1 | INTRODUCTION
Foot-and-mouth disease (FMD) remains a worldwide major constraint to animal production and international trade. The causative agent, FMD virus (FMDV; genus Aphthovirus , family Picornaviridae ), exists as seven immunologically distinct serotypes (O, A, C, Asia 1, SAT 1, SAT 2 and SAT 3) and the virus is known to infect up to 70 cloven-hoofed animal species (Grubman and Baxt, 2004). The epidemiology of FMD in Africa is complex. This is partly because the continent is resident to three out of the seven endemic FMD virus pools (Pools 4, 5 and 6; Paton et al., 2009), and six out of the seven FMD virus serotypes have been recorded (Rweyemamu et al., 2008), although serotype C has not been detected since 2004 (Paton et al., 2021). Sudan is one of the largest African countries (nearly 1.9 million km2) which has a resident population of more than 100 million FMD-susceptible animals. It has 30-40 million cattle, 70 million small ruminants as well as a diverse range of FMD susceptible wildlife species that are located mostly in the Southern areas or in the Dinder National Park in Eastern Sudan (Anon, 2009). Sudan is recognised as an important crossroads between sub-Saharan and Northern Africa, and between East and West Africa.
FMD has been known to be present in Sudan since 1903 (Abu Elzein, 1983) and previous studies have highlighted the contribution of FMD circulation in the country to the wider epidemiology of the disease in Africa (Bronsvoort et al., 2004; Rweyemamu et al., 2008; Ularamu et al., 2017). In sub-Saharan African countries, FMD is endemic but clinical signs are often mild or inapparent particularly in sheep and goats and outbreaks are inconsistently reported to veterinary services. Together with the costs and logistics associated with the shipment of samples, these issues result in infrequent submissions to international reference centres [such as the World Reference Laboratory for FMD (WRLFMD), Pirbright, United Kingdom] and consequent potential for biases in epidemiological inferences (Bronsvoort et al., 2004). To address these sampling and reporting issues, the Government of Sudan together with the Food and Agriculture Organization of the United Nations (FAO) and the European Commission for the Control of FMD (EuFMD) joined efforts in a Technical Corporation Programme (TCP/SUD/3401) to promote active surveillance of FMD in Sudan which was undertaken between 2012 and 2014. This project analysed more than 1500 bovine sera and more than 1000 sera from small ruminants for antibodies against FMD virus (data reported elsewhere, Raouf et al., 2016; 2017). Furthermore, epithelium samples were collected during 2013-2018 from suspected disease events in six Sudanese states for virus detection, serotyping and molecular characterization. Four different FMDV serotypes have been reported to circulate in Sudan (O, A, SAT 1 and SAT 2) with SAT 1 last detected in 1976 (Habiela et al., 2010a). In previous reports, type O has been detected more frequently while serotypes SAT 2 and A are found more sporadically. The aim of this current study is to improve our understanding of the epidemiological patterns of FMD in Sudan and connections to neighbouring countries through characterising FMDV in clinical samples.