The external parasites of sheep (195?)

[Music] if sheep are to be kept profitably and provide a good return in wool and meat the parasites that prey on them must be controlled if possible eliminated sheep that are infested with external parasites suffer int irritation to relieve this irritation they spend a considerable amount of time rubbing biting and scratching time that would normally be spent grazing and looking for food this causes damage to the fleece and apart from the reduction in Wool value shearing becomes much more difficult one of the most Troublesome of the external parasites that affect sheep is the Sheep blowfly duilia caprina this fly is the most widespread of the primary sheep blowflies and is responsible for practically all fly strike in Australia it is a coppery green blowfly slightly larger than a house fly it is most active in areas where rainfall is associated with warmth and humidity there are other flies associated with fly striking sheep and these are known as secondary flies these flies attack sheep already struck by the primary fly several species of both primary and secondary flies are found in Australia [Music] [Music] struck sheep usually do not graze they may bite or scratch the struck area which looks dark and [Music] moist close examination will reveal maggots in the fleece on the skin the female fly lays her eggs on moist areas the eggs soon hatch into [Music] maggots the maggots break the surface of the skin with their sharp mouth hooks at the same time releasing a substance which digests the skin causing large superficial wounds [Music] the damage which these maggots do to the skin can be judged by their vicious tearing action [Music] if left untreated the Sheep may die lesser damage results in enlarged areas of bare skin or Tender wool which may lead to complete shedding of the fleece after 3 to 6 days the maggots fall off to wander on the ground the exact period depending on climatic conditions they finally select some suitable spot either some distance down in clean soil or among the roots of grass in which to pupate in about 8 Days the adult fly emerges when conditions are [Music] [Music] suitable by pumping blood into a fine sack on its head the emerging fly pushes the top off the pupil case and if need be bues its way to the surface having emerged the fly runs on the ground whilst its wings expand after about half an hour it can take to the air after a meal and a mating it seeks out a sheep to start the cycle again the complete life cycle may be as short as 18 days in warm moist weather in Colder Weather the life cycle may take several months [Music] the body loss demolin ois lice of the most widespread of the external parasites affecting sheep in Australia they prefer the cool high rainfall regions although they can Thrive and cause appreciable damage in hotter drier areas three types of Li occur on sheep the body L is the most common cause of trouble body lifs are mostly found in the neck fos along the sides of the sheep spreading onto the back they feed on skin Dey and will die if removed from the Sheep more than a few days although they move readily from sheep to sheep and so a very small number of infested animals can cause the spread of body lice through an entire flock the body lus is a wingless insect about 125th of an inch long with a reddish brown head cream body with dark bands across the abdomen in the adult [Music] the females produce about one egg per day so the rate of multiplication is rapid the female lus attaches her egg to the wool fiber after about 10 days the cap on the end is forced off and a young Lous emerges and then under go a number of mols and reaches maturity in about 3 weeks Lous eggs are not destroyed by dipping therefore young lice may be found hatching out for periods of 10 days or so after dipping the residual action of the insecticide however copes with these irritation of lice causes sheep to rub and scratch vigorously the Sheep then lose condition because of the constant irritation even more important wool production is adversely affected the Shaggy appearance of the sheep and the wool caught on fence posts and trees where the sheep have been rubbing is generally the first indication of lice infestation the Sheep Ked melophagus of Venus the incidence of Keds has decreased appreciably in recent years they're restricted mainly to the cool high rainfall areas of the Eastern table lands and the southern part of the continent the Sheep K often wrongly called the Sheep tick is not a tick but a wingless blood sucking fly with six legs a tick has eight it is a brownish Gray colored insect about 1/4 of an inch long the abdomen is particularly noticeable when engorged with blood kids cause an obvious stain to the Wool by the excretor and the debris they leave behind as they feed by sucking blood badly infested sheep are usually poor in [Music] condition kids show some preference for the lower side of the body especially under the neck infested sheep are continually biting and scratching about every week the female K lays a small wh- skinned lava which is firmly attached to a wool fiber approximately 10 LA are produced during the kid's life in a matter of a few hours the skin of the lava becomes dark brown as it passes into the pupil stage these pupe are more tolerant to treatment than adults as the insecticide does not penetrate the protective