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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.
Helminthic Disease of Cattle
HUGH McL. GORDON, B.V.Sc., McMaster Animal Health Laboratory, C.S.I.R.O., Sydney
GENERAL COMMENTS
1. Cattle suffer a great deal more damage from worm infestation than is generally realised.
2. The rapid increase in the cattle population of Australia is likely to continue for some years as sown pastures and irrigated pastures are developed.
3. More cattle are being run on sheep properties as sown pastures become well established.
4. Losses due to worm infestation in cattle are not usually as obvious as in sheep but are reflected in general unthriftiness and failure to gain weight and fatten rapidly.
5. With increasing numbers of cattle, especially on sheep properties, it is essential to have a rapid turn-off of young beef; not only because this is the most economical form of beef production, but it is also essential to have a clearance of the previous drop of calves to make way for the next drop. Thus, young stock must grow and fatten rapidly without any check. Malnutrition is the most important cause of slow growth; worm infestation is probably the next most important cause.
6. Cattle and sheep share certain species. Fasciola hepatica is probably the most important parasite common to both ruminants, and cattle may play a very important part in the epidemiology of fasciolosis of sheep. Paramphistomes also occur in sheep. Haemonchus placei of cattle develops well in sheep and produces haemonchosis identical with that due to H. contortus. On the other hand, H. contortus does not develop well in cattle. Trichostrongylus axei is common to both and is capable of causing serious infestations. Cooperia spp. sometimes infest sheep. It is probable that Nematodirus spp. are also common parasites.
7. Handling cattle for drenching is a great deal more troublesome than drenching sheep.
8. Cattle may be infested with a great variety of helminths. The more important ones in Australia are:
Fasciola hepatica—Liver Fluke.
Paramphistomes (three species)—Stomach Fluke.
Haemonchus placei—Barber's Pole Worm.
Ostertagia ostertagi—Small Brown Stomach Worm.
Trichostrongylus axei—Small Stomaeh Worm.
Trichostrongylus spp.—Several species in the small inestine.
Cooperia spp.—Four or five species.
Nematodirus spp.—Thin-necked Intestinal Worm (three or four species).
Bunostomum phlebotomum—Hookworm.
Dictyocaulus viviparus—Lungworm.
Of somewhat less importance, but still potential causes of economic loss are the following:
Echinococcus granulosus—Hydatid Cyst.
Cysticereus tenuicollis—Bladder Worm Cyst.
C. bovis—Beef Measle.
Moniezia benedini—Tapeworm.
Neoascaris vitulorum—Large Round Worm.
Onchocerca gibsoni—Beef Nodule Worm.
Other helminths which have been recorded in cattle in Australia and the importance of which has yet to be studied are:
Strongyloides papillosus.
Capillaria spp.
Trichuris spp.—Whipworm.
Onchocerca gutterosa.
The larvae of Stephanurus dentatus, the Kidney Worm of pigs, will infest cattle and damage the liver. Larvae of Ascaris suis, the Large Roundworm of pigs, may also damage the liver of cattle; producing eosinophilic granulomas.
GEOGRAPHICAL OCCURRENCE
The precise distribution of cattle parasites has not been fully determined but there are some general indications of regional preferences.
F. hepatica has the same distribution in cattle as in cheep and in addition is found commonly in many coastal areas where there are few sheep. It is present in the Mary River Valley north of Brisbane and then extends south throughout the higher rainfall regions of N.S.W. There have been considerable extensions on the western slopes and even on the plains during the sequence of wet years. The irrigation areas of the Riverina and northern Victoria were early invaded by Simlimnaea subaquatalis, the intermediate host snail, and now Liver Fluke is well established in cattle in much of the region. There have been outbreaks of Black Diseases in cattle in the irrigation areas of Victoria.
The paramphistomes are widespread in swampy country which harbours the planorbid snails which are the intermediate host.
