Myanamr Health Research Registration 2020; 32(1): 46-50.
Vector Bionomic Study in Kayah State and Kachin State
Aye Aye Myint,Thiha, Ohmar Nyo, Abraham, Aung Thi & Nay Yi Yi Lin
Myanmar Health Sciences Research Journal, 2020; 32(1):46-50ABSTRACT
ï»¿Malaria is still one of the most important public health problems in Myanmar. National Malaria Control Programme (NMCP) has implemented malaria prevention and control activities based on national malaria control strategies. One of the strategies is selective and sustainable vector control measures with integrated vector management approach which includes distribution of Long Lasting Insecticide Treated Nets (LLINs), Insecticide Treated Nets (ITN) and Indoor Residual Spray (IRS) whenever and whatever necessary. As the country scale up distribution LLIN and ITN programme, insecticide selection pressure on the vector mosquito populations is increased. Susceptibility status of insecticides could depend on population migration and environmental changes and ecology factors in relation to human behavior. Therefore, malaria vector bionomic and insecticide susceptibility status study should be investigated in these malaria endemic areas. The present study was conducted in Kayah State and Kachin State. In Nankit Village, Kayah State, nineteen Anopheles species were collected and An. minimus was primary vector. In the whole night collection, peak biting time of An. minimus was 9 to 10 pm in first peak and 2 to 3 am in second peak. The highest density of An. minimus was observed in November. An. minimus was susceptible to 0.05% deltamethrin and 0.5% ectofenprox. In Tanphae and Ngwepyaw Sampya villages, Kachin State, more than 20 Anopheles species were collected and An. minimus and An. dirus were primary vectors in these areas. The density of the An. minimus was highest in June, and An. maculatus was also highest in June, but An. annularis which were higher density in December. Peak biting time of An. minimus was 20:00 to 21:00 and that of An. maculatus was 19:00 to 20:00. An. kochi was susceptible to 0.05% deltamethrin with 100% mortality.
Vector bionomic study (Nankit village, Phasaung Township, Kayah State)
The village is located at the forested and foothill area with slow running streams that is favorable for An. minimus breed.The primary vectors such as An.dirus, An.minimus, and the secondary vectors and other 17 anopheles species were collected. The primary vector, An.minimus was collected by human landing indoor and outdoor collection and animal bait net trap collection(Table 1).
Table 1. Totalnumber of Anopheles caught from Nankit village, PhasaungTownship
The feeding habit was both indoor and outdoor. Host preference was feeding on man (anthropophilic) and animal (zoophilic). The An.minimus biting density of human landing indoor collection is 0.915 per man-hour and outdoor is 0.86 per man-hour(Fig. 1).
Fig. 1.Human landing outdoor and indoor density in Nankit village, Phasaung TownshipIn the whole night collection, peak biting time of An.minimus was about 21:00to 22:00in first peak and 2:00-3:00 in second peak of the night. By animal bait net trap collection,An.minimus and other anopheline species (19)were collected (Table 2).
An. minimus were also collected in light trap collection. In monitoring the insecticide resistance, An. minimus was susceptible to 0.05% deltamethrin and 0.5% ectofenprox and An. philippinensis to 0.05% deltamethrin, 0.05% lambdacyhalothrin and 0.5% ectofenprox.An. peditaeniatus was resistant to 0.05% deltamethrin and 0.5% ectofenprox. An. maculatus was susceptible to 0.75% per-methrin and An. annularis was susceptible to 4% malathion, respectively. Bio-assay test was conducted with YorkoolR impregnated bed net (date of production 2015) and 92% mortality of An. minimus and 96% mortality of An. philippinensis were observed.Human bait 18.16% and animal bait 81.8% were found. It might have been zooprophylaxis effect in the village. There was reduction in number of cows and buffaloes in the village that can deviate the feeding of mosquitoes from animal to man.
In Tanphae village,Myitkyina Township,Kachin State
This village comprised a total of 67 houses with 168 population and the villagers earned their living by agricultures and forest-related works. In 2016, out of 807 blood smears taken by Rapid Diagnosis Test (RDT), 7 falciparum and 9 non-falciparum malaria were detected.The distribution of LLINs and Indoor residual spray has been conducted by NMCP since May 2016 for vector control.
Table 3. Total number of Anopheles caught from Tanphae village, Myitkyina Township,Kachin
A total of 25 Anopheles species were caught from Tanphae village (Table 3).Biting habit of the Anopheles vector was assessed by human bait and cattle bait. Zoophilics nature of both vector species was observed with 72% of An.minimus vs 58% of An.maculatus. Peak biting time of An.minimus was 20:00to 21:00 and An.maculatus was 19:00-20:00. The behavior and biting pattern of the vectors seemed to be related to the night-time activities of the villagers. Annual man biting rates were higher in An.minimus, An.maculatus and An.annularis, ie, 174.84, 264.26 and 199.66, respectively. Annual man biting rate was highest in An.maculatus followed by An.annularis and An. minimus (Table 4).Animal bait net trap collection: The anopheline species were tested for insecticide resistance with insecticide impregnated paper and bioassay test for LLIN sefficacy. For bioassay test,LLIN (permanet for one and half year, no wash) showed effective 100% mortality with An.minimusand LLIN (permanet for one and half year, no wash) and LLIN (Yorkool for two years with no wash) were effective 80% and 89% mortality with An.maculatus, LLIN (Yorkool for two years with no wash) was effective 80% with An. kochi. Monitoring of insecticide resistance with insecticide impregnated paper was carried out and An.kochi was susceptible to 0.05% deltamethrin with 100% mortality.
Table 4. Seasonal man biting rate (MBR) of different Anopheles species in Tan-phae village, Myitkyina Township, Kachin State, 2017
Annual man biting rate was highest in An.maculatus followed by An.minimus.
