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Indian Journal of Community Medicine

Parasitiological observations on prevalance seasonailty & transmission of Malaria among tribals of Surguja district

Author(s): Gyan Chand, R.S. Tiwary

Vol. 26, No. 4 (2001-10 - 2001-12)

Regional Medical Research Centre for Tribals (I.C.M.R.), Nagpur Road, Post-Garha, Jabalpur - 482003


Research question: What is the prevalence and seasonality of malaria among tribals.

Objective: To determine the prevalence of Malaria and its seasonality in two tribes.

Setting: Kodaku and Pando tribe of Sarguja district.

Study design: Cross-sectional.

Study variables: Slide positivity rate, slide falciparum rate and parasite density per micro litre of blood.

Statistical analysis: Proportions Chi-square test, students t-test.

Results and conclusion: 5023 slides were collected from both the tribes and 636 were positive for malaria parasite. SPR and SFR were 12.6 and 10.45 with pf% as 82.5%. SPR and SFR in Pando and Kodaku tribe was 11.0 and 9.0 and 15.9 and 13.3 respectively. Results indicate that malaria is endemic in these tribes and areas. Transmission is seasonal with peak transmission in the month of November and December. Parasite density was less in afebrile infected persons. Detailed longitudinal study is required to understand the aetiology of disease.

Keywords : Pando tribe, Kodaku tribe, P.falciparum, Slide positivity rate.


Among vector born diseases, malaria poses a major public health problem. The disease is more severe among the tribals. Though tribals represent only about 8% of the country's population, they account for 30% of all the malaria cases, more than 60% of the P.falciparum cases and as much as 50% of the mortality associated with malaria1. Containment of transmission of malaria in tribals is extremely difficult because of difficult terrain, poor communication, witchcrafts and superstitions prevailing in this underprivileged community2,3.

Madhya Pradesh (undivided) was the largest of all the states, had 46 tribal groups living in diversified geo-climatic atmosphere4. Together these groups constituted about 24% of the state's population as well as similar proportion of country's tribal population. The state contributes about 16% of total malaria cases of the country5. Tribe-wise only a few studies are available. The Regional Medical Research Centre carried out malaria surveys in Pando and Kodaku tribes of Surguja district - an endemic district for malaria6 between Dec., 1996 and Nov., 1999. In all, 5 mass blood surveys were carried out. The aim of the survey was to determine the prevalence of malaria, its magnitude and parasite density of P.falciparum in febrile and afebrile cases since it is reported that in endemic region semi-immune children carry parasitaemia up to 12,000/*l without febrile illness7.

Material and Methods:

The Area: District Surguja is the second largest district of undivided Madhya Pradesh (Now in Chhattisgarh) spread over 22,337 and consisting of 11 tehsils and 24 blocks. On the east this district forms boundary with the state of Bihar. Average rainfall is about 1150mm/annum. The area is hilly and covered under Sal (Shorea robusta) and Mahuva (Madhuca longifolia) forests. River Mahi is the life line of the district. Paddy and groundnut are the main crops of the area. Agriculture is rainfed and irrigation facilities are almost absent.

The Tribe: The tribe Pando is grouped with Bharias, Bhumias and Bhumihars tribe of M.P. They consider themselves as the successors of Pandavas of Mahabharat era. They live far away from the social mainstream either deep in the forest or near forest on hilltop and make their houses near permanent source of water i.e. river stream etc. Houses are kutcha, in scattered fashion with no concept of sanitation and sewerage. Literacy is low. Dependency for livelihood are based on picking of mahuva flowers and tendu leaves, collection of firewood, agricultural labour and labour in relief works. Wells, nallahs and Jhirias (seepage water) are the main sources of drinking water. Electricity connections are not there except in Pando Nagar, a colony settled by Tribal Welfare Department near Ambikapur town.

Kodakus consider themselves as the successors of Kaurvas of Mahabharat era. Living style and culture of Kodakus are similar as that of Pandos except that Kodakus live in plains and are influenced by Christianity. They send their children to Church for study. Churches also provide them medicines in case of emergency and minor ailments.

Mass Blood Survey: Mass blood surveys (MBS) were carried out in selected villages as per the list provided by state tribal department. Among Pando tribe MBS was carried out in Dec.96 (22 villages), March 97 (15 villages) and September 97 (26 villages). Besides MBS active fever survey was also carried out in 10 more villages during Dec. 96. Among Kodaku tribe MBS was carried out in July 1999 (22 villages) and November/December 99 (18 villages).

Parasite density: Parasite density was estimated in febrile and cases without symptoms of illness. Only P.falciparum density was determined because of its predominance (80%). The parasite density was determined for peak transmission season when the positivity was high, to compare the parasitaemia between adults and children and between febrile and afebrile carriers. The parasite density per mm3 blood was determined by multiplying mean parasite number per thick film with 500 assuming the average amount of each thick film as 0.002*8,9. This method is more reliable under field conditions than any other method10.

Results & Discussion:

Table I: Results of mass blood survey in Pando and Kodaku tribes of Surguja district.

