Abstract:
Newcastle disease (ND) outbreaks have been occurring in Iringa backyard chickens and
causing high mortalities leading to severe economic losses to rural households.
The study aimed at ascertain the epidemiological status of Newcastle disease (ND) in
Iringa rural district focusing on determining risk factors of the disease, prevalence of the
disease and genomic characteristics of NDV the etiology of the disease. A total of 250
structured questionnaires were subjected to respondents to assess the knowledge and
practices with regard to ND. The results of questionnaire survey depict that all
respondents (100%) were aware with the disease and 91.2% had experienced the
problem in their backyard chickens. Also 69.6 % of the respondents were aware about
the presence of vaccine against the disease. Most respondents (52.2%) were following
the correct vaccination regime by vaccinating three times a year, while 29.6% of the
respondents were vaccinating their chickens only once and 15.2% reported to have never
vaccinated their chickens. The awareness with disease and proper follow -up of
vaccination regime by the chicken keepers might be the contributing factor to the low
prevalence of the disease. Majority of the respondents (68%) kept chickens only in the
backyards, while 32% of respondents owned other birds such as ducks, pigeons, geese
and quills. About 60% of the respondents reported that their chickens were interacting
with wild birds while 40% of the respondents reported that their chickens were not
interacting with wild birds. Other birds apart from chickens including wild birds act as
reservoir for the disease and maintain the circulation of the virus in backyard chickens. A
total of 321 swabs and 63 tissue samples were randomly collected from backyard
chickens and virus detected by conventional reverse transcription polymerase chain
reaction (RT-PCR). Two chickens out of 384 were found positive for NDV, therefore the
detection rate of disease was 0.01%. The low detection rate could be due to most of the
chickens were the survivors of a preceding outbreak. Partial F-gene sequencing using
cycle dideoxy nucleotide sequencer and phylogenetic analysis using MEGA X software
shows that the circulating NDV strain in the backyard chickens in Iringa belong to
genotype VII and is similar to Mozambican isolates of 2011 and 2012. Moreover, the
isolate belongs to a different genotype with currently used vaccines. This study has
shown that NDV is still a threat in most backyard chickens as it causes massive death of
chickens and therefore mass education is essential in order to reduce the burden. Also,
regular molecular epidemiological studies on the characteristics of the virus will help to
improve vaccine and vaccination measures with regard to existing circulating strains to
end the problem in backyard chickens rearing communities.
