ORIGINAL RESEARCH
published: 28 February 2022
doi: 10.3389/fitd.2022.792857
Sero-Prevalence of West Nile Virus
in Urban and Peri-Urban Poultry
Farms of Guwahati, India
Archana Talukdar 1, Razibuddin A. Hazarika 1, Durlav P. Bora 2, Seema R. Pegu 3,
Phunu Talukdar 1, Nur A. Kader 1, Sidharth S. Mohakud 1, Naba Jyoti Deka 3
and Johanna F. Lindahl 4,5,6*
1
Department of Veterinary Public Health, College of Veterinary Science, Assam Agricultural University, Guwahati, India,
Department of Veterinary Microbiology, College of Veterinary Science, Assam Agricultural University, Guwahati, India,
3 Animal Health Division, National Research Centre on Pig, Guwahati, India, 4 Department of Clinical Sciences, Division of
Reproduction, Swedish University of Agricultural Sciences, Uppsala, Sweden, 5 Department of Biosciences, International
Livestock Research Institute, Nairobi, Kenya, 6 Department of Medical Biochemistry and Microbiology, Uppsala University,
Uppsala, Sweden
2
Edited by:
Wilmer Villamil Gómez,
University of Sucre, Colombia
Reviewed by:
Shih Keng Loong,
University of Malaya, Malaysia
Jody Hobson-Peters,
The University of Queensland,
Australia
*Correspondence:
Johanna F. Lindahl
j.lindahl@cgiar.org
Specialty section:
This article was submitted to
Emerging Tropical Diseases,
a section of the journal
Frontiers in Tropical Diseases
Received: 11 October 2021
Accepted: 20 January 2022
Published: 28 February 2022
Citation:
Talukdar A, Hazarika RA, Bora DP,
Pegu SR, Talukdar P, Kader NA,
Mohakud SS, Deka NJ and Lindahl JF
(2022) Sero-Prevalence of West Nile
Virus in Urban and Peri-Urban Poultry
Farms of Guwahati, India.
Front. Trop. Dis. 3:792857.
doi: 10.3389/fitd.2022.792857
West Nile virus (WNV) is a zoonotic, emerging mosquito-borne virus which can cause
severe disease in the form of encephalitis and acute flaccid paralysis in humans. In Assam,
northeast India, arboviruses seem to be re-emerging, however, WNV has been little
studied. The present investigation was carried out from April, 2018 to March, 2019 to
study sero-positivity of WNV in chicken in urban and peri-urban areas of Guwahati, the
capital city of Assam. Four urban and four peri-urban areas of Guwahati were selected. A
total of 864 chicken serum samples (72 samples per month) were screened by ELISA and
further confirmed by haemagglutination inhibition (HI), which revealed that 3.13% of the
chickens had been exposed to WNV, with 0.69% sero-positivity in urban areas compared
to 5.56% in peri-urban. Peak sero-prevalence of WNV were reported during the month of
July and August with 8.33% each with lowest sero-prevalence being recorded in
November (1.39%) and no sero-positive birds from December to April. These results
indicate that WNV is one of the actively circulating flaviviruses in Assam, and human febrile
and encephalitic cases should be screened for the disease.
Keywords: vector-borne disease (VBD), zoonoses, emerging infectious diseases, Flavivirus, arboviruses,
South Asia
INTRODUCTION
West Nile virus (WNV) is an arthropod-borne virus of the genus Flavivirus and belongs to the
Japanese encephalitis virus (JEV) antigenic complex under family Flaviviridae (1). Since the first
isolation of WNV in 1937 in the West Nile district of Uganda from a febrile woman (2), the virus
has been spreading and is considered an emerging zoonosis (3). WNV can cause encephalitis in
severe cases and a few patients develop acute flaccid paralysis (4, 5). Although WNV is transmitted
in a cycle involving different birds and mosquitoes (6), domestic birds are unlikely to play a major
role in the virus transmission as they usually do not develop sufficient viraemia (7, 8). However,
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Urban WNV in Poultry, India
rainfall, rice fields, animal reservoirs and diverse mosquito
species makes Assam the most vulnerable state for spread of
vector-borne diseases. Circulation of highly pathogenic neuroinvasive WNV has also been reported from this part of the
country (12), and it is therefore urgent to identify ways to protect
the Assamese population, using a one-health approach (19).
