Cattle, sheep and goats can be infected by three types of helminth, or internal parasite. These are roundworm, tapeworm and fluke. This paper discusses the control of roundworm in these three species. Roundworms are found all year round and live in many sites in the animal, including the eye, lungs, the body cavity, beneath the skin and most commonly, the gastro-intestinal tract. They lay large numbers of eggs, which are usually passed out in the dung of the host animal. In some cases the eggs hatch in the intestine and the larvae are passed out. There are 14 different roundworms affecting sheep, goats and cattle in this country.
It is important to understand the life-cycle of the roundworms so as to implement a strategic and effective dosing program. Very simply, roundworms live, usually in the intestine of the animal, where they suck blood, eat tissue or eat the stomach contents thus depriving the animal of nutrients. The female will lay eggs which pass out with the dung. If conditions are right the larvae hatches in a few days, then goes through a series of processes until it reaches a stage where it can infect the animal. In some helminthes, this process involves an intermediary host. The animal becomes infected while grazing, eating food or water contaminated with the larvae or eating the intermediate host, such as a mite. The larvae mature in the intestine and mate. The female lays her eggs in 2 – 4 weeks after infection and begins the cycle again.
Life-cycle of the roundworm (single host)
Roundworms of Cattle, Sheep and Goats of Southern Africa
Eye worm (Thelazia) In cattle, rarely in sheep. Not particularly harmful and does not cause ophthalmia, however a large number may make the animal more susceptible to ophthalmia.
Abdominal worm (Setaria cervi) Found in the abdomen of cattle, sheep and horses. Quite harmless, the larvae reach the bloodstream and are transmitted by blood sucking flies.
Lungworms Found in cattle, sheep and goats, horses, mules and donkeys. Can be very harmful, especially in sheep and goats. The worms live in the small bronchi of the lungs. When eggs are laid, they are coughed up and swallowed by the animal. The sheep can get respiratory complications, lose condition rapidly and die.
Zig-zag worm (Gongylonema) Found in the membrane lining the gullet and the rumen, these appear to be completely harmless, even in large numbers.
Parafilaria Bovicola (Parafilariasis) Only affecting cattle, it lives in the subcutaneous tissue on the forequarters. It causes a large subcutaneous lesion of green/yellow or dark red appearance; looking like bruising (false bruising). The lesion is the reaction of the animal’s body to the irritation caused by the parasite. Although the health of the cattle does not seem to be harmed by the parasite, at slaughter, large parts of the carcass are discarded due to the lesions and the carcass is down-graded. As flies are an intermediate host to this parasite, it is important to control biting flies. (See Fly Control)
Wireworm (Haemonchus contortus) Occurring in sheep, goats and cattle, this worm is the most common and most harmful of the roundworms. They suck blood, spilling so much that the contents of the abomasums, where they live, turn red. Anaemia develops, the animals get an oedematous swelling under the jaw and become thin, weak and breath rapidly. The larvae require moisture for their development and therefore there are often massive infestations after the rains begin. However, they can survive in the undeveloped stage through the winter if there is some moisture around.
Brown Stomach-worm (Ostertagia) lives in the abomasums of cattle, sheep and goats, and is particularly troublesome in Angora goats. The life-cycle is similar to that of the wireworm and symptoms of infestation are similar.
Bankrupt worm (Trichostrongyles and Cooperia) infect cattle, sheep and goats, living in the small intestine and abomasums. Sheep are most affected and can die from heavy infestations. The life-cycle is similar to that of the wireworm except that the bankrupt worm can survive through a dry winter. The larvae can survive in the egg for a year if conditions are not favourable for hatching. The eggs will hatch with the first rains and when animals graze these pastures a massive infection will result. The sheep start purging, become paralysed in the hindquarter and some die. Strongyloides does not even need to be swallowed but can burrow into the skin of the legs, then migrates to the lungs, causing respiratory distress and diarrhoea.
The cattle bankrupt worm Cooperia is fairly common and is quite harmful, but not as devastating as in sheep.
Hookworms This is a large family of blood-sucking worms which live in the small intestine of their hosts, which include cattle, sheep, goats, horses, dogs, cats and man. They suck large amounts of blood from the host and cause bleeding into the intestine. Young animals are particularly affected. The hookworm enters the body of the animal or man through the skin, migrates via the bloodstream to the lungs, is coughed up and swallowed to the intestine, where it begins the cycle again. A sheep hookworm Gaigeria causes the host sheep to lose some much blood that 24 can kill a healthy adult sheep in a few days.
