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.