Regional transmission dynamics
As PPR is an acute and highly contagious viral disease of small ruminants, the inter-territorial and transboundary transmission of PPRV in healthy animals is matter of dire attention. Transmission PPRV in healthy animals occurred by direct contact with infected animal and contaminated materials i.e. oculonasal and oral discharges, the loose faeces, hold large amount of the virus. Small infective droplets release into the air from these secretions and excretions, especially when affected animals cough or sneeze (Abubakar et al., 2011; Abubakar et al., 2012; Bundza et al., 1988, Taylor, 1984). Likewise, transboundary animal’s movement plays a key role in transmission because some neighbor’s countries have free animal movements, purchases system, nomadic system, infected migratory animals etc. These nutritional deficiencies which lead to poor immunity of animal might be a cause of rapid transmission of PPRV which results in heavy outbreaks in endemic situation.
The spread of PPR is considered to be a result of transboundary movement of small ruminants (Dhar et al., 2002; Kumar et al., 2014; Liu et al., 2018), with the rapid trading of small ruminants also contributing to the propagation of outbreaks (Balamurugan, Das et al., 2014). All holder farmers affected economically so importance of PPR is increasing in Laos region (Burns et al., 2018; Windsor et al., 2017). Although the goat industry in Laos is the smallest livestock sector, recent increase of mutton prices in China and Vietnam have spiked a “goat boom” in SE Asia, leading industry professionals to estimate that the Lao goat population has more than doubled since the 2011 agricultural census (Burns et al., 2018; Windsor et al., 2017). In that census, 6% of households raised goats (Anonymous, 2012). There are minimal data on the occurrence of PPR in Southeast Asia. China has experienced two major outbreaks of PPR in the last decade, although it was previously free from the disease. The first outbreak occurred in Tibet in 2007. This outbreak was likely caused by importation of goats from neighboring India, Pakistan, and Tajikstan, resulting in the loss of 30.8% of the local population of small ruminants (Bao et al., 2011; Liu et al., 2018). Stamping out of suspected infected herds, delivery of effective vaccination programs, and implementation of nationwide surveillance strategies, led to eradication of PPR in China by 2010 (Liu et al., 2018). The second outbreak occurred in Xienjiang in 2013‐14. This outbreak spread to 32 other counties, including an outbreak in Yunnan on the northern Lao border, a thoroughfare for trade between the Association of Southeast Asian Nations (ASEAN) countries (Li et al., 2017; Liu et al., 2018; Wu et al., 2016). PPR lineage studies suggest this outbreak was likely due to transboundary movement of animals into China rather than a re‐emergence of the disease from Chinese herds (Wu et al., 2016). Prior to these outbreaks in China, PPR antibodies were discovered in apparently healthy mountainous goats in northern Vietnam, yet any attempts to identify the virus and other investigations have not been reported (Maillard et al., 2008). To date, there have been no reports of PPR outbreaks in Laos. However, the occurrence of similar endemic diseases and poor veterinary infrastructure may lead to PPR being missed or underdiagnosed. Differential diagnoses for PPR in Laos may include foot and mouth disease virus (FMD) (Nampanya et al., 2013), ovine parapoxvirus induced Contagious Ecthyma (Windsor et al., 2017), Coxiellosis (Burns et al., 2018), Brucellosis (Burns et al., 2018) and intestinal parasites (Windsor et al., 2018). Laos is considered as being “at risk” of PPRV incursion due to: proximity and trade with PPR-endemic China; it is a landlocked country with “porous” borders enabling livestock trade between ASEAN countries; and the relatively poor veterinary infrastructure with suboptimal capacity to detect and respond to emergency and/or emerging disease outbreaks (Bastiaensen, Kamakawa, & Varas, 2011; Nampanya et al., 2013). PPR is an eminent disease and eradication needs to be prioritized for poverty alleviation and food security, because of the high morbidity and mortality in small ruminants commonly owned by resource-constrained farmers. However, to further support disease control policies, there is need for further research on several epidemiological features, such as transmission dynamics among known and/or novel hosts raised either under similar or different production systems (Jost et al. 2007). In addressing the risk of PPR to regional aspect to protect the livelihoods of small ruminant smallholder farmers from losses, it is important to investigate the regional epidemiology of PPR.