Considering the above facts, the present study was conducted
to better understand WNV epidemiology and to map serological
evidence of WNV infection in poultry in urban and peri-urban
areas of Guwahati.
seroconversion in poultry in any geographical region indicates
the existence of the virus and also the consequent threat to
human population, and therefore poultry can be used as sentinel
for disease surveillance (9).
Assam is a state in North-eastern India, situated south of the
eastern Himalayas along the Brahmaputra and Barak River
valleys, covering an area of 78,438 km2. To its north lies
Bhutan and Arunachal Pradesh with Nagaland and Manipur to
the East; Meghalaya, Tripura, Mizoram and Bangladesh to the
South and West Bengal to the West. The state extends from 89°
42′E to 96°E longitude and 24°8′ N to 28°2′ N latitude. It is the
most populated state with about 50% of the 38.8 million
inhabitants of Northeast India (10). Recognition of WNV as
the causative agent of acute encephalitis syndrome in Assam was
first confirmed in 2006, and the study by Khan et al. (10) was the
first report of this flavivirus from eastern parts of India. Although
JEV has been reported to cause epidemics in Assam since 1976,
studies have shown that only 53.7% of persons with acute
encephalitis syndrome (AES) were infected with this virus and
most cases remain undiagnosed (11). Since many patients with
symptoms of neurotropic viral infection are JEV negative, there
is likely circulation of some other virus, which might be WNV, as
signs and symptoms produced by JEV and WNV are similar, but
little is known about WNV circulation in the state, although the
virus has been confirmed in some cases of AES (12).
In Assam, a total of 52 mosquito species under 11 genera have
been detected, the most predominant being Anopheles followed
by Culex, Aedes, Mansonia, Armigeres, Mimomyia,
Ochlerostatus, Malaya, Toxorhynchites, Ficalbia and Aedeomyia
(13). Mosquitoes belonging to Ma. uniformis and Cx. vishnui
group comprising of Cx. tritaeniorhynchus, Cx. vishnui and Cx.
pseudovishnui were reported to be highly abundant, breeding
predominantly in paddy fields (14).
Assam is a state with many national reserves and wetlands, and
hence a diverse avifauna (15), but in addition to all wild birds,
poultry is also very common, and there has been substantial
development of poultry farming in India (16). Agriculture and
allied activities play a major role in the economy and the farmers are
considered to be the backbone of agriculture in Assam. Poultry has
become a vital component of the farm economy as it generates
additional income and employment in the rural area (17). Poultry
rearing is traditionally popular in this state, especially in rural and
tribal areas for meat and egg production and poultry is the primary
source of animal protein and supplementary income for the
rural people.
In Assam, WNV has been detected by reverse transcriptasePCR in Cx. vishnui, Cx. whitmorei, Cx. tritaeniorhynchus, Cx.
quinquefasciatus, Cx. pseudovishnui and Mansonia uniformis,
and the viruses detected were found to be WNV lineage 5, and
99-100% similar to a WNV strain earlier found in a human
sample in Assam (18).WNV has been identified from various
regions of Assam to which JEV is endemic indicating that WNV
might be a substantial contributor to the acute encephalitis
syndrome (AES) cases in this region.
Rice is the main crop of Assam and occupies about two-thirds
of the total cultivated area of the state. However, abundance of
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METHODS
This repeated cross-sectional study was conducted from April,
2018 to March, 2019.
Selection of Study Area and Location of
Poultry Farms
Based on a pilot survey and retrospective data on the availability
of poultry in urban and peri-urban farms of Guwahati, the area
of study was identified. Urban farms were defined as within the
official city boundaries and peri-urban as within 10 km of the
official city boundaries of Guwahati, the capital city of Assam
(20). All villages in that circle were mapped and poultry farms
identified. Thereafter, four locations each from urban
(Chandmari, Hatigaon, Noonmati and Khanapara) and periurban (Jugukuchi, Kamalajari, Garal and Gadebari) areas of the
city were purposely selected as representing different parts of the
city. From each study locations, three farms were selected
randomly encompassing in total 24 farms. Coordinates of
farms were recorded using GPS tools (Figure 1). A suitable
questionnaire was prepared for collecting baseline information
from urban and peri-urban poultry farmers of Guwahati which
was validated for its legitimacy and consistency. Consent was
obtained from the farmers before collection of information.
