Tribal Community Visit to Malaria-Endemic Areas Can Pose Risk to Car Nicobar Island: Deterrent for Malaria Elimination
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Int J Travel Med Glob Health. 2019 Mar;7(1):33-37 doi 10.15171/ijtmgh.2019.07 J http://ijtmgh.com IInternationalTMGH Journal of Travel Medicine and Global Health Original Article Open Access Tribal Community Visit to Malaria-Endemic Areas Can Pose Risk to Car Nicobar Island: Deterrent for Malaria Elimination Zahid Ali Khan1, Ittoop Pulikkottil Sunish 1* 1Division of Medical Entomology, Regional Medical Research Centre-ICMR, Dollygunj, Port Blair, Andaman and Nicobar Islands 744103, India Corresponding Author: Ittoop Pulikkottil Sunish, PhD, Division of Medical Entomology, Regional Medical Research Centre- ICMR, Post Bag No. 13, Dollygunj, Port Blair, Andaman and Nicobar Islands 744103, India. Tel: +95-31954301, Email: [email protected] Received November 15, 2018; Accepted February 16, 2019; Online Published March 4, 2019 Abstract Introduction: In the past 10 years, a declining trend was seen in the annual parasite incidence (API) of malaria in the Car Nicobar Island. For the past few years, the API in the island has been below one. Car Nicobar Island is struggling with malaria cases reported to have been brought from other, malaria-endemic islands. Methods: The movements of people were monitored by door-to-door visits during early morning hours, and the frequency of their movements to different islands (malarious and non-malarious areas) were monitored. Results: A larger number of villagers visited non-malarious areas (OS-O) than malarious areas (OS-N). The maximum number of people was found out of station during the month of June. Thirty-seven percent of people were out of the station to non-malarious areas, while only 6% were out of the station to islands endemic for malaria. In the latter category, the majority of those who left the village were in the age groups of 16-30 years and 31–45 years. Even though fewer villagers visited malaria-endemic areas, their visits can pose a threat of malaria transmission, in view of the prevalence of local anopheline vectors. Conclusion: Understanding people’s movement patterns to and from high malaria-transmission areas is important to designing strategic evidence-based control plans. In Car Nicobar, the main transport facilities within the inter-islands are ship and helicopter services. Hence, post-arrival medical examinations should be made mandatory to prevent the introduction of malaria parasites into the island. Keywords: Malaria, Travel, Islands Citation: Khan ZA, Sunish IP. Tribal Community visit to malaria-endemic areas can pose risk to Car Nicobar Island: deterrent for malaria elimination. Int J Travel Med Glob Health. 2019;7(1):33-37. doi:10.15171/ijtmgh.2019.07. Introduction the transmission route of malaria parasites, principally The movement of people in a variety of forms and on various through the travel of infected persons, is vital for efficacious scales plays a significant role in the equation of malaria and intervention strategies across the full range of transmission people in parasite vectors, who contribute to the transmission intensities.6 Therefore, it is important to quantify the peoples’ of malaria by exposing other people to the risk of infection and movement while choosing appropriate control strategies obscuring its control. Health sectors worldwide have always and developing a comprehensive elimination feasibility recognized the movement of people as a significant means assessment.7 of infectious pathogen transmission.1 Peoples’ movement Malaria is one of the most important vector-borne diseases has historically stood as a great challenge to the control in the Andaman and Nicobar archipelago, but for the past few and elimination of malaria.2 The failure of global malaria decades, a decline in malaria incidence rate has been observed. eradication programs has been attributed mainly to human A total of 23 anopheline species have been reported in these population movement (HPM) as well as drug resistance.3,4 islands.8 Of these, Anopheles sundaicus cytotype ‘D’, which The introduced/imported cases contribute a great threat breeds in both fresh and brackish water, is the incriminated of outburst initiation, epidemics, or increasing indigenous malaria vector.9-11 This principal vector is primarily zoophagic transmission levels in highly accessible areas.5 Understanding (prefers to feed on animals), exophilic (prefers to rest Copyright © 2019 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (http:// creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Khan and Sunish outdoors), and exophagic (prefers to feed outdoors).12,13 The station for a sufficiently long period were excluded from the 2004 tsunami caused severe devastation in these islands, and survey. The movement of people to outstations was monitored the number of malaria cases increased due to the