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Table of Contents
RESEARCH ARTICLE
Year : 2021  |  Volume : 58  |  Issue : 4  |  Page : 317-322

Current status of malaria elimination in Koraput district of Odisha, India


1 Indian Council of Medical Research-Vector Control Research Centre, Medical Complex, Indira Nagar, Puducherry, India
2 Chief District Medical Office, Koraput, Govt. of Odisha, India

Date of Submission20-Apr-2020
Date of Acceptance14-Jul-2020
Date of Web Publication25-Mar-2022

Correspondence Address:
Dr. Sudhansu Sekhar Sahu
ICMR-Vector Control Research Centre, Medical Complex, Indira Nagar, Puducherry, 605006
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-9062.325644

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  Abstract 

Background & objectives: After launching of NFME and NSP with wide scale implementation of effective intervention tools during 2017, Odisha State of India observed a drastic reduction of malaria cases (81%) in 2018 and 88.6% in 2019, compared to 2017. The current study analysed the different factors causative for malaria reduction in Koraput district of Odisha State, India.
Methods: The vector density and malaria incidences were assessed from January 2016 to December 2019 and human blood index, bio-efficacy and use rate of LLINs were assessed after distribution of long-lasting insecticidal nets. Results: The use rate of LLINs by the villagers ranged from 93.8% to 100% throughout the year. The mortality of Anopheles jeyporiensis remained 100.0% in both DuraNet and PermaNet LNs. The density of An. fluviatilis after distribution of LLINs reduced from 4.7 to 0.0 whereas, the density of An. culicifacies reduced from 12.2 to 9.3. The HBI of An. fluviatilis and An. culicifacies was 0.006 and 0.005, respectively after distribution of LLINs. The malaria incidences also drop from 14.2 to zero after distribution.
Interpretation & conclusion: A significant reduction in malaria incidences was validated and the possible reasons for the reduction are discussed.

Keywords: Annual parasite incidence; DAMaN; Koraput; Malaria elimination


How to cite this article:
Sahu SS, Thankachy S, Dash S, Panigrahi DK, Kumar A, Swain KK. Current status of malaria elimination in Koraput district of Odisha, India. J Vector Borne Dis 2021;58:317-22

How to cite this URL:
Sahu SS, Thankachy S, Dash S, Panigrahi DK, Kumar A, Swain KK. Current status of malaria elimination in Koraput district of Odisha, India. J Vector Borne Dis [serial online] 2021 [cited 2022 May 19];58:317-22. Available from: https://www.jvbd.org/text.asp?2021/58/4/317/325644




  Introduction Top


The complexity of malaria imposes a major public health problem in India. During 2001, India had reported 2.09 million malaria cases with 1005 deaths[1]. However, the epidemiological situation of malaria showed a decline trend from 2001 to 2015 (1.16 million malaria cases)[1]. This reduction in malaria cases provided a benchmark to the National Vector Borne Disease Control Programme (NVBDCP) of India to envision “Malaria-free India”[2]. In February 2016, the Government of India officially launched National Framework for Malaria Elimination (NFME) which aims to eliminate malaria from the country by 2030 focusing with specific objectives[2]. Under NFME, the NVBDCP of India has prepared a five-year (2017-2022) National Strategic Plan (NSP) for malaria elimination in which the focus is on district based planning, implementation and monitoring[3]. After the launching ofNFME and NSP with wide scale implementation of effective intervention tools, India has recorded 22.4% decline in malaria cases in 2017, 61.5% in 2018 and 69.2% in 2019 compared to 2016[1].

Among the 36 States/Union Territories of India, Odi- sha has been badly affected with high malaria incidences for many decades and added nearly 40% of total malaria cases and 50% of total Plasmodium falciparum cases reported in India up to the year 2017 (Source: NVBDCP, Odisha). The favourable factors like hilly terrain with forest cover, perennial streams, adequate rainfall and high humidity, difficulty in accessing remote and hilly villages and prevalence of efficient Anopheles mosquito vectors have accounted for persistent malaria transmission in 24 tribal districts of Odisha[4],[5]. After implementation of NSP, Odisha state observed a drastic reduction of malaria cases (81%) in 2018 and 88.6% in 2019, compared to 2017[1]. The two new interventions introduced in malaria endemic areas of Odisha state during mid 2017 included universal coverage of long-lasting insecticidal nets (LLINs) (11.13 million) in 17 high endemic districts and ‘‘Durga-maAnchalare Malaria Nirakaran’' (elimination of malaria in inaccessible regions) (DAMaN)[5].

