Foot and Mouth Disease (FMD) is a high-impact, contagious transboundary animal disease that is endemic in Southeast Asia. Abattoir samples were routinely collected in six selected provinces between March and December 2019. A total of 1280 samples of abattoir animals were tested for FMD Non-Structural Protein (NSP) antibodies to indicate natural infections. Overall, 22.8% were seropositive for FMD NSP antibodies while seroprevalence of cattle (n = 469), buffalo (n = 214), and pigs (n = 597) were 44.6%, 35.0%, and 1.3%, respectively. The highest seroprevalence destination province was Xiengkhouang (35.3% of 272 samples), followed by Savannakhet (27.0% of 244 samples). Risk factors for evidence of natural infection identified by a multivariate logistic regression model included age groups (p-value = 0.02) and origin provinces (p-value = 2.8 × 10−5) of the animals. There were significant differences of FMD NSP seroprevalence between age groups and origin provinces of the animals. The odds ratio of a seropositive result in the less than 1 year old group was 2.5 (95% CI; 1.4, 4.4) when compared to the 3–4 years old group, while the odds ratios for animals that originated from Khammouane and Xiengkhouang provinces were 4.5 (95% CI; 1.1, 18.7) and 2.4 (95% CI; 1.4, 4.1), respectively, when compared to Champasak province. Serotype-specific antibody ELISA for 44 NSP antibody–positive samples revealed evidence of FMD serotypes O and A virus circulation in some provinces. Despite the passive abattoir survey providing useful information on FMD virus previous exposure and geographic locations of the animals, timely information on FMD virus circulation and distribution is also crucial to an effective control program. Alternative approaches to increase the cost-effectiveness of the surveillance network are also discussed.

The heat resistance of foot-and-mouth disease virus (FMDV) strains isolated from outbreaks inFoot-and-mouth disease virus (FMDV) is classified within the genus Aphthovirus, family Picornaviridae. FMDV is a nonenveloped, icosahedral symmetric, and single-stranded RNA virus; therefore, it is somewhat resistant to harsh environments, e.g., UV radiation, low water activities, and heat (3). FMDV causes foot-and-mouth disease (FMD) and is highly contagious to cloven-hoofed animals. The common mode of transmission of FMDV is direct contact; however, oral-route transmission via indirect contact has frequently caused epidemics in pigs (2). FMD is the first disease on the OIE List A and also was the first disease for which the OIE established an official list of free countries and zones. FMD has a great potential for causing severe economic loss for many countries (2). In order to export meat from an FMD-infected country to an FMD-free country, meat is subjected to heat treatment to reach an internal core temperature of at least 70°C for a minimum of 30 min or to any equivalent treatment which has been demonstrated to inactivate the FMD virus (38).The efficiency of thermal inactivation is a function of time and temperature. Thermal destruction hypothetically follows first order kinetics. The decimal reduction time (D value, DRT, or D T ) is the time at a specified temperature required to reduce the number of microorganisms by a factor of 10 (23, 24, 44, 45). The D value is the negative reciprocal of the slope of the inactivation curve, where the inactivation of microorganisms is a logarithmic function of time. The z value is defined as the temperature change required to reduce D value by a factor of 10 (23, 24, 44, 45). Likewise, the z value can be calculated by the negative reciprocal of the slope of the decimal reduction curve where D values of different temperatures are plotted on a semilogarithmic scale against temperatures. The z value is specific for a given strain of microorganism in a given medium or product, but the z value does not differ across media as widely as does the D value. This association of D value and temperature in a DRT curve is helpful to calculate the D value of temperatures that were not included in the experiment. Many studies have demonstrated the heat resistance of FMDV (10, 12, 14-16, 30-32, 34). However, these studies involved only a few temperatures, different media, and strains that were not epidemic in Thailand. Therefore, these data are not appropriate bases for bilateral trade negotiations involving Thai animal products. The objective of the present study was to determine the heat resistance of FMDV strains isolated from outbreaks in Thailand, in terms of D value and z value in phosphate-buffered saline (PBS) at 50, 60, 70, 80, 90, and 100°C. MATERIALS AND METHODSVirus and cell culture. FMDV serotypes O (strains O189 and OPN), A (strains A118, A-Sakol, and A132), and Asia 1 (strain AS1) were obtained from the Regional Reference Laboratory for FMD in Southeast Asia, Pakchong, Thailand....

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