12 February 2024
Be vigilant about livestock diseases and parasites that may occur during autumn, especially hairworm, coccidiosis and cryptosporidiosis, which can cause significant harm to farmers, says Dr Faffa Malan, managing director of the Ruminant Veterinary Association of South Africa (Ruvasa).
Malan is responsible for collecting disease reports and other conditions in livestock reported by veterinarians across South Africa so he can issue monthly reports to the veterinary and agricultural industries.
Using historical reports and charts that Malan regularly compiles on various diseases and conditions, he can also forecast what farmers should be aware of during summer, autumn, winter and spring so they can take preventive measures to protect their herds.
African Farming spoke with him about what farmers can expect this autumn and what they should do.
For effective preventive control of prevailing diseases that cause significant damage, cattle, sheep and goats should be vaccinated against various diseases before the rainy season.
Diseases for which good vaccines are available include clostridial diseases such as black quarter, pulpy kidney (especially where farmers feed poultry litter), enterotoxemia (such as common, blackleg, head and bacillary enterotoxemia), enzootic abortion, E. coli, dermatophilosis (sheep), redwater (cattle), lumpy jaw and pneumonia.
Other diseases that also occur regularly include eye diseases, abscesses (do not cut open in a crowded passage, as other animals risk being infected) and foot rot.
Also, be alert to deficiencies in essential minerals and poisoning with urea and plants.
Be prepared to provide timely protection to animals against severe cold now that it is almost autumn.
“Farmers who lamb their ewes in March can expect particularly significant problems with coccidiosis, cryptosporidiosis and hairworm,” says Malan.
“Although one would expect roundworms to occur only in summer, there are still many other worms as well, such as hairworm and nodular worm in sheep, that farmers should be aware of.”
Hairworm
Based on last year’s charts of parasites, farmers can expect significant hairworm infestations as it continues to rain in many areas. This time last year, veterinarians in all nine provinces reported deaths due to hairworm infestations. This is because sheep and goats’ iron reserves are depleted as hairworms use large amounts of blood, causing severe anaemia.
The obvious sign of severe hairworm infestation is bottle jaw; a swelling under the sheep or goat’s lower jaw.
The farmer can also examine the colour of the conjunctiva and compare it with a FAMACHA card. This method and card were developed by Malan and fellow veterinarians Jan van Wyk and Gareth Bath, all from Pretoria. A bright red colour indicates a healthy animal, while a pale conjunctiva is a sign that the animal has anaemia. The farmer can then treat only those animals and not the entire herd at great expense.
<caption> Farmers can compare the colour of the conjunctiva with a FAMACHA card. A bright red colour indicates a healthy animal, while a pale conjunctiva is a sign that the animal has anaemia, which can be caused by severe hairworm infestation.
Resistance
“The major problem is that many farmers do not know if the worm remedies they administer are still effective because resistance gradually builds up in the worms when the same remedy is continuously administered,” says Malan.
This can be determined by taking faecal samples before and after dosing to determine the number of worm eggs (faecal egg count reduction test). This task can be performed by a veterinarian who can then recommend an alternative worm remedy.
Lambs born in March are susceptible to milk tapeworm, with symptoms including diarrhoea, emaciation, pot belly and weight loss. The farmer should only dose those lambs.
Diarrhoea
If there are many wet areas on the farm, and if the ewes and lambs sleep in kraals at night, coccidiosis may occur. If lambs have diarrhoea, it is a noticeable sign that they have coccidiosis.
Diarrhoea can also be a sign of cryptosporidiosis, which can be fatal. Malan recommends that farmers follow a good management programme and that lambs receive good quality colostrum milk after birth to receive maternal immunity.
However, the condition is that the herd’s immunity must be high, otherwise the colostrum is weak. The quality is determined by the ewe’s nutrition and general health. Therefore, seek expert advice on the right steps to ensure good colostrum, especially nutrition and vaccines against prevailing diseases.
Flukes and parafilariasis
If the cattle graze in wet camps and vleis, the farmer must take precautions against liver fluke. This is caused by water snails, which are the intermediate host between the flukes, such as liver fluke and rumen fluke, and the cattle.
Clinical signs in cattle and small stock are anaemia and bottle jaw, as well as black diarrhoea in rumen fluke. The correct control is dosing with the recommended agents.
Parafilariasis mainly occurs in the Bushveld and the coastal area of KwaZulu-Natal. It is visible as false bruises when the animals are slaughtered and looks like bloody streaks on the sides and neck.
