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Northern Territory Department of Health Library Services Historical Collection

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MOSQUITO SURVEY - LAJAMANU, KALKARINDJI AND DAGARAGU

JULY - AUGUST 1985

DL HIST 595.772 SMI 1985

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HISTORICAL COLLECTION

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MOSQUITO SURVEY - LAJAMANU, KALKARINDJI AND DAGARAGU July - August 1985

Medical Entomology Branch - N.T. Department of Health

1.0 INTRODUCTION

In response to a request from the Department of Transport and Works to evaluate the mosquito breeding situation at the aboriginal community of Lajamanu, approximately 650 km South of Darwin, prior to the upgrading of the sewerage ponds there, two officers from the Medical Entomology Branch of the N.T. Department of Health visited the community in late July 1985. Whilst in the area, two other aboriginal communities, Kalkarindji and Dagaragu approximately 100 km North of Lajamanu were visited to assess the current mosquito situation. Mosquito surveys had not been conducted in these communities since the last visit by personell of the Medical Entomology Branch during March 1981.

2.0 SURVEY METHODS 2.1 Adult mosquitoes

2. 2

To determine the species present and their relative numbers at each community, 5 CO2-baited traps were placed at appropriate sites near Lajamanu during the night of 30/31 July and a further 7 were placed near the other communities the following night. The locations of these trap sites are shown in Table IA and on Maps 1 and 2. Adults collected were identified and representative specimens pinned for retention.

Larval breeding sites

Using ladles, likely breeding places were surveyed to determine the actual breeding sites of mosquitoes in the area. These places included the local sewerage ponds, any areas of standing water and containers, tanks or septic systems in or around the communities.

2.3 Inspection of sewerage and water systems

In order to assess the current status of the sewerage systems, the sewerage ponds were examined at each community. In addi t ion, the private and public septic systems, rainwater tanks and water reticulation points were inspected for mosquito breeding in the Kalkarindji and Dagaragu communities.

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3.0 RESULTS

3.1 CO2-trap catches

The CO2-baited trap catches indicated that four species, namely Anopheles amictus (Lajamanu only), An. annulipes, Culex annulirostris 'gp' and Cx. guinguefasciatus were breeding in appreciable numbers near the communities. A further four species were collected in very low numbers as shown in Table I. However, catches were quite low and six of the 11 traps captured 30 or less mosquitoes overnight . Overall, Cx. guinguefasciatus was the most commonly trapped species, accounting for 38% of the total catch although the incidence varied from 14% at Lajamanu and 34% at Dagaragu to 89% at Kalkarindji.

An. amictus provided 32% of the total catch although it was trapped only at Lajamanu, where it made up 65% of the specimens collected. An. annulipes, with 19% of the total catch was most frequent (62% of catch) at Dagaragu.

3.2 Larval breeding sites

At Lajamanu, 11 positive larval sites were sampled and all the main species represented in the CO2-trap catches were reared through from larval stage. In addition, Cx. starkeae larvae were collected from green algal mats · floating in a large pool ( 15m diam.) caused by ponding of overflow from the overhead tanks in the community.

Four samples at Kalkarindji produced larvae of the four main species collected as adults and a larval collection at Wattie Creek showed that An. annulipes

r and Cx. annulirostris were breeding in the billabong to the South of Dagaragu. Details of these collections are listed in Table II.

3.3 Inspection of sewage and water systems

3.3.1. Lajamanu. This community has been on a sewerage system since 1970 and all houses are connected. The police station, NW of the airstrip has three septics which are connected by a separate pump to the sewer line. The ponds are situated approx. 1.2 km E of the main store and 200 m S of the E end of the airstrip.

Two primary ponds in parallel feed effluent to a larger secondary pond and the overflow is directed into a channel running roughly NE for a distance of about 3 km. At the time of the visit, effluent was flowing out at approx. 0.75 litres/second and running along the channel for a distance of about 1.5 km. However, a mob of 10~15 horses had broken the raised channel bank in several places along this length and caused very large areas of lateral sewage spread. The first of these occurred about 300 m from the ponds and effluent flowed in a SE direction for 200-300 m to eventually pool and fill borrow pits near a rubbish dump. Larval breeding was detected in the North primary and the secondary ponds and in most points of the outflow channel and lateral

seepage areas.

