Newcastle disease as an emerging disease in peacocks of Tharparker , Pakistan

1 Department of Zoology,University of Sargodha,Sargodha, Pakistan 2 Department of Biosciences, COMSATS Institute of Information Technology (CIIT), Park Road, Chakh Shazad, Islamabad, Pakistan 3 Department of Botany,PMAS Arid Agriculture University, Rawalpindi, Pakistan 4 Department of Remote Sensing and GIS, PMAS Arid Agriculture University, Rawalpindi, Pakistan 5 Department of Zoology, PMASArid Agriculture University, Rawalpindi, Pakistan 6 Department of Wildlife and Ecology, University of Veterinary and Animal Sciences (UVAS), Lahore, Pakistan 7 Department of Microbiology, Quaid-i-Azam University, Islamabad, Pakistan 8 Department of Chemistry, School of Science, University of Management and Technology (UMT), Lahore, Pakistan

Dear Editor, Newcastle disease virus (NDV) also known as avian paramyxovirus serotype I (APMV-1) is an RNA virus belonging to the genus Avulavirus (family Paramyxoviridae) [1].NDV strains can be categorized into three major classes: as velogenic (highly virulent) and can cause up to 100% mortality in an unvaccinated flock, mesogenic (intermediate virulence) or lentogenic (nonvirulent) which are used as a vaccine.NDV has an incubation phase of 2-5 days depending upon birds' immune status and age [2].NDV has the ability to infect a wide variety of avian species.More than 200 species of birds have been estimated to be vulnerable to natural or experimental illness through this virus [3].In most species of birds, the younger ones are more susceptible than adults [4].
Newcastle disease (ND) in domestic poultry is the matter of concern all over the world.The NDV is widely spread in Pakistan and frequent outbreaks are being repeatedly reported in wild captive, rural and commercial poultry flocks.Between 2012 and 2013, ND endemic was observed in peacocks in Tharparker desert, Sindh province of Pakistan, where approximately a population of 40,000 peacocks can be found.There is no epidemiological study carried out on NDV epidemic in peacock in Tharparker.The present study was therefore designed to determine the role of epidemiological factors involved in the NDV outbreak.
The study was conducted in different villages of following areas in Tharparker (Sindh), Pakistan including Nagarparker, Islamkot, Kasboo, Naukot, Mithi, Mao and Veera Wah Umarkot.A total number of 2,000 peacocks from eight villages of Tharparker of different age, sex and breed were randomly physically examined between July 2012 and September 2013 to find out the prevalence of disease and its possible causative factors.The epidemiological information was taken in a questionnaire comprising of sex, age, prevalence, feeding, weight, medication, topography and mating behaviour.To determine the statistical association between NDV infection and different parameters Chi-square statistical test was carried out using R 3.1.1for Windows.
The results of current study showed that prevalence of ND in different areas of Tharparker, Sindh, Pakistan during this period was 19.7%.Statistical analysis of different parameters between NDV-infected and non-infected groups of peacocks was carried out.Results showed that year (2012 vs 2013), age (group I [0.5-2 years], group II [2-3.5 years], group III [> 3.5 years]) (Supplementary Data), weight of animals, feeding behaviour (feeding during disease vs non-feeding during disease), mating behaviour (mating vs non-mating), different geographical distribution (different villages) and vaccination status (vaccinated vs non-vaccinated), were significantly associated with NDV infection while gender (male vs female) and habitat topography (stony vs sandy), apparently did not have any impact of NDV infection in Tharparker area (Table 1).The birds of younger age, male, non medicated, sandy area and located in the area of Nagaraparker/Islam Kot/Mithi were more infected in comparison to other factors.
The wide variation in year-wise prevalence of ND might be due to the delay of the monsoon rains in 2012 which caused unavailability of fresh water and increased the risk of disease spreading due to contaminated and infected water.The geographical distribution (village-wise) showed the highest infection in Islam kot, Mithi and Nagarparker.The possible reason might be the lack of good quality conservation practices as well as unavailability of fresh water in the lake due to the delay of monsoon season in these villages.There is a stream of water in Nagarparker which fills only during rainy season: it might be the major reservoir of NDV in the region.The disease sex-wise incidence showed a nonsignificant association which is in accordance with investigations carried out by Zeleke A et al [5].The change in mating behaviour is also positively associated with infection status and a sudden drop in egg production was also observed in animals under the influence of NDV.The vaccination status clearly has an impact on viral infection, in fact animals subjected to vaccination showed lower disease ratio as compared to untreated ones.The possible reason behind the infection of vaccinated peacocks might be represented by climate, because Tharparker has an extremely hot climate thus resulting in heat stress; moreover, the low monsoon rain, such as it was registered during the study period, resulted in a water shortage.Heat stress and water deprivation can lead to steroid production and results in immune suppression reducing the efficacy of the vaccine [6].It is recommended that a thorough implementation of a suitable vaccination plan is carried out which may be reduce the prevalence of ND in the future.This is the first report showing the prevalence of NDV in peacocks in Tharparker region.Research on genetic nature of strains circulating in Pakistan is currently limited and further studies on NDV strains characterization circulation in Pakistan are warranted.

Table 1 .
Different geographical factors in relation to prevalence of Newcastle disease in peacocks, Pakistan