Seroprevalence of Crimean-Congo haemorrhagic fever in Indian cattle and buffaloes.

BACKGROUND & OBJECTIVES: Crimean-Congo hemorrhagic fever (CCHF) is an emerging tick-borne viral zoonotic disease of public health importance. Cattle and buffaloes although not showing any clinical symptoms, can be infected by the CCHF virus and act as sources of infection to human beings. The prevalence of CCHF in cattle and buffaloes is important from One health perspective for control of CCHF in humans. METHODS: A cross-sectional study was undertaken to ascertain the prevalence of CCHFV in cattle and buffaloes of India. MATERIALS AND METHODS: A total of 804 serum samples from four states of India (Gujarat and Rajasthan: human outbreaks reported; Punjab and Haryana: no outbreak reported) were screened by ELISA test detecting nucleoprotein antibodies of CCHFV. RESULTS: The overall true prevalence was 8.63% (95% CI: 6.76% - 10.9%). The highest prevalence was recorded in Rajasthan (13.24%) followed by Gujarat (8.68%), Haryana (6.84%), and Punjab (6.51%). Prevalence of CCHF was higher in cattle (9.92%) than buffaloes (5.84%); in females (10.87%) than males (4.99%); in adults (10.18%) than young ones (5.66%). Interestingly, higher seropositivity was recorded in indigenous cattle (12.04%) than in exotic and cross-breed cattle (1.69%) which was statistically significant (p=0.001). INTERPRETATION & CONCLUSION: These findings revealed CCHF virus is circulating unnoticed and the prevalence has increased over time which is of public health concern.

Virulence gene profiling and antibiotic resistance pattern of Indian isolates of Pasteurella multocida of small ruminant origin.

Pasteurellosis in small ruminants affects the livelihood of small and marginal farmers of India. The present study was undertaken to understand the trends in gene carriage and antibiotic resistance pattern of Pasteurella multocida isolates recovered from small ruminants over a period of 10 years in India. A total of 88 P. multocida isolates of small ruminant origin were subjected to virulence gene profiling for 19 genes by PCR and antibiogram study employing 17 different antibiotics. Virulence genes like exbB, exbD, tonB, oma87, sodA, sodC, nanB and plpB (100% prevalence) and ptfA and hsf-2 (>90% prevalence) were found to be uniformly distributed among isolates. Unexpectedly, a very high prevalence (95.45%) of pfhA gene was observed in the present study. Dermonecrotoxin gene (toxA) was observed in 48.9% of isolates with highest occurrence among serotype A isolates and interestingly, one of each isolate of serotype B and F were found to carry this gene. Antimicrobial susceptibility testing revealed 17.04% isolates to be multidrug resistant. Amongst all the antibiotics tested, most of the P. multocida isolates were found to be susceptible to enrofloxacin and chloramphenicol. This study highlights novel epidemiological information on frequency and occurrence of virulence genes among Indian isolates from small ruminants.

Antigenic site variation in foot-and-mouth disease virus serotype O grown under vaccinal serum antibodies in vitro.

Foot-and-mouth disease virus (FMDV) is constantly evolving under neutralizing antibody pressure in either naturally infected or vaccinated animals. This study was carried out to understand the dynamics of evolution of antigenic sites. Neutralizing antibody-resistant populations of three strains of FMDV serotype O (INDR2/1975, IND120/2002 and IND271/2001) were isolated by serial propagation in BHK-21 cells in the presence of sub-neutralizing level of bovine vaccinal sera (BVS). In the partial neutralization escape variants, fixation of aa substitutions were observed at critical residues of all established antigenic sites of serotype O {144 of VP1 (site 1), 45 and 48 of VP1 (site 3), 72 and 134 of VP2 (Site 2)} except site 4 and 5. In majority of the variant populations, site 3 was found to be substituted and therefore immunodominance may not be associated with a particular site, rather it appears to be a virus strain and infected host specific affair. Substitutions were also observed in proximity to the identified residues {41 and 51 (ßB-ßC loop), 133, 140 and 143 (ßG-ßH loop), 201, 204 and 209 (C terminus) of VP1, 71 and 75 (ßB-ßC loop), 131 (ßE-αB region), 174 and 179 (ßG-ßH loop) and 219 (C terminus) of VP3} within antigenic sites of serotype O or other serotypes which could be significant in terms of neutralizing antibody binding and immune escape. Presence of similar residues in the Indian field viruses as selected in the variants supports the importance of these sites in antigenic diversification of serotype O FMD virus.