Peste des petits ruminants (PPR) is an emerging, economically important viral disease of goats and sheep in the Indian subcontinent. In the present investigation, 15 hill goats were experimentally infected with 2 ml of 10% splenic suspension of a virulent isolate of PPR virus (PPR/Izatnagar/94) that had caused heavy mortality (>75%) in goats during 1994 outbreaks in northern India. More than 86% (13 of 15) animals died between 9 and 13 days post inoculation at the height of temperature or when temperatures were declining. Necropsy findings included congestion of gastrointestinal tract (GIT), nasal sinuses, consolidation of antero-ventral lobes of lungs, engorged spleen, and occasionally oedematous lymph nodes. Histopathological examination of major organs of GIT revealed degeneration and necrosis of labial mucosa, severe mucosal and submucosal congestion, degeneration and necrosis of intestinal epithelium and lymphoid cell depletion from Peyer's patches along with presence of syncytia at times. Lungs showed broncho-interstitial changes and presence of intracytoplasmic and intranuclear eosinophilic inclusions in alveolar macrophages and syncytial cells. These changes in lungs were frequently complicated with serofibrinous pneumonia (57%, eight of 14). Lymphocytolysis and occasional syncytia formation were evident in the lymphoid tissues. Immunohistochemical (IHC) findings included presence of PPR virus antigen in the labial, intestinal, and bronchiolar epithelial cells, pneumocytes, macrophages and syncytial cells in lungs, and lymphoid (intact and necrotic) and reticular cells in lymphoid organs. The findings of the study indicated the highly virulent nature of the PPR virus isolate (PPR/Izatnagar/94), causing 100% mortality and characteristic pathological changes in the target organs such as lungs, intestines and lymphoid tissues. The results of the IHC study suggested that indirect immunoperoxidase could be an alternative method in the absence of more sophisticated methods of laboratory diagnosis of PPR virus infection in goats.

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A single-tube one-step multiplex RT-PCR was standardized to amplify both 337 bp and 191 bp fragments of N and M genes of peste des petits ruminants virus (PPRV), respectively, and only a 337 bp fragment of N gene of Rinderpest virus (RPV). The RT-PCR using purified viral RNA was easily adopted for direct detection of PPRV in clinical field samples and its differentiation from RPV. The amplified N and M gene products were confirmed to be PPRV- and RPV-specific by their size in 1.5% agarose gel and restriction analysis. In the assay, the Qiagen one-step RT-PCR kit containing the Ominiscript and Sensiscript reverse transcriptases and Hot star Taq DNA polymerase was utilized. The sensitivity of the assay was found to be 100 fg of PPRV RNA. Compared with a two-step assay, the one-step assay is easier and time-saving as it requires just a single buffer for both reactions, reverse transcription (RT) and PCR. In experimentally infected goats, PPRV was detectable by the one-step RT-PCR in nasal and ocular swabs 7-17 days post infection (p.i.). and in oral swabs 7-15 days p.i. Out of 32 clinical field samples tested, 18 were positive by sandwich ELISA (S-ELISA), while 22 were positive by the one-step RT-PCR.

Bluetongue (BT) is a noncontagious and arboviral disease of both domestic and wild ruminants. The disease is enzootic in areas where reservoirs (cattle and wild ruminants) and vectors exist for the BT virus (BTV). A total of 24 BTV serotypes have been recognized worldwide. The major control measures include restriction of animal movement, vector control applying insecticides, slaughter of infected animals and vaccination. Prophylactic immunization of sheep against BT is the most practical and effective control measure to combat BT infection. At present, attenuated vaccines are used in the Republic of South Africa, the USA and other countries. However, EU countries were using attenuated vaccines, only recently shifting to inactivated vaccines owing to their safety and efficacy. In India, inactivated vaccines are in experimental stages and are expected to be on the market shortly. Inactivated vaccines generate serotype-specific long-lasting protective immunity after two injections, and may help in controlling epidemics. Differentiating infected from vaccinated animals (DIVA) is theoretically possible with inactivated vaccines but has not yet been developed, whereas the attenuated live vaccines are not candidates for DIVA. Attenuated live vaccines are efficacious but safety issues are of great concern. New-generation vaccines (subunit, virus-like particles, core-like particles and vectored) can be employed for DIVA. Recombinant vaccines, which generate cross-protection against multiple BTV serotypes, have great potential in BT vaccine regimens. Furthermore, new-generation vaccines are safe and efficacious experimentally, but large-scale field trials are warranted. Alternative areas, such as antivirals, siRNA, interferon and nanotechnology, may be of future use in the control of BT. We give an overview of BT vaccines, starting from conventional to recent developments, and their feasibility in controlling BT infection.

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