugees re- sulted from shift&r the resnonsibilitv for malaria control in refugee &nips from the M-alaria Control Detxutment to the Proiect Directorate of Health for Afghan refugees. Thus ‘the prevalence data in the two population groups from 1983 onwards are not exactly comparable; however, taken along with the pre-1983 data, they provide useful information for comparing trends over the years.

Results and Discussion Comparison of age sDeciiic tievalence

Comparative data’ on age specific prevalence of malaria (Plamwdium falciparum and P. vivax combined) in Afghan refugees and a nearbv local nonulation at Karachi are-set out in Table 1. -Patent narasitaemia was detected in 24 refugees (21 P. vivax. !4 P. falciparum) from 183 examined, and in 16 local people (9 P. vivax, 7 P. falcipafum) from a sample of 213. Since prevalence of malaria did not differ with sex in either group (refugees: M = 12/85, F = 12/98, x* = 0.14, P>O*5; local eople: M = 91103, F = 71 110, x*=0-43, P>O-25), the data were pooled for both sexes. The overall crude prevalence of malaria in the two population groups (Afghan refugees = 13.11%; local people = 7.51%) did not differ significantly (x2 = 3.4; P>@O5), because of the difference in age structure of the two samples; comparison of age- adjusted rates (refugees = 14.0%; local people = 6.43%) revealed that malaria was more prevalent in Afghan refugees than in the local nonulation (r* = 12.38: P<O*OOl). In situations like & a comparison based on crude rates could be misleading.

The data clearly demonstrate that prevalence of malaria in the two populations did not differ significantly in younger age-groups (below 20 years), but showed a highly significant difference in later age- groups (above age 20), a manifestation of a high level of immunity in the older local age-groups; whereas in Afghan refugees malaria infections were quite prevalent in all age groups up to age 60, a manifestation of a low level of immunity in the older refugee age-groups.

Immunity against malaria increases with age as a result of repeated infections in endemic areas; as it is partial and short-term, older age-groups in a persis- tently endemic area exhibit low levels of patent

Table l-Comparison of age-specific prevalence of malaria (P. tiwax aad P. fakiporum combined) in Afghan refugees aad a nearby local population at Karachi, September, 1981

Afghan refugees

Age Number Number Prevalence Nlllllber (Ye& examined positive W) examined

109 5 i 20-o 13.8 5 :i zt 10 - 19

z 2

21.7

:: : :; ;: 20.0 9.5 30 14 kz : :; :; : ;:; 9

60+ 15 0 0.0 1:

Total 183 24 13.11 213

ns = difference not signi6cant; * = difference significant (P<O.Ol)

Local population

NNumber Prevalence positive w

1: 11.2 0.0

?I

12.8

8:; : ;:;

i 0.0

16 7.51

x2

0.22 1.11 ns ns o-85 ns

7.7a*

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Table mmparative prevalence of malaria (P. vivax and P. fakiparum combined) in Afghan refugees and local population in NWFP for the period 19794%

YfSI Total

examined

Afghan refugees Local population

NUltlbW Prevalence Total NUttltXt Prevalence oositive (%) examined uositive (%)

~ I

1979 12156 235 I-9 583824 1815 1980 52464 2562 612580 1982 8:;

1981 177537 11255 2:; 601508 3987 1982 268083 18087 6.8 603602 4437 8:; 1983 51843 4761 9.2 569819 5357 0.9

1984 131615 20808 15.8 667188 9558 1985 183725 40820 22.2 488490 17111 ::; 1986 114470 27326 29.1 252561 12661 5.0 (Jan. to July)

Source: Provincial office of Malaria Control Department and Project Directorate of Health for Afghan refugees NWFP.

Years: 1979 80 81 82 83 84 85 86 X: 01 2 3 4 5 6 7

Fig. Trends of malaria in Afghan refugees and local population in NWFF over the years 197946. Broken lines are fitted regression lines.

Afghan refugees (upper lines): y = 0.206 + 3.162~; bl # 0 (P<O+Ol). Local population (lower lines): y = -0527 + 0.613~; b2 f 0 (P<WOl).

parasitaemia (both in terms of prevalence and parasite density) . Thus a high parasite rate in younger age-groups accompanied by a low prevalence in older age-groups, as seen among the local population in this study, indicates high malaria transmission in the area. It is rather unusual that not a single case of patent parasitaemia was detected in older age-groups of the local population in the present study, probably due to the small sample size. This interpretation is based on the results of a more comprehensive study of a large sample of the local population in Lahore area (SULE- MAN, 1985), in which a strong inverse relationship was noted between age-specific parasite rates and antibodies detected by indirect immunofluorescence.

