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Northern Territory Department of Health Library Services Historical Collection

1

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I 3 0820 00018836 2

NORTHEIU-J' TERRITORY DEPARTMENT OF HEATLH

-:)L 1-\'..:,T 6 t4 .4 32.3

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1~82.

MEDICAL ENTOMOLOGY HISTORICAL

COLLECTION MOSQUITO CONTROL RECOMMENDATIONS KATHERINE 1982

1.0 Introduction

·The current mos qui to breeding situation in Katherin·e is indicated in the attached report "Vector Mosquito · Survey Katherine 16-19 February 1982^{11 •} The report confirms that Katherine -is free of Aedes aegypti, a dengue mos qui to, but highlights the need for action to reduce the receptivity of Katherine to the reintroduction of this vector, as well as eliminating or controlling other important sources of vector mosquitoes.

2.0 Aedes aegypti

The Aedes aegypti survey has shown a relatively high number of container breeding mos qui toes in both industrial and residential areas. Tyres pose the greatest problem. There is a dengue outbreak in Queensland this year and Aedes aegypti appears to be common in many areas of Queensland, posing the threat of reintroducing the mos qui to and the disease to the Northern Territory. Apart from the heal th threat, the most numerous mosgui toes in the residential areas are those that are actually breeding in the residential areas. This indicates . a necessity for a public education program against container breeding mosgui toes. It is suggested that the Katherine Regional Office of the Department --of Health, in conjunction with the Health Education Northern Region, conduct a public education program against ~omestic mosquitoes.

3.0 Other Mosquito Breeding Areas

3.1 Katherine Sewerage Treatment Works

This area is now the major source of vector mosquitoes in Katherine and is in contrast to 1980 when the Katherine Abattoir area was by far the major contributor to high numbers of mosquitoes. The sewerage treatment works area is producing very high numbers of both Culex annulirostris and Aedes normanensis which are both vectors of human disease. The Katherine Abattoir area has shown a dramatic reduction in the number of mosquitoes and this is attributed to the large amount of engineering works carried out on the effluent treatment and dispersal, after discussions and advice from the Katherine Regional Health Surveyors and the Medical Entomology Section of Darwin. It now remains for the responsible authorities to rectify mos qui to breeding at the sewerage treatment works.

DL HIST 614.4323 HOD 1982

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3.2 The Katherine Dump Area

The dump area is poor draining in the Wet Season and i t is a result of back flooding on the Katherine River. The current survey- pinpoints the dump area as a major source of many mosquito species, including Culex annulirostris and Aedes normanensis.

Other surveys made during the year indicate that i t is also a major source of Anopheles bancroftii. .The. dump itself is a source of mosquitoes due to incorrect disposal of tyres and car bodies, but the major problem is the inadequately draining area. It is recommended that the findings of the Willing and Partners 1976 report, "Katherine Regional Stormwater Drainage Study", be implemented as soon as possible to rectify this problem area, as well as reducing the potential for serious flooding in the area.

3.3 The Katherine River

There are still minor sources of mos qui toes along the Katherine River in cutoff pools that do not drain back to the main river when the flood level recedes. It is reconunended that local authorities locate these remnant

f

pools and investigate the possiblity of draining them.

t

4.0 ~ u i t o Control

A Leco fogging machine has been handed over to the Katherine Heal th Surveyors with a view that i t can be used to reduce high numbers of mos qui toes if and when they reach very high levels or when an outbreak of mosquito borne disease occurs.

On a current inspection the fogging machine had operational problems which highlights the importance of regular mainten- ance on this machine in preparation for possible outbreaks of mosquito borne disease. The decision on whether to fog must be made on a mos qui to moni to.ring program and this would be best performed at the local level by the Heal th Surveyors.

There have been manpower problems in the past year in this monitoring program in Katherine and i t is hoped that adequate resources can be allocated to the program. For actually carrying out the fogging program there is no suitable access on the north side of the river or on the south side of river above the main bank near the abattoir, sewerage ponds and around the dumn area. It is recommended that areas for access along the top ~f the river banks on both sides be set aside by the planning authorities for future fogging operations. It is also recommended that local authorities investigate construct- ing basic access tracks in these areas. The Health Department Entomology Section is available for expertise and advice on any of the above points.

Peter Whelan

Senior Medical Entomologist

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-'-"fC.-'OU/,5

NORTHERN TERRITORY DEPARTMENT OF HEALTH

MEDICAL ENTOMOLOGY

VECTOR MOSQUITO SURVEY KATHERINE /6th - 19th FEBRUARY 1982

INTRODUCTION

Both an Ae.aegypti survey and vector mosquito survey were conducted in the Industrial and Residential areas of Katherine township between 16th and 19th February 1982, by two officers from the Medical Entomology Section of the Northern Territory Department of Health.

