Aedes aegypti survey, Adelaide River, Pine Creek and Daly River : 26-29 April 1983

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Northern Territory Department of Health Library Services Historical Collection

210:)4 :5 6 :!

NORTHERN TERRITORY DEPARTMENT OF HEALTH MEDICAL ENTOMOLOGY BRANCH

AEDES AEGYPTI SURVEY

ADELAIDE RIVER, PINE CREEK AND DALY RIVER 26 - 29 April 1983

Dl. HI~ T

535 ,"77'2 HOD

13 ,:

1.0 INTRODUCTION

The recognised vector of dengue fever in Australia is Aedes aegypti, a mosquito which is at present restricted to Queensland. A survey to determine whether it has been introduced into the Northern Territory communities of Adelaide River, Pine Creek and Daly River was conducted during April by two officers from the Medical Entomology Branch.

2.0 METHOD

DL HIST 595.772 HOD 1983

2.1 Aedes Container Survey

A survey for container breeding Aedes mosquitoes was conducted to determine whether Aedes aegypti was present as larvae in the communities, and to detect other Aedes species present. The container survey was carried out by searching for, and examining any water filled container for mosquito larvae. Samples of mosquito larvae were collected in labelled vials of 70% alcohol and returned to the Medical Entomology laboratory for indentification.

2.2 Adult Mosquito Survey

An adult mosquito survey was conducted at each place to determine the presence and relative abundance of other mosquito vectors. Sampling was conducted using CO₂ baited traps, which were set out in and

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3.0

near the conununities, or at places nearby that were likely to be mosquito breeding areas of significance to the conununities. The traps were run from sundown to sunrise, and collected in the morning. The mosquitoes from the traps·· were killed and stored for later identification.

RESULTS

3.1 Aedes Container Survey

The results of the container survey are displayed in Tables 1 to 4.

Table 1 sets out the number of premises examined (a total of 38), the number of containers found with water (195), those with mosquito breeding (62) and the mosquito species present. This is an average of 5 containers per premise examined and 31% of all containers were supporting mosquito breeding.

Tables 2 to 4 show the type of containers found 1n each town surveyed, and the number of times each container was encountered. Tyres were the most commonly recorded containers (77 recorded) and supported the highest proportion of breeding

-

^43%

of breeding found was occurring in tyres.

Aedes notoscriptus was the most frequently collected Aedes species. Aedes aegypti was not detected in any of the containers.

3.2 Adult Mosquito Survey

Results of the CO₂ trap collections at each town are set out in Tables 5 and 7. Eighteen different sites were sampled ( 6 in each town) and twenty-two ( 22) species of mosquitoes were collected. Cul ex annulirostris was the most commonly collected

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3

mosquito, constituting 59% of the total collection.

Anopheles farauti, the principal suspected vector of malaria in the Northern Territory, was not detected at any of the towns surveyed .

4.0 DISCUSSION

14.9B

4.1 Aedes aegypti Survey

4.2

The survey was conducted in the late wet season when many containers were holding water. Compared with other Top End Aedes aegypti surveys, this survey found a relatively high incidence of containers with water, with the highest incidence being 1n Daly River (22 containers in 3 premises searched).

The most commonly collected Aedes species was Aedes

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notoscriptus, which was detected in all communities surveyed, both as larvae and adults. Aedes katherinensis and Aedes tremulus larvae were recorded from Adelaide River and Pine Creek, but not from Daly River. There were only two species of larvae recorded from Daly River (Aedes notoscriptus and Culex halifaxii).

Aedes aegypti utilises similar breeding sites to the above mentioned Aedes species, and it is probably, had it been present in any of the localities visited, that it would have been detected.

Therefore, lack of detection of Aedes aegypti indicates that the localities inspected were free of this mosquito at the time of the survey.

Other Mosquitoes

A total of 22 species of mosquitoes were recorded in CO₂ traps during the survey period. The most common species from all centres surveyed was Culex annulirostris.

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Adelaide River

Adelaide River CO₂ trap catches were all relatively low, with the highest catches being at the Showgrounds ( 65 mosquitoes) and the sewerage ponds

(46 mosquitoes).

Traps set within the town area collected small numbers of mosquitoes, indicating very minor nuisance and minimal disease transmission risk at the time of the survey. Whilst it is not reflected in CO₂ trap catches, a larval survey at the sewerage ponds revealed extensive breeding of Culex annulirostris amongst grass and weed growth at the margins of the primary and secondary ponds.

of the proximity of the ponds to the approximately 1.5 km the ponds could

In view town

be an important source of Culex annulirostris for the town.

Pine Creek

Culex annulirostris accounted for 71% of the total catch in Pine Creek, with the highest number recorded in the CO₂ trap adjacent to the sewerage ponds. A larval survey of the ponds revealed significant breeding of Culex annulirostris amongst grass and week growth in the primary, secondary and evaporation ponds. As these ponds are only approximately 2. 3 km from town and well within the flight range of Cul ex annulirostris, it is likely that they constitute an important source of this species for the town, with associated disease and nuisance problems.