cover and they don't hatch out for at least 3 weeks the adult K lives for several months passing its entire life cycle on the sheep but can't survive for more than a week off the [Music] Sheep the itch mite sores ois the itm was first discovered in Australia in 1940 however they are thought to have been in existence on this continent for many [Music] years they have now been reported in most parts of Australia but are less common in the drier pastal areas there was a significant increase in numbers following the change from arsenical dips to those containing chlorinated hydrocarbons compared to investigations into the control of KS or lice that into the control of the itch mite is exacting and tedious the parasite is not visible to the naked eye and its presence on the sheep can be determined only by taking skin scrapings it is sometimes necessary to take several scrapings from an infested sheep before the presence of bites can be determined to take a skin scraping clip a 2in square area as close to the skin as possible on the upper sides of the ribs or flanks moisten this area with liquid paraffin or peanut oil and scrape the fuzz towards the center of the clipped area with a scalpel sharp pocket knife or razor blade transfer the scrapings to a glass slide for examination under a microscope absence of mites in anyone scraping does not necessarily mean that the Sheep are free from mites they are not always easy to find especially during the summer when their numbers decrease the itch mite is a minute parasite which lives on the skin of sheep and like all mites passes through several stages of development the whole life cycle can be completed in about 5 weeks it lives in or on the top layers of the skin and spends its whole life on the sheep it feeds by sucking the fluid from the skin cells this action and movement on the skin causes the Sheep to rub and bite the eggs hatch into L followed by three nymph stages shedding their skin each time until they grow into adults the immature stages spend some time just below the superficial layers of the skin the spread of infestation occurs mainly During the period of Shing and shortly after however spread can also take place at mating and lamming if sheep show signs of wool damage be sure that grass seeds or lice are not causing the trouble before bothering to look for each might it bite infested sheep usually show a cheed ragged appearance of the wool on the sides a bad infestation can cause a white scarf next to the skin which may have hard ridges on it the skin may be Leen in color the wool is often cotton and it may carry an unusually high condition which gives a marked yellow appearance modern methods of controlling the external parasites of sheep consist of applying insecticide to the host sheep sheep can be either dipped Shard tip sprayed or jetted the method to be used however will depend upon the pest which is be eradicated or controlled the time of the year when the treatment is to be applied and the degree of control required dipping or Shing are the only effective methods of ensuring the complete wetting of the wool down to the skin over the whole body area plunge dipping is still the most widespread method of controlling the external parasites of sheep the efficiency of this technique depends on using the correct strength of insecticide and thorough weap of the [Music] sheep sh dips have some advantages over plunge dips but the Sheep must be held in the spray is long enough for the wool to be saturated and the insecticide must be kept up to [Music] strength all dips can be used for show or plunge treatments tip sprays however require selected insecticides having the power of diffusion down the wall a tip spray does not saturate the fleece but applies a low volume of high concentration insecticide to the surface of the fleece tip spraying is ideally suited for the treatment of sheep for the control of Len kads immediately off shears it therefore offers most advantage to those grazers who wish to avoid remastering sheep for treatment after sharing [Music] jetting is used mainly for blly control but for efficient results susceptible areas must be wetted right down to the skin it is a waste of time and money to use a weak wash or to apply too little fluid if fly strike is not an annual problem on a property then jetting should be saved until necessary after a spell of warm muggy wet weather there is a chance of Fly Trouble occurring [Music] if sheep with long wool have Li the parasites can often be held in check by jetting a broad strip of insecticide down the back in this way wool staining from Dirty dip wash is avoided this treatment may have to be repeated to effectively keep the life population down until shearing after shearing dipping must be carried out in the normal manner to ensure eradication [Music] [Music] external parasites cost the industry many millions of pounds each year by studying their living habits improved insecticides and techniques will be developed to eradicate and control them it must be remembered however that if all the Sheep are not treated or dipped properly then any method will fail even the best treatments cannot be relied upon to protect sheep against reinfestation for more than a few months read the directions for use carefully before dipping and remember with all mechanical treatments they are only as good as the man who uses them h