The age-specific prevalence of malaria in Afghan refugees (Table 1) indicates that they were susceptible to malaria even in later age-groups. A similar pattern of high parasite rates of malaria in all age-groups (up

to age 60) of Afghan refugees was noted by SHAH (1986) in Afghan refugee camps in Haxara district, NWFP. The logical interpretation for such a pattern of age-specific prevalence is that Afghan refugees had little experience of malaria and therefore only a low level of herd immunity before migrating to Pakistan, and faced a high risk of malaria infection in Pakistan. Reviewing the old annual reports (1960s to 1970s) of the WHO Regional Director of the Eastern Mediterranean Region shows that, on average, Pakis- tan has always been much more malarious than Afghanistan. Thus it is not surprising that refugees migrating from Afghanistan were faced with a high risk of malaria in Pakistan.

Comparison of trends Comparative epidemiological data on malaria based

on annual estimates of crude parasite rates in Afghan refugees and local population in NWFP, over the years 1979-1986, are shown in Table 2 and plotted in the Figure. A simple regression model was applied to the prevalence data, taking number of years after 1979 as fixed variable (x) and annual prevalence records as dependent variable 0, to estimate the average rate of change in prevalence of malaria in the two populations. Regression slopes in both of the data sets were significantly higher than zero (refugees: bi=3.16, P<O*OOl; local people: br=0.61, P<O*Ol), indicating that prevalence of malaria has been increasing in both populations almost linearly over the years. Compari- son of the slopes revealed a significant difference (bi # br, P<O-OOl), indicating that the rate of increase has been significantly different in the two populations; the average rate of increase for Afghan refugees (3.16%) was about 5 times higher than that for the local population (0.61%).

Difference in the parasites rates of the two populations was minimal in 1979 when the refugees had had only a relative short stay in Pakistan. All the refugees examined in 1979 were not necessarily fresh immig- rants, since, according to official records, there were already 109 000 Afghan refugees in Pakistan by April 1978 and 193 000 by September 1979. They may have contracted malaria after migrating to Pakistan. There- fore the higher prevalence of malaria in Afghan refugees compared to the local population in the first year of surveillance, 1979, does not prove that the refugees entered Pakistan carrying a heavy load of malarial parasites with them. On the other hand, the

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Afghanistan, indicates that preventive measures (vector control and chemoprophylaxis) must be the mainstay of malaria control strategy in Afghan refugee camps in Pakistan. Acknowledgements

The malaria survey at Karachi was supported by the Pakistan Medical Research Centre, Lahore. Drs Ihsanul- Haq and M. Munir helped during the survey. Technical assistance of Messrs Mian Bashir and Meher Din is gratefully acknowledged. Historical data on prevalence of malaria in the local population and Afghan refugees in NWFP was made accessible through the courtesy of the officials of the Malaria Control Department and Project Directorate of Health for Afghan refugees.

Refereoces DMC (1985). Annual Report 1984-1985. Directorate of

Malaria Control, Government of Pakistan Ministry of Health, Iskunabad. Mimeographed? 32 pp.

Shah, S . A. (1986). Zncidence of malaria m Afghan Refugees in Hazara NWFP (Pakistan). M.Sc. thesis. Zoology De- partment, University of Peshawar, 66 pp.

Simmond, S. & Hussain, M. (1986). Assignment Report - the Health of Afghan Refugees in PakistanJuly-August, 1985. World Health Organization WHO-EM/PHC!39, WHO Eastern Mediterranean Office, Alexandria, Egypt.

Suleman, M. (1985). Epidemiology of malaria in Punjab, Pakistan: a case stuay in a rural community near Lahore. Ph.D. dissertation. University of Hawaii, 319 pp. (Copies available from University Microfilms Intema- tional.)

UNICEF (1984). UNICEF Assistance w Afghan Refugees in Pakistan. UNICEF, Islamabad in collaboration with UNICEF, Peshawar, 22 pp.

Accepted for publication 2 June 1987

fact that prevalence of malaria in Afghan refugees has been increasina over the vears, at a rate much higher than in the loca population, clearly demonstrates-that thev faced a hither risk of malaria infection in Paliistan. -

If it is assumed that Afghan refugees have aggra- vated the malaria problem in Pakistan by bringing infections with them, one would expect a high prevalence of malaria -in the local population so& after the bulk of refuaees arrived in Pakistan. Mass influx of refugees occt&d in 1980, but prevalence of malaria in the local population remained largely unchanged during 1980-1984. The rise in prevalence of malaria in the local population after 1984 could be due to the well established phenomenon of long-term periodicity of malaria epidemics in this area or to the epidemiological impact-of large scale immigration of a susceptible refugee population, or both. The sharp rise in the prevalence of malaria in Afghan refugees after 1982 mav have been ~artlv due to the chanee in surveillance system (see ‘niaterials and Methods’yand partly to an aggravating malaria situation in recent years.

The prevalence estimates for 1986 shown in Table 2 and Fig. 1 are based on data collected UD to the month of July only. The annual estimates-for 1986 are expected to be higher than these figures indicate because peak transmission of malaria in Pakistan starts in -August-September (SULEMAN, 1985).

The conclusion that the Afghan refugees faced a high risk of malaria infection in Pakistan, rather than bringing a high infection load with them from

malaria in afghan refugees in pakistan

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