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Northern Territory Department of Health Library Services Historical Collection
91(€
NT DEPARTMENT OF HEAL TH~ AND COMMUNITY SERVICES
HISTORICAL COLLECTION
INVESTIGATION OF A MOSQUITO COMPLAINT AT FIVE MILE, DALY RIVER
29 - 30 APRIL 1992
DL HIST 614.4323
LOG ~~;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;~~~~~~~~~~~~~~~~
1992
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INVESTIGATION OF A MOSQUITO COMPLAINT AT FIVE MILE, DALY RIVER 29 - 30 APRIL 1992
D Logan and P Donaldson Medical Entomology Branch
Department of Health & Community Services
1
1.0 BACKGROUND
On 23 April 1992 the Medical Entomology Branch received a complaint about large numbers of mosquitoes at Five Mi le, Daly River. '11he complainant, Fr Allen Kinnane, requested advice on prevention measures that might be taken. On April 28 the Medical Entomology Branch was notified by Fr Kinnane that mosquitoes were no longer a large problem following burning off in the area. Nevertheless two officers from the branch travelled to Daly River on 29 April to investigate the complaint and advise on appropriate measures to reduce mosquito problems in the future.
2.0 METHODS
Collection of adult mosquitoes was made by EVS type
co
2 anda subsample identified at Daly River. The complete trap collection was scanned to check that the subsample was representative. All complete trap collections were compared and an estimate of mosquito numbers made. Subsamples of adults were rechecked later in Darwin.
A survey of potential mosquito larval habitats was made.
Sampling of these habitats was undertaken by soup ladle.
Mosquito larvae found were placed into sample bottles in 70%
alcohol and later identified in Darwin. Discussions were held with Fr Kinnane regarding trap results and probable sources of mosquitoes. A number of prevention measures were advised.
3.0 RESULTS OF SURVEY
3.1 Adult Collection
A C02-bai ted trap set in bush adjacent to roadscrapes off the main road ( trap site 2 ref er figs 1 and 2, Table 1) captured the largest number of mosquitoes. Most of the catch consisted of two species, Culex annulirostris and Coguilletidia xanthogaster, which made up on average 32.6%
and 25.7% of trap catches respectively. Trap catches contained on average of 20% anopheline mosquitoes with the major species being Anopheles bancroftii. Another species present in significant numbers was Aedes normanensis, which made up on average 7% of trap catches. The trap placed at the margin of Red Lily Lagoon (trap site l, fig 1) captured a large number of Mansonia uniformis c-70% of trap catch).
Apart from one other trap site (site 7) numbers of Ma uniformis captured were low (0-14/trap).
3.2 Larval Collection
Five potential breeding sites were visited and water checked for mosquito larvae by repeated dipping with a ladle. Table 2 gives descriptions of collection sites and mosquito
2
species found. Anopheline larvae were found at all freshwater sites checked. The polluted water of the sewage effluent drain provided habitat for Cx annulirostris and Uranotaenia albescens larvae. Larvae of ex annulirostris were also found in pools in the flowline (ref erred to as
'mosquito valley') near trap site 7 (fig 1).
4.0 DISCUSSION
4.1 Likely Mosquito Pest Species for Five Mile
The
co
2 -trap captures of Ma uniformis at sites 1 (Red Lily Lagoon) and 7 ('Mosquito Valley') probably indicate that breeding sites for this species were in close proxjmity to the traps. This is because Ma uniformis generally harbours in vegetation near the edges of its breeding sites which are permanent and semi-permanent freshwater bodies with emergent vegetation. This species may not have been a major problem for residents at Five Mile. Trap collections at sites on the creekline running past Five Mile did not capture large numbers of Ma uniformis (refer trap sites 9 and 4 Table 1).These that were present may have dispersed from other breeding sites in the area.
The two major species trapped, ex annulirostris and ~
xanthogaster, tend to disperse over a much wider area than Ma uniformis. Breeding sites for ~ xanthaqoster are similar to those for Ma uniformis - permanent and semi- permanent freshwater bodies with emergent vegetation. This species was trapped in large numbers in woodland next to the burnt-off area surrounding Five Mile ( trap sites 2 and 5, refer fig 2) . Burning-off is likely to have significantly altered its distribution pattern. It is likely to have been a major biting pest at the time of the complaint.
The other major species trapped, ex annulirostris, breeds in a large number of freshwater habitats. Significant numbers of this species probably come from Red Lily Lagoon and other permanent/semi-permanent freshwater bodies in the area.
Large numbers of this species probably also come from the relatively temporary ground pools in 'mosquito valley'.
Breeding in the sewage effluent drain is likely to be a minor source for Five Mile when compared to other waterbodies in the area. The drain is likely to bP a major source of mosquitoes for Daly River mission becaus 1 of its proxirni ty. Significant numbers of Cx annulirostr··_e_ were trapped at sites next to the burnt-off area (refer 'able 1 and fig 2, trap sites 2,5,10). Large numbers (>1: /trap) were also caught in traps set along the creekline . jacent to Five Mile. At the time of the complaint this species is likely to have been a major biting pest for Fi~e Mile residents.
OU(o'- ' '
3
Anopheline mosquitoes in the vicinity of Five Mile are likely to have dispersed from breeding sites at the margin of Red Lily Lagoon, from pools in 'Mosquito Valley', and from pools in the creekline next to Five Mile. Burning-off has probably influenced distribution patterns in the area, contributing to large catches of anophelines at sites 2 and 10 (Table 1; fig 1). Anophelines, especially An bancroftii, were probably a significant pest problem at the time of the complaint. Another species that is likely to have contributed to the pest problem, Ae normanensis, was trapped in largest numbers in woodland northwest {trap site 5) and south {trap sites 2 and 8) of Five Mile. This species may have its major breeding sites in the temporary pools in
'Mosquito Valley'.
