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Northern Territory Department of Health Library Services Historical Collection
DEPARTMENT Of HEALTH 1110 COIIIIUNITT SERVICES
V
C)0 6(2,
HISTORICAL COLLECTION
MEDICAL ENTOMOLOGY INVESTIGATIONS OF ROWLANDS DAIRY
KATHERINE
20 -22 FEBRUARY 1989
Appended April 1989
FOR FURTHER INFORMATION:
DL HIST 614.432 WHE 1989
CO'JTACT: MEDICAL ENTOMOLOGY BRANcH
DEPARTMENT OF HEAL TH AND COMMUNITY SERVICES GPO BOX 1701
DARWIN NT 0801
:LEPHONE: 20 8333 Peter Whelan
Senior Medical Entomologist
..
CENTRAL LIIRAFIY
- 6 MAR 1998
TERRITORY HEAL TH SERVICES
MEDICAL ENTOMOLOGY INVESTIGATIONS OF ROWLANDS DAIRY
KATHERINE 20 - 22 FEBRUARY 1989
Peter Whelan
Senior Medical Entomologist
DEPARTMENT OF HEALTH AND COMMUNITY SERVICES
WHE:
1~~9
46307
1. 0 INTRODUCTION
There have been eleven laboratory confirmed cases of epidemic polyarthitis in Katherine since the start of December 1988. This indicates a relatively serious degree of mosquito disease transmission and has· followed this Department's efforts in the latter part of 1988 to prevent such an outbreak. A full investigation of the mosquito breeding situation and the potential for disease transmission was carried out on September 13-14, 1988, and the resultant report presented to the relevant authorities.
Following the confirmation of the present disease outbreak in Katherine,
carried out
a comprehensive adult mosquito collection was over the period 6-8 February to assess the current mosquito situation, and to collect adult mosquitoes for virus investigations. This survey revealed significant mosqu~to levels in various localities. The current was to confirm the sources of these investigation
mosquitoes and authorities.
to discuss the situation with relevant
2. 0 PREVIOUS REPORT AND PROGRESS TO DATE
The previous report "Mosquito Investigations 13-14 September, 1988" located the sources of high numbers of various species of mosquitoes, the vector of epidemic polyarthritis disease.
Katherine, extremely including The major source of vector mosquitoes was Rowlands Dairy, caused directly by the lack of any effective effluent treatment or waste water management program. Immediate and ongoing mosquito control and mosquito monitoring measures were recommended and the need for an emergency solution outlined.
Some immediate control of the breeding sites was carried out by Rowlands Dairy for a few weeks after the matter was highlighted, · but the control was not continued. There has
been no plans submitted on an effluent treatment facility and there has been no progress on a suitable waste water management program.
3. 0 EPIDEMIC POLYARTHRITIS DISEASE IN KATHERINE
There have been eleven cases of epidemic polyarthritis disease in Katherine from the start of December 1988 to date. Most of the cases appear to have been contracted in mid and late December. At least eight of the cases are from residents in Katherine
along the Katherine River.
township or in the -rural area
The seasonal prevalence of epidemic polyarthritis in the Northern Territory is illustrated in Table 1. Most of the Katherine cases have been contracted in December, but there are s t i l l significant numbers of cases in January and February. From Table 1 i t is obvious that the Katherine region has a particular problem on a per capita basis when compared with other regions. A total of sixty-six confirmed cases have occurred in the Katherine region from 1 980-89, compared with eighty cases in the Darwin region, whi includes both Darwin and Jabiru.
There have been thirteen confirmed cases in all of 1988 from the Katherine region, with fifteen cases in the previous year. This represents a significant increase in the number of cases from previous years (See Table 2).
Unfortunately, the Department of Health and Community Services mosquito monitoring program was not carried out between 22/11/88 and 24/1/89, and so levels and species of mosquitoes present are not available for the transmission period. However, previous and subsequent mosquito monitoring indicated high populations of _g_ulex
3
annulirostris, the common banded mosquito. This is a recognised vector of Ross River virus, the causative agent of epidemic polyarthritis.
This species was previously found breeding in enormous numbers at Rowland's Dairy in effluent run-off, and effluent contaminated post-irrigation water. The previous September investigations indicated that Rowland's Dairy was the major source of vector mosquitoes, due to the very large area and extreme productivity of the breeding sites.
There were a number of other breeding sites found, with the waste water dam at the Abattoir being the most important.
During the dry season there are very few p~oductive breeding sites for this species except for artificial sources such as the Dairy.
