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Retrospective investigation of poultry mortality in Tsirang- a report
Dr. Rinzin Pem
Sr. VO, RLDC Wangdue
I. Background
Given the large number of mortality in eight poultry farms in Gosaling geog and two
farms in Tsholingkhar geog over a period of one week and with all the affected farmers
seeking for free replacement stock from Dzongkhag, RLDC Wangdue was intimated and
hence the need to carry out retrospective disease outbreak investigation in the affected
geogs was felt.
DVH Tsirang investigated and closely monitored the outbreak since day one of its
occurrence. Although various samples and relevant data were collected during the
outbreak period, no definite diagnosis has been made. Owing to this, the retrospective
investigation was mainly aimed to validate their findings and find out the cause and
possible source of the outbreak.
II. Retrospective investigation methodology
1. Review the report on disease outbreak investigation conducted by DVH Tsirang and
information gathered from the DVH Tsirang investigation team.
2. Visit affected poultry farms and interview the farm owners on events related to disease
occurrence.
3. Collect relevant samples for further laboratory analysis.
III. History
DVH Tsirang received reports of increased mortality in young poultry birds in a total of
eight layer farms located at Pemathang and Zomlingzor village in Gosaling geog and
Drupchugang and Lower Tsholingkhar villages of Tsholingkhar geog on 31st May 2014.
The incidences were reported by respective geog livestock in-charges. A team from DVH
immediately visited the affected farms for detail investigation and to institute appropriate
control measures.
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During the investigation, it was found that on 30th
May 2014, the owners of most of the
affected farms reported increased mortality to the geog livestock office. Appropriate
prevention and control measures were taken by the geog officials in both the geogs and
the outbreak incidences was then reported to DVH for further timely intervention.
Control and prevention measures instituted by Geog extension centre and DVH
Tsirang
Isolation of sick and affected birds from apparently normal birds.
Affected and in-contact birds treated with Tetracycline Hydrochloride
powder, Diaveridine and sulfaquinoxaline/ other coccidiostats and also feed
supplements (minerals and vitamins).
Owners were advised to thoroughly clean and disinfect the feeders and
waterers in the affected shed.
The carcasses of dead birds were disposed off following strict zoo sanitary
measures.
Owners were advised to change the litter in the contaminated shed and to
leave it vacant for a minimum of 21 days during which thorough cleaning and
disinfection to be done.
Owners advised to heighten bio security measures in the farms and prevent
further spread.
Affected farms were timely monitoring by Geog extension centre and DVH
Tsirang to control the infection and prevent new cases.
IV. Findings
a. Source of the chicks
The layer day old chicks were sourced from Satara Hatchery, an NPDC
contracted hatchery at Juprey at the rate of Nu. 30 per chick. Most of the farmers
lifted the chicks from the hatchery in hired vehicles.
b. Vaccination status
During the time of investigation, the vaccination status of the affected flock has
been recorded as vaccinated against Marek’s disease (done at the hatchery
immediately after hatching), ND (first dose on day 7) and IBD (new schedule
followed: first dose on day 10)
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c. Details of affected flocks
Sl.
No.
Name of the
poultry farmer
Village Geog Age
group
affected
(days)
Total
stock
Mortality
(number)
Mortality
(%)
1 Dewan Pradhan Pemathang Gosaling 23 1053 500 47.5
2 Diliram Wakhley Pemathang Gosaling 23 1300 500 38.5
3 Tshering Tamang Pemathang Gosaling 23 300 150 50
4 Goma Das Thapa Pemathang Gosaling 28 300 180 60
5 Sonam Yangdon Pemathang Gosaling 28 250 20 8
5 Til Bahadur Nepal Zomlingzor Gosaling 23 318 200 62.9
6 Bola Nath Sutar Zomlingzor Gosaling 38 300 150 50
7 Hatu Chuwan Zomlingzor Gosaling 23 300 190 63.3
8 Sonam Tshering Zomlingzor Gosaling 28 250 230 92
9 Purna Bdr. Subba Drupchugang Tsholingkhar 15 500 52 10.4
10 Santa lal Monger Tsholingkhar
Maed
Tsholingkhar 23 500 200 40
Total 5371 2372 44.2%
d. Temporal pattern of the disease
On interviewing the affected farmers, it was found that the first case and first
death in the geog occurred on 30th
May 2014 with peak mortality on the second
and third day after the first death. The deaths in most of the farms occurred
around the same time and the whole outbreak lasted for 5-6 days. By the end of
first week of June, the outbreak has completely subsided. Except for the total
number of deaths and the verbal accounts of increased deaths on the second and
third day, there is no records of daily mortality rates.
During the period of outbreak, change in weather patterns with cycles of intense
sun and heavy rain was reported in Tsirang. Prior to the outbreak period, there
were no reports of introduction of new birds or equipments in the farms. Some of
the affected farmers claim that in their almost a decade venture into poultry
farming, such a disease with acute intensity wiping off almost half of their flock
was encountered for the first time.
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e. Symptoms (as narrated by owners and investigation team members of DVH
Tsirang)
Depression, off feed, vent soiled with whitish droppings/bloody droppings in
some, ruffled feathers, huddling in one place, and in few, paralysis was also
noticed. (Picture courtesy: Rinzin Dorji, Lab Tech, DVH Tsirang)
Figures showing birds with droopiness, ruffled feathers and huddling
f. Post mortem lesions observed
i. External examination
The carcass was found to be weak and dehydrated, ruffled feathers, vent soiled
with white diarrhoeic faeces and in some with hints of blood.
