A Report on Massive Outbreaks of FMD with Concurrent Mannhaemia hemolytica Infection among Cattle in Tamil Nadu

Back ground: India has a huge resource of livestock and stands first globally in milk production, but reemergence of diseases like foot and mouth disease (FMD) causes a great concern and economic losses to the farmers. Three serotypes of FMD virus (O, A and Asia 1) are prevalent and serotype O was responsible for 80 per cent of confirmed outbreaks /cases in India. The highest incidence of the disease was seen in Southern region (31.5%) and during the month of September. Highest number of outbreaks (201) occurred in Tamil Nadu in the year 2007-08 caused by serotype O virus. FMD causes very high morbidity and mortality rate among young animals and the mortality rate is generally low in adult animals and seen with manifestation of infection limited to epithelial sites. However, In the present study an unusually high mortality among adult cattle due to FMD, complicated with Mannheimia hemolytica infection with specific myocardial lesions were discussed in several outbreaks of FMD in the state of Tamil Nadu, India.
Methods: Outbreaks of FMD occurred in various districts of Tamil Nadu during the period of October to December in the year 2013 causing large scale mortality among adult cross bred (Jersey cross and Holstein Friesian cross) cows, heifers and calves and detailed disease investigations were carried out .Samples were collected from ailing animals and dead animals for laboratory confirmation of the disease. The collected samples were subjected to isolation of bacteria, serology and molecular confirmation of the virus.
Result: Affected animals showed characteristic lesions of FMD with multiple, focal to coalescing ulcers and erosions covered with shreds of epithelium and fibrin on the dorsum and lateral margins of the tongue, dental pad, hard palate, mucosa of lips and gums. Samples of vesicular fluid, oral and tongue epithelium and heart confirmed the presence of FMD type ‘O’ virus based on sandwich ELISA and multiplex PCR. Cultural examination of bacteriological samples revealed presence of Mannheimia hemolytica which was further confirmed by multiplex PCR. Out of 83 serum sample collected, 45 sera were positive for FMD by LPB ELISA, while 32 serum samples were positive for FMD by DIVA test. The sudden deaths among adult cattle and heifers during the FMD outbreak might be attributed to the severe myocarditis and the disease was controlled by following appropriate treatment and preventive measures.