Cul ex annulirostris can fly at least ten kilometres in one night under favourable environmental conditions.
Dispersal up and down the Katherine River would have been particularly favoured because of the sheltered moist environment. This species must live at least seven to ten days to be able to transmit the virus. There can be no doubt that the mosquitoes originating from Rowland's Dairy would disperse as far as Katherine town and further up the Katherine River.
With such enormous numbers originating from the Dairy, and the dispersal power of this species, the high number of mosquitoes in the Katherine area could be directly attributable to the Dairy's waste water practices. Those mosquitoes that dispersed furthest from the Dairy would probably be the oldest mosquitoes, and thus have a greater potential to transmit disease. It is not unreasonable to suggest that cases of epidemic polyarthritis in Katherine town and rural areas near the river can be at least partly attributable to the mosquitoes originating from Rowland's Dairy.
4. 0 RECENT ADULT MOSQUITO MONITORING
The mosquito collections carried out on 7-8th February revealed very high numbers of vector mosquitoes in the Rowlands Dairy area. A brief summary table appears below:
Location Culex annulirostris/C02 trap
Rowlands Dairy - entrance Lily Ponds - (opposite Dairy) Sewerage Ponds <PAHA)
Abattoir
Lockheed Street, Katherine Cnr Jaensch & Gorge Roads
2023 872 185 122 2 21
The mosquito collections carried out 20-22 February recon(irmed that Rowland's Dairy is s t i l l the major source of vector mosquitoes. A brief summary table for this period is included below:
Location Rowlands Dairy Abattoir
Culex annulirostris/C02 trap 264
Lockheed Street, C away from river)
Shady Lane, C near river, upstream of town)
1 5 2 2
From these two periods of collection there is no doubt that Rowland's Dairy is s t i l l the major source of vector mosquitoes. Although there has been a reduction in numbers from early to late in February, the current levels of mosquitoes at the Dairy are similar to those found in September 1988 before any mosquito control was carried out.
These levels s t i l l represent a significant public health risk, particularly as mosquito numbers can alter drastically from week to week and even greater numbers could occur at any time.
5
The levels of mosquitoes recorded for 7-9 February may be resulting in more epidemic polyarthritis cases that are s t i l l awaiting det.ection by the Department's reporting scheme. This is quite probable in the light of the information in Table 1 which indicates that significant transmission has taken place in February in past years.
Public complaints or a perception of mosquito numbers by people living near the Dairy are not a reliable guide to periods of potential mosquito borne disease. Species likely to enter houses or bite in the presence of light or at various times of the day or night may not be the same as the vector species. In addition, mosquito populati-ons can fluctuate so widely in a short space of time that huge hatches of mosquitoes can occur with l i t t l e warning. These mosquitoes may be sufficient to set off a new wave of disease transmission, despite immediate larval control as soon as the problem becomes evident from complaints.
5. 0 MOSQUITO LARVAL SURVEY
A mosquito larval survey was carried out Rowland's Dairy on 21-22 February.
in the vicinity of Raw effluent was flowing via a pipe into an unformalized depression that has the appearance of a primary effluent pond. The run-off from this area was continuous, and flowed in an uncontrolled way through an overgrown grassy drainage line for approximately three hundred metres, where the effluent then entered a formal creek line which drains to the Katherine River. Prolific mosquito breeding was occurring down the entire length of the effluent. The species present was
polyarthritis
Culex vector.
Culex annulirostris general Katherine area.
annulirostris, the epidemic This is a primary source of numbers in the Dairy area and the
Checks of other areas indicated that, at the time of the survey, othe~ pools and swamp areas on the Dairy property
OO(o(p5
were not significant sources of mosquitoes, but had the capacity to become so at other times. There was a considerable area of non-draining land on the western side of the main entrance to the dairy, that is associated with a former drainage line. It is probable that various roadworks, ground levelling operations and irrigation structures have altered the former drainage patterns of this land. This area is the recipient of post-irrigation water and i f there is significant amounts of cattle dung dispersed on the land, this area has the potential to become a significant and additional source of vector mosquitoes.
6. 0 FLY INVESTIGATIONS AND RECOMMENDED CONTROL MEASURES
There was a significant house fly (Musca domestica problem in the vicinity of the dairy, and in the general area between Florina Road and the dairy. The flies were originating primarily from dead carcases and poorly dispersed cattle dung.