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The following notes on the Lajamanu sewage ponds were made:

(1) The main gate in the Western fence was open and had allowed horses and humans ready access

(2) The side gate in the Eastern fence directly above the outflow was open

(3) A large hole had been .£ut in the South fence and an unsuccessful attempt had been made to fix i t

(4) A hole in the NW corner of the fence had been fixed but a further two holes in the vicinity allowed access under the fence.

(5) Couch grass was growing around the margins of the three ponds and the outflow channel. Shrubby regrowth had been chopped back but further clearing was necessary at the time of the visit.

Although some rainwater tanks in the community and the police station were unscreened, no mosquito larvae were found in these tanks. Cx.

quinquefasciatus larvae were found in an old refrigerator body at a house near the airstrip and in an underground concrete tank l.2xl.2x0.5m deep in front of the church in the centre of the community (larval sites 7 and 11, Table II) .

On the South side of the community, continuous water flowing from the overhead tanks supplying the community with reticulated water had pooled into a large breeding area behind the workshop buildings.

One large (15m diam.) pool overflowed to a series of shallow, couch filled pools and the overflow extended in both a SE and SW direction for 400m, almost to Hooker Creek. This provided a large breeding area for mosquitoes close to the community.

Several muddy pools on the nearby Hooker Creek were not sampled but were unlikely to have produced large numbers of mosquitoes, although it was probably a

significant source of An. amictus.

3.3.2. Kalkarindji. This community runs a septic system but many tanks required attention and Cx.

guinguefasciatus breeding in the septics was common and created a considerable mosquito problem in the community. In a survey of 35 septics, 13 were in need of repair or maintainence and 9 had larvae (Table III). The sewage ponds on the SW side of the community consist of four ponds in series but only the first three were in use. The fourth pond was at that time dry, but outflowed to a creek. The primary pond (Westernmost) had considerable couch growth along the margin and a small amount of scrubby regrowth. Most larvae collected were sheltering in the couch margin. The secondary and tertiary ponds were less grassed at the edge and had fewer larvae. Although there was no outflow from the ponds, the creek into which the outflow would run contained several small remnant pools. One at the road bridge, about 50m from the outflow entry pipe produced large numbers of An. annulipes and Cx.

annulirostris (larval site 14, Table II).

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The majority of rainwater tanks were screened and mosquito breeding in these tanks was low. Results from this survey are shown in Table III.

As at Lajamanu, the overhead tanks to supply Kalkaringji community were almost continuously overflowing and run-off eventually reached the nearby Victoria River via a small creek through the houses and to the SW of the community. A small amount of Cx. annulirostris breeding occurred in this water (site 15, Table II) .

3.3.3. Dagaragu. Most of this community is serviced by communal ablution and washing blocks which are sewered and few houses remain on a septic system. The ponds, about 0.7 km E of the community are well formalised with bituminous sheeting borders. At the time of the visit, only the primary pond was in use and the secondary pond was dry. The outflow had probably never run. The bituminous sheeting was placed above the then present level of effluent and was also too high for the outflow pipe to the secondary pond. A small amount of vegetation growing above and below this sheeting was noted. Very little breeding was occurring in the pond.

Within the community, two toilet blocks had broken septic lids and were breeding Cx. guinguefasciatus (larvae could not be sampled but numerous adults were noted) while a further toilet block was in good repair. Of four house septics, one was dry, two were undamaged and the last was breeding brown house mosquitoes. In addition, two pools, one from a

leaking fire hydrant near the health centre and another from a leaking tap in the central playground contained Cx. annulirostris larvae (larval site 17, Table I I ) . -

Larvae of both An. annulipes and Cx. annulirostris were found at the edge of a large billabong in Wattie Creek, to the South of the community.

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-5- DISCUSSION

A discussion of the communities and the biology and pest status of the more common mosquito species in this area was presented in the report of the survey conducted by the Medical Entomology Branch during March 1981. The recent sqrvey collected three species, Cx. australicus, Cx. starkeae and Aedeomyia catasticta, which had not previously been recorded from the area and increased the species list from the Victoria River area to 26 mosquitoes (Appendix).

