South Asia:
India: India has twenty-eight states and seven union territories. The country possesses about 200 million sheep and goats (Ministry of Agriculture, Government of India, 2009). PPR is endemic in India and is a major threat to about 200 million small ruminant population of the country (Dhar et al., 2002), causing an economic loss of about 1800 million Indian rupees annually (Bhadyopadhyay, 2002). Close contact is the most important way of transmitting the disease. It is suspected that the infectious materials can also contaminate water, feed troughs and bedding, turning them into additional sources of the infection. These are however short-term sources, since the PPRV, like its close relative the Rinderpest virus, would not be expected to survive for a long time outside the host (Diallo, 2003). In addition to these sources of infection movement of animals across the boundaries of states commonly acts as source of PPR epidemics. There is no known carrier state in PPR and the infected animal may transmit the disease itself during the stage of incubation period. However, the PPR infected animal’s seroconvert and become immune to PPR and RP viruses (Sudarshan et al., 1995). Singh et al. (2004) discussed the relation of migration of animals with that of maintenance and transmission of PPRV in nature. The close relations between PPR outbreaks and transportation of sheep and goats’ flocks have been reported (Boniwell, 1980; Dhand et al., 2002; Kataria et al., 2007; Shankar et al., 1998). Migration may also spread infection to cattle (Shaila et al., 1989).
In India, animal rearing is practiced in two major ways: one is unorganized back yard rearing (where 5–10 sheep or goats are reared in backyards and fed up on the agriculture byproduct) and the other is the traditional rearing of sheep and goats by nomadic communities (where the animals are fed on pasture lands and uncultivated or barren fields during the course of migration). Most of the earlier studies from India were conducted on sheep and goats of non-migratory flock (Singh et al., 1996, 2004; Kataria et al., 2007; Bhanuprakash et al., 2008) but the present study covered animals of both migratory and non-migratory flocks. According to Mahajan et al. (2012), the risk of PPR is higher in migratory flocks than in non-migratory flocks. The animals of these migratory flocks were brought from hilly areas through different routes after the completion of their seasonal migration to escape severe winters. This seasonal movement of animals may increase the chance of transmission among the migratory flocks. Moreover, in migratory flocks, there is transportation stress, underfeeding and underlying parasitic infection which may decrease the immunity, thereby increasing the susceptibility of animals to disease. These facts were also supported by the findings of other workers who reported outbreaks of PPR in migratory herds in Himachal Pradesh (Joshi et al., 1996) and Rajasthan (Singh et al., 1996). Similarly, Khan et al. (2007) reported higher sero-prevalence of PPR in southern and western parts of Punjab of Pakistan where nomadic rearing of sheep and goats was common.
The virus spreads through close contact via respiratory route. Viremia develops 2-3 days post infection. Fine infective droplets from the secretions and excretions of the infected animals are released into the air (Sen et al., 2010). Transmission could also occur through contaminated water, feed troughs and bedding (Lefèvre and Diallo, 1990). In India, animals are allowed to share common grazing land and water sources are risk factors. Besides, migration of animals between various states is common especially, in the sub-Himalayan region and western dry land areas such as Rajasthan and Gujarat (Nanda et al., 1996; Singh et al., 2004). Mixing of these migrated populations with local population may contribute to the disease transmission. Further, during the festival seasons, animals are shipped to various states for meat purposes. These unrestricted movements of animals contribute significantly to the epidemiology of the disease. In India, the disease occurs round the year and the maximum outbreaks reported during the winter and rainy seasons. Therefore, vaccination just takes place prior to the onset of rainy/ winter season. Initially, PPRV was classified in to 4 lineages I–IV based on the F gene sequencing (Dhar et al., 2002; Shaila et al., 1996); lineage I-III viruses were reported in several countries of Africa and lineage IV (Asian lineage) mainly in Middle East and Asia (Banyard et al., 2010; Dhar et al., 2002; Ozkul et al., 2002). Currently, N gene is preferred over F gene due to its better molecular separation (Kwiatek et al., 2007). In the recent past, many researchers report the presence of lineage IV in African countries (Maganga et al., 2013; Salami et al., 2014). Till now, only lineage IV viruses have been reported in India. The PPRV goat strain isolated during the recent outbreak at Tripura showed 99.2 to 99.6% nucleotide identities with the Bangladesh strains (Muthuchelvan et al., 2014). The overall epidemiological investigation confirms the transboundary transmission of PPRV with the neighboring countries including china, Mongolia, India, Pakistan, Bangladesh, Nepal and Afghanistan.
