Xa0054978 Prevalence of Antibody to Foot-And-Mouth Disease in Cattle and Buffalo in Myanmar
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XA0054978 PREVALENCE OF ANTIBODY TO FOOT-AND-MOUTH DISEASE IN CATTLE AND BUFFALO IN MYANMAR M. MAUNG KYIN Foot-and-mouth Disease Laboratory, Livestock Breeding & Veterinary Department, Ministry of Livestock & Fisheries, Insein, Yangon, Myanmar Abstract PREVALENCE OF ANTIBODY TO FOOT-AND-MOUTH DISEASE IN CATTLE AND BUFFALO IN MYANMAR A serological survey for the prevalence of antibody to foot-and-mouth disease (FMD) was performed in six Divisions and three States in Myanmar. A liquid phase blocking ELISA prepared and standardized by World Reference Laboratory (WRL) for FMD was used for this study. A total of 831 serum samples from cattle and buffalo were collected by a random process and assayed for antibody against FMD virus types O, A, C and Asia I. Positive reactions to FMD virus O, A, C, and Asia I sero-types were detected. Even in the free zone area, (Ngape township) and the buffer zone (Minbu township) serum samples showed positive reactions. Ten percent of the sera tested showed positive reactions to all sero-types within the free zone and buffer zone. The majority of cattle and buffaloes, except those in the FMD free and buffer zones, were not vaccinated against FMD. The percentage of positive sera in each State and Divisions varied from 16 to 90 for at least one sero-type. More epithelial specimens from FMD outbreaks should be submitted for investigation and further nation-wide serological surveys for FMD should be carried out if a national policy for FMD control and eradication is to be effective and enforceable. 1. INTRODUCTION Myanmar is primarily an agricultural country and is undertaking measures not only to produce more food for domestic consumption but also for export. Measures undertaken to enhance surplus of production include expansion of cropping areas, optimum utilization of land, increasing per acre yield and improving the quality of crops harvested. Plans have been adopted to put 16 million acres under monsoon and summer paddy with increased paddy output in the near future. The economy of Myanmar depends mainly on agriculture with 65% of the total working population engaged in this sector. Livestock form an integral part of rural economy and 85% of cultivation is carried out by animal draft power. Livestock ownership is distributed mainly among the smallholder farmers. hi 1998/99, cattle and buffalo population were recorded as 10.49 million and 2.33 million respectively. It is estimated that 55% of the total population of cattle and buffalo is used for draft power. Thus, draft animals are given high priority and are a major socio-economic component in the national agricultural scene. Clearly the income from animal production is an important factor in rural areas. According to the reports and epidemiological data, in Myanmar four important infectious diseases occur in cattle and buffalo. These are foot-and-mouth disease (FMD), Haemorrhagic Septicaemia (HS), Black leg and Anthrax. Among these, foot-and-mouth disease is the only major economic disease in Myanmar that has never been brought under systematic control. FMD has been known to occur in Myanmar since 1887. FMD is considered to be the most significant epizootic virus condition of livestock in Myanmar. The disease is highly prevalent in valuable livestock species especially cattle, buffalo and pigs. About 55% of the buffalo and cattle provide 85% of draft power in Myanmar. The incidence of FMD fluctuates throughout the year. The highest incidence of disease usually occurs during the onset of the monsoon season (May to August) and again at the end of the year (October to December). The first episode in any one year is usually observed as progressive outbreaks of FMD involving large numbers of animals through a series of villages. FMD outbreaks appear to coincide with crop plantation and harvesting. Hence the FMD virus is thought to be spread through the use of draught cattle and buffalo and/or the increase in trade of animals just prior to the monsoon season. The disease is often considered to be mild, of short duration, and of low mortality. However, importantly, a large number of animals are infected in any one outbreak. It is therefore difficult to estimate the total annual economic losses to Myanmar. It should be noted that FMD is the only major economic disease in Myanmar that has never been brought under systematic control. Among the seven States and seven Divisions in Myanmar, FMD outbreaks are 91 common in those areas where there is a large concentration of livestock, as found in the low-lying plains from the central part of Myanmar to the Delta coast. These regions include Yangon, Ayeyarwady, Bago, Magway, Mandalay, Sagaing Divisions and Mon State. An epidemiological investigation to evaluate the immune status of animals in these regions would be an essential precursor to an effective control and eradication programme for FMD. The immune status of the animals in this State and these Divisions would not only reveal valuable information as to the distribution of this disease in Myanmar but would form the basis for a FMD control and eradication strategy. 