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This article was published in 1957
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Fluke and Black Disease
With Special Reference to Occurrence in the Murrumbidgee Irrigation Area.
H. MAITLAND WARE, B.V.Sc. Veterinary Inspector, Narrandera.
FLUKE DISEASE is an acute or chronic disease of sheep and cattle caused by infestation with the common liver-fluke, Fasciola hepatica. The liver-fluke is a flatworm found in the bile ducts of the livers of sheep, cattle and rabbits. Following damage to livers by the invading flukes, in many cases there is a secondary invasion by bacteria causing deaths from Black Disease. The intermediate host in the life-cycle of the liver-fluke is an aquatic snail, in Australia, Simlimnaea subaquatilis. which has a particularly wide distribution.
For many years Fluke dseases has been recognised in many parts of Australia. Its distribution is practically universal, but in this country is confined largely to the higher rainfall areas of the Coast and Tablelands of New South Wales and Victoria, the wet south-eastern corner of South Australia; and in Tasmania to the northern, midlands and east coast districts. It is said to be practically unknown in Western Australia. From the Tablelands of New South Wales there is some extension on to the lower rainfall areas of the western slopes; as far west as Wellington on the central western slopes and Cootamundra on the southern slopes. In certain instances it has been observed on the dry western plains after exceptionally wet years. Fluke snails now are spread widely in the irrigation areas of the Murrumbidgee and Murray rivers. This distribution has been outlined by Ross and Gordon (1).
In South Australia, in addition to the area mentioned above, Fluke Disease has become a problem on the gently sloping shores of Lakes Alexandrina and Albert at the mouth of the Murray River. This was described recently by Banks (2). The sheep graze on vegetation exposed as winds cause day-by-day fluctuations in water levels. Formerly the water in these lakes was too saline to support the snail intermediate host, but has become fresh following the erection of barrages which protect irrigation works further up the river. The host snail now thrives in this environment. It has been stated that sheep can only graze on the frontage with safety from about April to November each year.
In most of the areas described, Fluke Disease occurs in the usual habitat of springs, bogs, streams and irrigation areas. In the Murrumbidgee Irrigation Area of New South Wales, situated within the Narrandera Pastures Protection District, the country presents special features which, as far as can be ascertained, have not been described previously.
The Area generally comprises a very flat plain situated in a low rainfall part of New South Wales. The average rainfall for the district lies between 13 and 16 inches and prior to the introduction of irrigation, was more often than not very dry. A feature of the plain is a series of shallow watercourses, timbered with Box. These so-called Box Swamps provide natural drainage, and vary in size from a few hundred square yards up to 30-40 acres in extent. Under normal rainfall conditions in earlier years these swamps were dry for the greater part of the hotter months of the year, but since irrigation they have been used for drainage purposes. Fluke snails have been found in the main irrigation channels west of Griffith, but Fluke Disease, so far, has not occurred in every year. There seems to be no adequate reason why the disease does not occur more often, but it may be due to the fact that the snail population is not great in the main irrigation canals. Water channels in this area appear to act in the same way as tanks and dams in other parts. Snails are not found plentifully in tanks and dams for the most part, but frequent more often the slow-running streams and bogs. Very little vegetation grows in the main channels and ditches and channels are dry for the greater part of the winter. Sheep therefore do not have access to infection.
Over the years some very heavy mortalities have occurred in sheep in the M.L.A. due to Fluke and Black Disease. Almost invariably these outbreaks occur after a long dry summer; mortalities commencing about January. The usual history is several wet seasons, then a long dry summer, then a Fluke mortality. Stock are forced into the swamps owing to lack of feed and water elsewhere. 1956 and the summer of 1956-57 produced the typical set of circumstances. 1956 was a record rainfall year and most of the swamps filled; but from November onwards very little rain was recorded. Several heavy mortalities promptly became evident.
The following cases are reported, very briefly, to illustrate the point made above that Fluke mortalities in this area only occur in odd years and under special circumstances. In January, 1953, a heavy mortality occurred in Merino ewes on a property near Darlington Point. The sheep had been grazed on a swamp during December, 1952, and January, 1953. About the time the water dried up the sheep commenced to die. On investigation it was found that the mortality was due to acute Fluke infestation and Black Disease. Approximately 250 ewes died before the mortality was controlled by drenching with Carbon tetrachloride and vaccination against Black Disease.