Ngwepyawe Sampya village
As of 2017, the total population was 1799 and the occupation of the people were forest related workers, selling and buying of goods and commodities. In 2016, 69 malaria blood smears were taken and 2Pf positives were found. Indoor residual spray with Fondana (alphacypermethrin) has been conducted by NMCP since 2014. By human landing out-door collection at about 22:00-23:00,more density was collected at the later part of the night than the early part of the night at about 19:00-21:00. It is closely related to the night movement and sleeping pattern of the local people, because the locality is also urbanized and with electricity at night. By human landing outdoor collection An. minimus was 0.05 m/hr, An. maculatus was0.03 m/hr, An. aconitus was 0.04 m/hr, An. splendidus was 0.1 m/hr, An. peditaentiatus was 0.01m/hr and An.kochi was 0.01m/hr. By animal bait net trap collection, An.minimus and 9 Ano-phelinespecies were collected. An.minimus, An.maculatus and An.splendidus were collectedin light trap indoor collection and An.hyrcanus and Culex species were collected in light trap outdoor collection. An.minimuslarvae(0.73per dips) were collected in small pools. An.hyrcanus of anopheles specie,was tested for insecticide resistant and found that it was highly resistant to 0.05% deltamethrin with mortality of 15%.Human bait of 31.86% and animal bait of 68.13% were found. It might have been zooprophylaxis effect in the village. There was reduction in number of cows and buffaloes in the village, that could deviate the feeding of mosquitoes from animal to man.
ELISA for circumsporozoite protein for vector Anophelines from Kayah State and Kachin StateThe ELISA test for circumsporozoite protein was conducted. From Phasaung Township, KayahState and Myitkyina Township, Kachin State, An.minimus, An.maculatus, An.annularia, An.aconitus, An.philip-pinensis, An.tessellatus and An.hyrcanus of the vector anopheline species were tested with ELISA. Out of 850 mosquitoes samples collected from field, five were found positive in Kachin State. The Pf positives of An.minimus and An.philippinensis were found in Ngwepyaw Sanpya village.
ï»¿Malaria is still one of the important public health problems in Myanmar. National Malaria Control Programme (NMCP) has implemented malaria prevention and control activities based on national malaria control strategies. One of the strategies is selective and sustainable vector control measures with integrated vector management approach which includes distribution of LLINs, ITN and IRS whenever and whatever necessary.
As the country scale up distribution LLINsÂ and ITN programme, insecticide selection pressure on the vector mosquito populations is increased. The success of any vector control program relies on knowledge of vector species and their bionomics which is very importantÂ to get update knowledge and information on primary and secondary vectors, distribution is related to environmental changes. Monitoring level of resistance is an essential tool in enabling to make a decision. Resistance to insecticidesÂ is concerned due to population migration and changes of environment and ecology factors in relation to human behavior.1, 2 Thus, the vector bionomic and insecticide resistance susceptibility status survey should be investigated in this region.
MATERIALS AND METHODS
Localities and survey period
Vector bionomic survey was conducted in Nankit village, Phasaung Township, Kayah State during October, November and December, 2016. Nankit village is situated in latitude 18.89613ÂºN and longitude 97.30016ÂºE. Vector bionomic survey was also conducted in Tanphae and Ngwepyawe Sampya villages, Myitkyina Township, Kachin State during the period of March, June, September and December 2017. Tanphae village is situated in 25.71536ÂºN, 97.49098ÂºE, 633 feet above sea level and 27 miles far from Myitkyina and side of the Myitkyina-Putao highway road. Ngwe-pyawe Sampya village is about 14 miles far from Myitkyina, at the latitude 25.56707ÂºN and longitude 97.35565ÂºE with above sea level of 564 feet.
Entomological survey include: human landing indoor and outdoor collection, animal bait net trap collection, light trap collection, morning resting indoor and outdoor hand collection, spray sheet collection, larval collection, susceptibility test, bio-assay test and sporozoite detection with ELISA test.3
ï»¿Entomological surveillance in sentinel sites was conducted annually by Entomology team of the NMCP. Both in Phasaung Township, Kayah State and Myitkyina Township, Kachin State, primary vectors of An. minimus, An. dirus and other secondary vectors were observed in entomological survey. Entomological surveillance and vector control is an important component in malaria elimination programme. In Kayah State, the primary vectors of An. dirus, An. minimus, and 17 anopheles species were observed. The An. minimus biting density of human landing indoor collection is higher than outdoor. The peak biting time of An. minimus was 21:00 to 22:00 in first peak and 2-3 am in second peak. An. minimus, An. maculatus and An. philippinenesis were susceptible to pyrethroid and An. annularis was susceptible to organophosphate. According to the efficacy of the local LLINs, WHO optimal effective was observed.
In Kachin State, An. minimuswas observed in all entomological collection methods. Peak biting time of An. minimus was 20:00 to 21:00 and An. maculatus was 19:00-20:00. An. kochi is susceptible to pyrethroid. Biting habit of the Anopheles vector was assessed by human bait and cattle bait. Zoophilics nature of both vector species was observed as 72% of An. minimus vs. 58% ofÂ An. maculatus. There was reduction in number of cows and buffaloes in the village that could deviate the feeding of mosquitoes from animal to man. According to the efficacy of the local LLINs, WHO optimal effective was also observed. According to ELISA test, five positives were found in Kachin State.
ï»¿ï»¿ï»¿ï»¿ï»¿ï»¿ï»¿ï»¿ï»¿ï»¿We would like to express our special gratitude to the National Malaria Control Program for permission to conduct this research. Thanks are also due to the staffs from Regional and Township Health Departments in Kayah State and Kachin State for collaboration. Special thanks to Global Fund for funding support.
The authors declare that they have no competing
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