H. placei is chiefly a parasite of summer rainfall regions like H. contortus in sheep. B. phlebotomum also favours summer rainfall regions but has a fairly wide distribution from north Queensland to the south coastal district in N.S.W. It is rare on the tablelands. B. (Oesophagostomum) radiatum has a wide distribution but heaviest infestations occur in summer rainfall regions. 0. ostertagi and T. axei are parasites of the winter rainfall regions. Cooperia spp. show differences within the genus. C. oncophora is found chiefly in winter rainfall regions, C.punctata and C. pectinata in summer rainfall regions. D. viviparus is seen chiefly in coastal and cooler districts having a regular rainfall.
These are only general indications and there is a good deal of overlapping between summer and winter rainfall regions; as seen, for example, in the occurrence of H. placei and O. ostertagi.
EPIDEMIOLOGY
Cattle habitually graze and defaecate in swampy places and thus their habits favour the completion of the life-cycle of most species; especially the trematodes, F. hepatica and the paramphistomes. The larvae of the hookworm and Strongyloides papillosus infest by skin penetration and must have the muddy conditions of the swamp, calf pen and cow yard for their propagation and accession to the host.
The dung pad provides a favourable and protected situation for the development and survival of the eggs and larvae. If the pad dries out quickly many larvae may be trapped in the deeper layers, but may survive there for some months until heavy rain breaks the pad. Larvae are able to migrate away from dung pads provided there has been some rain-not necessarily enough to break up the pad-and have been found two feet away within 24 hours of reaching the infective stage. This appears to be an example of adaptation to ensure that larvae reach a situation where they are likely to be ingested by cattle, which usually do not graze within about twelve inches of dung pads.
The overcrowding of calf pens and yards, and of small paddocks by young dairy stock, is probably the most important factor predisposing to heavy infestations. Thus, the elimination of the permanent pen, yard or pasture and the substitution of rotational use of several enclosures is one of the first steps in the control of helminth parasites of cattle.
The seasonal occurrence of changes in the worm burden of cattle has been studied in Australia by Dr. F. H. S. Roberts and his colleagues at the Veterinary Parasitology Laboratory of C.S.I.R.O. in Queensland for a number of years and a fairly clear pattern has emerged. In the summer rainfall regions (Queensland and northern and north-western N.S.W.), H. placei, B. phlebotomum, C. punctata, B. radiatum and C. pectinata appear to be acquired in summer-autumn, and heaviest infestations were recorded in autumn-winter. In winter rainfall regions (southern N.S.W., Victoria, Tasmania, S.A. and W.A.), O. ostertagi, T. axei and C. oncephora infestations tended to reach peaks in autumn, winter and early spring in calves dropped in late winter to early summer. In some late winter calves T. axei was abundant in late summer.
Cattle appear to develop resistance to helminth parasites more rapidly than sheep and, in contrast to sheep, resistance to Haemonchus is developed quickly and is strong and persistent. It is thus unusual to experience heavy infestations in cattle beyond 18 months old. Liver Fluke is an exception and there is no doubt that dairy cows, anaemic from heavy infestations, suffer depressed milk production..
A good deal of work still is required before a true assessment of the significance of helminth infestations in adult cattle can be made. Very few complete worm counts have been made on adult cattle in Australia, but counts of over 400,000 worms, chiefly T. axei, O. ostertagi and Cooperia spp., have been recorded in investigations in U.S.A. These figures indicate severe pathogenic infestations. Lighter infestations may not give rise to clinical diseases but may be of economic importance and are certainly of epidemiological importance. For example, a cow passing only 10 eggs per gramme of faeces may disseminate over 200,000 eggs per day. Thus, as in sheep husbandry, where treatment of ewes before lambing is one of the most important attacks on the contamination phase of the life-cycle, it well may be that treatment of cows in the beef herd may be essential if calves are to be raised with light worm burdens which will not retard rapid growth and development.