METHOD

A search for containers with water was made throughout premises, in the Katherine Residential and Industrial areas. Each container was recorded and sampled for mosquito larvae, using the normal method ie. tipping the contents of each container into a ladle for examination and collecting mature specimens of each of the different looking larvae present .

Carbon dioxide (CO_{2 )} baited traps were positioned at select places to capture adult mos qui toes. A total of 12 sites were selected ( see figure 1). Six within the residential area to check for the presence of Ae.aegypti and other nuisance and known vector mosquitoes. The other six were used to sample mosquito populations at known and suspected mosquito breeding areas near the town. The traps were put out in the early evening and retrieved shortly after sunrise th~ following morning. The catches were killed with chloroform and preserved for trans- mission back to Darwin for examination.

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RESULTS

A total of ninety-eight (98) premises were searched for containers in the Katherine township, producing 254 containers with water, 90 of which contained mos qui to breeding. Eight different species of mosquito larvae were collected. No larvae of Ae.aegypti were collected. A SU111ffiary of the container breeding search is given in Table 1. Table 2 lists the type of containers and the species of mosquito larvae found breeding in them. The result of the CO₂ baited light trap catches are presented in Table 3. Ae.aegypti was not collected in any of the CO₂ baited traps placed in the residential area.

DISCUSSION

1.0 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.notoscriptus and Cx.quinguefasciatus were commonly detected in the container survey. These species. were also detected in the CO₂ trap catches. Thus i t is iridicated that the community is free of Ae.aegypti.

The dominant container breeding species were Ae.notoscriptus and Cx.quinguefasciatus with only minor representations from the other six species.

Adults or larvae of Ae.katherinensis were not detected during this survey al though an a,dul t of this species was collected man-biting during a previous Ae.aegypti survey of February 1980.

Table 1 reveals a much higher incidence of containers with water in the industrial area, than in the residential area.

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3 000~~/ 5

Many of the premises in the industrial area have a connection with interstate transport from Queensland. The prevalence of suitable breeding sites in the industrial area suggest Ae. aegypti could establish itself quickly in this area if adults or eggs were impoEted from Queensland.

The most commonly detected containers with water were vehicle tyres and 63% of these held mosquito breeding. This indicates that tyres were the most important source of container breeding mosquitoes located.

The next most commonly detected containers with water, in order of frequency, were buckets, plastic containers and drums of various volumes.

The incidence of breeding in these containers was signifi- cantly less than that found in vehicle tyres holding water.

2.0 General Mosquito Survey 2.1 Residential Areas

CO₂ collections in the residential area (sites 7 to 11 on figure 1) showed that, other than Ae.notoscriptus, numbers of man-bi ting species were low~ ( see Table 3).

Traps at two premises collected high numbers of Ae.notoscriptus indicating that at least in the vicinity of these premises the principal man-bi ting species was of a domestic origin. This situation suggest that public education concerning backyard mosquito breeding is required.

2.2 Areas Adjacent to Town

Previous surveys in Katherine have identified the principal sources of mosquitoes near the town as being:

1. rubbish dump area

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...

4

2. remnant pools in river bed 3. sewage effluents at abbatoir.

At these three sites the dominant man-bi ting species has been ex. annulirostris :.. This species also poses a potential health risk because i t is the principal vector of the virus that causes Australian Encephalitis.

CO₂ trap collections during this Cx.annulirostris to be the most

survey also showed common man-biting species.

Numbers of Cx.annulirostris collected at the abbatoirs were relatively low. A larval survey the following day revealed no mos qui to breeding in the abbatoir sewage ponds. The pond margins were weed free and wave action was present. There was no mos qui to · breeding in the area adjacent to the holding yards which receives run-off from washings. A ·possible source of these Cx. annulirostris · was the nearby town sewage treatment works. Currently the sewage input is greater than the system can handle and the Department of Transport and Works is using a large borrow pit area adjacent to the sewage ponds as an evaporation pond. Most of the margins are steep and there is little emergent vegetation which can allow mosquito breeding. However at the western end an area of shallow margin is allowing the growth of weeds. Cx.annulirostris larvae were detected breeding in this area. High numbers of Cx.annulirostris were collected in the CO₂ trap at this site. With time, the extent of this weed growth will increase, thus allowing more breeding of Cx. annuli- rostris. This situation Deeds to be monitored to prevent this site becoming a source of mos qui toes in the town. As an immediate measure Temephos ('ABATE') could be applied to the site to control mosquito breeding. The recommended solution would be to construct a number of small evaporation · ponds within

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the area currently being used. Each pond could then be filled in sequence thus maintaining steep margins that allow wave action.