proliferation in monthly door-to-door visits in both villages during early of malaria vector species by the formation of more breeding morning hours by enquiring the presence and absence of habitats.14 Among the 3 districts of the Andaman and household members. Those people who were not available in Nicobar Islands, the Nicobar district was highly affected by the household for the survey but were present on the island the tsunami. Laborers who came from mainland India for were marked as absent, and those available in the household rehabilitation work were affected by malaria. Their movement were marked as present. People moved to and from different to different islands for construction purposes increased the islands, and these movements did not involve a permanent risk of malaria transmission. However, during the past few change of residence. These movements included visits to years, a drastic reduction in cases has been observed in the relatives, attendance at ceremonies, treatment-seeking in archipelago, and the API (annual parasite incidence) declined hospitals, etc. and resulted in a return to the island. Along from 11.9 in 2011 to 0.87 in 2017. the temporal dimension, those persons found out of station Car Nicobar is one of the 3 tehsils of the Nicobar district. during the sampling time were classified as “OS-O” for those Malaria was widespread in the island subsequent to the out of station to non-malarious areas (like Port Blair) or “OS- tsunami disaster of 2004. However, a declining trend was N” for those out of station to malarious areas (mainly to the observed in API for the years between 2011 and 2017, ranging Nicobar group of islands). The total population of the study from 4.4 to 0.20.15 In the other 2 tehsils of the Nicobar district, area was categorized into different age groups to depict which endemicity is still high with an API greater than 5. Vector particular age group had the highest frequency of movements. control intervention is being implemented on the Car Nicobar The study population was kept constant and those individuals Island and has been found to be effective, in contrast with who were born or expired during the survey were excluded the other islands of the Nicobar district. The introduction from the analysis. Guests who visited Car Nicobar Island of the larvivorous fish Gambusia affinis into the breeding from malaria-endemic areas (other Nicobar Islands) were habitats of the island is one reason for the declining trend of also recorded during the study period. malaria.16 Nonetheless, this island has struggled for the past few years with malaria likely brought from other, malaria Statistical Analysis endemic islands of the Nicobar district. One of the major The data was entered in Microsoft Excel worksheet and risk factors for malaria infection is the lack of community analyzed using Epi Info, version 20.0. Descriptive statistics awareness about malaria transmission and prevention.17 (frequencies, means, standard errors, and standard deviations) Being on the verge of eliminating malaria, having an API less were used to tabulate and describe the data. The chi-square test than one for the past few years, a quantifiable determination was used to determine the level of significance of variables. A of peoples’ movement is important to resolving how best to P value of <0.05 indicated statistical significance. devise intervention strategies.18 In view of these factors, the frequency of peoples’ movement to other islands (malaria Results endemic and non-endemic) and vice versa was investigated. The total population of the 2 studied villages (n = 1400) was categorized into different age groups: <5, 6-15, 16-30, 31-45, Methods 46-60, and >60 (Table 1). A non-significant difference was Study Site observed among different age groups of males and females Car Nicobar (located at 9.16°N, 92.75°E) spans over 127 km2 in the 2 villages (χ2 = 4.11; P = 0.533). The majority of the of mostly flat terrain, except for small hilly areas in the interior. people were present on the island during the survey period, The island has a human population of 17 800, as per the 2011 with a maximum number of 1385 (98.9%) during the month census, and is inhabited by the native aboriginal ‘Nicobari’ of December. Among the total population, 54.28% were male tribal community which belongs to the mongoloid race. The and 45.91% were female. current study was undertaken in 2 villages, viz., Kakana and Kinmai, for a period of one year (May 2016 to April 2017). Monitoring Out-of-Station Individuals Total population (‘n’ = number of people) of the study area was In the OS-O category (out of station to non-endemic area), 1400, and the majority of the villagers were farmers. Coconut the movement of the highest number of people was observed plantation is the main source of income. The 2 villages were in the month of June (6.07% ± SE 0.013), and gradually selected based on the malaria cases reported in the past few years.