One of the conclusions from the investigations carried out by Dr. Cooperrider in U.S.A. was that adult beef cattle carried heavier infestations than adult dairy cattle, and he remarked that, "It is interesting to note that the time in the life of the animal when the least attention is given to the animal is the time parasites assume the greatest importance, i.e., between calfhood and bred adult in dairy cattle and after reaching maturity in beef animals".
DIAGNOSIS
Clinical symptoms are not specific. Unthriftiness has multiple causes; half-a-dozen different parasites may produce anaemia and the causes of diarrhoea are many. It should be noted that haemonchosis is seen vary rarely in cattle in good condition-perhaps never in fat cattle. This is in marked contrast with the disease in sheep; where it is not uncommon for fat sheep, even adult animals, to succumb from severe anaemia. The species of helminth which may produce certain symptoms may be grouped.
Parasites which may produce anaemia:
H. placei.
F. hepatica.
B. phlebotomum.
Cooperia spp.
Paramphistomes (the immature forms in the duodenum).
Parasites which may produce diarrhoea:
O. ostertagi.
T. axei.
Cooperia spp.
B. radiatum.
Paramphistomes (the immature forms in the duodenum).
Faecal examinations in cattle have been given a sound diagnostic basis by the work of Dr. Roberts and his colleagues. It is essential to make both egg counts and cultures and to assess the results with a number of modifying factors in mind.
1. There may be additive effects between species,e.g. H. placei and B. phlebotomum are blood suckers and a combined moderate infestation with each may give rise to a severe anaemia.
2. When cattle lose their appetite the faecal output is reduced and the egg count will rise.
3. When diarrhoea is present the eggs are diluted and counts will decline.
4. There may be massive infestations with immature worms which have not reached the egg-laying stage.
Thus faecal examinations, as in all helminthoses, have limitations and it is often necessary to make a post-mortem examination. Here again, there are a number of factors which must be kept in mind in carrying out and in assessing the results of the examination.
1. An animal which has died may not be a suitable subject because many worms may have passed out before death and many small species may have disintegrated after death.
2. An animal which has been scouring severely for a few days before death may not be suitable because many worms may have been lost.
3. There are several small species which are not readily seen,e.g., O. ostertagi, T. axei, Trichostrongylus spp. in the small intestine, Cooperia spp. and Strongyloides papillosus. Scrapings must be taken from the mucosa of the abomasum and duodenum and examined with the aid of a microscope. A binocular dissecting microscope is a particularly useful instrument and essential for the detection of small species and immature forms.
4. Symptoms may be due to large numbers of immature worms which cannot be detected microscopically. Here again it is essential to make scrapings for microscopic examination.
5. Ideally, the alimentary canal from abomasum to anus should be sent to a diagnostic laboratory for a total and differential worm count.
PATHOGENESIS
The role of the immature parasite in causing disease has had more emphasis in cattle than in other animals and it is clear that practically all species of gastro-intestinal helminths, including the paramphistomes, are capable of causing fatal infestations before reaching maturity. Some, with migratory stages in the life-cycle,e.g., D. viviparus, N. vitulorum and B. phlebotomum, may cause considerable damage during migration, while those having histotropic stages in the mucosa,e.g., O. ostertagi and B. radiatum, cause a great deal of tissue destruction.
In general, helminthosis in cattle tends to develop more slowly and insidiously than in sheep. This may be related partly to population dynamics; as illustrated by some hypothetical cases. A ewe weighing 90lb, may succumb to haemonchosis if there are 3,000 or more worms in the abomasum. In order to produce a similar degree of anaemia in a cow weighing 1,000 lb., over 30,000 worms may be required. It may be necessary to ingest over ten times this number of larvae to produce such an infestation. Unless climatic conditions are particularly favourable and the contamination rate of the pastures exceptionally high, such numbers of larvae may not be available during a short period of time. Similarly with Cooperia spp., where numbers of the order of 100,000 to 300,000 may be required to produce clinical cases, the dynamics of the population may only rarely provide enough larvae for the rapid establishment of such infestations. However, over a prolonged period of grazing, perhaps many weeks or even months, there may be a gradual accumulation of worms and thus an insidiously increasing burden.
