LIVER FLUKE
Fluke, an ever present issue for an increasing number of dairy farms, is currently the subject of a wealth of research at Liverpool University, as vet Alison Howell explains
iver fl uke affects about 80% of UK dairy herds and can infect grazing animals of all ages. The number of animals in affected herds can vary from a small number of heavily infected animals to 100% of the animals being infected.
L
In most herds just a small number of animals are heavily infected, with most animals having few or no fl uke.
This variation is due to the individual differences in general health, immune system,
genetics and other unknown reasons. What is liver fl uke?
Fluke is a type of parasitic worm, mainly affecting cattle and sheep. Animals are infected by eating grass containing parasitic cysts (metacercariae). The fl uke then migrate to the liver where they mature and produce eggs, which are passed out onto pasture. Fluke can survive in the liver for 1-2 years, and cause damage by migration and feeding on blood.
What makes liver fl uke different from
other parasitic worms? Liver fl uke cannot be spread directly from animal to animal or via the soil. Fluke require an intermediate host, the mud snail, as part of their lifecycle. This means that in the absence of the mud snail, fl uke cannot be transmitted between animals. It is a small snail that only lives in muddy, damp or boggy ground. You are unlikely to see these snails as they are tiny and burrow into mud, however, you may be able to identify likely habitats from the characteristics of your fi elds. Typical sites include muddy banks of ponds or streams, and damp or boggy areas. Certain plants can also indicate likely snail habitats. Because of the snail intermediate host, fl uke is a localised problem. One herd may have a high level of fl uke while a neighbouring farm with better drained fi elds may have none.
Plants often associated with mud snail habitats include sharp fl owered rush, soft rush and fl oating sweetgrass.
What effect does liver fl uke have? In most cases of fl uke you won’t see obvious disease, the most likely result of a fl uke infection is a drop in milk yield of about 8%. Fluke infected animals also have impaired immune systems, making animals more susceptible to other diseases including Black disease, Salmonella and TB, and may affect the TB skin test. It may also make vaccines less effective.
Obvious disease is rare in adult cows. When it does occur, due to a very heavy fl uke burden, you may see weight loss, anaemia, bottle jaw and rarely, death
38 THE JOURNAL JUNE 2015
How can you manage fl uke? The fi rst thing to remember is to try and avoid introducing fl uke when it isn’t already present in your herd. This means quarantining and treating all bought-in animals with an effective fl ukicide on arrival.
When you suspect your herd is infected then diagnosis is crucial. The fi rst step here will be a bulk milk test to determine the general level of fl uke in the herd. A positive result means that at least 25% of the animals in the herd are infected. When a test returns a high result most animals are probably infected. You can also undertake individual blood, milk or stool tests if you are concerned about particular animals.
Year to year variation Fluke can be more of a problem in some years than others, depending on the weather. Wetter summers and milder winters can make fl uke much worse. The effect will depend on the nature of the grazing land. For example, when you have a boggy fi eld which is the source of most of the fl uke problem and it dries out one year due to an unusually dry summer, you may fi nd that the following year there is much less fl uke than normal. When you have land that tends to stay wet even in dry years the weather will not make as much difference. Cold winters have the effect of killing off parasites and delaying snail development so that fl uke development on pasture is delayed. There is an online regional parasite forecast on the National Animal Disease Information Service (NADIS) website at www. NADIS.
org.uk
Develop a fl uke control plan Rather than just treating cattle for fl uke when you believe you have a problem, the best approach is to get together with your vet and consider your farm as a whole to develop an effective plan. See the Control of Worms Sustainably (COWS) website
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112