Pakistan: PPR was recognized in Pakistan in early 1990s but got importance during the Participatory Disease Surveillance (PDS) of Rinderpest Eradication Campaign. Lot of research work has been initiated during last decade towards disease epidemiology, risk factor recognition, laboratory diagnosis, vaccination and demonstration of control strategies (Abubakar et al., 2015). In Pakistan PPR is endemic, during the last decade, PPR outbreaks have increased to an alarming level involving newer areas (Ali, 2004). According to Zahur et al. (2011) PPRV is circulating in the small ruminant population throughout Pakistan. As, on the basis of clinical and serological methods, an outbreak of PPR was reported in goat flocks of Livestock Production and Research Institute (LPRI), Bahadurnagar, Okara, Pakistan (Khan et al., 2005). According to another report based on observations from 50 laboratory confirmed outbreaks of PPR and provides details of the presence or otherwise of PPRV in 427 tissue/organ samples from small ruminants in Pakistan. PPR is more severe in goats than sheep and the frequency of disease outbreaks are greater between the months of January to April. Spatial distribution of PPR in various locations of Pakistan indicate that the disease pattern, although both goats and sheep are susceptible to infection and may show disease yet they are not always affected simultaneously, for example, in Africa PPR is seen most commonly in goats, while in western and South Asia sheep are usually the most noticeable victims (FAO, 1999). But if we see the picture in Pakistan, PPR affect both goats and sheep but in many villages, it is seen that only goats are affected usually Taylor et al. (2005) and this concept is much supported by findings of Abubakar et al. (2008). In different districts of Sindh province, overall PPR seroprevalence in sheep is 49.5 % as compare to goats which is 56.3 %. According to (Obi et al., 1983; Durojaiye et al., 1983; Abubakar et al., 2011), most cases of PPR emerge with the start of summer season and cases get peak during the months of April to July and then the prevalence drop again that indicate the temporal pattern of disease Khan et al. (2008) reported the antibody prevalence of PPRV in small ruminants in Punjab 51.3 %. The antibodies frequency against PPRV recorded 67.7 %, 71.1 % and 60.2 % in the months of December, January and February and 50.7 % and 53.0 % in the months of September and October, respectively. Less local fodder availability and poor nutritional status of the animals may play a key role in the transmission of disease. Zahur et al. (2011) has reported distribution of PPRV in different districts of Pakistan that is over all 48.30 %. Jalees et al. (2013) investigated that disease is more prevalent in young sheep and goats than adult and predilection site of the PPRV remained the lymph nodes.
The true sero-prevalence of PPR in Pakistan estimated to be 48.5 % (95 % CI, 46.6–50.3), and 52.9 % (95 % CI, 50.7–55.1) and 37.7 (95 % CI, 34.4–41.0) for goats and sheep, respectively. The sheep and goats exhibited a different seroprevalence pattern with a quite higher prevalence in goats. The highest prevalence was recorded in animals over 2 years of age: 49.29 % of sheep and 65.94 % of goats were seropositive for PPR (Zahur et al., 2011).
In Pakistan different vaccination programs are introduce with the live attenuated virus belonging to Lineage I. Despite of the strict vaccination programs and other preventive and clinical measures the PPR outbreaks are frequent. Moreover, different type of PPR vaccines including conventional, thermostable, recombinant and edible vaccines has been developed and used from control/eradication of said disease world widely (Abubakar et al. 2011; Abubakar et al. 2012; Abubakar et al. 2015 and Odo, 2003).
Currently, vaccination is recommended in certain areas of the country. This vaccination is based on Nig75/1, which belong to lineage II, while field isolates from Pakistan are grouped in lineage IV. Genetic characterization of field strains will provide foundations for construction of vaccines from domestic strains as has recently been practiced in India (Anees et al., 2013). While, tissue culture based live freeze-dried PPRV (PPR 75–1) vaccine has been produced by Abbas et al. (2012) using Vero cell line and checked for validation, safety, sterility and efficacy. They concluded that this PPR vaccine would be an effective tool to limit PPR disease in goats as well as to reduce economic losses due to this disease in Pakistan. Currently, although the PPR vaccine production capacity is present in the two places in the country yet there is no organized PPR vaccination campaign going on. With the current population of more than 90 million of small ruminants and endemic situation of PPR, there is continuous threat from PPR in terms of food security.
International authorities working on animal health (OIE and FAO) have recognized PPR as the next target disease for control and possible eradication from the world. So there is need of the time to have national and regional PPR control program in the country and neighbors. After the successful Rinderpest eradication campaign, OIE has officially declared PPR as next candidate disease, to be eradicated. Therefore, serious efforts have been started towards the disease understanding and possible measures for its eradication.
Although there are some projects completed towards the progressive control of the disease in country yet there is need to understand the epidemiology of disease and to established a national level control and eradication program for PPR which will link with the regional control and eradication setup. Also there is need to have comprehensive social economic surveys, disease hot spot recognition and identification of role of other species like yolk, cattle, buffalo, camel and wildlife in disease transmission. With combined efforts of local and national authorities and political will, there is high likelihood that this devastating disease can be controlled and eventually eradicated in near future (Abubakar et al., 2015).