It is dfficult to obtain precise figures for the measurement of the pathogenic effects of parasitic infestations, but in U.S.A. Dr. Boughton has collected a good deal of evidence, which is published in Advances in Veterinary Science, Vol. 2. Another U.S.A. publication shows that in cattle a single dose of cercariae of F. hepatica was followed by a decline in red cells from eight to five million per cmm. in 20 weeks and the count had not returned to pre-infestation levels after 36 weeks. Some interesting figures have been provided by a veterinarian in practice on the South Coast of N.S.W. A dairy herd of 33 cows, heavily infested with F. hepatica, produced 2½ cans of milk daily. Four weeks after treatment with hexachlorethane, and with only 29 cows, daily production was four cans.
It has been something of a mystery why we do not see more cases of severe infestations with D. viviparus, and why the disease known in Great Britain as "Husk" does not appear in Australia in the form which may cause fatalities even in adult cattle. There is still some controversy in Great Britain about the precise ways in which acute outbreaks of "Husk" develop and it seems possible that there may be a virus infection associated with the disease known as "Fog Fever". However, there is no doubt that acute cases of "Husk" often are due to an anaphylactic type of reaction in hypersensitive lung tissue.
The slow recovery of young cattle which have experienced heavy infestations with gastro-intestinal nematodes is characteristic, and it may be many months before the animals begin to grow and put on condition again. The reason for such slow recovery is not known. In sheep, chronic infestations with trichostrongylosis and oesophagostomosis are characterised by loss of appetite, and it is probable that chronically affected cattle do not eat sufficient feed. Often in chronic infestations anthelmintics appear not to have been effective and, in view of recent critical work on the efficiency of a number of drugs in cattle, it is probable that in many instances of chronic infestations recovery was slow simply because the worms had not been removed. Further, many anthelmintics are relatively ineffective against immature worms, which survive and prevent recovery.
TREATMENT
Little was known of the efficiency of the commonly-used anthelmintics for cattle until the advent of phenothiazine, which was so highly effective against certain species that it provided a comparative measure. At the same time, its independence of the oesophageal groove reflex conferred on it a tremendous advantage over nicotine, arsenic and tetrachlorethylene.
However, when critical tests were carried out phenothiazine was found to have a fairly limited anthelmintic range in cattle, being in fact highly efficient only against H. placei and B. radiatum; while having little effect on Cooperia spp. and B. phlebotomum. Like many other anthelmintics for cattle, phenothiazine has not been tested thoroughly under properly-controlled conditions against O. ostertagi and T. axei. The former, because of its histotropic stage in the mucosa, presents additional difficulties in anthelmintics trials-for example, if an animal is treated and the egg count is reduced and then later returns to pre-treatment levels, one cannot be sure of the source of the post-treatment rise in egg count. It may be from worms which were not killed but simply suffered reduced egg production; it may be from worms which have emerged from the mucosa and matured; or, if the cattle are grazing, it may represent a completely new infestation. It appears that for a truly reliable test it will be necessary to kill treated and control cattle and make worm counts; including counts of immature worms recovered from the mucosa of the abomasum by a digestion technique.
The oesophageal groove reflex behaves differently in sheep and cattle. In the sheep, soluble copper salts stimulate the reflex in a high proportion of animals; whereas in cattle copper compounds are ineffective. Wester, in Holland in 1930, showed that sodium salts were effective in cattle and Dr. Roberts and his colleagues have confirmed that a solution of sodium bicarbonate is very effective. It is now generally recommended that when it is desired to stimulate the oesophageal groove in cattle they should be dosed with 60 ml. of a 10% solution a few seconds before the administration of drugs which are not effective unless swallowed into the abomasum.
