Prevalence, molecular detection, and pathological characterization of small ruminant lentiviruses in goats from Mexico

Abstract

Small ruminant lentiviruses (SRLVs) are one of the main viral agents affecting goats worldwide. They cause a systemic, chronic, incurable, degenerative disease. In Mexico, the B1 genotype of SRLV has been detected as endemic in goats and sheep; however, its pathological characteristics have not yet been evaluated. In this study, sampling was performed to identify the percentage of SRLV positivity in different farms in Mexico. Prevalence rates of 19.6 % and 11.6 % were detected through PCR and serology, respectively. Through a real-time PCR differential test, the prevalence of genotype B was identified. From a chosen case, an SRLV strain was isolated (which was called SRLV/B1/Goat/Mx/INIFAP-1/2013). The phylogenetic analysis revealed that the strain SRLV/B1/Goat/Mx/INIFAP-1/2013 shares a great homology with an American and Asiatic strains of the B1 genotype. Virulence of the isolated strain was analyzed during an experimental infection in kids. The kids did not present clinical disease after the experimental infection. The high viral load values persisted throughout the entire experiment (90 days), and no seroconversion was detected. At necropsy, macroscopic alterations were not observed, except in the lungs. The microscopic lesions in the respiratory tract consisted of moderate interstitial pneumonia, peribronchial lymphoid hyperplasia, and bronchial exudate. In the central nervous system, moderate gliosis, meningeal congestion, lymphocyte infiltration, satellitosis, and demyelination were observed. The virus was systemically distributed among organs; the cerebellum and carpal synovial fluid samples were those with the highest viral load, 5.73 copies of virus per ng of total DNA (log10) and 5.07 log10, respectively. In this study, we identified a strain with high homology to Asiatic strains that manifested low virulence in kids during short infection. Understanding the strains that circulate in the goat population will allow implementing better diagnostic methodologies to propose disease control alternatives for this emerging animal production system in Mexico.