Foot-and-mouth disease seroprevalence and reporting behaviours in nine northern provinces in Lao PDR: The current situation and challenges for control

A scoping review of foot-and-mouth disease risk, based on spatial and spatio-temporal analysis of outbreaks in endemic settings

Foot-and-mouth disease (FMD) is one of the most important transboundary animal diseases affecting livestock and wildlife species worldwide. Sustained viral circulation, as evidenced by serological surveys and the recurrence of outbreaks, suggests endemic transmission cycles in some parts of Africa, Asia and the Middle East. This is the result of a complex process in which multiple serotypes, multi-host interactions and numerous socio-epidemiological factors converge to facilitate disease introduction, survival and spread. Spatial and spatio-temporal analyses have been increasingly used to explore the burden of the disease by identifying high-risk areas, analysing temporal trends and exploring the factors that contribute to the outbreaks. We systematically retrieved spatial and spatial-temporal studies on FMD outbreaks to summarize variations on their methodological approaches and identify the epidemiological factors associated with the outbreaks in endemic contexts. Fifty-one studies were included in the final review. A high proportion of papers described and visualized the outbreaks (72.5%) and 49.0% used one or more approaches to study their spatial, temporal and spatio-temporal aggregation. The epidemiological aspects commonly linked to FMD risk are broadly categorizable into themes such as (a) animal demographics and interactions, (b) spatial accessibility, (c) trade, (d) socio-economic and (e) environmental factors. The consistency of these themes across studies underlines the different pathways in which the virus is sustained in endemic areas, with the potential to exploit them to design tailored evidence based-control programmes for the local needs. There was limited data linking the socio-economics of communities and modelled FMD outbreaks, leaving a gap in the current knowledge. A thorough analysis of FMD outbreaks requires a systemic view as multiple epidemiological factors contribute to viral circulation and may improve the accuracy of disease mapping. Future studies should explore the links between socio-economic and epidemiological factors as a foundation for translating the identified opportunities into interventions to improve the outcomes of FMD surveillance and control initiatives in endemic contexts.

Abattoir-Based Serological Surveillance and Spatial Risk Analysis of Foot-and-Mouth Disease, Brucellosis, and Q Fever in Lao PDR Large Ruminants

A national animal disease surveillance network initiated by the Lao PDR government is adopted and reinforced by a joint research project between the National Animal Health Laboratory (NAHL), the Department of Livestock and Fisheries (DLF), and the Mahidol Oxford Tropical Medicine Research Unit (MORU). The network is strengthened by staff training and practical exercises and is utilised to provide zoonotic or high-impact disease information on a national scale. Between January and December 2020, large ruminant samples are collected monthly from 18 abattoirs, one in each province, by provincial and district agriculture and forestry officers. The surveillance network collected a total of 4247 serum samples (1316 buffaloes and 2931 cattle) over this period. Samples are tested for antibodies against Brucella spp., Coxiella burnetii (Q fever) and Foot-and-Mouth Disease Non-Structural Protein (FMD NSP) using commercial ELISA kits and the Rose Bengal test. Seroprevalences of Q fever and brucellosis in large ruminants are low at 1.7% (95% CI: 1.3, 2.1) and 0.7% (95% CI: 0.5, 1.0) respectively, while for FMD NSP it is 50.5% (95% CI: 49.0, 52.0). Univariate analyses show differences in seroprevalences of Q fever between destination (abattoir) province (p-value = 0.005), province of origin (p-value = 0.005), animal type (buffalo or cattle) (p-value = 0.0008), and collection month (p-value = 3.4 × 10−6). Similar to Q fever, seroprevalences of brucellosis were significantly different for destination province (p-value < 0.00001), province of origin (p-value < 0.00001), animal type (p-value = 9.9 × 10−5) and collection month (p-value < 0.00001), plus body condition score (p-value = 0.003), and age (p-value = 0.007). Additionally, risk factors of the FMD NSP dataset include the destination province (p-value < 0.00001), province of origin (p-value < 0.00001), sex (p-value = 7.97 × 10−8), age (p-value = 0.009), collection date (p-value < 0.00001), and collection month (p-value < 0.00001). Spatial analyses revealed that there is no spatial correlation of FMD NSP seropositive animals. High-risk areas for Q fever and brucellosis are identified by spatial analyses. Further investigation of the higher risk areas would provide a better epidemiological understanding of both diseases in Lao PDR. In conclusion, the abattoir serological survey provides useful information about disease exposure and potential risk factors. The network is a good base for field and laboratory staff training in practical technical skills. However, the sustainability of such a surveillance activity is relatively low without an external source of funding, given the operational costs and insufficient government budget. The cost-effectiveness of the abattoir survey could be increased by targeting hotspot areas, reducing fixed costs, and extending the focus to cover more diseases.