Daly River

At Daly River, Culex annulirostris was the most commonly collected in CO₂ traps ( 55% of the total

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14.9B

5

catch). Each trap set recorded relatively high numbers of this species, ranging from 70 to 270 Culex annulirostris per trap. Anopheles bancroftii, a suspected malaria vector in the Northern Territory, made up 21% o~the catches in Daly River.

This species typically breeds in permanent fresh water swamps. High numbers of mosquitoes collected in this area were most likely the result of breeding in the extensive shallow flooded areas in the region, caused by flooding of the Daly River (6.7 m above normal dry season flow). The water was flowing through low lying areas outside the river banks, and mosquito breeding is likely to increase when flow ceases as flood waters recede, leaving remnant flooded areas of still water, which are likely to provide suitable mosquito breeding sites.

Culex pullus was taken in moderate to high numbers from this area. This species usually breeds in a variety of sites including containers and temporary pools, and does not generally bite man.

Anopheles far au ti, the suspected principle malaria vector, was not collected in any of the areas surveyed. Northern Territory Heal th has not collected this species in these towns since collections began in 1974, although earlier records exist for these areas. Failure to detect this species may be due to the rarity of Anopheles farauti in these localities, or to collections being made at suboptimum times of the year. In other areas of the Northern Territory Anopheles farauti is reasonably common during April, and this survey suggests that this species is rare in these towns, at least at present.

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5.0 CONCLUSIONS

5 .1 At the time of the survey Aedes aegypti was not present in any of the localities visited.

5.2 The high numbers of containers with water suggests that an awareness campaign, to inform the public of the dangers associated with mosquitoes, could be of great value. This campaign could be implemented by heal th workers or heal th surveyors in each community, with advice and materials available from the Health Education Section, Northern Territory Department of Heal th. A clean up campaign of all containers breeding mosquitoes would be beneficial.

5.3 Sewerage ponds at Adelaide River and Pine Creek need clearing of weeds and maintained weed free to reduce the large numbers of Culex annulirostris breeding in them.

5.4 High numbers of mosquitoes at Daly River at the time of the survey indicate a significant mosquito nuisance and a risk for the transmission of certain arboviruses Culex annulirostris is known to vector.

These high numbers are most likely a temporary fluctuation due to flooding providing abundant breeding sites. Owing to the extent of the floodwater in the area, control measures are not practicable at this stage. Inspection after floodwaters recede would be required to detect if any remnant waterbodies are present, and whether they are breeding appreciable numbers of mosquitoes.

Sui table options for control could then be sought from the Entomology Section. In the meantime, personal protection and avoidance of exposure during peak biting times for mosquitoes is recommended to reduce the potential of mosquito borne disease.

Kevin Hodder Wendy Kelton·

Officers conducting Survey

G. Davis

Supervising Officer P. Whelan O.I.C.

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TABLE 1 Aedes aeg:ypti SURVEY - ADELAIDE RIVER! PINE CREEKl DALY RIVER APRIL, 1983

LOCATION OF SOURCE

Locality No of Date No of No of No of No of containers positive for each species premises examined premises containers containers _{~ ~ ~} ()

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examined with with water with larvae ^{(D (D (D ~}

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breeding ⁰ rt ^Ii CD ^Pl rt ^~ I-' ^~ I-'· ^Pl I-' ^{t-o (D}

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t-o ^(D Pl ^{I-'· Ul}

rt ::s ^Ul

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ADELAIDE RIVER 19 26/4/83 10 66 24 15 2 2 6 8 3 2

PINE CREEK 16 27/4/83 9 107 31 21 1 2 1 10 3

DALY RIVER 3 28/4/83 3 22 7 6 1

TOTALS 38 22 195 62 42 3 4 7 18 7 2

TABLE 2 Aedes aegypti SURVEY - ADELAIDE RIVER 16/4/83

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Type of container No of No of No. of containers positive for each specie~

with water times times _{::i::i ::i::i ~ () () () 1-3} container larvae ^{(D (D}

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^{(D X X}

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^{X X}

recorded present _{~ rt ;,.;" trj ~ ::r' CJ)}

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Tyres 16 5 3 2 1 1 1

Plastic containers 9 2 2

Drums (44gal etc) 6 2 1 1 1

Buckets 5 3 2 .1 2 1

Plastic bowls 5 0

Watering can 2 0

Plastic lunch box 2 1 1 1

Plant pot 2 0

Truck tray 2 0

Tree hole 2 2 1 1 2

Baking dish 2 1 1

Car body 2 .1 1

Cement mixer 2 1 1 1

Stoneware 1 1 1

Sea shell 1 1 1

Garbage bin 1 1 1

Camp oven 1 1 1 1 1

Freezer liner 1 1 1 1

Terrarium .1 1 1

Hub cap 1 0

Paint tin .1 0

" Refrigerator crisper .1 0

TOTALS 66 24 15 2 2 6 8 3 2

TABLE 3 Aedes aegypti SURVEY.,... l?INE CREEK 27/4/83

Type of container No of No of No of containers positive for each species

with water times times

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_{container larvae} ^::i:,i (D ^::i:,i (D