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Figure showing weak and dehydrated carcasses
ii. Internal examination
Marked haemorrhages in the thigh muscle and in some birds,
haemorrhages were also seen in the pectoral muscles.
Figure showing marked haemorrhages in thigh muscles
Intestines congested in most of the birds with caecal tonsils swollen and
filled with bloody contents.
Bursa swollen and filled with cheesy exudates.
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g. Laboratory samples collected and analysed
Sl.
No.
Type of
samples
No. of
samples
Type of test Laboratory
Findings
Remarks
1 Faecal
droppings
40 Direct/Sedimentation
/Stoll/Floatation
techniques
500-1200 OPG
coccidian oocyst
detected
Conducted at DVH
Tsirang
2 Feed
sample
3 Sample referred to
RLDC Wangdue for
Qualitative Aflatoxin
testing
Weak positive to
aflatoxin
Conducted at RLDC
Wangdue
3 Tracheal/Cl
oacal swabs
30 Rapid Antigen
Detection test against
Avian Influenza
virus
Negative to
Influenza A
Carried out in the
field
4 Organ
Impression
smear
10 Direct Gram
staining/Leishman/G
eimsa staining
No pathogenic
bacteria detected
Conducted at DVH
Tsirang
5 HP samples
(collected
on 30.05.14
& 02.06.14)
2 HP examination Laboratory
results awaited
Sample referred to
NCAH on 22nd
June
2014
6 Serum
samples
(collected
from
remaining
birds in the
flock on
22.06.14)
7 ELISA (antibody
detection)
Laboratory
results awaited
Sample referred to
NCAH on 22nd
June
2014
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Figure showing negative AIV antigen Figure showing mouldy lumps in feed
in the affected birds
h. Similarities between the affected farms
1. The layer DOCs in all the farms were sourced from Satara Hatchery and
transported to Tsirang in hired vehicles separately.
2. No loss of DOCs/birds from the day of lifting from hatchery till the disease
outbreak occurrence.
3. No history of introduction of new birds/equipments/fomites into the farm.
4. The affected bird flocks were of similar age group, with a difference of a week or
two between some flocks.
5. Deep litter system practiced in all farms.
6. Potassium permanganate or Kohrsolin solutions used as foot dip in most of the
farms.
7. Commercial feed (Karma feed) used by all the farms
8. All in all out management system not practiced. Most farms had broiler birds,
adult layer birds in adjoining sheds.
i. Differences between the affected farms
1. No two affected farms were in close proximity despite the occurrence of disease
outbreak at around the same time. In addition, there is no history of introduction
of new birds/equipments/fomites into any of the farms.
2. Level of bio-security differed between the farms. Eg. No proper foot dip tank in
some farms and the frequency of change of solutions variable (mostly done at
owner’s convenience!)
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j. Diagnosis
Based on the salient post mortem lesions, age of the affected flock (3-5 weeks), acute
and infectious nature of disease spread, mortality pattern, the outbreak has been
provisionally diagnosed as Acute Infectious Bursal Disease Outbreak (IBD).
Concurrent infestations with coccidia sps with oocysts ranging from 500-1200 OPG
in the affected birds could have further worsened the disease outbreak situation. The
sudden change in weather conditions could have triggered suspected IBD outbreak
and besides the chicks in majority of the farms were nearing their first IBD vaccine
booster dose.
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V. Recommendations
1. Bio-security practices needs to be improved in most of the affected farms to prevent
future disease outbreaks. For their strict compliance, there is an immediate need to
educate the poultry farmers on the bio-security guideline for poultry farms and make it as
a basis for regulation of the poultry farms.
2. Proper record keeping needs to be practiced by the poultry farmers to record all the
happenings in the farm. Due to lack of proper recording, except for the number of total
deaths, no data on the day wise morbidity and mortality could be collected for this
outbreak.
3. Regulatory guidelines for in-country source of live poultry (hatcheries) should be
developed to regulate and ensure good management practices to prevent introduction of
disease pathogen at the source.
4. Since no other source of the infection could be established and as the affected birds
were sourced from the recent IBD outbreak area (Juprey) around 9th
May 2014, there is a
strong assumption given the stable nature of the virus that this outbreak could be the
spillover infection from the April 2014 outbreak in Sarpang. If this is assumptions turn
out to be true, proper SOPs for sourcing/transportation of DOCs/movement control
measures in events of disease outbreak in the locality of hatchery should be adopted to
prevent future inter Dzongkhag spread of poultry infection of similar nature. However, a
thorough study needs to be carried out to see whether the outbreaks at Sarpang and
Tsirang are related.
VI. Limitations
1. Since this investigation is of retrospective nature, there is possibility of recall bias and
misinterpretation of the events that occurred during the outbreak. However, efforts have
been made to capture the true events as best as possible.
2. Since the outbreak had already subsided during the time of visit, the provisional
diagnosis has been reached after assimilating verbal accounts of the farmers, information
obtained from DVH staffs and after reviewing the outbreak investigation report prepared
by DVH Tsirang team.
3. The serum samples were collected from remaining birds in the affected flock on 22nd
of June 2014 and these birds can be either be uninfected or those that have recovered
from the infection.