CONTAINMENT

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Cambodian Cooler Box: A Low-Tech Solution for Storing Malaria RDTs

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In hot humid Cambodia, maintaining a ‘cool chain’ can be a problem. But the Cambodian National Centre for Parasitology, Entomology and Malaria Control (CNM) has an innovative solution. It has developed the Cambodian Cooler Box, with technical support from WHO and support from the USAID-funded University Research Co (URC), for perishable medical commodities in remote communities.

A village malaria worker in Pich Kiri, Pailin, with his Cambodian Cooler Box. Pix by WHO/Sonny Krishnan

Since malaria rapid diagnostic tests (RDTs) were introduced in Cambodia in 1996, the use of these tests has increased steadily.

The malaria containment project in Cambodia funded by the Bill & Melinda Gates Foundation uses RDTs to improve diagnosis of febrile illness in remote malaria-endemic areas where microscopy diagnostic services are not readily available.

Rising treatment costs due to introduction of artemisinin combination therapy has further raised the importance of proper malaria diagnosis prior to treatment, and the urgency to contain and eliminate emerging artemisinin-resistant malaria in western Cambodia has made rapid access, at community level, to both RDTs and anti-malarial drugs a priority for the Cambodian National Centre for Parasitology, Entomology and Malaria Control (CNM).

Front view of the Cambodian Cooler Box. Pix by WHO/Sonny Krishnan

Malaria RDTs are lateral-flow tests based on interactions of biological agents (antibodies and antigens) attached to or flowing along a nitro-cellulose strip. They are therefore sensitive to degradation by heat and humidity.

Heat can damage RDTs through deconjugation of the antibody-dye conjugate, detachment of the bound antibody from the nitrocellulose, loss of ability of the antibody to bind to antigen, and degradation of the nitrocellulose strip.

While packaging in moisture-proof envelopes can prevent exposure to humidity, if RDTs are stored at temperatures exceeding the recommended temperature it is likely that loss of sensitivity will occur and the shelf life of the RDTs will be reduced.

Previous studies in Cambodia have demonstrated storage temperatures for RDTs much higher than 30°C in remote health facilities. Temperatures in drug storerooms in some health centres can reach 42.5°C.

CNM, with technical support from WHO and support from the USAID-funded University Research Co (URC), has pioneered the introduction of evaporative cooler boxes for storage of medical supplies in remote clinics in Cambodia, known locally as the “Cambodian Cooler Box” (CCB).

Diagram showing a cross-section of the cooler box. Source/Malaria Journal

Cooling is based on the principle that water absorbs heat from its surroundings when changing from a liquid phase to its higher energy gaseous phase (evaporation). As heat is absorbed from the surroundings of the damp sacking cover, particularly from the galvanized iron sides of the box with which the sacking is in direct contact, the box sides and contents are cooled.

Evaporative cooling is an ancient technology that is still used for making water cool. While the idea is not new, the principle has not been put to use on a large scale to allow extension of important health interventions.

The CCB uses local materials and construction, and the prototypes cost only $25 to produce. Significant cooling can be achieved despite Cambodia being cooler than many other malaria-endemic countries and having high humidity, both of which should reduce the relative efficiency of evaporative cooling.

Development of a “cool chain” is not only important for many RDTs, it is also important for many medicines. Medicines are commonly stored and transported under the same conditions as RDTs in developing countries. In general, medicines should be stored under conditions similar to RDTs.

A village malaria worker checking the reading from a RDT. Cooler boxes ensure the efficacy of the RDTs. Pix by WHO/Sonny Krishnan

The study for this paper was done in two phases. Phase 1 was a pilot study conducted in Sampov Loun operational district storeroom and Ankor Ban Health Centre in Battambang province, Cambodia, from May to July, 2004. The province has a clearly defined dry season (December to May) and rainy season (June to November). The maximum temperature in the dry season can reach 38°C. This phase of the study was designed to demonstrate the temperature and humidity differences in the storerooms at ambient temperature, in the CCB without water and in the CCB with water.

Phase 2 was conducted in Sampov Loun, Serey Meanchey health centre storeroom and, Barieng Tlek storeroom in Battambang province, Cambodia between November 2005 and December 2006. These areas are malaria-endemic for both Plasmodium falciparum and Plasmodium vivax, and RDTs use used for malaria diagnosis. This phase of the study focused on investigation of temperature and humidity to which the RDTs were exposed and the stability of the RDTs during exposure to temperature and humidity in three conditions; ambient room temperature, CCB without water and, CCB with water (as designed).

Source/Malaria Journal

The results indicate that a low-cost, locally produced product employing evaporative cooling technology can effectively maintain safe storage temperatures well-below room temperatures in tropical conditions, even in the presence of relatively high ambient humidity. This has applications for the maintenance of quality of diagnostics and drugs in clinics in village-based settings.

This is an edited condensed version of the article “Low-technology cooling box for storage of malaria RDTs and other medical supplies in remote areas” by Lon Chanthap, Frédéric Ariey, Duong Socheat, Reiko Tsuyuoka and David Bell that appeared in Malaria Journal, Vol: 9, 2010. The full open-access article can be downloaded from http://www.malariajournal.com/content/9/1/31

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Written by malariacontainment

October 23, 2010 at 12:45 pm

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