Bangladesh: In Bangladesh, PPR was first reported in goats in 1993 and since then it has become endemic in the country (Islam et al. 2001). Most of the previous PPR studies conducted in Bangladesh were based on either serology or clinical signs except a few recent publications with genetic characterization (Chowdhury et al. 2014; Rahman et al. 2016). Phylogenetically, the Bangladeshi PPRV strains belong to the PPRV lineage IV and formed a separate subgroup and these are closely related with China-Tibet/07 and Indian/TN/VEL/2015 PPRV isolate. The overall PPR sero-prevalence was 21% in 2008, ranging from 6% to 49% in different geographical locations/districts in Bangladesh (Bhuiyan, 2012). A study conducted in 2009–2010 on laboratory confirmed outbreaks of PPR in Black Bengal goats resulted in 75% and 59% flock morbidity and mortality, respectively, with a case fatality rate of 74% (Chowdhury et al. 2014). Approximately 84 000 veterinary clinical cases of PPR were recorded in 2010 in Bangladesh, but it might not represent the actual burden of the disease as they all were not laboratory confirmed and presumptive diagnosis by veterinarians only has a moderate predictive value (Chowdhury et al. 2014; Haider et al. 2016). Bangladesh Livestock Research Institute (BLRI) has developed a homologous cell culture attenuated PPR vaccine which is very potent against PPR (Anonymous, 1999). But vaccination program has not yet covered the total population of the country. So supportive therapy of atropine aided antibiotic, fluid therapy and antihistaminic aided antibiotic, fluid therapy as well as combined therapy can save the life of PPR affected patient in field condition (Chakrabarti, 2003). According to Parvez et al. (2014), reported prevalence of PPR in goats at Chittagong district, Bangladesh was 8.99. The prevalence regarding PPR among kid, young and adult goats were found to be 6.19% 11.72% and 7.52% respectively with the significant p value (P=0.000). Thus the reported prevalence of PPR was higher in young goats over the adults and kids agreed with the results of Islam et al., (2012), Sarker and Islam (2011), Rahman et al., (2011) and Singh et al., (2004. This research also revealed that, the highest prevalence of PPR was recorded in Black Bangle goats 10.11% in compare to Jamunapai goats 7.44% and other cross breed goats with significant p value (P=0.005). So that the Black Bangle goats were much more prone to PPR in compare to Jamunapari along with other cross breed goats similarity with the findings of Islam et al., (2012).Sarker and Islam (2011) and Mondal et al., (1995). They observed that Black Bangle goats were more susceptible to the PPR in compare to other goat breeds. Prevalence of PPR in goats due to seasonal variation revealed that highest prevalence had been seen in rainy season 11.30% in comparison to summer 6.40% as well as winter season 8.25% with significant p value (p=0.000). This variation might be due to different geographical region and study period. The highest prevalence of PPR at present study was observed in the month of August 13.75% and October 11.51% in contrast with the findings of Sarker and Islam (2011); Abubakar et al., (2009) who recorded highest prevalence in the month of December (31.68%) and January (30.34%); 32.57% in March and 19.43% in April respectively. Results revealed that the lowest occurrence was in May (4.09%) in contrary with this result Abubakar et al., (2009) and Sarker & Islam (2011) who reported lowest prevalence in the month of June, i.e., 1.71% and 9.52%, respectively. This variation might be due to different geographical location, research period, and different management practices. Bangladesh faces a little bad analogous issue as existing in the neighbor’s countries like India and Pakistan regarding the epidemiology, risk factors, pattern of disease, virus linage distribution and future control and eradication targets. Proper epidemiological studies are needed to be conducted in near future linked with neighbor’s countries to control and eradicate the roots of PPR from the region.
Nepal: PPR is epidemic disease of small ruminants which has caused significant economic losses in Nepal (Acharya et al., 2018). In Nepal, first outbreak of PPR was reported in 1995 (Banyard et al., 2010; Dhar et al., 2002) from the Dhanusha, Mahottari, Bara, Sarlahi, Rauthat and Gorkha districts (Jha et al., 2013) and about 68 districts of Nepal have reported the PPR outbreaks covering all eco-zones and developmental regions (DoAH, 2015). A study done by Regional Agricultural Research Station (Goats), Bandipur under the National Agriculture Research Council in Syangja and one other district has reported PPR as the major infectious disease of goats and recorded 33.48% mortality, investigative efforts were made to determine sero-prevalence of PPR in unvaccinated goat population of Syangja and Kaski districts and associated risk factors (Khakural, 2003). The PPR virus circulating in different countries of Asia i.e. Nepal, India, Bhutan, China, Iran, Iraq, Israel, Kuwait, Bangladesh, Pakistan, Saudi Arabia, Tajikistan, Turkey is of lineage (IV) (Parida et al., 2015) however, the F and N gene sequencing based study has shown that the virus found in Nepal, India and Bangladesh is more closely related than virus found in rest of the countries (Dhar et al., 2002). According to Acharya et al. (2018), Eco zone wise distribution of PPR showed that the PPR outbreaks were reported the highest in mountain followed by hills and the lowest in Terai. The highest outbreaks in mountain may be due to excessive movements of nomadic herd of sheep and goat, common pasture, low vaccine coverage in mountain whilst in hill region due to geographic difficulty and low sero-conversion of vaccine. Hence, strategic vaccination campaigns, proper biosecurity, movement control, risk analysis and early diagnosis need to be implemented for the control of PPR in the country and also do the same strategies for the region. The above studies justify the regional links of virus transmission, temporal and spatial pattern of disease distribution in the region, virus lineage distribution and other complex phenomenon of the virus regionally.