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BMC Malaria Journal

Designing malaria surveillance strategies for mobile and migrant populations in Nepal: a mixed-methods study

Jennifer L. Smith^†, Prakash Ghimire^†, Komal Raj Rijal, Alysse Maglior, Sara Hollis, Ricardo Andrade-Pacheco, Garib Das Thakur, Nabaraj Adhikari, Upendra Thapa Shrestha, Megha Raj Banjara, Bibek Kumar Lal, Jerry O. Jacobson and Adam Bennett

^†Contributed equally

Malaria Journal201918:158 https://doi.org/10.1186/s12936-019-2791-1

© The Author(s) 2019

Received: 18 January 2019            Accepted: 23 April 2019    Published: 3 May 2019

ABSTRACT

Background

As malaria cases have declined throughout Nepal, imported cases comprise an increasing share of the remaining malaria caseload, yet how to effectively target mobile and migrant populations (MMPs) at greatest risk is not well understood. This formative research aimed to confirm the link between imported and indigenous cases, characterize high-risk MMPs, and identify opportunities to adapt surveillance and intervention strategies to them.

Methods

The study used a mixed-methods approach in three districts in far and mid-western Nepal, including (i) a retrospective analysis of passive surveillance data, (ii) a quantitative health facility-based survey of imported cases and their MMP social contacts recruited by peer-referral, and (iii) focus group (FG) discussions and key informant interviews (KIIs) with a subset of survey participants. Retrospective case data were summarised and the association between monthly indigenous case counts and importation rates in the previous month was investigated using Bayesian spatio-temporal regression models. Quantitative data from structured interviews were summarised to develop profiles of imported cases and MMP contacts, including travel characteristics and malaria knowledge, attitudes and practice. Descriptive statistics of the size of cases’ MMP social networks are presented as a measure of potential programme reach. To explore opportunities and barriers for targeted malaria surveillance, data from FGs and KIIs were formally analysed using a thematic content analysis approach.

Results

More than half (54.1%) of malaria cases between 2013 and 2016 were classified as imported and there was a positive association between monthly indigenous cases (incidence rate ratio (IRR) 1.02 95% CI 1.01–1.03) and the previous month’s case importation rate. High-risk MMPs were identified as predominantly adult male labourers, who travel to malaria endemic areas of India, often lack a basic understanding of malaria transmission and prevention, rarely use ITNs while travelling and tend not to seek treatment when ill or prefer informal private providers. Important obstacles were identified to accessing Nepali MMPs at border crossings and at workplaces within India. However, strong social connectivity during travel and while in India, as well as return to Nepal for large seasonal festivals, provide opportunities for peer-referral-based and venue-based surveillance and intervention approaches, respectively.

Conclusions

Population mobility and imported malaria cases from India may help to drive local transmission in border areas of far and mid-western Nepal. Enhanced surveillance targeting high-risk MMP subgroups would improve early malaria diagnosis and treatment, as well as provide a platform for education and intervention campaigns. A combination of community-based approaches is likely necessary to achieve malaria elimination in Nepal.

Keywords

Imported malaria cases, Mobile migrant populations (MMPs), Focus group discussion, Key informants’ interview, Malaria elimination, Nepal

Full text: https://malariajournal.biomedcentral.com/track/pdf/10.1186/s12936-019-2791-1

Staining-the basic concept

Staining

Microorganism are very minute, generally they are colorless and transparent so it is very difficult to focus through microscope. The use of special types of microscopy such as phase contrast and dark field techniques is design to improve visualization; however these techniques require special microscopes and training. In common purpose we use light microscope for direct observation of bacteria, to observe through this we have to increase the contrast of the organisms against their background is necessary, to do this microorganism should be colored against their background i.e  application of staining techniques.

Staining: It is the process of coloring of microbial cells and their parts with the application of a dye or dyes to a fixed smear.

Stains or dyes: Yhey are coloring compounds, chemically they are salt as they contain acidic or basic part of stain. Microbiologists mostly use aniline or synthetic dyes. Each dye molecule has two functional groups, the auxochrome and chromophore.

•       Auxochrome: It ionizes and gives the molecules the ability to react with substrate.

•       Chromophore: It is site of unsaturation and absorbs specific wavelength of light. The color of the solution obtained is that of the  unabsorbed light which transmitted through it.

The synthetic dyes be classified as Acidic, Basic and Neutral dyes depending on whether the coloring bearing compound is a cation and an anion.

•       Acidic dyes: Anionic dyes, which react with substrate group which ionize to produce positive charge such as corboxyl, phenolic or sulfydryl etc. Anionic dyes are usually found as sodium. Eg: Nigrosin, Congo red, Eosin, Acid fuchsin etc.

•       Basic dyes: Cationic dyes, which react with substrate group which ionize to produce negative charge such as ammonium ions. Anionic dyes are usually found as chlorides or sulfates. Eg: Methylene Blue, Crysal Violet, Safranin etc.

•       On the basis of number of dyes and staining techniques used, staining are of following types;

•       1:   Simple staining: In this staining only single dye is used. Morphology of bacteria, yeast and mold are observed. Generally, positively charged chromophores are used in this staining. Methylene blue, Basic fuchsin, Crystal violet etc are used.

•       2:            Negative Staining: It is the techniques where the background is stained leaving the bacterial cell unstained due to electrostatic repelling between same charged cell and stain used. Heat fix is avoided so the accurate size, shape and arrangement can be measured and studied. Bacteria which are hard to stain like Spirochaetes, Mycobacterium and Nocardia are used in this techniques. Capsule staining is one of this techniques. Stains nigrosin, congored, eosin, acid fuchsin are used.

•       3:            Differential Staining: In this techniques more than one dye is used. It is applied in categorization of bacteria into two groups. It stains specific structure of cell eg: flagella, spore, capsule etc. Gram staining categorizes bacteria into two groups i.e gram positive and gram negative.