4.2 Prevention Measures
Discussions were held with Fr Kinnane regarding what possible local measures could be implemented to reduce mosquito problems. It was suggested that burning-off significantly reduced numbers of mosquitoes at the Five Mile camp itself. The trap set at Five Mile captured small numbers of mosquitoes { trap site 3, Table 1) . This trap site had the lowest collection of mosquitoes of all ten trap sites.
After an inspection of camp houses was made in the company of Fr Kinnane, a number of control and prevention measures were discussed.
1. Lighting. It was suggested that:-
{a) Lights on buildings should be replaced by yellow or red light;
(b) A line of three or four fluorescent tubes could be placed along the south and eastern edge of the camp to act as a barrier. These lights should have a reflector on one side and be baffled to increase the amount of reflected light at the expense of direct light. Light should be reflected away from the camp and toward the surrounding open woodland;
(c) A light source could station standing some 100m light source would attract camp.
2. Screening.
be mounted on the east of Five Mile.
mosquitoes away from pump This the
It was suggested that camp houses should be screened.
The construction of the houses and the incidence of screen destruction however make this option less attractive than just using mosquito nets at night.
4
3. Reducing harbouring sites.
Maintaining cleared areas and cutting grass at the edges of the camp can deter mosquitoes from harbouring nearby.
4. Wearing repellants.
According to Fr Kinnane aborigines were not likely to wear repellants because it was culturally idiosyncratic to rub such materials onto the skin.
5. Long-sleeved clothing.
Such clothing such as overalls and long-sleeved shirts will generally protect wearers from mosquito bites.
6. Adult and Larval control by spraying.
Spraying to control mosquito larvae and adults is not likely to be practical because of the large area of breeding sites available to mosquitoes in the Daly River area.
TABif: l mTAL NUMBERS OF AWLT FEMALE IDS(}TI'IOES ffilllCTrn IN EVS DRY ICE BAITED TRAPS DALY RIVER APRIL 30 1992. SEE MAP 1 FDR ADULT TRAP SITES .
TRAP IJX'.ATIOO ~ SPEX:IES TOTALS
SITE An annulipes Ae e]choensis Ae reesi Cx bitaeniorhynchus Cq xant.hCXJaster
00. An bancroftii Ae lineatopennis Ae vigilax Cx squarrosus Ma lllli fonnis
An rreraukensis Ae nonnanensis Cx annulirostris Cx vicinus Ur nivipes
---·-· - -- - - ---w - - -
1 North side of red 7 49 150 2 2 68 566 1 845
Lily Lagoon.
') Adjacent. to road scrapes 82 128 38 1 59 377 3 357 1045
LJ
1. 8km SE of 5 rnile.
3 five rrdle. 3 1 2 15 21 2 44
4 ] 00 M East of 5 rnile 32 54 2] 13 2 111 47 ]4 294
Adjacent to creek.
5 Roadside 700M North 4 36 3 1 76 214 283 617
of turnoff to Wooliana.
6 Turnoff to Woob ana 8 10 5 1 25 78 94 3 224
RHS of Road.
'] J.5km NE of Daly River 13 54 11 3 1 57 1 66 40 246
Mission approximately 2km SW of 5 Mile.
8 1km SW of 5 Mile 30 38 30 56 142 40 2 338
9 150M North of 5 Mile 15 52 36 36 99 34 272
ne..xt to Creek 1 ine.
10 Creek line adjacent ]7 88 31 1 30 201 129 8 505
adjacent to main Rd.
700M SE of 5 Mile.
'lUfAl.S 211 509 176 2 2 300 2 1 1444 5 2 1 1139 635 ] 4430 6
~
J 6 ~-
l,
TABLE 2 lARVAL SURVEY RESULTS FOR DALY RIVER APRIL 30 1992.
Refer to fig 1 for larval sample sites • . MAP (fig 1) ffililCTIOO SITE
SITE ID.
IJ.
L2
IA
L5
Sewage IX)l1d effluent outflow.
thickly vegetated margin;
shaded,slow--rroving water.
Pcllds in flowline crossing sewage JX)l1ds road.
partly-shaded,still water with grass at edges.
Adjacent to road,'rrosquito valley' tffOIX)rary JXX)ls with grass,
sunlit or partly shaded.
Margin of Red Lily lagoon.
still water with aquatic vegetation-suhnerged and arergent;S\Illlit or partly shaded.
Waterholes in creekline 100n east of Five Mile.
still water with algae and
~rged aquatic vegetation;
partly shaded.
SPECTF.S
ex
annulirostris Ur albescensAn bancroftii
An bancroftii
ex
annulirostrisAnopheles spp.
An bancroftii An rooraukensis
ex
hilliex
vicinus/starkeaeIJ
>--.r--
-
0 1.5 1.5 2 #l
LI
Scab
Fig 1. Location of adult trap sites and larval sampling sites for the mosquito complaint investigation at Daly River 29-30 April 1992.
KEV
building
5Paso11allv vl't Hl'~
cr,ek s,aI,d roatf 9ri,,l roid/track
co,_ tu, sit, lar,al coll. sitP
KEY
0 building
seasonally wet ~re
;:...,-. creek
-
s,al,d road9rav,l ro~d/track
#l ca, tnp sit,
Fig 2. Representation of numbers of adult mosquitoes trapped at sites around Daly River 29-30 April 1992. Each mm of the diameter of the circles represents 25 mosquitoes trapped. Data is taken from the totals column in Table 1. The inner circle at trap site 1 represents the total n_umber of mosquitoes trapped less the number of Mansonia uniform1s trapped at this site.