There were numerous cattle carcases dumped in and near the effluent pipe discharge area. These carcases were in shallow water and were host to masses of maggots. The carcases were not covered with earth. It is strongly recommended that a separate purpose designated disposal pit be constructed on well drained land away from any drainage lines, and any carcases be dumped and immediately covered with earth such that fly breeding is prevented.
This practice Regulation 16
of disposing of dead and Regulation 18 of
animals contravenes the Public Health (General Sanitation) Regulations of the Public Health Act.
A notice could be served on the owner to request a change to this present disposal practice.
7
The remainder and the majority of the fly breeding was occurring in cattle dung. There was a considerable area of cattle dung spread over an area of at least a hectare, between the cattle holding yards and the effluent stream.
There was waste water from the cattle holding pens discharging into this dung disposal area. In some places the dung was at least 500 mm thick, and almost bogged our four wheel drive vehicle. The dung appeared to have been disposed of at least a few months previous, and probably has been a practice for a considerable time. Wherever the dung was examined, high numbers of fly maggots were present. The area of dung and the moist condition of the dung is ensuring that the area is a major an~ enormous source of houseflies. This is a direct contravention of Regulation 10 Parts 1 and 2 and Regulation 9 of the Public Health (General Sanitation) Regulations of the Public Health Act. In addition, any rainfall run-off through the dung disposal area or from the paddocks where the dung is presently being dispersed, is likely to lead to run-off water with high organic levels being discharged to the Katherine River.
It is recommended that the present fly breeding areas be covered with soil to a suitable depth to prevent fly breeding and that all waste water discharged from the dair~
area be collected and suitably disposed. The present dung dispersal practice of dispersing the semi-liquid dung on freshly prepared land should be examined to ensure that fly breeding in not occurring. If i t is, the dung will need to be incorporated into the soil immediately after dispersal, or dispersed thinly enough so that fly breeding does not result. The suitability of dung disposal practices should be monitored regularly by the Regional Health officers of the Department.
7. 0 RECOMMENDED MOSQUITO CONTROL MEASURES
The most immediate mosquito control need is to kill the larvae in the present breeding sites. Because of the risk of killing other non-target insects that may be achieving some biological control, only Bacillus thuringiensis var.
israelensis CB. t. i - brand names such as Teknar) should be used. The B. t. i. needs to be applied over the entire water surface, from the effluent release point near the Dairy, all the way to where the effluent enters the creek.
The application should be by motorized equipment (either back-pack vehicle assisted or by helicopter). Application of B. t. i. must be started immediately, be conduct-ed weekly without a break, and must be checked 2-3 hours after application for success. It is strongly recommended that local health officials monitor and assess the control weekly by examining the breeding sites at a number of points to ensure that the control is effective.
In the longer term, a suitable effluent and waste water facility must be installed. The plans of such a facility must be drawn up as soon as possible and implemented in the coming dry season. The local Department officials should examine the plans and seek co-ordination and comment to ensure that the plans are suitable. The implementation . of the plans should be followed through by Regional officials. If there is no committment to prepare plans and to implement such plans, the Department must contemplate the closing of the Dairy to stop the effluent release and reduce the public health risk to the residents of Katherine and to the tourist industry.
9. 0 CONCLUSIONS
Rowland's Dairy is causing actual and potential public health problems by breeding flies and mosquitoes. This is in direct contravention of a number of specific regulations
•
•
under the implemented mosquitoes.
treatment
9
Public Health Act.
immediately to
Control control
measures must both flies
be and Plans for effluent and waste water storage, and dispersal must be formalized as soon as possible for comment by the relevant authorities. If plans for effluent treatment and dispersal and dung dispersal are not prepared in time to be implemented before the end of this dry season, the Department must contemplate closing the Dairy to reduce the public health risks .
•
11
TABLE 1
EPIDEMIC POLYARTHRITIS CASES IN THE NORTHERN TERRITORY 1980-89 SEASONAL PREVALENCE OF INFECTION
MEDICAL ENTOMOLOGY BRANCH
N. T. DEPARTMENT OF HEALTH AND COMMUNITY SERVICES
Seasonal prevalence of epidemic polyarthritis infection in the Northern Territory. The time of infection has been calculated as
14 days before date of 1st blood sample, 10 days before 1st symptoms or recollection of exposure to high numbers of mosquitoes. This data has been collected from contributing laboratories and Doctors from 1980-89 Lines indicate probable vectors. Broken lines are used where
identity of vector is particularly uncertain.