Serum Sample Collection
The farms were visited every month for a period of 1 year (April,
2018, to March, 2019), and at each visit, three birds were
randomly selected from each of the 24 farms, comprising of 72
serum samples per month. Sample size was decided after budget
considerations and discussions with farmers on how many birds
they would allow to have sampled. The farmers consented to the
blood collection procedure of the chickens and from each bird, 2
ml of whole blood was collected using sterilized disposable
syringes. The blood samples were transferred to a vacutainer
and left to clot at room temperature. The samples collected were
then brought to laboratory in sample carrier box using ice packs.
The serum samples separated from the clot were then stored at
-20°C until analysis.
Serological Analyses
Serum samples were screened for WNV antibodies using a
c om m er c i a l l y a va il a b l e c o m p e ti t iv e e n z ym e- li n k e d
immunosorbent assay (ELISA) kit (7) (ID Screen® West Nile
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Talukdar et al.
Urban WNV in Poultry, India
FIGURE 1 | Locations of sampled urban and peri-urban poultry farms of Guwahati, together with population density (people/square km) and serological status of
the farms (positive or negative).
for 10 min. The supernatant obtained was thus made ready to
carry out HI test (1/10 dilution).
West Nile virus reference strain WN_0304 (Israel 2000) was
used as antigen and prepared by diluting virus culture stored on
Whatman® FTA® Classic cards with a borate saline solution
with 0.4% bovine albumin (BABS). The antigen was tested for its
haemagglutinating activity before performing the HI test. The
highest dilution of the virus causing haemagglutination was
taken as 1 HA unit. Four times more concentrated 1 HA unit
virus was considered as 4 HA unit.
Serial two-fold dilution of the test serum samples was made
with BABS in the microtitre plate. An equal volume of known
viral antigen using 4 HA unit was added to each of the serum
containing wells. The plates were shaken gently and kept at room
temperature for 1 h. To all the wells double the volume of the
washed RBC solution was added. The plates were then shaken
gently and incubated at 37°C for 1 h. In each of the test, serum
control containing BABS and diluted antigen; and RBC control
containing BABS and RBC were kept.
Competition, IDVet, Grabels, France) following the
manufacturer’s instructions, which allows species-independent
recognition of WNV antibodies against the Pr-E envelope
protein. However, flavivirus ELISA are prone to cross-reaction
with other flaviviruses (21–24), and the results of the ELISA can
thus only be interpreted as having antibodies against a flavivirus.
The most specific test to identify WNV antibodies is through
virus neutralization tests (VNT) (21, 25), but this method is less
sensitive and requires high biosafety level of laboratories which is
why ELISA is more commonly used (26).
Since VNT was not possible in the lab, the ELISA positive
samples in this study were confirmed for WNV specific
antibodies using haemagglutination inhibition (HI) test as
recommended by OIE (27) and as per the method described
previously (28, 29).
Acetone extraction of the serum was carried out to remove
non-specific HA inhibitors. Cold acetone (2.5 ml) was added to
serum (50 µl) samples in test tubes which were then capped with
rubber stoppers. The solution was mixed well and extracted for 5
min in an ice-bath. Centrifugation was carried out at 1500×g for
5 min at 4°C and thereafter, the supernatant was decanted. The
sediments thus obtained were spread inside tubes and vacuum
dried at room temperature for 1 hour. Borate saline (pH 9.0; 500
µl) was added to each tube, capped with a rubber stopper, and
sediments were allowed to dissolve overnight at 4°C to make 1/10
dilution of the sera.