Koraput, a tribal district of southern region of Odisha state, is highly endemic to falciparum malaria since many years[6]. The API of malaria in the district was 25.9 in 2014, 24.5 in 2015, 29.5 in 2016 and 26.5 in 2017 (Source: Office of the Chief District Medical Officer, Koraput). In 2017, the district also received free distribution of LLINs, covering total population and DAMaN was implemented in high endemic areas. Similar to the reduction in malaria cases observed in the State as well as in the country, the district has observed 88.3% decline in malaria incidences during 2019 (4609 malaria cases reported during 2019 (API: 3.1)) compared to 39,173 in 2017 (API: 26.4) after implementation of NFME plan in the district (Source: Office of the Chief District Medical Officer, Koraput).

This reduction of malaria incidences recorded by the NVBDCP has not been validated by any other agency. Moreover, to authenticate this reduction, no supporting information such as the impact of intervention on vector density, HBI, bio-efficacy and use rate of LLINs is available so far. In this manuscript, an attempt has been made to gather evidences on different supporting parameters resulting malaria reduction in Koraput district after implementation of NFME and NSP in mid 2017.


  Material & Methods Top


Study area

The study was conducted in Koraput district (latitude 180 82’ N and longitude 820 72’ E) situated in the southern part of Odisha state. The district has 14 Community Health Centres (CHCs), 308 sub centres (SCs) and 4352 villages including hamlets[7]. The population of the district during 2019 was 14.9 lakhs with 51% tribes. Malaria transmission is intense and perennial[8]. The API of the district during 2008-2017 varied from 17.7 (2013) to 36.7 (2010) with 61 deaths due to malaria (Source: Office of the Chief District Medical Officer, Koraput). The district is rich in anopheline fauna. Anopheles fluviatilis and An. culicifacies are the major malaria vectors in the district[9],[10]. An. fluviatilis is susceptible to dichlorodiphenyl-trichloroethane (DDT), malathion and deltamethrin; An. culicifacies is resistant to these insecticides in the district[6].

Atotal of 8, 37,435 LLINs (DuraNet® (alphacypermethrin treated net) and PermaNet 2.0 (deltamethrin treated net) were distributed to entire population (n=14, 76,356) of Koraput district by the NVBDCP during July–August 2017 (Source: Office of the Chief District Medical Officer, Koraput). In addition, indoor residual spraying (IRS) with DDT is being carried out only in identified hot spots of malaria in the district. The NVBDCP has introduced the use of monovalent rapid diagnostic tests (RDTs) since 2002 and bivalent RDTs from 2013 to facilitate early detection of malaria cases. Due to development of resistance of P. falciparum to Chloroquine, the drug was replaced with Artemisinin-based combination therapy (ACT) in 2009 in this district[11].

To focus the malaria control in inaccessible areas, DAMaN programme was introduced during 2017 and 2018 in the district[5]. The objective of DAMaN was to reduce malaria parasite load in the community by diagnosing and treating all malaria infected patients in inaccessible villages of high malaria endemic CHCs by conducting mass blood survey. In this programme, a total of 9387 (asymptomatic: 7580; symptomatic: 1807) malaria cases were treated with anti-malarials during three rounds of DAMaN in 2017 (one round) and 2018 (two rounds) (Source: Office of the Chief District Medical Officer, Koraput).

Assessment of interventions

Coverage of LLINs

Distribution of LLINs was done by the district health department as per the national guidelines, i.e., 1 net per 2 persons[12]. A house-to-house survey was conducted along with NVBDCP staff just after distribution of LLINs in 54 randomly selected villages in Koraput district to know the coverage of LLINs in the community. A structured questionnaire was used as per Roll Back Malaria (RBM) guidelines for determining the coverage of LLIN among the members of the households[13]. The questionnaire had three parts: general information; individual net access and compliance to LLIN use.

Net use rate

The monthly net usage survey was conducted by Accredited Social Health Activist (ASHA) workers and supervised by Indian Council of Medical Research-Vector Control Research Centre (ICMR-VCRC) research team in three randomly selected villages of the district. In each village, the survey was conducted in 20 households selected randomly. The net use rate was assessed by spot check during early morning hours by ASHA workers.

Bio-efficacy of LLINs

Persistent insecticide effect of LLINs was assessed through cone-bioassays[14] at one to two months interval. For carrying out cone bio-assays, two LLINs (one DuraNet and one PermaNet) from one randomly selected village of the district were selected. Since, in the study area, An. fluviatilis was not available in sufficient numbers and An. culicifacies was resistant to synthetic pyrethroids (SPs), cone-bioassays were conducted with An. jeyporiensis mosquitoes, a local malaria vector[15], susceptible to deltamethrin[16]. The tests were carried out during the months of October to April based on the availability of An. jeyporiensis in the field.

