Catching mosquitoes in the forest.

Name of investigators: Dr. Nguyen Xuan Quang, BA. Le Giap Ngo, BA. Vu Tuan AnhTechnician. Le Hoang Dung, Technician. Le Dinh Vinh, Nurse. Trinh Thi Nhu

Introduction

Malaria situation in the Central - Western Highlands in 2013 and the first nine months of 2014 tended to decrease. However in the last 2 months of 2014 (October, November), malaria was recorded with unexpected occurrence in the Central - Western Highlands areas, the proportion of malaria patients and parasites increased in almost every province. In particular, in October and November 2014, parasite rate of Gia Lai province increased from 71.38 to 168.89% compared to the same period in 2013. Therefore, we conducted surveys, epidemiological surveillance of malaria and the variation, distribution and behaviour of Anopheles mosquitoes in order to attain the objectives:

1. Evaluation of indicators of malaria in the community

2. Determination of the species composition, the number of species, density of malaria vectors in Ia Mla commune.

3. Dissection and conduction of ELISA tests to evaluate the proportion of mosquitos infected with Plasmodium parasite.

II. Location, duration, object andmethodology

2.1. Location: Ia Mla commune, KrongPa district, GiaLai province

2.2. Duration: From 12/16/2014 to 12/28/2014 (13 days).

2.3. Research design: The cross-sectional and retrospective study

2.4. Object of study

- Local people (especially forest goers, field-hut sleepers)

- Malaria transmitting Anopheles mosquitoes

2.5. The techniques and methods of investigation

2.5.1. Epidemiological investigation of malaria

- Epidemiological situation of malaria in the locality

- Examination and determination of clinical malaria cases and conduction of smear tests for 400 people to identify Plasmodium parasite in Ia Mla community.

2.5.2. Survey insect indicators

- Implement measures to investigate, monitor, collect adult mosquitoes and larvae due to the method of WHO (1994) and the National Institute of Malariology and Parasitology and Entomology, Ha Noi (2011).

- Species composition, Anopheles larval and mosquito densities.

- Ecology and behaviour of vectors such as biting and resting behaviour, host preference.

2.5.3 Mosquito dissection: Determine the rate of mosquitoes infected with malaria parasite

(Alive mosquitoes were dissected for oocyste, sporozoits and lay egg or not yet).

III. Results and discussions

a.The situation of malaria in the Ia Mla commune in 2014 (data district health)

Table 1: Malaria situation in 2014 compared to the same period in 2013

Malaria situation in Ia Mla commune in 2014:

- The proportion of Plasmodium /slides + test strips in 2014 is 16.3% (141/865).

- In 2014, Plasmodium in January increased by 280% while reduced from 24 to 100% in other months. Especially the last 2 months (November and December) of 2014, Plasmodium parasite surged from 28.6 to 93.3% in comparison with the same period in 2013.

- The overall number of Plasmodium reduced 26.9% in 2014 compared with the same period in 2013.

Graph 1: Performance ratio Plasmodium/slides+test strips in 2014 of Ia Mla commune

3.2. Results of the survey o­n the prevalence of malaria in the Ia Mla commune

Table 2: Results of cross-sectional survey o­n the prevalence of malaria in the Ia Mla commune

Conducting smear examination and blood tests for 400 people in the Ia Mla commune, 6 patients were found with clinical malaria, accounting for 1.5% and 7 blood tests found the malaria parasites, accounting for 1.75% and notfoundspleen.

3.3. Results of survey o­n social insects in Ia Mla commune

Table 3: Anopheles mosquito species composition in the Ia Mla commune

- In the hamlet, 8 species of anopheles were found not catching the disease vectors. In the hamlet, An. vagus and An. sinensis predominate.

- In the buffer zone (near the forest), 9 species of Anopheles were found, including the presence of main malaria vector - An. dirus and sub vector - An. aconitus and An. maculatus. In the buffer zone, An. aconitus and An. vagus dominate.

- In the plot-huts, 5 species of Anopheles were found, including the presence of main malaria vector - An. dirus and 2 sub vector - An. aconitus and An. maculatus. In the forests, An. dirus predominate.

Table 4: Results of investigation of Anopheles mosquitoes in residential areas in the Ia Mla commune

Investigation of mosquitoes in residential areas showed that the main malaria vectors - An. dirus, An. Minimus were not found; only found the sub vector - An. maculatus.

Table 5: Results of the survey o­n Anopheles mosquitoes in the buffer zone of the Ia Mla commune

Investigation of mosquitoes has found that the main malaria vector is An. Dirus in the buffer zone, with a density of 0.33 mosquito/trap/night and also found the sub vectors: An. aconitus and An. maculatus.

Table 6: Results of investigation of Anopheles mosquito in the plot-huts in the Ia Mla commune

Investigation of mosquitoes in the plot-huts has found that the main malaria vector is An. Dirus, with a density of 1.0-1.5 mosquito/person/night and 0.17 to 1.33 mosquito/trap/night; in addition the sub vectors An. maculatus and An. Aconitu are also found.

3.4 Activity of anopheles mosquito

Table 7: Activities of Anopheles mosquitoes in the upland forest of Ia Mla commune

Noted: I: Collected by the human bait indoor; O: Collected by the human bait outdoor

Anopheles mosquitos fly and bite after 8 p.m., after 23 p.m. due to bad weather conditions: cold, windy, Anopheles mosquitos were not caught.

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