To each of the acetone extracted sera, 1/50 volume of packed
goose red blood cells (RBC) were added and adsorbed for 20
minutes in an ice bath. Then centrifugation was done at 800×g
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Data Analyses
Data were entered into MS Excel and statistical comparisons
conducted by STATA 14.2 (STATAcorp Ltd, College Station,
Texas) using Exact Fisher’s test. Other studies have also found
higher sensitivity of ELISA (97.9%) compared to HI (87.5%),
while the specificity of ELISA and HI have been reported as
95.7% and 100%, respectively (30). Due to the higher specificity,
HI results are used for the descriptive statistics. Coordinates were
entered into Google Earth Pro to understand how densely
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Talukdar et al.
Urban WNV in Poultry, India
poultry farms and multiple in-contact of other animals with
chickens were recorded from both urban and peri-urban farms.
Out of 864 samples, 36 were positive for antibodies against
WNV by ELISA (4.2%, 95% confidence interval (CI) 2.9-5.7%).
Further confirmation of these 36 ELISA positive samples by HI
revealed 27 to be positive for WNV with an overall apparent
prevalence of 3.1% (95% CI 2.07-4.5%) (Table 3). Location-wise
sero-prevalence of WNV in chicken was recorded to be 0.9% and
0.7% in urban areas and 7.4% and 5.6% in peri-urban areas, as
evidenced by ELISA and HI, respectively, which was
comparatively higher in peri-urban than urban areas of
Guwahati. Half of the peri-urban farms (50%) had at least one
positive bird, compared to one (8.3%) of the urban farms
(p=0.07). The sero-prevalence was recorded from Hatigaon in
urban Guwahati and three peri-urban locations namely,
Jugukuchi, Kamalajari and Garal. Location-wise, highest WNV
sero-prevalence was recorded in Jugukuchi (11.1%), followed by
Kamalajari (8.3%) with lowest in Hatigaon and Garal, showing
2.8% sero-positivity each. No WNV sero-positivity in chicken
was found in the other sites (Figures 1 and 2).
WNV antibodies were detected in one poultry farm of urban
Guwahati compared to six sero-positive farms belonging to periurban areas (Figure 1). Through mapping of the farm
coordinates, it was possible to see that positive farms were
both in densely populated as well as in more peri-urban
locations. More farms with seropositive birds were observed
among those that kept pigs (2/3, 66.7% (the negative farm had
only one pig)) compared to farms not keeping pigs (5/21, 23.8%),
and the same was observed for farms keeping any kind of
livestock apart from poultry (4/8, 50%) compared to farms
with only poultry (3/16, 18.8%), but the difference was not
significant (p>0.1). None of the small farms with indigenous
poultry had any seropositive birds.
Maximum sero-positivity of WNV was reported in July and
August, 2018 with 8.3% prevalence each. Lowest sero-positivity
was recorded in November (1.4%) and no positive birds were
recorded from December to April (Figure 3). Out of a total of 27
WNV sero-positive samples, three were from urban farms, one
each in the months of July, August and September 2018. The
remaining 24 sero-positive samples from May to November 2018
were from peri-urban farms.
Most seroconversions were observed in monsoon (7.3%),
followed by post-monsoon (2.8%) and pre-monsoon (0.9%)
with no sero-positive birds detected in winter season (Table 4).
All the sero-positive samples in urban areas of Guwahati were
recorded during monsoon season.
populated the area was where chickens were found positive. Four
climatological seasons (pre-monsoon, monsoon, post-monsoon
and winter) were defined as by India Meteorological
Department, Ministry of Earth Sciences, Government of India.
RESULTS
Based on the questionnaire data, it was found that the purpose of
rearing chicken in the present study was mainly for earning
livelihood by selling the birds, while only a small number of
farmers reared the birds for home consumption and
egg production.
In the present study, 25% of the total farms were under
integrated production system and all of these belonged to periurban areas. In integrated systems the farmers only invest by
providing the sheds, equipment and the existing land and the
integrator provides all other requisites including day-old chick,
feed, litter (bedding), medications, vaccines, technical support
etc. for raising the birds. No farm had an abattoir and the farmers
sold the birds directly in the market, or the birds were collected
by the company in case of integrated farms. The farmers and
their families were all living in the same compound at walking
distance from the poultry house.
