Retroviruses are a diverse group of animal pathogens that causes OPA, maedi, CAE and enzootic nasal tumour in small ruminants. The present investigation was designed to study the prevalence of retroviral diseases in north Indian sheep and goat population along with its etiological characterization and immunopathological aspect. Total of 1177 samples (serum-342, blood-233, tissue-468, nasal swab-134) were collected from different places of northern India and screened for JSRV, MVV, CAEV and ENTV. Overall SRLVs seroprevalence of 19.58% was observed, in which seropositivity was higher in sheep (22.9%) as compared to the goats (15.59%). DNA was extracted from the samples and subjected for the specific PCR for the detection of retroviral agents. JSRV nucleic acid was detected in 3.5% of samples, which includes 3.79% and 3.06% of sheep and goat, respectively. MVV nucleic acid was detected in 10.41% of samples, which comprised of 8.7% and 12.6% of sheep and goats, respectively. All the samples were found negative for CAEV and ENTV. Partial JSRV genome sequences of 4587 bp (CDG16/JSRV/Sheep/India) and 5886 bp (CDG34/JSRV/Sheep/India) were sequenced by using the overlapping primers. Both the sequences showed close homology with DL35/JSRV/Sheep/India and the exJSRV circulating in the USA and China. Phylogenetic analysis of the 4 MVV sequences generated showed close homology with sequences reported from India and United Kingdom. Histopathology of 341 tissue samples (219 lungs, 52 lymph node, 29 brain and 41 mammary gland) was done. In lung tissues interstitial pneumonia (31.5%) was most frequent type of pneumonia followed by bronchopneumonia (26%), maedi (5.47%), OPA (3.65%), pulmonary cyst (0.46%). Other miscellaneous lung lesions include emphysema and atelectasis (13.6%), pulmonary haemorrhage and congestion (13.6%), and pulmonary oedema (5.47%). Lymph node sections showed lymphoid depletion (44.2%), reactive lymph nodes (26.9%) and congestion (11.53%). In mammary glands, atrophy with fibrosis was observed in 36.5% cases, followed by mastitis (24.3%), fatty change (7.3%), hypertrophy (7.3%) and lipoma (4.8%). Brain tissue showed congestion (31.03%), hypercellularity (24.13%) and peri-neuronal satellitosis (13.7%). IHC revealed that JSRV CA localized in the cytoplasm of the proliferated pneumocytes, bronchiolar epithelium and macrophages of OPA affected lungs. MVV p28 immunostaining was observed in the cytoplasm of MNCs, particularly in the macrophages of lungs and lymph node. IHC for immune cells revealed that CD8 T lymphocytes and B cells were predominant type of immune cells present in the lungs affected with OPA and maedi. MHC II expression was shown by the macrophages and fibroblasts, and comparatively higher in OPA cases than maedi. Expression of cytokine gene (IFN-γ, TNFα, IL2, IL4, IL6, IL10) was down regulated in both OPA and maedi. Up regulation of cytokines gene was seen in few cases and among them upregulation was comparatively higher in maedi cases than OPA. In conclusion, JSRV and MVV are prevalent in the small ruminant population of northern India which need to study systematically so that its economic impact can be evaluated. CD8 T cells and B cells are more prominent in OPA and maedi cases and the ecpression of inflammatory cytokines genes is downregulated in most of cases. A controlled experimental study is needed.to know its pathogenesis and immunopathological behavior.