High numbers of Cx. annulirostris and Ae. notoscriptus were collected in the CO₂ trap placed at the top of the riverbank near the Katherine South Primary School.

Possible sources of Ae.notoscriptus are containers and treeholes. Sources of Cx.annulirostris are most likely to be the remnant pools left in the river bed as the level falls. Dispersal of Cx. annulirostris from the breeding site at the town sewage ponds, along the river, could also contribute to this catch. Drainage of the larger pools in the river bed combined with the filling of smaller pools would remove these mos qui to breeding areas.

Sources of the high numbers of fx.annulirostris collected at the dump site are probably the shallow flooded areas in the vicinity of the dump. These flooded areas are also the source of An.annulipes and An. meraukensis. The flood water species Ae. normanen- sis, Ae ~ lineatopennis and Ae. alboscutellatus are most likely breeding in shallow pools which occur following rain, in the vicinity of the dump and to the east of the dump .

Significant numbers of Ae .notoscriptus were also collected at the dump site. The container breeding survey at the dump located breeding of this species in vehicle tyres. At the time of the survey there were about 200-300 tyres at the dump. Such a collection of potential container breeding sites could contribute to numbers of nuisance mosquitoes in the area and present an ideal site for the rapid increase in numbers of Ae. aegypti, if this species were imported from Queensland. These tyres and other i terns capable of holding water such as car bodies,· tins etc should be either buried or crushed so that they cannot hold water.

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CONCLUSIONS

1. f1e. aegypti appears to be absent from Katherine.

2. A publicity carnpa1.gn concerru.ng mosgui Lo b.recd i.ng ¹¹¹ containers is needed to reduce numbers of donH.:-!3 t.ic nuisance mosquitoes .

3. The abbatoirs are not curr,-:nt ly an impor tant ~.;out-ce of mosquitoes.

4. Breeding of ex. annul.iros tri::; :Ls occurring :u1 the t emporary evaporation ponds at the - town sewage treatment plant. This

~jite is now an important source of thi s species.

5. The municipal dump area ^1~3 an important source of mos qui toes, with breeding in bo t.h shaJ. low ':_flooded areas and containers (principally tyres). All containers should be disposed of properly and the dump are;:-1 needs to be drained.

6. Remnant pools in the Katherine riverbed may be a source of Cx. annulirostris for the town. ^A Compreher1c: i ve larval survey of these pools 1s necessary to determine which pools support significant levels of mosquito breeding. These :;ites could then be rectified by draining them into the river.

K. Hodder W. Kelton

Officers Conducting Survey

G. Davis

Supe~vising Officer

P. Whelan

Officer in Charge

TABLE 1

AEDES AEGYPTI SURVEY - KATHERINE FEBRUARY 1982

·LOCATION OF SOURCE - SUMMARY Incomplete information available for dump, data not included.

Street No.Premises Date No.Premises No.Containers No.Containers No. Containers Positive

Name Examined Examined where with Water with Larvae ^VJ ::::J

mosquitoes ^.µ _ru ^U)

found ^U) ::::J ^·rl u ^·rl H

breeding ^{.. .µ U) .µ}

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H ::::J ^Q) H ><

u ^{r l} ::::J ·rl f'\J

U) ::::J 01 r l ~

0 8 h ::::J ·rl

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0 H :::1 h f'\J

h ^.j..l 01 f'\J ...c:

Q) Q) >< >< ><

i::t: i::t: u u u

INDUSTRIAL AREA

Victoria Highway

l

¹¹

--- --- ^17/2/82

9 109 ---·---39 --- ----27

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·- - ----²⁵¹ ---- --------·----

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RESIDENTIAL AREA

Bernard Street _{13 17/2/82} 3 13 5 3 4

Rundel Street _{5 17 /2/82 3 11 7 6 2 1}

Campbell Street 8 18/2/82 ⁴ 16 ⁹ 5 6

Shaw Street lJ_ 13/2/82 6 33 9 7 4

Heron Street _{4 13/2/82 2 13 6 5} 2 2

Cox Crescent 33 18/2/82 6 48 10 3 6 ' 1

Dakota Street _{13 18/2/82 5 11 5 5 2}

TOTALS ,

for Each Species

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1 1

1 1

(RESIDENTIAL AREA) 87 29 145 51 34. 26 1 3 1 1

---

--- -~ --- ---~--- - - - - ---- ---- ---

--- -,- --- ______________ T ______________ ,_ --- ---

TOTALs - (RESIDEN- ·

I ·

TIAL & INDUSTRIAL) 98 39 I 254 90 61 1 51 l 5 1 2 1

---~---~---~=---~---=~==

- ~ ====~===~====~====-====~==--=-===c=====

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TABLE 2

AEDES AEGYPTI SURVEY KATHERINE FEBRUARY .1982 NATURE OF SOURCE

Incomplete information available for dump, data not included.