4.1 Vector mosquitoes

Significant numbers of four mosquitoes, An.

annulipes, An. amictus, Cx. annulirostris and Cx.

guinguefasciatus were recorded during this survey, and Ae. normanensis had been reported in an earlier survey (March 1981). All five species are potential disease vectors and since few houses were mosquito proofed, the majority of the population could be exposed to mosquito attack and possible disease (malaria and arbovirus) transmission. Although the likelihood of malaria transmission is low, the two Anophelines are potential vectors of the disease and cases did occur in the area during 1921, 1933, 1934 and 1957 before malaria was eradicated in the Northern Territory. Cx. annulirostris is a known vector of several arboviruses, Ae. normanensis can transmit epidemic polyarthritis and Cx.

guinguefasciatus, although not known as a vector of human disease in the Northern Territory, is an important pest species and a vector of dog heartworm.

4.2 Lajamanu

The survey indicated that two main areas of breeding occurred around the community. The sewage ponds and associated outflow had created conditions for the breeding of An. amictus, An. annulipes, Cx.

australicus and Cx. guinguefasciatus, while the fresh water ponding to the South of the community encouraged breeding by these species in addition to Cx. annulirostris and Cx. starkeae.

The Anophelines were probably also breeding in remnant pools along Hooker Creek since larvae had previously been collected from there. An. amictus, which typically breeds in drying remnant pools, was recorded only at Lajamanu, whi:ch indicates that this country further North near the Victoria River.

As yet, there is no evidence that that Cx. starkeae attacks humans and this may be the reason why this species was not collected in CO2-baited traps .

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During a previous survey at Lajamanu in March 1981, the principal nuisance species was Ae. normanensis, which breeds in shallow, sunlit, temporary rain filled pools. As the recent visit was made at least three months after rain, no specimens were collected and it is very unlikely that this species would breed in the "semi-permanent·~-water areas found at

this time.

The proposed redesigning of the sewage ponds and effluent disposal by spray irrigation should greatly reduce the potential for mosquito breeding in that area, but the ponding of overflow from the overhead water tanks will continue to allow breeding of pest species adjacent to the community. It should be possible to arrange time clocks on the pumps to keep the reticulation supply topped up without overflowing and replenishing these breeding areas.

4.3 Kalkarindji

Poorly maintained septics produced the main source of mosquitoes in this community and 89% of the total catch consisted of Cx. guinguefasciatus. The majority of the total catch occurred in trap 2, set at the council office near the large, broken septic tank of a communal toilet block. The proposed reconstruction of the sewage ponds and elimination of septic tanks should greatly reduce the Cx.

guinguefasciatus problem. However, the design and maintainence of these ponds will be a large factor in lowering the numbers of Cx. annulirostris. The ponds should be constructed to provide: (1) impervious sides (2) a relatively small final pond (3) the prevention of excess effluent release into creek systems (4) effluent dispersal by sprinkler irrigation (5) no ponding of this dispersed effluent for longer than four days.

An. annulipes and Cx. annulirostris were found breeding in the effluent creek to the SW of the community and the anopheline was probably breeding in remnant pools of the Victoria River to the East.

The supply to the overhead water reticulation tanks should be arranged to prevent ponding of overflow and associated mosquito breeding, although this was causing only minor problems during this visit.

4.4 Dagaragu

Trapping results here indicate that the main source of mosquitoes was from Wattie Creek, although the damaged septics would produce most of the Cx.

guinguefasciatus trapped and the pooling around the fire hydrant and the playground tap allowed some An.

annulipes and Cx. annulirostris breeding .

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5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 Due to its absence at the last survey (March 1981) and to the lack of water filled containers during the dry season, it is very unlikely that Ae. aegypti is present or will become established in these communities.

5.2 Sewage ponds in all communities should be maintained weed-free and in good condition. This can be achieved by the present system of period contracts with Transport and Works Department inspections possibly being more frequent and stringent. Fences should be repaired to prevent humans and other animals entering the enclosures and the access gates should be kept locked.

5.3 The upgrading of the Lajamanu sewage ponds with the associated sprinkler irrigation system should greatly reduce breeding of pest mosquitoes in the area to the West of the community.

5.4 Pooling of fresh water to the South of the workshop area at Lajamanu promotes breeding of potential disease vectors close to the community. This situation should be rectified as soon as possible by preventing the tanks from overflowing.

5.5 Generally, little breeding within the Lajamanu community was found, although the pit area near the church should be filled to prevent accidents and the breeding of Cx. guinguefasciatus.