Out of the 24 visited farms, four had indigenous, which means
local breeds or non-descript birds, with between 5 and 11 birds per
farm. The other 20 farms kept broilers, and reported keeping
between 200 and 100,000 birds (Table 1). Farmers in the periurban areas of Guwahati reared comparatively more birds than the
urban farmers. In the present study, 75.0% of peri-urban farms had
more than 1000 birds followed by 16.7% farms with 101-500 birds.
In contrast to peri-urban farms, 58.3% of urban farms had 101-500
birds followed by 33.3% farms with less than 100 birds. Most farms
were deemed to have moderately clean shed (15/24 farms, defined
as: Bedding dry or little bit damp. Feeders and water sources may
have some contamination), and similarly most farms had
moderately clean birds (16/24 farms, defined as: Majority of birds
having plumage color more towards brownish or dusty).
The poultry farmers of urban and peri-urban Guwahati also
reared cow, pig, goat, duck, quail, pigeon, and fishes (Table 2).
Out of the 24 farms, 66.7% farms were found to have at least one
other animal species. Household of eight farms, five in urban and
three in peri-urban areas, were only kept poultry. Other animals
in contact with chickens were recorded to be comparatively
higher in peri-urban (55.6%) than urban (44.4%) poultry farms
of Guwahati. Presences of pigs were recorded only in peri-urban
TABLE 1 | Number of chickens reared by urban and peri-urban poultry farmers.
Location of poultry farms
Urban
Peri-urban
Total
Number of chickens reared by the poultry farmers
Total farms
Less than 100
101 to 500
501 to 1000
More than 1000
4 (33.3%)
0
4 (16.7%)
7 (58.3%)
2 (16.7%)
9 (37.5%)
0
1 (8.3%)
1 (4.2%)
1 (8.3%)
9 (75.0%)
10 (41.7%)
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12
12
24
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Urban WNV in Poultry, India
TABLE 2 | Other animals kept by urban and peri-urban poultry farms.
Animal species
Location of poultry farms
Cow
Dog
Pig
Cow+ pigeon
Dog+ duck
Indigenous chicken+ cow
Indigenous chicken+ goat
Indigenous chicken+ quail
Indigenous chicken+ cow+ dog
Pig+ cow+ duck+ pigeon
Indigenous chicken+ cow+ dog+ cat
Indigenous chicken+ duck+ dog
Indigenous chicken+ cow+ pig+ goat+ dog+ fish
No other animal/bird/fish
Total farms
Total
Urban
Peri-urban
0
3 (25.0%)
0
0
1 (8.3%)
1 (8.3%)
1 (8.3%)
1 (8.3%)
0
0
0
1 (8.3%)
0
4 (33.3%)
12
1 (8.3%)
2 (16.7%)
1 (8.3%)
1 (8.3%)
0
0
1 (8.3%)
0
1 (8.3%)
1 (8.3%)
1 (8.3%)
0
1 (8.3%)
2 (16.7%)
12
1
5
1
1
1
1
2
1
1
1
1
1
1
6
24
Higher (29.40%) as well as lower (0.60-1.70%) WNV seropositivity in domestic birds has been reported in other countries
(7, 32). Domestic chickens do not usually show clinical signs of
WNV, and therefore they are the most commonly used avian
model for the study of immune responses to WNV infection.
However, abnormal death and paralysis of domestic chickens has
been found associated with sero-positivity against WNV (32).
There is expected variation in WNV sero-prevalence over the
year, as the WNV epidemiology is determined by both abiotic
and biotic factors, including climate (33–35). In this study, the
sero-prevalence were higher during the months with high
average monthly temperature and precipitation. Higher
environmental temperature increases the ability of Culex
mosquitoes to transmit WNV (36, 37), and in addition, higher
temperatures facilities faster larval development and this was also
shown in an earlier study in Assam, which found a peak of the
relative mosquito abundance during monsoon and least
mosquitoes during winter (38).
Sero-prevalence may also depend on managemental and
husbandry practices as well as genetic variation in disease
resistance (39). Under poor housing and sanitary conditions,
vectors proliferate in dirty water, filthy environment, thereby,
having their highest impact on the underprivileged section of the
society (40), making them especially vulnerable. Vector densities
have been reported to be higher in rural areas compared to urban
localities due to more favorable habitats for some mosquito
species (41), which is similar to our finding of more common
seroconversions in peri-urban compared to urban areas.