No further cases of Fluke or Black Disease were reported in this area following the above until February, 1957. As stated, 1956 was a record rainfall year, but very little rain fell after the end of October. Just under two inches only were recorded from early November until the end of February, 1957. All the swamps had filled during the wet weather, and in many cases they had been kept wet by the running of drainage water into them. Conditions were ideal for the aquatic snails; while owing to the dry summer stock frequented these swampy areas.
At the end of February, 1957, a property near Gogeldrie, a few miles south-west of Leeton, reported a serious mortality in sheep. On investigation it was found that deaths had commenced early in December, 1956. The sheep, a mixed flock of approximately 280, were dipped about 4th December and some three days later deaths commenced to occur. The owner blamed the dipping and did nothing about it. However, mortality continued until some 70 were dead by the end of February. Mortality was due to Acute Fluke infestation and some Black Disease. In all, about 90 sheep died before the outbreak was controlled. The sheep had been grazed continuously for a good long period on a swamp; kept moist and green by run-off water from the nearby rice fields. In the ditches carrying this drainage water, aquatic snails were very numerous.
Within recent months further mortalities have been investigated on irrigation properties in the neighbourhood of Leeton, Whitton and Gogeldrie. In each case mortalities have been heavy and found to be due to acute and chronic Fluke infestation. All the affected sheep had been grazing in Box swamps or had access to drainage channels where the water was almost stagnant. One property claimed to have lost over 200 and another over 100; with several up to 40 sheep deaths.
In addition to these mortalities in sheep, there have been a few deaths in cattle in the area. These have been due in each case to chronic Fluke. Generally speaking, however, there has been little trouble in large stock. The fact that cattle harbour the Fluke should be remembered, though, when control measures are being adopted.
Liver condemnations for Fluke at slaughtering establishments in the area have not been high. They usually are intermittent, and only in certain lines of sheep. The symptoms of both acute and chronic Fluke are well known and are not being dealt with in this paper, but a sound knowledge of the symptoms and of the life cycle of the Fluke is essential when working out control measures.
As far as control measures are concerned, very little has been done in the Murrumbidgee Irrigation Area to date. The Box swamps would appear to be the main problem in dealing with snails. Some of the smaller ones could be fenced to deny access of stock, but some of the larger areas would present some difficulty. Bluestone could be broadcast over most of these areas at appropriate times of the year.
A useful article on Liver Fluke of Sheep appeared in the Rural Research in C.S.I.R.O., No. 17. September, 1956 (3); the following points being quoted: For the destruction of the snails it is suggested that all swamps which cannot be drained satisfactorily be treated with Bluestone in September October and again in February March. Bluestone can be broadcast, either alone or with sand, at the rate of 25 lb. per acre. All snails should be destroyed before the spring to prevent a new season's cycle from infection of snails by miracidia which have emerged from eggs laid since the previous autumn. Recent experimental work suggests that Copper pentachlorphenate may have certain merit for eradicating the snails. This can be dusted on at the rate of 10 to 25 lb. per acre, or sprayed at 800-2000 gallons per acre of a concentrate (10 lb. per 100 gallons water). Spraying apparently gives better results than dusting. The amount of fluid per acre depends on the amount of cover in the swamp; the denser the cover the more fluid required.
Points to be borne in mind when working out any control measures are as follows:
(a) Characteristics of the Fluke; aiding occurrence and persistence:
1. High rate of egg production.
2. Long-lived (up to 11 years).
3. Wide range of hosts (sheep, cattle, pigs, horses, rabbits, man).
4. High rate of multiplication in the snail.
5. Longevity of encysted cercariae.
6. Rapid multiplication of snails under favourable conditions.
(b) Hazards for the Fluke.
1. Eggs must have very wet conditions.
2. Miracidiae must find snail within 24 hours.
3. Encysted cercariae must be eaten by sheep.
4. Very susceptible to certain drugs,e.g., Carbon tetrachloride and Hexachlorethane.
Briefly summarised, this is an account of several mortalities due to Fluke Disease in the Murrumbidgee Irrigation Area, with special reference to features peculiar to that area and suggested methods of dealing with the parasite in the particular environment.
Thanks are due to Officers of the Department of Agriculture, N.S.W. for permission to use material contained in Departmental files.
References:
(1) Internal Parasites of Sheep-Ross and Gordon.
(2) A.V.A. Annual Conference, 1957-A. W. Banks, B.V.Sc.-Epidemiolgy of Helminth Infestation in Sheep: South Australian aspects.
(3) Rural Research in C.S.I.R.O., No. 17, September, 1956-Liver Fluke of Sheep.