Ascaris worm (Ascaris vitulorum) Found only in calves kept in pens, it is closely related to the Ascaris of pigs. The worms lay many eggs which pass into the pen via the dung and can infect a contaminated area for years. Pens must be regularly cleaned and disinfected.
Nodular worm (Oesophagostomum) Commonly infecting sheep and goats, while different species infect cattle, pigs and man. The worms form protective nodules in the intestine of the host, making them very difficult to kill. Toxic secretions from the worm cause erosion of the gut wall and eventually these secretions enter the body of the animal, basically poisoning the whole system. Sheep grow thin and weak, emaciated and die.
Large-mouthed worm (Chabertia ovina) Lives in the large intestine of cattle, sheep and goats. Its habits and life cycle are similar to the hookworms. They cause anaemia and loss of condition.
Whipworm (Trichuris) A relatively harmless worm which lives in the mucous membranes of the large intestine of cattle, sheep and goats. It is sometimes mistaken for the nodular worm, but causes far less damage.
Worm Nodules of Cattle (Onchocerca) The worms live in subcutaneous nodules, especially along the brisket. The larvae enter the bloodstream and are swallowed by blood-sucking midges, which then transmit the infection to other animals. Although the worm is not harmful to the animal, the infected carcass is down-graded and revenue from beef is lost.
SYMPTOMS OF ROUNDWORM INFESTATION
Some animals can carry a worm burden and appear unaffected, showing no symptoms. Young animals and animals under stress due to malnutrition, disease etc are more affected. However, even healthy adults, if they have a large worm burden will show symptoms and a loss of production. Young animals show stunted growth and development, are pot-bellied , have poor coats and may have diarrhoea. Animals with many blood-sucking worms can shows signs of anaemia. In extreme cases they may die.
PREVENTION AND CONTROL
• Animals in good condition are definitely more able to tolerate worm infestations – another good reason for feeding livestock well. Young animals are more susceptible and require more care.
• Calf pens, dairy yards, collecting pens, kraals, anywhere that animals are in constant close confinement should be regularly cleaned and disinfected and manure collected and disposed of to kill infective eggs and larvae.
• Pasture rotation and paddock resting will help to break the cycle. Where paddocks are heavily dunged, discing or harrowing the manure into the ground can help.
• Avoid grazing animals in low-lying wet areas in summer if possible.
• Identify the species of worms on your farm by taking dung samples into the laboratory for egg counts and identification. The worming regime will depend on these results. It is also a good idea to take samples before and after dosing to check the effectiveness of the product against the worms on your property. A sample dosing programme, depending on the worm load and species present is to dose all animals 3 weeks after the first heavy rain to kill infective larvae picked up with the rainfall. Dose again in the middle of summer and after the first frosts in Autumn, so that animals go into the Winter clean. Young stock, particularly dairy calves will requie more frequent dosing.
• Anthelmintics (dosing medicines) come in various forms – injectables, by mouth and pourons. Some have combination effects against roundworm and fluke.
DECTOMAX INJECTABLE is effective against most roundworms of sheep, cattle and goats, parafilaria and sheep scab.
FINIWORM is registered for cattle, sheep, goats, horses and pigs and is effective against most roundworm including migrating lungworm, nodular worm.
NILZAN BOLUS is an anthelmentic for the treatment and control of gastrointestinal and pulmonary nematode infestations and chronic fascioliasis in cattle.
SYSTAMEX is an effective treatment for susceptible strains of Small Brown Stomach Worm, (including inhibited larvae), Stomach Hair Worm, Barber’s Pole Worm, Small intestinal Worm, Thin-necked Intestinal Worm, Nodule Worm, Black Scour Worm, Hookworm, Tapeworm and Lungworm in cattle.
VALBAZEN® is remedy for roundworms and milk tapeworms in cattle. Prevents roundworms eggs present in the animal at dosing from hatching.
VALBAZEN® FOR SHEEP AND GOATS is a remedy for roundworm, lungworm, milk tapeworm and liver fluke in sheep and goats. Prevents roundworm eggs present in the animal at dosing from hatching.
Handbook of Stock Diseases: Monnig and Veldman