In the present study, the most common disease symptoms in
the poultry farmers or their house-hold members were reported
to be fever (75.0%) followed by flu-like symptoms (70.8%),
headache (66.7%), fatigue (50.0%), off-fed (29.2%), myalgia
(25.0%), arthralgia (25.0%), nausea (16.7%) and vomiting
(12.5%). No farmers reported drowsiness, neurological
symptoms or motor dysfunction. Peri-urban farmers (41.7%)
suffered more than urban farmers (8.3%) from myalgia (p=0.06).
The only symptom with an association with serological status of
the farm was myalgia (p=0.02), where 4/7 (7.1%) seropositive
farms reported myalgia, while this was only reported by 2/17
(11.8%) seronegative farms.
DISCUSSION
This study demonstrates that poultry in Assam, India, are
exposed to WNV and that exposure is more common in periurban areas, and around the monsoon season. The higher
positivity (4.17%) found in our study by ELISA compared to
HI (3.13%) is likely due mainly to higher sensitivity, but could
also be indicative of lower specificity, and more cross-reactions,
maybe with JEV. Flaviviruses are prone to serological crossreactions (31), and it may be difficult to conclude which virus an
animal has been exposed to by only using one serological
method, particularly in an area with more than one flavivirus
circulating, like Assam.
TABLE 3 | Sero-prevalence of West Nile virus in urban and peri-urban poultry farms by enzyme-linked immunosorbent assay (ELISA) and haemagglutination inhibition
(HI).
Location
Serum samples tested
Urban
Peri-urban
Total
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Number of positive samples (%)
432
432
864
5
ELISA
HI
4 (0.93)
32 (7.41)
36 (4.17)
3 (0.69)
24 (5.56)
27 (3.13)
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Urban WNV in Poultry, India
FIGURE 2 | Accumulated sero-prevalence of West Nile virus in chicken samples over one year in different parts of Guwahati, Assam, India.
in urban areas, combining farming with private job was also
another option for urban farmers which was non-existent in
peri-urban areas of Guwahati. Agriculture plays an important
role in the Indian economy and 70% of its rural households still
depend primarily on agriculture for their livelihood, comprising
of 82% of small and marginal farmers (51). All the poultry
farmers during the present study were found to be either small or
marginal and most of them were engaged in agriculture and
allied sectors corroborating the above statement.
The noticeable difference in the number of birds reared in
urban and peri-urban farms might be due to more conveniences
of farming in peri-urban areas because of larger land holding by
farmers, joint families extending help in farming, involvement of
more household members in farm activities, availability of
agricultural produce which can be used as feed stuffs,
proximity to wholesale markets, less availability of other
sources of livelihood as well as pro-activeness of different
companies expanding integrated system of broiler production
by involving the peri-urban farmers which was evident from the
present study. Mixed farming is a commonly adopted farming
practice in India involving combination of crop production with
one or more type of animal species like rearing of cattle, sheep,
goat, pigs and poultry as well as fishery, beekeeping, sericulture,
etc. (52).
The limitations of this study include the lack of confirmation
with VNT, as well as the relatively low number of birds sampled
each month per farm. Given the known cross-reactions between
different flaviviruses, particularly JEV and WNV, and the fact
that the ELISA kit used cannot differentiate these viruses (23, 53),
it is possible that some of these sero-conversions could be against
Similarly, presence of potential factors facilitating vector-borne
and zoonotic diseases such as the way of living (42), socioeconomic status of the people (43), livestock dependence (44),
cultural aspects of community (45), drainage system (46), may
also contribute to higher sero-prevalence of WNV in periurban areas.
In disease epidemiology, GIS and Global Positioning System
(GPS) helps in envisioning topographical distribution of disease,
with respect to time and space, which is difficult to perform in
any other system (47). Through mapping of the coordinates of
the positive farms in this study into online tools such as Google
Maps, or Google Earth, it was possible to show that
seroconversions in birds occurred in densely populated as well
as peri-urban areas.