Density, parity and blood feeding of vector mosquitoes

Daytime resting collections were done fortnightly in 3 randomly selected villages from January 2016 to December 2019 to monitor the vector density. Mosquitoes were collected using oral aspirators and flash lights in 3 human dwellings and 3 cattle sheds for 10 min in each catching station. In these villages, day time outdoor resting collections were made fortnightly in 12 pit shelters. In each shelter 5 min were spent for collecting the mosquitoes. The number of vectors collected indoors was expressed as number per man hour density indoors (PMHDI) resting density of vectors. Parity was determined using ovariolar dilatation method[17]. Blood meals of the fully fed female vector mosquitoes obtained from day time resting collections were analyzed to determine the blood meal source using the agar gel diffusion method[18].

Fever surveillance

Fortnightly, active fever surveillance was carried out in randomly selected six villages. Blood smears were collected from fever patients by the respective ASHA and screened microscopically for malaria infections at ICMR-VCRC laboratory. The malaria positive cases were administered anti-malarial drugs by the respective ASHAs. Incidence of malaria per 1000 population calculated from the fever surveillance data was used to assess the impact of the interventions. The data on malaria incidences for entire Koraput district was collected from the District Malaria Office, Koraput.

Statistical analysis

To compare the use rate of LLINs between different seasons, chi-square (χ2) test was used. The PMHDI of vectors between the pre and post LLIN distribution period was compared using student’s t-test. Logistic regression analysis was used to find out the difference in API between pre and post LLIN distribution period. All the analysis was done using SPSS 16.0 version.

Ethical statement

Since, no blood smear was collected by us; clearance from Institutional Human Ethical Committee was not required.


  Results Top


Coverage and use of LLINs

The net coverage survey in 54 randomly selected villages of Koraput after the mass distribution of LLINs showed that 2261 nets were distributed among 4600 population at the rate of 1 net per two persons. All the population in the surveyed villages were covered under LLINs. The percentage of holdings using net ranged from 93.8% to 100%. The season wise net use rate is given in [Figure 1]. No significant difference was found in the use rate of LLINs between three seasons (χ2=0.21, p>0.05).
Figure 1: Season-wise net use rate

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Bio efficacy of LLINs

A total of 100 mosquitoes were exposed to each LLIN and 50 mosquitoes were kept as control. Bio-assays were conducted between 8 and 30 months of mass distribution of LLINs and the mortality of An. jeyporiensis remained 100.0% when exposed to DuraNet and PermaNet after successive washes up to 8 times [Table 1].
Table 1: Results of net bioassays

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Density, parity and blood-feeding of vector mosquitoes

The density (number per man-hour) of An.fluviatilis and An. culicifacies recorded in indoors (human dwellings + cattle shed) is shown in [Figure 2] and [Figure 3], respectively. The PMHDI of An. fluviatilis before distribution of LLINs, varied from 0.0 to 4.7 and became zero after six months of distribution of LLINs and continued to be remained at 0.0 to 0.1 until December 2019. There was a significant reduction of average PMHDI (t=2.169, p=0.035) after the intervention. Before distribution of LLINs, the PMHDI of An. culicifacies varied from 0 to 12.2 and after introduction of LLINs, it varied from 0 to 9.3, with no significant difference (t=-0.351, p=0.727). The PMHDO of An.fluviatilis before distribution of LLINs, varied from 0.0 to 4.5 and after distribution varied from 0.0 to 0.5. Before distribution of LLINs, the PMHDO (per man hour density outdoors) of An. culicifacies varied from 0 to 0.5 and after introduction of LLINs, it varied from 0 to 0.7. Since, the density of both the vector species was zero in most of the outdoor collections, the analysis was not possible.
Figure 2: PMHDI (HD+CS) of An. fluviatilis

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Figure 3: PMHDI (HD+CS) of An. culicifacies

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The parity rate of An. fluviatilis was 29.5 and 24.2 before and after distribution of LLINs, respectively. The parity rate of An. culicifacies was 47.8 and reduced to 42.9 after distribution of LLINs. It may be noted that the parity of An. fluviatilis was calculated only up to six months of post distribution of LLINs, as the density of this species became zero after this period. After distribution of LLINs, of the 100 blood meals of An. fluviatilis tested, 0.6% had fed on human and 99.4% bovine, indicating important zoophagic behavior. Before intervention, 62.2% of An. fluviatilis fed on human. In the case of An. culicifacies, of the 643 blood meals tested; only 0.47% were positive for human and 99.53% for bovine indicating a highly zoophagic behaviour of this species. Before intervention, 0.75% of this species had fed on human.

