Product Name : Development of a comprehensive test kit for the rapid detection of insecticide resistance
Centre : Infectious Disease Research Centre
Unit : Entomology Unit
Awards :
Descriptions
Today resistance detection is dependent on the use of WHO test kits which provide insecticides for the direct testing of insects. Although useful and effective, WHO tests possess inherent weaknesses such as the requirement of large number of test insects, shelf life of test insecticide, high cost etc which have prevented their widespread use. We developed a comprehensive kit for the rapid detection of non-specific esterases, oxidases and insensitive acetylcholinesterase, the detoxification enzymes responsible for resistance to insecticides. Using eye score to read colorimetrically, the degree of resistance can be estimated. This kit has many advantages over WHO test i.e. requires only a single specimen, low cost, rapid, sensitive and easy to conduct in the field without the use of any equipment. The kit is now commercialised by a local company.
These rapid test methods are the world's first rapid kits that can be used by vector control agencies worldwide in the rapid screening of large number of specimens in a relative short time at affordable cost. Decisions can then made to remedy the situations if resistance is detected. These micro tests were first used and reported by Lee (1990) for determining the resistance status of Malaysian Culex quinquefasciatus mosquito. The author had successfully determined that insecticide resistance in this mosquito was due to elevated level of non-specific esterases. Since then, these technique is used for the rapid detection of insecticide resistance, not only in mosquitoes, but also inclusive of the housefly and cockroaches.
Problems associated with the use of 45-years old WHO test kits for insecticide resistance detection have been resolved on the introduction of the new micro tests. Researchers are now able to routinely use this novel method in assays against insects because of the rapid and low cost nature of the tests. Even in the laboratories, no sophisticated equipment is required and the requirement of skilled manpower which is so often lacking is now eliminated by adoption of the new tests. Vector control specialists in the field have now a valuable tool in their hands to rapidly assess the status of inset susceptibility which is crucial in ensuring a successful outcome in their control efforts.
ADVANTAGES OF RAPID TEST
COST:
The cost of testing has been reduced significantly with the introduction of the novel rapid test. The cost comparison of the WHO test kit and new microassay test kit is shown as below:
|
ITEM |
*COST OF A NEW TEST KIT |
*COST OF WHO TEST KIT |
|
1. A complete kit |
RM 95 |
RM 580 |
|
2. Consumables |
RM 17 |
RM 450 |
|
TOTAL/kit |
RM 112 |
RM 1,030 |
- Cost is estimated for testing of 10,000 mosquitoes
Hence a microassay test kit is about 10 times lower in cost compared with the standard WHO Test Kit and this represent a cost-saving of 10 times in expenses.
TIME-SAVING:
Time saving in the implementation of the new test is shown below:
|
PROCEDURES |
RAPID TEST |
WHO TEST |
|
1. Insect collection |
2 hours |
2 hours |
|
2. Insect rearing in lab |
0 hour |
10 days |
|
3. Actual testing |
1 hour |
24 hours |
|
TOTAL TIME |
3 hours |
11 days 2 hours |
Much time have been saved with the use of the new test. The most time saving aspect of the new test is in the rearing of the test insect. It is unnecessary to breed large number of insects for the test, which however, is a pre-requisite in the WHO test method. To do so would also require insectarium facilities and skilled manpower for rearing the test insects. At times, rearing may also failed which will then entail another collection and more time spent .
PRODUCTIVITY:
- Using this new test method, large number of mosquitoes can be screened in a short period of time. We estimated that about 500 single mosquito specimens can be screened in 1 hour. (WHO Test method= 500 mosquitoes in 24 hour).
- Since 8 replicate tests can be obtained from each mosquito specimen, a total of 4,000 replicate readings can be obtained in one hour. (WHO Test= 3 replicates per concentration)
- The new test can be used to screen resistance to all groups of insecticide which induce high level of non-specific esterases. (WHO Test= 1 insecticide per test).
- Less skilled manpower required. The new test requires only 1 person to run the test (WHO Test= usually several workers required)
CLIENT SATISFACTION:
Introduction of this new test enables the client i.e. vector control agencies (e.g. Ministry of Health) to be able to ascertain the resistance status of the vectors in the field rapidly. This is important because rapid response to insecticide resistance is required to ensure that remedial actions can be taken to contain the vectors e.g. introducing new vector control measures. In the past, this is difficult to achieve because of the problems associated with the WHO Test Kit. The vector control specialists are now in a better position to monitor the occurrence of resistance under field conditions.
OTHER ADVANTAGES:
- Introduction of high technology in vector control.
- Since the new test can be conducted rapidly, the quality of the test is ensured.
- The requirement for skilled manpower is much reduced
- This new test possesses the commercialisation potential