WNV infections are asymptomatic in 80% of infected
humans (48), while most symptomatic persons develop fever,
headache, muscle pain, joint pain, rash, or gastrointestinal
symptoms and very rarely (less than 1%) infected persons
show neurological disorders, including encephalitis, meningitis,
or acute flaccid paralysis (49). However, humans are dead-end
host as there is no danger of WNV transmission from infected
humans because of insufficient viremia to permit virus
transmission through mosquitoes (50). None of the poultry
farmers interviewed in this study reported neurological
symptoms, but fever and headache were commonly reported.
Agriculture along with livestock farming was adopted as a
source of livelihood by majority of the peri-urban farmers in
contrary to the absence of agriculture in urban areas which might
be due to lesser land holding by farmers in urban areas. Due to
presence of numerous job avenues offered by different companies
TABLE 4 | Season-wise sero-prevalence of West Nile virus in chicken in Guwahati, India.
Season
Pre-monsoon
Monsoon
Post-monsoon
Winter
All year
Number of samples collected
Number of positive samples
216
288
144
216
864
2 (0.9%)
21 (7.3%)
4 (2.8%)
0 (0%)
27 (3.1%)
March- May
June-September
October-November
December-February
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FIGURE 3 | Month-wise number of chickens sero-positive to West Nile virus (WNV) out of 72 chicken sampled each month.
JEV instead of WNV. The best method for distinguishing the
causative virus would be VNT, but this would require a biosafety
level 3 laboratory, which was not available. However, the study
shows the use of serological testing of birds to understand the
pattern of flavivirus infections in the city area, thereby indicating
risks for humans.
After completion of the present study, all the farmers under
study were included in an awareness program about mosquitoborne diseases and which precautions that can be done,
including to remove the possible mosquito breeding sites like
stagnant-standing water, empty containers, broken flower pots,
tip over buckets, tyres, etc. The farmers of the sero-positive farms
were informed about the presence of West Nile virus in their
respective areas. The farmers were also advised to seek medical
help if they developed fever, headache, muscle pain, joint pain,
neurological disorder or any other symptoms common to
WNV infection.
In conclusion, this study found circulation of WNV in urban
and peri-urban Guwahati, indicating that this virus may be an
important contributor to the undiagnosed cases of acute
encephalitis that occurs every year. Understanding the
distribution of WNV sero-prevalence in chicken can support
future strategic planning of vector-borne disease control
approaches by identifying the underlying environmental
factors as well as demography of urban and peri-urban farmers
in a city such as Guwahati. For improved understanding of the
risks for WNV as well as other mosquito-borne flaviviruses, it
would be recommended to set up surveillance programmes with
a One Health approach, where sampling in animals can advise
preventive measures in humans.
ETHICS STATEMENT
The animal study was reviewed and approved by Institutional
Animal Ethics Committee, Assam Agricultural University,
Khanapara (Approval Registration No. 770/ac/CPCSEA/FVSc/
AAU/IAEC/17-18/584 dated 09.08.2017).
AUTHOR CONTRIBUTIONS
Conceptualization, RH and JL. Methodology, JL, RH, and AT.
Formal analysis, JL and AT. Investigation, AT, RH, JL, ND, NK,
PT, and SM. Resources, JL. Writing—original draft preparation,
AT, JL, and RH. Writing—review and editing, all authors.
Supervision, JL, RH, SP, and DB. Project administration, RH
and JL. Funding acquisition, RH and JL. All authors have read
and agreed to the published version of the manuscript.
FUNDING
The authors are thankful to Swedish Research Council for
Environment, Agricultural Sciences and Spatial Planning
(Formas, grant number 2016-00364) for funding the research.
The authors are also grateful to Assam Agricultural University,
Khanapara, Guwahati, NRC on Pig, Rani, Guwahati, Assam, the
CGIAR system and Uppsala University, Sweden for the supports
provided during the study.
ACKNOWLEDGMENTS
DATA AVAILABILITY STATEMENT
The authors wish to acknowledge all participating poultry
farmers and all students for their help in the survey, as well as
Stephen Oloo for his help with generating the map.
The raw data supporting the conclusions of this article will be
made available by the authors, without undue reservation.
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Conflict of Interest: The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
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Copyright © 2022 Talukdar, Hazarika, Bora, Pegu, Talukdar, Kader, Mohakud, Deka
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