Mosquito control Groote Eylandt, 1982

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Northern Territory Department of Health Library Services Historical Collection

NORTHERN TERRITORY DEPARTMENT OF HEALTH MEDICAL ENTOMOLOGY SECTION

Mosquito Control Groote Eylandt 1982

HISTORICAL COLLECTION

1.0 Introduction

The findings of the recent mosquito survey on Groote Eylandt are outlined in the Medical Entomology Section Report "Aedes aegypti Survey of Groote Eylandt January 1981¹¹• The report confirms the absence of Aedes aegypti from the three communities on Groote Eylandt but highlighted problems from other vector mosquitoes.

2.0 Aedes aegypti and the potential for dengue transmission Al though no Aedes aegypti mosquitoes were detected on Groote Eylandt there was a high proportion of Aedes katherinensis larvae found in containers in all three communities. Al though i t is not known whether Aedes katherinensis can act as a vector under natural conditions, evidence to date suggests that Aedes katherinensis can transmit dengue virus under laboratory conditions. Groote Eylandt currently has the highest potential of any town in the Northern Territory for dengue transmission to occur. It is considered that a public education program is needed immediately to aid in a campaign to remove all water holding containers around all communities on Groote Eylandt that could contribute to the breeding of this species of vector mosquito.

3.0 Aedes vigilax (the salt marsh mosquito)

4.0

DL HIST 614.4323 DAV 1982

Aedes vigilax appears to be the principal pest and disease vector mosquito affecting Alyangula. There is still a need to investigate Connexion Island and Little Paradise Swamp a few days after the highest tides· in October and November to determine if these areas are in fact sources of this mosquito. The recent establish- ment of a regular carbon dioxide baited mosquito

trapping program at Alyangula by the Heal th Surveyor may add information towards solving this problem. If the breeding sites can be pin-pointed, i t may be a relatively simple matter to apply larvicides to the actual breeding areas before adult mosquito emergence occurs.

Mosquito Fogging

Recent mos qui to monitoring carried out by the Heal th Surveyor on Groote Eylandt indicates that there is no need to conduct fogging operations around Alyangula except at infrequent intervals. The decision on when to fog and the duration of fogging should be determined

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by a mosquito monitoring program. It is expected that the fogging will be needed around Alyangula from October to January to cope with Aedes vigilax plagues, but these plagues usually only last for a week, so self protection measures can play a large part in reducing man/mosquito vector contact.

Peter Whelan

Senior Medical Entomologist NT Department of Health

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AEDES AEGYPTI SURVEY OF GROOTE EYLANDT, JANUARY 1981

INTRODUCTION

MEDICAL ENTOMOLOGY SECTION

NORTHERN TERRITORY DEPARTMENT OF HEALTH

A survey of container breeding mosquitoes was conducted in three communities on Groote Eylandt over the period January 21-23, 1981 to check for the presence of the dengue vector Aedes aegypti.

Communities visited were the G.E.M.C.O. town, Alyangula and the aboriginal communities at Umbakumba and Angurugu.

METHOD

Selected premises within the communities were searched for containers holding mosquito breeding. These containers were sampled for mature specimens of each of the different looking larvae present. Specimens were preserved in 80% alcohol and returned to the laboratory for identification.

Man-bi ting catches and carbon-dioxode (CO_{2 )} baited traps were used to supplement this container breeding survey in Alyangula.

RESULTS

Results of the container breeding survey are displayed in Tables 1 and 2. Within the three communities a total of 164 containers holding water were detected and sampled. Fifty-six (56) of these held mosquito breeding representing 9 species.

Ae. aegypti larvae were not detected in any of the containers.

Results for the CO₂ trap collections and man-biting catches conducted in Alyangula are displayed in Tables 3 and 4. No adults of Ae.aegypti were collected by either of these methods.

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DISCUSSION

1. Aedes aegYPti Survey

The survey was conducted during the wet season when suitable breeding sites were available for container breeding mosquitoes such as Ae.aegYPti. Other mosquitoes that utilise similar breeding sites as Ae.aegYPti, notably Ae.katherinensis and Ae.tremulus were commonly detected in the container breeding survey. Hence if Ae. aegYPti was breeding in any of the communities visited then i t is likely i t would have been detected. The results indicate Ae.aegYPti is absent from the communities visited.

The most commonly collected container breeding species were Ae. katherinensis and ex. quinquefasciatus. Similar surveys conducted in the top end of the Northern Territory most commonly detect Ae.notoscriptus and Cx.quinquefasicatus. It would appear that on Groote Eylandt Ae.katherinensis, occupies the niche usually used by Ae.notoscriptus .

Ae.katherinensis is a member of the scutellaris group and in view of the proven ability of a number of members of this group to transmit dengue virus, the question arises as to the potential of Ae.katherinensis to also act as a vector.

As yet studies to determine the vector competence of Ae.katherinensis are incomplete.

The recent outbreaks of dengue in Queensland (earliest notfication in C .D. I. 82/4) highlight the need for such studies.

If Ae. katherinensis is demonstrated as a vector of dengue virus, in the laboratory, then the high prevalence of this species in the communities visited may mean a risk of dengue transmission if this virus was imported onto the island.

