Veterinary Preventive Medicine-II

DIAGNOSIS

• The highly contagious nature of the disease, profuse salivation and the presence of typical raised vesicles with blanched covering epithelium filled with a clear straw colour fluid are usually pathognomonic.

Samples to be collected

• Vesicular fluids
• Epithelial fragments of recent vesicles especially from lesions of tongue, feet, udder or lips of about 1 gm
• Recently dead animals - pieces of cardiac muscle and pancreas
• Transport medium-The samples should be kept in a solution of phosphate buffer saline at pH 7.6 which contain equal parts of glycerol and 0.00196 phenol red indicator.
• The outside of the container should be disinfected with 4% Na₂ Co₃ or 0.2% citric acid.
• The container is wrapped with cotton wool and kept in a sealed fluid tight container packed in a strong outer box of wood and sent to the lab.

By Serological tests

• Complement fixation test (CFT) is the most commonly used and important test to identify the type of virus. The suspension of the original serum is used as antibody.
• Virus and serum neutralization tests may be used to detect specific antibodies in the serum of recovered animals or for identifying the causative virus.
• The test is done with known hyperimmune sera
• Gel diffusion test, Fluorescent Anitbody Test (FAT), Immunoperoxidase test (IPT) and Iso electric focusing are also useful
• Enzyme Linked Immunosorbent Assay (ELISA) and Polymerase Chain Reaction (PCR) are now standard methods for virus detection and typing in reference laboratories

Cell culture

• Monolayers of bovine thyroid or pig kidney cells are inoculated and CPE develops within 24-48 hours at 37°C.

Mouse inoculation

• The suspected material is inoculated in unweaned mice and the mice die within 1-7 days.

Cross immunity

• For accurate identification inoculation of groups of susceptible and immune cattle are used.