1.1. Background for FMD virus typing and serology in Myanmar Field staff of the Livestock Breeding and Veterinary Department routinely reacts promptly to FMD outbreaks and visit the area to assist in the control of the disease and its spread to surrounding areas. Notification, isolation, zoo-sanitary measures, and animal movement control are carried out in co-operation with the local authorities. Specimens from diseased animals were collected and submitted to the FMD laboratory, Yangon, for the identification of sero-types. Serum samples from convalescent animals were also sent for serological examination. Plan for surveillance of FMD and investigation of sero-types was commenced in 1977 through support provided under an FAO/UNDP Co-operation Project. This Project was first and foremost for FMD control in Myanmar. However, its longer term objectives were to promote the standard of disease control measures for FMD and hence to increase the healthy stock contributory towards the development on livestock products. The short-term objectives of the project focused on creating an ability to perform virus typing by serological techniques and to study the types of FMD virus in the country. It lasted three years starting from 1977/78 to 1979/80. The serological method used in differentiation of FMD virus was complement fixation test (CFT). According to the results obtained, three sero-types O, A and Asia I viruses were identified. This was carried out using specific anti-serum supplied by the Animal Virus Research Institute, Pirbright, UK and Plum Island Laboratory, USA. This was the first identification of FMD virus type A in the country. 1.2. Establishment of an ELISA unit for FMD In June 1995, Mr. N.P Ferris of the World Reference Laboratory (WRL), UK, visited Mynamar as an IAEA expert supported under a IAEA Technical Co-operation Project (MYA/5/007). He provided practical training in the ELISA both for FMD antigen and antibody detection. Following this further FMD virus typing and serology was carried out both under this Technical Co-operation Project and the FAO/IAEA Research Contract (8046/RB). ELISA kits for both FMD antigen and antibody detection as well as ELISA equipment including an ELISA reader linked to a computer system were supplied. As a result, the traditional method CFT was substituted with the more effective ELISA technology. The objectives of the studies reported in this paper were to determine the distribution and prevalence of antibody to FMD virus in cattle and buffalo in Myanmar and to advise on a national policy for the control and eradication of FMD in Myanmar. 2. MATERIALS AND METHODS 2.1. Sampling frame for survey A total of 816 serum samples from cattle and buffaloes were collected in 1997 from densely populated and FMD endemic areas in the State of Mon (10), in the Divisions of Bago (12), Ayeyarwady (2), Sagaing (5), Magway (13), Mandalay (14), and Yangon (1). Nineteen townships were chosen for this survey, based on previous knowledge of high risk areas for FMD. Fifty-eight samples were collected in 1998 from Shan State (7) and Rakhine State (3). Serum samples were collected by the of the FMD laboratory, Livestock Breeding and Veterinary Department (LBVD), Ministry of Livestock and Fisheries (MLF), except those from Shan and Rakhine States. The serum samples were collected randomly from 2 to 5 townships in each State or Divisions. 92 2.2. Sample collection and submission Blood samples were collected by vein puncture using 10 ml non-pyogenic disposable syringes disposable needles (0.80 x 38 mm 21G) and dispensed into sterile collection bottles. The decanted serum samples were collected in sterile Wheaton serum bottles. Each serum sample was kept in small amounts using 2 ml cryovials and stored at -20°C. The serum samples from Rakhine and Shan States were provided by the Diagnostic Laboratory, LBVD, Insein, Yangon, Myanmar. 2.3. Antibody detection Eight hundred and thirty-one serum samples were tested for antibody to FMD sero-types O, A, C and Asia I. Liquid phase blocking ELISA kits provided through the FAO/IAEA Research Contract under the Co-ordinated Research Project prepared and standardized by the WRL were used to assay all samples for FMD virus antibody [1-4]. Sera were assayed at a single dilution of 1:32 using the ELISA as a rapid, qualitative screening method. The assay procedures followed were those described in the IAEA/WRL Bench Protocol of July 1997 and September 1997. Sera were considered positive if one or more wells at the 1:32 dilution showed more than 50% inhibition as compared to the antigen control.