5.6 As recommended after the March 1981 survey, the breeding sites of Ae. normanensis located near the Lajamanu community should be rectified by in-filling or ensuring that they are free draining.

5.7 At Kalkarindji, many of the septics require repair to prevent mosquito breeding. The systems should be regularly checked to ensure they are well sealed and operating efficiently. The proposed upgrading of the sewage system should eliminate much of this problem if it follows the guidelines outlined in 4.3 above . 5.8 Overflow from the reticulation system at Kalkarindji

should be stopped to eliminate mosquito breeding in the resultant pooling.

5.9 Pooling in the creekline to the South of the Kalkarindji sewage ponds and especially near the road bridge could be prevented by small scale filling to formalise the area and reduce significant mosquito breeding in the dry season. If necessary, chemical treatment using temaphos (Abate (R)) could be used.

5.10 The leaking fire hydrant and tap at Dagaragu should be repaired to prevent the small amount of breeding within the community.

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5.11 Since six pest species were recorded in containers at these communities during the earlier survey, receptacles which may hold water and create breeding sites for container breeding mosquitoes during the wet season should be removed or holed to allow drainage.

6.0 ACKNOWLEDGEMENTS

We are grateful for the assistance given to us by the Health Sisters at Lajamanu and Kalkarindji.

Local information was supplied by Jerry Jangala (Liason Councillor), Pat McGrath, Ian Chisholm and Bill Mill at Lajamanu and Michael Paddy (Liason Councillor), Jan Richardson, Les Jones and Stan Davey at the other communities.

E.S.C. Smith Technical Officer

A. Hancock

Technical Assistant P.I.Whelan

Senior Medical Entomologist

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Map 1. Locat1·ons of CO2 b · _{- a1} t _{ed traps} · · _{, set} near Lajamanu, July 1985

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Map 2. Locations of CO2-baited t~aps set near Oagaragu and Kalkarindji communities, August 1985

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Table IA. Locations of CO2-baited mosquito traps set near Lajamanu, Kalkarindji and Dagaragu.

Lajamanu - night of 30/31 July 1985 1.

2.

Sewage pond outflow. Approx. 250m NE of ponds near first break in channel and lateral effluent soakage area

Approx. halfway between seKage ponds and community, 20m N of road. 600m R of ponds, 600m E of Heal th Clinic 300m NE of pensioner's camp

3. Heal th Clinic, in front of flats

4. Centre of community at house of plumber, opposite store 5. Hooker Creek. Behind Council Offices, near roadway and at

edge of large pool 50 x 4 m

Dagaragu - night of 31 July/ 01 August 1985 1 . Hattie Creek.

SR of bore

Bank of creek at SE corner of community, 50m

2. Centre of community, Michael Paddy's house

3. Rat tie Creek. 1 OOm E of road crossing before community and approx. 1 50m SR of high level water tank

Kalkarindji - night of 31 July/ 01 August 1985

1. Victoria River. 150m upstream from road bridge on bank of drying billabong

2. Under tamarind tree at house on N side of Council offices 3. Rear of house #3 on R side of community and occupied by

plumber

4. 50m downstream from main road along creekline created from overfloK of overhead tanks, betKeen Health Centre and seKage ponds

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TABLE I. Mosquito survey Lajamanu, Dagaragu and Kalkarindji - July/August 1985 Numbers of female mosquitoes caught in one trapping night

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SPECIES I LAJAHANU DAGARAGU

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I 2 3 4 5 SUH 2 3 SUH

An. amictus 77 1 81 5 11 23 297

An. annulipes 4 16 21 57 87 144

Ae. bancroftianus

Cx. annulirostris • gp' 1 2 22 2 6 31 73 2 4 6

Cx. australicus 3 3

Cx. quinquefasciatus 38 1 0 1 2 3 63 76 3 79

Ad. catasticta Tr. punctolateralis

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TOTALS I 130 217 7 30 74 458 137 3 92 232

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KALKARINDJI

1 2 3 4

7 5 2

2 7

2

4 174 25 10

1 2 183 27 19

SUH

14

11

2

21 3

241

TOTAL

297 179

90 6

355

2

1

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Site No.

