By Vida Booysen

Above-average rainfall in April affected large parts of South Africa’s interior, compelling livestock farmers to take even greater care of their animals. Be aware of these diseases that accompany persistent wet weather.

Experts warn that waiting until it rains to take precautions against diseases is dangerous because there is not enough time to complete the vaccination programme. Additionally, every herd on the farm needs to have a biosecurity plan developed in cooperation with a herd veterinarian.

African Farming asked Dr Johan van Rooyen, a veterinarian from Steynsburg, Wikus Bekker, a sheep farmer from Edenburg in the Southern Free State, and Mornay Verster, a cattle farmer from Westminster in the Eastern Free State, for their advice on how farmers can keep their animals disease-free in very wet conditions.

Weaned calves vaccinated against pneumonia

Verster, whose Le Roc Brangus stud has earned a reputation for hardy, field-adapted animals, says that with the wet and cold weather approaching, farmers will encounter more pneumonia in weaned calves when they wean the animals this year.

“At Le Roc, we inject all calves three to four weeks before weaning with a preventive respiratory vaccine.”

While administering this vaccine, the animals are also vaccinated against blackquarter with Clostrivax B+ (reg. no G4483, Act 36 of 1947), which protects against all blackquarter diseases, botulism, anthrax, and Type A1 pneumonia. When the calves are weaned after four weeks, both vaccines are repeated to achieve their full effect.

Verster also provides farmers with tips on managing the vaccination process. “We clip the tail tips of all calves we vaccinate, making it easy to see if the calf has already received its first vaccination.”

Be aware of general health

Bekker says that when it’s wet, parasite loads tend to be higher than usual, and sheep farmers must be mindful of their animals’ overall health.

“The parasite that usually does the most damage is the wireworm. You must dose against it – more than you normally would. Preferably, you should have experience and the right eye to know whether it’s necessary to dose. If in doubt, you should dose with any wireworm remedy as a precaution.”

He also advises farmers to monitor their animals’ general health and boost their immune systems with vitamin and mineral supplements. “It helps with the animal’s general health because if the sheep’s general health and immunity are good, they won’t easily get footrot in wet weather.”

Liver fluke is a parasite that sometimes occurs in years with excessive rain, says Bekker. “It’s not something we usually get in the southern Free State, but in extreme cases, it can occur in standing water due to the wetness. Fortunately, it still rains often, and the water flows strongly.”

He warns that this parasite can cause considerable damage to a herd and that special remedies must be obtained against it, not just an ordinary broad-spectrum dosing agent.

Bekker advises farmers to move animals from wetland camps to higher ground when it is wet. “Sometimes you only have so much grazing available, and it’s not always possible, but try to stay out of low-lying areas when it rains continuously.”

He says there are naturally more mosquitoes and midges in wet conditions. “Many guys spray dipping agents around the sheep’s head and nose, keeping some of these bugs away. The midges transmit diseases like bluetongue. But bluetongue is a disease against which you should have started vaccinating long ago. It’s a whole series of vaccines that you need to administer.”

Protect newborn lambs

Regarding herd management during wet seasons, Van Rooyen states that wet and cold weather poses a danger to farm animals due to the chill factor caused by low temperature, wind, and water. “If a lamb is born on a windy, rainy night, it will only survive one hour if it doesn’t start drinking and find shelter.”

Cold, wet weather can also interfere with the intake of colostrum, the first milk that contains large amounts of antibodies and protects a lamb and calf against infectious diseases. In bad weather, it sometimes happens that the ewe and the lamb don’t immediately work together to ensure colostrum intake, he explains. “The newborn animal must get colostrum within six hours to be absorbed into the bloodstream. If this doesn’t happen, the animal is susceptible to infectious diseases.”

“A good example is pulpy kidney, a disease caused by the toxins of a bacterium. A lamb that has received adequate colostrum within six hours will be protected against the disease for up to six months, but lambs that didn’t receive colostrum can start dying from pulpy kidney as early as three to four weeks old.”

Don’t wait until it rains

Van Rooyen warns that wet years also increase insect populations, which can trigger outbreaks of diseases such as bluetongue in sheep, three-day stiffness sickness in cattle, and Rift Valley fever.

“Livestock owners should protect animals against these diseases with yearly preventive vaccinations. It’s dangerous to wait until it rains because there isn’t enough time to complete the vaccination program. There is often also a shortage of vaccines because everyone scrambles to get vaccines after outbreaks have already begun.”

Van Rooyen says that livestock farmers must be cautious when vaccinating herds during outbreaks because the viruses can be transmitted through the needles. “In such a case, a new needle for each animal is non-negotiable.”

Wet weather also creates ideal conditions for various foot problems, such as footrot, virulent footrot, hoof abscesses, and navel string infection caused by the same microbes. “The footrot bacteria can survive and multiply in the soil and are therefore extremely dangerous in lamb pens, corrals, and lands.”

He recommends treating sheep and cattle preventively with a footbath containing disinfectants or zinc sulfate. “When cases already occur, applying good internal biosecurity and treating animals with antibiotics and regular footbaths is extremely important. The herd veterinarian can draw up a protocol for this.”

Remove infected animals from the herd

Wet and rainy conditions can also lead to skin diseases, such as lumpy wool (Dermatophilus congolensis) in sheep and senkobo disease in cattle. Additionally, it can spread to goats, horses, and wildlife.

Van Rooyen says this disease can be combated with disinfectants and zinc sulfate. In sheep, it’s sometimes necessary to also inject antibiotics. “Wool sheep susceptible to lumpy wool should be culled (especially rams), if possible because skin diseases tend to occur more in certain families. The infected animals should also be removed from the herd to reduce further spread.”

Fly strikes often become problematic during periods of heavy rainfall, as the wet fleece provides an ideal breeding ground for maggots after flies lay eggs in damp areas. Van Rooyen recommends preventive treatment with toxins or growth regulators to protect the animals.

With all animal diseases, biosecurity is essential, and a herd veterinarian should be consulted for each herd and flock to establish a biosecurity plan. Additionally, the herd veterinarian should review a farm health and production plan annually to adapt to changing circumstances. Keeping records to ensure traceability is also becoming increasingly important. With preparation and sound practices, livestock farmers can manage risk even in a severe rainy year.