Meet the ‘other’ critters that might be freeloading in your stock! Tapeworm is a mostly harmless parasite of young lambs. Lungworm is most common in young calves and can cause serious disease if left unchecked. Liver fluke can be a cause of ill thrift on some farms. Learn about these worms and their management here.
What you see
Tapeworms are a large, easily visible parasite. You can see segments in the faeces of young lambs. By eight months, many lambs will have naturally got rid of most of their tapeworms, without having been drenched for it.
Life cycle
Tapeworm segments passed in lamb faeces have eggs inside them. Mites on your pasture consume the eggs and are the ‘intermediate host’. Grazing lambs eat the mites, and the immature tapeworm then develops to maturity in the small intestine.
Most at risk
We have little evidence of tapeworm infections reducing lamb growth rates. While other intestinal worms feed by physically browsing the gut edges, tapeworms absorb their nutrition through their skin. Thus they are far less irritating to the gut than nematode worms.
Identification
Visible tapeworm segments in lamb faeces. Tapeworm eggs are a different shape to other worm eggs and can also be seen in lamb faecal samples.
Treatment/prevention
Some lamb drenches contain praziquantel, which will kill susceptible adult tapeworms. But a high and unreported level of praziquantel resistance is now likely in NZ tapeworms; positive tapeworm eggs counts are becoming more common from lamb drench checks. Wormwise advocates using the most effective drench family for other nematodes on the farm, for early season lamb drenches, rather than choosing a product specifically for tapeworm treatment.
What you see
Weak, thin ewes, often from late autumn through to lambing. Ewes may show ‘bottle jaw’ (soft fluid swelling under the lower jaw) due to anaemia or blood loss. In worst cases, ewes die of liver failure. Post-mortems of tail end ewes are the best way to determine if liver fluke is an issue on your farm. Sheep do not develop immunity to fluke and infections can build up over several seasons, so older ewes are a good choice for post-mortem.
Cattle develop some immunity to fluke. But in areas of high fluke challenge, milk production and liveweight gain can improve after treating cattle for fluke. Affected cattle lose weight, eat less and may show bottle jaw similar to ewes.
Life cycle
Fluke eggs pass out in the dung of sheep and cattle. The eggs need to be in water before they hatch into larvae. These are eaten by a freshwater snail. The life stage that comes out of the snail forms a cyst on blades of grass near the snail habitat and is eaten by grazing animals. After being ingested, this stage comes out of the cyst and migrates through the liver, settling in the bile ducts. The fluke then matures and lays eggs, to repeat the cycle. Autumn and early winter are peak infection times. Once temperature drops below 10 degrees, snail activity ceases and the life cycle halts for winter.
Most at risk
Stock grazing damp areas where the snail host is present. Worse after droughts where animals have grazed down hard into damp areas looking for green feed. Under-fed MA ewes are most at risk. Fluke is found in most areas of the North Island and the West Coast of the South Island.
Identification
Post-mortem: Examine the underside of the liver (the surface that sits against the gut, not the diaphragm). Adult fluke may be seen in the bile ducts if you cut into them. In bad infections they will also come out of the liver tissue.
Laboratories can also test sheep faeces to look for eggs. This is a sedimentation test and is different from a standard faecal egg count. Cattle faeces often won’t show many eggs as cattle develop some level of immunity to fluke.
For both sheep and cattle, an ELISA blood test will confirm fluke have been present, although antibodies persist for about three months after infection.
Prevention/treatment
Gather as much evidence as possible to decide whether fluke is of clinical significance on your farm before treating. Many fluke treatments also contain other drench families and unnecessary use of these can build resistance in other parasites.
Good nutrition reduces ingestion of infective stages. Minimise stock access to waterways.
Preventive treatments may be necessary on some farms. Benzimidazole (white) drench will kill susceptible adult liver fluke, so young stock regularly drenched with combinations containing BZ will get some fluke control by default. Products containing triclabendazole and closantel kill most stages of the life cycle of susceptible fluke and are more appropriate targeted treatments for adult sheep. Clorsulon injection is a convenient way to treat cattle for adult fluke.
Dictyocaulus viviparus is the most common and problematic lungworm species in cattle..
What you see
Signs usually start two to three weeks after infection. Listen for rattly shallow breathing and a harsh cough. Calves lose weight, may appear tucked up and have a harsh coat.
Life cycle
Eggs hatch to L1 larvae within the airways. These are then coughed up, swallowed and pass out in dung. Within seven days they moult through to L3 and spread from the cow pat across pasture. Eaten by calves, larvae penetrate the intestinal wall and are carried to local lymph nodes, where they moult to become L4 larvae. They then travel via the lymphatic system to the jugular vein and into the heart, which pumps them to the lungs. Here they complete their final moult some 14 days after ingestion. Sexually mature adults can be found about 8 days later.
Over-wintering: Lungworm can become inhibited in R1 cattle, re-commencing development in spring. This can sometimes contaminate pasture for calves if you have few other animals to ‘vacuum’ pastures.
Identification
The best way to identify worms in faeces is larval recovery, not FEC.
Post-mortem
At post-mortem white worms (about 2 cm long) will be obvious in frothy material in the airways of lungs.
Most at risk
Young hand-reared calves introduced to contaminated pasture, especially if their first drench has been delayed or a long gap has been left between early drenches of these very young calves. A classic scenario is sick calves at New Year when they were due a drench just before Christmas! Older calves and young dairy cows (first and second calvers) under feed or disease pressure sometimes succumb to clinical lungworm. .
Treatment/prevention
Wean calves onto pastures free of very young calves the previous year or onto pastures thoroughly cleaned by other stock classes since. Don’t defer or miss early drenches for newly weaned calves if they’re grazing contaminated pasture. Lungworm almost never occurs in calves reared on cows and weaned in autumn.
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