Estimating foot‐and‐mouth disease (FMD) prevalence in central Myanmar: Comparison of village headman and farmer disease reports with serological findings

Abstract

The impacts of foot‐and‐mouth disease (FMD) on food security in developing countries are difficult to quantify due to the scarcity of accurate data on the prevalence and incidence of affected villages. This is partly due to resource constraints as well as the logistical challenges of conducting regular diagnostic testing in remote locations. In this study, we used descriptive analysis and latent class analysis (LCA) models to analyse data collected during a field survey of 160 villages in central Myanmar in the Mandalay and Sagaing Regions over the 2012–2016 time period. We evaluated the performance of verbal reports made by village householders and headmen against serological data to retrospectively determine the FMD‐infection status of our study area and to identify factors contributing to under‐reporting. Blood samples were collected from approximately 30 cattle per village in both the 6‐ to 18‐month age range and over 18‐month age range to distinguish between recent and historic exposure. Village householders were asked to identify pictures of FMD‐affected cattle amongst pictures of cattle affected with other common endemic diseases to assess the accuracy of their verbal reporting. The serological results confirmed that FMD is endemic in central Myanmar with village‐level seroprevalence estimated at 56% for animals 6–18 months of age and 80% when all age groups were considered together. Most village householders were familiar with the clinical signs of FMD‐affected cattle (72%). Based on the results from the LCA models, the village headman had a sensitivity of 77% and specificity of 75% for identifying FMD outbreaks in their village, whereas individual householders had a higher sensitivity and lower specificity of 80% and 56%, respectively. The level of disagreement between the different sources was correlated with the total number of cattle in the village and may potentially be worse in villages where endemic FMD may have led to a high level of natural immunity in cattle and subsequent masking of clinical signs. However, other regional effects such as the intensity of FMD extension efforts cannot be ruled out. Overall, the results suggest that verbal reports of FMD outbreaks from village headmen may be a useful tool to integrate into active FMD surveillance programmes in developing countries.

Detection of Foot-and-Mouth Disease Virus in the Absence of Clinical Disease in Cattle and Buffalo in South East Asia

“…The results were similar for both Laos and Myanmar, suggesting this might be a pattern which is common throughout the region. This is supported by data from Myanmar showing that clinical FMD occurred less frequently than exposure and seroconversion (5). The FMDV 3D RT-qPCR has a diagnostic specificity of close to 100% (31) and a diagnostic sensitivity (DSe) of 97.7% (32), therefore low rates of false positivity may occur.…”

“…Previous studies undertaken in these countries as part of the PCP-FMD demonstrated widespread exposure of cattle, with up to 56% of villages in central Myanmar demonstrating serological evidence of FMDV exposure (5), 51% of large ruminants at a Laos slaughterhouse testing positive on serology (20) and the circulation of multiple strains of FMDV (types O, A, and Asia 1) (23,24). Seropositivity is greater than predicted by either formal outbreak reporting (25) or village headman observations (5). This suggests that research is needed to better define the role played by subclinical animals in FMDV transmission in Myanmar and other FMDV-endemic countries with similar husbandry and ecological conditions.…”

“…Parameters of acute FMD infection in naïve cattle are welldefined, and continue to be refined by research (3,4). In contrast, the subclinical cycles of FMD in the approximately 128 countries where the virus circulates are less-well documented, and the characteristic, "fulminant" herd-wide disease may be observed or reported inconsistently in endemic regions compared to what is documented in epidemic contexts (5,6). Almost 50 years ago, Anderson et al (7) wrote that "the occurrence of clinical outbreaks does not necessarily give a true assessment of the amount of virus in the environment as subclinical or in apparent infection could occur, particularly in partially immune cattle."…”

What drives small-scale farmers to vaccinate their multiple livestock species animals against common infectious diseases in Myanmar?

“…Even though the vaccine with high efficacy is available, the different types of strains (i.e. serotype Asia 1, O/ME-SA/Ind-2001d, and O/SEA/Mya-98) could be challenging for disease control and which may further need for vaccine matching with local strain [ 17 – 19 , 22 , 23 ]. The most prevalent FMDV strains are serotype O and A whereas serotype Asia 1 was newly detected in Myanmar in 2005 which could not be clearly explained by the source of origin; and since the dynamic of disease transmission is so complicated, vaccine matching is another challenging for disease control by vaccination for low-income country with limited resource like Myanmar [ 16 , 22 , 24 – 27 ].…”

“…serotype Asia 1, O/ME-SA/Ind-2001d, and O/SEA/Mya-98) could be challenging for disease control and which may further need for vaccine matching with local strain [ 17 – 19 , 22 , 23 ]. The most prevalent FMDV strains are serotype O and A whereas serotype Asia 1 was newly detected in Myanmar in 2005 which could not be clearly explained by the source of origin; and since the dynamic of disease transmission is so complicated, vaccine matching is another challenging for disease control by vaccination for low-income country with limited resource like Myanmar [ 16 , 22 , 24 – 27 ]. Due to the awareness, limited resources and vaccination practice especially in rural areas where the majority of traditional backyard farming is implemented, FMD has been still threatening the livestock production especially in developing countries [ 28 , 29 ].…”