According to Malan, the false bruises are caused by the internal female parasite and occur under the skin when she lays small worms. When flies sit on the infected streaks, they can transmit the parafilariasis to other animals by sitting on their eyes. After five months, the cycle is then complete again.
Infected animals must be treated with macrocyclic lactones. This is the farmer’s task because it takes 70 days before the animals are slaughtered, when the bruising has cleared up.
Ticks
Blue ticks remain a major problem in Southern Africa and transmit dangerous diseases, especially African and Asian redwater in cattle. The latter causes large-scale deaths. “Cattle simply die. You see nothing wrong and the next moment the animal dies,” says Malan. Discuss a comprehensive vaccination programme with your veterinarian to prevent this.
There are several resistant blue tick strains. Tests can be done on ticks present on the farm to determine if the agents used by the farmer are still effective.
The organism that causes anaplasmosis (tick-borne gall disease) is transmitted by blue ticks and horseflies. Clinical signs are hard faeces causing constipation and jaundice seen on a yellow conjunctiva.
The heartwater tick mainly occurs in the Bushveld and on the east coast. Clinical signs of heartwater are neurological symptoms. It looks like cattle, goats and sheep are “riding bicycles”; in other words, they lift their legs high. Then they lie down and die. Treatment must start immediately when there are clinical signs – such as when the drool starts flowing – to ensure effective control.
Sweating sickness can be caused by the brown ear tick during autumn. They secrete a toxin that makes the cattle sick, then the cattle sweat through the skin. These ticks mainly attach to the tail switch where they are not easily visible. There are agents available to treat sweating sickness.
Onderstepoort Biological Products (OBP) has blood vaccines available to prevent tick-borne diseases.
Knot disease
Malan says knot disease occurred extensively across Southern Africa last year, even in autumn. This proved that many cattle were not vaccinated against it before the rainy season.
“Plan ahead so that all your animals are vaccinated before the next rainy season because it is an insect and tick-borne disease. Good vaccines are available.”
Bovine ephemeral fever or three-day stiffness disease is also transmitted by insects. If three-day stiffness disease and knot disease break out, the cattle should be taken to higher areas of the farm where there are fewer insects. They can be sprayed with insect repellents there.
Redwater fever can break out at any time during a wet summer because large numbers of mosquitoes breed then. Malan encourages farmers to vaccinate their animals against it to provide immunity. “Don’t think it can’t happen to you just because redwater fever hasn’t occurred in the past few years with heavy rains. It can break out any year.”
Blue tongue and other diseases
Blue tongue is one of the biggest cattle diseases and is a viral disease against which animals must be vaccinated preventatively. There was a shortage of vaccine at one stage but sufficient stock is now available from Design Biologix and OBP.
Snotty nose disease, which is especially associated with wildebeest, occurred widely last autumn and cattle died on a large scale. Therefore, keep wildebeest and cattle apart as far as possible.
Viruses causing respiratory diseases also occurred last autumn. Good vaccines are available against them.
Mange and scabies are viral diseases in sheep and goats, while mange mainly occurs in calves. A veterinarian can make a vaccine for a farmer.
Farmers should always be mindful of lameness. Count bones lying in the field after the many fires, remove dead animals and birds from water troughs and thoroughly clean the troughs. Revaccinate animals two to three times before feeding them chicken manure.
Brucellosis
According to the law, heifers must be vaccinated with strain 19 vaccine at four to eight months. RB 51 vaccine can be administered at any time except on pregnant animals because they will abort.
“Brucellosis is out of control. Farmers must apply very good biosecurity to keep it out of their herds,” says Malan.
Test the entire herd. Any animal purchased must be quarantined for 28 days so the necessary tests can be done.
Reproductive diseases
Malan is concerned about the large extent of reproductive diseases, such as trichomoniasis and vibriosis. Herds must be tested now so that farmers can know in time if the diseases occur on their farms. Therefore, it is necessary to decide whether bulls should be culled and replaced.
The recommended action is to test all cows for pregnancy and scrape bull’s sheaths. Cows that are not pregnant should be culled to promote herd fertility, even if they do not have a reproductive disease.
Biosecurity
In addition to the necessary treatment – whether preventive or curative – farmers must maintain good biosecurity. Therefore, take all precautions on the farm to prevent diseases from entering with new cattle.
This applies especially to contagious miscarriages and foot-and-mouth disease. Maintain fences and gates and control the movement of people and vehicles. Don’t allow just anyone onto the farm and implement a comprehensive vaccination programme, says Malan.
