Temporal and Spatial Epidemiological Analysis of Peste Des Petits Ruminants Outbreaks from the Past 25 Years in Sheep and Goats and Its Control in India

Abstract

This study was aimed to understand the temporal and spatial epidemiology of peste des petits ruminants (PPR) in India using national surveillance data available in the National Animal Diseases Referral Expert System (NADRES) along with its control plan undertaken. On analysis of the outbreaks/cases reports in sheep and goats in NADRES database from 1995 to 2019, it was observed that PPR features among the top ten diseases and stands first among viral diseases, and among reported deaths, PPR accounts for 36% of mortality in sheep and goats. PPR outbreaks occur round the year in all the seasons but are encountered most frequently during the lean period especially, in the winter season (January to February) in different regions/zones. The reported outbreaks have been progressively declined in most of the states in India due to the implementation of a mass vaccination strategic program since 2011. On state-wise analysis, the PPR risk-areas showed wide variations with different levels of endemicity. Andhra Pradesh, West Bengal, and Karnataka were the top three outbreaks reported states during 1995-2010, whereas Jharkhand and West Bengal states reported more outbreaks during 2011-2015 and 2016-2019 periods. The temporal and spatial distribution of PPR in India provides valuable information on the hotspot areas/zones to take appropriate policy decisions towards its prevention and control in different regions/zones of India. The study also identifies when and where intensive surveillance and vaccination along with biosecurity measures need to be implemented for the control and eradication of the disease from India in consonance with the PPR Global Control and Eradication Strategy.

Keywords: 1995–2019; India; PPR; control; endemicity; epidemiology; risk zones; temporal-spatial analysis.

Figure 1

Shows different agro-climatic zones of India. 1.Western Himalayan 2. Eastern Himalayan 3. Lower Gangetic Plains 4. Middle Gangetic Plains 5. Upper Gangetic Plains 6. Trans Gangetic Plains 7. Eastern Plateau & Hills 8. Central Plateau & Hills 9. Western Plateau & Hills 10. Southern Plateau & Hills 11. East Coast Plains & Hills 12. West Coast Plains & Hills 13. Gujarat Plans and Hills 14. Western Dry Region and 15. Islands.

Figure 2

Analysis of cumulative PPR reports in different periods (1995–2019). (A). Zone-wise (B). Species-wise. Relative percentages of the cumulative outbreaks, cases, and deaths in sheep and goats in different zones of the country during the different analyzed periods. The highest proportion of reported outbreaks and deaths was observed in the South and East zone, respectively.

Figure 3

Dispersion analysis of the cumulative PPR reports in India (1995–2019). (A). State/Zone-wise (B). Species-wise. The mean cases per outbreak with the measure of the variation was calculated. C-Central zone; E-East zone; N- North Zone; NE-North-East Zone; S-South Zone; W-West zone. The highest mean cases per outbreak were observed in Gujarat, followed by Himachal Pradesh, Rajasthan, with the highest in sheep and goats in the West and North zone, respectively.

Figure 4

State-wise proportion of the cumulative PPR reports in India (1995–2019) with the population. (A). Outbreaks (B). Cases. Himachal Pradesh, West Bengal, and Odisha were the top three states reporting the highest number of cases per 100 thousand population during 1995–2010, whereas Tripura & Kerala and Jharkhand & Haryana states were highest during 2011-15 and 2016–2019 periods, respectively.

Figure 5

Year-wise trend analysis of cumulative PPR reports in India (1995–2019). (A). Outbreaks (B). Cases. A gradual increase in outbreaks and cases since 1995 and the highest numbers between 2000 and 2007, with a declining trend from 2005 was observed.

Figure 6

The state-wise occurrence of cumulative PPR reports in India (1995–2019). (A). Outbreaks (B). Cases. C-Central zone; E-East zone; N- North Zone; NE-North-East Zone; S-South Zone; W-West zone. Karnataka and Andhra Pradesh have shown a decline in the number of outbreaks during 2011-FS115 and 2016-19 with sporadic outbreaks in 2018 and 2019; West Bengal and Jharkhand states have reported the highest outbreaks during 2011–2015 and 2016–2019 periods, respectively.

Figure 7

Month-wise analysis of cumulative PPR outbreaks in different zones in India (1995–2019). The outbreaks were predominantly observed between December to April in the South zone, during October & November in the East zone; April & May months in the Central zone; in June in the North-East zone; from January to March in the Western zone and between November and January in the North Zone.

Figure 8

Species-wise occurrence of cumulative PPR reports in different zones/regions of India (1995–2019). (A). Outbreaks (B). Cases. An increased number of outbreaks have been reported in goats than in sheep in the different zones of the country, except in the south zone where the number of outbreaks was greater in sheep.

Figure 9

Endemic districts of PPR in different states of India (1995–2019). The endemicity categorization is based on the scale of the cumulative outbreaks, that occurred in the districts per year in the given period of analysis and classified as in the categories of risk, if the outbreaks numbers in the district as 0 –no risk, 1- very low, 2- low, 3- medium, 4- high and >4 very high-risk districts depicted in the map. Andhra Pradesh, West Bengal, and Karnataka states were the top three states during 1995–2010, whereas during 2011-15 and 2016–2019, Jharkhand and West Bengal states had reported more PPR outbreaks. The current status of PPR outbreaks during 2019 in different districts of India was depicted separately in the map.

Figure 10

Zone-wise trend of outbreaks reports in the states from the financial year 2011-12 to 2019–2020; outbreak reports versus the doses of vaccines used (in thousand) in the strategic immunizations during the preceding years against the population are depicted. (A). North (B). East (C). West (D). South (E). Central (F). North-East zones.

Figure 11

The trend of reduction of outbreaks in the states of Karnataka (A) Andhra Pradesh (B) from the financial year 2003–2004 to 2019–2020; outbreak reports versus the doses of vaccines used (in million) in the strategic immunizations during the preceding years are depicted as the vaccine produces immunity for 3–6 years.

Figure 12

The reported outbreaks in different categories of endemic districts of Karnataka (A) Andhra Pradesh (B) with risk areas are depicted in six scales at different periods of analysis using QGIS-2.18 in the maps of the respective states. The endemicity categorization is based on the scale of the cumulative outbreaks, that occurred in the districts per year in the given period of analysis and classified into different risk level (if the outbreaks numbers in the district as 0–no risk, 1- very low, 2- low, 3- medium, 4- high and >4 very high-risk districts).