Type of. No. Times No. Times NUMBER CONTAINERS POSITIVE

Container Container Larvae

With water Recorded Present Ae. ex.

notoscriptus quinquefasciatus ..

Vehicle tyres ^SJ_ · 32 19 17

Plastic and ice-cream

containers 24 9 7 7

.

Buckets 30 9 5 ·4

Plant pots 6 2 2 l

Kitchenware bowls 9 2 l 1

Tins (paint, food etc) 8

Drums 4, 12, 20, 44 gall 24 9 8 4

Garbage bins 8 3 1 2

Ornamental pools 9 4 3 3

Bird/animal drinking bowls 6 2 2

Boats/canoes 3

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1.

FOR LARVAL SPECIES Other

Species

3 ex. pullus ( 1) * ex. halifaxii ( 3) Ae. tremulus . ( 1)

1 ex. J:~alifaxii l ex. halifaxii

.

.

1 ex. pullus

2 ex. annulirostris (1) An. annulipes ^{( 1)}

* Species incidence

TABLE 2

Type of No Tjmes

Container Container

With water Recorded

;

i

Wheelbarrows ! ₃

Watering cans 3

Baths/bowls etc 6

Car parts 12

Car bodies 16

Plumbing fittings 4

Truck body 3

Freezer/Refrigera~or cabinet

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Machinery parts

!

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Mower catcher

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Baby stroller hood 1

Other plastic ware

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2

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AEDES AEGYPTI SURVEY - KATHERINE FEBRUARY 1982 NATURE Of SOURCE

No Times

I

NUMBER CONTATNERS POSITIVE FOR LARVAL SPECIES Larvae

Present

Ae. Cx. Other

notoscriptus guinquefasciatus Species

1 1 1

. .

1 1

2 1 2

-

I 6 Sp. 32

9 ! ^{7 1}

2 2

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1 1 1

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2.

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TABLE 2 3.

AEDES AEGYPTI SURVEY KATHERINE F2BRUl>.RY 1982 NATURE OF SOURCE

Type of TNo,Tilnes No. Times NUMBER CONTAINS RS POSITIVE FOR Ll'~RVAL SPECIES

Container Container Larvae

With water

I

1

Recorded Present Ae. ex. Other

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notoscriptus quinquefasciatus Species

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J

Esky 5

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Railway sleeper .l

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Cement mixers 4 ! l l

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Water tank

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Washing machines 3 l 1

Toolboxes 2 '

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Metal drip trays

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TOTALS 254 90 6J_ Sl

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Ae. tremulus 1

I ex. annulirostris l

I

I

ex. halifaxii 5

l

ex. sp 32 l

ex. pullus 2

I

^An. 2.nnulipes l

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l;J) TABLE 3

Date Site 17.2.82 1

'

17.2.82

I

²

17.2.82 3

17.2.82 4

17.2.82 5

18.2.82 6

KATHERINE - FEBRUARY 1982 CO₂ BAITED TRAP - COLLECTIONS

Number of female mos·qui toes caught in one trap in one night S P E C I E S

U)

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ru ·rl Ul

Ul r l C: Ul ::i

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::i ·rl 0 X u ^{QJ ..µ} C u

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·rl C r l C H ..0 C: C: H ..µ QJ

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QJ Q)

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Beside Effluent Drain

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Adjacent to Sewage Ponds 6 2 2 J.

(town ponds)

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Beside Holding Yards at

Northmeat Abbatoirs ^{3 2 4} 2

Beside Drainage Pools

Adjacent to Rubbish Dump 3 10 2 6 8 1 .10 27 28 2

On Top of River Bank Near

South Katherine School 6 ₃ 2 9 94

Beside Boat Ramp Under High Level Road Bridge

> - - - -

In tree near front gate

of Riverview Caravan Park, _{1 1 1}

Victoria Highway

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E ^·rl :::J ru r l C H ^{(Y) 4-<}

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2 30 1 .

2 l 68 4

l 84 3 l

3 1

1 2 1

TABLE 3

Date Site 18.2.82 ' 7 18.2.82

I

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18.2.82 ^I i 9 18.2.82 10

19.2.82 6 19.2.82 11

19.2.82 12

KATHERINE - FEBRUARY 1982 CO₂ BAITED TRAP - COLLECTIONS

Number of female moiquitoes caught in one trap in one night

S P E C I E S

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I

164 Dowling Street 1 6

251 Stutterd Street 36

919 Dove Street ³

Clarke Crescent,site marked

I

on figure 1

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1

Riverview Caravan Park Second house from southern

end of Second Street 38

On river bank adjacent

to Katherine Hospital 1 1

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:NEL YR INUNDATION

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