Joint ultrasonography of goats infected by the caprine arthritis encephalitis virus

Background: The most important form of caprine arthritis encephalitis virus in the goat is the arthritic, generally observed in animals over eight months of age. Differently in sheep, there is less arthritis incidence, affecting 2-3-year-old animals. The clinical alterations frequently affect goat joints, and an increase in the joint consistency and size is observed. The objective of the present study was to standardize the ultrasound technique to access joints in animals infected with the caprine arthritis encephalitis virus (CAEV), so that it can be a complimentary support tool for diagnosis and animal management. Materials, Methods & Results: Animals were examined from farms located in the municipality of Teresina, state of Piaui, Brazil. For this, the M-Turbo, Sonosite Fujifilm ultrasonography apparatus was used, attached to a linear transducer with 10-13 MHz frequency. The ultrasound examination analyzed three regions: patella-humerus joint, carpal and tarsal joints. The patella-humerus joint was characterized by its concave convex surface. The surface of the head humerus was a fine hyperechoic line composed by the junction between the joint cartilage and the subcontinent bone. The sub patella muscle was visible and its fibers present a parallel and hypoechogenic pattern compared to bone tissue. A discreet muscle edge with echogenicity was observed separating the sub patella and supraspinatus muscles. The surface of the proximal and distal rows of the carpal bones was characterized by fine hyperechogenic lines that formed acoustic shadow. Regarding the bones of the tarsal joint, the surface of the central tarsal joint bone was observed centrally as a fine, hyperechogenic line. The third tarsal joint bone was visualized on the left side and was represented by a thick hyperechoic line, while the fourth tarsal joint bone was observed to the right with a hypoechogenic surface and both formed acoustic shadow. Discussion: Joint inflammation caused by other diseases, such as derived from bacteria of the Micoplasma genus can suggest similar semiological aspects and can present positive results for the joint clinical index. Studies carried out have established measurements of the joints of animals affected by various degrees of arthritis, where absolute values equal or less than 5.5 cm would be indicative of negative arthritis diagnosis, variations between 6.0 and 6.5 cm would be considered suspicious and when equal or greater than 7.0 cm they would be positive. From the anatomical point of view, ultrasound assessment of the joints of the normal animals showed a morphological pattern as observed in dogs, horses and humans. The loss of echogenicity, surface erosions and exposure of subchondral bone observed in goats infected with CAEV were also reported in dogs with patella-humerus osteochondrosis, by the presence of a cartilage flap seen radiographically, or even as cracks, characterized by a hyperechoic line parallel to the subchondral defect, in the ultrasonography examination. The lesions observed in the ultrasound examination showed various degrees of osteoarthritis, with the presence of sound hyperreflection, hyperechogenic areas, cartilage lesions with erosion of the subchondral bone and loss of anatomic limits, and these characteristics were described for the metacarpal phalangeal and metatarsal phalangeal joints of dogs submitted to routine radiographic examination. The ultrasound examination of the joints of normal goats and goats infected with caprine arthritis encephalitis virus allowed the comparative description of normal anatomy, evolution of joint and adjacent soft tissue lesions, generating valuable clinical and surgical information.