Month BSC SPR from prev. surv. SFR (from prev. surv.) pf% Afebrile Afebrile pf gameto%
Dec-96 1142 20.9 18.1 86.6 83.5 27.7
Mar-97 1130 2.56 (-83.77%) 1.6 (-91.2%) 62 83.3 33.3
Sep-97 1069 9.35 (+365.2%) 7.1 (+446.5%) 76 81.57 3.2
Total 3341 11 9 81.8 83.0 22.0
Jul-99 858 4.5 4.1 92.3 27.7 0
Nov-99 824 27.8 (+617.7%) 22.8 (+556%) 82.0 30.85 20.6
Total 1682 15.9 13.3 83.5 30.35 17.6
Grand Total 5023 12.66 10.45 82.50 60.5 21.0

BSC- Blood slide collection, SPR- Slide positivity rate, SFR- Slide falciparum rate.

A total of 5,023 blood slides were collected from both the tribes in all the five surveys and 636 slides were found positive for malaria (Slide positivity rate - 12.66%). Among positive slides 525 were of P.falciparum (slide falciparum rate - 10.45%). Among Pandos slide positivity rate (SPR) was 11.0%. Highest SPR was observed during Dec.96 (20.92%) - the winter season when P.falciparum constituted 86.6%. Three months later i.e. during March 97, (onset of summer) slide positivity rate was 2.56% i.e. it was reduced by 83.77%. Similarly, SFR was reduced from 18.12% to 1.59% during the same period. The reduction was highly significant (Z=14.25 and 13.8 respectively, p<0.05). The falciparum percentage among malaria positive cases was also reduced from 86.6% to 62%. Further, an increase was observed in SPR and SFR during the month of September. The increase was found statistically significant (Z=6.74 and 6.34 respectively, p<0.05). During the month there was an increase in falciparum percentage from 62 to 76. Among P.falciparum cases 24.25% were having gametocyte. Maximum gametocyte carriers were found in the month of March (33%) followed by December (27%) and September (13.1%). Among P.falciparum infections 83% of the cases did not report any symptoms of clinical illness. The proportions were almost equal in all the 3 surveys. Overall 22% symptomless P.falciparum infections had gametocytaemia. The percentage was highest in March (33.33%) and lowest in September (3.2%).

Among Kodaku tribe overall SPR and SFR were 15.9% and 13.3% respectively. The indices were low in July with magnitude of 4.5% and 4.1% respectively. There was an increase in malaria cases from July to November by more than six times in SPR and five times in SFR (Z=13.59 and 11.6 respectively, p<0.05). During July, P.falciparum constituted 92.3% (36 cases) of all the malaria cases of which 10 cases (27.7%) did not report any symptoms of febrile illness. In November P.falciparum percentage was reduced to 82% of which 58 cases (30.8%) did not report any symptom of illness.

Table II: Results of active fever survey Dec. 1999.

  B.S. Collected +ve SPR Pf (Gametocyte) SFR
ACD (10 Villages) 92 39 42.4 35(9) 38.0
Among mass blood survey 77 38 49.3 34(9) 44.1
Total 169 77 45.56 69(18) 40.82

In 10 villages out of 169 fever cases 77 were having malaria. Out of these sixty nine had P.falciparum and among them 18 were having gametocytes.

Table III: Age group wise break-up of blood slide collection and positivity.

Age Group
<15 years 15+ years Chi Square
% +ve pf
Dec. 476 27.5 23.73 98 (86.8) 666 16.2 14.11 75 (79.78) 21.42 17.33
Mar. 491 4.07 2.03 7 (70) 639 1.4 1.25 8 (100) 7.88 1.09
Sep. 411 14.11 11.19 41 (89.1) 658 6.38 4.55 21 (70) 17.82 16.85
Total 1378 15.16 12.66 146 (86.4) 1963 8.09 6.72 104 (79) 41.25 30.3
Jul. 391 5.37 4.85 6 (31.5) 467 3.85 3.64 4 (23.5) 1.13 0.8
Nov. 320 33.4 28.75 27 (29.3) 504 24.26 19.04 31 (32.3) 8.31 9
Total 711 18.0 15.6 33 (29.7) 971 14.41 11.6 35 (31) 3.93 5.61
G.Total 2089 16.13 13.4 179 (63.9) 2934 11.9 8.4 139 (46.4)    

Overall malaria and P.falciparum infection were more among children than the adults and the difference was statistically significant for both the tribes.

Table IV: Parasite (asexual) count # among P. Falciparum positive cases in Pando (Dec. 1996) and Kodaku (Dec. 1999) tribes, district Surguja.