The outstanding need has been for an anthelmintic effective against B. phlebotomum and Cooperia spp. in the summer rainfall regions, and against O. ostertagi and C. oncophora in the winter rainfall areas.
It is curious that tetrachlorethylene, which has long been recommended in South Africa for treatment against the hookworms of sheep (B. trigonocephalum and Gaigeria pachyscelis), was not effective against hookworm in cattle when tested in Queensland. Nicotine, usually mixed with copper sulphate, has been recommended for cattle for many years. It is clear now that there is no advantage in using copper sulphate, and that if nicotine is to be used it should be preceded by a dose of sodium bicarbonate. However, nicotine causes toxic effects more often in cattle than in sheep and in view of recentlydeveloped anthelmintics there is no justification for its use.
Hexachlorethane appears to be the drug of choice against F. hepatica for it is evidently much less toxic than carbon tetrachloride, especially for milking cows. It may taint the milk for a few days and so it is wise not to treat more than about one-third of the milking herd at one time,
It is independent of the oesophageal groove and is effective against H. placei and the paramphistomes, as well as F. hepatica.
The search for better anthelmintics for cattle by Dr. Roberts and his colleagues showed that toluene (methyl benzene) is effective against hookworms and also against H. placei and Cooperia spp.; and probably against O. ostertagi and T. axei. It is not effective against B. radiatum. It is effective only when swallowed into the abomasum and thus must be preceded by a dose of sodium bicarbonate. Further, it is effective against worms other than H. placei only when formulated as an emulsion or a suspension. Further again, it is necessary to starve cattle overnight before treatment,
Following the demonstration of the interesting anthelmintic properties of 1:8 dihydroxyanthraquinone in sheep, investigations in cattle showed that it is very effective against H. placei, B. radiatum and Cooperia spp., and possibly O. ostertagi. The dose rate of 2 to 2.5 g per 100 lb, bodyweight was non-toxic and the compound was effective whether swallowed into rumen or abomasum.
The latest development in anthelmintics for cattle is the organic phosphorous insecticide known as Bayer L13/59. In U.S.A., Levine found it was highly toxic for eggs and larvae of horse strongyles in faecal cultures, and there were reports that some anthelmintic promise was shown when similar compounds were drenched to cattle. In Queensland, Riek has found L13/59 highly effective against H. placei, Cooperia spp., B. radiatum and B. phlebotomum. In the doses used, there have not been toxic effects and the anthelmintic effects of the drug are independent of the oesophageal reflex. It appears to mark an important step forward in the control of many of the more important nematode parasites of cattle.
The ascarid of cattle. N. vitulorum, has been recorded in most States in Australia but only on few occasions have there been heavy infestations. The piperazines are very effective against this and most other ascarids. There have not been any advances in treatment of lungworm infestation. Certain claims have been made for a proprietary preparation administered by mouth, but trials at the Veterinary Laboratory of the Ministry of Agriculture in England showed that it was not effective.
Small repeated doses of phenothiazine given in salt lick or feed supplement have proved useful in control of cattle parasites in U.S.A. Doses of 1 to 2 g. daily are required to prevent development of eggs and larvae in faeces. A daily intake of this order will check the development of the eggs of species such as Cooperia spp., which are not affected by ordinary anthelmintic doses. This method has not been tested extensively in Australia, but in W.A. some dairy farmers provided calves with 1 g. daily in milk or supplementary feed and appeared to obtain beneficial results. The efficiency of this method of using phenothiazine depends on the regularity and adequacy of the intake. Both may vary tremendously and thus it would be unwise to rely on this method except in cases where it was certain that the animals were, in fact, taking their daily doses. Some recent work in U.S.A. by Dr. Drudge has shown that strains of nematode parasites develop resistance to phenothiazine when it has been administered in small doses over long periods.
