High Seroprevalence of PPRV-Antibodies among Sheep and Goats in Hail, Saudi Arabia

Peste des petits ruminants (PPR) is a highly infectious and often fatal viral disease of sheep, goats and wild small ruminants. The disease is caused by PPR virus (PPRV), classified under genus Morbillivirus in the family Paramyxoviridae (Gibbs and Taylor, 1979; Shaila et al., 1996). Its transmitted by direct contact with infectious animals shedding the virus in both ocular-nasal discharges and in fecal matter (Munir et al., 2013; Albina et al., 2013). After first identification, the virus spread to sub- Saharan Africa, the Middle East, Turkey and the Indian subcontinent. During the last decade, the disease has been reported for the first time in China, Kenya, Uganda, Tanzania, Morocco and Tunisia (Abu Elzein et al., 1990; Banyard et al., 2010). The first report in Saudi Arabia was in 1990 (Abu Elzein et al., 1990), later it was reported in eastern and central region (Housawi et al., 2004; Al-Afaleq et al., 2004; Boshra et al., 2015). We recorded evidence of spreading PPR in smaller population of non-vaccinated sheep and goats in Hail during 2012–2013 (Mahmoud et al., 2016), the present study was proposed to evaluate the status of the disease in larger population during 2011-2016 surveys.

Sera (n=1462) were collected from non-vaccinated sheep (n=683), goats (n=624) and camels (n=155) of all ages and sexes in Hail district, Saudi Arabia (Figure 1) during 2011–2016 surveys and outbreaks investigation (Table 1). Samples were stored at –20ºC until further analysis.

The NP-epitopes based competitive ELISA kit (310 rue Louis Pasteur, 34790 Grabels, FRANCE, http://www.id-vet.com/produit/id-screen-PPR-competition) was used for detection of PPRV-antibodies according to the manufacturer’s protocol (Libeau et al., 1995).

The prevalence of PPR and the associations between variables and seropositivity were estimated. Pearson correlation was performed to assess statistical significance of seroprevalence with discrete variables. Statistical analysis was performed using SPSS-22 (Statistical Package for Social Sciences 22).

Table 1: Cross tabulations of the results* species, year, season and location

Table 2: Significant difference between the prevalence and species, season, year and location

Out of tested sera eight hundred and seventy-six (59.9%) were found positive for PPRV-antibodies, 470 (75.3%) from goats, compared to 406 (59.4%) obtained from sheep. However, all camel samples were seronegative (Figure 2 and 3).

The prevalence of PPR was found to be higher in 2016 (77.3%) compared to 27.9% in 2011 (Figure 4). The positivity was higher in wet moderate season (61.4%) followed by 60.9% in wet cold and 56.7% in dry hot season (Table 1). Species, year and location appeared to be having significant effect (p< 0.01) on the frequency of circulating antibodies in the study (Table 2).

Seroprevalence of antibodies clarifies the status of the PPR especially in non-vaccinated flocks. The present investigation provided data about infection in Hail district in goats, sheep and camels during 2011-2016 where vaccination is not practiced. We reported evidence of spreading PPR in the region in relatively small population (Mahmoud et al., 2016).

The study showed overall prevalence of 59.9%, high sero-prevalence rates in goats (75.3%) and sheep (59.4%), whereas camels were seronegative. Our results further suggest that the incidence was increasing from 27.9% in 2011 onwards to 77.3% in 2016. Species, year and location are significant variables associated with PPRV. Seropositivity was higher in wet seasons (60.9 to 61.4%) to 56.7% in dry hot season. Ameen and Ajayi (2013) reported that clinical conditions of small ruminants was influenced by seasonality, with high percentage of PPR (9.59%) on dry season. Obi (1983) and Okoli (2003) who recorded 25.1% of PPR in dry season. The results obtained varied from previously recorded data (Al-Afaleq et al., 2004; Al-Dubaib, 2009; Boshra et al., 2015), which may be due to seasonal effects, host population density, age, prevailing management practices and the social environment that can influence the contact rates (Abu Elzein et al., 1990; Singh et al., 2004; Bhanuprakash et al., 2006; Bowden et al., 2008). Field and laboratory observations indicate that PPR is less severe in sheep than in goats (Taylor, 1984; Lefèvre and Diallo, 1990). Seronegative camel sera may be related to sample size and/or the circulating virus strain.

Saudi Arabia serves as a major center for international trade, where hundreds of thousands of ruminants are imported every year changing prevalence in a short period of time. Increasing prevalence of PPR in Hail district is alarming and necessitate systematic and intensive serological surveillance programme along with measurement of clinical prevalence, implementing intensive vaccination campaigns and effective control measures/strategies for PPR.

The authors gratefully acknowledge the outstanding staff of the Veterinary Laboratory. Hail, Ministry of Environment, Water and Agriculture, Saudi Arabia

The authors declare that they have no conflict of interest.

Mahmoud, A.Z., M. Abdellatif collected and tested sera, performed statistical analysis and wrote the manuscript. A. Abdalla supervised the study and corrected the manuscript, all read and approved it for submission.