Tribe Category Indices Age Group Total
<15 yrs. 15+ rs.
Pando Afebrile cases n 46 37 83
Mean P.D. / l 1.5972987* 1.1384082 1.392773
SD 0.701326 0.3285303 0.610522
  Febrile cases n 15 20 35
Mean P.D. / l 1.531463 1.5389256+ 1.537274
SD 0.6.9585 0.59099342 0.59901
Kodaku Afebrile cases n 21 24 45
Mean P.D. / l 2.08 1.835+++ 1.9511
SD 0.806 0.53 0.6134
  Febrile cases n 55 44 99
Mean P.D. / l 2.768++ 2.319** 2.58***
SD 0.824 0.7728 0.8077

#Count at log10 scale, Mean P.D = Mean parasite density/micro litre, *Significantly higher in <15 years age group t=3.93, p<0.05, **Significantly less in 15+ years age group t=2.79, p<0.05, ***Significantly more in febrile group, t=5.153, p<0.05, +Significantly higher in febrile group t=2.81, p<0.05, ++Significantly more in febrile group t=3.3063, p<0.05, +++Significantly more in febrile group t=3.0427, p<0.05.

The results of parasite count have been summarised in Table IV on log10 scale. Among Pandos tribe there was high parasite density among children of afebrile category. However, in 15+ years age group higher density was observed in febrile cases than the corresponding afebrile group.

Among Kodakus estimated parasite density was significantly higher among febrile cases than the afebrile cases in both the age groups. The parasite density was also more in younger age groups than the adults. However, the difference was insignificant in case of afebrile category. The trend of parasite density among younger age group in Kodaku was reverse to the trend seen in Pandos.

As per National Anti Malaria Programme, presently about 2.4 million cases are annually reported from the country. Average SPR and SFR for M.P. is about 5% and 2%. The Pv and Pf ratio is 60:4012. In the present study reverse trend with predominance of P.falciparum over P.vivax has been observed. Malaria is a local and focal disease influenced by intrinsic and extrinsic factors113. District Surguja enjoys extreme climatic conditions. High SPR and SFR during the winter month of December when temperature comes down to as low as 2-3 C, are explained by the fact that tribals use fire in their houses during night to keep the house warm. This practice makes the microclimate in the house conducive for the metabolic activities and development of parasite in the insect and maintains transmission. The area is covered under thick forest. Such situation provides favourable atmosphere for P.falciparum14. The transmission and incidence of malaria in this district is characterized by seasonal fluctuations. In both the tribes peak transmission was observed after rains. Magnitude of rains, number of rainy days and spells and agricultural pattern are the factors which determine the breeding of vector, its density and longivity. During the rains large pools are formed which are the preferred breeding sites of An.culicifacies. After rains water starts receding and left within low running channels which are the most favourable breeding sites for An. fluviatilis. Hence, the transmission continues from July to December by An.culicifacies during monsoon and by An.fluviatilis during post monsoon. In the present study P.falciparum predominated in all the seasons. In the tribal areas increase in P.falciparum proportion has been reported year by year over the last 10 years15. Probably drug resistant strain is prevalent in tribal areas of the state16 which is multiplying unabatedly.

There was high proportion of symptomless P.falciparum infections (which accounted 80% and 30% in two communities). Similar findings were reported earlier from tribal and non-tribal areas during the mass blood surveys17,18. Possibly these P.falciparum infected persons might have suffered mild headache, nausea, chills and fever but were overlooked by the individuals. Further, tribals consumed country made liquor irrespective of age and gender, under the influence of which they did not feel any sufferings. In partially immune population most of the P.falciparum infections present with fever in narrow range of increased temperature between 99 to 100 F19. The fever caused by malaria in most of the cases subsides within 4-5 days in untreated persons20. There is also possibility of prevalence of more than one strain of P.falciparum in the area which may be different in its virulent effect.

Difference of afebrile infection in two communities can be explained by the fact that the Kodakus are influenced by different socio-cultural set up which had direct bearing upon the pattern of transmission and had easy access to anti-malarials than Pandos.

More slide positivity rate and slide falciparum rate among the children indicated that the transmission was indigenous and children were more vulnerable to infections than the adults. Probably some immunity was acquired which protected the adults against the infection.

The time lag between the appearance of trophozoite and crescent on an average is 10 days21. Therefore, less gametocyte carriers observed during July and September expressed that the transmission had just began and it increased and attained peak during the month of February and March.

Most of the crescent carriers were silent. Such cases even with low parasite density were implicated as the main source of P.falciparum infections22. In the present study, only a small proportion of P.falciparum infection had crescents. It is not known whether the gametocyte density was so low to be detected with conventional microscopy or did not have gametocytes. Continuation of asexual form without showing sexual form of P.falciparum has also been reported from another tribal area23.

Regarding parasitaemia, overall density of asexual parasite was higher in febrile cases. Though the difference in Pando tribe was not statistically significant, it seemed that more parasite density was needed for the onset of fever. More parasite density in younger age groups of both the tribes indicated that younger age group was more afflicted and vulnerable to the infection. Probably better immune response of adults protected them against the infection.

More parasite rates, more falciparum rate and more parasitaemia among the younger than the adults stressed upon the urgent need to take up longitudinal studies for better understanding of the etiology and management of disease in the underprivileged section of society and in the tribal areas of the district.


The authors gratefully acknowledge the tough field work being carried out by the staff of Entomology division of the centre. Valuable suggestions provided by Dr. G.D. Pandey, Deputy Director is also gratefully acknowledged.


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