SHEEP-DISEASE AT TAURANGA.

Auckland Star, Volume XXII, Issue 142, 17 June 1891, Page 3

SHEEP-DISEASE AT TAURANGA.

BY PROFESSOR A. P. W. THOMAS,' M.A., F.L.S., UNIVERSITY COLLEGE, AUCKLAND.

(From the "New Zealand Farmer;")

For some time past T have been in correspondence with Mr P. C. Crump, of Oliauiti j with reference to the disease of sheep in the Tauranga district. Mr Crump and Dr. Forbes had found in the nasal passages of diseased sheep a number ot minute parasites, and sent some of them to mo for identification. I found some of them to be th'a larvce or maggots of Oestrus (or Ccphalomyia) ovis, the common bot fly or the sheep, a parasite known to occur in many parts of the colony. At Mr Crump's request I consented to examine some of the diseased sheep if they should be sent up to Auckland. Two lambs and a wether were received on the 19th May. As the matter is one of general interest to farmers, I have thought it desirable to publish the following account of the results of my examination. This must, however, be considered as only an incomplete account, as I have as yet dissected but two out of the three sheep sent by Mr Crump, and even with regard to these there is still some material reserved for microscopic examination, which the time at my disposal has not permitted me to examine thoroughly. Perhaps I may be permitted to state that the thorough and detailed examination of such cases demands much time and care, and even the sacrifice of all leisure available after fulfilling my duties has not sufficed to complete my work. I will state first the results of the examination dealing with each sheep separately.

No. 1, Lamb: This lamb had never left the Tanranga district previous to its journey to Auckland. It was very thin and weak, the unhealthy wool scarcely concealing the prominent hones. It stood with hack arched and hollow flanks, a thin watery discharge running from eyes and nose. When driven it would fall down from excessive weakness, bub was able to get up again. The post mortem examination showed that the lungs contained a moderate number of lung-worms [Strongylus filaria). The substance of the lungs showed signs of long-standing disease. The surface was uneven in places. Much of the tissue at the ends of the smaller lobes was devoid of air, boing solid, and nearly of the colour of liver. This injury to the lung was probiibly due entirely to inflammation set up by the irritation caused by the lungworms. The small intestine contained three different kinds of parasitic worms namely : —(1) Tape-worms in large quantities. (2)' Strongylus filicollis, a small, slender thread-worm, present in large numbers— not fewer than several hundreds. (3) Strongylus contorius, a few. The wall of the intestine was marked by numerous irregular reddened patches due to the attacks of the parasites. The large intestine contained numerous separate joints and series of joints of the tape-worm, also a moderate number of another kind of thread-worm (Trichoccphalus affinis). The nasal passages were somewhat inflamed, and contained very numerous white larvse of Oestrus (Cephalcmiyia) ovis, less than onefourth of an inch in length. I estimated the number of these parasites to be at least one hundred. Much time was spent in examining the other organs, but they appeared to be free from any serious disease, though it should be mentioned that the organs generally did not present quite the appearance which would be seen in a lamb in vigorous health. But such slightly unhealthly appearance of the organs is only what is to be expected in an animal in such a weakly condition. No. 2, Wether: The wether was very thin, and in an extremely exhausted condition when it arrived. The journey was probably too great a tax on its powers. It lay on its side, refusing all food and drink, and died on the fourth day after its arrival. This animal was _ one of a large flock brought from Napier twelve months ago. Mr Crump states that 150 did not do well. The wethers had been sent to Katikati during the present autumn, but had not done well, and many had been lost. The lungs were strongly congested, and were of a deep crimson or purple colour. In places the air-cavities were completely filled with a red inflammatory exudation. The smaller air holes were filled with a reddish froth, but the inflammation did not seem to have extended to the trachea. Lung-worms were present. I did not, however, see more

than lialf-a-clozen, though there is no doubt that; the lung more. The small intestine contained thread-worms, as in the lamb. The large intestine contained a considerable number of Strongyli different from any of the worms mentioned above. The liver was diseased. It was of an opaque yellowish brown colour. On the surface it seemed firm, but on pressing between the ringers ib yielded readily. Oα cutting open the substance it was found that the proper liver substance (the liver cells) had undergone a process of softening or liquitaction. The spleen and mesenteric glands were of somewhat abnormal character, but as the microscopic investigation has not been completed, I reserve further remarks on these organs. The nasal passages were intensely congested, and contained the larvre of the sheep bot-lly, as in the lamb. They were, perhaps, equally numerous. The immediate cause of death in this wether was inflammation of the lungs. It is possible that the irritation due to the lung-worms may have been, in the first instance, the exciting cause of the inflammation, biit it appears probable that the disease was strongly aggravated by the driving and exposure to which the animal Avas necessarily subjected on its way to Auckland. Indeed, in a sheep of such enfeebled powers the exposure on the journey might in itself give rise to an attack of congestion of the lungs. The cause of the enfeebled condition of this sheep is, however, a more important point for our consideration. Lung-worms, two kinds of intestinal worms, and very numerous larvae of the sheep bot-fly are quite sufficient to account for some degree of disease, but in the present case the diseased condition of the liver is a point to which considerable importance must be attached.