CONTROL
General control measures are readily set down but may not be so readily applied; either because, being set down in general terms, often rather vague, the owner does not do anything specially directed towards control of parasitic diseases, or again, being in general terms, the special needs imposed by changing epidemiological conditions are not recognised and the special measures required may not be applied in good time.
Control must be based on a knowledge of epidemiology, which in turn has its foundations on the life-cycle. When the life-cycle is set out to show its several stages and phases, and control measures are set against each, then an overall plan should work out almost automatically.
Some of the more important aspects which must be kept in mind are:
1. Young stock are highly susceptible.
2. Malnutrition predisposes to both heavy infestation and more severe effects from the infestation once established. Cattle usually do not graze as close to the ground as sheep and thus may restrict their intake of larvae. If pastures are inadequate and cattle are forced to graze closely, they then may acquire large numbers of larvae. However, it is not generally recognised that young cattle may be very selective in their search for an adequate diet, and may, in fact, bite very close to the ground.
The symptoms of malnutrition and helminthosis are similar in many ways and the conditions are often additive.
3. The dung pad provides moisture and shelter for the early stages of developing eggs and larvae, but if the surface dries quickly the larvae may be trapped.
4. In spite of the protection afforded by the dung pad it appears that a heavy rainfall is required before heavy infestations can develop. Dr. Roberts and his colleagues have shown that in Queensland a monthly rainfall of about five inches is necessary before outbreaks of haemonchosis occur.
5. The general seasonal trends in infestation have been established by the epidemiological studies carried out by Dr. Roberts and his colleagues, and these trends can be used to base the times for strategic treatments. However, there is still much to be learnt about the seasonal effects in the winter rainfall regions. The epidemiological effects of higher rates of stocking as sown pastures become highly productive must also be studied.
SEASONAL DRENCHING AND EPIDEMIOLOGY
Summer Rainfall Regions
The general seasonal trends are increasing worm burdens in autumn and winter, as a result of infestations acquired during the wet summer and early autumn months. Thus, it seems wise to reduce worm burdens in young stock by treatment in early summer, supported by further treatment towards the end of summer and probably again in the autumn months before the nutritional stresses of winter appear. Where B, radiatum is present, a late winter treatment may be required to destroy adult worms which have emerged from nodules.
Winter Rainfall Regions
The general seasonal trend is for increasing worm burdens in autumn, winter and early spring as a result of infestations acquired from late summer onwards. Treatment in spring should reduce contamination of pastures and, if followed up at the end autumn (April-May), worm burdens should remain at low levels.
In W.A., heavy infestations with 0. ostertagi and Cooperia spp. were seen in August-September in calves born in the autumn. Treatment in July should have prevented the development of heavy infestations.
AVOID OVERCROWDING
1. Eliminate the permanent yard, pen or paddock and replace with a system of rotational grazing and spelling. Moveable calf pens have been used successfully. The New Zealand system of rotational grazing with the calves ahead of the cows appears to have given very effective control of parasitic diseases.
2. On beef cattle properties avoid local overcrowding by subdivision of paddocks, provision of better watering facilities, rotational grazing and spelling. A spelled paddock should be provided for the weaners, which should not be placed in the same weaning paddock year after year.
ADEQUATE NUTRITION
Young growing stock need ample, highly nutritious and palatable feed; whether it is supplied as pasture or supplement, Calves do not thrive on poor quality roughage. A good deal of hay made from pastures is not adequate for young stock. Lucerne hay and protein-rich supplements are better.
SUMMARY
1. Cattle suffer more from helminthosis than is generally recognised.
2. Cattle numbers are increasing and the parasite population also is increasing.
3. Diagnosis is difficult and ideally should be made on a basis of post-mortem examination with complete and differential worm counts. A macroscopic examination in the field may not reveal a fatal infestation with small or immature worms.
4. Some new anthelmintics offer better chances for control.
5. Many of the gaps in knowledge of the problems of cattle parasites can be filled by submission of material to diagnostic laboratories.