There are many other important features of a potential vector, apart from the ability to transmit virus, that must be assessed before i t can be assumed to be a significant potential vector. Such features include:

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(1) the tendency of Ae.katherinensis to enter houses (2) whether i t is anthropophilic

(3) longevity of the mosquito

These features will need assessing if Ae. katherinensis is shown to be competent of transmitting dengue virus.

Other Species

2.1 Aedes vigilax "The Salt Marsh Mosquito"

At the time of the survey plague numbers of the salt marsh mosquito (Ae.vigilax) were present in Alyangula and the prawn base at Bartalumba Bay. The collection of day-biting specimens in Angurugu suggests that plague numbers were also present in this area.

Three CO₂ sites, all separated by at least 2km, collected similar numbers of Ae.vigilax (approximately 800/900) . The sites were near t he Alyangula Heal th Centre, near the turn-off to Bartalumba Bay and near Bartalumba Bay ( See figure 1). For this fairly even distribution of numbers to occur, the Ae.vigilax adults would most likely be spreading into the area from relatively distant breeding site/s.

Traditionally, Connexion Island (about 5km NW of Alyangula) has been thought to be the source of these plagues and yearly scrub burns have been conducted on this island in an effort to reduce the size of the plagues affecting Alyangula. If Connexion Island is the principal source of these plagues then the prevailing NW breezes of the early wet season would aid

in the dispersal of the mosquito towards Alyangula.

A search of potential breeding sites on the island, following spring tides or heavy rainfall, is needed to determine if large suitable breeding sites for this species are present. Sites worth examining are evident

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from aerial photographs. These distant breeding sites could also be on Groote Eylandt its elf and similar searches of potential breeding sites, as mentioned above, are necessary to identify the source of these

• plagues.

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2.2 Culex sitiens ¹¹The Salt Water Culex Mosquito¹¹

The numbers of Cx.sitiens collected in the CO₂ traps in Alyangula indicate the presence of an as yet undiscovered brackish water breeding site nearby.

2.3 Culex annulirostris ¹¹Common Banded Mosquito¹¹

The numbers of this species collected in the CO₂ trap in the creek line near the shops in Alyangula indicates a nearby breeding site. This is most likely to be the lower reaches of the creek where it runs along a boundary of the golf course. The creek receives run- off from the watering of the golf course greens. The mouth of the creek is usually blocked by dunes making these pools in the lower reaches semi-permanent in the dry season. Natural control of any mosquito breeding in these waters by fish would be promoted if the pools were joined and they were kept free of debris that would provide harbourage for mosquito larvae.

CONCLUSIONS

(1) Ae.aegypti appears to be absent from Groote Eylandt.

( 2) Ae. katherinensis was the most commonly collected container breeding species.

There may be a risk of dengue virus transmission if this virus was brought to the island, because this species is closely related to known vectors of this disease.

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( 3) Plagues of Ae. vigil ax influencing Alyangula may be coming from distant breeding sites. Possible breeding sites may be on Connnexion Island or Groote Eylandt .

G. Davis

W. Kelton

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Table 1

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Aedes aegypti SURVEY GROOTE EYLANDT JANUARY 1981

LOCATION OF SOURCE

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!Location Number of Number of Number of Number of Species IncidencE a.nd Date Premises Premises Containers Containers·

.:3ea.rched Examined with With Water With

Breeding Lar~1ae ^{~ ~ ~} :i:::i :i:::i n n n 8

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rt rt 0 ^(D !:J !:J ^{I--' f-'·} :::l ::r' 0 ::r' s C C I-'· :::l 0

(D Ul ... _C I--' I--' ^H, i..o rt

t1 0 I--' ... f-'· p, C 0

I-'· ~ C 'U ~ X ^(D I--'

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Alyangula 65 11 50 16 8 1 ll 2 2 5 2

2~/1/81

Umbakumba 28 7 46 15 6 ii 1 2 4

Mission 21/1/81

Angurugu 21 12 68 25 14 5 l l l 13

Mission 22/1/81

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~rOTALS ll4 30 164 56 28 6 1 8 1 4 ^{2 20 6}

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Table 2

Aedes aegypti SURVEY GROOTE EYLANDT JANUARY 1981

Premises Examined

ALYANGULA 23/1/1981

6 streets chosen at random, 65 premises searched.

34 containers with nil breeding.

Dry dump

UMBAKUMBA MISSION 21/1/1981

Housing Association yard

No.

