A silent killer of dairy farming

Bovine viral diarrhoea virus (BVDV) is an important viral pathogen of cattle all over the world, spread through body fluids. It destroys the health, fertility and productivity of affected cattle. Infections with BVD virus can vary from subclinical to manifestation of clinical signs such as oral cavity lesions, elevated body temperature, decreased milk production, diarrhoea, nasal discharge, death and abortion. Virus can establish two types of infections in the animals; transient and persistent. BVD infection during early stage of pregnancy will result in the birth of live calves that remain persistently infected (PI) with the BVD virus throughout their lives meaning they can spread vast quantities of BVD virus to susceptible cattle.
Some PI calves appear to be normal and healthy; however, they have poor immunity, often fail to thrive and are prone to mucosal disease, the fatal form of BVD. Their offspring will also be persistently infected with the BVD virus resulting in low fertility, abortions and ill-health. Milk production of PI heifers is essentially halved; their immune system is affected making them susceptible to other infections like pneumonia. Transiently infected animals usually cleared the virus from body due to self clearance mechanism.
Semen of bulls are potentially silent killers, if untested for BVD and farmers are warned to ensure any bulls or their semen for insemination coming onto their farms are BVD free as the virus inflicts the greatest harm to cows during pregnancy. Farmers are also advised to make sure that any animal bought onto the farm are BVD tested.
In Pakistan, Unfortunately little attention has been paid until now to investigate this problem. Dairy farmer and professional mostly correlate cause of abortion to brucellosis while ignoring the involvement of BVD virus. In many developed countries, control programs are being implemented for eradication of this economically important disease. The success of all these programs depends on the ability to detect all PI animals at a young age. Undetected PI calves are the main source of the infection within herds. It is recommended that all newborn calves should be tested; these animals are worth a lot of money and any animal with BVD is not, economically, worth keeping.
Precise and economical assays for confirmation of PI cattle with BVDV would be best, since it would allow prevention of BVDV spreading on farms. University Diagnostic Lab (UDL), University of Veterinary and Animal Sciences, Lahore is providing diagnostic facility for BVD infection. Blood or tissue samples can be taken for diagnosis. It is advised that farmers must contact their vet before taking samples. Retesting is required if a carrier is detected. It is pertinent to mention that BVD is a very complex disease, and farmers wanting advice, should talk with their veterinarian to eradicate this problem from Pakistan.
Dr Arfan Ahmad, Prof Dr Masood Rabbani
UVAS, Lahore