Review/Oorsig Volume 22, Issue 02 - Page 17

the freshwater which liver 2 snails The shell of the freshwater snail in which stomach fluke multiply. cycle 600 1 on 1 The shell of the freshwater snail in which liver fluke multiply. er Life cycle of flukes in the environment LIFE CYCLE snails OF FLUKES IN THE - TRANSMISSION Freshwater are active during late ENVIRONMENT spring, summer and early autumn. Stomach fluke pa th o a sh d b se nsi Liver fluke Volume 22 • Issue 02 • 2018 This is the stage that is infective for livestock and in this form, the flukes can survive for a few months. LIVER FLUKE - DETAILED UNDERSTANDING OF THE DISEASE PROCESS THAT TAKES PLACE IN THE ANIMAL Safer period to graze wetlands. 4 1. Start of infection The signs of disease will depend on the number of infective worms (high, medium or low) taken in by the animal. The signs that will be seen with a medium to high infection are described here. Danger period to graze wetlands on infected farms. 2. Week 1-8 Animals show rapid weight loss, weakness, signs of blood loss and even sudden death if the infection rate is extremely high. 3. >12 Weeks Affected sheep can fall behind when herded or develop bottle jaw which is a sign of slow blood loss. Continued weight loss especially during the period when the grazing is poor. 4. Examination of dead sheep When a veterinarian cuts the dead animal open he will look for signs of liver damage (thickened gall tubes)and flukes in the gall tubes Development of liver fluke inside Cattle When the animals graze in wet areas they take the immature worms which are attached to plants. In side the animal, these immature flukes penetrate through the wall of the small intestine, migrate to the liver and penetrate the liver. The immature flukes will then start to eat liver tissue, forming small tunnels in the process. Immature flukes feed on the liver for the next 6-8 weeks while they are growing which causes severe damage to the liver. Liver damage depends on the number of immature flukes feeding on the liver tissue.By 8 weeks they become adult flukes which will now enter the small bile ducts (tubes) and migrate to the larger bile ducts. These adult flukes attach to the wall of the bile ducts and feed by drinking blood. After a month each adult starts 2 3 plant and form a protective capsule around it. fluke 8 1 rainwater into areas with standing water. Freshwater snails become infected by this stage of the flukes. These flukes will now multiply inside the freshwater snail. produce eggs that are excreted with the dung. Eggs in the dung hatch with an increase in temperature. 1. The shell of the freshwater Spring snail in which liver fluke multiply Summer and autumn Winter Adult liver of and stomach this stage of the stomach parasite it fluke multiply During high rainfall, the flukes that have multiplied inside the freshwater snails are released into the water again. 2. The shell the freshwater At snail in which flukes inside livestock is washed out of the dung by Images supplied by Karen Grobler at Afrivet At this stage, the flukes can swim. The small flukes swim until they reach a plant that grows in the water. They will attach to the to produce eggs (20 000 per day) which go with the bile into the intestine and out with the dung. The thin walls of the bile ducts now become thickened and white and the whole liver can become hard (fibrotic) due to the bodies reaction to this infection. To confirm infection in the live animal, dung must be collected and sent to the veterinarian for tests to determine if there is a liver fluke infection. The newest tests can identify the infection early (from 4 weeks after infection), which will be at the time when the first signs of disease are observed in the case of a very severe infection 17 9