In the case of the lamb, we have a formidable list of parasites present, including lung-worms, abundant tapeworms, three kinds of nematodes (threadworms, etc.) in the intestines, and the larvte of the bot fly in the nasal passages —these parasites, occurring for the most part in large numbers, are, in my opinion, quite sufficient to account for the enfeebled condition of the lamb.

It will be seen that the result of the present examination agrees with the observations made by me on diseased sheep at Tauranga some yeais ago. We have heard a good deal of late of ' the Tauranga sheep disease.' It would be more correct to use tho phrase, ' Sheep diseases at Tauranga. 5 Some years ago 1 found ten different internal parasites in various sheep at Tauranga. Of these ten parasites seven occurred in the sheep recently examined. Each of these parasites is really the cause of a distinct disease, and we have in addition a disease of ; and it is not by any means clear that this exhausts the list of the diseases which have done more or less harm at Tauranga, for it must be remembered that I have only examined fourteen animals from chat district.

The serious nature of the ravages of the lung-worm are well known, and it is probabJy the worst of the parasites we have now to deal with. But the intestinal parasites can also be the cause of serious disease and death. We have, however, this advantage in dealing with intestinal parasites, that it is not difficult to dislodge them.

It must be remembered that the extent of the mischief done by parasites is largely dependent upon their numbers. If only a few be present no noticeable injury may be caused if the sheep be well nourished and kept under generally favourable conditions. But if the number of parasites be large, the irritation caused by their presence has a very injurious effect (perhaps chiefly by its inliuence on the nervous system), and when we have large numbers of parasites in different parts of the body, all exercising their own peculiar powers for evil, we need not be surprised that the victim should cease to thrive, and fail into a sickly condition. Once in a weakly condition, the sheep feela the irritation due to the parasite still more, and becomes weaker and weaker.

The bot larva? in the nasal passages appear to be present in unusually large numbers. I found the same larva; in sheep at Tauranga six years ago. They are by no means confined to Tauranga, but are widety prevalent in the colony, but as a rule they occur in small numbers only. I have never found more than five fully-grown larvae in one sheep. It is extremely improbable that all, or even a majority of the hundred young larvae found by me in a single lamb, could have developed to the adult condition. Many seem to be dislodged by the sheep in their efforts to relieve the irritation in the nasal passages by violently expelling the air through the nostrils. There are few data for estimating the exact amount of harm which would be caused by large numbers of bot-larvse, as different writers express very different opinions. Some of these opinions, however, are evidently of little value. On the whole, it appears to be generally recognised by more recent writers that the larvae may give rise to serious injury, and even be the cause of death. The running from eyes and nose, which is supposed to be symptomatic of the so-called lauranga disease, may be in part due to the irritation caused by these larvae.*

It will be asked why removal to Katikatior other districts should be so beneficial to the diseased sheep from Tauranga ? To this it may be replied that change of air is generally beneficial in cases of weakness. It is stated in England with reference to the disease produced by the sheep bot that animals suffering from it are much relieved by change to another district, but I would point out that the wether and one lamb (still alive) received from Mr Crump are but sorry testimonials to the restorative qualities of Katikati air. Mr Crump states that thelambswere benefited by the change, but that the wethers were not.

The past season has been, on account of its excessive moisture, exceptionally favourable for the development of parasites. We must remember that the moist, equable climate of New Zealand, free for the most part from extremes of drought and cold, is eminently adapted to encourage the development of parasitic life.

*NOTE.-The sheep bot-fly must not be confused with the bot flies of the horse and ox. All these, however, are closely related, belonging to the Oestridte, a family of two-winged flies. (Diptera). The sheep bot-fly is said to be the most injurious of the three. In England the perfoet-winged fly is active in June and July and during those months lays its eggs (or perhaps the already hatched larvse) within the nostrils of the sheep. The larvae pass the autumn and winter and part of the spring months within the nasal passages, living on the mucus and epithelium. When ready to transform they fall out of the nostrils, and, hiding themselves in the ground, they undergo the transformation into the perfect fly.