Socioeconomic impacts of clinical foot-and-mouth disease and a risk-based partial vaccination campaign for smallholders in Lao People's Democratic Republic

Foot-and-mouth disease (FMD) is endemic in Lao People's Democratic Republic (PDR). A risk-based partial vaccination campaign was implemented in Champasak, Savannakhet and Xiengkhouang Provinces in Lao PDR in 2016-20, which had limited effects on reducing the circulation of FMD virus. The objectives of this study were to measure the socioeconomic effects of (i) a clinical FMD occurrence and (ii) the vaccination campaign on livestock production performance of smallholders in Lao PDR in 2016-2020. Two questionnaire surveys were conducted at the beginning (2016) and the end (2020) of the campaign, involving 1,609 smallholders in 160 villages comparing areas with and without FMD control. Mixed-effect multivariable regression models were fitted to measure the association between livestock production parameters at the household level (rates of birth, sale, purchase, and death, sale price, costs, gross gains and net gains) and (i) a clinical FMD occurrence and (ii) the vaccination campaign, while adjusting for village, herd size, province, vaccination status and FMD knowledge. We found no significant difference in annual household-level costs, gains and net gains by due absence of FMD. However, smallholders with FMD had a 52% higher cattle death rate, a 43% lower goat sale rate and a 78% lower pig sale price than those without FMD. Smallholders with FMD also had a lower purchase rate of livestock (cattle -15% and pigs -93%) compared with those without FMD. There was a general improvement in livestock production in target villages over the five years of the vaccination campaign, whereas there was an overall decline in non-target villages, resulting in USD 218 higher net gains in target villages in 2020 compared with non-target villages, possibly due to reduced severity of disease and improved awareness on FMD and general livestock health. The findings of this study will help improve strategies for sustainable and efficient FMD control in Lao PDR, while the challenges and importance of gaining participation by smallholders are highlighted. This article is protected by copyright. All rights reserved.

Livestock movement patterns in the main livestock production provinces of Lao PDR

Foot-and-mouth disease (FMD) is a highly infectious transboundary disease that is endemic and affects the livelihood of smallholder farmers in Lao People's Democratic Republic (PDR). Knowledge about livestock movement patterns is important for preventing the spread of FMD between villages. This study describes the livestock movement patterns in Champasak, Savannakhet and Xiangkhouang provinces of Lao PDR. Face-to-face interviews were conducted with randomly selected villagers (n = 195) and traders (n = 169) in 115 villages between February and March 2019. Livestock owners commonly purchased (mainly breeding) animals from other smallholders (81%) and sold (mainly slaughter) animals to traders (76%) or other smallholders (16%), typically within the same district and province. The median inter-village trade distance was 20-30 km, with an average frequency of 4 trades per village per month. Traders purchased animals from smallholders (71%) and middlemen (25%) located within their district. It was common for many traders (74%) to retain animals at their property before selling, typically a median of 4 beef cattle per trader. Local trades within the district were far more common (72%) than distant trades. The movements of grazing/fattening large ruminants between villages were reported in 30% of the villages in all three provinces and occurred mostly within the same district or province in short distance (6 km). Social Network Analysis has identified animal movement hubs in the three provinces which could be targeted for FMD control and surveillance. Movements of animals for further use (fattening/ reproduction), long-distance movements and frequent local movements described in this area have important implications for FMD circulation. The findings from the study will inform FMD spread simulation models for Lao PDR. The knowledge gained from these data will also help the Lao PDR authorities understand the patterns of animal movements associated with disease spread.

Impact of risk-based partial vaccination on clinical incidence and seroprevalence of foot and mouth disease in Lao PDR

Foot and mouth disease (FMD) is endemic in the Lao People's Democratic Republic (PDR) and it causes economic loss to smallholder husbandry systems. An intervention programme based on a risk-based partial vaccination strategy was implemented in three provinces of Lao PDR (Champasak, Savannakhet and Xiangkhouang) to immunise domestic cattle and buffalo during 2016-2020. Two cross-sectional surveys were conducted in 2016/17 and 2020 to evaluate the impact of the vaccination programme on the prevalence of FMD virus exposure and clinical incidence of the disease. A total of 212 villages were visited during the two surveys, collecting 1609 household-level questionnaire results and 5931 blood samples of domestic cattle and buffalo. Blood samples were tested for the presence of antibodies to the non-structural proteins of FMD virus, and seroprevalence of 42.5 and 47.5% in 2016/17 and 2020, respectively were found. Multivariable regression analysis indicated that the efficacy of the FMD vaccination programme for reducing FMD virus circulation varied by province. In general, the incidence of clinical FMD increased toward the end of the 5-year intervention period, coinciding with a reduction of vaccine coverage in the last 2 years of the period. The findings suggest that the risk-based vaccination strategy achieved a marginally protective effect against the circulation of FMD virus with the possible limiting factors being operational constraints of public veterinary services, lack of farmers' compliance and unsustainable funding. We conclude that consistent resource availability and higher vaccination coverage is required to successfully control FMD with a risk-based vaccination strategy in Lao PDR.