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^::i:,i (D ⁽⁾ ~ ⁽⁾ ~ ⁽⁾ ~

recorded present

::s rt X" t-o ^µJ ::,-"'

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Tyres 50 l7 13 1 6 l

Drums (44gal etc) 8 5 3 .1 2 .1

Buckets 7 2 .1 1

Plastic containers 6 3 .1 .1 .1

Paint tins 5 0

Rainwater tanks 5 0

Car bodies 4 l 1

Bowls 4 .1 1 .1

Baths 2 0

Wheel barrows 2 0

Animal drinking water 2 0

Fibre glass cover ^_l 0

Trailer body l 0

Stainless steel sink ^.1 0

PVC pipe 1 0

Garbage bin 1 0

Swimming pool 1 0

Bottles .1 0

Washing machine 1 1 1

• Saucepan .1 0

Refrigerator crisper _l ₀

Metal tray l .1 1

Baking dish .1 0

TOTALS 107 31 21 1 2 .1 .10 3

" Type of container No of No of No 'of containers positive for each species

with water times times

container larvae Aedes notoscriptus Culex halifaxii recorded present

Tyres l l 5 4 1

Drums (_44gal etc). 3 .1 1

Garbage bins 3 0

Paint tins 2 l .1

Chlorine container 1 0

Dish 1 0

Bucket .1 0

TOTALS 22 7 6 1

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TABLE 5 ^CO. ,TRAP COLLECTIONS ADELAIDE RIVER - APRIL, .1983 - J

NUMBER OF FEMALE MOSQUITOES CAUGHT IN ONE TRAP IN ONE

WCATION DATE

..

SPECIES COLLECTED

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9 Becker Street 27/4/83 ^l 1 .13

Teachers house ^II 3 l ^l

War cernetary ^II l2 8

Adjacent to road through flood

plain - 2.3km south of town ^II 1 5 1 9

Sewerage Ponds ^II 3 1 5 3

Showgrounds 3 l 4 12 13 14

TOTALS 6 2 22 22 14 27 22

NIGHT

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TABLE 6 CO

2 TRAP COLLECTIONS - PINE CREEK - 28th APRIL, 1983 NUMBER OF FEMALE MOSQUITOES CAUGHT IN ONE TRAP IN ONE NIGHT

LOCATION DATE SPECIES COLLECTED

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Transport company 28/4/83 2 5 1 1 2 5 24 1 3 44

yard on W side of highway, approx 1km

from township

Adjacent to creek, 28/4/83 1 6 1 2 .19 71 2 102

~km north side of township

Rear of Ah Toy's 28/4/83 13 9 35 16 1 1 1 76

store, Railway Tee.

School yard 28/4/83 .1 1 12 22 44 3 3 86

Contractor's yard, 28/4/83 3 .1 5 .1 1 7 9 114 3 144

100m S of township.

Sewerage Ponds,approx.28/4/83 1 8 30 9 1 1 11 4 299 1 1 366

2.3km E of township.

TOTALS 2 5 9 36 21 1 2 28 2 1 20 68 587 1 25 2 7 1 818

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TABLE 7

CO2 TRAP COLLECTIONS - DALY RIVER - 29 APRIL, 1983 NUMBER OF FEMALE MOSQUITOES CAUGHT IN ONE TRAP IN ONE NIGHT -

WCATION DATE SPECIES COLLECTED

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RIVER CROSSING AREA ^Ul _Ul ^C

Riverbank, between 29/4/83 88 2 2 l 12 17 208 18 1 21 370

Mission & Fairweather's motel.

Riverbank, adjacent to 29/4/83 ll2 2 2 2 4 ^{74 90 4 290}

road to river crq?sing.

Adjacent to entrance to 29/4/83 122 16 3 26 1 1 2 124 1 11 1 .12 3 323

accomodation (formerly Health flats)

MISSION AREA

On river bank adjacent 29/4/83 10 1 3 7 3 2 220 1 .12 14 273

to convent

Swamp adjacent to mission, 29/4/8.3 30 10 .10 14 2 5 270 2 10 353

at end of airstrip.

Swamp area, approx 1km 29/4/83 6 9 l l3 2 1 70 2 16 12 132

E of corrununity.

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TOTALS 368 38 _l9 63 6 18 1 1 26 966 6 _147 4 2 69 3 1741 ..( ⁽

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