REGION DARRIN
Cx.ann Ae. vig EAST ARNHEH
KATHERINE
BARKLY
ex. ann Ae. vig
ex. ann Ae. nor
Ae. nor ALICE SPRINGS
Cx.ann
TOTAL
As at 16/2/89
J F H A M J J
8 34 10 6 4
2 2 2 2
11 1 5 5 3
2( 1?)
24 51 16 12 3 6 2
A s
4
5 0
Cx.ann = Culex annulirostris (common banded mosquito) Ae. nor - Aedes normanensis (floodwater mosquito) Ae. vig = Aedes vigilax (salt marsh mosquito)
0 N D TOTAL
2 10
1 3
3 27
3 5 50
80
27
66
3( 1?)
177
TABLE 2.
EPIDEMIC POLYARTHRITIS CASES IN THE NORTHERN TERRITORY 1980-89 MEDICAL ENTOMOLOGY BRANCH
N. T. DEPARTMENT OF HEALTH AND COMMUNITY SERVICES
Probable infection points for serologically confirmed cases of of epidemic polyarthritis cases submitted to the Pathology Laboratories, Darwin, based on first blood sample date.
REGION DARRIN KATHERINE BARKLY
80 7
ALICE SPRINGS 1?
EAST ARNHEM UNKNORN OUTSIDE NT
TOTAL
* As at 16/2/89 4
1 4
81 7
9
82 4 6
4
1 4
83
8 6
4
19
84 8 1 3
25
85 7 2
10
86
9 4
1 3
Note: Regions are as defined by Department of Health and Community Services with Darwin Region including Jabiru.
87 8 1 5
2
25
88 22
1 3
1 0
47
89*
2
3
2
8
•
..DEPAI~T MENT
OFHEALT H AND CO MMUNITY SEI~VI CES
NORTHERN TERRITORY OF AUSTRALIA
Your Ref:
Our Ref:
11th April, 1989
Len Scott
Regional Director KATHERINE REGION
Dear Len
RE: ROWLAND'S DAIRY
The proposals by Rowland's Dairy (refer 88/213, 13 March 1989) for effluent collection and disposal do not cover all of the environmental problems outlined in my previous report. The proposals that Rowland's Dairy have outlined should reduce the total amount of mosquito breeding currently occurring, but it is unlikely to result in a reduction in the numbers of flies and mosquitoes to an acceptable level that will prevent a pest and a public health problem. A total approach to the current problems must be undertaken.
Aspects that must be incorporated into a total approach include:
1. Wet season runoff from manure spreading.
It is likely that the current and anticipated practice of manure spreading will lead to manure con tam in a ted water ponding in a number of non-draining areas, particularly the large area at the entrance to the property. This, and other non-draining areas that will receive contaminated water, must be drained.
2. The mixing of rainwater run-off from covered areas and manure contaminated areas.
There must be a proper drainage proposal to prevent large amounts of manure contaminated water from holding areas and production areas entering drainage lines. In particular, there should be a proposal to separate uncontaminated rain water from manure contaminated run- off.
Telephone: (()X9) 80 2911 Telex: J\ J\i-15011
Facsimile: 41 0:'i(iO
/\II correspondence to: Secretary Department of I kalth .ind Community Services r.un Il,w 171\1 (")i\ T)WTl'J l'JT ll~fll
2
3. The rehabilitation of the present effluent pond area The present discharge of effluent into a manure rich bog in a former creek line must be rehabilitated to prevent fly and mosquito breeding. This will necessitate either excavating or filling the present contaminated area and preventing drainage lines from entering the contaminated area.
4. Reconstruction of the dam
The present darn on the creek on the western side of th~
property does not have a properly constructed overflow structure. This must be rectified so that excess water can flow directly into the creek line below the dam to ensure the free flowing nature of this creek is not . impeded.
5. The rehabilitation of the old manure dump area near the creek
This large are of thick manure deposits has resulted in the death of trees. The whole area of approximately a hectare will need to be excavated and re-spread over a wide area or deep ploughed or covered with soil to a depth of at least 30cm depth.
6. Carcass disposal facility
A designated carcass disposal facility, constructed in a suitable location to the satisfaction of the Health Surveyors, must be installed as soon as possible.
It is suggested that Rowland's Dairy should provide detailed plans for all of the aspects above and that they should be carried out this dry season. 'Failure to carry out these rehabilitation and preventative measures will lead to continued high mosquito and fly numbers and continued transmission of mosquito borne disease in the Katherine area.
Yours sincerely
Peter Whelan
Senior.Medical Entomologist for SECRETARY FOR HEALTH AND COMMUNITY SERVICES
.)
