Parafilaria historically has been relatively geographically limited, but we are starting to see it spread further. It can be identified on farm by the characteristic bleeding spots seen at this time of year but is not visible in possibly infected weaner cattle going into the feedlot.
The Start of Bleeding
Visible Bleeding Spots
Severely affected cow
Parafilaria causes significant economic losses when untreated cattle are slaughtered, and parts, or the whole, of the carcass are condemned. Cost-effective treatments are available at both farm and feedlot level but requires awareness that the cattle are being exposed to the disease and timeous treatment pre-slaughter.
Where farmers are feeding and slaughtering their own cattle, awareness of this disease in their area can allow them to proactively limit significant losses and ensure that the disease is effectively managed.
Consult your vet if any signs of this disease are observed, so that appropriate treatment protocols can be established to limit exposure, and the broader industry can be aware of the distribution and process livestock accordingly to limit the cost of disease.
It is essential that the veterinarian in charge of the health program at a feedlot know the origin of calves in order for the correct treatment at the start of the feedlot phase and/or action follow up treatments if needed
Background Information
Parafilaria is a filarial roundworm that lives under the skin in cattle. The adult female worm makes a small hole through the skin where she deposit eggs/larvae. Flies are attracted to these wounds, and when feeding on the blood they will ingest the larvae, which will then develop further in the fly.
The third stage of the larvae is then transmitted to cattle when the fly feeds on eye secretions or small wounds on the cattle. The larvae will migrate to areas under the skin of the neck, over the ribs or the flank of cattle where they then grow into adults over the next 7-10 months before the females make a small hole again to deposit her eggs.
The Economic Loss Caused by Parafilaria
Although the worms under the skin don’t cause a severe production loss in cattle, the loss arises when these cattle, or their offspring, are slaughtered. The migrating worms under the skin cause lesions, called false bruising. These must be trimmed out at slaughter.
It can lead to losses of 0,5kg or more per lesion, and in severely affected carcasses the whole carcass is condemned for human use. Thus, losses of between R30 (single trimmed lesion) to more than R10 000 if carcass is condemned can be incurred.
Disease Distribution
Parafilaria mostly occurs in the warm bushveld areas of Limpopo, North-West and Kwazulu-Natal but the parasite is spreading to more areas as reported by veterinarians through the disease reporting system.
Disease Prevention
To prevent losses at slaughter, cattle, and specifically weaner calves that go through a feedlot phase, must be treated against parafilaria at least 60 days before slaughter for the filarial worms to be killed and the lesions to heal. Although calves from affected areas can be infected with parafilaria, they will not show bleeding spots during the 120 day feedlot phase due to the long development period of the worm of 7-10 months.
It is essential that the veterinarian in charge of the health program at a feedlot know the origin of the batches of calves in order to advise on the correct treatment at the start of the feedlot phase and/or follow up treatments if needed. Better awareness of this disease will reduce the cost of disease on the industry, at no cost to the farmer.