2

3

4

5

6

7

8

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9

1 0

11

1 2

1 3

14

1 5

1 6

1 7

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TABLE II. Mosquito species reared from larvae collected at breeding sites near the three communities surveyed

Community Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Lajamanu

Kalkarindji

Kalkarindji

Kalkarindji

Kalkarindji

Dagaragu

Dagaragu

Species collected Cx. australicus Cx. quinquefasciatu~

An. amictus

Cx. quinquefasciatus Cx. quinquefasciatus

ex. quinquefasciatus

An. annulipes Cx. australicus Cx. quinquefasciatus Cx. australicus Cx. quinquefasciatus

Cx. quinquefasciatus

Cx. annulirostris

Cx. annulirostris Cx. quinquefasciatus Cx. starkeae

An. amictus

Cx. annulirostris Cx. australicus Cx. quinquefasciatus ex. quinquefasciatus

Cx. annulirostris Cx. australicus Cx. quinquefasciatus An. annulipes

Cx. annulirostris Cx. quinquefasciatus An. annulipes

Cx. annulirostris Cx. annulirostris

An. annulipes Cx. annulirostris Cx. annulirostris

Breeding site

Primary sewage pond, North side

Secondary sewage pond

Sewerage outflow channel, 50-100 m NE of ponds

Sewerage outflow channel, 150-200 m NE of ponds

Near break in sewerage outflow channel, 250-270m NE of ponds

Sewerage outflow, approx 400m SE of ponds nr. rubbish and borrow pits

Old refridgerator body in house opposite airstrip

Ponding behind workshop area of overflow from high watertank. In couchgrass margin of large (15 m diam) pool

As above, in floating mats of green algae

As above, in shallow pools with extensive couch growth

Concrete pit, 1. 2 x 1. 2 x 0. 5 m in front of church

Primary sewage ponds

Secondary sewage ponds

Pool in creek at roadbridge 100m E of sewage outflow point Creek formed by overflow from overhead tanks in community Hattie Ck. Edge of billabong to S of community

Pooling at leaking fire hydrant Pooling beneath leaking tap

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TABLE III. Survey of septic systems at Kalkarindji community, July 1985

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Residence or Lot j~ I

43 54 55 53 52 51 50 49 48 47 46 44 1 5 1 6 1 2 1 1 1 7 42 26 27 41 23B

Old council office 58, Health flats 34, Health Centre

37 38 39 31 32 33

63, Public toilet 64, Shell Service

68, Church Council house

Septic OK Open

OK OK OK Lid removed

OK OK OK OK OK OK Open, dry

Open OK OK Open Open, dry

OK

Open, overflowing OK

OK Open, broken

OK OK Broken lid

OK

Nearly dry, lid broken OK

OK

No solid cover (tin) No cover, high adult I

OK OK

One OK;One dry, open

Larval numbers/ladle

>30

>100

> 30

>30

Nil,(Eristalis larvae)

>50

>30

>30

> 30 Not sampled

Rainwater tanks Screened

Unscreened, low I

Unscreened, low I

Screened Screened

Screened

Other breeding sites

Blocked drain, -ve

Dripping tap, -ve

Duck pond, -ve

Swimming pool with fish. Low numbers

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APPENDIX

List of mosquito species recorded from three aboriginal communities in the Victoria River Area Medical Entomology Branch - Northern Territory Department of Health

SPECIES I LAJAMANU DAGARAGU KALKARINDJI

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I MARCH 1981 JULY 1985 MARCH 1 981 JULY 1985 MARCH 1 981 JULY 1985 I ADULT LARVAE ADULT LARVAE ADULT LARVAE ADULT LARVAE ADULT LARVAE ADULT LARVAE --- ---

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An. amictus X X X X X X

An. annulipes X X X X X X X X X X X

An. meraukensis X X

An. novaguinensis X

Ae. alternans X X

Ae. bancroftianus X X X

Ae. britteni X

Ae. eidsvoldensis X

Ae. katherinensis X

Ae. lineatopennis X X

Ae. normanensis X X X

Ae. notoscriptus ^X

Ae. tremulus X X

Ae. vigilax X X

Ae. ( Och) sp. X

Ae. sp. 71 X

Ae. sp. ? 1 59 X

Ae. sp. 160 X

Cx. annulirostris X X X X X X X X X X X X

Cx. australicus X X X X X

Cx. halifaxii ^X X

Cx. pullus X X X X X X

Cx. quinquefasciatus X X X X X X X X X X X ')

Cx. starkeae X

c·

Ad. catasticta X X \.l

Tr. punctolateralis X X

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