1 1 1 1 1 1 1 1 1

2 1 1 1 2

1 2 1 1 1 1

NATURE OF SOURCE

Containers with Water Type

small aluminium cont.

with plant cuttings ice-cream container esky

foam packaging plastic bucket 5 gall. drum with plant cuttings ornamental pond (no fish) algae, grass plastic bucket

\ of 44 gall. drum under tree, organic matter

sea shells in garden, organic matter

metal bucket engine casting

\ of 44 gall. drum, organic matter truck tyres

galvanised roofing iron car tyres

car tyre wheelbaJ::i'row cement mixer

shallow metal tank

Species of Larvae

Cx. quinquefasciatus Ae. katherinensis Cx. quinquefasciatus Ae. katherinensis Ae. notoscriptus Ae. katherinensis Ae. tremulus

Cx. quinquefasciatus Cx. halifaxii

Cx. annulirostris Cx. quinquefasciatus Cx. halifaxii

Cx. quinquefasciatus Cx. annulirostris Ae. katherinensis Ae. katherinensis Ae. katherinensis Ae. katherinensis Tr. punctolateralis

Ae. tremulus

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Table 2 (cont)

Premises Examined

Dry dump

Nurses quarters

Community area (23 houses)

roadside on way to Umbakumba

ANGURUGU MISSION 22/1/1981

Mechanics yard

No .

3 5 2 7 1 2

4

1 1

1 1 3

1 1 2 1 1 1 1

3 4 17 5

2

1 1

2

Containers with Water Species of Larvae

washing machines vehicle tyres

vehicle tyres Ae. tremulus various tins

paint tin Ae. katherinensis vehicle bodies

vehicle bodies (3) Ae. tremulus (2) Ae katherinensis (2) Tr. punctolateralis 4 gall. tin

44 gall. drum set in ground

esky, polluted water open sewage inspection hole, clean water rainwater tanks, screened

unused washing machine ice-cream container saucepans, polluted water

5 gall. tine vehicle hub cap car tyre

vehicle body

vehicle bodies vehicle bodies vehicle tyres vehicle tyres tins

vehicle hub cap 5 gall. drum

(2) (2)

(4) (3)

Ae. katherinensis Ae. tremulus

Cx. quinquefasicatus Cx. quinquefasicatus Cx. annulirostris

Ae. katherinensis

Tr. punctolateralis Ae. katherinensis Tr. punctolateralis

Ae. katherinensis Cx. quinquefasciatus

Cx. quinquefasciatus Ae. katherinensis Ae. katherinensis Cx. quinquefasciatus

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Table 2 (cont)

Premises Examined

Teachers houses (5)

Administration houses (2)

Aboriginal housing (10 houses)

on roadside, track from Angurugu to Yambugwa

TOTALS

No.

8 1 1 3 2 2 1 1 1 1 1 1

1

1 1 3 2 1 1 1

1

3

Containers with Water Type

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over-full pot plants over-full pot plant bath, beneath tree

ice-cream containers vehicle tyres

glass jars with cuttings

fish pond (no fish) algae, organic matter ice-cream container esky

paint tin

metal wash bucket water bowl in fowl yard

ice-cream container with cuttings

vehicle tyre vehicle tyre

saucepans, polluted water

ice-cream containers metal bucket

5 gall. drum plastic bucket

large truck tyre in open forest

Species of Larvae

Ae. katherinensis Ae. notoscriptus Ae. katherinensis

Cx. quinquefasciatus Cx. annulirostris Ae. katherinensis Ae. notoscriptus Ae. katherinensis Ae. notoscriptus Ae. katherinensis Cx. quinquefasicatus

Cx. katherinensi~

Cx. quinquefasciatus Cx. quinquefasicatus

Cx. quinquefasciatus Ae. notoscriptus Ae. notoscriptus Ae. katherinensis Ae katherinensis An. annulipes Ae kochi

(x): number of times species recorded 114

30 164 56 9

Premises' examined

Premises with mosquito breeding Containers holding water

Containers with mosquito breeding Species represented

Table 3 Aedes aegypti SURVEY GROOTE EYLANDT, JANUARY 1981 Number of female mosquitoes caught in one trap in one night

SPECIES

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Alyangula, in scrub adjacent

to health centre 20 .i.1981 1 1 1 1

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A:Lyangula, in scrub on creek

line near shops 20 .i.1981 1 13 25 1

In scrub adjacent to Rowell

Hwy lOOm before turn-off to 20.i.1981 4 10

Bartalumba Bay (7)

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Near Bartalumba Bay - track on 20 .i.1981 3 2 3 1 0

LHS of road ~km before bay (5)

i\lyangula, rear year No. 10 21.i.1981 10

Tasman Street

i\lyangula, rear year No. 10

Tasman Street 22.i.1981 3

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540

92.5

800

400

226

CO2 TRAP COLLECTIONS (x) : number of males

COLLECTED

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TABLE 4 Aedes ~egypti SURVEY GROOTE EYLANDT, JANUARY 1981 MAN-BITING COLLECTIONS

Number of female mosquitoes collected by 2 collectors, in the time given

LOCATION DATE TIME SPECIES COLLECED

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Near Baralumba bay - track on 19/1/1981 1935-1938 127 1 2 LHS of road ~km before bay

Alyangula, in scrub on creek

line near shops 19/1/1981 2000-2005 1 .142 1 2

Alyangula, in scrub at corner

of Poinciana and Smith Streets 19/1/1981 2010-2015 148 2 Alyangula, in scrub at corner

of Poinciana and Smith Streets 22/1/1981 1935-1945 106 10 ²

Anglirugu, rear yard of house in One Collector

administration area 22/1/1981 Approx 1040

Hours 4

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