Malaria incidences reported by state NVBDCP and IC-MR-VCRC

The monthly malaria parasite incidence recorded in the district by State NVBDCP and ICMR-VCRC is given in [Figure 4]. The monthly malaria parasite incidence observed by ICMR-VCRC ranged between 0 and 14.2 during pre-intervention period and after intervention the MPI varied from 0 to 1.1. The peak malaria incidence was recorded during July 2017. After distribution of LLINs, the malaria incidence decreased gradually and become zero after three months of distribution. The change of malaria incidence from pre to post distribution period was also significant (Wald statistics= 73.814, p<0.001; Odds ratio = 0.028, 95% CI: 0.012-0.064). Thereafter, with a minor fluctuation, the incidence of malaria maintained at zero level up to December 2019. While monthly malaria parasite incidence surveyed by NVBDCP varied 1.1 to 6.5 during pre-intervention period, the same ranged between 0.1 and 1.2 after intervention. There was 82.7% decline of malaria cases in the district during 2018 (6800 malaria cases reported during 2018 (API: 4.6) and 88.3% decline during 2019 (4609 malaria cases reported during 2019 (API: 3.1) compared to 39,173 in 2017 (API: 26.4) [Figure 4]. After mass distribution of LLINs (August 2017) and introduction of three rounds of DAMaN, malaria incidence in the district has reduced significantly (Wald statistics= 4.61, p<0.0001; Odds ratio = 0.137, 95% CI: 0.134-0.139).
Figure 4: Monthly malaria parasite incidence recorded by NVBDCP and ICMR-VCRC

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  Discussion Top


The current analysis showed that after introduction of new intervention tools in 2017, malaria cases in Koraput district reduced drastically. One of the reasons for such reduction is that the use rate of LLINs by the villagers was well above 90.0% throughout the year. Such a high use rate of nets was possible in the district due to introduction of an unique innovation by the district administration i.e. bell ringing in the central place of the village at 20.00 hrs every night by the ASHA workers to ensure the use of the nets by the community. The increase in the high use rate of LLINs was made possible by creating awareness in the community through frequent village meetings by the State health department. Another factor for such a massive reduction of malaria incidence in the district is due to the persistence of 100.0% bio-efficacy of LLINs even after 30 months of distribution of LLINs. It is expected that the LLINs provided to the villagers need to be replaced after three years of distribution[19],[20], as the residual bio-efficacy is expected to remain up to July 2020. Since the LLIN has largely contributed to the achievements in the decline of malaria in the district as well as in the entire State, there is a need to replenish these nets when the residual efficacy will start reducing. Therefore, continuous monitoring of the residual efficacy of distributed LLINs in a wide area is the need of the day. Other reason of malaria reduction in the district is that An. fluviatilis is susceptible to synthetic pyrethroids (SPs)[21] and when this insecticide was used judiciously, the density and other entomological factors of susceptible vector affected drastically. A preliminary entomological study conducted in Koraput district after distribution of LLINs showed the evidence of shifting of resting behaviour of An. fluviatilis from human dwellings to cattle sheds and to some extent to outdoors which may be due to the greater exposure of An.fluviatilis to synthetic pyrethroids used in LLINs[22]. The results of the current study showed that a change in the feeding behaviour of An. fluviatilis from anthropophagy to zoophagy as observed elsewhere[22]. Similarly, An. culicifacies, the other malaria vector in the district, though developed phenotypic resistance to SPs, the intensity bioassay showed that the resistance was of moderate level and the insecticide is still operationally effective[23]. It may be noted that, migration of malaria positive cases was not a problem in the district.

The implications of DAMaN could not be ignored, as the district has a passive surveillance system for detecting malaria cases by which only symptomatic cases are detected. The current routine surveillance system is incapable to detect asymptomatic cases often leading to under reporting of malaria cases[24],[25]. Earlier sample blood surveys conducted during 1989, 2010–2011, 2013 and 2017 in Koraput district showed that the gametocyte rates among the asymptomatic cases was 15.2%, 7.7%, 15.1% and 8.4%, respectively[4],[16],[26]. These studies clearly provide the evidence that a substantial proportion of the population in the district harbouring P. falciparum gametocytes served as a reservoir of the parasite, maintaining the natural transmission cycle. In this scenario, identifying asymptomatic malaria cases and providing anti-malaria treatment to them by DAMaN would certainly help in reducing the malaria transmission. So far, no drug (ACT) resistance in P. falciparum has been reported either in the district or in the State.


  Conclusion Top


The findings of the study clearly showed that the success of malaria control in Koraput district was mainly because of the introduction of effective vector control intervention, i.e., LLINs and early detection and liquidation of parasites in the human host. By utilising these malaria intervention tools, and if the reduction trend of malaria cases continues, achieving the target of malaria elimination under NFME would be possible within the time frame.

Conflict of interest: None



 
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